Exploring Coronary Circulatory Response to Stenosis and Its Association with Invasive Physiologic Indices Using Absolute Myocardial Blood Flow and Coronary Pressure
Background—Although invasive physiologic assessment for coronary stenosis has become a standard practice to guide treatment strategy, coronary circulatory response and changes in invasive physiologic indices, according to different anatomical 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 (PET) and invasive physiologic measurement were analyzed. Myocardial blood flow (MBF) measured using PET and invasively measured coronary pressures were used to calculate microvascular resistance (MVR) and stenosis resistance.
Results—With progressive worsening of angiographic stenosis severity, both resting and hyperemic trans-stenotic pressure gradient and stenosis resistance increased (P<0.001 for all) and hyperemic MBF (P<0.001) and resting MVR (P=0.012) decreased. Resting MBF (P=0.383) and hyperemic MVR (P=0.431) were not changed and maintained stable. Both fractional flow reserve (FFR) and instantaneous wave free ratio (iFR) decreased as angiographic stenosis severity, stenosis resistance, and trans-stenotic pressure gradient increased, and hyperemic MBF decreased (all P values<0.001). When the presence of myocardial ischemia was defined by both low hyperemic MBF and low coronary flow reserve (CFR), the diagnostic accuracy of FFR and iFR did not differ, regardless of cut-off values of hyperemic MBF and CFR.
Conclusions—This study demonstrated how the coronary circulation changes in response to increasing coronary stenosis severity using 13N-ammonium PET-derived MBF and invasively measured pressure data. Currently used resting and hyperemic pressure-derived invasive physiologic indices have similar patterns of relationships to the different anatomic and hemodynamic lesion severity.
Clinical Trial Registration—URL: https://clinicaltrials.gov Unique Identifier: NCT01366404
- instantaneous wave free ratio
- coronary artery disease
- myocardial ischemia
- myocardial perfusion imaging
- positron emission tomography
- fractional flow reserve
- Received June 10, 2017.
- Revision received July 17, 2017.
- Accepted August 11, 2017.