Tissue Doppler imaging differentiates physiological from pathological pressure-overload left ventricular hypertrophy...

Area of Science:

• Cardiology
• Echocardiography
• Physiology

Background:

• Myocardial velocity gradient (MVG) is a novel index of regional myocardial function.
• It is derived from endocardial and epicardial velocities using tissue Doppler imaging (TDI).
• MVG may differentiate physiological from pathological left ventricular hypertrophy (LVH) and track early changes toward heart failure.

Purpose of the Study:

• To compare MVG in the left ventricular posterior wall of normal rats with those exhibiting physiological (exercise) or pathological (pressure-overload) LVH.
• To assess the utility of MVG in distinguishing between types of LVH and its response to interventions.

Main Methods:

• Wistar rats were divided into sedentary, exercise (swimming), and abdominal aortic banding (2-month and 9-month) groups.
• Echocardiography, including TDI for MVG measurement, and conventional systolic function parameters were assessed.
• Aortic debanding was performed at 2 and 9 months post-banding.

Main Results:

• Exercise and 2-month banding induced significant LVH comparable to sedentary controls.
• Conventional systolic function parameters remained unchanged after 2-month banding.
• Systolic and diastolic MVG were significantly reduced in aortic-banded rats compared to sedentary and exercise groups.
• MVG recovered fully after 2-month debanding but remained depressed after 9-month debanding.

Conclusions:

• TDI-derived myocardial contraction and relaxation are impaired in pressure-overload LVH, but not in exercise-induced LVH.
• TDI is more sensitive than conventional echocardiography for detecting myocardial dysfunction in pressure-overload LVH.
• MVG can predict early recovery of myocardial function following normalization of loading conditions.