Higher Mortality, Costs for Underweight Patients Following Cardiac Catheterization

Despite receiving cardiac catheterization at lower rates than other weight categories, underweight patients were more likely to die, be readmitted, and have higher hospital costs.

Being underweight — not overweight – carries the highest mortality, cost, length of stay, and readmission rate for cardiac catheterization patients, according to analysis from the European Society of Cardiology (ESC) Congress in Barcelona.

The study analyzed body mass index’s (BMI) association with in-hospital rates of mortality, cost, length of stay and readmission within a 30-day period for patients undergoing coronary angiography in a 2013 cohort.

1,035,727 patients underwent cardiac catheterization in 2013, with 42% receiving percutaneous coronary intervention (PCI) with a stent or balloon. Split into categories by BMI, 0.4% of patients were underweight (BMI <19 kg/m2), 11.4% were obese (BMI 30.1-40 kg/m2), and 8.0% were morbidly obese (BMI >40 kg/m2).

“Elevated BMI is a risk factor for coronary artery disease, yet studies have shown that overweight and obese patients actually have fewer complications and better clinical outcomes after revascularization using PCI — a phenomenon dubbed the obesity paradox,” Afnan Tariq, MD, an interventional cardiology fellow, Lenox Hill Hospital, in New York, said in a statement.

When it came to cardiac catheterization, only 25.8% of underweight patients went on to receive PCI, compared to 32.5% of morbidly obese, 41% of the overweight, 41% of the obese, and 43.2% of the normal weight patients.

Despite the lower rate of PCI and cardiac catheterization, the underweight patients were more than 3 times as likely to die after cardiac catheterization (6.0% mortality) than the morbidly obese (1.9%) and overweight (1.7%), 5 times more likely than obese patients (1.2%), and twice as likely as normal weight patients (2.3%).

“The obesity paradox has flummoxed researchers for some time, and our research also flips the conventional wisdom that a higher BMI should portend a worse outcome,” Tariq said. “We found that the lower BMI group had worse outcomes across the board, including readmission, length of stay, cost, and mortality.”

Length of stay for underweight patients was an average of 10.5 days compared to 5.1 days for normal weight, which resulted in nearly 50% higher costs ($33,540 compared to $22,581). Although, the morbidly obese tended to stay slightly longer and have higher costs than normal weight patients (6.2 days, $23,889 cost).

Underweight patients were also 18% more likely to be readmitted within 30 days compared to normal weight patients, and 8.2% more likely than morbidly obese patients.

“Further research will certainly add to the growing body of evidence, but the scales seem to be tipping in favor of higher BMI patients having better outcomes than normal weight patients,” Tariq said. “This study also reinforces the notion that the frail, those with the lowest BMI, have the worst outcomes - suggesting that when it comes to cardiac catheterization, the smaller they are, the harder they fall.”

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