Complexities of Genetic Testing in Familial Dilated Cardiomyopathy

A 59-year-old female with a personal and family history of dilated cardiomyopathy (DCM) was referred by her cardiologist for genetic testing and counseling. The patient was initially diagnosed with DCM after presenting with dyspnea and fatigue. Her symptoms also included mild bilateral pedal edema, but she denied orthopnea, paroxysmal nocturnal dyspnea, palpitations, presyncope, or syncope. An electrocardiogram showed sinus rhythm and a left bundle branch block morphology (Figure 1). She underwent a gadolinium-enhanced cardiac magnetic resonance imaging that showed an enlarged left ventricle (LV; internal diameter at end diastole and systole were 6.5 cm and 5.4 cm, respectively), and the LV ejection fraction was ≈25%. Abnormal septal wall motion consistent with a bundle branch block was noted. All other walls of the LV were diffusely hypokinetic. Mild midmyocardial hyperenhancement suggestive of idiopathic DCM was present. The right ventricle was normal in size and function. There were no valvular abnormalities. Left heart catheterization showed no significant epicardial coronary artery disease. She was treated with a β-adrenergic antagonist, an angiotensinogen inhibitor, a mineralocorticoid antagonist, and a loop diuretic. Her symptoms improved; however, the LV remained enlarged and had poor systolic function with an ejection fraction of ≈30%. She subsequently underwent biventricular implantable cardioverter-defibrillator implantation. Figure 1. ECG of proband. Heart rate (HR) in bpm, P–R interval (PR) in milliseconds (ms), QRS duration (QRS) in ms, Q–T interval (QT) in ms, and corrected Q–T interval using Bazett formula (QTc) in ms are shown. aVF indicates augmented vector foot; aVL, augmented vector left; and aVR, augmented vector right. At the time of her initial diagnosis, the patient’s family history was notable for a 86-year-old mother who had atrial fibrillation and valvular heart disease; a father who died at the age of 89 years with coronary artery disease; a 59-year-old sister who had hypertension; a 50-year-old brother …