By Joshua D. Moss, MD
Associate Professor of Clinical Medicine, Cardiac Electrophysiology, Division of Cardiology, University of California, San Francisco
Dr. Moss reports no financial relationships relevant to this field of study.
SYNOPSIS: Late-breaking findings of several important clinical trials were presented at this year’s Heart Rhythm Society Scientific Sessions in Chicago. A selection particularly relevant to the general cardiology community is presented here.
SOURCE: Late-Breaking Clinical Trials 1; Late-Breaking Clinical Trials II. Heart Rhythm 2017;14:940-947.
THE S-ICD POST-MARKET APPROVAL STUDY(Gold MR, et al.)
A prospective registry of the totally subcutaneous ICD (S-ICD) was created following FDA approval of the device in 2013. The reported findings included an average of two years of follow-up data for 1,637 patients implanted at 86 U.S. centers, 77% for primary prevention and 23% for secondary prevention. Patients had similar co-morbidities to those typically implanted with a more traditional transvenous ICD: 74% had heart failure with an overall mean ejection fraction of 32%, and 34% had diabetes. Additionally, 13% of patients were on hemodialysis. The device was effective at implant, with successful conversion of induced VT/VF achieved in 98.7% (first shock conversion in 95.6%). There were few complications, with an infection rate of 1.2% and 30-day complication-free rate of 96.2%. Registry follow-up is scheduled to continue to five years for all patients.
The subcutaneous ICD offers an important tool in our armamentarium for treating ventricular arrhythmias, with the advantage of requiring no intravascular hardware (particularly ideal in younger patients and those with more risk factors for infection). Procedural time is similar to that for implanting a single-lead transvenous ICD, and implants can be performed without fluoroscopy. This registry data further affirms the low 30-day complication rate and high rate of defibrillation success at implant. We await important information about “real-world” success rates of terminating clinical arrhythmias, incidence of inappropriate ICD shocks, and proportion of arrhythmias that potentially could be treated with transvenous overdrive pacing rather than a shock.
THE NODE-I TRIAL (Stambler B, et al.)
Etripamil is a short-acting L-type calcium channel blocker with rapid onset of action, designed for intranasal administration and being developed as a self-administered outpatient therapy for paroxysmal supraventricular tachycardia (PSVT). NODE-1 is a Phase II, multicenter, randomized, controlled study of 104 patients undergoing electrophysiology studies. After SVT (AV reentrant tachycardia or AV nodal reentrant tachycardia) was induced and sustained for at least five minutes, either a dose of etripamil ranging from 35-140 mg or placebo was administered intranasally. Conversion rates to sinus were as high as 95% within 15 minutes of administration of the highest dose of etripamil, compared with 35% in the placebo group (mean time to conversion ranged from 2.6-3.4 minutes). Nasal congestion occurred in up to 45% of etripamil patients, compared with 0% who received placebo, and transient second-degree AV block (Mobitz type I) was seen in one patient who received the highest dose of the study drug. There were two cases of hypotension reported as adverse events.
Etripamil eventually may offer a new treatment approach for patients with paroxysmal SVT, particularly those who do not wish to take daily medications or undergo an ablation procedure. The next step will be a trial of patient self-administration to terminate PSVT in the ambulatory setting.
THE POWDER-AF MULTICENTRE RANDOMISED TRIAL (Duytschaever M, et al.)
This three-center randomized trial included patients who underwent a standard pulmonary vein isolation procedure for paroxysmal AF and who continued a previously ineffective antiarrhythmic drug therapy (ADT) for the three-month post-ablation blanking period. Of 153 patients who were free of AF at the end of the blanking period, half were randomly assigned to continue the ADT, and half were told to stop the medication. Assessment of recurrent AF was based on a seven-day Holter monitor and quality of life questionnaires at six and 12 months post-procedure. Sustained atrial arrhythmia was documented in 2.7% of the group on ADT, significantly less than in the group off medication (21.9%; P < 0.001). Patients on continued ADT also had a lower rate of repeat ablations and unscheduled visits; quality-of-life scores were similar.
These findings may have important implications for the clinician managing patients with AF after an ablation procedure, often the cardiologist who originally referred the patient. Continuation of an antiarrhythmic drug for up to one year after the ablation procedure, even if that drug was ineffective at controlling the arrhythmia, resulted in significantly fewer atrial arrhythmias, repeat ablations, and unscheduled visits. Although quality-of-life scores were similar, the potential for reduced cost and burden to the medical system may warrant consideration of this strategy.
THE REVEAL AF STUDY (Reiffel JA, et al.)
In this single-arm, multicenter study, 385 patients with risk factors for AF, CHADS2 score ≥ 3 (or = 2 with an additional risk factor), and no AF detected on ≥ 24 hours of external monitoring received an insertable cardiac monitor (ICM). By 30 days (the longest typical duration of monitoring when using an external device) the incidence of adjudicated AF ≥ 6 minutes was 6.2%. However, that incidence increased to 27.1% by 12 months and 40.0% by 30 months. Oral anticoagulation was prescribed in 56.3%.
Several studies have demonstrated that a higher incidence of AF can be detected with longer-term continuous ambulatory monitoring. In CRYSTAL AF (N Engl J Med 2014;370:2478-2486), an insertable cardiac monitor detected AF in 12.4% of patients with cryptogenic stroke by 12 months, compared with 2.0% of patients undergoing conventional monitoring. The REVEAL AF study went a step further by including all patients with risk factors for AF, not just those with stroke. The authors did not comment on whether any specific risk factor vs. compatible symptoms predicted AF more reliably, nor on what proportion of patients may have been diagnosed otherwise (via symptom-based monitoring or routine screening). Nevertheless, the impressively high incidence of previously undiagnosed AF, which resulted in anticoagulation therapy in the majority of cases, suggests there may be a public health benefit to more rigorous AF screening in high-risk patients. The risks and benefits of anticoagulating asymptomatic patients once AF is detected incidentally by monitoring will require further studies.