Application of microvolt T-wave alternans testing in scheduling implantable cardioverter-defibrillator placement for the primary prevention of sudden cardiac death in patients with left ventricular dysfunction.

BACKGROUND: Patients with left ventricular ejection fraction (LVEF) ≤ 35% are eligible for implantable cardioverter-defibrillator (ICD) placement for the primary prevention of sudden cardiac death (SCD). This recommendation results in continuously growing waiting lists of patients who have been qualified for and are awaiting the procedure. Whiled reduced LVEF is a feature shared by all the patients in this group, the risk of malignant ventricular arrhythmias varies widely. It therefore seems important from the clinical point of view to improve the waiting lists by identifying patients at the lowest risk of SCD, who can safely wait for the procedure, while higher-risk patients undergo the procedure before them.

AIM: To verify the utility of microvolt T-wave alternans (MTWA) testing, which is characterised by high negative predictive value (NPV), in scheduling ICD implantation in these patients.

METHODS: The study included 152 patients with LVEF ≤ 35%, qualified for ICD implantation for the primary prevention of SCD, and managed in accordance with the current recommendations. Patients with a history of malignant ventricular arrhythmias were excluded. Each patient underwent MTWA testing during chronic treatment (including beta-blockers) and was followed-up.

RESULTS: During 14 ± 8 months of follow-up, the primary outcome, which included SCD, non-fatal sustained ventricular arrhythmia, or appropriate high-voltage ICD discharge, was observed in 16 patients. The one-year event rate was 13.1% (5.8-19.8%) in non-negative MTWA patients and 0% in those who had negative MTWA result (p = 0.027). The NPV of the MTWA test was 100% (95% CI 92.73- 00%).

CONCLUSIONS: In the group of patients with left ventricular systolic dysfunction, excluding patients with a history of malignant ventricular arrhythmia, the NPV of MTWA was 100% over 12 months of observation. MTWA may therefore be considered useful in determining the order of ICD implantation procedures in this group of patients by identifying patients at a relatively low risk of malignant ventricular arrhythmias, who can be relatively safely rescheduled for ICD implantation at a later time. Future studies should concentrate on this issue.