Abstract Body (Do not enter title and authors here): Introduction: Patients with angina but unobstructed coronaries (ANOCA) represent a diagnostic and therapeutic challenge. Current Guidelines recommend invasive testing using acetylcholine and adenosine for evaluation of coronary vasomotor disorders. However, there is a broad variability among the different measurement techniques.
Purpose: To assess the differences of bolus thermodilution versus Doppler flow velocity derived indexes of coronary physiology using intracoronary adenosine in patients with ANOCA.
Methods: A total of 162 patients (61.1% women, mean age 63±28 years) with ANOCA (no epicardial stenosis >50%, FFR >0.80) were enrolled between 2018 and 2023. All patients underwent wire-based assessment of coronary flow reserve (CFR) and microvascular resistance (MR) using adenosine in the left anterior descending artery. The bolus thermodilution technique was applied in 46 patients (CFR/IMR, CFRThermo) and the Doppler technique in another 116 patients (CFR/HMR, CFRDoppler). All measurements were performed according to a standardised protocol. The commonly applied cut-offs for CFR (<2.5), HMR (>2.5) and IMR (>25) were used.
Results: The study population was characterized by the following risk factors: arterial hypertension (63%), hypercholesterolemia (62%), positive family history for cardiovascular disease (36%), diabetes (16%) and smoking (10%). The frequency of an abnormal CFR <2.5 was 36%. There was a significant difference between the frequency of an abnormal CFR among patients with CFRThermo (8/46, 17.4%) and patients with CFRDoppler (50/116, 43.1%, p=0.002). Moreover, the median CFR was higher in the CFRThermo group compared to the CFRDoppler group (3.5 [IQR2.8] vs. 2.6 [IQR 0.9], p<0.0005) with a much larger interquartile range in the former (Figure 1). Assessment of MR revealed an abnormal result in 20% of cases which was more often observed with the thermodilution (IMR >25 in 39.1%, median 22.5 [IQR 17.0]) compared to the Doppler technique (HMR >2.5 in 12.1%, median 1.7 [IQR 0.7], p<0.0005). Multivariable analysis revealed arterial hypertension (OR 4.04, CI 1.88 – 8.77, p<0.0005) and female sex (2.12, 1.04 - 4.34, p=0.04) as independent predictors for an abnormal CFR.
Conclusion: Comparison of thermodilution and Doppler derived indexes of coronary physiology in patients with ANOCA reveals marked differences among the different measurement techniques. The results are important for the endotype classification and subsequent patient management.