Electrocardiogram-Gated ¹⁸F-FDG PET/CT Hybrid Imaging in Patients with Unsatisfactory Response to Cardiac Resynchronization Therapy: Initial Clinical Results

Abstract

The present study aimed to distinguish responders to cardiac resynchronization therapy (CRT ) from nonresponders, using electrocardiogram-gated 18 F-FDG PET/CT. Methods: Seven consecutive CRT nonresponders were included in the study, along with 7 age-and sex-matched CRT responders, serving as reference material. Therapy response was defined as clinical improvement ($1 New York Heart Association class) and evidence of reverse remodeling. Besides PET/CT, we measured brain natriuretic peptide levels and assessed dyssynchrony using transthoracic echocardiography. Results: Compared with nonresponders, CRT responders showed significant differences in the declines of left-ventricular end-systolic volume and brain natriuretic peptide and in left-ventricular dyssynchrony (global left-ventricular entropy), extent of the myocardial scar burden, and biventricular pacemaker leads positioned within viable myocardial regions. Among the nonresponders, further therapy management was guided by the PET/CT results in 4 of 7 patients. Conclusion: Cardiac hybrid imaging using gated 18 F-FDG PET/CT enabled the identification of potential reasons for nonresponse to CRT therapy, which can guide subsequent therapy.

Imaging cardiac dyssynchrony

“…The first published description of the use of SPECT to assess LV dyssynchrony by Chen in 2005 [20] built both on myocardial perfusion imaging (MPI) SPECT work by Cooke in 1994 [21] and the technique described by Links for MUGA. More recently, dyssynchrony has also been assessed from gated myocardial PET using both 82 Rb perfusion imaging [22] and 18 F fluorodeoxyglucose (FDG) viability imaging [23]. There is also ongoing research into dyssynchrony assessment using gated blood pool SPECT [24][25][26][27] and planar MUGA [28], though there are important differences between these nuclear techniques and phase analysis from MPI, as we shall detail later.…”

“…While there is evidence that transmural scar at the site of LV pacing prohibits CRT response [57], the effect of non-transmural scar remains unclear [58]. One small study [23] evaluated differences between RSP (n = 7) and age-and gendermatched nonresponders (NRSP, n = 7) using 18 F FDG PET/CT, finding statistically significant differences (p \ 0.05) both in scar burden (RSP scar = 10 ± 8 %; NRSP scar = 30 ± 21 %) and QGS phase entropy (RSP, E = 77 ± 4 %; NRSP, E = 83 ± 3 %). There was no association between lead position in viable myocardium and persistent dyssynchrony by echocardiography, but pacemaker leads in all CRT responders were positioned in viable areas.…”

Myocardial perfusion scintigraphy: past, present and future

“…There is now a growing literature on the uses of MPS in cardiac failure. In addition to providing information on perfusion, it can give an accurate assessment of both systolic and diastolic left ventricular function, including phase and movement asynchrony which, in conjunction with CT anatomy information from hybrid imaging, can be used in planning for positioning of various intracardiac devices [22][23][24][25]. Another potential growth area in nuclear cardiac imaging is SPECT blood pool imaging.…”

Cardiac Simulation to Personalize Cardiac Resynchronization Therapy

“…Initial experience with fusion imaging, overlaying magnetic resonance imaging data on myocardial scar location, and cardiac venous anatomy onto fluoroscopy or positron emission tomography and computed tomography have been developed to tailor CRT delivery and avoid LV lead placement in areas of scar tissue. 6,7 Despite these efforts, the rate of nonresponse to CRT remains unchanged, and the use of sequential imaging may lead to increased costs. In an ideal situation, the information obtained from each patient could be used to generate a cardiac model that permits accurate prediction of the effects of CRT for each individual.…”