JACC: Obese STEMI patients continue to present 'paradox'

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Extremely obese patients present with STEMI at younger ages, yet have less extensive coronary artery disease and better left ventricular systolic function, adhering to the “obesity paradox,” a study published Dec. 13/20 in the Journal of the American College of Cardiology found. Additionally, obese patients have similar processes and quality of care when compared with normal-weight patients, but see higher risk-adjusted in-hospital mortality rates.

“Despite these adverse effects that overweight and obesity have on CHD [congestive heart disease] risk factors and CHD, numerous studies have addressed the 'obesity paradox,' which suggests that once CV diseases are established, including CHD, the overweight and obese seem to have a better prognosis than do their leaner counterparts,” Carl J. Lavie, MD, of the Ochsner Heart and Vascular Institute in New Orleans, and colleagues wrote in an accompanying editorial.

The prevalence of obesity, which is defined as a body mass index (BMI) greater than or equal to 30 kg/m2, has skyrocketed in the past three decades and now affects one in three U.S. adults.

“The relationships between obesity and non–ST-segment elevation myocardial infarction (NSTEMI) presentation, processes of care and outcomes have been described previously. However, little is known about the relationship between obesity, particularly extreme obesity, and care and outcomes in ST-segment elevation MI (STEMI)," Sandeep R. Das, MD, MPH, University of Texas Southwestern Medical Center in Dallas, and colleagues wrote.

To better understand the impact of “extreme” obesity (a BMI 40 kg/m2 or higher) on outcomes of STEMI patients, Das and colleagues analyzed data from 50,149 STEMI patients from the National Cardiovascular Data Registry (NCDR) ACTION Registry-Get With the Guidelines between Jan.1, 2007, and June 30, 2009, and recorded the relationship between BMI and baseline patient characteristics, treatment patterns and risk-adjusted in-hospital outcomes.

During the study, the researchers classified patients with STEMI by BMI categories: 1.6 percent was underweight, 23.5 percent were of normal weight, 38.7 percent were overweight, 22.4 percent were Class I obese, 8.7 percent were Class II obese and 5.1 percent were Class III obese.

Those STEMI patients classified with Class III obesity were more than a decade younger than their normal-weight counterparts, and these patients were more likely to be women and African-American. Class III obese patients had a higher prevalence of obesity (three-fold) compared with those who were in normal weight class.

Three-fourths of STEMI patients were overweight or obese in the current study and Class III obesity affected one in 20 STEMI patients.

There were no differences in the use of evidence-based medical therapies across all BMI groups during the study, and prescription of evidence-based therapies at hospital discharge (aspirin, clopidogrel, beta-blockers and ACE inhibitors/ARB use) also did not differ across the various groups. Class III obese classified patients were less likely to be prescribed statins at discharge.

“Rates of adverse outcomes in general were highest among normal-weight patients, lower in overweight and mild to moderately obese patients, and then increased again in patients with Class III obesity,” the authors found in an unadjusted analysis.

Lastly, Das et al noted that Class III obesity was linked to an increase in the risk of in-hospital mortality but not major bleeding.

“These data are encouraging and suggest the absence of an obesity-related systematic bias in the delivery of STEMI care, even to Class III obese patients,” the authors noted.

Das and colleagues called the increase in mortality in patients classified as Class III obese concerning; particularly due to the rapid rise in Class III obesity prevalence seen in the U.S. Obesity has increased nearly 150 percent between 1960 and 2004. Meanwhile the prevalence of Class III obesity increased from 0.9 percent to 5.1 percent, a relative increase of 460 percent.

The fact that anticoagulants and antiplatelet drugs go unprescribed in more obese patients could have led to the increased mortality seen during the study, the authors said.

“The enigma of patients who are at lower a priori risk and receive similar care but nevertheless have worse outcomes mandates further attention and elucidation as the population prevalence of Class III obesity continues to grow at a pace that far exceeds the overall rise in obesity,” Das et al summed.

In the accompanying editorial, Lavie and colleagues wrote: “Quite possibly, overweight and obese patients who develop CV diseases may have avoided these diseases in the first place had significant weight gain been prevented, whereas the lean patients who develop CV diseases do so for other reasons, such as genetic predisposition, which could be associated with a worse prognosis."