Noninvasive Arrhythmia Risk Stratification in Idiopathic Dilated Cardiomyopathy

Abstract

Background-Arrhythmia risk stratification with regard to prophylactic implantable cardioverter-defibrillator therapy is a completely unsolved issue in idiopathic dilated cardiomyopathy (IDC). Methods and Results-Arrhythmia risk stratification was performed prospectively in 343 patients with IDC, including analysis of left ventricular (LV) ejection fraction and size by echocardiography, signal-averaged ECG, arrhythmias on Holter ECG, QTc dispersion, heart rate variability, baroreflex sensitivity, and microvolt T-wave alternans. During 52Ϯ21 months of follow-up, major arrhythmic events, defined as sustained ventricular tachycardia, ventricular fibrillation, or sudden death, occurred in 46 patients (13%). On multivariate analysis, LV ejection fraction was the only significant arrhythmia risk predictor in patients with sinus rhythm, with a relative risk of 2.3 per 10% decrease of ejection fraction (95% CI, 1.5 to 3.3; Pϭ0.0001). Nonsustained ventricular tachycardia on Holter was associated with a trend toward higher arrhythmia risk (RR, 1.7; 95% CI, 0.9 to 3.3; Pϭ0.11), whereas ␤-blocker therapy was associated with a trend toward lower arrhythmia risk (RR, 0.6; 95% CI, 0.3 to 1.2; Pϭ0.13). In patients with atrial fibrillation, multivariate Cox analysis also identified LV ejection fraction and absence of ␤-blocker therapy as the only significant arrhythmia risk predictors. Conclusions-Reduced LV ejection fraction and lack of ␤-blocker use are important arrhythmia risk predictors in IDC, whereas signal-averaged ECG, baroreflex sensitivity, heart rate variability, and T-wave alternans do not seem to be helpful for arrhythmia risk stratification. These findings have important implications for the design of future studies evaluating prophylactic implantable cardioverter-defibrillator therapy in IDC.

Prophylactic Implantation of Cardioverter Defibrillators in Idiopathic Nonischemic Cardiomyopathy for the Primary Prevention of Death: A Narrative Review

“…The Marburg Cardiomyopathy Study revealed that a low LVEF and the lack of β-blocker use predicted arrhythmia in patients with NCM. 17 Other studies have demonstrated that ventricular arrhythmias are associated with myocardial scar tissue in NCM patients, and this is present in almost 50% of the patients with premature ventricular complexes or monomorphic ventricular tachycardia. 18 Aldosterone antagonists may reduce arrhythmic foci because of their potential to inhibit myocardial fibrosis and need more study in these patients.…”

Evidence regarding clinical use of microvolt T-wave alternans

“…This study, while it is included in the summary statistics, appears to be an outlier. One possible explanation for MTWA performance in Grimm 21 compared to the other studies of MTWA in DCM patients might be that in Grimm beta-blockers were withheld for at least 24 hours prior to MTWA testing while 74% of patients took beta-blockers during follow-up. In contrast in ALPHA 7 , Kitamura 3 , and Bloomfield 5 were not withheld prior to MTWA testing.…”

“…Grimm 21 it is possible that the withdrawal of beta-blockers acutely increased the incidence of MTWA without concomitantly increasing VTEs during follow-up because these same patients were taking beta-blockers during follow-up. The results of these studies suggest that it may be advisable to perform MTWA tests in patients while they are on the same pharmacologic regimen as they will be on during follow-up.…”

Appropriate ICD Therapy in Patients With Idiopathic Dilated Cardiomyopathy Long-Term Follow-Up

“…Although various risk predictors have been studied for arrhythmia risk stratification in patients with DCM, it has been suggested that only a few parameters can be reliably used for risk stratification. [22][23][24][25] Even the electrophysiologic study results alone were not helpful in deciding who to refer for ICD implantation. Fazio, et al found that the only clinical or EP study-derived variable predictive of future ICD shocks was the presence of inducible sustained VT or VF during preoperative EP studies.…”