OBJECTIVE: The purpose of this study was to evaluate the genetic basis of myocarditis in ARVD and to investigate the association with a poorer prognosis and a higher risk of ventricular arrhythmias.
METHODS: Two groups were analyzed: group A, which consisted of 131 affected patients-84 with ARVD (62% male, age 45 years [range 33-55 years]) and 47 with left-sided forms (arrhythmogenic left ventricular dysplasia [ALVD]) (47% male, age 45 years [range 25-61 years]); and group B, which consisted of 64 nonaffected mutation-carrying relatives (36% male, age 42 years [range 22-56 years]; 23 from classic ARVD families and 41 from ALVD families).
RESULTS: Seven patients (3.5%) presented with a clinical diagnosis of acute myocarditis over median follow-up of 34 months. Myocarditis was the first clinical presentation in 6 of 7 cases. In 2 patients, acute myocarditis preceded worsening of left ventricular systolic function. In 1 case, myocarditis was associated with an increased gadolinium pattern in cardiac magnetic resonance. Two patients presented with ECG changes weeks after myocarditis resolution. Myocarditis preceded the development of ventricular tachycardia in 2 other patients. Myocarditis clustered in families bearing DSP Q447* and LDB3 c.1051A>G.
CONCLUSIONS: Acute myocarditis reflects an active phase of ARVD that leads to changes in phenotype and abrupt progression of the disease. An active phase should be suspected in a patient with myocarditis associated with a family history of ARVD. Certain mutations may increase the susceptibility to superimposed myocarditis in ARVD.