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'Obesity paradox' observed in patients after TAVR
The “obesity paradox,” previously reported in patients after PCI, may also occur in those who have undergone transcatheter aortic valve replacement, according to study findings. Specifically, obese patients who underwent transcatheter aortic valve replacement had a greater incidence of minor, but not major, perioperative complications and lower 30-day mortality.
In all, researchers studied 940 patients who underwent TAVR, of whom 25 (2.7%) were underweight, 384 (40.9%) normal weight, 372 (39.6%) overweight and 159 (16.9%) obese.
Obese patients had a greater incidence than normal weight and overweight patients of minor stroke (1.3% vs. 0 [normal] and 0.3% [overweight]; P=.03), minor vascular complications (15.7% vs. 9.1% [normal] and 11.6% [overweight]; P=.028) and acute kidney injury stage I (23.3% vs. 10.7% [normal] and 16.1% [overweight]; P<.001).
There was no association between BMI and 30-day and 1-year mortality when using it as a categorical variable. As a continuous variable, BMI was associated with a lower risk for mortality at 30 days (OR=0.93; 95% CI, 0.86-0.98) but had no effect on survival after discharge (HR=1.01; 95% CI, 0.96-1.07), leading researchers to suggest that the findings underscore the obesity paradox in patients undergoing TAVR. Furthermore, every BMI increase in 1 kg/m2 was associated with a 7% mortality reduction.
The researchers also said obese patients were younger than the nonobese patients and had a greater prevalence of preserved ventricular and renal function.
“The combination of these characteristics might have contributed and, even explain, the lower rate of all-cause mortality at 30 days, providing a possible explanation for the apparent paradox,” they wrote.
Disclosure: Van der Boon reports no relevant financial disclosures.Perspective
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Although these results indicate that there might be some protective issues for obese TAVR patients, as the authors reported, the obese patients in this study in general were actually younger, and had better LV and renal function than nonobese patients. The paper states in the conclusion that the findings at 30 days, with the mortality difference favoring obese patients, may be secondary to the finding that they had better baseline CV function. So I don’t necessarily believe that this study conclusively makes the case that overweight patients are going to do better with TAVR, or even PCI for that matter (based on prior literature examining the obesity paradox in PCI patients). Initially, as it states in the study, obese patients had more complications. This may be explained by the fact that when interventionalists/surgeons access the groin site to insert catheters, obese patients generally have more tissue to traverse, thus making access more difficult and possibly resulting in more bleeding.
Ultimately, I feel that more research should be performed examining this “obesity paradox” in TAVR before stating that a particular subset of patients based on weight do better or worse. The “paradox” we are seeing in these studies may be secondary to the fact that the patients on the other end of the spectrum (ie, the nonobese population) may in fact be a very frail and cachectic cohort. Indeed, most patients who are approved to undergo TAVR in the United States are usually extremely sick to begin with and frailty is not unexpected. Thus obesity may not be a “protective” factor, but rather an indication of the disease process not reaching end-stage where basic metabolic and systemic pathways tend to deteriorate. The authors bring up an interesting point, but as aforementioned, I feel only looking at larger data sets/patient populations from other TAVR studies performed around the world can we get a better idea if weight/BMI is a true factor in predicting outcomes after these procedures.