Impact of diurnal variations in the QRS complex and T-waves on the eligibility of subcutaneous implantable cardioverter-defibrillators.

BACKGROUND: Subcutaneous implantable cardioverter-defibrillators (S-ICDs) are an established therapy for preventing sudden cardiac death. However, a considerable number of patients still undergo inappropriate shocks even after conventional pre-implantation ECG screening.

OBJECTIVE: This study aimed to elucidate the additional impact of diurnal variations in the QRS complex and T-waves of 24-h Holter monitoring on the S-ICD eligibility.

METHODS: Patients with transvenous ICDs who did not need pacing were selected for the study. The ECG was recorded by placing the electrodes to simulate the three sensing vectors of an S-ICD, with the patient in the standing and supine positions (conventional), during exercise, and during 24-h Holter monitoring. We investigated the additional discrimination of the diurnal variations in patients ineligible for S-ICDs and characteristics of those patients.

RESULTS: Among 86 patients (82% males; mean age 54±16 years) analyzed by all three screenings, two (2.3%) and three (3.4%) were considered ineligible by conventional and exercise ECGs, respectively. An additional 21 patients (24.4%) were found ineligible by Holter screening. A multivariate logistic regression analysis demonstrated that Brugada syndrome and an increased QRS duration per millisecond were associated with ineligibility (odds ratio 5.74; 95% confidence interval 1.74-20.2; p=0.003, odds ratio 1.04; 95% confidence interval 1.01-1.07; p=0.007, respectively). T-wave oversensing was mostly observed during 0-6 am but no significant diurnal variations were observed in the incorrect QRS profiles.

CONCLUSION: The detection of diurnal variations by Holter monitoring in addition to conventional screening is expected to be useful for determining the S-ICD eligibility.