Tachycardia exacerbates abnormal left ventricular-arterial coupling in heart failure

Area of Science:

• Cardiovascular Physiology
• Heart Failure Pathophysiology
• Biomechanical Coupling

Background:

• Left ventricular (LV) stroke work and mechanical efficiency are critically dependent on the coupling between the LV and the arterial system.
• The response of this LV-arterial coupling to increased heart rate (tachycardia) may be significantly altered in the context of congestive heart failure (CHF).

Purpose of the Study:

• To investigate the impact of elevated heart rate on left ventricular (LV)-arterial coupling and LV mechanical efficiency.
• To compare these effects in healthy states versus states of congestive heart failure (CHF).

Main Methods:

• Utilized six instrumented dogs, comparing measurements before and after pacing-induced CHF.
• Quantified LV-arterial coupling using the ratio of end-systolic elastance (Ees) to arterial elastance (Ea).
• Assessed mechanical efficiency as the ratio of stroke work (SW) to total pressure-volume area (PVA).

Main Results:

• In healthy states, increased heart rate maintained optimal LV-arterial coupling (Ees/Ea) and mechanical efficiency (SW/PVA).
• Following CHF induction, resting Ees decreased, leading to reduced baseline Ees/Ea and SW/PVA.
• In CHF, tachycardia further decreased Ees/Ea and SW/PVA, indicating exacerbated suboptimal coupling and reduced efficiency.

Conclusions:

• Normal physiological increases in heart rate maintain optimal left ventricular-arterial coupling and efficiency.
• Congestive heart failure significantly disrupts this coupling, with tachycardia worsening the suboptimal state.
• Tachycardia in heart failure reduces the efficiency of generating stroke work, highlighting a critical derangement in cardiovascular function.