Electromechanical left ventricular resynchronisation by coronary artery bypass surgery.

Area of Science:

• Cardiovascular Physiology
• Cardiac Electrophysiology
• Echocardiography

Background:

• Patients with coronary artery disease (CAD) exhibit abnormal electromechanical responses to dobutamine stress, including prolonged QRS duration and increased left ventricular asynchrony.
• These abnormalities impair the normal rise in cardiac output during stress, a critical factor in cardiovascular health.

Purpose of the Study:

• To investigate the impact of coronary artery bypass grafting (CABG) on stress-induced electromechanical abnormalities in patients with CAD.
• To determine how revascularization affects peak cardiac output response following CABG.

Main Methods:

• Doppler echocardiography was used to assess long axis asynchrony, post-ejection shortening, total isovolumic time, and cardiac output in 20 patients before and after CABG.
• Key parameters measured included QRS duration, amplitude and duration of post-ejection shortening, and total isovolumic time.

Main Results:

• Before CABG, dobutamine stress led to QRS duration broadening, increased post-ejection shortening, and elevated total isovolumic time, with a modest rise in cardiac output.
• After CABG, stress resulted in QRS duration shortening, decreased post-ejection shortening, reduced total isovolumic time, and a significantly greater increase in cardiac output.
• Changes in total isovolumic time and post-ejection shortening duration were independent predictors of increased peak cardiac output post-revascularization.

Conclusions:

• Revascularization through CABG effectively resynchronizes left ventricular wall motion by restoring normal electrical activation patterns during stress.
• This resynchronization reduces total isovolumic time and normalizes the peak cardiac output response to stress in patients with CAD.