Related Experiment Videos
Effect of heart rate on myocardial blood flow in dogs with left ventricular hypertrophy
Insights
In dogs with left ventricular hypertrophy, rapid heart rates during pacing redistribute blood flow away from the heart
Area of Science:
- Cardiovascular Physiology
- Cardiac Hypertrophy Research
- Myocardial Perfusion Studies
Background:
- Previous research suggested inadequate subendocardial perfusion in hypertrophied hearts.
- Left ventricular hypertrophy (LVH) can alter cardiac function and blood supply.
Purpose of the Study:
- To investigate myocardial blood flow patterns during induced tachycardia in dogs with chronic LVH.
- To assess the transmural distribution of blood flow under stress in hypertrophied canine hearts.
Main Methods:
- Created chronic LVH in puppies by banding the ascending aorta.
- Utilized radionuclide-labeled microspheres to measure myocardial blood flow.
- Examined blood flow at varying heart rates (100, 200, 250 bpm) via ventricular pacing.
Main Results:
- Dogs with LVH showed an 87% increase in relative left ventricular mass.
- At 250 bpm, LVH dogs exhibited a significant shift in blood flow from subendocardium to subepicardium (subendo/subepi ratio decreased from 1.03 to 0.83).
- This redistribution was most pronounced in papillary muscle regions and the lateral ventricular wall.
Conclusions:
- Pacing-induced tachycardia causes subendocardial hypoperfusion in canine hearts with LVH.
- LVH significantly alters myocardial blood flow distribution during increased heart rates.
- Findings highlight potential risks of tachycardia in hypertrophic cardiomyopathy.
Abstract:
Because of the previous suggestion that subendocardial perfusion may be inadequate in the hypertrophied heart, this study was carried out to examine the response of transmural myocardial blood flow to pacing induced tachycardia in dogs with chronic left ventricular hypertrophy. Myocardial hypertrophy, produced by banding the ascending aorta of puppies at 5-6 wk of age, resulted in an 87% average increase in relative left ventricular mass compared with the control dogs. Myocardial blood flow was examined during ventricular pacing at heart rates of 100, 200, and 250 beats/min using radionuclide-labeled microspheres. Mean blood flow per unit myocardial mass was similar in the two groups of dogs at a heart rate of 100 beats/min and increased regularly during pacing in both groups of animals. Increasing heart rates did not change the transmural pattern of myocardial blood flow in the normal dogs, but in the animals with left ventricular hypertrophy pacing at 250 beats/min resulted in a significant redistribution of perfusion away from the subendocardium, with the ratio of subendocardial/subepicardial blood flow falling from 1.03 +/- 0.08 at 100 beats/min to 0.83 +/0 0.06 at 250 beats/min (P < 0.01). This redistribution of blood flow away from the subendocardium was especially marked in the regions encompassing the papillary muscles and the intervening left ventricular lateral wall.