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

To provide more insight into the role of α-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 < 23% (p < 0.01) and 33% (p < 0.01), respectively, and pulmonary artery wedge pressure (PA wedge) increased from 9 ± 1 to 26 ± 2 mm Hg (p < 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 < 0.001), 25% (p < 0.01) and 40% (p < 0.01), respectively; however the increase in PA wedge was less (p < 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 < 0.01). ST/HR slope in exercise 2 also decreased 51% (p < 0.01). These results show a less severe ischemic response after intracoronary α blockade and argue for an improvement in coronary blood supply.