Direct cardiac versus systemic effects of inorganic nitrite on human left ventricular function: Effect of inorganic nitrite on LV function

Background
Inorganic nitrite is a source of nitric oxide (NO) and is considered a potential therapy in settings where endogenous NO bioactivity is reduced and left ventricular (LV) function impaired. However, the effects of nitrite on human cardiac contractile function, and the extent to which these are direct or indirect, are unclear.
Methods and Results
We studied 40 patients undergoing diagnostic cardiac catheterisation who had normal LV systolic function and were not found to have obstructive coronary disease. They received either an intracoronary sodium nitrite infusion (8.7-26 mol/min, n=20) or an intravenous sodium nitrite infusion (50 g/kg/min, n=20). LV pressure-volume relations were recorded. The primary end point was LV end-diastolic pressure (LVEDP). Secondary end points included indices of LV systolic and diastolic function. Intracoronary nitrite infusion induced a significant reduction in LVEDP, LV end-diastolic pressure-volume relationship (EDPVR) and the time to LV end-systole (LVEST) but had no significant effect on LV systolic function or systemic haemodynamics. Intravenous nitrite infusion induced greater effects, with significant decreases in LVEDP, EDPVR, LVEST, LV dP/dtmin, tau, and mean arterial pressure.
Conclusions
Inorganic nitrite has modest direct effects on human LV diastolic function, independent of LV loading conditions and without affecting LV systolic properties. However, the systemic administration of nitrite has larger effects on LV diastolic function which are related to reduction in both preload and afterload. These contractile effects of inorganic nitrite may indicate a favourable profile for conditions characterized by LV diastolic dysfunction.