**3. Guidelines for the WCD**

The American College of Cardiology, American Heart Association, and European Society of Cardiology (ACC/AHA/ESC) 2006 guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death was the first society-based recommendation for the use of WCD in patients at transient high risk for VF, such as patients waiting for heart transplant; patients at high risk following an acute myocardial infarction or invasive cardiac procedure; and patients whose ICD had to be temporarily explanted, for example, because of an infection [7]. The International Society for Heart and Lung Transplantation

with reduced ejection fraction after a myocardial infarction (with or without revascularization) may benefit from WCD use in weeks to months until recovery [11]. Many patients who might be potential WCD candidates are not routinely included in clinical trials, and the HRS/ACC/AHA Expert Consensus Statement of 2014 suggested that the WCD may be considered as a "bridge to ICD" in certain patients [12]. The following year, in 2015, ESC guidelines suggested that the WCD might be used in patients with transiently impaired LV function, naming certain specific conditions such as myocardial infarction, peripartum cardiomyopathy, and myocarditis, and in patients awaiting heart transplantation or a left ventricular assist

In 2016, the AHA issued a science advisory about the WCD which was endorsed by the HRS [14]. Among their key concepts: they viewed the WCD as a temporary means for preventing arrhythmic death without the need of bystander response; despite limited evidence from randomized controlled trials, observational data support the notion that the WCD can detect and terminate ventricular tachyarrhythmias; and the use of a WCD is reasonable when there is a clear ICD indication and a current, transient contraindication to ICD implantation. According to this advisory, the role of a WCD is less clear when the risk of arrhythmias is transient, but a WCD still may be appropriate. The most controversial use of the WCD is in patients in the early recovery phase after myocardial infarction or with a newly diagnosed form of nonischemic cardiomyopathy. Many of these patients will not need a permanent ICD but will experience a period of time when they are at increased risk of SCD.

Evidence for use of the WCD was C-level (expert opinion) and may be

temporarily prevents implantation (Class IIa).

heart transplant (Class IIa).

• The use of WCD is reasonable when there is an indication for an ICD, but a transient contraindication or interruption in ICD care (such as infection)

• The use of WCD is reasonable as a bridge to more definitive therapy, such as

• The use of WCD may be reasonable if there is concern about an elevated SCD risk that is expected to resolve over time or with treatment, for example, ischemic heart disease following revascularization or nonischemic cardiomyopathy being initiated on guideline-directed medical therapy

• The WCD may be appropriate as a bridge therapy when patients are at elevated risk for SCD in cases where an ICD would reduce the risk of SCD but not improve overall survival, such as within 40 days following acute myocardial

• WCDs should not be used when the risk for potentially life-threatening nonarrhythmic causes is expected to exceed the risk of ventricular arrhythmias, especially in those situations where longevity is not expected to exceed

There are many observational studies about the use of the WCD, but to date only one large randomized clinical trial has been published, the Vest Prevention of Early

device [13].

*The Wearable Cardioverter-Defibrillator DOI: http://dx.doi.org/10.5772/intechopen.90663*

summarized as:

(Class IIb).

infarction (Class IIb).

6 months (Class III).

**67**

**4. Clinical trials and other evidence**

#### **Figure 3.**

*Report from the WCD about a tachycardia that was detected but did not require therapy delivery.*

guidance made the WCD a Class I indication for Status 18 patients awaiting transplant at home [8]. In 2009, the Heart Rhythm Society expert consensus recommended that the WCD be considered as an alternative treatment for patients who needed early ICD revision following device explant in the setting of suspected continuing infection [9]. In 2013, the ACC/AHA guideline stated that the utility of the WCD in high-risk patients in the first 4 to 6 weeks after myocardial infarction was being investigated [10]. The European Heart Rhythm Association, Heart Rhythm Society, and Asia Pacific Heart Rhythm Society (EHRA/HRS/APHRS) Expert Consensus on Ventricular Arrhythmias stated that patients with heart failure

#### *The Wearable Cardioverter-Defibrillator DOI: http://dx.doi.org/10.5772/intechopen.90663*

with reduced ejection fraction after a myocardial infarction (with or without revascularization) may benefit from WCD use in weeks to months until recovery [11]. Many patients who might be potential WCD candidates are not routinely included in clinical trials, and the HRS/ACC/AHA Expert Consensus Statement of 2014 suggested that the WCD may be considered as a "bridge to ICD" in certain patients [12]. The following year, in 2015, ESC guidelines suggested that the WCD might be used in patients with transiently impaired LV function, naming certain specific conditions such as myocardial infarction, peripartum cardiomyopathy, and myocarditis, and in patients awaiting heart transplantation or a left ventricular assist device [13].

In 2016, the AHA issued a science advisory about the WCD which was endorsed by the HRS [14]. Among their key concepts: they viewed the WCD as a temporary means for preventing arrhythmic death without the need of bystander response; despite limited evidence from randomized controlled trials, observational data support the notion that the WCD can detect and terminate ventricular tachyarrhythmias; and the use of a WCD is reasonable when there is a clear ICD indication and a current, transient contraindication to ICD implantation. According to this advisory, the role of a WCD is less clear when the risk of arrhythmias is transient, but a WCD still may be appropriate. The most controversial use of the WCD is in patients in the early recovery phase after myocardial infarction or with a newly diagnosed form of nonischemic cardiomyopathy. Many of these patients will not need a permanent ICD but will experience a period of time when they are at increased risk of SCD. Evidence for use of the WCD was C-level (expert opinion) and may be summarized as:

