ACE Inhibitors Should Be Avoided or Discontinued in Hypertrophic Obstructive Cardiomyopathy (HOCM)
ACE inhibitors are contraindicated in patients with obstructive HCM because their vasodilatory effects worsen left ventricular outflow tract (LVOT) obstruction, exacerbate symptoms, and can precipitate hemodynamic collapse. 1
Why ACE Inhibitors Are Harmful in HOCM
The pathophysiology of HOCM centers on dynamic LVOT obstruction that worsens with reduced afterload. ACE inhibitors act as pure vasodilators, which:
- Decrease systemic vascular resistance, reducing the afterload that normally opposes the outflow gradient 1
- Worsen the pressure gradient across the LVOT by allowing more vigorous ejection into a dilated arterial system 1
- Exacerbate symptoms of angina and dyspnea that are directly attributable to the dynamic obstruction 1
Guideline Recommendations
The most recent 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guidelines explicitly state that discontinuation of vasodilators including ACE inhibitors may be reasonable because these agents can worsen symptoms caused by dynamic outflow tract obstruction (Class IIb recommendation). 1
The 2020 AHA/ACC guidelines similarly recommend that for patients with obstructive HCM, discontinuation of vasodilators (including ACE inhibitors and ARBs) may be reasonable because they worsen symptoms from dynamic obstruction. 1
The 2011 ACCF/AHA guidelines were even more cautious, stating that the usefulness of ACE inhibitors in treatment of symptoms in patients with HCM with preserved systolic function is not well established, and these drugs should be used with caution (if at all) in patients with resting or provocable LVOT obstruction. 1
Clinical Algorithm for Managing Vasodilators in HOCM
Step 1: Identify if obstruction is present
- Measure resting LVOT gradient (>30 mmHg is significant) 1
- Perform provocative maneuvers (Valsalva, exercise) if resting gradient is normal 1
Step 2: If obstruction is confirmed (gradient ≥30 mmHg)
- Immediately discontinue ACE inhibitors, ARBs, and dihydropyridine calcium channel blockers 1
- Review all medications for vasodilatory properties 1
Step 3: Initiate appropriate therapy
- Start non-vasodilating beta-blockers as first-line (target heart rate <60-65 bpm) 1, 2, 3
- If beta-blockers fail or are not tolerated, use verapamil or diltiazem (non-dihydropyridine calcium channel blockers) 1, 3
- Add low-dose diuretics cautiously only if volume overload persists despite rate-controlling agents 1
Important Exception: Non-Obstructive HCM with Systolic Dysfunction
The only scenario where ACE inhibitors may be used is when HCM progresses to the "burned-out" phase with systolic dysfunction (LVEF <50%) and loss of obstruction. 2, 3
In this situation:
- The dynamic obstruction is no longer present 3
- The patient now has heart failure with reduced ejection fraction 2
- Guideline-directed medical therapy for HFrEF is recommended, which includes ACE inhibitors or ARBs 2, 3
Common Clinical Pitfalls
Pitfall #1: Using ACE inhibitors for concurrent hypertension
- Even if the patient has hypertension, ACE inhibitors will worsen HOCM symptoms 1
- Use beta-blockers or non-dihydropyridine calcium channel blockers instead, which treat both conditions 1
Pitfall #2: Assuming all HCM patients need vasodilators
- Only patients with non-obstructive HCM who are asymptomatic can potentially tolerate vasodilators 1
- Always assess for provocable gradients before prescribing 1
Pitfall #3: Continuing ACE inhibitors "for renal protection"
- The risk of worsening LVOT obstruction and precipitating hemodynamic collapse outweighs theoretical renal benefits 1
- Reassess the treatment strategy if symptoms emerge after medication initiation 1
Summary of Medication Classes to Avoid in Obstructive HCM
Absolutely contraindicated (Class III: Harm):
- Positive inotropes (dobutamine, dopamine, norepinephrine) 1, 2
- Dihydropyridine calcium channel blockers (nifedipine, amlodipine) 1, 2, 3
- Digoxin (in absence of atrial fibrillation) 1, 3
Should be discontinued (Class IIb):