# Intrinsicoid Deflection of the QRS Complex Predicts Appropriate Antitachycardia Pacing or Shock Therapy in Heart Failure Patients with an Implantable Cardioverter Defibrillator

## TL;DR

This study finds that a specific electrocardiographic feature called intrinsicoid deflection can predict if heart failure patients with ICDs will need antitachycardia pacing or shocks.

## Contribution

The study identifies intrinsicoid deflection as a novel predictor for appropriate ICD therapy in heart failure patients.

## Key findings

- An intrinsicoid deflection greater than 50 ms predicted ICD therapy with high sensitivity and specificity.
- Intrinsicoid deflection, fragmented QRS, and Selvester score were independent predictors of appropriate ICD therapy.
- Prolonged QRS and QTc intervals were more common in patients who received ICD therapy.

## Abstract

Sudden cardiac death remains a significant risk for patients with heart
failure (HF). Current guidelines recommend implantable cardioverter
defibrillator (ICD) for patients with low left ventricular ejection fraction
(LVEF). However, the effectiveness and necessity of ICDs in patients with
normal LVEF raise questions, especially given associated complications and
costs.

This study aims to evaluate the electrocardiographic predictors of
appropriate ICD therapy (antiTachycardia pacing [ATP]/shocks) in patients
with HF.

We conducted an analysis of 160 consecutive HF patients (New York Heart
Association class I-III, LVEF ≤ 35%) undergoing ICD controls from
January 2023 to December 2024. Patients were classified into two groups
based on the occurrence of appropriate ATP or ICD shocks.
Electrocardiographic parameters including QRS duration, QTc interval,
intrinsicoid deflection (ID), and fragmented QRS (fQRS) were assessed.
Statistical analyses, including receiver operating characteristic curves and
logistic regression, were performed to identify independent predictors of
appropriate ICD therapy.

The ATP/shock group exhibited significantly prolonged QRS and QTc intervals,
increased ID, and higher Selvester scores compared to the non-shock group.
Notably, an ID > 50 ms emerged as a strong predictor of ICD therapy
(sensitivity 96.3%, specificity 95.3%). Univariate and multivariate analyses
identified ID, fQRS, and Selvester score as independent predictors of
appropriate ICD therapy.

Elevated ID, alongside other electrocardiographic parameters, serves as a
valuable predictor for appropriate ICD therapy in HF patients. These
findings support the potential for refining ICD implantation criteria,
emphasizing the importance of detailed electrocardiographic evaluation in
predicting arrhythmic events.