Left ventricular size determines tissue Doppler-derived longitudinal strain and strain rate

Area of Science:

• Cardiology
• Biomedical Engineering
• Physiology

Background:

• Tissue Doppler imaging provides indices of strain (epsilon) and strain rate (SR) for regional cardiac function assessment.
• The influence of left ventricular (LV) size on these echocardiographic parameters requires further investigation.

Purpose of the Study:

• To determine the extent to which heart size affects cardiac strain (epsilon) and strain rate (SR).

Main Methods:

• Assessed tissue Doppler-derived epsilon and SR, and hemodynamic parameters in 21 anesthetized pigs (12.5-70.0 kg) under controlled heart rates and varying loading conditions.
• Analyzed the correlation between pig weight (as a proxy for heart size) and measured cardiac indices.
• Evaluated the impact of altered afterload and preload on longitudinal epsilon and SR.

Main Results:

• Longitudinal epsilon and SR were significantly higher in smaller hearts compared to larger hearts.
• A hyperbolic correlation was observed between pig weight and both epsilon (r²=0.621) and SR (r²=0.372), both statistically significant (P<0.0001).
• Increased afterload reduced epsilon and SR, while increased preload enhanced these parameters, confirming their load-dependent nature.

Conclusions:

• Longitudinal epsilon and SR decrease with increasing LV dimensions, even with unaltered myocardial contractility.
• Heart size is a significant determinant of measured epsilon and SR.
• Cardiac strain and strain rate are highly sensitive to changes in loading conditions.