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Nitrates versus angiotensin-converting enzyme inhibitors for congestive heart failure
1University of Minnesota Medical School, Minneapolis 5455.
Insights
Nitrates and ACE inhibitors offer benefits for heart failure patients, improving hemodynamics and potentially survival. Hydralazine/nitrate combinations may offer a slight edge in exercise capacity compared to ACE inhibitors.
Area of Science:
- Cardiology
- Pharmacology
Background:
- Heart failure management involves optimizing hemodynamic function, symptom relief, and survival.
- Nitrates and angiotensin-converting enzyme (ACE) inhibitors are key therapeutic classes for heart failure.
Purpose of the Study:
- To compare the efficacy of nitrates versus ACE inhibitors in heart failure.
- To elucidate the mechanisms of action and therapeutic benefits of these drug classes.
Main Methods:
- Evaluation of hemodynamic parameters including stroke volume and left ventricular filling pressure.
- Assessment of arterial compliance using a modified Windkessel model.
- Review of multicenter trials assessing exercise tolerance and long-term survival benefits.
Main Results:
- Both nitrates/hydralazine and ACE inhibitors improve hemodynamics, with nitrates/hydralazine showing a larger increase in stroke volume.
- Hydralazine/nitrate therapy demonstrated a slightly superior effect on exercise capacity compared to ACE inhibitors.
- Both drug classes may mitigate adverse myocardial remodeling, potentially contributing to improved long-term survival.
Conclusions:
- Nitrates and ACE inhibitors offer distinct yet overlapping benefits in heart failure treatment.
- Long-term benefits likely stem from their combined effects on cardiac remodeling and vascular smooth muscle relaxation.
- Hydralazine/nitrate combinations may provide additional advantages in exercise tolerance for heart failure patients.
Abstract:
The efficacy of nitrates versus that of angiotensin-converting enzyme (ACE) inhibitors in heart failure may be evaluated based on 3 treatment aims: hemodynamic improvement, symptom relief, and survival benefit. Nitrates used in conjunction with hydralazine produce a relatively large increase in stroke volume and a prominent reduction of left ventricular filling pressure, whereas ACE inhibitors produce a comparatively modest increase in stroke volume with a prominent reduction in filling pressure. The effect of these drugs on arterial compliance has been evaluated using a modified Windkessel model of the circulation to define their mechanism of action. Nitrates appear to affect the large arteries and arterial bed as well as the venous circulation. Intermediate-term response to therapy is often evaluated by changes in exercise tolerance. A review of multicenter trials reveals that, although both ACE inhibitors and hydralazine/nitrate have favorable hemodynamic actions, the effect of hydralazine/nitrate on exercise capacity appears to be slightly better. ACE inhibitors and nitrates both may reduce dysfunctional myocardial remodeling, as evaluated in a canine model of chronic left ventricular dysfunction. The increase in the ejection fraction by these drugs and the decrease of plasma norepinephrine levels by ACE inhibitors may contribute to improved long-term survival. It appears, therefore, that the long-term benefits of nitrates and ACE inhibitors in heart failure probably relate to their ability both to affect cardiac remodelling and to relax vascular smooth muscle.