Related Experiment Video
Updated: Jun 22, 2025
Determining the Likelihood of Variant Pathogenicity Using Amino Acid-level Signal-to-Noise Analysis of Genetic Variation
Published on: January 16, 2019
Exercise-Induced QRS Prolongation in Brugada Syndrome: Implications for Improving Disease Phenotyping and Diagnosis
Praloy Chakraborty1, Mahbod Rahimi2, Adrian M Suszko2
1Division of Cardiology, Peter Munk Cardiac Center, University Health Network, Toronto, Ontario, Canada; Heart Rhythm Institute, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma, USA.
Background:
Abnormal ventricular activation at rest is reported in Brugada syndrome (BrS).
Objectives:
The aim of this study was to evaluate the usefulness of dynamic changes in ventricular activation during exercise to improve disease phenotyping and diagnosis of BrS.
Methods:
Digital 12-lead electrocardiograms during stress testing were analyzed retrospectively at baseline, peak exercise, and recovery in 53 patients with BrS and 52 controls. Biventricular activation was assessed from QRS duration (QRSd), whereas right ventricular activation was assessed from S wave duration in the lateral leads (I and V6) and terminal R wave duration in aVR. Exercise-induced changes in QRS parameters to predict a positive procainamide response were assessed in separate test and validation cohorts with suspected BrS.
Results:
Baseline electrocardiogram parameters were similar between BrS and controls. QRSd shortened with exercise in all controls but prolonged in all BrS (-6.1 ± 6.0 ms vs 7.1 ± 6.5 ms [P < 0.001] in V6). QRSd in recovery was longer in BrS compared with controls (90 ± 12 ms vs 82 ± 11 ms in V6; P = 0.002). Both groups demonstrated exercise-induced S duration prolongation in V6, with greater prolongation in BrS (8.2 ± 14.3 ms vs 1.2 ± 12.4 ms; P < 0.001). Any exercise-induced QRSd prolongation in V6 differentiated those with a positive vs negative procainamide response with 100% sensitivity and 95% specificity in the test cohort, and 87% sensitivity and 93% specificity in the validation cohort.
Conclusions:
Exercise-induced QRSd prolongation is ubiquitous in BrS primarily owing to delayed right ventricular activation. This electrocardiogram phenotype predicts a positive procainamide response and may provide a noninvasive screening tool to aid in the diagnosis of BrS before drug challenge.
Related Concept Videos
01:29Electrocardiogram
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...
01:30Cardiac Action Potential
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
01:16ECG Interpretation of Arrhythmias I: Sinus Arrhythmias
Types of Arrhythmias
Sinus Node Arrhythmias
Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism,...
01:26Exercise Stress Test
Exercise stress testing, commonly known as a treadmill test, is a noninvasive procedure used to evaluate cardiovascular function and diagnose heart conditions.
Definition
An exercise stress test measures the heart's response to exertion using a treadmill or stationary bicycle. Chest electrodes record the heart's electrical activity through an ECG, and blood pressure is monitored regularly.
Purposes
01:14Decreased pulse rate
There are specific risk factors that can elevate the likelihood of developing bradycardia. Advanced age is a significant factor, with...
01:24Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers