Impact of Extreme Obesity on PCI Outcomes (JACC in a Flash)
As the obesity epidemic continues in the United States, more and more obese—particularly morbidly obese—patients are at risk for cardiac disease, and more and more likely to need invasive cardiac procedures. Little is known, however, about the prevalence and outcomes of PCI in morbidly obese patients (BMI ≥40 kg/m2). Two new studies published in JACC sought to examine this relationship, the impact of extreme obesity on clinical outcomes, and what steps need to be taken to prevent the rise of morbid obesity.
The Burgeoning Epidemic of Morbid Obesity in PCI Patients
In their study, Michael E. Buschur, MD, from the University of Michigan in Ann Arbor, and colleagues collected data from a total of 227,044 PCI patients enrolled in the Blue Cross Blue Shield of Michigan Cardiovascular Consortium (BMC2) Registry from 1998 to 2009.
The investigators divided the study population into four categories: 19.1% were "lean" (BMI <25), 36.3% were "overweight" (BMI 25.0-29.9), 37.2% were "sub-morbidly obese" (BMI 30-39.9), and 7.4% were "morbidly obese" (BMI ≥40). Members of the morbidly obese group were significantly younger than the other groups (mean age = 59.2 years vs. 64.9 years), were less likely to be smokers, and had a significantly higher incidence of hypertension and diabetes.
From 1998 to 2009, the authors noted significant changes in the obesity profile. For instance, the proportion of lean patients decreased from 22.64% to 18.48%, while the proportion of morbidly obese patients increased from 4.38% to 8.36%. During this period, there was a 91% increase in the number of morbidly obese patients presenting for PCI; as expected, this group also had an increased risk of contrast-induced nephropathy, vascular complications, and death.
Insights from the CathPCI Registry
The findings from the BMC2 Registry were confirmed in an analysis of CathPCI Registry data from 2009 to 2011, conducted by Saeed Payvar, MD, MS, from the East Carolina University Brody School of Medicine in Greenville, North Carolina, and colleagues. Dr. Payvar and his team compared in-hospital outcomes of PCI for 217,616 normal-weight patients (BMI = 20.0-24.9) and 83,861 extremely obese (BMI ≥40) patients.
Again, extremely obese patients were younger than normal-weight patients and had a markedly higher prevalence of cardiac risk factors, like diabetes and hypertension. Multivariate adjustment showed that extreme obesity was independently associated with higher mortality (OR =1.14) and lower bleeding (OR = 0.80). This increased mortality risk was restricted to the setting of STEMI, however. The lower bleeding risk, Payvar et al. noted, may be due to complications of weight-based dosing of anticoagulants.
Evidence Against the Obesity Paradox?
Regardless of differing risk factors and access route, Payvar et al. found that extreme obesity in patients presenting with STEMI carried greater risk of poor outcomes, seemingly disproving the "obesity paradox," which suggests that obesity exerts a cardioprotective effect on PCI patients.
Buschur et al. found similar results, stating: "[Morbidly obese] patients have a markedly increased risk of complications, suggesting that the obesity paradox does not appear to be protective in this population." Furthermore, compared to the normal-weight patients in their study, the morbidly obese patients had better baseline LVEF and lower incidence of AMI, cardiogenic shock, and less need for emergent PCI—all factors that are traditionally associated with a lower mortality risk in PCI patients.
"The reasons for this increased risk despite the presence of lower risk features suggest that factors other than traditional risk factors for post-PCI mortality may play a role in this population," Dr. Buschur and colleagues wrote. "The dramatic increase in the proportion of young patients with morbid obesity invokes the need for more upstream interventions for primary prevention and better treatment of obesity."
Buschur ME, Smith D, Share D, et al. J Am Coll Cardiol. 2013 June 18. [Epub ahead of print]
Payvar S, Kim S, Rao SV, et al. J Am Coll Cardiol. 2013 June 18. [Epub ahead of print]
Keywords: Morbidity, Overweight, Blue Cross Blue Shield Insurance Plans, Risk Factors, Primary Prevention, Prevalence, Shock, Cardiogenic, Registries, Incidence, Body Mass Index, Obesity, Morbid, Hypertension, United States, Diabetes Mellitus
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