Effects of radial artery spasm prophylaxis on intracoronary vasomotor responses during acetylcholine spasm provocation testing

Background: Invasive coronary angiography via the radial approach is commonly performed following radial artery spasm prophylaxis (RASP). It is however unknown, whether RASP influences the results of coronary spasm provocation testing performed after diagnostic angiography. We aimed to investigate the effects of RASP on vasomotor responses during intracoronary acetylcholine (ACh) testing.

Methods: We retrospectively screened 372 consecutive patients (51 % female, mean age 61 ± 11 years) with angina and non-obstructive coronary arteries, who underwent intracoronary provocation with ACh according to a standardized protocol. During testing, dose-dependent clinical discomfort and concomitant ischemic electrocardiographic changes were recorded in addition to visual reductions of epicardial lumen diameters. Of these patients, 156 (42 %) received RASP (i.e. 200 μg nitroglycerin and 2.5 mg verapamil), while no RASP was administered in 216 (58 %) patients. Both groups were compared regarding age, sex, cardiovascular risk factors and ACh-test results.

Results: ACh provocation testing revealed a pathological test result in 71 patients (46 %) with RASP and 103 patients (48 %) without (p = 0.752) [epicardial spasm: in 20 patients (28 %) with RASP and 42 patients (41 %) without (p = 0.120); microvascular spasm: in 51 patients (72 %) with RASP and 61 patients (59 %) without (p = 0.362)]. Overall, RASP did not significantly alter coronary artery vasomotor responses, neither regarding the frequency (p = 0.752) or type of coronary spasm (microvascular vs. epicardial; p = 0.108) nor regarding the ACh dose leading to spasm (p = 0.151).

Conclusions: RASP does not significantly affect coronary vasomotor responses to ACh, suggesting that radial artery spasm prophylaxis can be routinely administered even in patients in whom intracoronary spasm testing is performed.