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CLINICAL RESEARCH

Association of Subclinical Right Ventricular Dysfunction With Obesity

University of Queensland, Brisbane, Australia

Manuscript received May 11, 2005; revised manuscript received August 11, 2005, accepted August 15, 2005.

^_* Reprint requests and correspondence: Prof. Thomas H. Marwick, University of Queensland Department of Medicine, Princess Alexandra Hospital, Ipswich Road, Brisbane Qld 4102, Australia. (Email: tmarwick{at}soms.uq.edu.au).

OBJECTIVES: The purpose of this research was to identify the determinants of right ventricular (RV) dysfunction in overweight and obese subjects.

BACKGROUND: Right ventricular dysfunction in obese subjects is usually ascribed to comorbid diseases, especially obstructive sleep apnea. We used tissue Doppler imaging to identify the determinants of RV dysfunction in overweight and obese subjects.

METHODS: Standard and tissue Doppler echocardiography was performed in 112 overweight (body mass index [BMI] 25 to 29.9 kg/m²) or obese (BMI >30 kg/m²) subjects and 36 referents (BMI <25 kg/m²), including 22 with obstructive sleep apnea but no obesity. Tissue Doppler was used to measure RV systolic (s_m) and diastolic (e_m) velocities and strain indexes.

RESULTS: Obese subjects with BMI >35 kg/m² had reduced RV function compared with referent subjects, evidenced by reduced s_m (6.5 ± 2.4 cm/s vs. 10.2 ± 1.5 cm/s, p < 0.001), peak strain (–21 ± 4% vs. –28 ± 4%, p < 0.001), peak strain rate (–1.4 ± 0.4 s^–1 vs. –2.0 ± 0.5 s^–1, p < 0.001), and e_m (–6.8 ± 2.4 cm/s vs. –10.3 ± 2.5 cm/s, p < 0.001), irrespective of the presence of sleep apnea. Similar but lesser degrees of reduced systolic function (p < 0.05) were present in overweight (BMI 25 to 29.9 kg/m²) and mildly obese (BMI 30 to 35 kg/m²) groups. Differences in RV e_m, s_m, and strain indexes were demonstrated between the severely versus overweight and mildly obese groups (p < 0.05). Body mass index remained independently related to RV changes after adjusting for age, log insulin, and mean arterial pressures. In obese patients, these changes were associated with reduced exercise capacity but not the duration of obesity and presence of sleep apnea or its severity.

CONCLUSIONS: Increasing BMI is associated with increasing severity of RV dysfunction in overweight and obese subjects without overt heart disease, independent of sleep apnea.

Abbreviations and Acronyms   AHI = apnea-hypopnea index   BMI = body mass index   LV = left ventricle/ventricular   OSA = obstructive sleep apnea   RV = right ventricle/ventricular   RV em = right ventricular early diastolic velocity   RV sm = right ventricular systolic velocity   SatO2 = oxygen saturation   SR = strain rate   TDI = tissue Doppler imaging   TR = tricuspid regurgitation   VO2max = peak ventilatory capacity

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