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Coronary and systemic vascular resistance during reperfusion after global myocardial ischemia
S B Digerness1, J W Kirklin, D C Naftel
1Department of Surgery, University of Alabama, Birmingham 35294.
Insights
Coronary blood flow decreases after cardiac surgery despite controlled aortic pressure. Increased coronary vascular resistance and potassium load impact reperfusion success, affecting cardiac recovery.
Area of Science:
- Cardiovascular Surgery
- Cardiac Anesthesia
- Myocardial Ischemia
Background:
- Controlled reperfusion is critical after cardiac surgery involving myocardial ischemia.
- Understanding coronary hemodynamics during reperfusion is essential for optimizing patient outcomes.
Purpose of the Study:
- To investigate coronary blood flow and vascular resistance during controlled aortic root reperfusion following global myocardial ischemia.
- To assess the impact of aortic root pressure, nitroglycerin, and potassium load on coronary hemodynamics and cardiac function recovery.
Main Methods:
- Study involved 16 patients undergoing coronary artery bypass grafting with global myocardial ischemia.
- Coronary blood flow and aortic root pressure were monitored during controlled reperfusion.
- Coronary vascular resistance was calculated, and the effects of nitroglycerin and varying potassium loads were evaluated.
Main Results:
- Coronary blood flow was highest in the initial minutes of reperfusion, declining despite controlled aortic pressure.
- Coronary vascular resistance increased significantly above baseline levels.
- Nitroglycerin transiently decreased resistance; higher potassium loads prolonged the interval to cardiac systole resumption.
Conclusions:
- Controlled aortic root reperfusion exhibits declining coronary flow and rising resistance.
- Potassium management during reperfusion is crucial for timely cardiac function recovery.
- Further strategies are needed to optimize coronary perfusion and reduce resistance post-ischemia.
Abstract:
During controlled aortic root reperfusion after global myocardial ischemia for the performance of coronary artery bypass grafting (N = 16), coronary blood flow was the highest during the first 1 minute to 2 minutes even though the aortic root pressure was controlled at about 40 mm Hg. Even during the period of controlled low pressure, flow began to decline, and the decline continued during the period in which the pressure was controlled at 75 mm Hg. Calculated coronary vascular resistance rose steadily from an initially low value to one well above the normal value for beating hearts. A transient fall in resistance resulted from the administration of a bolus of nitroglycerin into the aortic root. When the initial reperfusate was normokalemic, coronary flow was less and coronary vascular resistance higher during the initial phase of reperfusion. The systemic arterial pressure and resistance fell during the first 1 minute to 3 minutes of reperfusion and in 25% of patients, remained low. The greater the potassium load delivered during the initially hyperkalemic phase, the longer the interval between the beginning of reperfusion and the resumption of cardiac systole.