Atrial Rhythms in Patients with Left Atrial Isomerism

ABSTRACT

PURPOSE: Histologic studies have revealed ectopic location and hypoplasia of sinus nodal tissue in left atrial isomerism. The purpose of this study is to characterize the atrial rhythms corresponding to these histologic abnormalities in left atrial isomerism. Electrocardiograms in left atrial isomerism are characterized by multiple atrial rhythms with abnormal P-wave axes, but the complex nature of atrial rhythms in left atrial isomerism remains to be clarified. METHODS: Surface electrocardiograms and Holter recordings of 16 patients with left atrial isomerism were retrospectively reviewed. For comparison, atrial rhythms in 8 patients with right atrial isomerism were studied with the same study protocol. RESULTS: In left atrial isomerism, atrial rhythm with abnormal superior P-wave axis was the most frequent in 69% of patients and multiple atrial rhythms were observed in 37% in surface electrocardiograms. In Holter recordings, transient or persistent slow atrial rhythms with or without visible P waves associated with junctional escape were documented in 9 out of 16(56%) patients. In comparison, multiple atrial rhythms were as frequent as in left atrial isomerism, but slow atrial rhythm with junctional escape was not present in 8 patients with right atrial isomerism. CONCLUSION: It is concluded that transient or persistent slow atrial rhythms associated with junctional escape, suggestive of atrial nodal dysfunction, are characteristic and helpful in the diagnosis of left atrial isomerism.