Left ventricular effects of nicorandil in comparison with nitroglycerin in chronic conscious dogs

Nicorandil is a new coronary vasodilator possessing beneficial properties. However, its detailed cardiovascular effects, especially on left ventricular (LV) preload, have not yet been fully elucidated. The purpose of this study was to assess the effects of nicorandil on LV hemodynamics in conscious dogs and to examine the mechanisms of its anti-ischemic action. Nine mongrel dogs were instrumented for instantaneous and continuous measurements of LV diameters, and aortic and LV pressures. The effects of nicorandil (0.2 mg/kg, intravenously) were compared with those of nitroglycerin (15 μg/kg, intravenously) in conscious dogs. Mean aortic pressure decreased similarly with both nicorandil and nitroglycerin (−20.1±3.1% vs. 21.6±2.8%, ns). Heart rate was elevated with both drugs. Both nicorandil and nitroglycerin significantly decreased LV systolic pressure to the same extent (−11.3±0.5% vs.−10.5±11.6^, ns). LV max dp/dt was not significantly changed by either drug. Although both nicorandil and nitroglylerin significantly increased fractional shortening, nicorandil had a greater effect on fractional shortening than nitroglycerin (20.0±3.0% vs. 10.2±2.3%, p<0.05). In this study, nicorandil, administered intravenously, had a salutary effect on cardiac function. LV enddiastolic diameter decreased with nicorandil and nitroglycerin (−6.5±1.5% vs.−12.6±2.6%, p<0.01), respectively. In conclusion, nicorandil decreased LV end-diastolic diameter in conscious dogs, indicating a decrease in venous return and preload of the heart. In addition, nicorandil decreased LV afterload to the same extent as nitroglycerin. The decrease in preload and afterload on the heart is thought to be one of the mechanisms of the antiischemic action of nicorandil.