An analysis of data from more than 100,000 patients with multivessel coronary artery disease undergoing coronary artery bypass graft (CABG) surgery or percutaneous coronary intervention (PCI) has reopened debate on controversial guidelines concerning coronary revascularisation.
Findings of the analysis, involving data from the US Centers for Medicare and Medicaid Services, were presented by cardiac surgeon J Hunter Mehaffey (West Virginia University, Morgantown, USA) at the 59th annual meeting of The Society of Thoracic Surgeons (STS 2023; 21–23 January, San Diego, USA).
The research was instigated following the publication of guidelines from the American College of Cardiology (ACC), the American Heart Association (AHA) and the Society for Cardiovascular Angiography and Interventions (SCAI) in December 2021, which downgraded the indications for CABG from a class 1 recommendation to a class 2B in three-vessel coronary disease, a recommendation that left the cardiothoracic surgery world “shocked”, according to Mehaffey.
In a press release promoting the findings of the study, the STS—which pointedly declined to endorse the guidelines upon their publication in 2021—said that the guidelines rely heavily on data from the ISCHEMIA trial, which compared an initial invasive approach versus a conservative approach in patients with stable coronary artery disease. However, STS claims that the majority of patients in the ISCHEMIA trial were not representative of US patients undergoing CABG, and therefore the study did not fully represent the comparative benefits for patients who had multiple blockages in their coronary arteries.
The latest analysis, which was performed by a team of cardiac surgeons, cardiologists, and researchers at West Virginia University, included outcomes over a three-year period, from 2018‒2020, capturing data from the US Centers for Medicare and Medicaid Services database for patients undergoing isolated CABG or multivessel PCI for acute coronary syndrome.
“We used one of the largest and most inclusive databases of patients hospitalised in the USA, including all patients over the age of 65 on Medicare,” said Mehaffey. “We performed a very robust statistical analysis including propensity score balancing to help ensure that the groups of patients who underwent stenting versus those who underwent bypass surgery were well matched and well balanced in order to compare their outcomes.”
The population included 104,127 patients with multivessel coronary disease, with more than 51,000 patients undergoing CABG and 52,000 undergoing PCI following the application of exclusion criteria.
According to Mehaffey, the analysis demonstrated a significantly lower hospital mortality for the patients who underwent CABG compared to those who underwent PCI. “CABG was associated with significantly improved longitudinal survival, with a nearly 60% reduction in all-cause mortality at only three years,” Mehaffey told delegates at the STS meeting, a finding that was met with a smattering of applause from members of the audience.
Additionally, the researchers found a marked reduction in both 30-day and three-year readmissions for myocardial infarction (MI). CABG patients were also significantly less likely to need any additional stenting or intervention on their coronary arteries during those three years, Mehaffey reported.
In discussion that followed the presentation at STS, speakers agreed upon the need to reappraise the recommendations within the ACC, AHA and SCAI guidelines based upon the analysis. Mehaffey commented that the findings underscore the importance of physicians “reading the fine print” when it comes to interpreting guidelines into their own practice.
However, speaking to Cardiovascular News, interventional cardiologist and clinical trialist David J Cohen (St Francis Hospital and Heart Center, Roslyn, USA) cautions against overplaying the results of the study, arguing that the use of observational data, rather than randomised trial data, limit the conclusions that can be drawn from the analysis.
Cohen questions the use of Medicare data as the basis for the study, commenting that these “provide very little in the way of granular information” such as angiographic complexity, SYNTAX score, left ventricular function, or other parameters—such as frailty– that may influence long term outcomes among these patients. “The simple answer is that the claims data are insufficient to truly risk adjust this comparison,” he says.
Further to this, Cohen suggests that the investigators have “failed to level the playing field” between the two therapies. “That can be seen in their risk-adjusted outcome curves that diverge in favour of bypass surgery almost immediately,” he says, which runs counter to trends seen in randomised trial data, which take several years (or more) to emerge.
“If you look at the randomised trial data that support a survival benefit of bypass surgery over PCI in patients with three-vessel coronary disease the treatment effect is about a 20% relative risk reduction,” Cohen adds. “Here they found in their data almost a 60% relative risk reduction—another indication that there are major unmeasured differences between the 2 groups that have not been adequately accounted for in the analysis.”
Asked if he saw a route to moving this debate forward, Cohen commented that more randomised trial data are likely to be the only way to adequately inform the debate. “I wish that our colleagues would divert the time, energy and effort that they put into these types of studies into designing and conducting randomised trials that would really inform the question,” he concludes.