Instantaneous wave-free ratio for guiding treatment of nonculprit lesions in patients with acute coronary syndrome: A retrospective study.

BACKGROUND: The aim of this study was to analyze the feasibility of a physiological coronary evaluation with the instantaneous wave-free ratio (iFR) of nonculprit lesions in patients with acute coronary syndrome (ACS) successfully revascularized. METHODS: A multicenter registry including patients of four high-volume PCI centers with ACS and underwent successful revascularization of the culprit vessel and had other nonculprit lesions that were physiologically evaluated with the iFR between January 2017 and December 2019. The primary endpoint was a composite of cardiac death, nonfatal myocardial infarction, probable or definitive stent thrombosis and new revascularization (MACEs). RESULTS: A total of 356 patients with 472 nonculprit lesions were included. The mean age was 66 ± 11 years. The clinical presentation was ACS without persistent ST-segment elevation (NSTE-ACS) in 235 patients (66%) and ST-segment elevation myocardial infarction (STEMI) in 121 patients (34%). After a median follow-up period of 21 (14-30) months, the primary endpoint occurred in 32 patients (9%). There were no differences in outcomes regarding clinical presentation (NSTEMI vs. NSTE-ACS, 9.1 vs. 8.9%, padj  = 0.570) or iFR induced treatment strategy (patients with all lesions revascularized vs. patients with at least one lesion with an iFR > 0.89 deferred for revascularization, 10.5 vs. 8.4%, padj  = 0.476). CONCLUSIONS: The use of the iFR to guide percutaneous coronary intervention decision making in nonculprit lesions seems to be feasible, with an acceptable percentage of MACEs at the mid-term follow-up. Patients with deferred revascularization of lesions without physiological significance and patients undergoing complete revascularization had a similar risk of MACEs.

Coronary microvascular dysfunction assessed by continuous intracoronary thermodilution: A comparative study with index of microvascular resistance.

BACKGROUND: This study aimed to assess the correlation between the standard of care, the index of microvascular resistance (IMR) versus the novel microvascular resistance (Rmicro) and to determine the pathologic cut-off value in a selected population with suspected coronary microvascular dysfunction (CMD). METHODS: One-hundred and twenty patients with high clinical suspicion of CMD due to ischemic symptoms in the absence of significant epicardial coronary lesions were prospectively included. Following a standardized systematic protocol, coronary flow reserve, IMR, fractional flow reserve, Q and Rmicro were measured in the left anterior descending coronary artery using a temperature/pressure sensor-tipped guidewire and a dedicated infusion catheter. RESULTS: There was a high prevalence of CMD with 50 (42%) patients showing an IMR ≥ 25. Median IMR was 23 [IQR: 14-34] and median Rmicro was 464 Woods Units (WU) [IQR: 354-636WU]. ROC analyses identified 500 WU as the optimal Rmicro cut-off to identify patients with an IMR ≥ 25, with an area under the ROC curve (C statistic) of 0.83 (95% CI: 0.74 to 0.89, p < 0.0001). CONCLUSIONS: Rmicro derived from continuous intracoronary thermodilution is an accurate index to measure microvascular resistances enabling the invasive diagnostic of CMD.

Continuous Thermodilution Method to Assess Coronary Flow Reserve.

Coronary flow reserve (CFR) is a well-validated flow-based physiological parameter that has shown value in clinical risk stratification. CFR can be invasively assessed, classically by Doppler and, more recently, by thermodilution with saline boluses (CFRthermo-bolus). Alternatively, continuous thermodilution is a novel operator-independent, highly-reproducible technique to invasively quantify maximum absolute coronary flow (AF). This study aimed to assess the feasibility of this method to quantify resting AF and to determine CFR (CFRThermo-infusion) as compared with CFRthermo-bolus. Sixty-two consecutive patients with suspicion of coronary disease and absence of significant epicardial lesions were prospectively investigated. AF at maximal hyperemia (20 mL/min) and at lower infusion rates (6-8-10-12 mL/min) were systematically measured using a dedicated catheter and a temperature/pressure guidewire. The absence of baseline Pd/Pa decrease at 6 (0.15 ± 0.2%), 8 (0.17 ± 0.18%) and 10 mL/min (0.2 ± 0.12%) demonstrated absence of hyperemia at ≤10 mL/min (all p = NS). However, at 12 mL/min hyperemia was confirmed by a significant decrease in Pd/Pa (1.3 ± 1.5%, p <0.01) and increase in AF from 10 mL/min to 12 mL/min (31.4 ± 28.1 mL, p <0.05). All curve tracings at 10 mL/min (129/129, 100%) were adequate versus only (7/15, 53%) and (15/18, 17%) at 6 mL/min, and 8 mL/min, respectively, and this infusion-rate was considered to determine resting-AF. CFRThermo-infusion was determined as the ratio of hyperemic-AF (20 mL/min) by resting-AF (10 mL/min). Mean CFRThermo-infusion was 2.56 ± 0.9 and CFRthermo-bolus 2.49 ± 1. Both parameters showed a good correlation (r = 0.76; p <0.001) and intraclass agreement (ICC = 0.76; p <0.001).The continuous thermodilution method enables to quantify resting-AF providing a novel clinical tool to determine CRF. CFRThermo-infusion shows a good correlation with CFRthermo-bolus..