Predictive value of Body Mass Index (BMI) and Waist Circumference (WC) for Coronary Artery Disease (CAD) and Clinical Outcomes using Gated Myocardial Perfusion Imaging.

Abstract

Objective: Obesity is generally considered as a risk factor for coronary artery disease (CAD) and cardiac deaths but some reports suggest better survival in obese with CAD. The objective of this study was to find out predictive value of body mass index (BMI) and waist circumference (WC) for CAD and its outcome using gated myocardial perfusion imaging (GMPI).

Material and Methods: This was a prospective study conducted at Nuclear Cardiology Department of Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan from August 2011 till May 2013. 400 patients who qualified study criteria were included and were divided in (a) to Obese (BMI ≥ 30 Kg/m²) and Non-obese (BMI < 30 30 Kg/m²) and (b) Low-WC group (male <90cm and female <80 cm) and High-WC group (male≥90 cm and female ≥80cm). Rest and stress GMPI using Tc-99m MIBI was performed in all patients and abnormal GMPI was followed by coronary angiogram. These patients were followed for 12-18 months regarding fatal and non-fatal events.

Results:  Non-Obese group included 281 patients (Male: Female = 131:150) with a mean age of 58 ±12 years and mean WC 100 ±15 cm. Obese group included 119 patients (Male: Female = 36:83) with a mean age of 55 ±11 years and mean WC 101±13 cm. Normal GMPI was found in 172 non-obese and 85 obese patients (p<0.05). GMPI was abnormal in 109 non-obese and 34 obese patients (p<0.05). WC was not found independent predictor of abnormal GMPI but high WC was found to a significant predictor of CAD in non-obese females (Odd ratio 8.04; 1.041 – 62.127).  At 18 months event-free survival in normal GMPI group for non-fatal MI was 99.4% in non-obese group and 94.1% for obese (significant P value). For fatal MI, event-free survival was 99.4% in non-obese and 100% for obese (non-significant P value). In patients with abnormal GMPI event-free survival for non-fatal events was 95.4% in non-obese group and 82.3% in obese group (significant P value). While event-free survival for fatal MI was 96.3% in non-obese group and 98.1% for obese (significant P value).

Conclusion: We conclude that CAD was found less prevalent in obese group and High-WC predicted CAD in non-obese females only and was not found an independent predictor. A normal GMPI predicted very high event free survival for fatal events in obese and non-obese but significantly lower for non-fatal events in obese group. Obese group with abnormal GMPI had lower risk for cardiac deaths but higher risk for non-fatal events than non-obese patients with abnormal scans.

Key words: Obesity; Waist circumference, GMPI; event free survival; fatal events