Myocardial flow reserve in experimental cardiac hypertrophy

Area of Science:

• Cardiovascular Physiology
• Cardiac Metabolism
• Heart Failure Research

Background:

• Left ventricular (LV) hypertrophy is a common cardiac response to pressure overload.
• Understanding the impact of hypertrophy on myocardial blood flow (MBF) is crucial for predicting heart function.
• Early detection of circulatory dysfunction in hypertrophy can guide therapeutic interventions.

Purpose of the Study:

• To investigate the changes in myocardial blood flow (MBF) and flow reserve in a canine model of pressure-induced LV hypertrophy.
• To assess the impact of varying degrees of hypertrophy and coronary stenosis on MBF distribution.
• To determine if MBF impairment precedes the onset of overt heart failure symptoms.

Main Methods:

• Induction of LV hypertrophy in foxhounds via aortic banding.
• Measurement of resting MBF and myocardial flow reserve at 3 months and 1 year post-banding.
• Evaluation of MBF response to acute coronary stenosis (60-70%) in control and hypertrophied hearts.

Main Results:

• Early hypertrophy (3 months) showed no significant difference in resting MBF or flow reserve compared to controls.
• Advanced hypertrophy (1 year) demonstrated a significant decrease in myocardial flow reserve.
• Coronary stenosis caused a greater reduction in post-stenotic MBF in extensively hypertrophied hearts, especially in the subendocardium.

Conclusions:

• Myocardial blood flow impairment occurs in pressure-induced LV hypertrophy even before clinical signs of heart failure.
• Reduced flow reserve is a key feature of advanced hypertrophy and is exacerbated by coronary stenosis.
• These findings highlight the vulnerability of hypertrophied hearts to ischemia and suggest broader implications beyond specific hypertension types.