Primary Prevention Implantable Cardiac Defibrillators: A Townsville District Perspective

Abstract

Background: Despite major advances in treating patients with severe heart failure, deciding who should receive an implantable cardiac defibrillator (ICD) remains challenging. Objective: To study the risk factors and mortality in patients after receiving an ICD (January 2008-December 2015) in a regional hospital in Australia. Methods: Eighty-two primary prevention patients received an ICD for ischemic cardiomyopathy (ICM, n = 41) and non-ischemic cardiomyopathy (NICM, n = 40) with 4.8-yrs follow-up. One patient had mixed ICM/NICM indications. Ventricular arrhythmias were assessed using intracardiac electrograms. Statistical analysis compared the total population and ICM and NICM groups using Kaplan-Meier for survival, Cox regression for mortality predictors, and binary logistic regression for predictors of ventricular arrhythmias (p < 0.05). Results: Major risk factors were hypercholesterolemia (70.7%), hypertension (47.6%), and obesity (41.5%). Severe obstructive sleep apnea (OSA) was found exclusively in NICM patients (23.7%, p = 0.001). Mortality was 30.5% after 4.8-yrs. The majority of patients (n=67) had no sustained ventricular arrhythmias yet 28% received therapy (n = 23), 18.51% were appropriate (n = 15), and 13.9% inappropriate (n = 11). Patients receiving ≥2 incidences of inappropriate shocks were 18-times more likely to die (p = 0.013). Three sudden cardiac deaths (SCD) (3.7%) were prevented by the ICD. Conclusion: Patients implanted with an ICD in Townsville had 30.5% all-cause mortality after 4.8-yrs. Only 28% of patients received ICD therapy and 13.9% were inappropriate. OSA may have contributed to the fourfold increase in inappropriate therapy in NICM patients. Our study raises important efficacy, ethical and healthcare cost questions about who should receive an ICD, and possible regional and urban center disparities.

Fragmented QRS is associated with ventricular arrhythmias in heart failure patients: A systematic review and meta‐analysis

“…Our analysis also found that the fQRS patients were significantly 1.5 years older than non-fQRS patients and had a 12% increased incidence of diabetes. Multiple studies have shown that age is not a contributing factor to VA in ICD patients (Santangelo et al, 2021), (Bergau et al, 2017), and we and others have found that comorbidities are not often associated with VA or appropriate ICD therapy (Engstrom et al, 2020). While some studies have demonstrated a link between diabetes and VA (Grisanti, 2018), others have reported the opposite (Juhani Junttila et al, 2020), which may be related to HF…”

“…Mortality is most likely a 'systems failure' comprising a weak heart and many underlying comorbid conditions and mechanisms, some of which we have discussed above, and many that are currently unknown (Engstrom et al, 2020). For example, some comorbidities such as obstructive sleep apnea predispose patients inappropriate ICD therapy, which may increase mortality risk (Engstrom et al, 2020).…”

“…Mortality is most likely a 'systems failure' comprising a weak heart and many underlying comorbid conditions and mechanisms, some of which we have discussed above, and many that are currently unknown (Engstrom et al, 2020). For example, some comorbidities such as obstructive sleep apnea predispose patients inappropriate ICD therapy, which may increase mortality risk (Engstrom et al, 2020). It would be interesting to know whether these patients more likely to developed fQRS and their clinical implications after ICD placement, and these data should be included in future studies.…”

“…Primary prevention ICDs protect HF patients against ventricular arrhythmias that cause SCD. However, a number of studies show that up to 80% of ICD patients never experience sustained arrhythmias (Engstrom et al, 2020 ), suggesting the current guidelines about who should receive a device may need refinement (Disertori et al, 2020 ). New criteria are required to identify patients who are at risk for VA and require an implantable device.…”

Obstructive Sleep Apnea and Cardiac Arrhythmias: A Contemporary Review

“…OSA has been implicated as a contributor to secondary rhythm-related complications of other cardiovascular diagnoses, including myocardial infarction and heart failure [71,72]. Among patients with permanent pacemakers that are largely implanted for sinus or AV nodal diseases, the prevalence of previously unrecognized OSA is quite high, raising the question of whether appropriate OSA treatment might have resulted in fewer device implants [73]. In patients with non-ischemic cardiomyopathies who have implanted cardiac defibrillators for the primary prevention of sudden death, OSA has been associated with an increased rate of inappropriate shocks [74].…”