Effects of Weight Loss on Cardio-respiratory Function

Obesity is a medical problem of epidemic proportions and is associated with high mortality.
Obesity has significant effects on the cardiovascular system, producing structural
cardiovascular changes including myocardial hypertrophy, fatty infiltration, and fibrosis;
diastolic and systolic dysfunction; changes in pulmonary artery compliance; and increased
aortic stiffness - all of which can lead to heart failure. Indeed, evidence suggests that
obesity increases the risk for heart disease independent of other known risk factors such as
coronary artery disease, hypertension, diabetes mellitus, and obstructive sleep apnea.
Obesity also causes significant changes in pulmonary function, including a decrease in
expiratory reserve volume and functional residual capacity and closure of peripheral
airways. The exact mechanisms for the development of cardiopulmonary disease are not well
understood - the pathophysiology is complex and likely multifactorial, related to altered
hemodynamic load, altered metabolic activity, underlying inflammation, and increased cardiac
output.

Newer diagnostic modalities available at our institution such as cardiac MRI and pulmonary
function tests with impulse oscillometry allow us to better evaluate cardiopulmonary
dysfunction in patients with severe obesity. Cardiac MRI is especially promising as a
non-invasive imaging modality in obese individuals, providing more reproducible measurements
of cardiac and vascular anatomy and function relative to echocardiography. Similarly,
pulmonary function testing with impulse oscillometry is more sensitive for detection of
abnormalities in the distal airways especially when spirometry is normal, as frequently
occurs in the severely obese symptomatic patients. The main objective of the proposed study
is to evaluate the effect of obesity on quality of life and health care utilization and its
relationship to cardiopulmonary disease in an ethnically diverse, underserved obese
population by using state-of-the-art diagnostic modalities before and after significant
(20%) weight loss.

The investigators propose to perform stress cardiac MRI and pulmonary function testing with
oscillometry before and after significant surgical weight loss in 150 severely obese
patients with cardiopulmonary symptoms. Patients evaluated in the comprehensive Obesity
Center at Bellevue Hospital who meet NIH Consensus Guidelines for Bariatric Surgery, who
have cardiopulmonary symptoms, and who meet clinical criteria for cardiac stress testing and
pulmonary function testing will be approached by the study personnel and offered enrollment.
Informed consent will be obtained. Enrolled patients will undergo clinical evaluation with a
detailed medical history including the Borg dyspnea scale, physical examination, laboratory
testing including cardiopulmonary biomarkers (brain natriuretic peptide, C-reactive protein,
atrial natriuretic peptide), and non-invasive cardiovascular stress MRI and pulmonary
physiologic evaluation including spirometry, plethysmography and impulse oscillometry (IOS).
Patients with active smoking history and/or asthma will be identified clinically.

Cardiovascular MRI will be performed using a 1.5T (Avanto or Espree, Siemens Healthcare)
system. Standard cardiovascular techniques will be used for the assessment of myocardial and
vascular structure and function, including T1-weighted, T2-weighted, late gadolinium
enhancement, cine, tagged and phase contrast imaging in selected planes. Adenosine stress
MRI will be performed for evaluation of underlying coronary artery or microvascular disease.