Effect of dynamic myocardial dyssynchrony on mitral regurgitation during supine bicycle exercise stress...

Area of Science:

• Cardiology
• Echocardiography
• Heart Failure Research

Background:

• Cardiac resynchronization therapy (CRT) selection relies on resting ECG and echocardiography.
• The impact of physical exertion on myocardial dyssynchrony in heart failure (HF) is not fully understood.
• Dynamic assessment may reveal novel insights into HF pathophysiology.

Purpose of the Study:

• To investigate if dynamic left ventricular (LV) dyssynchrony during physical effort is a determinant of dynamic mitral regurgitation.
• To assess LV dyssynchrony using Doppler myocardial imaging (DMI) in dilated cardiomyopathy patients with narrow QRS.
• To correlate exercise-induced dyssynchrony with mitral regurgitation severity and exercise capacity.

Main Methods:

• Sixty patients with idiopathic dilated cardiomyopathy and narrow QRS (<120 ms) underwent DMI, exercise stress echocardiography, and cardiopulmonary exercise testing.
• LV synchronicity was assessed at rest and peak exercise using time intervals (Ts) and standard deviation of Ts (Ts-SD-12).
• Mitral regurgitation severity was quantified by effective regurgitant orifice (ERO).

Main Results:

• At peak exercise, 58.3% of patients showed significant electromechanical delay, and 78.3% had increased mitral regurgitation.
• Changes in Ts-SD-12 positively correlated with changes in mitral valve ERO (P < 0.0001).
• Increased LV dyssynchrony during exercise was independently associated with reduced LV stroke volume and peak VO2.

Conclusions:

• Colour DMI effectively assesses LV wall motion delay in HF patients with narrow QRS during stress.
• Exercise-induced LV dyssynchrony significantly correlates with increased mitral regurgitation severity.
• Dynamic dyssynchrony during exertion is a key factor in impaired LV stroke volume and reduced exercise capacity in these patients.