Hypertrophic obstructive cardiomyopathy
Stem
A 34-year-old man, 80 kg, with hypertrophic cardiomyopathy is scheduled for arthroscopic rotator cuff repair in the beach-chair position. His septum measures 21 mm, the resting outflow gradient is 40 mmHg and rises to 85 mmHg with Valsalva, with systolic anterior motion of the mitral valve. He takes metoprolol, gets lightheaded climbing stairs, and has no history of syncope or arrhythmia. Blood pressure is 118/72, heart rate 62.
Question
How will you anesthetize him, and what are you trying to avoid?
Ideal answer
HeadlineDynamic outflow obstruction: less preload, less afterload, more contractility or rate pulls the mitral leaflet into the septum.1 I keep him full, constricted, slow and unstimulated.
- Metoprolol the morning of surgery, because beta-blockade is first-line therapy and withdrawal invites tachycardia.2
- Fluid bolus; arterial line, ideally before he sits up, then raise the beach chair slowly in stages, because it is a preload challenge.
- Interscalene block, no epinephrine in the local, sparing the surges of pain and catecholamines.
- Smooth, unhurried induction, opioid for laryngoscopy, adequately deep, because sympathetic surges raise the gradient.
- Phenylephrine is my pressor, restoring afterload without raising contractility or rate; no ephedrine, epinephrine or dobutamine,3 no nitrates, big diuretic or vasodilator doses.1
Watch for: instability; TEE is my rescue tool, separating obstruction from hypovolemia and failure at a glance.
Breaking down the answer
- Name the physiology — obstruction is a peak gradient of 30 mmHg or more, and 50 mmHg or more generally causes symptoms; systolic anterior motion also causes posteriorly directed MR.1 It shows I am managing a dynamic, load-dependent lesion.
- Provocation — when the resting gradient is under 50 mmHg, the guideline uses Valsalva to unmask it.2 His 85 mmHg provoked gradient is what anesthesia will reproduce.
- Rate-control ladder — non-vasodilating beta-blockers first, then verapamil or diltiazem; verapamil is contraindicated with hypotension or a resting gradient above 100 mmHg.2
- Preload is protective — reduced preload and vasodilation worsen obstruction, which is why ACE inhibitors are also avoided.1 Changes if: insufflation or a neuraxial sympathectomy, each a further preload hit.
- Inotropes make it worse — they raise rate and contractility and the gradient.3 The single most-graded decision on the page.
- Drug status — a cardiac myosin inhibitor such as mavacamten matters; if ejection fraction falls below 50%, it is stopped and HFrEF therapy started.2
Follow-up question
As the table is raised to 70 degrees, his pressure falls to 72/40 with a heart rate of 108, and a new loud systolic murmur is heard. The resident reaches for ephedrine. What do you do?
Follow-up answer
HeadlineDynamic outflow obstruction from sudden preload loss; I stop the ephedrine and say why: it will make it worse.
I ask the surgeon to pause and lower the back of the bed toward flat to return venous blood. Phenylephrine boluses and a rapid fluid bolus; deeper anesthesia only if light. Once pressure recovers, esmolol slows the rate, lengthening filling time and reducing contractility. If he does not respond, TEE to confirm systolic anterior motion and rule out hypovolemia from another cause or new failure. I reassess the arterial line and murmur, then raise him again slowly with a phenylephrine infusion running. If pressure stays poor, the surgery is done flatter or later.
Pitfalls that cost points
- Reaching for nitroglycerin when the pressure or ST segments change.
- Treating hypotension with ephedrine, epinephrine or dobutamine.
Rapid-fire
Q: What wall thickness defines HCM in adults? A: 15 mm or more without another cause, or 13 mm with a family history or sarcomeric variant.1
Q: How common is it? A: About 1 in 200 to 1 in 500 adults.1
Q: How is AF anticoagulated in HCM? A: With a DOAC first line, regardless of CHA2DS2-VASc score.2
Q: Who needs an ICD? A: Anyone with HCM and prior VT or cardiac arrest.2
Q: Why does the murmur get louder with Valsalva? A: Lower preload shrinks the cavity and increases obstruction.1
Numbers to know
| Item | Value |
|---|---|
| Diagnostic wall thickness | 15 mm or more1 |
| Obstruction | Peak gradient 30 mmHg or more1 |
| Symptomatic gradient | 50 mmHg or more1 |
| Provocation if resting gradient | Below 50 mmHg2 |
| Verapamil contraindicated | Resting gradient above 100 mmHg or hypotension2 |
Links
- Aortic stenosis, Intraoperative hypotension: differential and management, Vasopressors and inotropes: choosing and titrating, Interscalene block and its complications, Atrial fibrillation: new onset and chronic
- Atlas: Basic valvular lesions on 2D and color
- 2024 AHA/ACC/multisociety hypertrophic cardiomyopathy guideline
Sources
- 1.Hypertrophic Cardiomyopathy · Merck Manual Professional Edition · merckmanuals.com
- 2.2024 AHA/ACC/Multisociety Hypertrophic Cardiomyopathy Guideline: Key Points · American College of Cardiology, 2024 · acc.org
- 3.Anaesthetic management in a case of concurrent hypertrophic cardiomyopathy and constrictive pericarditis: Are there special concerns? · Indian Journal of Anaesthesia (PubMed Central), 2016 · pmc.ncbi.nlm.nih.govCase report; used only for the mechanism of inotropes raising the gradient and phenylephrine for hypotension.
Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.