The Role of I-123 Metaiodobenzylguanidine Imaging in Management of Patients With Heart Failure

Single-photon cardiac imaging in patients with cardiac implantable electrical devices

Nuclear imaging techniques like single-photon emission computed tomography (SPECT) and radionuclide angiography have wide applications in patients receiving a cardiac implantable electrical device (CIED), who cannot usually undergo cardiac magnetic resonance. Our aim was to provide an update of single-photon imaging clinical applications, with a specific focus on CIED recipients. SPECT imaging is commonly used in CIED patients to assess myocardial perfusion, but it can also be used to evaluate myocardial viability, which is an important predictor of LV function improvement by cardiac resynchronization therapy (CRT). Radionuclide angiography has shown higher temporal resolution and reproducibility than SPECT in the evaluation of cardiac function and dyssynchrony. Left ventricular dyssynchrony as assessed by radionuclide angiography with phase analysis may be reliably used for CRT patient selection and evaluation of CRT response. SPECT imaging with meta-iodo-benzyl-guanidine allows for cardiac sympathetic innervation examination, which may be used for prognostic stratification of heart failure patients and prediction of ventricular tachyarrhythmias. Finally, promising results in CIED infection diagnosis have been shown by SPECT with radiolabeled autologous white blood cells.

CMR-Based Risk Stratification of Sudden Cardiac Death and Use of Implantable Cardioverter-Defibrillator in Non-Ischemic Cardiomyopathy

Non-ischemic cardiomyopathy (NICM) is one of the most important entities for arrhythmias and sudden cardiac death (SCD). Previous studies suggest a lower benefit of implantable cardioverter–defibrillator (ICD) therapy in patients with NICM as compared to ischemic cardiomyopathy (ICM). Nevertheless, current guidelines do not differentiate between the two subgroups in recommending ICD implantation. Hence, risk stratification is required to determine the subgroup of patients with NICM who will likely benefit from ICD therapy. Various predictors have been proposed, among others genetic mutations, left-ventricular ejection fraction (LVEF), left-ventricular end-diastolic volume (LVEDD), and T-wave alternans (TWA). In addition to these parameters, cardiovascular magnetic resonance imaging (CMR) has the potential to further improve risk stratification. CMR allows the comprehensive analysis of cardiac function and myocardial tissue composition. A range of CMR parameters have been associated with SCD. Applicable examples include late gadolinium enhancement (LGE), T1 relaxation times, and myocardial strain. This review evaluates the epidemiological aspects of SCD in NICM, the role of CMR for risk stratification, and resulting indications for ICD implantation.

Usefulness of Cardiac MetaIodobenzylguanidine Imaging to Improve Prognostic Power of the Model for End-Stage Liver Disease Scoring System in Patients With Mild-to-Moderate Chronic Heart Failure

Liver dysfunction has a prognostic impact on the outcomes of patients with advanced heart failure (HF). The model for end-stage liver disease (MELD) score is a robust system for rating liver dysfunction, and a high score has been shown to be associated with a poor prognosis in ambulatory patients with HF. In addition, cardiac metaiodobenzylguanidine (MIBG) imaging provides prognostic information in patients with chronic HF (CHF). However, the long-term predictive value of combining the MELD score and cardiac MIBG imaging in patients with CHF has not been elucidated. To prospectively investigate whether cardiac MIBG imaging provides additional prognostic value to the MELD score in patients with mild-to-moderate CHF, we studied 109 CHF outpatients (New York Heart Association: 2.0 ± 0.6) with left ventricular ejection fraction <40%. At enrollment, an MELD score was obtained, and the heart-to-mediastinal ratio on delayed imaging and MIBG washout rate (WR) were measured using cardiac MIBG scintigraphy. During a follow-up period of 7.5 ± 4.2 years, 36 of 109 patients experienced cardiac death (CD). On multivariate Cox analysis, MELD score and WR were significantly independently associated with CD, although heart-to-mediastinal ratio showed an association with CD only on univariate Cox analysis. Patients with abnormal WR (>27%) had a significantly greater risk of CD than those with normal WR in both those with high MELD scores (≥10; hazard ratio 4.0 [1.2 to 13.6]) and with low MELD scores (<10; hazard ratio 6.4 [1.7 to 23.2]). In conclusion, cardiac MIBG imaging would provide additional prognostic information to the MELD score in patients with mild-to-moderate CHF.