Assessment of Myocardial Ischemia in Obese Individuals Undergoing Physical Stress Echocardiography (PSE)

The obesity paradox in the stress echo lab: fat is better for hearts with ischemia or coronary microvascular dysfunction

BACKGROUND

Obesity is an independent risk factor for coronary artery disease (CAD), but once CAD has developed it has been associated with improved survival ("obesity paradox").

AIM

To assess how obesity affects prognosis in patients with or without inducible ischemic regional wall motion abnormalities (RWMA) and/or abnormal coronary flow velocity reserve (CFVR) during stress echocardiography (SE).

METHODS

In an observational retrospective two- center study design, we analyzed 3249 consecutive patients (1907 men; age 66 ± 12 years; body mass index, BMI, 26.9 ± 4.1 kg/m²) with known (n = 1306) or suspected (n = 1943) CAD who underwent dipyridamole SE with simultaneous evaluation of RWMA and CFVR. All-cause death was the outcome end-point.

RESULTS

1075 patients were lean (BMI 18.5-24.9 kg/m²), 1523 overweight (BMI 25.0-29.9 kg/m²), and 651 obese (≥30.0 kg/m²). Ischemic test result for RWMA occurred in 28 (3%) lean, 69 (4%) overweight, and 28 (4%) obese patients (p = 0.03). An abnormal CFVR (≤2.0) was found in 281 (26%) lean, 402 (26%) overweight and 170 (26%) obese patients (p = 0.99). During 68 ± 44 months of follow-up, 496 (15%) patients died. At multivariable Cox analysis, BMI ≥ 30 was an independent predictor of reduced mortality in the 878 patients with stress-induced (≥2 segments) RWMA and/or CFVR abnormality (HR 0.58, 95% CI 0.40-0.84; p = 0.003), while showed no effect at univariate analysis in the 2371 patients with no RWMA and normal CFVR (HR 1.04, 95% CI 0.74-1.46; p = 0.84).

CONCLUSIONS

Obesity exerts a "paradoxical" protective effect in patients with stress-induced ischemia and/ or coronary microvascular dysfunction, and shows a neutral effect in patients with normal CFVR and no stress-induced RWMA.

Management of cardiovascular diseases in patients with obesity

The management of cardiovascular diseases (CVD) in patients with obesity presents numerous challenges. Obesity has a negative effect on almost all of the major CVD risk factors, and adversely influences cardiovascular structure and function. Patients who are overweight or obese have a higher incidence of almost all CVDs compared with patients who are of normal weight. However, those who are overweight or obese seem to have a better short-term and medium-term prognosis after major CVD events and interventional procedures or cardiac surgeries than leaner patients, a phenomenon termed the 'obesity paradox'. In considering the mechanisms underlying this paradox, we review evidence of the deleterious consequences of obesity in patients with coronary heart disease, and the limited data on the benefits of weight loss in patients with CVD. Additional studies are needed on the efficacy of purposeful weight loss on cardiovascular outcomes to determine the ideal body composition for patients with CVD.

Stress echocardiography in patients with morbid obesity

The incidence of significant obesity is rising across the globe. These patients often have a clustering of cardiovascular risk factors and are frequently referred for noninvasive cardiac imaging tests. Stress echocardiography (SE) is widely used for assessment of patients with known or suspected coronary artery disease (CAD), but its clinical utility in morbidly obese patients (in whom image quality may suffer due to body habitus) has been largely unknown. The recently published Stress Ultrasonography in Morbid Obesity (SUMO) study has shown that SE, when performed appropriately with ultrasound contrast agents (whether performed with physiological or pharmacological stress), has excellent feasibility and appropriately risk stratifies morbidly obese patients, including identification of patients who require revascularization. This article reviews the evidence supporting the use of echocardiographic techniques in morbidly obese patients for assessment of known or suspected CAD and briefly discusses other noninvasive modalities, including magnetic resonance and nuclear techniques, comparing and contrasting these techniques against SE.