Ventricular Arrhythmias Among Patients With Advanced Heart Failure: A Population‐Based Study

Background The epidemiology of ventricular arrhythmias (VAs) in patients with advanced heart failure (HF) is not well defined. Methods and Results Residents of Olmsted County, Minnesota, with advanced HF from 2007 to 2017 were identified using the 2018 European Society of Cardiology criteria. Billing codes were used to capture VAs; severe VAs requiring emergency care were defined as events associated with emergency department visits or hospitalizations. The cumulative incidence of VAs postadvanced HF was estimated with the Kaplan–Meier method. Multivariable Cox analyses were used to determine the following: (1) Predictors of severe VAs postadvanced HF; and (2) Impact of severe VAs on mortality. Of 936 patients with advanced HF, 261 (27.9%) had a history of VA. The 1‐year cumulative incidence of severe VAs postadvanced HF was 5.4%. Prior VAs (hazard ratio [HR] 2.22 [95% CI, 1.26–3.89], P =0.006) and left ventricular ejection fraction <40% (HR, 3.79 [95% CI, 1.72–8.39], P <0.001) were independently associated with increased severe VA risk postadvanced HF. New‐onset severe VAs were associated with increased mortality (HR, 4.41 [95% CI, 2.80–6.94]; P <0.001), whereas severe VAs in patients with prior VAs had no significant association with mortality risk (HR, 1.08 [95% CI, 0.65–1.78]; P =0.77). Severe VAs were associated with increased mortality in patients without implantable cardioverter defibrillators (HR, 4.89 [95% CI, 2.89–8.26]; P <0.001), but not in patients with implantable cardioverter defibrillators (HR, 1.42 [95% CI, 0.92–2.19]; P =0.11). Conclusions Patients with left ventricular ejection fraction <40% and prior VAs have increased risk of severe VA postadvanced HF. New‐onset severe VAs or severe VAs without implantable cardioverter defibrillators postadvanced HF are associated with increased mortality.

CIED guideline recommendations in the setting of advisories

Subcutaneous implantable cardioverter defibrillators (S-ICDs) are currently indicated for patients who meet ICD implantation criteria for the prevention of sudden cardiac death (SCD). In December 2020, a unique cardiac implantable electronic device (CIED) situation arose as both the S-ICD generator and electrode were under a device advisory. We would recommend all future CIED implantation guidelines receive a caveat regarding checking current CIED advisories, in order to avoid future similar scenarios.

Efficacy and Complications of Subcutaneous versus Conventional Cardioverter Defibrillators: A Systematic Review and Meta-Analysis

Background/Objectives: Implantable cardioverter defibrillators are used to prevent sudden cardiac death. The subcutaneous implantable cardioverter defibrillator was newly developed to overcome the limitations of the conventional implantable cardioverter defibrillator-transvenous device. The subcutaneous implantable cardioverter defibrillator is indicated for young patients with heart disease, congenital heart defects, and poor venous access, who have an indication for implantable cardioverter defibrillator without the need for anti-bradycardic stimulation. We aimed to compare the efficacy and complications of subcutaneous with transvenous implantable cardioverter defibrillator devices. Methodology: A systematic review was conducted using different databases. The inclusion criteria were observational and clinical randomized trials with no language limits and no publication date limit that compared subcutaneous with transvenous implantable cardioverter defibrillators. The selected patients were aged > 18 years with complex ventricular arrhythmia. Results : Five studies involving 2111 patients who underwent implantable cardioverter defibrillator implantation were included. The most frequent complication in the subcutaneous device group was infection, followed by hematoma formation and electrode migration. For the transvenous device, the most frequent complications were electrode migration and infection. Regarding efficacy, the total rates of appropriate shocks were 9.04% and 20.47% in the subcutaneous and transvenous device groups, respectively, whereas inappropriate shocks to the subcutaneous and transvenous device groups were 11,3% and 10,7%, respectively. Conclusion: When compared to the transvenous device, the subcutaneous device had lower complication rates owing to lead migration and less inappropriate shocks due to supraventricular tachycardia; nevertheless, infection rates and improper shocks due to T wave oversensing were comparable for both devices

Microvolt QRS Alternans in Hypertrophic Cardiomyopathy: A Novel Risk Marker of Late Ventricular Arrhythmias

Background Unlike T‐wave alternans (TWA), the relation between QRS alternans (QRSA) and ventricular arrhythmia (VA) risk has not been evaluated in hypertrophic cardiomyopathy (HCM). We assessed microvolt QRSA/TWA in relation to HCM risk factors and late VA outcomes in HCM. Methods and Results Prospectively enrolled patients with HCM (n=130) with prophylactic implantable cardioverter‐defibrillators underwent digital 12‐lead ECG recordings during ventricular pacing (100–120 beats/min). QRSA/TWA was quantified using the spectral method. Patients were categorized as QRSA+ and/or TWA+ if sustained alternans was present in ≥2 precordial leads. The VA end point was appropriate implantable cardioverter‐defibrillator therapy over 5 years of follow‐up. QRSA+ and TWA+ occurred together in 28% of patients and alone in 7% and 7% of patients, respectively. QRSA magnitude increased with pacing rate (1.9±0.6 versus 6.2±2.0 µV; P =0.006). Left ventricular thickness was greater in QRSA+ than in QRSA− patients (22±7 versus 20±6 mm; P =0.035). Over 5 years follow‐up, 17% of patients had VA. The annual VA rate was greater in QRSA+ versus QRSA− patients (5.8% versus 2.0%; P =0.006), with the QRSA+/TWA− subgroup having the greatest rate (13.3% versus 2.6%; P <0.001). In those with <2 risk factors, QRSA− patients had a low annual VA rate compared QRSA+ patients (0.58% versus 7.1%; P =0.001). Separate Cox models revealed QRSA+ (hazard ratio [HR], 2.9 [95% CI, 1.2–7.0]; P =0.019) and QRSA+/TWA− (HR, 7.9 [95% CI, 2.9–21.7]; P <0.001) as the most significant VA predictors. TWA and HCM risk factors did not predict VA. Conclusions In HCM, microvolt QRSA is a novel, rate‐dependent phenomenon that can exist without TWA and is associated with greater left ventricular thickness. QRSA increases VA risk 3‐fold in all patients, whereas the absence of QRSA confers low VA risk in patients with <2 risk factors. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02560844.