Wearable cardioverter defibrillator has little effect on sudden death incidence after acute MI
The use of a non-invasive, wearable cardioverter defibrillator (WCD) in addition to medical therapy did not significantly reduce the incidence of sudden and non-sudden death within 3 months of an acute myocardial infarction (MI), results from the VEST* trial show.
“We did not show a significant reduction in sudden death mortality in the WCD arm nor in non-sudden death,” said Professor Jeffrey Olgin from the University of California, San Francisco School of Medicine, San Francisco, California, US, who presented the results at ACC.18.
In this trial conducted at 109 sites in the US, Germany, Poland, and Hungary, 2,302 patients within 7 days of discharge from hospital following an acute MI and with an ejection fraction ≤35 percent were randomized to receive guideline-based medical therapy alone (n=778, mean age 61.4 years, 74.7 percent male) or in addition to using a WCD (n=1,524, mean age 60.9 years, 72.8 percent male). Patients were followed up for a mean 84.3 days and patients randomized to the WCD arm wore the device for an average 14.1 hours per day.
The WCD is an interchangeable garment equipped with self-gelling defibrillation and dry ECG electrodes, and an attachable rechargeable monitor and battery pack. It monitors for ventricular tachyarrhythmias and can automatically deliver up to four 150 Joule shocks.
Compared with medical therapy only, use of the WCD was associated with nonsignificant reductions in the incidence of sudden death and ventricular tachyarrhythmia death (p=0.18) and in the incidence of non-sudden death (p=0.14) at 90 days. [ACC.18, abstract 18-LB-17834-ACC]
There was a significant improvement noted in the pre-specified secondary endpoint of total mortality at 90 days (death from any cause) favouring the WCD arm compared with the medical therapy only arm (relative risk reduction, 35.5 percent; p=0.04).
Shortness of breath was more commonly reported among patients on medical therapy only (45.4 percent vs 38.7 percent; p=0.003), while rash and itch on the torso were more common among patients using the WCD compared with medical therapy only (12.9 percent vs 3.8 percent and 14.5 percent vs 3.1 percent; p<0.001 for each comparison).
“[T]he guidelines for [implantable cardioverter defibrillator (ICD)] implantation after an MI recommend patients wait 40–90 days before being evaluated for ICD implantation,” said Olgin.
“Therefore, despite the high rate of sudden death early post-MI, ICD implantation is currently not indicated during this period … Due to the high mortality during this period, we are left with a gap in the therapy to prevent sudden death,” he said.
“[W]e found that about half the patients improved their [ejection fraction] but half didn’t, so the expectation is that half the patients will go on to get ICD 40–90 days post-MI,” said study co-author Dr Byron Lee from the University of California, San Francisco.
ACC commentators Dr Peter Block and Professor Anthony DeMaria suggested potential reasons behind the findings, including a psychological effect and higher chance of physician consult among patients wearing the WCD.
“If people … have this device on, they have a sense that if something funny is happening, they’ll go to their doctor more quickly,” said Block, highlighting that this may help doctors pick up other potential causes of mortality.
“In my experience, there is a psychological benefit in patients [in whom] I’ve used the vest and they go home and feel a little bit better [or safer] and … you’re getting a benefit in overall reduction even though we may not be sure exactly why,” said DeMaria.
Potential compliance issues?
Patient compliance in the WCD group reduced from 81 percent of the participants wearing the WCD daily in the period after randomization to 48 percent at 90 days follow up. However, patients who were compliant wore the WCD for an average 22.4 and 21 hours at study onset and at 90 days, respectively.
According to Lee, shared decision making may help physicians identify which patients would be more likely to be compliant.
Despite the findings, guest commentator Professor Dhanunjaya Lakkireddy from the University of Kansas Medical Center, Kansas City, US did not completely discount the use of an external defibrillator, and recommended more studies with a higher level of compliance to assess the use of the device.