Contributions of heart rate and contractility to myocardial oxygen balance during exercise

Citations Over TimeTop 10% of 2003 papers

Abstract

The respective contributions of heart rate (HR) reduction and left ventricular (LV) negative inotropy to the effects of antianginal drugs are debated. Accordingly, eight instrumented dogs were investigated during exercise at spontaneous and paced HR (250 beats/min) after administration of either saline, atenolol, or ivabradine (selective pacemaker current channel blocker). During exercise, atenolol and ivabradine (both 1 mg/kg iv) similarly reduced HR (-30% from 222 +/- 5 beats/min), and LV mean ejection wall stress was not altered. LV dP/dt(max) was reduced by atenolol but not ivabradine. Diastolic time (DT) was increased by atenolol versus saline (195 +/- 6 vs. 123 +/- 4 ms, respectively) and to a greater extent by ivabradine (233 +/- 11 ms). Myocardial oxygen consumption (MVo(2)) was lower under ivabradine and atenolol versus saline (6.7 +/- 0.6 and 4.7 +/- 0.4 vs. 8.1 +/- 0.6 ml/min, respectively, P < 0.05). Under pacing, DT and MVo(2) were similar between ivabradine and saline but significantly reduced with atenolol. Thus HR reduction and negative inotropy equally contribute to the reduction in MVo(2) during exercise in the normal heart. The negative inotropy limits the increase in DT afforded by HR reduction.

Related Papers

• → If Inhibition with Ivabradine(2008)137 cited
• → Differential effects of heart rate reduction and β-blockade on left ventricular relaxation during exercise(2002)105 cited
• → Effect of Ivabradine vs Atenolol on Heart Rate and Effort Tolerance in Patients With Mild to Moderate Mitral Stenosis and Normal Sinus Rhythm(2012)21 cited
• → Effects of ivabradine and atenolol on heart rate and heart rate variability in healthy cats over a 24 h period: A pilot study(2022)5 cited
• → Central pressure and arterial stiffness in patients with stable angina and arterial hypertension without left ventricular systolic dysfunction: effects of atenolol and ivabradine(2015)2 cited