Drug contraindicated in HOCM
Reading File
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Reading File
Reading File
Reading File
Finding Sources
Finding Sources
Reading File
Reading File
Finding Sources
Reading File
I now have comprehensive information from the textbooks. Here is the full, well-sourced answer:
Drugs Contraindicated in HOCM
The core principle: anything that reduces preload, reduces afterload, or increases contractility/heart rate will worsen the dynamic LVOT obstruction in HOCM.
1. Nitrates (e.g., Nitroglycerin)
Contraindicated. Nitrates cause venodilation, reducing preload and ventricular volume. A smaller LV cavity brings the septal wall and anterior mitral leaflet closer together, worsening the outflow tract gradient. As stated in Rosen's Emergency Medicine: "Nitroglycerin should be avoided in HCM-associated chest pain because it decreases ventricular volume, exacerbating outflow tract obstruction." - Rosen's Emergency Medicine, p. 1116
2. Positive Inotropes (Digoxin, Dobutamine, Dopamine)
Contraindicated. These increase myocardial contractility, which increases systolic obliteration of the LV cavity and worsens dynamic obstruction. Dobutamine and other beta-agonists are specifically called out: "Beta-agonists, such as dobutamine, increase the gradient across the outflow tract obstruction and should be avoided." - Rosen's Emergency Medicine, p. 1116
3. Vasodilators (ACE inhibitors, ARBs in obstructive HCM, alpha-blockers, dihydropyridine CCBs like amlodipine/nifedipine)
Avoid. Afterload reduction decreases systemic vascular resistance; the LVOT obstruction is sensitive to afterload - reduced afterload paradoxically worsens symptoms as less "back-pressure" holds the outflow tract open.
4. Diuretics (excessive use)
Use with caution / generally avoid. Reducing preload by aggressive diuresis decreases LV filling, making the cavity smaller and increasing obstruction. They are particularly dangerous in obstructive HOCM.
5. Spironolactone
Specifically noted as not efficacious in HOCM and should not be relied upon. - Rosen's Emergency Medicine, p. 1116
Quick Memory Table
| Drug/Class | Why Contraindicated |
|---|---|
| Nitrates | ↓ Preload → ↓ LV volume → ↑ obstruction |
| Digoxin | ↑ Contractility → ↑ obstruction |
| Dobutamine / Dopamine | ↑ Contractility + HR → ↑ obstruction |
| Dihydropyridine CCBs (nifedipine, amlodipine) | Vasodilation → ↓ afterload → ↑ obstruction |
| ACE inhibitors / ARBs | ↓ Afterload → ↑ obstruction |
| Diuretics (aggressive) | ↓ Preload → ↓ LV volume → ↑ obstruction |
What IS used in HOCM
For completeness:
- Beta-blockers (metoprolol) - first line; reduce HR and contractility, improve diastolic filling
- Non-dihydropyridine CCBs (verapamil, diltiazem) - for beta-blocker intolerance; reduce HR
- Disopyramide - negative inotrope; added to reduce resting gradient
- Phenylephrine - vasopressor of choice for hypotension (pure alpha-agonist, no inotropic effect, ↑ afterload helps close the LVOT)
The underlying mechanism for all contraindications is the same: HOCM obstruction is dynamic and worsens with anything that reduces LV size (less preload/afterload) or increases the force of ventricular ejection.
This is a shared conversation. Sign in to Orris to start your own chat.