Non-invasively assessed coronary flow reserve stratifies outcomes in patients with intermediate left main coronary artery stenosis

Abstract

Background: Correct assessment of the significance of left main coronary artery (LMCA) stenosis on the basis of clinical and angiographic information alone often cannot be done reliably and requires assessment of functional significance of lesions observed on coronary angiography. Aim: The aim of this study was to determine the prognostic value of noninvasively measured coronary flow reserve (CFR) in patients with angiographically assessed intermediate or equivocal LMCA stenosis during long-term follow up. Methods: Hundred patients (59±9 years, 80 male) in whom LMCA was assessed by coronary angiography to be ≤50% diameter stenosis; without significant left anterior descending artery stenosis (LAD), were included in this prospective follow-up study. All patients underwent transthoracic Doppler echocardiography measurements of CFR in medial part of LAD after intravenous adenosine administration to assess functional significance of LMCA stenosis. CFR values were calculated as the ratio between hyperemic maximal flow velocity and resting flow velocity. Patients were followed for the mean period of 27±10 months for the occurrence of composite end point including cardiovascular death, myocardial infarction, hospitalization due to unstable angina and clinically guided revascularization. Results: 91 patient completed follow-up. Events occurred in 16. Mean CFR value of 1.80±0.44 for patients having events was significantly lower, compared to those who were free of events where mean CFR value was 2.4±0.44 (p<0.001). During the follow up period (range 1-50 months), 69 patients (95, 8%) with CFR ≥2 remained free of death and major adverse events vs. 6 patients (31,6%) with CFR <2, p<0.001. By Kaplan-Meier method, at 24 months the percent estimated survival free from cardiac related events was 95±3% in patients with CFR ≥2 and 45±11% in patients with CFR <2, p<0.001. Picture Conclusion: In patients with intermediate or equivocal left main coronary artery disease, CFR ≥2 is associated with low event rate and excellent survival. According to our results CFR measured by transthoracic Doppler echocardiography provides reliable and precise, yet non-invasive tool for the assessment of functional severity of LMCA disease that carries significant prognostic information in long-term follow-up.