Key Points
- To determine how congestive heart failure impacts coronary blood flow and myocardial oxygen consumption during graded exercise.
- Measured coronary blood flow and metabolic parameters in chronically instrumented dogs at rest and during two stages of treadmill exercise under control conditions (n=10).
- Repeated measurements after inducing congestive heart failure via 3 weeks of rapid ventricular pacing (n=9).
- Resting myocardial blood flow decreased by 25% after the development of congestive heart failure (P<0.05).
- Coronary blood flow and myocardial oxygen consumption increased during stage 1 exercise in heart failure but plateaued during stage 2 despite rising rate-pressure product.
- Myocardial lactate consumption persisted without decreases in coronary venous pH or additional oxygen extraction during stage 2 exercise, demonstrating an absence of myocardial ischemia.
Structured PICO
Does congestive heart failure impair the increase in coronary blood flow and myocardial oxygen consumption during exercise in a canine model?
PPopulation19 chronically instrumented dogs (n=10 control, n=9 with congestive heart failure produced by 3 weeks of rapid ventricular pacing)
IInterventionCongestive heart failure (CHF) state induced by 3 weeks of rapid ventricular pacing, evaluated during 2 stages of graded treadmill exercise
CComparatorNormal control conditions (n=10) evaluated during the same graded treadmill exercise
OOutcomeMyocardial oxygen consumption and coronary blood flow at rest and during exercisesurrogate
In a canine model of heart failure, the failure of coronary blood flow to increase during higher levels of exercise is driven by reduced myocardial oxygen demand rather than inadequate oxygen supply.