Complete right bundle branch block and QRS-T discordance can be the initial clue to detect S-ICD ineligibility

Abstract

There are no differences in eligibility of S-ICD among types of cardiac diseases. CRBBB and QRS-T discordance were independent predictors for ineligibility.

A case of frequent and inappropriate shock with a subcutaneous implantable cardioverter-defibrillator triggered by newly developed complete right bundle branch block

“…From a previous report, 19% of potential patients for S-ICD were considered unsuitable for S-ICD when evaluated with a surface ECG screening template, and CRBBB and QRS-T discordance in the I, II, and aVF leads with a standard 12-lead ECG are known to be independent predictors for a failed S-ICD indication. 5 QRS-T discordance was defined as oppositely oriented vectors of QRS and T-wave vectors. 5 In this case, his 12-lead ECG showed CRBBB and QRS-T discordance in the I, II, and aVF leads.…”

“…However, after 4 years, the S-ICD began frequently delivering shocks while the patient was conscious. The 12-lead ECG showed newly developed intermittent CRBBB, indeterminate axis, and QRS-T discordance in I, II, and aVF leads (QRS-T discordance is defined as oppositely oriented vectors of QRS and T wave 5 ) ( Figure 1B ). Chest radiograph showed no obvious S-ICD lead displacement.…”

A case of pseudo-appropriate shock

“…Given this patient's baseline bundle branch block, preoperative screening measures should have been performed to determine whether double counting of a wide QRS complex would result in inappropriate detection. 12 Ultimately, inappropriate detection of a slower VT with double counting led to an appropriate therapy, terminating tachycardia ( Figure 3). In order to avoid therapy during episodes of slow hemodynamically tolerated VT, sensing vectors can be analyzed during VT during electrophysiologic study.…”

SMART pass will prevent inappropriate operation of S‐ICD

“…All 102 vectors from 34 patients were assessed for S‐ICD eligibility using supine and standing ECG limb lead recordings which simulate the three S‐ICD sensing vectors (primary, secondary, and alternate), as reported previously . All ECG readings were analyzed by two independent blinded observers.…”