Background: Due to suspected pro-arrhythmia and elevated mortality associated with class IC antiarrhythmic drugs (AADs), AAD therapy in structural heart disease (SHD) is often limited to amiodarone. However, its long-term use frequently leads to severe adverse effects. With modern advancements in heart failure therapy and emergence of implantable cardioverter-defibrillators (ICDs), it remains unclear if previous studies still adequately reflect current patient populations. In clinical practice, class IC AADs are occasionally used as a last resort in individual patients, particularly under ICD-protection. Nevertheless, systematic analyses of these cases are sparse. 

 

Methods: This study investigates outcome in ICD-carriers with SHD in whom class IC AADs were used as an individualized therapy due to failure or intolerable risk of other therapy options. Patients were screened at four tertiary care centres based on electronic patient records and included in a retrospective registry. Demographic and clinical baseline parameters as well as the long-term outcome were recorded. Clinical and rhythm-associated endpoints were analysed in a descriptive manner. Continuous variables are reported as median with inter-quartile range (Q1, Q3).

 

Results: Forty-eight patients were included. Median age was 49 years (Q1: 38y; Q3: 65y) and 52% (n=25) were female. The underlying heart disease in the majority of patients was dilated cardiomyopathy (44%) or ischemic heart disease (27%). Other forms of structural heart disease included congenital heart disease (10%), mitral valve prolapse associated with reduced left ventricular ejection fraction (LVEF) (8%) or hypertrophic cardiomyopathy (4%). Median LVEF in this cohort was 45% (Q1:35%; Q3:48%). Flecainide was used in 79% and propafenone in 21% of cases. Indications for AAD were sustained ventricular arrhythmias (VA) (56%), atrial arrhythmias (17%) or PVCs (27%). The majority of patients received concomitant therapy with betablockers (96%), ACE-inhibitors/ARBs (60%) and aldosterone antagonists (52%). 

Median follow-up duration under class IC AAD was 835 days (Q1:195d; Q3: 1864d) with a total follow-up duration of 990 days (Q1: 617d; Q3: 2225d). During follow-up, 73% of patients remained free from sustained VA, 81% of patients were free from ICD-therapy. Freedom from sustained VA was more common in women (12% vs. 43%, P=0.022). In 19 patients (40%) class IC AAD therapy was terminated during follow-up. The most common reason for termination was insufficient efficacy (n=8). Pro-arrhythmia was suspected in 3 patients (6%). Five patients died during follow up (10.4%), 2 of these due to cardiovascular causes (4%).

 

Conclusion: In a cohort of ICD-carriers with SHD, class I AADs were associated with low rates of observed pro-arrhythmia or cardiovascular mortality. The majority of patients remained free from sustained VA and ICD-therapy during a follow-up of >2 years. Further efforts should be made to evaluate safety and efficacy of class IC AADs in SHD in patients receiving modern heart failure therapy under ICD-protection.