Predicting the Need for an Implantable Cardioverter Defibrillator Using Cardiac Metaiodobenzylguanidine Activity Together with Plasma Natriuretic Peptide Concentration or Left Ventricular Function

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 stratifica-tion of patients. This study investigated whether altered cardiac autonomic function is associated with the occurrence of ICD dis-charge or lethal cardiac events. Methods: Fifty-four ICD-treated patientswere prospectively followed after assessment of cardiac metaiodobenzylguanidine (MIBG) activity, quantified as the heart-to-mediastinum ratio (HMR), plasma concentration of brain natri-uretic 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 dis-charge during a 15-mo period. Results: Group A had a signifi-cantly 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 mul-tivariate 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 ICDshock: positive predictive values, 82 % (HMR1 BNP) and 58 % (HMR1 LVEF); negative predictive values, 73% (HMR1 BNP) and 77 % (HMR1 LVEF); sensitivities, 45 % (HMR 1 BNP) and 67 % (HMR1 LVEF); and specificities, 94 % (HMR1 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. Key Words: implantable cardioverter defibrillator; metaiodoben-zylguanidine imaging; brain natriuretic peptide; sudden cardia