Myocardial imaging in patients with defibrillator patch electrodes

Abstract

Radionuclide imaging methods such as single-photon emission tomography (SPECT) and positron emission tomography (PET) are well-established techniques to evaluate myocardial ischemia and viability in patients with coronary artery disease. 1‐3 Life-threatening ventricular tachyarrhythmias are frequent findings in these patients. There is growing consensus that implantable cardioverter defibrillator (ICD) therapy reduces the incidence of sudden cardiac death in this group. 4‐8 Considering the progressive nature of the underlying disease, these patients may require radionuclide imaging to guide further therapy. Initiated by anecdotal evidence of a discrepancy between coronary angiography (no significant stenosis), thallium-201 (Tl-201) SPECT (persistent defect), and fluorodeoxyglucose-18 (F-FDG-18) PET (no defect) in patients with epicardially placed ICD leads, we investigated the hypothesis that epicardial ICD patch electrodes cause pseudodefects with SPECT. Therefore, Tl-201 SPECT, technetium-99m (Tc-99m) SPECT, and FFDG-18 PET measurements with a thorax phantom were performed to validate findings in patients and to clarify the effects of photon attenuation in the ICD patch electrode in relation to patch location, patch material composition, and the choice of nuclearcardiologic imaging modality. ICD patch electrodes placed directly on the epicardium were frequently used until recently. 9 ‐11 ••• Three different patch electrodes were examined: model 6897-M (Medtronic, Minneapolis, Minnesota), model L67 (CPI, St. Paul, Minnesota), and model 1501 (Siemens, Erlangen, Germany). The electrodes are shown in Figure 1. Technical specifications and attenuation coefficients for gamma radiation of the Medtronic and the CPI electrodes are listed in Table 1. The Siemens electrode is identical in composition to the CPI electrode.