Periprocedural MI Predicts Mortality After PCI for Chronic Total Occlusion

Patients who experience MI during PCI for a chronic total occlusion (CTO), even when the procedure is successful, have an increased risk of death in subsequent years.

In a study published in the November 14, 2016, issue of JACC: Cardiovascular Interventions, patients who required a greater number of stents, were treated for multiple lesions, had renal dysfunction, were treated with a retrograde approach, or had clinical ACS presentation were at increased risk for periprocedural MI. Such MIs were associated with greater mortality in the long term.

Researchers led by Seung-Whan Lee, MD, PhD (Asan Medical Center, Seoul, Korea), note that data on the prognostic relevance of periprocedural MI after PCI in CTO patients is sparse and say their findings “might be helpful when planning a treatment strategy for patients with complex coronary artery disease including CTO.”

Periprocedural MI was defined as a postprocedural CK-MB increase of more than three times the upper reference limit (URL) of the assay. Serial CK-MB values were obtained 1 to 3 hours before PCI and at 6 hours after the procedure. In cases of elevated CK-MB or chest pain, measurements were taken again at 12 hours, with additional testing at the discretion of the treating physician.

CK-MB Cutoff Values High

Periprocedural MI occurred in 11.4% of the 1,058 study participants during PCI. Of those, peak CK-MB values were three to five times the URL, five to 10 times the URL, and > 10 times the URL in 36.4%, 38.8%, and 24.8% of patients, respectively. CTO length and total lesion length incorporating CTO were longer in the periprocedural MI group, and multivessel disease was more frequent, with more of these patients undergoing concomitant PCI for nontarget lesions.

Over a median follow up of 4.4 years, the mortality rate was 8.4%. Compared with patients who did not have a periprocedural MI, those who did had a higher adjusted risk of death (HR 1.86; 95% CI 1.09-3.17). Analysis of peak CK-MB cutoff values showed a correlation between mortality and increased values, but only at 10 times the URL (HR 2.67; 95% CI 1.13-6.30).

Lee and colleagues say their findings are not surprising since the “prognostic value of [periprocedural MI] would depend on the presence and severity of irreversible myocardial injury.” But the situation is complicated, they add, by lack of both symptoms and electrocardiographic or echocardiographic changes in the majority of patients with periprocedural MI. Therefore, whether the latter “is a direct cause of mortality or it functions as a simple marker of an atherosclerotic burden and the procedural complexity is uncertain,” they add.

The investigators also looked at the 173 patients in their study who failed PCI for CTO. Within this subgroup, there was a numerically higher cumulative rate of mortality with increasing CK-MB elevations, but this pattern did not reach statistical significance.

Data Support SCAI Definition

In an accompanying editorial, Gregg W. Stone, MD (NewYork-Presbyterian Hospital/Columbia University Medical Center, New York, NY), notes that three major working groups have all defined periprocedural MI differently. The findings from the current study, he says, reinforce the definition proposed by the Society for Cardiovascular Angiography and Interventions (SCAI) in 2013. In their position paper, the SCAI authors suggested that a post-PCI elevation of CK-MB to 10 times or greater the upper limit of normal (ULN) is the prognostically important threshold for clinically relevant periprocedural MI. Conversely, the third universal definition from the Global MI Task Force relies on troponin measurements, specifically a measure of more than five times the ULN in the first 48 hours, plus clinical or ECG features. The Academic Research Consortium’s biomarker criteria include troponin or CK-MB elevations of more than three times the ULN.

According to Stone, the current study, “adds to the weight of evidence that only large post-PCI biomarker elevations (ie, extensive myonecrosis) are prognostically important.”

But he says more data are needed on the relationship between periprocedural MI and prognosis in other patient populations, and in the context of troponins. Furthermore, he suggests that outcomes other than death should be examined. These include angina, heart failure, left ventricular function, exercise performance, and quality of life.

“Such studies should ideally be prospectively performed, large (n = > 5,000), and have routine frequent biomarker draws (every 8 hours, 3 times),” Stone adds.

In an email to TCTMD, Harvey D. White, MB ChB DSc (Auckland City Hospital, Auckland, New Zealand), co-chairman of the third universal definition, pointed out that among the 30 patients in the study with > 10 times elevation of CK-MB, there were only six deaths. He said it is unclear how many of those were cardiac related. The numbers, he added, are simply too small to draw any conclusions. White also noted that in contrast to the recommendations of the universal definition, Lee and colleagues did not use different cut points for CK-MB for men and women.

“The fourth universal definition is being discussed at the moment and will be presented in 2018,” White told TCTMD. “It’s likely that cut points for troponin (which is recommended over CK-MB) will be increased. Isolated elevations of biomarkers are not part of the definition and associated features (as in the third universal definition), will be required, such as ECG or imaging changes, or angiographic findings consistent with a procedural complication such as coronary dissection, loss of collateral flow, slow flow or no reflow, or coronary thrombus.”