Interesting clinical case...what's the cause?

This is an actual clinical case that attended my hospital. A 40 year old Afro - American man who's usually fit and well suddenly presents with syncope and is found to be in complete heart block. Echo shows structurally normal heart. He is treated with a pacemaker. All is well until 2 years later when he suddenly complains of palpitations and shortness of breath. On arrival to the emergency department he is in sustained monomorphic ventricular tachycardia and is quickly DC cardioverted as haemodynamically compromised. His recovery ECG shows sinus rhythm with ventricular pacing. He has another echo which now shows severely dilated and impaired left ventricular systolic function. A coronary angiogram is performed which shows normal coronary arteries. His pacemaker is upgraded to a bi ventricular icd. Any ideas about the likely underlying cause of his recent onset dilated cardiomyopathy?
Source: Doc2Doc BMJ Cardiology - Category: Cardiology Authors: Source Type: forums