# Beyond Tachycardia-Induced Cardiomyopathy: ABCC9-Related Dilated Cardiomyopathy and Familial Atrial Fibrillation

## TL;DR

A new genetic variant in ABCC9 is linked to heart failure and atrial fibrillation, suggesting a broader genetic role in heart disease beyond typical tachycardia-induced cases.

## Contribution

A novel ABCC9 gene variant is identified as a potential contributor to atrial fibrillation-induced cardiomyopathy, expanding beyond tachycardia-induced cases.

## Key findings

- A likely pathogenic ABCC9 variant (c.3892+2T>C) was found in a patient with atrial fibrillation and dilated cardiomyopathy.
- The ABCC9 variant suggests a genetic basis for AF-induced cardiomyopathy beyond typical tachycardia-induced cases.
- Genetic testing is highlighted as valuable in diagnosing atypical or treatment-resistant heart conditions.

## Abstract

Tachycardia-induced cardiomyopathy (TICM) is typically reversible with rhythm control, but individual susceptibility remains poorly understood and may reflect genetic predisposition.

A 66-year-old woman with paroxysmal atrial fibrillation (AF) presented with new-onset heart failure. Genetic testing identified a likely pathogenic heterozygous ABCC9 gene variant (c.3892+2T>C), not previously associated with dilated cardiomyopathy or AF. ABCC9 loss-of-function mutations have been linked with cardiac channelopathies and cardiomyopathies. Ventricular function improved with rhythm control and medical therapy.

This case illustrates the potential role of ABCC9 mutations in arrhythmia-induced cardiomyopathy beyond pure TICM. Although this variant has not been previously reported in affected individuals, existing models support its pathogenicity. The co-occurrence of prolonged QT, familial AF, and dilated cardiomyopathy underscores the value of genetic testing in cardiac disease.

Genetic testing may reveal causes in atypical or treatment-resistant cardiomyopathies and arrhythmias. This novel ABCC9 variant suggests a genetic contribution to AF-induced cardiomyopathy beyond the expected course of TICM.