Extended vs standard ECG monitoring detects more arrhythmias in HCM

Extended ECG monitoring for 30 days significantly increases the detection rates of arrhythmias compared with the standard 24-hour monitoring period in patients with hypertrophic cardiomyopathy (HCM), according to the TEMPO-HCM study presented at EHRA 2023.

Previous studies have shown that “extended ECG monitoring allows us to detect significantly more arrhythmias … and this may result in better management of these patients,” said lead author Dr Juan Caro Codón from La Paz University Hospital in Madrid, Spain.

However, data “regarding extended ECG in HCM are lacking,” he noted.

Hence, Codón and his team conducted a multicentre, prospective, observational study involving 100 patients (mean age 56.8 years, 78 percent male) who were diagnosed with HCM and had a clinical indication to undergo a conventional ECG Holter monitoring. All participants underwent a 30-day ECG monitoring by using a dedicated device. The primary endpoint of the study was the detection of clinically relevant arrhythmias, including atrial fibrillation (AF) or atrial flutter and nonsustained ventricular tachycardia (NSVT), during the 30-day or first 24-hour monitoring.

According to the findings, there were significantly more relevant arrhythmias detected with the extended 30-day monitoring than during the first 24-hour monitoring (65 percent vs 11 percent; p<0.001). This increased detection of arrhythmias was mainly due to a significantly higher prevalence of NSVT observed in the 30-day vs 24-hour monitoring group (62 percent vs 8 percent; p<0.0001).

“While in most studies, largely using conventional Holter monitoring, the prevalence of NSVT was only observed at 20–30 percent,” said Codón.

Of note, the incidence of NSVT “didn’t reach a plateau during the entire study period. Therefore, there is a possibility that if we continued to monitor these patients, the difference between both monitoring periods may have been even greater,” he noted. “However, caution is needed regarding the significance of NSVT episodes during prolonged ECG monitoring.”

A higher incidence of AF was also seen during the extended monitoring than 24-hour monitoring (10 percent vs 6 percent; p=0.297).

“Although the difference between the two study periods did not achieve statistical significance, that may have been true if the sample size had been larger,” Codón said. “This may be a signal of true benefit for AF screening and our findings justify further research on extended ECG monitoring for this indication.”

In an exploratory analysis, using the HCM Risk-Sudden Cardiac Death (SCD) calculator, the median estimated 5-year risk of SCD was significantly higher in the extended monitoring group than in the 24-hour monitoring group (median, 2.92 percent vs 1.74 percent; p<0.001), which resulted in approximately 20 percent of the patients being potentially reclassified into a higher risk category, Codón noted.

“Overall, clinically meaningful arrhythmias were identified in six times more patients by extended ECG monitoring than by conventional ECG monitoring in non-selected and non-high-risk HCM population,” said Codón.

“It is also important that in this relatively low-risk cohort of HCM patients, the majority of participants have NSVTs, which warrants further investigation, and it also raises questions regarding its true ability to discriminate between high- and low-risk groups of patients for SCD,” Codón added.

“We think that there's a sign here that extended ECG assessment in HCM may have a role in the future. It is a potential topic for research to screen for AF, at least in certain groups of patients,” he noted.