Metastatic Melanoma Presenting as Multiple Cardiac Masses: The Critical Role of Endomyocardial Biopsy

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 role of ABCC9 mutations in arrhythmia-induced cardiomyopathy beyond pure TICM. This variant has not been previously reported in individuals with this condition. The co-occurrence of prolonged QT interval, familial AF, and dilated cardiomyopathy underscores the value of genetics in cardiac disease.

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