Hypertrophic cardiomyopathy differential diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Soroush Seifirad, M.D.[2]

Overview

Hypertrophic cardiomyopathy must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as [differential dx1], [differential dx2], and [differential dx3].

OR

Hypertrophic cardiomyopathy must be differentiated from [[differential dx1], [differential dx2], and [differential dx3].

Differentiating Hypertrophic cardiomyopathy from other Diseases

Hypertrophic cardiomyopathy must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as [differential dx1], [differential dx2], and [differential dx3].

OR

Hypertrophic cardiomyopathy must be differentiated from [differential dx1], [differential dx2], and [differential dx3].

OR

As Hypertrophic cardiomyopathy manifests in a variety of clinical forms, differentiation must be established in accordance with the particular subtype. [Subtype name 1] must be differentiated from other diseases that cause [clinical feature 1], such as [differential dx1] and [differential dx2]. In contrast, [subtype name 2] must be differentiated from other diseases that cause [clinical feature 2], such as [differential dx3] and [differential dx4].

Differentiating Hypertrophic cardiomyopathy from other diseases on the basis of [symptom 1], [symptom 2], and [symptom 3]

On the basis [symptom 1], [symptom 2], and [symptom 3], Hypertrophic cardiomyopathy must be differentiated from [disease 1], [disease 2], [disease 3], [disease 4], [disease 5], and [disease 6].

Cardiomyopathy must be differentiated from athlete heart (which is often confused with HCM on echocardiography), hypertrophy due to hypertension or aortic stenosis; as these have common clinical features, including thickened myocardium on imaging and high QRS voltage on EKGs.

Diseases	Clinical manifestations						Para-clinical findings							Gold standard	Additional findings
	Symptoms			Physical examination
							Lab Findings			Imaging			Histopathology
	Symptom 1	Symptom 2	Symptom 3	Physical exam 1	Physical exam 2	Physical exam 3	Lab 1	Lab 2	Lab 3	Imaging 1	Imaging 2	Imaging 3
Differential Diagnosis 1
Differential Diagnosis 2
Differential Diagnosis 3
Diseases	Symptom 1	Symptom 2	Symptom 3	Physical exam 1	Physical exam 2	Physical exam 3	Lab 1	Lab 2	Lab 3	Imaging 1	Imaging 2	Imaging 3	Histopathology	Gold standard	Additional findings
Differential Diagnosis 4
Differential Diagnosis 5
Differential Diagnosis 6

Based on an increased LV to aortic gradient

• Sever Volume depletion:
• These patients may develop hyperdynamic ventricular function in an effort to maintain cardiac output in the setting of normal LV systolic function.
• Here is the sequence of events in this setting:

• Hyperdynamic LV function
• Vigorous blood ejection at a higher velocity than normal
• An increased intracavitary gradient
• This may be mistaken for an increased LVOT gradient.

Subaortic stenosis:

• A congenital abnormality typically caused by a thin membrane of tissue in the LVOT
• Fixed subaortic stenosis can usually be distinguished from HCM and valvular AS by echocardiography or invasive cardiac catheterization.
• There is no systolic anterior motion of the mitral valve, and generally the ventricular wall thickness is normal. Nevertheless, chronic long-standing LV hypertension may finally lead to concentric LVH.
• The aortic valve leaflets are usually normal, but in decades these patients may develop aortic valve damage as well.

Valvular aortic stenosis:

• In addition to potentially causing LVH, narrowing of the aortic valve opening can lead to a significant pressure gradient between the LV and the aorta.
• similar to subaortic stenosis, valvular AS can be distinguished from other pathology by echocardiography or invasive cardiac catheterization.

Overview

The diagnostic imaging modality of choice is echocardiography. There are multiple echocardiographic features that distinguish hypertrophic cardiomyopathy from other conditions that lead to myocardial hypertrophy. In hypertrophic cardiomyopathy, the left ventricle is not dilated, and there is no other condition that would account for the magnitude of hypertrophy. The hypertrophy is often asymmetric.

Differential Diagnosis

HCM must be distinguished from the following disorders:

Athlete's heart

Quite often, HCM can be mistaken for a condition known as athlete’s heart. Both involve growth of the myocardium, however the latter generally is not correlated with incidences of SCD. While HCM can be linked to family history, athlete’s heart arises purely as a function of intense exercise (usually at least an hour a day, everyday. Since the body is operating at high training levels, the heart adapts and grows in order to pump blood more efficiently. Stoppage of exercise for three months generally leads to a decrease in wall/septum thickness in those with athlete’s heart, whereas those with HCM exhibit no decline.

People with athlete’s heart do not exhibit an abnormally enlarged septum, and the growth of heart muscle at the septum and free ventricular wall is symmetrical. The asymmetrical growth seen in HCM results in a less-dilated left ventricle. This in turn leads to a smaller volume of blood leaving the heart with each beat.

	Athlete's Heart	HCM
Septum thickness	<15 mm	>15 mm
Symmetry	Yes (for septum and LV wall)	No (septum much thicker
Family history	None	Possibly
Deconditioning	Reduction within 3 months	None

Several criteria can be used to distinguish these two entities:

The degree of left ventricular wall thickness

• In athlete's heart the LVH is symmetric and less than or equal to 12 mm
• Rarely the LV thickness can be 14-16 mm and this makes it difficult to distinguish from HOCM. Athletes who engage in strength training may develop this pattern, ahtletes who engage in endurance training do not.
• If the degree of thickening is out of proportion to the type and intensity of exercise, this suggests HOCM

The pattern of left ventricular wall thickness

• Athleste's heart is symmetric
• HOCM is more often asymmetric, but may in some cases be symmetric

The left ventricular cavity size

• HOCM has smaller LV cavitary dimensions

Anderson-Fabry disease

(X-linked deficiency of the lysosomal enzyme alphagalactosidase)

Overview

Aortic stenosis must be differentiated from other cardiac or pulmonary causes of dyspnea, weakness, and dizziness. Furthermore, when left ventricular outflow tract obstruction is present, it is critical to identify whether the obstruction is subvalvular, valvular or supravalvular and whether there is hypertrophic cardiomyopathy (HOCM) or not.

Differentiating Aortic Stenosis from other Diseases

Pulmonary Causes of Dyspnea

Aortic stenosis can be differentiated from pulmonary causes of dyspnea by the presence of:

• A narrow pulse pressure
• A harsh late-peaking systolic murmur heard best at the right second intercostal space with radiation to the carotid arteries
• A delayed slow-rising carotid upstroke (pulsus parvus et tardus)
• Signs of heart failure on examination

Aortic Sclerosis

While a murmur may be heard in aortic sclerosis, there is no fusion of the commisures and no significant obstruction to antegrade blood flow across the aortic valve. As a result, the S2 is normal in aortic sclerosis and the carotid upstroke is normal (i.e. pulsus parvus et tardus is absent).

Mitral Regurgitation

The murmur of aortic stenosis is harsh and best heard at the right second intercostal space while the murmur of mitral regurgitation is blowing, soft and best heard at the apex.

Hypertrophic Obstructive Cardiomyopathy

In HOCM the murmur is dynamic and varies with maneuvers. Moreover, there is a bifid or spoke and dome pattern of the carotid upstroke.

Valvular, Subvalvular and Supravalvular Aortic Stenosis

Differentiating Valvular Aortic Stenosis from Subvalvular Aortic Stenosis

Aortic insufficiency is more often present with subvalvular aortic stenosis (in 50% to 75% of cases). Symptoms associated with subvalvular aortic stenosis begin earlier in life (in childhood or adolescence) than symptoms associated with valvular aortic stenosis.

Differentiating Valvular Aortic Stenosis from Supravalvular Aortic Stenosis

Supravalvular aortic stenosis is an uncommon congenital anomaly caused by a narrowing in the ascending aorta or by the presence of a fibrous diaphragm just above the aortic valve. It presents in early adulthood. Although the aortic valve is not stenotic, doppler shows an increased pressure gradient. 50% of patients with supravalvular aortic stenosis have a characteristically greater pulse and systolic blood pressure in the right carotid and brachial arteries than in the left. The systolic murmur is maximal below the right clavicle and radiates primarily to the right carotid artery. There is not an ejection click nor a diastolic murmur.

Differentiating hypertrophic cardiomyopathy and valvular aortic stenosis

	Aortic stenosis	Hypertrophic cardiomyopathy
Echocardiography
Aortic valve calcification	Common	No
Dilated ascending aorta	Common	Rare
Ventricular hypertrophy	Concentric LVH	Asymmetric, often involving the septum
Physical examination
Murmur of AI	Common	No
Pulse pressure after PVC	Increased	Decreased
Valsalva maneuver	Decreased intensity of murmur	Increased intensity of murmur
Carotid pulsation	Normal or tardus et parvus	Brisk, jerky, or bisferiens pulse (a collapse of the pulse followed by a secondary rise)

Hypertensive heart disease

• Long-standing HTN is the most common cause of LVH

• Most of the LVH due ti HTN cases will present beyond adolescence, when HCM is most commonly identified.
• The magnitude of hypertrophy seen in hypertension, however, rarely leads to wall thicknesses in excess of 1.5 cm.
• Hypertension is usually suspected in persons with an extended history of elevated blood pressures (10 or more years), particularly in those with other evidence of end-organ damage due to hypertension (eg, retinopathy, nephropathy).