Lipomatous Hypertrophy of the Interatrial Septum Manifesting as Third Degree Atrioventricular Block

Abstract

A 55-year-old patient was found to have complete heart block during preoperative assessment. Cardiac magnetic resonance imaging revealed an interatrial mass suggestive of primary cardiac tumor. Extensive evaluation including intracardiac biopsy and finally open resection revealed lipomatous hypertrophy masquerading as tumor. ( Level of Difficulty: Intermediate. )

Lipomatous Hypertrophy of Interatrial Septum Presenting with Two Distinct Atrial Arrhythmias

“…The disorganized fibers ultimately result in impairment of electrical conduction and lead to the arrythmias described [2,7]. This is further evidenced by cases where the infiltration extends into the conduction fibers of the Atrioventricular (AV) node resulting in complete AV node block [8].…”

Increased 18F-PSMA and 18F-FDG Uptake in Lipomatous Hypertrophy of the Interatrial Septum

“…4,5 Although LHIS is a benign disorder and remains asymptomatic in the majority of cases, it rarely can cause atrial arrhythmias, obstructive flow symptoms, and sudden death. [6][7][8][9][10][11][12][13] Increased 18 F-FDG uptake in LHIS can occasionally be found on 18 F-FDG PET/CT, 14,15 initially thought to be caused by metabolic activation of brown adipose tissue. 16 There is no evidence of increased 18 F-FDG uptake in other brown adipose tissue in our patient, and this theory has also been questioned by some authors, suggesting inflammation or other unknown mechanism of increased 18 F-FDG uptake.…”

“…It has a prevalence of 1% in autopsy studies 2,3 and between 2.2% and 7.6% in imaging studies, depending on the modality (CT vs transesophageal echocardiography) 4,5 . Although LHIS is a benign disorder and remains asymptomatic in the majority of cases, it rarely can cause atrial arrhythmias, obstructive flow symptoms, and sudden death 6–13 . Increased 18 F-FDG uptake in LHIS can occasionally be found on 18 F-FDG PET/CT, 14,15 initially thought to be caused by metabolic activation of brown adipose tissue 16 .…”

Gaining Insights Into Lipomatous Hypertrophy of the Interatrial Septum

“…In this issue of JACC: Case Reports, Yavar et al. ( 6 ) illustrate the challenges that this diagnosis presents. Their patient, a 55-year-old woman, presented with complete heart block during a routine evaluation before surgery.…”

“…The case described by Yavar et al. ( 6 ) is challenging, for several reasons. First, there is a lack of evidence-based recommendations for diagnosis of this condition.…”