Exploring Coronary Circulatory Response to Stenosis and Its Association With Invasive Physiologic Indexes Using Absolute Myocardial Blood Flow and Coronary Pressure

Abstract

Background: Although invasive physiological assessment for coronary stenosis has become a standard practice to guide treatment strategy, coronary circulatory response and changes in invasive physiological indexes, according to different anatomic and hemodynamic lesion severity, have not been fully demonstrated in patients with coronary artery disease.

Methods: One hundred fifteen patients with left anterior descending artery stenosis who underwent both ¹³N-ammonia positron emission tomography and invasive physiological measurement were analyzed. Myocardial blood flow (MBF) measured with positron emission tomography and invasively measured coronary pressures were used to calculate microvascular resistance and stenosis resistance.

Results: With progressive worsening of angiographic stenosis severity, both resting and hyperemic transstenotic pressure gradient and stenosis resistance increased (P<0.001 for all) and hyperemic MBF (P<0.001) and resting microvascular resistance (P=0.012) decreased. Resting MBF (P=0.383) and hyperemic microvascular resistance (P=0.431) were not changed and maintained stable. Both fractional flow reserve and instantaneous wave-free ratio decreased as angiographic stenosis severity, stenosis resistance, and transstenotic pressure gradient increased and hyperemic MBF decreased (all P<0.001). When the presence of myocardial ischemia was defined by both low hyperemic MBF and low coronary flow reserve, the diagnostic accuracy of fractional flow reserve and instantaneous wave-free ratio did not differ, regardless of cutoff values of hyperemic MBF and coronary flow reserve.

Conclusions: This study demonstrated how the coronary circulation changes in response to increasing coronary stenosis severity using ¹³N-ammonium positron emission tomography-derived MBF and invasively measured pressure data. Currently used resting and hyperemic pressure-derived invasive physiological indexes have similar patterns of relationships to the different anatomic and hemodynamic lesion severities.

Clinical trial registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01366404.

Keywords: coronary artery disease; fractional flow reserve, myocardial; instantaneous wave free ratio; myocardial ischemia; myocardial perfusion imaging; positron-emission tomography.