Microvascular dysfunction and absolute coronary blood flow after percutaneous coronary intervention of a chronic total occlusion
Authors: Aparisi A , Garcia Guimaraes M , Gutierrez-Barrios A , Gomez-Lara J , Rivero F , Salvatella N , Tizon H , Cubero-Gallego H , Negrete A , Vaquerizo B 
Published: October 2022

Abstract

The development of a coronary chronic total occlusion (CTO) causes changes in the distal epicardial vascular bed and in the microvasculature tributary of the occluded vessel. Studies with positron emission tomography showed an increase in myocardial blood flow and coronary flow reserve (CFR) after percutaneous coronary intervention (PCI) of a CTO (1). These changes are not immediate after PCI, since they usually involve a process of weeks-months (2).
The FLOW-CTO study aims to evaluate the evolution of microvascular resistance and absolute coronary blood flow (ABF) after PCI of a CTO.
The study consecutively included patients in 4 national centers in Spain. In these patients, a coronary physiology study was performed, immediately after PCI and at 6 months follow-up. Fractional flow reserve (FRR), CFR and index of microcirculatory resistance (IMR) were determined. ABF and microvascular resistances were determined by continuous thermodilution during maximal hyperemia induced by serum infusion (3). Coronary microvascular dysfunction (MVD) was defined as an IMR ≥25 and/or an CFR &lt;2.0, in the presence of an FFR &gt;0.80. We present data from the baseline study immediately after PCI of a CTO in the first 49 patients.
Most patients were male (90%), with a median age of 62 years-old [IQR 56–69]. The prevalence of hypertension, dyslipidemia and diabetes were 71, 67 and 41%, respectively. The median left ventricular ejection fraction was 55% [IQR 45–60]. Eighty-six percent of the patients had exertional angina and 14% had history of congestive heart failure.
The most frequently involved vessel was the right coronary artery (55%). The most used technique was antegrade guidewire escalation (74%). The median length of the devices implanted was 59±25 mm. The mean percentage of residual stenosis was 8±4%.
Despite the good angiographic result, 20% of the lesions had an FFR value ≤0.80. Of those patients with a non-significant FFR value (&gt;0.80), 54% had signs of MVD. Those patients with an elevated IMR (≥25) showed a non-significant trend towards a lower ABF (143±79 vs. 192±59 mL/min; p=0.1043), with significantly higher microvascular resistance (694±206 vs. 471±166 mmHg/(l/min); p=0.0328). Those patients with a reduced CFR (&lt;2.0) had lower ABF (166±57 vs. 207±64 ml/min; p=0.0460) and a non-significant trend towards a higher microvascular resistance (535±240 vs. 466±195 mmHg/(l/min); p=0.3419). Diabetes mellitus was identified as a predictor of an elevated IMR (OR 6.3, 95% CI 1.1–13; p=0.046) or reduced CFR (OR 5.7, 95% CI 1.4–22, p=0.013).
In our study, more than half of the patients presented signs of MVD immediately after PCI of a CTO. Despite an optimal angiographic result, in a fifth of the cases we found a significant alteration of the parameters that evaluate the epicardial circulation. Diabetes mellitus was found as a predictor of MVD after PCI of a CTO.

Funding Acknowledgement
Type of funding sources: None.