Cardiac Output and Index in Obese and Non-obese Patients using Gated Single Photon Emission Computed Tomography Sestamibi Perfusion Imaging

JP Coffey, JC Hill

Hong Kong J Radiol 2005;8:226-32

Objective: To assess prospectively the overall prevalence of abnormal cardiac index values in a symptomatic group of patients from gated single photon emission computed tomography perfusion studies and to compare cardiac index of patients with body mass index <30 and obese patients (body mass index >30).

Patients and Methods: 112 patients (62 females) aged 37 to 81 years (mean, 57 years) referred for evaluation of chest pain, dyspnoea or inconclusive exercise electrocardiogram, underwent gated single photon emission computed tomography perfusion imaging with technetium 99m sestamibi intravenously following Bruce exercise protocol (102 patients) or dobutamine stressing (10 patients). Cardiac output was calculated as the product of resting heart rate and stroke volume and cardiac index determined using the body mass index. Left ventricular ejection fraction, stroke volume, and end-systolic volume were determined for each patient.

Results: Seventy three patients (65%) had an abnormal cardiac index (<2.5 L/min/m2). The mean cardiac index overall was 2.19 L/min/m2. Twelve patients had left ventricular ejection fraction less than 50%, and the mean left ventricular ejection fraction overall was 61%. Thirty two patients with body mass index >30 had mean cardiac index of 2.28 L/min/m2, which was not significantly different from an age-matched group of 32 non-obese controls (body mass index <30; mean cardiac index, 2.24 L/min/m2). Left ventricular ejection fraction was elevated in the obese group compared with the non-obese group (mean, 65.2% versus 58%; p < 0.03).

Conclusions: A high prevalence of abnormally low cardiac index was observed in symptomatic patients. Obese patients had similar cardiac index to non-obese control patients, but had an elevated left ventricular ejection fraction suggesting hypersystolic function.