The Wearable Cardioverter/Defibrillator - Toy Or Tool?

Abstract

After the success story of implantable cardioverter/defibrillator systems, prevention of sudden cardiac death (SCD) remains one of the main duties in cardiology. For patients with unkown or transient risk profile for SCD, a wearable cardioverter/defibrillator (WCD) has been established for temporary and effective prevention of sudden arrhythmic death. Several studies have shown safety and efficacy of the WCD, even though randomized studies proving a mortality benefit are still lacking. This review provides an overview of actual WCD data and usage, special indications and possible risks and complications. WCD use is effective and adequate for temporary prevention of SCD in chosen populations. In particular, it provides secured time for sophisticated risk stratification to identify patients at persistent risk for SCD. Nevertheless, prospective randomized trials seem mandatory to prove a prognostic relevance and the economic value of this device.

Keywords: Sudden Cardiac Death; Ventricular Arrhythmia; Wearable Cardioverter/Defibrillator.

Figure 1. Wearable Cardioverter Defibrillator (WCD)

Figure 2. ECG shows normal sinus rhythm with T wave oversensing. The patient did not press the response buttons and therefore received an inappropriate therapy. Fortunately, the shock was triggered to the true R-wave

Figure 3. Episode of a patient with dilative cardiomyopathy. Patient fell on the floor and remained unconscious. ECG shows ventricular tachycardia that was adequately detected and WCD shock was delivered. After WCD shock, the patient remained unconscious and developed irregular ventricular rhythm going along with some noising leading to oversensing and delivery of another – inappropriate – WCD shock

Figure 4. Spontaneous ventricular fibrillation (VF) occurred in this patient with peripartum cardiomyopathy. Amplitude of VF rapidly decreased followed by myopotentials (black arrow) which were possibly linked to hypoxia-related seizures. Due to this high-frequency lowamplitude signals, VF criteria were no longer satisfied and detection was cancelled (white arrows). VF was redetected several more times. Probably due to some increase in VF amplitude, VF was finally redetected and the life-saving shock was successfully applied 80 seconds after onset of the tachycardia

Figure 5. Workflow of the Wearable Cardioverter/Defibrillator (WCD) program at Hannover Medical School (GP: general practitioner, EF: left ventricular ejection fraction)