Hypertrophic cardiomyopathy in special clinical scenarios

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Editors-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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.