ABSTRACT
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]. 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 [BMI30 Kg/m[2]] and Non-obese [BMI<30 Kg/ m[2]] and [b] Low-WC group [male<90 cm and female < 80 cm] and High-WC group [male 90 cm and female 80 cm]. 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. 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]. 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