Impaired cardiac sympathetic innervation assessed by MIBG activity has the greatest potential for predicting cardiac death and may be useful for identifying a threshold level for selecting patients at risk for death by heart failure, sudden cardiac death, and fatal myocardial infarction.

Despite widespread use of implantable cardioverter defibrillators (ICDs), their cost and the fact that only a certain group of patients fully benefits from the devices require appropriate risk stratification of patients. This study investigated whether altered cardiac autonomic function is associated with the occurrence of ICD discharge or lethal cardiac events. Methods: Fifty-four ICD-treated patients were prospectively followed after assessment of cardiac metaiodobenzylguanidine (MIBG) activity, quantified as the heartto-mediastinum ratio (HMR), plasma concentration of brain natriuretic peptide (BNP), and left ventricular ejection fraction (LVEF). Patients were divided into 2 groups based on the presence (group A, n 5 21) or absence (group B, n 5 33) of appropriate ICD discharge during a 15-mo period. Results: Group A had a significantly lower level of MIBG activity and a higher plasma BNP level than did group B. Univariate analysis revealed BNP level, any medication, and late HMR to be significant predictors, and multivariate analysis showed late HMR to be an independent predictor. An HMR of less than 1.95 with a plasma BNP level of more than 187 pg/mL or an LVEF of less than 50% had significantly increased power to predict ICD shock: positive predictive values, 82% (HMR 1 BNP) and 58% (HMR 1 LVEF); negative predictive values, 73% (HMR 1 BNP) and 77% (HMR 1 LVEF); sensitivities, 45% (HMR 1 BNP) and 67% (HMR 1 LVEF); and specificities, 94% (HMR 1 BNP) and 70% (HMR 1 LVEF). Conclusion: When combined with plasma BNP concentration or cardiac function, cardiac MIBG activity is closely related to lethal cardiac events and can be used to identify patients who would benefit most from an ICD.

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The reduction in mortality risk achieved by using ACE inhibitors and/or beta-blockers is associated with the severity of impairment of cardiac MIBG uptake. Cardiac MIBG activity can consequently be of long-term prognostic value in predicting the effectiveness of such treatment in patients with heart failure.

We examined prognostic interactions among cardiac autonomic function assessed by 123 I-labeled metaiodobenzylguanidine ( 123 I-MIBG) activity, hemoglobin, and kidney function in chronic heart failure patients. Anemia, chronic kidney disease, and impairment of cardiac sympathetic function have been shown as determinants of prognosis in heart failure patients, but there has been little information on their synergistic correlations with cardiac mortality. Methods: After evaluations of hemoglobin and estimated glomerular filtration rate (GFR), 468 heart failure patients with left ventricular ejection fraction less than 50% underwent cardiac 123 I-MIBG imaging before discharge and were then followed up for a mean interval of 60.5 mo with a primary endpoint of cardiac death. Cardiac 123 I-MIBG activity was quantified using heart-to-mediastinum ratio (HMR) and washout rate. Results: For 89 fatal cardiac events documented (19.0%), besides New York Heart Association class, multivariate Cox analysis revealed HMR, hemoglobin, and estimated GFR as significant independent determinants, with hazard ratios of 0.215 (P 5 0.0129; 95% confidence interval [CI], 0.064-0.718), 0.821 (P 5 0.0062; 95% CI, 0.708-0.946), and 0.984 (P 5 0.0243; 95% CI, 0.970-0.998), respectively. Receiver-operating-characteristic analysis determined the thresholds for identifying patients at increased risk for cardiac death to be 1.57 for HMR, 11.9 g/dL for hemoglobin, and 46.4 mL/min/1.73 m 2 for estimated GFR. Combining the 4 independent predictors incrementally (P , 0.05) improved prognostic powers maximally up to a global x 2 value of 97.3 compared with sole or other combinations. Conclusion: Hemoglobin, kidney function, and alterations of cardiac sympathetic nerve activity are independently and synergistically associated with increased cardiac mortality in chronic heart failure patients, together with New York Heart Association functional class.