Objective To assess the prognostic value of cardiac iodine-123 metaiodobenzylguanidine (123I-MIBG) scintigraphy to predict ventricular arrhythmias in patients with heart failure (HF) listed for implantable cardioverter-defibrillator (ICD) devices as primary prevention.
Design, setting and patients A prospective cohort study in 27 patients with HF referred for ICD implantation (alone or in combination with cardiac resynchronisation therapy) at a tertiary cardiac centre.
Methods Cardiac 123I-MIBG scintigraphy was performed with calculation of early and late heart-to-mediastinum (H:M) ratios, washout rate, and summed defect score from single photon emission computed tomography (SPECT) acquisition. Resting myocardial perfusion SPECT using 99mTc-tetrofosmin was also performed and a summed score calculated. Innervation-perfusion mismatch was evaluated by comparing SPECT scores.
Main outcome measure Ventricular arrhythmia requiring ICD therapy.
Results At 16 months median follow-up, 10 (37%) patients experienced a significant arrhythmic event. Compared with patients who suffered no event, these individuals had lower early and late H:M ratio and higher 123I-MIBG SPECT defect scores: 1.83±0.43 versus 2.34±0.33 (p<0.001); 1.54±0.38 versus 1.96±0.38 (p=0.005); 37.0±9.4 versus 25.5±7.7 (p=0.001). Mismatch scores were also higher: 18.5±8.5 versus 8.4±5.0 (p<0.01). Optimal thresholds for predicting arrhythmia were <1.94 for early H:M ratio (sensitivity 70%, specificity 88%); <1.54 for late H:M ratio (sensitivity 60%, specificity 88%); 123I-MIBG SPECT defect score ≥31 (sensitivity 78%, specificity 77%).
Conclusions In HF patients without prior ventricular arrhythmia, 123I-MIBG imaging strongly predicts future arrhythmic risk. This may inform the process of case selection for ICD therapy on an individual basis, although no single measurement provides sufficient reassurance to obviate device implantation if otherwise clinically indicated.
- implantable cardioverter-defibrillator
- heart failure
- ventricular arrhythmia
- imaging and diagnostics
- nuclear cardiology
- cardiac resynchronisation therapy
- allied specialities
- cardiac function
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Funding The study was supported by GE Healthcare Ltd who provided all doses of the 123I-MIBG radiopharmaceutical used in the study. There was no additional financial support from any company or institution, and the study authors have no other conflicts of interest to declare.
Competing interests None to declare.
Ethics approval This study was approved by the local Research Ethics Committee (REC No. 07/Q0404/48) and Administration of Radioactive Substances Advisory Committee (ARSAC). Written informed consent was obtained from all participants. The study was carried out in accordance with the principles of the Declaration of Helsinki.
Provenance and peer review Not commissioned; externally peer reviewed.