P <0.05 vs. Control.P <0.05 vs. Drug. The first Pvalue indicates LL-ES vs.control, and the second P value indicates LL-ES vs. Drug. VERP=ventricular effective refractory period; LVEDV=left ventricular end-diastolic volume; LVESV=left ventricular end-systolic volume; LVSV=left ventricular stroke volume; LVEF=left ventricular ejection fraction.