Effects of nitric oxide synthase inhibition on Basal function and the force-frequency relationship in the normal and failing human heart in vivo
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View abstract on PubMed
Summary
This summary is machine-generated.Nitric oxide (NO) has a minor positive effect on normal heart contractility, but this effect is lost in heart failure. NO does not impact the force-frequency relationship in vivo for either healthy or failing hearts.
Area Of Science
- Cardiology
- Cardiovascular Physiology
Background
- Nitric oxide (NO) influences cardiac function and contractility.
- In vitro studies suggest NO modulates the myocardial force-frequency relationship.
- Heart failure is associated with depressed contractility and a blunted force-frequency relationship, potentially due to increased NO production.
Purpose Of The Study
- To investigate the in vivo effects of nitric oxide synthase inhibition on left ventricular (LV) function and the force-frequency relationship in humans.
- To compare these effects in patients with dilated cardiomyopathy and healthy controls.
Main Methods
- Intracoronary administration of N(G)-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase inhibitor.
- Assessment of basal LV function (using LV dP/dt(max)) and response to incremental atrial pacing.
- Comparison between 11 patients with dilated cardiomyopathy and 7 healthy controls.
Main Results
- In controls, L-NMMA reduced basal LV dP/dt(max) but did not affect heart rate or pressures. Pacing-induced increases in LV dP/dt(max) were not altered by L-NMMA.
- In dilated cardiomyopathy patients, L-NMMA had no effect on baseline LV dP/dt(max).
- The blunted pacing-induced increase in LV dP/dt(max) in heart failure patients remained unaltered by L-NMMA.
Conclusions
- Endogenous NO exerts a small baseline positive inotropic effect in the normal human heart, which is absent in heart failure.
- Nitric oxide does not significantly influence the force-frequency relationship in vivo in normal or failing human hearts.
- Further investigation is needed to determine if these findings apply to patients with more severe heart failure.
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