Changing Risk Stratification in Hypertrophic Cardiomyopathy?

Patients with hypertrophic cardiomyopathy (HCM) must be assessed using a 24- or 48-hour Holter monitor at least every 2 years to identify atrial fibrillation (AFib) or nonsustained ventricular tachycardia (NSVT). An AFib diagnosis calls for full anticoagulation, because the risk of cerebrovascular events is exceptionally high (making the use of additional clinical scores, such as CHA₂DS₂-VASc and ATRIA, redundant). NSVT detection is part of the current risk stratification model and, according to the latest guidelines, makes a patient eligible for an implantable cardioverter defibrillator (ICD). The level of evidence in favor of an ICD after NSVT detection in adults is class IIb. For patients younger than 16 years, this diagnosis has greater prognostic weight, and the level of evidence supporting the benefit of an ICD is higher (class IIa).

At this year’s European Heart Rhythm Association Congress, Juan Caro Codón, MD, a cardiologist affiliated with the La Paz University Hospital in Spain, presented the TEMPO-HCM study. A total of 100 patients were included in the study. The average age was 57 years, and 22% were women. Patients with HCM phenocopies or an ICD were excluded. Participants underwent extended ECG monitoring for 30 days using a dedicated device. Extended monitoring detected almost five times more cases of NSVT. The comparison was made between the number of detections observed during the first 24 hours of monitoring (simulating conventional 24-hour Holter monitoring) vs the whole 30-day period.

Extended ECG monitoring detected a higher incidence clinically relevant arrhythmias than 24-hour monitoring: 65% vs 11% (P < .001). Patients who developed NSVT during the first 24 hours had different electrophysiologic characteristics than those who did not develop NSVT. Their tachycardias during the whole monitoring period were faster (174 vs 152 bpm; P = .001), longer (14 vs 8 beats; P = .029), and more frequent (11 vs two episodes; P < .001). Monitoring using a 24-hour Holter monitor may allow for detection of patients who are more electrophysiologically unstable. What is not known, however, is how to use this information in clinical practice. If NSVT diagnosis with extended monitoring is applied to the 5-year risk for sudden cardiac death, according to the European Society of Cardiology HCM Risk-SCD calculator, then patients are reclassified to a higher risk category. The calculator detected NSVT (beats faster than 120 bpm) as an independent risk factor. In Codón’s study, the median estimated 5-year risk for sudden cardiac death was 1.74% using data from the first 24 hours, vs 2.92% using extended monitoring data (P < .001), resulting in 13 (14.4%) additional patients for whom an ICD may be considered, and seven (7.8%) additional patients for whom an ICD should be considered.

Regarding AFib, extended monitoring detected four more cases than 24-hour monitoring, including three cases in which the patient had not been previously diagnosed with this arrhythmia. This may be a signal of true benefit for AFib screening, and the findings justify further research on extended ECG monitoring for this indication.

Although extended monitoring may not seem feasible initially, I have already seen patients with AFib and a patient with NSVT whose conditions were identified by a smartwatch. We are living in the era of wearables that record blood volume variations, from which heart rate and other physiologic parameters can be extracted to inform about user health.

Being able to detect these arrhythmias more often will have an impact on our patients and us. We will have a significant increase in indications for prophylaxis with an ICD and anticoagulation, whether to prevent sudden death or embolic events. These indications will be justifiable to start with, but we will need to reassess the actual prognostic weight for indicating procedures in a context that has not yet been foreseen in clinical studies. AFib ablation seems to play a role in reducing the risk of embolic events, but today, its main roles are in improving quality of life and reducing symptoms and new hospitalizations. What are we to do with the thousands of asymptomatic events that are uncovered every day? Do we have studies to deal with this? No. But I do hope we will have some soon.

This article was translated from the Medscape Portuguese Edition.

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