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Thrombotic events that occur during percutaneous coronary intervention (PCI) are associated with poorer patient outcomes, a study found.

Patients with intraprocedural thrombotic events had double the risk of major adverse cardiovascular events and more than triple the risk of mortality at 30 days compared with those whose frame-by-frame core laboratory angiographic analysis showed no such events (both P<0.0001),, of Columbia University Medical Center/New York-Presbyterian Hospital in New York City, and colleagues reported in JACC: Cardiovascular Interventions.

Intraprocedural stent thrombosis had the strongest (hazard ratio 7.51, 95% confidence interval 4.36-12.94), as well as major bleeding (HR 4.47, 95% CI 2.44-8.20) and death (HR 7.47, 95% CI 3.21-17.39).

No or slow reflow, new or worsened thrombus, distal embolization, abrupt closure, or stent thrombosis during the procedure also individually showed links to those negative outcomes at 30 days,

"Most interventional cardiologists feel that when a patient leaves the cardiac catheterization laboratory with a patent vessel, adequate lumen, and intact flow, clinical success is nearly guaranteed," , of Houston Methodist DeBakey Heart and Vascular Center, wrote in an accompanying editorial.

He suggested that the reality is quite different, "particularly for patients undergoing PCI for acute coronary syndromes."

While the findings "are likely to contain an element of survivor bias, they still suggest that improved management of thrombotic risk in the cath lab is likely to have a major impact on post procedural outcomes," wrote Kleiman.

He found that "a back of the envelope calculation of attributable risk percentage reveals that 48% of major adverse cardiac events, 70% of the deaths, and 62.5% of the stent thromboses that occur by 30 days could be prevented if intraprocedural thrombotic events were eliminated."

"It has become time to develop a new logic to test evolving therapies," wrote Kleiman. "Deferred stenting, the intriguing approach of performing primary PCI but delaying stent implantation by several hours or days until the culprit lesion is less thrombus-laden had much merit in a pilot study but its widespread implementation is likely to be logistically challenging," he noted, adding that "a variety of new antithrombotic approaches merit consideration" as well.

For now, unfortunately, "the optimal treatment strategy for new/worsened thrombus or intraprocedural stent thrombosis remains elusive," the authors wrote. Similarly, there are few options for cases of no-reflow.

The identification of risk factors for intraprocedural thrombotic events may be a first step towards refining PCI for certain groups.

"Several authors have identified rudimentary risk factors for intraprocedural thrombotic events, including STEMI [ST-segment elevation myocardial infarction] presentation, high white blood cell count, large thrombus burden, bifurcation stenting and stent length. Developing a score that includes such risk factors would go a long way toward developing a target group in whom newer therapies could prove useful," according to Kleiman.

The investigators pooled data from the ACUITY and HORIZONS-AMI trials, which included 6,591 patients who underwent stent implantation for STEMI, non-ST-segment elevation myocardial infarction (NSTEMI), or unstable angina.

Intraprocedural thrombotic events emerged during 7.7% of interventions. No or slow reflow made up the majority of thrombotic events at 58.0%, followed by new or worsened thrombus (35.3%), distal embolization (34.9%), abrupt closure (19.8%), and intraprocedural stent thrombosis (9.5%).

Intraprocedural thrombotic events occurred more frequently in STEMI patients than the NSTEMI/unstable angina population (12.2% versus 3.5%).

Kirtane and colleagues acknowledged that their study was limited by different baseline characteristics between those who did and did not experience intraprocedural thrombotic events. "We found that patients with significant risk factor burden (diabetes, hypertension, coronary disease) experienced lower intraprocedural thrombotic events, a finding that might be explained by better baseline medical therapy or heightened practitioner awareness in these patients with greater baseline risk," they explained.

"The occurrence of intraprocedural thrombotic events is not infrequent among high-risk acute coronary syndromes patients undergoing PCI," concluded the researchers. "The objective assessment of individual components of intraprocedural thrombotic events may contribute to future therapeutic strategies aimed at minimizing adverse clinical outcomes."

From the American Heart Association: