The relationship between ischemia-induced left ventricular dysfunction, coronary flow reserve, and coronary steal on regadenoson stress-gated 82Rb PET myocardial perfusion imaging

Abstract

Background Gated rubidium-82 (82Rb) positron emission tomography (PET) imaging studies are acquired both at rest and during pharmacologic stress. Stress-induced ischemic left ventricular dysfunction (LVD) can produce a significant decrease in left ventricular ejection fraction (LVEF) from rest to stress. We determined the prevalence on PET of stress LVD with reduced ejection fraction (EF) and its association with absolute global and regional coronary flow reserve (CFR), and with relative perfusion defect summed difference score (SDS). Methods and Results We studied 205 patients with known or suspected coronary disease (120 M, 75 F, age 69 ± 13 years) who had clinically indicated rest/regadenoson stress 82Rb PET/CT studies. Data were acquired in dynamic gated list mode. Global and 17-segment regional CFR values were computed from first-pass flow data using a 2-compartment model and factor analysis applied to auto-generated time-activity curves. Rest and stress LVEF and SDS were quantified from gated equilibrium myocardial perfusion tomograms using Emory Cardiac Toolbox software. LVD was defined as a change in LVEF of ≤−5% from rest to stress. A subgroup of 109 patients also had coronary angiography. Stress LVD developed in 32 patients (16%), with mean EF change of −10 ± 5%, vs +6 ± 7% for patients without LVD (P < .0001). EF was similar at rest in patients with and without stress LVD (57 ± 18% vs 56 ± 16%, P = .63), but lower during stress for patients with LVD (47 ± 20% vs 61 ± 16%, P = .0001). CFR was significantly lower in patients with LVD (1.61 ± 0.67 vs 2.21 ± 1.03, Wilcoxon P = .002), and correlated significantly with change in EF (r = 0.35, P < .0001), but not with SDS (r = −0.13, P = .07). The single variable most strongly associated with high risk of CAD (i.e., left main stenosis ≥50%, LAD % stenosis ≥70%, and/or 3-vessel disease) was stress EF (χ2 = 17.3, P < .0001). There was a higher prevalence of patients with territorial CFR values ≤1.0, consistent with coronary steal, in the LVD group than in the non-LVD group (39% vs 12%, P = .001). Conclusions LVD developed in 16% of patients undergoing 82Rb PET myocardial perfusion imaging, and was associated with multivessel coronary artery disease. There was a significant relationship between LVD and coronary blood flow during stress, with LVD corresponding to a low CFR. Territorial CFR ≤1.0 was more common in patients with LVD than those without, suggesting that coronary steal is an important pathophysiologic mechanism contributing to pharmacologic stress-induced LVD.

Why LV dilatation with vasodilator stress in hypertrophic cardiomyopathy?

“…The early ratios correspond to times typically reported with vasodilator PET imaging. 2,3 The late TID measurements more closely correspond to times at which TID is assessed on vasodilator SPECT perfusion images. 6 It should be noted that the cut-off value used to define an abnormal TID index in the present report (1.13) was based upon studies employing rubidium-82 and not 13 NH 3 as the perfusion tracer .…”

“…TID on vasodilator stress PET perfusion images has previously been correlated with impaired myocardial perfusion reserve and with an acute decline in LV systolic function during stress. 2 Moreover, patients with TID on vasodilator PET images exhibit poorer clinical outcomes as compared to those without TID who have similar LV ejection fractions and perfusion defect scores. 3 Thus, TID on vasodilator stress images in CAD patients may reflect global subendocardial hypoperfusion, induction of a true oxygen supply/demand imbalance with ischemic LV dysfunction, or both.…”

The blood pressure response to vasodilator stress does not provide independent prognostic information

“…This rare occurrence is likely to also manifest through other markers of poor prognosis such as high percentage of ischemic myocardium on imaging, transient ischemic dilatation, and low poststress ejection fraction. 21,22 Indeed, these strong predictors of risk may reduce the prognostic power of vasodilatorinduced hypotension on multivariate analysis as suggested by the findings of Witbrodt et al 8 Further, since the majority of patients will experience a drop in BP with vasodilator stress due to direct peripheral vasodilation, it becomes difficult if not impossible to distinguish those who experience a drop of BP due to ischemia from the normal response. In contrast, an abnormal heart rate response to vasodilator stress, i.e., a blunted response, runs directionally opposite to the normal response seen in the majority of patients, a brisk increase in heart rate.…”

Early post-stress LV dyssynchrony: A new marker for significant CAD

“…With the introduction of PET MPI, and more recently dynamic PET with coronary flow reserve assessment, the detection of multi-vessel CAD has become less challenging. 29 PET MPI provides even better quality images, lower radiation dose, and the ability to obtained immediate peak-stress images. The latter can be used to identify true LV stunning and worsening of LV dyssynchrony.…”