Severe atrial fibrosis as a cause of significant intraatrial conduction delay in a patient with scleromyositis.

Scleromyositis is an autoimmune disease and an overlap syndrome of scleroderma and poly/dermatomyositis. It is characterized by frequent cardiovascular involvement including heart failure, arrhythmias and conduction disturbances. We present a case of a 73-year old female patient who required an upgrade from a DDD pacemaker to cardiac resynchronization therapy due left ventricular dysfunction and permanent ventricular pacing. Electroanatomical mapping (CARTO 3D) revealed extensive right atrial fibrosis which resulted in significant delay in intraatrial conduction. Interval from atrial paced stimulus to A signal in His bundle was 364 ms, while AH and HV intervals were within normal range.