Lipomatous Hypertrophy of the Interatrial Septum: An Overview

Archives of Pathology & Laboratory Medicine, Mar 2006 by O'Connor, Siobhan, Recavarren, Rosemary, Nichols, Lawrence C, Parwani, Anil V

CLINICAL FEATURES

Although lipomatous hypertrophy of the interatrial septum has often been identified incidentally, atrial arrhythmias, including atrial fibrillation, atrial premature complexes, supraventricular tachycardia, ectopic atrial rhythm, and junctional rhythm, have been associated with lipomatous hypertrophy.24" Although other sources of cardiac arrhythmia may exist in older patients (eg, atrial enlargement due to decreased ventricular compliance8 and atherosclerotic coronary disease), Shirani and Roberts" provided statistical evidence of a causal association between lipomatous hypertrophy and arrhythmia. This association is not unreasonable because the accumulation of fat is often located in the region where 2 of the pathways between the sinoatrial node and the atrkwentricular node course through the atrial septum anterior to the fossa ovalis." An abnormal P-wave configuration in leads II, III, and aVF, originally termed dome and dip, has been described in some patients with lipomatous hypertrophy of the interatrial septum and may be due to conduction disturbances.3,9,27 Extension into the superior vena cava, with right atrial inflow obstruction, has also been described.28,29

Although intervention is not usually required, surgical resection has been performed in symptomatic patients with superior vena caval obstruction or with intractable arrhythmias.1" One patient with subtotal obstruction of the superior vena cava had recurrent pericardial effusions and symptoms of constrictive pericarditis.11 An association between lipomatous hypertrophy and cerebrotendinous xanthomatosis was proposed in one study,12 and lipomatous hypertrophy of the interatrial septum has been reported as an unusual complication of total parenteral nutrition.11 Although it is impossible to prove that lipomatous hypertrophy causes sudden death, it has been accepted as a presumptive cause of fatal arrhythmias. In one series, lipomatous hypertrophy of the interatrial septum was the only finding to explain sudden death in 3 patients.1" In the same series, the cause of death appeared to be directly related to the lipomatous hypertrophy in 6 additional patients who experienced prolonged episodes of cardiac arrhythmia or persistent congestive heart failure. Because lipomatous hypertrophy is increasingly diagnosed before death and may be biopsied or excised, it is important for the surgical pathologist to be familiar with this entity. It is worthwhile to consider lipomatous hypertrophy in older patients with otherwise unexplained rhythm disturbances or congestive heart failure and in patients with sudden cardiac death from an unknown cause.

CONCLUSIONS

Lipomatous hypertrophy of the interatrial septum is an unencapsulated accumulation of adipose cells and dispersed cardiac myocytes, which may be a neoplasm or a developmental anomaly. With improvements in imaging, lipomatous hypertrophy of the interatrial septum is recognized more frequently in living patients. This entity may come to the attention of the pathologist during surgery or as an excised specimen. It should be kept in mind as a possible cause of death in the autopsy of any patient with a sudden death without any other explanation revealed by the postmortem investigation.