Prevalence of subcutaneous implantable cardioverter-defibrillator based on template ECG screening and ineligible surface ECG predicting factors in patients with hypertrophic cardiomyopathy in China

The subcutaneous implantable cardioverter-defibrillator (S-ICD) may provide comparable protection while avoiding the disadvantage of transvenous lead, but the abnormal features of the hypertrophic cardiomyopathy (HCM) electrocardiogram (ECG) make it a challenge for S-ICD template screening. We aimed to investigate S-ICD eligibility according to the S-ICD manufacturer’s surface ECG screening template in China, and further analyze its corresponding ineligible predicting factors in 12-lead suface ECG. A total of 179 HCM patients (114 males; mean age: 45 ± 14 years) underwent S-ICD screening at rest and on exercise, among which 91 patients (50.8%) were eligible for S-ICD. Among the patients who passed screening, 43 (47.3%) had 3 vectors eligibility; 64 (70.3%) screening qualified on both sides; 10 patients (11.0%) passed the screening while the electrodes located only on the left parasternal line versus 17 patients (18.7%) moved to the right line. The secondary sensing vector (Lead III) was mostly appropriate (53.6%), followed by the primary sensing vector (lead II, 53.1%) and the alternate sensing vector (Lead I, 46.9%). Higher R wave was the major cause, accounted for 70.5%, for screening failure. There existed significant difference in T wave in lead II, aVF, V5 and V6, adds R/T ratio in lead V5 and V6, between the screening success group (group A) and screening failure group (group B) at rest and on exercise. A multivariable logistic regression analysis was performed to identify that R/T ≤ 3.5 in lead V5 was the independent factor to predict the screening ineligibility, with odds ratio 3.648. S-ICD screening success is 50.8% in HCM patients, which is much lower than that in other studies. R/T ≤ 3.5 in lead V5 in 12-lead surface ECG was an independent predicting factor for screening failure.