Hypertrophic cardiomyopathy case study one
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. ; Associate Editor(s)-in-Chief: Soroush Seifirad, M.D.
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:
- Reduced pre-load which can be due to:
- Venodilators such as nitrates
- Following epidural blockade
- Withdrawal of beta-blockers or calcium channel blockers
- Decreased afterload due to:
- Vasodilator therapy
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.