Study: Short-term Outcomes of Non-CABG Cardiac Surgery Not Impacted by Antiplatelet Therapy

A recent study has found that there is no correlation between recent antiplatelet therapy and outcomes after non-coronary artery bypass grafting (CABG) surgery.

The purpose of the study, presented at the 65^th Annual Meeting & Exhibition of the Southern Thoracic Surgical Association, was to assess mortality and morbidity in relation to antiplatelet agent exposure within five days of non-CABG cardiac surgery, according to presenter and study author Cecillia Lui, MD, of Johns Hopkins Hospital in Baltimore. The study researchers collected data from the Maryland Cardiac Surgery Quality Initiative (MCSQI), which included data from Maryland’s 10 cardiac centers, on non-CABG cardiac surgery patients between July 2011 and December 2016.

According to the study abstract, researchers found 9,611 non-CABG cardiac surgery patients, of which 974 had exposure to a non-aspirin antiplatelet agent within five days of surgery. Antiplatelet exposure patients were older (72.5 years vs 61.5 years, P < 0.001) and more likely to have diabetes (38.8% vs 22.5%, P < 0.001), be on dialysis (4.3% vs 3.1% P = 0.04), have hypertension (87.2% vs 66.2%, P < 0.001), have peripheral arterial disease (16.7% vs 6.0%, P < 0.001), and be undergoing a reoperation (37.5% vs 22.3%, P < 0.001). Propensity matching was used to control for confounding factors including age, gender, race, body mass index, tobacco use, diabetes, preoperative estimated glomerular filtration rate, type of surgery, urgency of the surgery, and re-operative surgery. Researchers analyzed 30-day mortality using Cox survival estimates.

After propensity matching, there were 642 patient pairs. Researchers did not observe significant differences between the groups in reoperation for bleeding, blood products transfused, postoperative stroke, postoperative renal failure, and 30-day readmission rates. Both groups had similar survival rates. In adjusted analyses, the factors most likely to impact mortality in antiplatelet patients were peripheral arterial disease (hazard ratio [HR] 2.25), lower preoperative hematocrit (HR 0.94), urgent case status (HR 1.82), and emergent/salvage case status (HR 9.48).

“Exposure to antiplatelet therapy within five days of non-CABG cardiac surgery is not associated with an increase in 30-day mortality or perioperative morbidity in a propensity-matched sample,” Lui concluded.

The study had several limitations, Lui said during her presentation. The study was retrospective and limited to MSCQI variables, excluding information such as antiplatelet type and exposure timing. Since it was a multi-center study, there was also data entry variability, as well as incomplete data from some centers. The study size was also relatively small.

During discussion, Mario Gaudino, MD, of Weill Cornell Medicine in New York City, raised questions about the use of propensity matching in Lui’s research and others’ research as well.

“There is a biological and clinical reason why a patient is taking antiplatelet agents or not. By using propensity matching. […] The patients are still different, and there is no statistical adjustment that you can use” to account for that, he noted. “We always have to remind ourselves that there is no statistical adjustment that can make patients that are not comparable, comparable.”

Another audience member pointed out that some drugs are more powerful than others, and some cause significant bleeding in patients, which would result in many transfusions.

“The results of this study mean nothing in the sense of clinical decision-making for each patient, because there is such a variety in the antiplatelets used. These results should be taken with a grain of salt,” said Lui added.

Ed Savage, MD, of Cleveland Clinic Florida located in Weston, questioned the cutoff time of five days and said in his own experience he normally operates much sooner than that.

He surmised that most patients were probably on clopidogrel, and if so, “you’re not really going to show that there’s a bleeding problem because in five days, most of the clopidogrel effect is going to be gone anyway,” he said. “The other aspect of this, too, is did they get clopidogrel because they came to the ER and they just got a loading dose, or had they been on clopidogrel for a couple of years? It would be important to break that down.”