Mechanisms of Left Atrial Enlargement in Obese Individuals

PURPOSE: Obesity is linked to diastolic dysfunction and left atrial enlargement (LAE); however, the mechanisms responsible for LAE in obesity are unknown. Previous studies have demonstrated that LAE is directly related to diastolic dysfunction [1], though the influence of obesity on this association is unclear. In this thesis, we examine if obese subjects have left atrial enlargement when compared to age and sex matched non-obese controls. We then attempted to identify relationships between LAE and various echocardiographic measures of diastolic dysfunction. We hypothesized that LAE in obese subjects is not related to diastolic function but rather is associated with overall increased heart size. METHODS: Thirty-seven middle-aged, obese subjects (10M: 27F, 49±7years) with an average body mass index (BMI) of 38 ±5 kg/m2 were compared to age and sex matched non-obese healthy controls. Diastolic function (E/A ratio, e', IVRT; isovolumic relaxation time, Vp; propagation velocity) was assessed using Doppler echocardiography. Left atrium (LA) size was measured using 3D echocardiogram, and normalized to height, body surface area (BSA), and left ventricular (LV) volume to account for the effects of body size. RESULTS: Obese individuals had a significantly enlarged atrial volume when compared to healthy individuals when indexed to height (36 ± 8 vs. 23 ± 5 mL/m; p<0.01). Obese subjects had a significantly shorter IVRT when compared to non-obese subjects (68 ± 11 vs 100 ± 16 msec; p<0.0001) indicating a higher LA pressure. Obese subjects also had a significantly faster Vp when compared to non-obese subjects (74 ±18 vs 53 ±12 cm/sec; p<0.0001). When LA volume of obese subjects was indexed to LV volume, there was no difference between groups (0.39 ± 0.1 vs 0.42 ± 0.1 p=0.2). CONCLUSIONS: While obese subjects have larger LA volumes and markers of elevated LA filling pressures (IVRT and Vp) compared to age matched controls, their LA size was similar when indexed to their LV volume. We conclude that obesity causes an increased LA volume that is proportional to LV volume. While LA enlargement in obese individuals may increase the risk of atrial fibrillation, is possibly a physiologic rather than pathological phenomenon.

Name thesis:degree_name

M.D. with Distinction

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Research

Grantor

UT Southwestern Medical Center

Year dc:date.issued

2018

Author dc:creator

• Aiad, Norman Nadir

Advisor dc:contributor.advisor

• Levine, Benjamin

Committee members dc:contributor.committeemember

• Lawley, Justin
• Joglar, Jose

• Heart Atria
• Obesity

Language dc:language.iso

en

Identifier

1156324495

OAI record oai:identifier

https://utswmed-ir.tdl.org/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Autswmed-ir.tdl.org%3A2152.5%2F8337