Single-loop Macroreentry in the Left Atrium in an “Atrial Cardiomyopathy”: Discrimination between Right and Left Circuits and the Paradox of Proximal-to-distal Coronary Sinus Activation in a Left-sided Arrhythmia

Abstract

This is a 44-year-old female patient with an initial form of familiar cardiomyopathy characterised by impairment of left ventricular function and sudden death. In sinus rhythm, a very low voltage surface P wave associated with a right bundle branch block and left axis deviation was present. The patient’s sister, who showed the same electrocardiographic pattern, had previously died suddenly. The patient’s echo cardiogram showed enlarged right and left atria, mild mitral valve regurgitation and normal-sized left ventricle with ejection fraction just below the normal range (50%). Over the last 6 months, the patient complained of recurrent episodes of persistent atrial tachycardia with an almost undetectable surface P wave morphology (Fig. 1); the only lead with a discernible positive P wave was V1. The tachycardia cycle length was 310 ms with a prevalent 2:1 atrioventricular conduction, although not infrequently a 1:1 conduction was observed. During sinus rhythm and tachycardia, frequent monomorphic ventricular ectopies were recorded (Fig. 1). Since the arrhythmia recurred early after cardioversion, the patient was highly symptomatic and oral amiodarone was considered a second-choice option, an ablation procedure was planned.