The optimal use of vasodilators for diagnosis of microvascular angina in the cardiac catheterization laboratory

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Background: Amongst patients with angina and non-obstructive coronary artery disease (NOCAD), those with coronary microvascular dysfunction (CMD) have a poor outcome. CMD is usually diagnosed by assessing flow reserve with an endothelium-independent vasodilator like adenosine but the optimal diagnostic threshold is unclear. Furthermore, the incremental value of testing endothelial function has never been assessed before. We sought to determine what pharmacological thresholds correspond to exercise pathophysiology and myocardial ischemia in patients with CMD.

Methods: Patients with angina and NOCAD underwent simultaneous acquisition of coronary pressure and flow during rest, supine bicycle exercise and pharmacological vasodilatation with adenosine and acetylcholine. Adenosine and acetylcholine coronary flow reserve were calculated as vasodilator / resting coronary blood flow (CFR and AchFR respectively). Coronary wave intensity analysis was used to quantify the proportion of accelerating wave energy; a normal exercise response was defined as an increase in accelerating wave energy
from rest to peak exercise. Ischemia was assessed by quantitative 3-Tesla stress perfusion cardiac magnetic resonance imaging and dichotomously defined by a hyperemic endoepicardial gradient <1.0.
Results: 90 patients were enrolled (58±10 years, 77% female). Area under the curve using receiver-operating characteristic analysis demonstrated optimal CFR and AchFR thresholds for identifying exercise pathophysiology and ischemia as 2.6 and 1.5, with positive and negative predictive values of 91% and 86% respectively. 58% had an abnormal CFR (of which 96% also had an abnormal AchFR). Of those with a normal CFR, 53% had an abnormal AchFR, and 47% had a normal AchFR; ischemia rates were 83%, 63% and 14% respectively.
The optimal CFR and AchFR diagnostic thresholds are 2.6 and 1.5, with high positive and negative predictive values respectively. A normal CFR value should prompt the measurement of AchFR. A stepwise algorithm incorporating both vasodilators can accurately identify an ischemic aetiology in patients with NOCAD.
Original languageEnglish
JournalCirculation: Cardiovascular Interventions
Publication statusAccepted/In press - 5 May 2020


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