Conference Coverage

Surprisingly more nonsustained VT shown in HCM using extended ECG monitoring



Clinically important arrhythmias, especially nonsustained ventricular tachycardia (NSVT), may be more prevalent in patients with hypertrophic cardiomyopathy (HCM) than widely believed, suggests a study that questions current risk stratification practices in HCM.

In the registry study, such arrythmias were observed in about six times as many HCM patients during 30 days of ambulatory electrocardiographic monitoring as would have been identified based on the first 24 hours of the monitoring period: 65% vs. 11% of the cohort.

Also, about 62% of the patients showed NSVT at “extended” 30-day monitoring, compared with an 8% prevalence of the arrhythmia based on the more conventional ECG monitoring period of 24 hours.

Nonsustained ventricular tachycardia, an important arrhythmia used every day in clinical practice to make decisions, is “much, much more prevalent than we thought” in patients with HCM, Juan Caro Codón, MD, the study’s principal investigator, said in an interview. “We should invest in further research regarding extended ECG monitoring in these patients.”

Dr. Caro Codón, of La Paz University Hospital, Madrid, presented the findings from the TEMPO-HCM study at the European Heart Rhythm Association 2023 Congress, held in Barcelona and virtually.

Its results, he said, have implications for stratifying HCM patients according to their risk for sudden cardiac death in deciding who should be offered an implantable cardioverter-defibrillator (ICD).

The life-incidence of atrial fibrillation (AF) in patients like those in the current analysis has previously been found to be about 20%, and the life-prevalence of NSVT about 20%-30%, using traditional 24- or 48-hour Holter monitoring, Dr. Caro Codón said.

“These arrhythmias are clinically relevant events because they are linked to very meaningful clinical endpoints,” including stroke and thromboembolism, he said, “but also for sudden cardiac death.”

Extended ECG monitoring has been shown useful in the setting of cryptogenic stroke and after AF ablation, but similar findings have been scarce in HCM. Patients using personal wearable monitors such as smart watches, Dr. Caro Codón said, have come to his clinic with concerns that the devices may have signaled a problem. But the lack of relevant data leaves them without a sufficient answer.

In other findings, invited discussant Isabelle van Gelder, MD, PhD, observed after Dr. Caro Codón’s presentation that the number of patients with AF almost doubled based on extended monitoring, compared with the first 24 hours of monitoring.

Based on European Society of Cardiology guidelines from 2020, “Once clinical AF has been documented, there is a class IIA recommendation to start anticoagulation,” said Dr. van Gelder, University of Groningen, the Netherlands. “Therefore, your data really are a call for more data on screening for AF in hypertrophic cardiomyopathy patients.”

Prospective multicenter registry

The TEMPO-HCM registry includes patients with HCM and a clinical indication for standard Holter monitoring at five hospitals in Spain. It excludes patients with an HCM-like phenotype but who lack the telltale genotype, as well as those already implanted with an ICD.

Those in the current analysis underwent 30-day ECG monitoring with a small, wearable device that Dr. Caro Codón described as about 7 cm long, worn in what is essentially a T-shirt with a pocket. Patients could remove the shirt and device to bathe or go swimming, for example, and still be monitored for most of the day.

The analysis included the registry’s first 100 patients (mean age, 57 years; 78% male). Hypertension was present in 47%, 58% were on beta-blockers, 16% had prior AF or atrial flutter, and 19% were taking anticoagulants. Only 8% were on antiarrhythmic drugs, Dr. Caro Codón reported.

The patients had good functional status (68% and 29% were in NYHA class 1 and 2, respectively) and their left ventricular ejection fraction averaged 66%. Of the 71 patients who underwent MRI, 28.2% showed late gadolinium enhancement suggesting myocardial scarring.


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