Long-term Secondary Prevention Post-CABG Important Yet Lacking: SWEDEHEART

PARIS, France—Following CABG surgery, use of secondary prevention medications like statins and renin-angiotensin-aldosterone system (RAAS) inhibitors is high at 6 months after discharge but falls over the ensuing years, according to results from the SWEDEHEART registry. Both of these drug classes were associated with a significant reduction in mortality risk over time, underscoring the importance of long-term adherence.

“Part of the problem with secondary prevention [is] that you're not treating symptoms but instead you're trying to better the prognosis,” said Erik Björklund, MD (Sahlgrenska Academy, Gothenburg, Sweden), who presented the SWEDEHEART results yesterday in a Hot Line session here at the European Society of Cardiology Congress 2019. When people start to feel “fine” a year or two after CABG, that’s when they stop taking their meds, he told TCTMD. For physicians, “it means that you need to stay sharp. CABG is not a cure for coronary artery disease, but it's symptom-relieving. Coronary artery disease is chronic and progressive in both the native vessels and grafts. Therefore, you need to continue treating it.”

“With bypass surgery, medications definitely get overlooked a lot of the time,” Martha Gulati, MD (University of Arizona, Phoenix), who was not involved with the study, commented to TCTMD. “Saying to someone, ‘Okay, you have to take the aspirin forever, you have to take a statin forever,’ it is harder for patients to accept that they need a medication to control their disease.”

In an unexpected finding, beta-blockers did not appear to be protective against mortality over time, and this, said Gulati, might represent an opportunity. “If a beta-blocker has minimal effect and isn't protective, maybe that's a way for us to simplify our medication regime,” she said.

Surprise With Beta-blockers

For the study, Björklund and colleagues included 28,812 patients from the SWEDEHEART registry who underwent isolated CABG between 2006 and 2015 and survived to at least 6 months after hospital discharge.

Use of preventive medications was generally high but decreased over time, most steeply after the first year. At 6 months postdischarge, prescriptions for statins, beta-blockers, RAAS inhibitors, and antiplatelet agents were given to 93.9%, 91.0%, 72.9%, and 93.0% of patients, respectively. Eight years later, these drugs were only dispensed to 77.3%, 76.4%, 65.9%, and 79.8%, respectively.

Over a median follow-up of 5 years, after adjusting for age, sex, comorbidities, and use of other secondary prevention medications, statins, RAAS inhibitors, and antiplatelets were significantly associated with a lower risk of mortality, but beta-blockers were not.

Medication Use and Mortality: 5-year Median Follow-Up

There were no differences observed between women and men with regard to prescription prevalence, but those older than 75 years were less likely to receive secondary prevention medications compared with younger patients. “The survival benefits we observed were across ages, so our study does not support treating patients over 75 differently to younger patients,” according to Björklund.

In the subgroup of patients with reduced LV function, beta-blocker use still appeared to have no interaction with mortality.

This was perhaps the biggest surprise of the study, Björklund said, offering some explanations. “You need to keep in mind that we had a very crude categorization of left ventricular function, with over and under 50% of ejection fraction, that's perhaps one reason. This is a subgroup analysis on the patients with reduced left ventricular function and we plan on digging deeper. . . . It's an ongoing matter of investigation.”

Notably, the researchers did not have any information on why patients didn’t receive secondary prevention, “so we could not differentiate between legitimate reasons, such as contraindications, from doctors’ nonadherence to guidelines or patients’ nonadherence to prescriptions,” he said. “Also, we lacked a few variables like smoking, which has been shown as an important risk factor.”

Future Focus

“There was a presumption that [beta-blockers] were beneficial, but remember they were introduced before a lot of our stronger and more potent and more studied drugs,” Gulati said. “So I think that we need a future study of what should you get post-bypass, perhaps looking at the post-MI group versus the non-MI, elective revascularization [patients] and trying to figure out what medications are actually necessary and which ones actually help people.”

This will not be an easy study to bring about because “everybody wants to do studies with the newest, latest, greatest drugs because there is pharma money behind them, but I do think that this is something that I would hope the [National Institutes of Health] would focus on because that's probably the only way such a study is going to get done,” she continued.

Additionally, Gulati stressed the importance of cardiac rehab not only for the exercise programs they provide but also for the education. “They teach you a lot about medication, and when you understand why to take a medication, you might be more likely to take it,” she said, adding that a study looking at cardiac rehab and medication adherence would also be important. “It'd be interesting to see who completed cardiac rehab, those who didn't go, and [who was] more likely to take the medication.”

Cecilia Linde, MD, PhD (Karolinska Institute, Stockholm, Sweden), who co-chaired a media briefing, told TCTMD that the prescription of secondary prevention medications after CABG is “not optimal in Sweden or elsewhere. As time goes on, even patients think ‘Why am I taking this drug if I'm feeling well?’ So I think there is a major pedagogy problem to make them motivated to continue therapy.” Physicians have a responsibility to fix this, but family members and nurses can play a role as well, she said.