‘Obesity Paradox’ Alive, Well, and Mysterious After TAVR
PARIS, France—The so-called “obesity paradox” previously observed in patients undergoing TAVR, which seemingly protects patients with high BMIs, has been documented yet again in a single-center German study. However, this effect was not observed in patients undergoing surgical aortic valve replacement.
Prior subanalyses of the FRANCE 2 registry and the PARTNER trials have linked obesity—and even just higher-than-normal BMIs—with lower rates of 1-year mortality and major vascular complications. Researchers have yet to pinpoint the exact mechanism behind this phenomenon, and operators still await more data as they risk-stratify patients slated for either TAVR or surgery.
Presenting at EuroPCR 2016, Marco Spaziano, MD (Institut Cardiovasculaire Paris Sud, France), explained how his group stratified 3,340 patients who underwent TAVR (n = 1,301) or surgery (n = 2,039) at a single German hospital between 2007 and 2015 into quartiles by BMI:
- Q1: BMI < 24.3 kg/m2
- Q2: BMI 24.3-27.0 kg/m2
- Q3: BMI 27.0-30.1 kg/m2
- Q4: BMI > 30.1 kg/m2
Among TAVR patients, those with the lowest BMI had higher rates of mortality, major bleeding, and major vascular complications at 30 days and 1 year compared with those in the other quartiles (P < 0.05 for trend for all). In contrast, there were no differences in any outcomes among quartiles within the surgical arm.
On top of being a retrospective single-center study, Spaziano said the study was limited as it was unadjusted and included data from both the early and late TAVR experience.
‘Hockey Stick Relationship’
Commenting from the audience, Danny Dvir, MD (St. Paul’s Hospital, Vancouver, Canada), said “it’s really important to have a couple of studies looking at the same thing and we got similar results,” referring to the aforementioned PARTNER data on obese patients. However, he was curious as to why this team decided to classify patients by quartiles and not by more conventional definitions of under, normal, and overweight as well as obesity.
Spaziano explained that there weren’t enough patients in the conventional underweight group to have statistically relevant analyses. But using BMI as a “potential quick way to evaluate if a patient is going to do well after [TAVR] or not” is a good idea and something to potentially investigate down the road,” he said.
Because this study is population-based, “we’ve noticed . . . a shift over time where the higher-risk patients are now going to [TAVR],” Spaziano continued. “So maybe this obesity paradox problem is only pertinent for the higher-risk patients. We didn’t find the association in the surgical patients because maybe now weight or BMI doesn’t matter as much.”
In agreement, Dvir said the paradox likely has more of an effect on more challenging patients.
There is a “slight nuance” to the whole thing though, Spaziano commented. “The way I first saw this was that obese patients had lower mortality and the other patients were about equal. What we found here is not the same thing at all. It’s more like a hockey stick relationship where low BMI patients do bad and all others do about the same.”
Thin Doesn’t Mean Fit
Given that contemporary wisdom advocates for patients to lose weight, eat healthy, and exercise, panel moderator Ganesh Manoharan, MBBCh, MD (Royal Victoria Hospital, Belfast, Northern Ireland), expressed confusion at how it would make sense that overweight patients somehow do better than thinner people after TAVR. “When I reach 80 and put a stethoscope to my heart and hear a whoosh, should I then rapidly start eating a hell of a lot of food?” he joked.
Spaziano pointed to the fact that in this study, predictors of mortality at 30 days included chronic obstructive pulmonary disease and creatinine levels. At 1-year, mitral regurgitation grade also predicted mortality. “This reflects the frailty of those patients,” he explained.
“That’s probably the stronger message,” Manoharan said. “People who are thin at that age were probably smokers, and they are thin not because they are fit. They are thin because there are other comorbid issues.”
- Prior Renal Impairment, Low Body Weight Predispose to Acute Kidney Injury After TAVR
- PARTNER: Post-TAVR Survival Higher in Overweight, Obese Patients
- ‘Obesity Paradox’ Observed in TAVR Patients
Spaziano M. Adverse effects of low body weight on outcomes in patients undergoing TAVI or surgical aortic valve replacement. Presented at: EuroPCR 2016. May 18, 2016. Paris, France.
- Spaziano reports no relevant conflicts of interest.