Obesity and Substrate for Atrial Fibrillation | Journal Scan

Jun 30, 2015
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Authors:
Mahajan R, Lau DH, Brooks AG, et al.
Citation:
Electrophysiological, Electroanatomical, and Structural Remodeling of the Atria as Consequences of Sustained Obesity. J Am Coll Cardiol 2015;66:1-11.
Summary By:
Thomas C. Crawford, MD, FACC

Study Questions:

Does obesity affect global endocardial electrophysiological, electranatominal, and structural substrate of the atria?

Methods:

Ten sheep were fed a high-calorie diet until they gained weight and sustained it for 36 weeks. Ten age-matched sheep maintained baseline weight and were used as controls. All sheep underwent electrophysiological and electroanatomical mapping, echocardiography, and dual-energy x-ray absorptiometry scans, as well as histological and molecular evaluation.

Results:

Compared with controls, chronically obese sheep had greater left atrial (LA) volume, LA pressure, pulmonary artery pressure, reduced atrial conduction velocity, increased conduction heterogeneity, increased fractionated electrograms, decreased posterior LA voltage, and increased voltage heterogeneity (all statistically significant). There was no change in effective refractory period (ERP) and ERP heterogeneity. Obese sheep were more susceptible to atrial fibrillation (AF) induction during ERP testing. Reduced posterior LA voltage was due to epicardial fat infiltration. Atrial fibrosis and transforming growth factor (TGF)-β1 protein expression were increased in the obese sheep.

Conclusions:

The authors concluded that obesity results in global biatrial remodeling presenting a unique substrate for AF.

Perspective:

There are a slew of data linking obesity and AF. The effect of obesity on AF is confounded by the coexistence in many patients of hypertension, diabetes, coronary artery disease, and obstructive sleep apnea. The obese sheep model in the present study managed to exclude the confounding factors. The study provides an insight into the development of the AF substrate in obese patients—fat migration from the epicardium to the posterior LA. In addition to the obvious strategy of weight loss, this process could one day become a target of pharmacotherapy.

Keywords: Absorptiometry, Photon, Arrhythmias, Cardiac, Atrial Fibrillation, Diabetes Mellitus, Echocardiography, Electrophysiology, Heart Atria, Hypertension, Metabolic Syndrome, Pericardium, Pulmonary Artery, Transforming Growth Factor beta1, Obesity


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