CORONARY FLOW AT REST AND CLINICAL OUTCOMES IN DILATED CARDIOMYOPATHY

Abstract

Abstract Background/Objectives Reduced coronary flow reserve (CFR) was described in dilated cardiomyopathy (DCM). To match increased metabolic demand from the myocardium, resting coronary flow (rCF) increases with CFR consumption. Whether an increased rCF causing a reduction of CFR is associated with worse clinical outcomes in DCM remains debated. RCF is inversely correlated to the resting mean transit time (mtt) required for blood to pass through the coronary artery (rCF=1/mtt). A reliable surrogate of mtt is the ratio n frames/frame rate where n frames are the number of frames required for the dye to reach standard distal landmarks of coronary arteries during invasive coronary angiography (ICA) and frame rate is the frame rate acquisition. We aim to assess the prognostic role of rCF evaluated at the ICA performed as standard clinical practice at the time of diagnosis at long–term follow–up in DCM. Methods This is a retrospective analysis of a prospective cohort of patients with idiopathic DCM under medical management enrolled in the Verona Heart Failure registry between 01/2012 and 12/2022. RCF was evaluated at the ICA performed at the time of diagnosis as 1/(n frames/frame rate). The primary endpoint was a composite of cardiovascular death, rehospitalization for heart failure, resuscitated cardiac arrest, hemodynamically unstable ventricular arrhythmias, implanted cardiac defibrillator intervention and cardiac transplantation due to advanced heart failure. Results 110 patients were enrolled in the final cohort. 15 patients (13.6%) suffered the primary endpoint at a median follow–up time of 42 months (IQR 18–71). At the ROC curve analysis rCF predicts the primary endpoint at a cut–off of 2.32 with an AUC of 0.728 (0.599–0.858, p=0.005) with sensitivity, specificity, negative and positive predictive value of 73.3%, 69.5%, 94.3% and 27.5% respectively. Patients suffering the primary endpoint tended to be older (66 years [60–74] vs 59 years [51–69], p=0.060) and were characterized by an increased rCF (3 [1.87–3.75] vs 1.87 [1.36–2.5]). Patients with rCF<2.32 suffered the primary endpoint more frequently when compared to those with rCF≥2.32 (27.5% vs 5.7%, log rank test p=0.007). Conclusions Increased rCF leading to a consumption of CFR is associated with worse clinical outcomes at long term follow–up in idiopathic DCM. Whether coronary microvascular dysfunction can play a prognostic role in this setting remains to be explored by proper prospective studies.