Gated ⁸²Rb PET measurement of increased left ventricular asynchrony during stress as a correlate of conventional cardiac resynchronization therapy criteria

Objectives Left ventricular (LV) asynchrony is common in pts with heart failure and is improved with resynchronization (CRT). Asynchrony parameters phase bandwidth (BW) and standard deviation (SD) can be obtained from ⁸²Rb PET myocardial perfusion imaging at rest and stress. Qualifying criteria for CRT comprise LV ejection fraction (EF) and ECG conduction delay, but not BW and SD. The relation between PET rest and stress BW and SD, LV EF, and ECG conduction, is unknown.

Methods Data were analyzed retrospectively for 100 pts who had gated ⁸²Rb PET and resting 12-lead ECG showing non-paced sinus rhythm. ECGs were interpreted by an experienced reader, who classified conduction as normal (NL) or delayed (IVCD) including left or right bundle branch block (BBB) or nonspecific. Emory Cardiac Toolbox algorithms were applied to ⁸²Rb PET to obtain LVEF, and rest and stress BW and SD (in degrees).

Results ECG conduction was NL in 53% of pts and showed IVCD in 47%. 26 pts had LBBB, 13 had RBBB & 9 had nonspecific delay. 40 pts had rest EF≤35% & 60 had EF>35%. EF was lower in pts with IVCD vs. NL (42±17% vs. 58±15%; p < 0.0001), but similar among ECG conduction patterns (p = 0.76). Four categories of LV conduction and function were defined: NL & EF>35% (N=60); IVCD & EF>35% (N=23); NL & EF≤35% (N=6); IVCD & EF≤35% (N=11, these pts meet criteria for CRT). Rest SD values were similar among the four categories (ANOVA F-ratio = 0.7, p=0.33), but stress SD differed significantly (F-ratio = 6.9, p<0.001), and was progressively larger for each category (ρ = 0.40, p<0.0001): SD = 21±18, 28±17, 33±11 & 41±17. Parameters that agreed most strongly with conventional criteria for CRT were stress SD>22 (ROC area 80%) and BW>68 (ROC area 84%).

Conclusions Asynchrony parameters obtained during stress, but not rest, correlate most closely with CRT qualifying criteria, so that ⁸²Rb PET phase analysis during stress may aid in stratifying potential candidates for CRT