Left-dominant Arrhythmogenic cardiomyopathy (LDAC)
Left-dominant Arrhythmogenic cardiomyopathy (LDAC) differs from ARVC in more ways than only predominantly involving the LV. Ventricular arrhythmias of typical ARVC are characterized by LBBB morphology, whereas over 75% of LDAC demonstrated RBBB morphology. Additionally, findings of lateral and/or inferior T wave inversion found in LDAC differ in pattern seen with ARVC which involves anterior T-wave inversion and epsilon waves of the right precordial leads.16 Epsilon waves are low-amplitude positive signals following a QRS complex that arise from prolonged depolarization in the affected part of the myocardium (as shown in our patient, Image 2). On echocardiography, 30% of LDAC patients have LV dilation and/or impairment with preserved RV volume and function. In the classic pattern of ARVC, isolated RV dysfunction precedes LV involvement throughout the disease course. In addition, there is general sparing of the septum in late stage ARVC with LV involvement.17 It is noteworthy that our patient manifested ventricular ectopy with RBBB pattern (a typical characteristic of left ventricular involvement), despite developing an epsilon wave, (which is similarly seen in typical ARVC) along with other features of left sided involvement such as a reduction in left ventricular function and the interval development of left ventricular fibrosis seen on CMR.