Risk Stratification of Patients With NonObstructive Coronary Artery Disease Using Resistive Reserve Ratio

Abstract

Background Resistive reserve ratio (RRR), or the ratio of baseline to hyperemic microvascular resistance, has prognostic implications in predicting clinical outcomes in patients with obstructive coronary artery disease. However, its value in patients with angina or ischemia with nonobstructive coronary artery disease is unknown. Methods and Results We included 1692 patients with nonobstructive coronary artery disease who underwent invasive coronary vasoreactivity testing. Abnormal coronary flow reserve (CFR, the ratio of hyperemic and baseline resting flow velocities) and RRR were defined as <2.5 and <2.62, respectively. The mortality rate was marginally higher in patients with abnormal CFR (428 patients [25%]) than those with normal CFR (38 [9%] versus 81 [6%]; P =0.08), and was significantly higher in patients with abnormal RRR (716 patients [42%]) than those with normal RRR (70 [10%] versus 49 [5%], P =0.0002) over the median follow‐up of 11.3 years. Patients with abnormal CFR had marginally lower survival than those with normal CFR (log‐rank P =0.08). In contrast, patients with abnormal RRR had significantly lower survival than those with normal RRR (log‐rank P =0.001). Abnormal RRR was associated with shorter time to death even after adjustment for other covariates (adjusted hazard ratio, 1.63; 95% CI, 1.11–2.38; P =0.01). Conclusions In patients with no obstructive coronary artery disease, RRR was superior to CFR in predicting long‐term survival. An RRR <2.62 was associated with 1.6 times increased risk of death in patients with nonobstructive coronary artery disease. Indices of coronary microcirculatory resistive reserve comprising flow‐ and pressure‐derived values may reflect underlying microvascular pathology more faithfully than flow‐alone indices like CFR.

Angiography-based Coronary Microvascular Assessment with and without Intracoronary Pressure Measurements ─ a Systematic Review

“…Alternatively, RRR can also be represented as coronary ow reserve (CFR) divided by the ratio between resting and hyperemic distal pressure (Pd). In contrast with IMR, which does not provide information on the vasodilatory capacity of the microcirculation, RRR reliably re ects the ability of the coronary microcirculation to adjust its resistance in response to adenosine and provides prognostic value in both acute myocardial infarction and nonobstructive coronary artery disease [45][46][47] . CFR p−3D was proposed by Tar et al to calculate CFR using invasive intracoronary pressure data and 3D anatomic reconstructions of the target vessel from angiography 22 .…”

Association of endothelial glycocalyx shedding and coronary microcirculation assessed by an angiography-derived index of microcirculatory resistance in patients with suspected coronary artery disease

“…RRRangio is a measurement of coronary microvascular vasodilatory capacity, describing the ability of the microcirculation to respond to a vasodilatory stimulus regardless of epicardial stenosis ( 15 , 18 , 19 ). Due to the lack of reference on the optimal cut-off value to define impaired coronary vasodilator capacity (IMVC) using RRRangio, referring to the methods of previous studies ( 15 , 18 , 19 ), we used RRRangio below the median value was used to define IMVC.…”

Coronary Physiology: Delivering Precision Medicine?

“…It can be performed with either the bolus or doppler thermodilution techniques. There is no clear cut-off for the diagnosis of CMVD but RRR <2.62 by Doppler was associated with a 1.6-fold higher risk of death in patients with angina or ischemia with NOCAD [38].…”