Role of alpha-adrenergic coronary tone in exercise-induced angina pectoris

To provide more insight into the role of alpha-adrenergic coronary tone in exercise-induced angina, 9 patients with chronic stable angina underwent after coronary angiography a symptom-limited supine exercise test on a cyclo-ergometer. After recovery, phentolamine was directly injected into the most diseased vessel (2 mg in 5 minutes), and immediately thereafter the same exercise (identical workloads and exercise duration) was repeated. During exercise 1, heart rate (HR), mean blood pressure and cardiac index increased 51% (p less than 0.001), 23% (p less than 0.01) and 33% (p less than 0.01), respectively, and pulmonary artery wedge pressure (PA wedge) increased from 9 +/- 1 to 26 +/- 2 mm Hg (p less than 0.001). After intracoronary injection of phentolamine, control values (including PA wedge) at rest did not change significantly. During exercise 2, HR, mean blood pressure and cardiac index increased in a similar way--50% (p less than 0.001), 25% (p less than 0.01) and 40% (p less than 0.01), respectively; however the increase in PA wedge was less (p less than 0.01). ST-segment depression at the end of exercise 2 was smaller for identical workloads and double products: 1.5 +/- 0.3 mm vs 2.5 +/- 0.3 mm (p less than 0.01). ST/HR slope in exercise 2 also decreased 51% (p less than 0.01). These results show a less severe ischemic response after intracoronary alpha blockade and argue for an improvement in coronary blood supply.