Hypertrophic cardiomyopathy in special clinical scenarios
Editors-In-Chief: C. Michael Gibson, M.S., M.D. [1], Cafer Zorkun, M.D. [2], Caitlin J. Harrigan [3], Martin S. Maron, M.D., and Barry J. Maron, M.D.
Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [4] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Management of HCM in presence of hypotension and cardiovascular collapse
The first patient I (C. Michael Gibson, M.D.) treated as a medical student was an 18 year old woman who had HOCM. She had just entered college and had partied throughout the night. She was vomiting, developed new atrial fibrillation at a rate of 180 beats per minute. She had a syncopal episode and had a systolic blood pressure of 60 mm Hg. This young lady had sustained hemodynamic collapse as a result of volume depletion and tachycardia.
Precipitants of Hemodynamic Collapse
- Volume depletion or dehydration which can be due to:
- Vomiting
- Diuretics
- Hemorrhage
- Reduced pre-load which can be due to:
- Sepsis
- Venodilators such as nitrates
- Following epidural blockade
- Tachycardia
- Withdrawal of beta-blockers or calcium channel blockers
- Decreased afterload due to:
- Vasodilator therapy
- Sepsis
Physical examination Findings in Hemodynamic Collapse
A rapid, weak pulse is present in the patient who is hypotensive. The JVP is flat. A systolic murmur is present.
Echocardiographic Findings in Hemodynamic Collapse
- A small hypercontractile left ventricle is present
- Prolonged systolic anterior motion of the mitral valve is present
- Mitral regurgitation with a posterior directed jet
Treatment of Hemodynamic Collapse
Initial treatment includes the following:
- Avoid nitrates even though it appears the patient is in heart failure!
- Avoid vasodilators again even though it appears the patient is in heart failure! Both these agents could cause further hemodynamic compromise.
- Administer beta-blockers to slow the heart rate and fluids to raise the left ventricular filling pressures.
- Elevate the legs to increase venous return and raise the preload
If the patient does not respond to these measures, then the following can also be administered:
- Intravenous phenylephrine at a rate of 100 to 180 µg/min, which is then reduced to 2 to 3 mL/min (40 to 60 drops/min).
- How to mix the phenylephrine: Make a solution that contains 10 mg (1 mL of 1 percent phenylephrine) of phenylephrine diluted in 500 mL of D5W. Administer at a rate of 5 to 9 mL/min (i.e. 100 to 180 drops/min assuming there are 20 drops/mL). This solution provides a phenylephrine drip of 100 to 180 µg/min.
- Outside of the US, intravenous disopyramide at a dose of 50 mg over one to five minutes can be administered.
Management of the HCM Patient During Pregnancy
Among HCM patients who chronically have mild symptoms, pregnancy is generally well tolerated [1][2]. Although pregnancy causes vasodilation which should exacerbate the outflow gradient, pregnancy also causes fluid retention and an increase in plasma volume which increases preload and offsets the reduction in afterload. In a series of 100 HCM patients, only one of 28 asymptomatic patients developed NYHA Class III or IV heart failure. Among 12 previously symptomatic patients, 5 patients developed NYHA Class III or IV heart failure. It is notable that two sudden deaths occurred in this series of 100 patients. One of the two patients had a resting gradient of 115 mm Hg. The other patient had a markedly positive family history with 8 family members sustaining any early death, 5 of which were sudden death [2].
Although beta blockers and verapamil may improve symptoms in the mother, the dosing should be limited to minimize the risk of fetal bradycardia, growth retardation and hypoglycemia, and growth retardation. There is more experience with the use beta blockers during pregnancy.
Due to the potential for venous pooling, epidural anesthesia should be avoided.. Blood should be crossed and typed in case a transfusion is needed for bleeding, which can exacerbate outflow obstruction. Home delivery without IV access is not preferred. Vaginal delivery is usually successful.
References
- ↑ Oakley GD, McGarry K, Limb DG, Oakley CM (1979). "Management of pregnancy in patients with hypertrophic cardiomyopathy". British Medical Journal. 1 (6180): 1749–50. PMC 1599373. PMID 572730. Unknown parameter
|month=ignored (help) - ↑ 2.0 2.1 Autore C, Conte MR, Piccininno M, Bernabò P, Bonfiglio G, Bruzzi P, Spirito P (2002). "Risk associated with pregnancy in hypertrophic cardiomyopathy". Journal of the American College of Cardiology. 40 (10): 1864–9. PMID 12446072. Unknown parameter
|month=ignored (help)