Hypertrophic cardiomyopathy case study one

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.