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

BACKGROUND

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

CASE SUMMARY: 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.

DISCUSSION: 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.

TAKE-HOME MESSAGES: 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.