The Influence of Coronary Physiology and Wall Shear Stress on Pathophysiology and Prognosis in Coronary Artery Disease

Abstract

Background Coronary physiology is a discipline involving the measurement of pressure, flow, and resistance in the coronary circulation. Our understanding of this field remains incomplete.

Methods and Results The relationship between coronary physiology and wall shear stress (WSS) was examined in 88 patients. After adjusting for angiographic severity of the underlying lesion, fractional flow reserve (FFR) and the instantaneous wave-free ratio (iFR) remained independent predictors of the total burden of low WSS and maximum lesion WSS. The association between myocardial bridge (MB), WSS, and atheroma development was examined in 92 patients. Patients with MB had significantly lower WSS and higher maximal plaque burden compared to controls. The natural evolution of the microcirculation after revascularization in ST-elevation myocardial infarction (STEMI) was studied in 22 patients. All patients had serial coronary physiology measurements in the culprit vessel after successful percutaneous coronary intervention (PCI), and significant improvements in microcirculatory function were found over time. The outcomes of patients with discordant microcirculatory physiology indices after PCI were studied in 502 patients. Microcirculatory discordance was found in 28% of patients, and these patients had higher major adverse cardiac event (MACE) rates compared to normal controls. Real-world outcomes of patients undergoing FFR-guided PCI were evaluated in a large Australian population registry comprising 10,304 patients. After multivariable adjustment, FFR-guidance was an independent predictor of MACE.

Conclusions Myocardial ischaemia is independently associated with pathological WSS. Low WSS occur in MB and is associated with atheroma formation. Microcirculatory function improves within minutes after revascularization in STEMI. Microcirculatory discordance is associated with worse outcomes after PCI. FFR-guided PCI is associated with improved outcomes in an Australian population.