Congestive heart failure pathophysiology: Difference between revisions

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'''Associate Editor-In-Chief:''' {{CZ}}; Saleh El Dassouki, M.D [mailto:seldassouki@hotmail.com], Atif Mohammad, MD
{{Congestive heart failure}}
 
{{CMG}}; {{AE}} {{CZ}}; Saleh El Dassouki, M.D [mailto:seldassouki@hotmail.com]; Atif Mohammad, MD


==Overview==
==Overview==
Heart failure is a complex syndrome whereby there is inadequate output of the heart to meet the metabolic demands of the body. Abnormal function of different anatomic parts of the heart cause heart failure including the pericardium, the myocardium, the endocardium, the heart valves and the great vessels. Symptoms of heart failure are due to a lack of both forward blood flow to the body, and backward flow into the lungs.
Heart failure is a complex syndrome whereby there is inadequate output of the heart to meet the metabolic demands of the body. Heart failure is caused by abnormal function of different anatomic parts of the heart including the [[pericardium]], the [[myocardium]], the [[endocardium]], the [[heart valves]] and the great vessels. Heart failure is characterized by decreased [[cardiac output]] but not necessarily decreased [[ejection fraction]]. [[Symptoms]] of heart failure are due to a lack of both forward blood flow to the body, and backward flow into the [[lungs]]. The body tries to compensate for the low [[cardiac output]] by mechanisms that increase the [[preload]] and [[afterload]]. These mechanisms lead to exacerbation of the [[cardiac]] malfunction and symptoms associated with heart failure.


==Underlying Anatomic Abnormalities==
==Pathophysiology==
Heart failure may result from an abnormality or dysfunction of any one of the anatomical structures of the heart:
===Decreased Cardiac Output===
*Heart failure is defined as the inability of the heart to pump enough blood to meet the demands of the body.
* Therefore, heart failure is characterized by a reduced [[stroke volume]] as a result of a failure of [[systole]], [[diastole]] or both:
**'''Systolic heart failure''': Increased [[end systolic volume]] is usually caused by reduced [[contractility]].
**'''Diastolic heart failure''': Decreased [[end diastolic volume]] results from impaired [[ventricular]] filling, as occurs when the compliance of the [[ventricle]] falls (i.e. when the walls stiffen in [[diastolic dysfunction]]).
 
*Heart failure was once thought to be secondary to a depressed [[left ventricular ejection fraction]]. However, studies have shown that approximately 50% of patients who are diagnosed with heart failure have a normal [[ejection fraction]] ([[diastolic dysfunction]]). Patients may be broadly classified as having heart failure with depressed [[left ventricular ejection fraction]] ([[systolic dysfunction]]) or normal/preserved ejection fraction ([[diastolic dysfunction]]). Systolic and diastolic dysfunction commonly occur in conjunction with each other.
 
* Normally, blood flows from the [[lungs]], into the [[pulmonary veins]], into the [[left atrium]], through the [[mitral valve]], and finally into the [[left ventricle]]. When the [[left ventricle]] cannot be normally filled during diastole in both diastolic and systolic heart failure, [[blood]] will back up into the [[left atrium]] and, eventually, into the [[lungs]]. The result is a higher than normal pressure of blood within the [[Blood vessel|vessels]] of the [[lung]]. As a result of [[Hydrostatic pressure|hydrostatic]] forces, this high pressure leads to leaking of fluid (i.e. [[transudate]]) from the [[Lung|lung's]] [[vasculature]] into the air-spaces ([[alveoli]]) of the [[lungs]]. The result is [[pulmonary edema]], a condition characterized by difficulty breathing, inadequate [[oxygenation]] of blood, and, if severe and untreated, death.
 
===Underlying Cardiac Abnormalities Leading to Heart Failure===
Heart failure may result from an abnormality or dysfunction of any one of the anatomical structures of the [[heart]]:
*[[Pericardium]]
*[[Pericardium]]
**It can be damaged by infiltration of [[inflammatory cells]] (e.g. [[pericarditis]]) or fluid ([[pericardial effusion]]).
*[[Myocardium]]
*[[Myocardium]]
**It can be damaged by [[Ischemia|ischemic injury]] (e.g. acute [[MI]]), toxins (e.g. [[chemotherapy]]), infiltration by [[inflammatory cells]] (e.g. [[myocarditis]]), pressure overload (e.g. [[hypertension]] or [[aortic stenosis]]), metabolic derangements, or volume overload ([[aortic insufficiency]] or [[mitral insufficiency]]).
*[[Endocardium]]
*[[Endocardium]]
*[[Valvular heart disease]] or
**It can be damaged by infiltration
*Disorders of the great vessels (e.g. [[pulmonary hypertension]])
*[[Valvular heart disease]]
**[[Valves of the heart|Valves]] can be damaged or dysfunctional from birth ([[bicuspid aortic valve]]) or can be acquired (e.g. [[endocarditis]] or [[rheumatic heart disease]]).
*Disorders of the great vessels
**Great vessels can be stiffened by [[atherosclerosis]] (e.g. [[hypertension]]) or can be chronically constricted (e.g. [[pulmonary hypertension]])


==Mechanism by Which Anatomic Structures are Damaged==
===Systolic versus Diastolic Dysfunction===
*[[Pericardium]]: Can be damaged by infiltration of inflammatory cells (e.g. [[pericarditis]]) or fluid ([[pericardial effusion]]).
====Systolic Dysfunction====
*[[Myocardium]]: Can be damaged by ischemic injury (e.g. acute [[MI]]), toxins (e.g. [[chemotherapy]]), infiltration by inflammatory cells (e.g. [[myocarditis]]), pressure overload (e.g. [[hypertension]] or [[aortic stenosis]]), metabolic derangements, or volume overload ([[aortic insufficiency]] or [[mitral insufficiency]]).
*[[Endocardium]]: Can be damaged by infiltration
*[[Valvular heart disease]]: Can be damaged or dysfuncitonal from birth ([[bicuspid aortic valve]]) or can be acquired (e.g. [[endocarditis]] or [[rheumatic heart disease]]).
*Disorders of the great vessels: Can be stiffened by atherosclerosis (e.g. [[hypertension]]) or can be chronically constricted (e.g. [[pulmonary hypertension]])


==Systolic versus Diastolic Dysfunction==
* Heart failure caused by systolic dysfunction is more readily recognized. It can be simplistically described as failure of the pump function of the heart.
Heart failure was once thought to be secondary to a depressed [[left ventricular ejection fraction]]. However, studies have shown that approximately 50% of patients who are diagnosed with heart failure have a normal ejection fraction ([[diastolic dysfunction]]). Patients may be broadly classified as having heart failure with depressed left ventricular ejection fraction ([[systolic dysfunction]]) or normal/preserved ejection fraction ([[diastolic dysfunction]]). Systolic and diastolic dysfunction commonly occur in conjunction with each other.
* It is characterized by a decreased [[ejection fraction]] (less than 40%-45%). The strength of [[ventricular]] contraction is attenuated and inadequate for creating an adequate [[stroke volume]], resulting in inadequate [[cardiac output]]. In general, this is caused by dysfunction or destruction of [[cardiac myocytes]] or their molecular components.
* In congenital diseases such as [[Duchenne muscular dystrophy]], the molecular structure of individual [[myocytes]] is affected.
* [[Myocytes]] and their components can be damaged by [[inflammation]] (such as in [[myocarditis]]) or by infiltration (such as in [[amyloidosis]]).
* Toxins and pharmacological agents (such as [[ethanol]], [[cocaine]], and [[amphetamines]]) cause [[intracellular]] damage and [[Oxidative stress|oxidative stres]]<nowiki/>s.
* The most common mechanism of damage is [[ischemia]] causing [[infarction]] and [[Myocardial scarring|scar formation]].
* After [[myocardial infarction]], dead [[myocytes]] are replaced by [[scar tissue]], deleteriously affecting the function of the [[myocardium]]. On [[echocardiogram]], this is manifest by abnormal or absent wall motion.
* Because the [[ventricle]] is inadequately emptied, ventricular end-diastolic pressure and volumes increase. This is transmitted to the [[Atrium (heart)|atrium]]. On the left side of the [[heart]], the increased pressure is transmitted to the [[pulmonary vasculature]], and the resultant [[hydrostatic pressure]] favors extravasation of fluid into the [[lung]] parenchyma, causing [[pulmonary edema]]. On the right side of the heart, the increased pressure is transmitted to the [[Venous blood|systemic venous circulation]] and systemic [[Capillary bed|capillary beds]], favoring extravasation of fluid into the tissues of peripheral organs and [[extremities]], resulting in dependent [[peripheral edema]].


===Systolic dysfunction===
;Shown below is an image summarizing the pathophysiology of systolic heart failure.
Heart failure caused by systolic dysfunction is more readily recognized. It can be simplistically described as failure of the pump function of the heart. It is characterized by a decreased ejection fraction (less than 40%-45%). The strength of ventricular contraction is attenuated and inadequate for creating an adequate stroke volume, resulting in inadequate cardiac output. In general, this is caused by dysfunction or destruction of cardiac myocytes or their molecular components. In congenital diseases such as [[Duchenne muscular dystrophy]], the molecular structure of individual myocytes is affected. Myocytes and their components can be damaged by inflammation (such as in [[myocarditis]]) or by infiltration (such as in amyloidosis). Toxins and pharmacological agents (such as [[ethanol]], [[cocaine]], and [[amphetamines]]) cause intracellular damage and oxidative stress. The most common mechanism of damage is ischemia causing infarction and [[Myocardial scarring|scar formation]]. After myocardial infarction, dead myocytes are replaced by scar tissue, deleteriously affecting the function of the myocardium. On echocardiogram, this is manifest by abnormal or absent wall motion.
[[Image:Systolic_Heart_failure.png|center|600px|Systolic heart failure.]]


Because the ventricle is inadequately emptied, ventricular end-diastolic pressure and volumes increase. This is transmitted to the atrium. On the left side of the heart, the increased pressure is transmitted to the pulmonary vasculature, and the resultant hydrostatic pressure favors extravassation of fluid into the lung parenchyma, causing [[pulmonary edema]]. On the right side of the heart, the increased pressure is transmitted to the systemic venous circulation and systemic capillary beds, favoring extravassation of fluid into the tissues of target organs and extremities, resulting in dependent [[peripheral edema]].
====Diastolic Dysfunction====


===Diastolic dysfunction===
* Heart failure caused by [[diastolic dysfunction]] is generally described as the failure of the [[Ventricle (heart)|ventricular]] chambers to adequately relax and results from stiffening of the [[Ventricular|ventricular walls]]. The consequence is reduced filling of chambers of the heart.
Heart failure caused by diastolic dysfunction is generally described as the failure of the ventricle to adequately relax and typically denotes a stiffer ventricular wall. This causes inadequate filling of the ventricle, and therefore results in an inadequate stroke volume. The failure of ventricular relaxation also results in elevated end-diastolic pressures, and the end result is identical to the case of systolic dysfunction (pulmonary edema in left heart failure, peripheral edema in right heart failure.)
* The failure of ventricular relaxation also results in elevated end-diastolic pressures, and the end result is identical to the case of systolic dysfunction (pulmonary edema in left heart failure, peripheral edema in right heart failure.)
* Diastolic dysfunction can be caused by processes similar to those that cause systolic dysfunction, particularly causes that affect cardiac remodeling.
* Diastolic dysfunction typically becomes [[symptomatic]] in physiological conditions under which a high cardiac demand is required. Therefore, patients suffering from diastolic dysfunction are sensitive to increases in [[heart rate]], and sudden bouts of tachycardia (which can be caused simply by physiological responses to [[exertion]], [[fever]], or [[dehydration]], or by pathological [[tachyarrhythmias]] such as [[Atrial fibrillation with rapid ventricular rate|atrial fibrillation with rapid ventricular response]]) which may result in [[flash pulmonary edema]].
* Adequate rate control (usually with a [[Pharmacological|pharmacological agent]] that slows down [[atrioventricular node]] conduction such as a [[calcium channel blocker]] or a [[beta-blocker]]) is therefore key to preventing decompensation.
* Left ventricular diastolic function can be determined through echocardiography by measurement of various parameters such as the [[E/A ratio]] (early-to-atrial left ventricular filling ratio), the E (early left ventricular filling) deceleration time, and the isovolumetric relaxation time.


Diastolic dysfunction can be caused by processes similar to those that cause systolic dysfunction, particularly causes that affect cardiac remodeling.
===Manifestations of Heart Failure===
====Pulmonary Edema====
* The reduction in forward cardiac output leads to a rise in the [[pulmonary capillary wedge pressure]]. [[Rales]] usually develop if the [[pulmonary capillary wedge pressure]] is >25 mm Hg. [[Rales]] may not be present in the patient with chronic heart failure. [[Rales]] may develop at even lower pressures if left [[ventricular]] function deteriorates suddenly.
* [[Dyspnea]] and [[orthopnea]] occur due to [[interstitial edema]] within the [[lungs]] at lower pressures.


Diastolic dysfunction may not manifest itself except in physiologic extremes if systolic function is preserved. The patient may be completely asymptomatic at rest. However, they are exquisitely sensitive to increases in heart rate, and sudden bouts of tachycardia (which can be caused simply by physiological responses to exertion, fever, or dehydration, or by pathological tachyarrhythmias such as [[atrial fibrillation with rapid ventricular response]]) may result in [[flash pulmonary edema]]. Adequate rate control (usually with a pharmacological agent that slows down AV conduction such as a calcium channel blocker or a beta-blocker) is therefore key to preventing decompensation.
====Hypotension====
* Heart failure is characterized by decreased [[cardiac output]] and hence it causes low [[blood pressure]].


Left ventricular diastolic function can be determined through echocardiography by measurement of various parameters such as the [[E/A ratio]] (early-to-atrial left ventricular filling ratio), the E (early left ventricular filling) deceleration time, and the [[isovolumic relaxation time]].
====Hypoperfusion====
The reduction in forward [[cardiac output]] leads to [[hypoperfusion]] at rest which manifests as:
*[[Cool extremities]]
*[[Confusion]] and [[altered mentation]]
*Impaired [[renal]] perfusion and declining [[renal function]] (increased [[blood urea nitrogen]] [<nowiki/>[[Blood urea nitrogen|BUN]]] and [[serum creatinine]] [<nowiki/>[[Creatinine|Cr]]] ; mostly leading to pre-renal failure [BUN:Cr > 20])
* Reduced perfusion of skeletal muscle causes atrophy of the muscle fibres. This can result in weakness, increased fatigue and decreased peak strength, all contributing to exercise intolerance and [[claudication]].<ref>{{GPnotebook|919601204|systemic pathophysiology in heart failure}}</ref>
*In severe heart failure, the effects of decreased cardiac output and poor perfusion become more apparent, and patients will manifest symptoms of systemic hypoperfusion including generalized [[weakness]], [[dizziness]], and [[syncope]].
 
====Impaired Cardiac Reserve====
As the heart works harder to meet normal metabolic demands, the amount cardiac output can increase in times of increased oxygen demand (e.g. exercise) is reduced. This contributes to the exercise intolerance commonly seen in heart failure. This translates to the loss of one's cardiac reserve. The cardiac reserve refers to the ability of the heart to work harder during exercise or strenuous activity. Since the heart has to work harder to meet the normal metabolic demands, it is incapable of meeting the metabolic demands of the body during exercise.
 
===Compensatory Mechanisms and Their Associated Complications===
;Shown below is an image summarizing the compensatory mechanisms of the heart along with their associated complications.
[[Image:Pathophysiology_of_heart_failure.png|center|600px|The compensatory mechanisms in heart failure.]]


== Pathophysiology==
===Abnormality in Contractility===
* In systolic heart failure, there is reduced contractility of the heart and a reduced left ventricular ejection fraction.
* In systolic heart failure, there is a failure of blood to move forward (forward failure) and a tendency of blood to move back ward (backward failure).
* Normally, blood flows from the lungs, into the [[pulmonary veins]], into the [[left atrium]], through the [[mitral valve]], and finally into the [[left ventricle]]. When the [[left ventricle]] cannot be normally filled during diastole in both diastolic and systolic heart failure, blood will back up into the [[left atrium]] and, eventually, into the lungs. The result is a higher than normal pressure of blood within the vessels of the lung. As a result of hydrostatic forces, this high pressure leads to leaking of fluid (i.e. [[transudate]]) from the lung's blood vessels into the air-spaces ([[alveoli]]) of the lungs. The result is [[pulmonary edema]], a condition characterized by difficulty breathing, inadequate [[oxygenation]] of blood, and, if severe and untreated, death.
* A reduced stroke volume, as a result of a failure of [[systole]], [[diastole]] or both. Increased [[end systolic volume]] is usually caused by reduced contractility. Decreased [[end diastolic volume]] results from impaired ventricular filling – as occurs when the compliance of the ventricle falls (i.e. when the walls stiffen in [[diastolic dysfunciton]]).
===Compensatory Mechanisms===
*Left ventricular systolic dysfunction is associated with a reduction in [[stroke volume]], the amount of blood the heart ejects with each heart beat.
*Left ventricular systolic dysfunction is associated with a reduction in [[stroke volume]], the amount of blood the heart ejects with each heart beat.
* The reduction in [[stroke volume]] leads to a reduction in [[cardiac output]] which is the [[stroke volume]] multiplied by the [[heart rate]].
* The reduction in [[stroke volume]] leads to a reduction in [[cardiac output]] which is the [[stroke volume]] multiplied by the [[heart rate]].
* There are two compensatory mechanisms to preserve forward [[cardiac output]] (the product of stroke volume and heart rate):
* There are several mechanisms to preserve forward [[cardiac output]] (the product of stroke volume and heart rate):
#Dilation of the left ventricle to increase the [[stroke volume]] and
#Dilation of the left ventricle to increase the [[stroke volume]] and
#Increase in [[heart rate]]
#Increase in [[heart rate]]
====Dilatation of the Left Ventricle:====
* Dilation of the left ventricle increases volume and increases contractility up to a point (see [[Frank-Starling law of the heart]]).  As further LV dilation occurs, however, contractility drops.  This is due to reduced ability to cross-link [[actin]] and [[myosin]] filaments in over-stretched heart muscle.<ref>''Boron and Boulpaep'' 2005 Medical Physiology Updated Edition p533 ISBN 0-7216-3256-4</ref>.
* Dilation of the left ventricle increases volume and increases contractility up to a point (see [[Frank-Starling law of the heart]]).  As further LV dilation occurs, however, contractility drops.  This is due to reduced ability to cross-link [[actin]] and [[myosin]] filaments in over-stretched heart muscle.<ref>''Boron and Boulpaep'' 2005 Medical Physiology Updated Edition p533 ISBN 0-7216-3256-4</ref>.
* As further dilation occurs, functional [[mitral regurgitation]] ([[MR]]) may develop despite an anatomically normal [[mitral valve]].
* As further dilation occurs, functional [[mitral regurgitation]] ([[MR]]) may develop despite an anatomically normal [[mitral valve]].
* Left ventricular enlargement and lack of forward cardiac output can lead to [[left atrial enlargement]]. [[Left atrial dilation]] may lead to [[atrial fibrillation]] which occurs in 20% of patients with [[congestive heart failure]].  Atrial fibrillation diminishes left ventricular filling through the loss of the [[atrial kick]] (the atrial contraction) and due to an increase in the [[heart rate]] which reduces the time available for the left ventricle to fill.
* Left ventricular enlargement and lack of forward cardiac output can lead to [[left atrial enlargement]]. [[Left atrial dilation]] may lead to [[atrial fibrillation]] which occurs in 20% of patients with [[congestive heart failure]].  Atrial fibrillation diminishes left ventricular filling through the loss of the [[atrial kick]] (the atrial contraction) and due to an increase in the [[heart rate]] which reduces the time available for the left ventricle to fill.
====Hypertrophy of the Myocardium:====
*[[Hypertrophy]]  (an increase in physical size) of the myocardium can develop, which is caused by the terminally differentiated heart muscle fibers increasing in size in an attempt to improve contractility. This may contribute to the increased stiffness and decreased ability to relax during diastole.
====Activation of the Sympathetic Nervous System:====
* Arterial blood pressure falls. This destimulates [[baroreceptors]] in the [[carotid sinus]] and [[aortic arch]] which link to the nucleus tractus solitarius. This center in the brain increases sympathetic activity, releasing catecholamines into the blood stream. Binding to alpha-1 receptors results in systemic arterial [[vasoconstriction]]. This helps restore blood pressure but also increases the total peripheral resistance, increasing the workload of the heart. Binding to beta-1 receptors in the myocardium increases the heart rate and make contractions more forceful, in an attempt to increase cardiac output. This also, however, increases the amount of work the heart has to perform.
* The increased heart rate, stimulated by increased sympathetic activity<ref>{{cite book |author=Rang HP |title=Pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2003 |pages=127 |isbn=0-443-07145-4}}</ref> maintains [[cardiac output]]. Initially, this helps compensate for heart failure by maintaining blood pressure and perfusion, but places further strain on the myocardium, increasing coronary perfusion requirements, which can lead to worsening of ischemic heart disease. Sympathetic activity may also cause potentially fatal [[arrhythmias]].
* The increased heart rate, stimulated by increased sympathetic activity<ref>{{cite book |author=Rang HP |title=Pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2003 |pages=127 |isbn=0-443-07145-4}}</ref> maintains [[cardiac output]]. Initially, this helps compensate for heart failure by maintaining blood pressure and perfusion, but places further strain on the myocardium, increasing coronary perfusion requirements, which can lead to worsening of ischemic heart disease. Sympathetic activity may also cause potentially fatal [[arrhythmias]].
* * [[Hypertrophy]] (an increase in physical size) of the myocardium can develop, which is caused by the terminally differentiated heart muscle fibers increasing in size in an attempt to improve contractility. This may contribute to the increased stiffness and decreased ability to relax during diastole.
===Pulmonary Edema===
* The reduction in forward cardiac output leads to a rise in the [[pulmonary capillary wedge pressure]]. [[Rales]] usually develop if the [[pulmonary capillary wedge pressure]] is >25 mm Hg. [[Rales]] may not be present in the patient with chronic heart failure. [[Rales]] may develop at even lower pressures if LV function deteriorates suddenly.
* [[Dyspnea]] and [[orthopnea]] occur due to interstitial edema within the lungs at lower pressures.
===End Organ Hypoperfusion===
* The reduction in forward cardiac output leads to [[hypoperfusion]] at rest which is suggested by
:*[[Cool extremities]]
:*[[Confusion]] and altered mentation
:*Impaired renal perfusion and declining renal function
===Impaired Cardiac Reserve===
As the heart works harder to meet normal metabolic demands, the amount cardiac output can increase in times of increased oxygen demand (e.g. exercise) is reduced. This contributes to the exercise intolerance commonly seen in heart failure. This translates to the loss of one's cardiac reserve. The cardiac reserve refers to the ability of the heart to work harder during exercise or strenuous activity. Since the heart has to work harder to meet the normal metabolic demands, it is incapable of meeting the metabolic demands of the body during exercise.
===Hypotension===
* Arterial blood pressure falls. This destimulates [[baroreceptors]] in the [[carotid sinus]] and [[aortic arch]] which link to the nucleus tractus solitarius. This center in the brain increases sympathetic activity, releasing catecholamines into the blood stream. Binding to alpha-1 receptors results in systemic arterial [[vasoconstriction]]. This helps restore blood pressure but also increases the total peripheral resistance, increasing the workload of the heart. Binding to beta-1 receptors in the myocardium increases the heart rate and make contractions more forceful, in an attempt to increase cardiac output. This also, however, increases the amount of work the heart has to perform.
===Stimulation of the Renal / Adrenal / Sympathetic Axis===
* Increased sympathetic stimulation also causes the [[hypothalamus]] to secrete [[vasopressin]] (also known as antidiuretic hormone or ADH), which causes free water retention in the kidneys leading to [[hyponatremia]]. This free water retention increases total body blood volume and blood pressure.
* Increased sympathetic stimulation also causes the [[hypothalamus]] to secrete [[vasopressin]] (also known as antidiuretic hormone or ADH), which causes free water retention in the kidneys leading to [[hyponatremia]]. This free water retention increases total body blood volume and blood pressure.
====Stimulation of the Renal / Adrenal / Sympathetic Axis:====
* Reduced [[perfusion]] (blood flow) to the kidneys stimulates the release of [[renin]] – an enzyme which catalyses the production of the potent vasopressor [[angiotensin]]. Angiotensin and its metabolites cause further vasocontriction, and stimulate increased secretion of the steroid [[aldosterone]] from the [[adrenal glands]]. This promotes salt and fluid retention at the kidneys, also increasing the blood volume.
* Reduced [[perfusion]] (blood flow) to the kidneys stimulates the release of [[renin]] – an enzyme which catalyses the production of the potent vasopressor [[angiotensin]]. Angiotensin and its metabolites cause further vasocontriction, and stimulate increased secretion of the steroid [[aldosterone]] from the [[adrenal glands]]. This promotes salt and fluid retention at the kidneys, also increasing the blood volume.
* The chronically high levels of circulating neuroendocrine hormones such as [[catecholamines]], renin, angiotensin, and aldosterone affects the myocardium directly, causing structural remodelling of the heart over the long term. Many of these remodelling effects seem to be mediated by transforming growth factor beta (TGF-beta), which is a common downstream target of the signal transduction cascade initiated by catecholamines<ref>{{cite journal |author=Shigeyama J, Yasumura Y, Sakamoto A, ''et al.'' |title=Increased gene expression of collagen Types I and III is inhibited by beta-receptor blockade in patients with dilated cardiomyopathy |journal=Eur. Heart J. |volume=26 |issue=24 |pages=2698–705 |year=2005 |month=December |pmid=16204268 |doi=10.1093/eurheartj/ehi492 |url=}}</ref> and angiotensin II,<ref>{{cite journal |author=Tsutsui H, Matsushima S, Kinugawa S, ''et al.'' |title=Angiotensin II type 1 receptor blocker attenuates myocardial remodeling and preserves diastolic function in diabetic heart |journal=Hypertens. Res. |volume=30 |issue=5 |pages=439–49 |year=2007 |month=May |pmid=17587756 |doi= 10.1291/hypres.30.439|url=http://joi.jlc.jst.go.jp/JST.JSTAGE/hypres/30.439?from=PubMed |format= &ndash; <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=intitle%3AAngiotensin+II+type+1+receptor+blocker+attenuates+myocardial+remodeling+and+preserves+diastolic+function+in+diabetic+heart&as_publication=Hypertens.+Res.&as_ylo=2007&as_yhi=2007&btnG=Search Scholar search]</sup>}} {{Dead link|date=June 2008}}</ref> and also by epidermal growth factor (EGF), which is a target of the signaling pathway activated by aldosterone<ref>{{cite journal |author=Krug AW, Grossmann C, Schuster C, ''et al.'' |title=Aldosterone stimulates epidermal growth factor receptor expression |journal=J. Biol. Chem. |volume=278 |issue=44 |pages=43060–6 |year=2003 |month=October |pmid=12939263 |doi=10.1074/jbc.M308134200 |url=}}</ref>
* The chronically high levels of circulating neuroendocrine hormones such as [[catecholamines]], renin, angiotensin, and aldosterone affects the myocardium directly, causing structural remodelling of the heart over the long term. Many of these remodelling effects seem to be mediated by transforming growth factor beta (TGF-beta), which is a common downstream target of the signal transduction cascade initiated by catecholamines<ref>{{cite journal |author=Shigeyama J, Yasumura Y, Sakamoto A, ''et al.'' |title=Increased gene expression of collagen Types I and III is inhibited by beta-receptor blockade in patients with dilated cardiomyopathy |journal=Eur. Heart J. |volume=26 |issue=24 |pages=2698–705 |year=2005 |month=December |pmid=16204268 |doi=10.1093/eurheartj/ehi492 |url=}}</ref> and angiotensin II,<ref>{{cite journal |author=Tsutsui H, Matsushima S, Kinugawa S, ''et al.'' |title=Angiotensin II type 1 receptor blocker attenuates myocardial remodeling and preserves diastolic function in diabetic heart |journal=Hypertens. Res. |volume=30 |issue=5 |pages=439–49 |year=2007 |month=May |pmid=17587756 |doi= 10.1291/hypres.30.439|url=http://joi.jlc.jst.go.jp/JST.JSTAGE/hypres/30.439?from=PubMed |format= &ndash; <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=intitle%3AAngiotensin+II+type+1+receptor+blocker+attenuates+myocardial+remodeling+and+preserves+diastolic+function+in+diabetic+heart&as_publication=Hypertens.+Res.&as_ylo=2007&as_yhi=2007&btnG=Search Scholar search]</sup>}} {{Dead link|date=June 2008}}</ref> and also by epidermal growth factor (EGF), which is a target of the signaling pathway activated by aldosterone<ref>{{cite journal |author=Krug AW, Grossmann C, Schuster C, ''et al.'' |title=Aldosterone stimulates epidermal growth factor receptor expression |journal=J. Biol. Chem. |volume=278 |issue=44 |pages=43060–6 |year=2003 |month=October |pmid=12939263 |doi=10.1074/jbc.M308134200 |url=}}</ref>
* Reduced perfusion of skeletal muscle causes atrophy of the muscle fibres. This can result in weakness, increased fatigueability and decreased peak strength - all contributing to exercise intolerance.<ref>{{GPnotebook|919601204|systemic pathophysiology in heart failure}}</ref>
 
===Edema===
*The increased peripheral resistance and greater blood volume place further strain on the heart and accelerates the process of damage to the myocardium. Vasoconstriction and fluid retention produce an increased hydrostatic pressure in the capillaries. This shifts the balance of forces in favour of [[interstitial fluid]] formation as the increased pressure forces additional fluid out of the blood, into the tissue. This results in [[edema]] (fluid build-up) in the tissues. In right-sided heart failure this commonly starts in the ankles where venous pressure is high due to the effects of gravity (although if the patient is bed-ridden, fluid accumulation may begin in the sacral region.) It may also occur in the abdominal cavity, where the fluid build-up is called ascites. In left-sided heart failure [[edema]] can occur in the lungs - this is called cardiogenic [[pulmonary edema]]. This reduces spare capacity for ventilation, causes stiffening of the lungs and reduces the efficiency of gas exchange by increasing the distance between the air and the blood. The consequences of this are shortness of breath, [[orthopnea]] and [[paroxysmal nocturnal dyspnea]].
The increased peripheral resistance and greater blood volume place further strain on the heart and accelerates the process of damage to the myocardium. Vasoconstriction and fluid retention produce an increased hydrostatic pressure in the capillaries. This shifts the balance of forces in favour of [[interstitial fluid]] formation as the increased pressure forces additional fluid out of the blood, into the tissue. This results in [[edema]] (fluid build-up) in the tissues. In right-sided heart failure this commonly starts in the ankles where venous pressure is high due to the effects of gravity (although if the patient is bed-ridden, fluid accumulation may begin in the sacral region.) It may also occur in the abdominal cavity, where the fluid build-up is called ascites. In left-sided heart failure [[edema]] can occur in the lungs - this is called cardiogenic [[pulmonary edema]]. This reduces spare capacity for ventilation, causes stiffening of the lungs and reduces the efficiency of gas exchange by increasing the distance between the air and the blood. The consequences of this are shortness of breath, [[orthopnea]] and [[paroxysmal nocturnal dyspnea]].
===Systemic Hypoperfusion===
In severe heart failure, the effects of decreased cardiac output and poor perfusion become more apparent, and patients will manifest symptoms of systemic hypoperfusion including with [cold and clammy extremities]], [[cyanosis]], [[claudication]], generalized [[weakness]], [[dizziness]], and [[syncope]].


===Right Heart Failure as a Result of Left Heart Failure===
===Right Heart Failure as a Result of Left Heart Failure===
*The [[hypoxia]] caused by [[pulmonary edema]] causes vasoconstriction in the pulmonary circulation, which results in [[pulmonary hypertension]]. Since the right ventricle generates far lower pressures than the left ventricle (approximately 20 mmHg versus around 120 mmHg, respectively, in the healthy individual) but nonetheless generates cardiac output exactly equal to the left ventricle, this means that a small increase in pulmonary vascular resistance causes a large increase in amount of work the right ventricle must perform.
*The [[hypoxia]] caused by [[pulmonary edema]] causes vasoconstriction in the pulmonary circulation, which results in [[pulmonary hypertension]]. Since the right ventricle generates far lower pressures than the left ventricle (approximately 20 mmHg versus around 120 mmHg, respectively, in the healthy individual) but nonetheless generates cardiac output exactly equal to the left ventricle, this means that a small increase in pulmonary vascular resistance causes a large increase in amount of work the right ventricle must perform.
*Other mechanisms of right heart failure are mediated by neurohormonal activation.<ref>{{cite book |author=Hunter JG, Boon NA, Davidson S, Colledge NR, Walker B |title=Davidson's principles & practice of medicine |publisher=Elsevier/Churchill Livingstone |location= |year=2006 |pages=544  |isbn=0-443-10057-8}}</ref> *Mechanical effects may also contribute. As the left ventricle distends, the intraventricular septum bows into the right ventricle, decreasing the filling capacity of the right ventricle.
*Other mechanisms of right heart failure are mediated by neurohormonal activation.<ref>{{cite book |author=Hunter JG, Boon NA, Davidson S, Colledge NR, Walker B |title=Davidson's principles & practice of medicine |publisher=Elsevier/Churchill Livingstone |location= |year=2006 |pages=544  |isbn=0-443-10057-8}}</ref>
*Mechanical effects may also contribute. As the left ventricle distends, the intraventricular septum bows into the right ventricle, decreasing the filling capacity of the right ventricle.


==Pathology==
===Microscopic Pathology===
==Microscopic Pathology==


[http://www.peir.net Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]
[http://www.peir.net Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology]
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==References==
==References==
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Latest revision as of 21:06, 29 July 2020

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Resident
Survival
Guide
Congestive Heart Failure Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Systolic Dysfunction
Diastolic Dysfunction
HFpEF
HFrEF

Causes

Differentiating Congestive heart failure from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

Clinical Assessment

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

Chest X Ray

Cardiac MRI

Echocardiography

Exercise Stress Test

Myocardial Viability Studies

Cardiac Catheterization

Other Imaging Studies

Other Diagnostic Studies

Treatment

Invasive Hemodynamic Monitoring

Medical Therapy:

Summary
Acute Pharmacotherapy
Chronic Pharmacotherapy in HFpEF
Chronic Pharmacotherapy in HFrEF
Diuretics
ACE Inhibitors
Angiotensin receptor blockers
Aldosterone Antagonists
Beta Blockers
Ca Channel Blockers
Nitrates
Hydralazine
Positive Inotropics
Anticoagulants
Angiotensin Receptor-Neprilysin Inhibitor
Antiarrhythmic Drugs
Nutritional Supplements
Hormonal Therapies
Drugs to Avoid
Drug Interactions
Treatment of underlying causes
Associated conditions

Exercise Training

Surgical Therapy:

Biventricular Pacing or Cardiac Resynchronization Therapy (CRT)
Implantation of Intracardiac Defibrillator
Ultrafiltration
Cardiac Surgery
Left Ventricular Assist Devices (LVADs)
Cardiac Transplantation

ACC/AHA Guideline Recommendations

Initial and Serial Evaluation of the HF Patient
Hospitalized Patient
Patients With a Prior MI
Sudden Cardiac Death Prevention
Surgical/Percutaneous/Transcather Interventional Treatments of HF
Patients at high risk for developing heart failure (Stage A)
Patients with cardiac structural abnormalities or remodeling who have not developed heart failure symptoms (Stage B)
Patients with current or prior symptoms of heart failure (Stage C)
Patients with refractory end-stage heart failure (Stage D)
Coordinating Care for Patients With Chronic HF
Quality Metrics/Performance Measures

Implementation of Practice Guidelines

Congestive heart failure end-of-life considerations

Specific Groups:

Special Populations
Patients who have concomitant disorders
Obstructive Sleep Apnea in the Patient with CHF
NSTEMI with Heart Failure and Cardiogenic Shock

Congestive heart failure pathophysiology On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Congestive heart failure pathophysiology

CDC on Congestive heart failure pathophysiology

Congestive heart failure pathophysiology in the news

Blogs on Congestive heart failure pathophysiology

Directions to Hospitals Treating Congestive heart failure pathophysiology

Risk calculators and risk factors for Congestive heart failure pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Saleh El Dassouki, M.D [3]; Atif Mohammad, MD

Overview

Heart failure is a complex syndrome whereby there is inadequate output of the heart to meet the metabolic demands of the body. Heart failure is caused by abnormal function of different anatomic parts of the heart including the pericardium, the myocardium, the endocardium, the heart valves and the great vessels. Heart failure is characterized by decreased cardiac output but not necessarily decreased ejection fraction. Symptoms of heart failure are due to a lack of both forward blood flow to the body, and backward flow into the lungs. The body tries to compensate for the low cardiac output by mechanisms that increase the preload and afterload. These mechanisms lead to exacerbation of the cardiac malfunction and symptoms associated with heart failure.

Pathophysiology

Decreased Cardiac Output

Underlying Cardiac Abnormalities Leading to Heart Failure

Heart failure may result from an abnormality or dysfunction of any one of the anatomical structures of the heart:

Systolic versus Diastolic Dysfunction

Systolic Dysfunction

Shown below is an image summarizing the pathophysiology of systolic heart failure.
Systolic heart failure.
Systolic heart failure.

Diastolic Dysfunction

  • Heart failure caused by diastolic dysfunction is generally described as the failure of the ventricular chambers to adequately relax and results from stiffening of the ventricular walls. The consequence is reduced filling of chambers of the heart.
  • The failure of ventricular relaxation also results in elevated end-diastolic pressures, and the end result is identical to the case of systolic dysfunction (pulmonary edema in left heart failure, peripheral edema in right heart failure.)
  • Diastolic dysfunction can be caused by processes similar to those that cause systolic dysfunction, particularly causes that affect cardiac remodeling.
  • Diastolic dysfunction typically becomes symptomatic in physiological conditions under which a high cardiac demand is required. Therefore, patients suffering from diastolic dysfunction are sensitive to increases in heart rate, and sudden bouts of tachycardia (which can be caused simply by physiological responses to exertion, fever, or dehydration, or by pathological tachyarrhythmias such as atrial fibrillation with rapid ventricular response) which may result in flash pulmonary edema.
  • Adequate rate control (usually with a pharmacological agent that slows down atrioventricular node conduction such as a calcium channel blocker or a beta-blocker) is therefore key to preventing decompensation.
  • Left ventricular diastolic function can be determined through echocardiography by measurement of various parameters such as the E/A ratio (early-to-atrial left ventricular filling ratio), the E (early left ventricular filling) deceleration time, and the isovolumetric relaxation time.

Manifestations of Heart Failure

Pulmonary Edema

Hypotension

Hypoperfusion

The reduction in forward cardiac output leads to hypoperfusion at rest which manifests as:

Impaired Cardiac Reserve

As the heart works harder to meet normal metabolic demands, the amount cardiac output can increase in times of increased oxygen demand (e.g. exercise) is reduced. This contributes to the exercise intolerance commonly seen in heart failure. This translates to the loss of one's cardiac reserve. The cardiac reserve refers to the ability of the heart to work harder during exercise or strenuous activity. Since the heart has to work harder to meet the normal metabolic demands, it is incapable of meeting the metabolic demands of the body during exercise.

Compensatory Mechanisms and Their Associated Complications

Shown below is an image summarizing the compensatory mechanisms of the heart along with their associated complications.
The compensatory mechanisms in heart failure.
The compensatory mechanisms in heart failure.
  1. Dilation of the left ventricle to increase the stroke volume and
  2. Increase in heart rate

Dilatation of the Left Ventricle:

Hypertrophy of the Myocardium:

  • Hypertrophy (an increase in physical size) of the myocardium can develop, which is caused by the terminally differentiated heart muscle fibers increasing in size in an attempt to improve contractility. This may contribute to the increased stiffness and decreased ability to relax during diastole.

Activation of the Sympathetic Nervous System:

  • Arterial blood pressure falls. This destimulates baroreceptors in the carotid sinus and aortic arch which link to the nucleus tractus solitarius. This center in the brain increases sympathetic activity, releasing catecholamines into the blood stream. Binding to alpha-1 receptors results in systemic arterial vasoconstriction. This helps restore blood pressure but also increases the total peripheral resistance, increasing the workload of the heart. Binding to beta-1 receptors in the myocardium increases the heart rate and make contractions more forceful, in an attempt to increase cardiac output. This also, however, increases the amount of work the heart has to perform.
  • The increased heart rate, stimulated by increased sympathetic activity[3] maintains cardiac output. Initially, this helps compensate for heart failure by maintaining blood pressure and perfusion, but places further strain on the myocardium, increasing coronary perfusion requirements, which can lead to worsening of ischemic heart disease. Sympathetic activity may also cause potentially fatal arrhythmias.
  • Increased sympathetic stimulation also causes the hypothalamus to secrete vasopressin (also known as antidiuretic hormone or ADH), which causes free water retention in the kidneys leading to hyponatremia. This free water retention increases total body blood volume and blood pressure.

Stimulation of the Renal / Adrenal / Sympathetic Axis:

  • Reduced perfusion (blood flow) to the kidneys stimulates the release of renin – an enzyme which catalyses the production of the potent vasopressor angiotensin. Angiotensin and its metabolites cause further vasocontriction, and stimulate increased secretion of the steroid aldosterone from the adrenal glands. This promotes salt and fluid retention at the kidneys, also increasing the blood volume.
  • The chronically high levels of circulating neuroendocrine hormones such as catecholamines, renin, angiotensin, and aldosterone affects the myocardium directly, causing structural remodelling of the heart over the long term. Many of these remodelling effects seem to be mediated by transforming growth factor beta (TGF-beta), which is a common downstream target of the signal transduction cascade initiated by catecholamines[4] and angiotensin II,[5] and also by epidermal growth factor (EGF), which is a target of the signaling pathway activated by aldosterone[6]
  • The increased peripheral resistance and greater blood volume place further strain on the heart and accelerates the process of damage to the myocardium. Vasoconstriction and fluid retention produce an increased hydrostatic pressure in the capillaries. This shifts the balance of forces in favour of interstitial fluid formation as the increased pressure forces additional fluid out of the blood, into the tissue. This results in edema (fluid build-up) in the tissues. In right-sided heart failure this commonly starts in the ankles where venous pressure is high due to the effects of gravity (although if the patient is bed-ridden, fluid accumulation may begin in the sacral region.) It may also occur in the abdominal cavity, where the fluid build-up is called ascites. In left-sided heart failure edema can occur in the lungs - this is called cardiogenic pulmonary edema. This reduces spare capacity for ventilation, causes stiffening of the lungs and reduces the efficiency of gas exchange by increasing the distance between the air and the blood. The consequences of this are shortness of breath, orthopnea and paroxysmal nocturnal dyspnea.

Right Heart Failure as a Result of Left Heart Failure

  • The hypoxia caused by pulmonary edema causes vasoconstriction in the pulmonary circulation, which results in pulmonary hypertension. Since the right ventricle generates far lower pressures than the left ventricle (approximately 20 mmHg versus around 120 mmHg, respectively, in the healthy individual) but nonetheless generates cardiac output exactly equal to the left ventricle, this means that a small increase in pulmonary vascular resistance causes a large increase in amount of work the right ventricle must perform.
  • Other mechanisms of right heart failure are mediated by neurohormonal activation.[7]
  • Mechanical effects may also contribute. As the left ventricle distends, the intraventricular septum bows into the right ventricle, decreasing the filling capacity of the right ventricle.

Microscopic Pathology

Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

  • HEART: Congestive heart failure, hydropic change

    HEART: Congestive heart failure, hydropic change

  • HEART: Congestive heart failure, hydropic change

    HEART: Congestive heart failure, hydropic change

  • HEART: Congestive heart failure, hydropic change

    HEART: Congestive heart failure, hydropic change


  • HEART: Congestive heart failure, hydropic change

    HEART: Congestive heart failure, hydropic change

  • HEART: Congestive heart failure, hydropic change

    HEART: Congestive heart failure, hydropic change

  • HEART: Congestive heart failure, hydropic change

    HEART: Congestive heart failure, hydropic change


  • Lung, congestion, heart failure cells (hemosiderin laden macrophages)

    Lung, congestion, heart failure cells (hemosiderin laden macrophages)

  • Lung, Congestive Heart Failure, bone marrow embolus

    Lung, Congestive Heart Failure, bone marrow embolus

  • Lung, pulmonary edema in patient with congestive heart failure due to heart transplant rejection

    Lung, pulmonary edema in patient with congestive heart failure due to heart transplant rejection


  • HEART: Congestive heart failure, hydropic change

    HEART: Congestive heart failure, hydropic change

  • HEART Congestive heart failure, hydropic change

    HEART Congestive heart failure, hydropic change

  • Spleen, congestion, congestive heart failure

    Spleen, congestion, congestive heart failure

References

  1. ↑ Template:GPnotebook
  2. ↑ Boron and Boulpaep 2005 Medical Physiology Updated Edition p533 ISBN 0-7216-3256-4
  3. ↑ Rang HP (2003). Pharmacology. Edinburgh: Churchill Livingstone. p. 127. ISBN 0-443-07145-4.
  4. ↑ Shigeyama J, Yasumura Y, Sakamoto A; et al. (2005). "Increased gene expression of collagen Types I and III is inhibited by beta-receptor blockade in patients with dilated cardiomyopathy". Eur. Heart J. 26 (24): 2698–705. doi:10.1093/eurheartj/ehi492. PMID 16204268. Unknown parameter |month= ignored (help)
  5. ↑ Tsutsui H, Matsushima S, Kinugawa S; et al. (2007). "Angiotensin II type 1 receptor blocker attenuates myocardial remodeling and preserves diastolic function in diabetic heart" (– Scholar search). Hypertens. Res. 30 (5): 439–49. doi:10.1291/hypres.30.439. PMID 17587756. Unknown parameter |month= ignored (help)[dead link]
  6. ↑ Krug AW, Grossmann C, Schuster C; et al. (2003). "Aldosterone stimulates epidermal growth factor receptor expression". J. Biol. Chem. 278 (44): 43060–6. doi:10.1074/jbc.M308134200. PMID 12939263. Unknown parameter |month= ignored (help)
  7. ↑ Hunter JG, Boon NA, Davidson S, Colledge NR, Walker B (2006). Davidson's principles & practice of medicine. Elsevier/Churchill Livingstone. p. 544. ISBN 0-443-10057-8.

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