Situation: A 45-year-old man with hypertrophic cardiomyopathy (HCM) is admitted to the coronary care unit after fainting at home. Echocardiography shows a thickened septum with left ventricular outflow tract obstruction. He has vomited repeatedly for 2 days. His blood pressure is 82/50 mmHg, heart rate 118/min, lungs are clear, and mucous membranes are dry. The physician writes these orders. Which order should the nurse question?

Obstructive HCM is an exception to the usual use of inotropes for hypotension from pump failure: dobutamine makes the thick ventricle contract harder and faster, narrowing the outflow tract and worsening obstruction and hypotension. Hypotension in obstructive HCM is treated with fluids and a pure vasoconstrictor such as phenylephrine, and a beta blocker is resumed once pressure allows because it improves filling.

Clinical context
A 45-year-old man with known hypertrophic cardiomyopathy (HCM) presents after syncope. Echocardiography confirms asymmetric septal hypertrophy with left ventricular outflow tract (LVOT) obstruction. He is volume-depleted from 2 days of vomiting, with hypotension (82/50 mmHg), tachycardia (118/min), and dry mucous membranes. The central question is which physician order is unsafe in obstructive HCM with hypotension.

Why dobutamine is the wrong choice
In most hypotensive patients with poor cardiac output, an inotrope such as dobutamine seems logical. However, obstructive HCM is a major exception. The thickened septum plus systolic anterior motion of the mitral valve creates a dynamic narrowing of the LVOT. Dobutamine is a beta-1 agonist that increases both contractility and heart rate. Stronger, faster contraction pulls the mitral valve closer to the hypertrophied septum, making the outflow tract narrower and worsening the obstruction. As obstruction worsens, stroke volume falls further, and blood pressure drops even more. This creates a dangerous spiral of worsening hypotension and reduced coronary perfusion. Watch out! Inotropes that increase contractility are contraindicated in obstructive HCM with hypotension because they aggravate the very obstruction causing the low output.

What actually helps in this scenario
The hypotension in this patient has two contributors: volume depletion from vomiting and dynamic LVOT obstruction. Management follows a specific sequence. First, intravenous 0.9% sodium chloride bolus restores preload. Adequate preload helps keep the LVOT open by increasing ventricular filling and reducing the degree of systolic anterior motion. Second, a pure vasoconstrictor such as phenylephrine raises systemic vascular resistance without increasing contractility or heart rate. This improves coronary perfusion pressure and blood pressure without worsening the obstruction. Third, once systolic pressure exceeds 100 mmHg, a beta blocker such as metoprolol is resumed. Beta blockers slow the heart rate and reduce contractility, which increases diastolic filling time and decreases the outflow gradient.

Intervention	Effect on obstructive HCM	Safety in this patient
Dobutamine infusion	Increases contractility and heart rate; narrows LVOT; worsens obstruction and hypotension	Unsafe — should be questioned
Oral metoprolol once SBP > 100 mmHg	Slows heart rate; improves diastolic filling; reduces LVOT gradient	Safe once pressure is adequate
IV 0.9% sodium chloride bolus	Restores preload; reduces systolic anterior motion; opens LVOT	Safe and appropriate first step
Phenylephrine infusion titrated to BP	Pure vasoconstriction; raises BP without increasing contractility	Safe and appropriate for hypotension

Pathophysiology link to the evidence
The 2026 Taiwan Society of Cardiology consensus emphasizes that HCM is a heterogeneous disease in which dynamic LVOT obstruction, diastolic dysfunction, and myocardial ischemia can all contribute to heart failure and shock ^[1]. The 2024 review by Zakynthinos and colleagues specifically notes that managing cardiogenic shock in HCM requires strategies tailored to the distinct pathophysiology, including avoidance of agents that worsen the outflow gradient ^[2]. The imaging review by Cutts and Kramer reinforces that the morphologic changes in HCM — particularly septal hypertrophy and systolic anterior motion — are responsible for symptoms and hemodynamic instability ^[3]. These sources support the principle that therapy must reduce, not increase, the outflow gradient.

Nursing priority and safety check
When reviewing orders for a patient with obstructive HCM and hypotension, the nurse must recognize that any drug that increases contractility or heart rate can convert a stable obstruction into a life-threatening low-output state. Dobutamine is the order to question because it directly opposes the therapeutic goal of reducing the LVOT gradient. Key point! In obstructive HCM with hypotension, the correct sequence is volume first, then pure vasoconstriction, then beta blockade once blood pressure permits — never an inotrope that increases contractility.