Impaired forearm vasodilator reserve in patients with microvascular angina. Evidence of a generalized disorder of vascular function?

In previous work, we described a group of patients with angina-like chest pain and normal coronary arteries. These patients had impaired coronary vasodilator responses to the stress of rapid atrial pacing and to the administration of dipyridamole, a potent vasodilator of coronary arterioles. This abnormality appears to be localized to the prearteriolar microvascular bed. To determine whether these patients have a more generalized abnormality of vasodilator reserve, we used mercury-in-Silastic strain-gauge plethysmography to compare their hyperemic responses to forearm ischemia with those of normal controls. After 10 minutes of ischemia, peak forearm flow was 39.9 +/- 5.0 ml per minute per deciliter in the controls [corrected] and 31.7 +/- 10.5 in the patients [corrected] (21 percent reduction; 95 percent confidence interval, 4 percent to 37 percent). Flow responses were also significantly reduced after three and five minutes of ischemia. Correspondingly, the vascular resistance after ischemia was also consistently higher in the patients with microvascular angina. The degree of vasodilator impairment in the peripheral circulation correlated well with the degree of vasodilator impairment in the coronary circulation (r = 0.74; P less than 0.004). Thus, patients with microvascular angina appear to have an impairment of vasodilator reserve that affects not only their coronary circulation but also their peripheral arterial bed.