Study Finds No ‘Obesity Paradox’ in DES-Treated Patients

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Contrary to several reports demonstrating an ‘obesity paradox’ in patients receiving percutaneous coronary intervention (PCI), a new study in the February 2012 issue of JACC: Cardiovascular Interventions shows no weight-related differences in hard outcomes among patients after drug-eluting stent (DES) implantation.

Researchers led by Christoph A. Nienaber, MD, PhD, of the Heart Center Rostock (Rostock, Germany), analyzed data from 1,436 (24.7%) normal-weight, 2,839 (48.9%) overweight, and 1,531 (26.4%) obese patients who received DES between October 2005 and 2006 at 98 sites in the prospective German Drug-Eluting Stent registry. Patients received either paclitaxel-eluting (PES) or sirolimus-eluting stents (SES). Mean age was 65 years, with normal-weight patients (66.1 years) being older than overweight (65.5 years) or obese (63.7 years; P < 0.0001) patients.

Outcomes Similar at 1 Year

In-hospital, there were few differences in outcomes except for a slight increase in mortality in normal-weight patients (0.8%) compared with overweight (0.5%) and obese patients (0.3%; P for trend = 0.05). There was also a trend for increased MACCE (death, MI, stroke) in the normal-weight patients (2.4%) vs. overweight (2.2%) vs. obese patients (1.6%; P for trend = 0.10).

At 1-year follow-up (available in 97.1% of patients), outcomes were equivalent across all groups for endpoints including mortality, MI, TVR, stent thrombosis, and major bleeding. The only exceptions were minor bleeding and MACCE, which showed a higher rate and an increased trend, respectively, in normal-weight patients (table 1).

Table 1. One-Year Outcomes

 

Normal Weight

Overweight

Obese

P Value
(Trend)

Mortality

3.3%

2.4%

2.4%

0.17

MI

2.8%

2.3%

2.3%

0.45

MACCE

7.1%

5.6%

5.5%

0.09

TVR

10.9%

11.7%

11.6%

0.56

Stent Thrombosis
   
Definite
  
 Probable

1.2%
1.1%

1.2%
0.8%

1.1%
0.6%

0.93
0.26

Bleeding
Major
Minor

2.5%
57.2%

2.1%
46.3%

2.8%
45.7%

0.53
< 0.0011


Antiplatelet therapy was similar across the groups. Subgroup analysis showed no difference in outcomes among the different weight groups according to use of PES or SES. In addition, on multivariable analysis, body mass index (BMI) was not a predictor of either MACCE (HR 0.92 for increase of 5 kg/m2; 95% CI 0.81-1.04) or TVR (HR 1.00 for increase of 5 kg/m2; 95% CI 0.90-1.12) at 1 year.

“Data from [the study] revealed no evidence of the ‘obesity paradox’ in patients subjected to DES treatment in routine clinical practice,” the researchers conclude, adding that the concept of the obesity paradox “may actually be a misnomer, or may in fact not exist at all.”

For instance, Dr. Nienaber and colleagues observe, it may be explained simply by the fact that overweight and obese patients are usually younger and therefore have better outcomes after acute MI regardless of reperfusion method. Also, the presence of comorbidities in overweight and obese patients usually leads to more aggressive treatment for cardiovascular risk factors, thereby improving outcomes despite obesity.

In Defense of the Paradox

However, outside experts were not convinced the study proves or refutes anything. Robert M. Minutello, MD, of Weill Cornell Medical College (New York, NY), pointed to the higher in-hospital mortality and MACCE in the normal-weight patients. “The majority of the PCI and critical care literature suggests that moderate obesity portends a protective effect in the acute setting, and that’s what this also supports,” he told TCTMD in a telephone interview.

Luis Gruberg, MD, of Washington Hospital Center (Washington, DC), agreed. “You cannot ignore the strong trends that you see in those outcomes,” he said in a telephone interview with TCTMD. Dr. Gruberg also pointed to the Kaplan-Meier 1-year MACCE-free survival estimate, which showed a lower trend among normal-weight patients (P = 0.07). “That’s a very strong trend,” he said. “That’s telling us something, and maybe if they had more patients, it would become significant.”

As far as the longer-term results, “the obese patients are expected to have a higher incidence of cardiac events,” Dr. Minutello said. “It’s not surprising that there’s a late catch-up at 1 year.”

Not All Obesity Created Equal

His main criticism of the study methodology was that the researchers did not divide the obese patients into further categories. “There’s a difference among the different classes of obesity,” Dr. Minutello said. “My conclusion was not that obesity in general is protective, it’s more that moderate obesity is protective, but patients with severe, class 3 obesity actually do worse. The authors are putting all that together, I would have liked to see a subdivision of obesity into the 3 typical categories.”

In previous research published in the American Journal of Cardiology (Minutello RM, et al. 2004;93:1229-1232), Dr. Minutello and colleagues found that patients who were at either end of the spectrum—extremely obese with a BMI > 40 or underweight with a BMI < 18.5—had significantly higher mortality and MACE after PCI compared with patients more toward the middle BMI ranges.

In particular, the extremely low-weight individuals may help explain some of the obesity paradox. “What’s the explanation for overweight and moderately obese patients doing better?” Dr. Minutello said. “It’s in comparison to what we consider normal, but a certain fraction of ‘normal’ patients at the lower end of the BMI scale may in fact be underweight, and they may have concomitant illnesses. It’s impossible to tease out and nobody knows the answer, but that’s what I think a lot of it is.” In the current study, 16 severely ill patients with a BMI less than 18.5 were excluded.

Regardless, Dr. Gruberg maintained that clinicians have to be careful when talking with patients regarding studies supporting any protective effects of obesity. “I don’t think we should be giving the message that being fat is good and protects you against dying,” he said. “I think it’s still a paradox.”

Study Details

Normal weight was defined as a BMI of 18.5 to 24.9 kg/m2; overweight as a BMI of 25 to 30 kg/m2; obese as a BMI > 30 kg/m2. Overweight and obese patients showed higher rates of diabetes, hypercholesterolemia, and hypertension compared with normal-weight patients, but lower rates of current smoking.

The number of DES, both per patient and per lesion, was equally distributed across the 3 groups. However, stent diameter was larger in the obese patients compared with overweight and normal-weight patients.

 


Source:
Akin I, Tölg R, Hochadel M, et al. No evidence of “obesity paradox” after treatment with drug-eluting stents in a routine clinical practice. Results from the prospective multicenter German DES.DE (German drug-eluting stent) registry. J Am Coll Cardiol Intv. 2012;5:162-169.

 

 

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Disclosures
  • Drs. Nienaber, Minutello, and Gruberg report no relevant conflicts of interest.

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