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Effect of changes in ventricular relaxation on early diastolic coronary blood flow in canine hearts
L J Domalik-Wawrzynski1, W J Powell, L Guerrero
1Cardiac Unit, Massachusetts General Hospital, Boston 02114.
Insights
Impaired left ventricular relaxation reduces early diastolic coronary blood flow. Calcium channel blockers like verapamil can improve this flow during reperfusion after heart attacks.
Area of Science:
- Cardiovascular Physiology
- Cardiac Electrophysiology
Background:
- Coronary blood flow is significantly influenced by the pressure gradient between the aorta and the left ventricle during diastole.
- Left ventricular relaxation critically affects early diastolic pressure, thereby impacting coronary perfusion.
Purpose of the Study:
- To investigate the relationship between impaired left ventricular relaxation and early diastolic coronary blood flow.
- To assess the effects of hypothermia and reperfusion on ventricular relaxation and coronary blood flow.
- To evaluate the efficacy of verapamil in mitigating these effects.
Main Methods:
- Inducing impaired left ventricular relaxation through hypothermia and left anterior descending coronary artery occlusion followed by reperfusion.
- Measuring left ventricular relaxation parameters and early diastolic coronary blood flow.
- Administering verapamil during hypothermia and reperfusion phases.
Main Results:
- Both hypothermia and reperfusion significantly prolonged left ventricular relaxation (p < 0.01).
- Early diastolic coronary blood flow significantly decreased concurrently with impaired relaxation (p < 0.01).
- Verapamil did not affect hemodynamics during hypothermia but significantly blunted the negative effects of reperfusion on relaxation and coronary blood flow (p < 0.002 and p < 0.01, respectively).
Conclusions:
- Impaired left ventricular relaxation adversely affects early diastolic coronary blood flow.
- Calcium channel blockade with verapamil can alleviate the reduction in early diastolic coronary blood flow during reperfusion following myocardial ischemia.
Abstract:
Since the gradient between aortic pressure and left ventricular diastolic pressure is a major determinant of coronary blood flow, a change in left ventricular relaxation by its effect on early diastole could diminish early diastolic coronary flow. Two interventions that resulted in impaired left ventricular relaxation, hypothermia, and reperfusion following a left anterior descending coronary artery occlusion were studied to evaluate whether there were associated changes in coronary blood flow. With both interventions, there was a significant prolongation of left ventricular relaxation (p less than 0.01) accompanied by a significant decrease in early diastolic coronary blood flow (p less than 0.01). Verapamil did not have a significant effect on these hemodynamic changes during hypothermia. However, verapamil significantly blunted the effects of reperfusion following ischemia on ventricular relaxation (p less than 0.002) and early diastolic coronary blood flow (p less than 0.01). Thus, impaired left ventricular relaxation has an adverse impact on early diastolic coronary blood flow, which, under the condition of reperfusion following regional myocardial ischemia, can be alleviated with calcium channel blockade.