Related Experiment Video
Updated: Jul 10, 2026

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine
Published on: February 9, 2016
Differential effects of heart rate reduction and beta-blockade on left ventricular relaxation during exercise
Patrice Colin1, Bijan Ghaleh, Luc Hittinger
1Département de Pharmacologie, Institut National de la Santé et de la Recherche Médicale E00.01, Faculté de Médecine Paris Sud, 94276 Le Kremlin-Bicêtre Cedex, France.
Abstract:
Left ventricular (LV) relaxation is crucial for LV function, especially during exercise. We compared the effects of increasing doses of ivabradine, a selective inward hyperpolarization-activated current inhibitor, and atenolol on the rate and extent of LV relaxation (best fit method: time constant tau(BF), pressure asymptote P(BF)) at rest and during exercise. Eight dogs were chronically instrumented to measure LV pressure and LV wall stresses. During exercise under saline, heart rate increased from 108 +/- 5 to 220 +/- 6 beats/min and tau(BF) was significantly reduced from 22 +/- 1 to 14 +/- 2 ms. At rest, atenolol but not ivabradine increased tau(BF). For similar heart rate reductions during exercise, atenolol impeded the shortening of tau(BF) (23 +/- 2 ms) whereas ivabradine had no effect (15 +/- 2 ms). The extent of the relaxation process (P(BF)) at peak exercise was increased by ivabradine, and to a greater extent by atenolol, compared with saline. Thus, for a similar reduction in heart rate at rest and during exercise, ivabradine, in contrast with atenolol, does not exert any negative lusitropic effect.
Related Concept Videos
Factors Influencing Heart Rate
Let us explore the significant factors affecting heart rate, including age, body temperature, posture, acute pain, chemical influences,...
Adrenergic Antagonists: Pharmacological Actions of β-Receptor Blockers
Antihypertensive Drugs: Action of β1 Blockers
Antihypertensive Drugs: Types of β-Blockers
Heart Failure Drugs: β-Blockers
Cardiac Output I:Effect of Heart Rate on Cardiac Output
Cardiac output (CO) refers to the total amount of blood ejected by one of the ventricles in liters per minute (L/min). In a resting adult, CO ranges from 5 to 6 L/min, adjusting according to the body's metabolic requirements.
Effect of Heart Rate on Cardiac Output
Cardiac output adapts to metabolic demands during stress, physical activity, or illness. The autonomic nervous system regulates heart rate via the sinoatrial node. The parasympathetic nervous system decreases heart rate...

