Good Coronary Collateral Circulation? Better LVEF and Survival After STEMI

NATIONAL HARBOR, MD—STEMI patients with good coronary collateral circulation undergoing PCI are more likely to be alive at 2 years and have better cardiac function when compared with STEMI patients without good collateral flow, a new study shows.

Presented this week at CRT 2020, the study showed that among 1,952 patients with TIMI flow 0 to 1 sent for PCI, 88% of those with good coronary collateralization—defined as a Rentrop score of 2 to 3—were alive at 24 months compared with 71% of those with poor coronary flow (P < 0.001). Similarly, left ventricular ejection fraction was significantly better in patients with good coronary collateralization, investigators said.

Lead investigator Ali Aldujeli, MD (Lithuanian University of Health Sciences, Kaunas), said that when performing coronary angiograms in STEMI patients, he’d often feel reassured with the presence of collateral flow. “Seeing evidence of coronary collaterals, I felt a little safer, but me feeling safer wasn’t based on any studies or any data,” he told TCTMD. “It was based a little on experience and feeling. Then the idea came that we should study whether the collaterals really affected the outcomes of the patient.”     

The impact of collateral flow on LVEF and prognosis in patients with STEMI is somewhat uncertain, he said. One recent meta-analysis, which included more than 10,400 patients with STEMI undergoing PCI, showed that good coronary collateralization reduced the risk of long-term mortality (≥ 6 months), as well as reduced the risk of in-hospital and 30-day mortality. There was no difference in the risk of MI or target vessel revascularization between patients with and without collateral circulation.

In the Lithuanian study, the average age of patients was 65 years and the majority required treatment of either the left anterior descending artery (49%) or right coronary artery (40%). Coronary collateral filling was visually assessed during the invasive coronary angiogram.

In total, 78% of patients had a Rentrop score of 0 to 1, meaning there was either no filling at all of the collateral vessel or filling of the collateral vessel without any epicardial filling of the target artery. By contrast, 22% had a Rentrop score of 2 to 3 (partial or complete epicardial filling by collateral vessels of the target artery). The culprit artery in patients with poor collateralization was more likely to be the left circumflex artery while patients with a culprit lesion in the right coronary artery tended to have good coronary collateralization, said Aldujeli.

In addition to the survival advantage at 2 years, LVEF at 6 months ranged from 50% to 55% in patients with a Rentrop score of 2 to 3, which was significantly better than the 40% to 45% observed in those with poor coronary collateralization (P < 0.05).

Collateral Benefits

“We were amazed by the results,” said Aldujeli. “There’s a very big impact, but it’s logical. The myocardial and endocardial areas that were not supplied with blood through collaterals were almost deprived for 1 or 2 hours without any blood flow. For patients with good collaterals, they had some blood supply during the hours of acute MI, and their ejection fraction remained nearly normal. This study changed our perspective because we were seeing the collaterals, but not really evaluating them. For me, now, I evaluate them, but it’s not used widely in clinical practice.”

Abdul Ihdayhid, MBBS, PhD (Monash Heart, Melbourne, Australia), the session cochair, said knowing there is good coronary collateralization can provide some reassurance the patient will be relatively stable during the procedure. He noted that the symptom-to-balloon time was much longer in STEMI patients with well-established collateral circulation, suggesting that they weren’t having as much ischemia as those without good collateralization.

“Anecdotally, we see it in the cath lab,” Ihdayhid told TCTMD. “It’s the 40-year-old guys who end up in the lab, they’ll have a flush occlusion of the LAD and go down the [drain] whereas there are others who have had a chronic occlusion that’s been getting narrower over the years, but they’re much more stable. . . . Or if we dissect an artery that was completely normal, the patient does really badly. Their heart’s never seen ischemia before.”

Commenting on the longer time from symptom onset to reperfusion in patients with good collaterals, Aldujeli agreed with Ihdayhid that the patients likely experienced milder ischemic symptoms, noting that these STEMI patients also reported lower pain scores than those with poor coronary collateralization.  

One of the major questions, said Ihdayhid, is if good coronary collateralization leads to better LVEF and survival after STEMI, what is it that leads to the development of coronary collateralization? “Is it ischemic preconditioning?” he asked. “Over time, if you’re getting chronic exposure to ischemia, your body is preconditioned to it, you’re more likely to develop good collaterals.” He noted, however, that trials testing ischemic preconditioning haven’t exactly panned out. In studies of remote ischemic preconditioning, the evidence is mixed with respect to protecting against ischemic reperfusion injury or improving short-term clinical outcomes, for example.  

To TCTMD, Aldujeli said an assessment of coronary collateral flow might one day be used to help physicians determine how STEMI patients respond to PCI. While collateral flow was a significant predictor after adjusting for several baseline variables, including LVEF, he stressed that larger, randomized studies are still needed to confirm their findings.