Physicians Uncover New Ways to Predict the Onset of Life-Threatening Cardiac Arrhythmias
Analysis of ICD recordings can predict spontaneous ventricular tachycardia and ventricular fibrillation in patients

FOR IMMEDIATE RELEASE
Contact: Ann-Marie White
Heart Rhythm Society
(202) 464-3476
awhite@hrsonline.org

A new research method makes it possible to predict the onset of life-threatening ventricular tachycardia (VT) or fibrillation (VF), two life-threatening heart rhythm disturbances that can often lead to sudden cardiac death. The new study is published in the May issue of HeartRhythm, the official journal of the Heart Rhythm Society, and is the first to provide evidence that high-amplitude electrogram T-wave alternans often precedes spontaneous VT/VF in humans, by measuring stored data directly from implantable cardioverter-defibrillators (ICDs).

ICDs are electronic devices implanted in patients at high risk for VT/VF. They deliver electrical pulses to stop VT/VF after it has started. Study findings may permit ICDs to warn patients who are about to have VT/VF and may ultimately permit ICDs to deliver sequences of electrical pacing pulses that prevent the onset of VT/VF.

Characterized by a very fast and abnormal heart rate, VT is a serious condition that warrants immediate treatment and can lead to VF and Sudden Cardiac Arrest (SCA). SCA poses the greatest threat and accounts for half of all cardiac deaths. SCA is a leading cause of death in the US, claiming more than 250,000 lives per year.

T-wave alternans is a measure of cardiac electrical instability. Previous studies have used advanced signal processing techniques to measure T-wave alternans from the routine surface electrocardiogram and predict whether patients are at sufficient long-term risk of VT/VF to warrant implantation of an ICD. Unlike previous studies, the new study led by Charles Swerdlow, MD, FHRS, Cedars Sinai Medical Center in Los Angeles, California, looks for short-term predictors of spontaneous VT/VF using electrical signals recorded from ICD electrodes. These electrodes are wires that are permanently implanted in the heart and attached to the ICD.

This is the first study to measure T-wave alternans in humans directly from ICD recordings. To make these measurements, Swerdlow’s team first had to develop and validate a new simple averaging method, suitable for use in an ICD, to measure T-wave alternans from short segments of ICD electrical signals. “Using this method, we found that high-amplitude T-wave alternans occurs frequently just before the onset of spontaneous VT/VF and only rarely at other times,” said Swerdlow.

Using this new method, T-wave alternans from ICDs can be measured continuously, enabling the detection of high-amplitude T-wave alternans which could be used to predict the onset of VT/VF. According to Swerdlow, the long-term goal of this research is to develop ICD technology that continuously and automatically assesses T-wave alternans for the purpose of warning patients before the onset of VT/VF or even initiating pacing algorithms to prevent VT/VF.

For more information about this study, please visit the HeartRhythm Journal website at www.heartrhythmjournal.com.

About HeartRhythm Journal
HeartRhythm provides rapid publication of the most important science developments in the field of arrhythmias and cardiovascular electrophysiology (EP). As the official journal of the Heart Rhythm Society, HeartRhythm publishes both basic and clinical subject matter of scientific excellence devoted to the EP of the heart and blood vessels, as well as therapy. The journal is the only EP publication serving the entire electrophysiology community from basic to clinical academic researchers, private practitioners, technicians, industry and trainees. HeartRhythm has an Impact Factor of 3.777 and is ranked ninth out of 72 cardiovascular medicine journals by the Institute for Scientific Information. Additionally, the journal ranks sixth in the Immediacy Index among cardiology publications. It is also the official publication of the Cardiac Electrophysiology Society.