Which drug is most appropriate to treat hypotension in a patient with hypertrophic obstructive cardiomyopathy after induction?

Which drug is most appropriate to treat hypotension in a patient with hypertrophic obstructive cardiomyopathy after induction?

• A. Ephedrine
• B. Phenylephrine
• C. Isoproterenol
• D. Epinephrine

Answer: (B)

In hypertrophic obstructive cardiomyopathy, the left ventricular outflow tract (LVOT) obstruction is dynamic and worsens with increased contractility, decreased preload, or decreased afterload. When hypotension occurs after induction, the goal is to raise afterload and maintain preload while avoiding increases in contractility or heart rate. Phenylephrine is a pure alpha-1 agonist. It causes vasoconstriction, raising systemic vascular resistance and afterload without tangibly increasing heart rate or myocardial contractility. This helps reduce the LVOT obstruction by pushing the outflow gradient outward and improves blood pressure. In contrast, drugs with beta effects like ephedrine (which increases heart rate and contractility), epinephrine (strong beta effects with increased contractility and heart rate), or isoproterenol (a potent beta agonist very likely to raise contractility and tachycardia) can worsen the obstruction and are thus less suitable in this scenario.

In hypertrophic obstructive cardiomyopathy, the left ventricular outflow tract (LVOT) obstruction is dynamic and worsens with increased contractility, decreased preload, or decreased afterload. When hypotension occurs after induction, the goal is to raise afterload and maintain preload while avoiding increases in contractility or heart rate.

Phenylephrine is a pure alpha-1 agonist. It causes vasoconstriction, raising systemic vascular resistance and afterload without tangibly increasing heart rate or myocardial contractility. This helps reduce the LVOT obstruction by pushing the outflow gradient outward and improves blood pressure.

In contrast, drugs with beta effects like ephedrine (which increases heart rate and contractility), epinephrine (strong beta effects with increased contractility and heart rate), or isoproterenol (a potent beta agonist very likely to raise contractility and tachycardia) can worsen the obstruction and are thus less suitable in this scenario.