Myocardial blood flow and coronary flow reserve by rest/stress regadenoson gated ⁸²Rb PET correlate with stress-induced changes in measurements of left ventricular asynchrony

Objectives Left ventricular (LV) asynchrony contributes to LV dysfunction, and is improved by resynchronization (CRT). Asynchrony is quantified on myocardial perfusion imaging as phase bandwidth (BW) and phase standard deviation (SD), in units of degrees. Prior studies suggest that BW and SD do not change from rest to stress. Whether this is true in a broad pt population, and whether SD and BW correlate with myocardial blood flow (MBF) and coronary flow reserve (CFR), are not known.

Methods Data were analyzed retrospectively for 61 pts with known/suspected coronary disease who had rest/stress CT attenuation-corrected ⁸²Rb PET data acquired in gated list mode. Rest MBF (rMBF), stress MBF (sMBF) and CFR were computed by factor analysis. LV ejection fraction, summed rest scores (SRS), BW and SD were quantified. Phase values indicating asynchrony were: stress BW>64, rest BW>88 at, stress SD>29, rest SD>49 (J Nucl Card 2011).

Results For the 61 pts, ejection fraction=53±18 & SRS=9.5±7.5. Asynchrony was common at rest: average BW and SD were 82±52 and 28±15, and did not change with stress (81±57 & 26±16, p=NS). Pts (N=24) with abnormal stress BW had lower sMBF than pts with normal stress BW (236±78 vs. 405±162 ml/min/100 mg, p<0.0001). In pts (N=33) with low CFR (≤2.0), SD increased with stress (worsened asynchrony) vs. pts with CFR>2 whose SD decreased with stress (median SD change = +2 versus -7, Wilcoxon p=0.001). In the 16 pts whose SD increased with stress, sMBF was lower than the 45 other pts (235±92 versus 337±161 ml/min/100g, p=0.001). BW & SD correlated inversely with sMBF (r = -0.54, p<0.0001 & r = -0.56, p<0.0001). SD change correlated inversely with CFR (r = -0.33, p=0.009).

Conclusions Further study is needed to determine if combining ⁸²Rb PET MBF and CFR with asynchrony parameters improves prediction of response to CRT