Should the Right Coronary Artery Be Routinely Assessed During Provocative Spasm Testing?

Abstract

Background/Objectives: The diagnosis of coronary artery spasm (CAS) frequently requires invasive provocation testing, typically utilising acetylcholine (ACh). Although the left coronary artery (LCA) is routinely assessed as a part of the testing protocol, assessment of the right coronary artery (RCA) is often avoided since it requires the insertion of a temporary pacing wire. We sought to compare the prevalence of inducible CAS in the LCA and RCA, among patients with CAS undergoing multivessel spasm provocation testing with ACh. Methods: A local multi-institutional ANOCA (angina and non-obstructive coronary arteries) database was analysed, which included 316 patients with angina and suspected CAS who underwent provocation testing (single vessel n = 266, multivessel n = 50) with incremental bolus doses of intracoronary ACh (25, 50, 100 μg in the LCA; 25, 50 μg in the RCA). CAS was defined as >90% constriction of the epicardial coronary artery as assessed visually on coronary angiography. Results: In the 50 patients (55 ± 10 years, 77% female) who underwent multivessel spasm provocation testing, CAS was induced in 20 patients (40%), with ACh provoking CAS only in the LCA system in 45%, only in the RCA system in 35%, and both LCA/RCA in 20%. Conclusions: These findings demonstrate that assessing only the LCA may miss up to one-third of CAS cases. Therefore, it is essential to routinely evaluate the RCA, particularly when no inducible spasm is detected in the LCA.

Keywords: ANOCA; angina with non-obstructive coronary arteries; coronary artery spasm; functional coronary angiography; multivessel testing; provocative spasm testing.

Figure 1

ACh-induced Coronary Artery Spasm in patients Undergoing Multivessel Testing (n = 20). Multivessel provocative testing was positive in 20 patients, 20% of which had spasm in both the left and right coronary arteries, 45% in the left coronary artery, and 35% in the right coronary artery alone. LCA: Left Coronary Artery, RCA: Right Coronary Artery.

Figure 2

The workflow of a recommended provocative spasm testing protocol with intracoronary acetylcholine, at a minimum employing a multivessel testing approach in cases where single-vessel testing concludes a negative result. Following diagnostic invasive coronary angiography, whereby the patient is confirmed to have non-obstructive coronary arteries (atherosclerotic stenosis observed to be ≤50% vessel diameter, or a Fractional Flow Reserve ≥ 0.8 in any major epicardial coronary artery), provocative testing is initiated in the left coronary artery (LCA). An initial baseline image is used as a reference image before proceeding with an intracoronary acetylcholine (ACh) bolus dose of 25 μg over 20 s. A repeat angiogram image is taken to observe vasospasm, where <90% vasoconstriction is considered negative. Simultaneous monitoring of a 12-lead ECG for ischemic changes and patient-reported reproducible chest pain symptoms is conducted. The doses progress incrementally when negative (i.e., an increase of the dose to 50 μg when 25 μg does not result in vasospasm, and 100 μg when 50 μg does not result in vasospasm), * denotes the allowing of a 5 min interval between each dose before proceeding to the next step as necessary. LCA testing is concluded at a maximum dose of 100 μg or at 25 μg or 50 μg where occlusive or sub-occlusive vasospasm (>90% epicardial constriction) is induced (as in Image A). If LCA testing produces a negative result (as in Image B), RCA testing commences, demonstrated by the dashed arrow, following the insertion of a temporary pacing wire with the threshold set to 50 bpm, following the same pattern of progressive doses with negative results at 25 μg and 50 μg. RCA testing is concluded at a maximum dose of 50 μg, or at 25 μg where occlusive or sub-occlusive spasm is observed (as in Image C). If at the conclusion of this testing protocol RCA spasm produces a negative result (as in Image D), the patient is considered negative for coronary artery spasm. This concludes the administration of intracoronary ACh bolus doses, and is followed by a bolus dose of 150 μg intracoronary GTN to evaluate endothelium-independent coronary artery function, and/or to relieve ACh-induced coronary artery spasm and coinciding angina symptoms.