CHILL-MI Published: Results Show Some Benefit to Cooling in Primary PCI

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While hypothermia before and during percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI) patients failed to reduce the primary endpoint of infarct size in the CHILL-MI trial, the approach was associated with a significant reduction in heart failure. In addition, according to a paper published online February 5, 2014, ahead of print in the Journal of the American College of Cardiology, the cooling method shows potential in treating anterior STEMI of short duration.

Results from CHILL-MI were previously presented at the annual Transcatheter Cardiovascular Therapeutics scientific symposium in San Francisco, CA, in October 2013.

For the multicenter trial, researchers led by David Erlinge, MD, PhD, of Skane University Hospital (Lund, Sweden), enrolled 120 STEMI patients within 6 hours of symptom onset who were slated to undergo PCI. Patients were randomized to standard of care (n = 59) or hypothermia (n = 61) induced by endovascular cooling and rapid infusion of 600 to 2,000 mL cold saline. Hypothermia was initiated before PCI and continued for 1 hour after reperfusion, with a target temperature of 33°C.

Infarct Size Unaffected

Baseline tympanic temperature was 36°C in both groups. For the hypothermia group, average temperature at the time of reperfusion was 34.7 ± 0.6 degrees; core body temperature decreased to 35°C or below in 76% and 35.4°C or below in 91%.

Hypothermia lengthened the randomization-to-balloon time by 9 minutes (42.7 ± 16.6 minutes vs 33.3 ± 21.2 minutes for controls). The treatment was performed successfully in all but 1 patient in the study group, while 1 of the controls received hypothermia in error.

The primary endpoint of infarct size normalized to myocardium at risk did not differ between the 2 groups. Exploratory analysis suggested, however, that anterior infarcts treated within 4 hours of onset may be more likely to benefit (table 1).

Table 1. Infarct Size/Myocardium at Risk

At 45 days, hypothermia was associated with lower incidence of heart failure (2 vs 8 events; P = 0.047); all events occurred in patients with anterior STEMI. There were no deaths or strokes in either group. Rates of pneumonia, ventricular arrhythmias, bradycardia, reinfarction, and major bleeding were similar irrespective of treatment.

Researchers Push for Further Study

While “using a combination of cold saline infusion and endovascular cooling prior to reperfusion in awake STEMI patients was feasible and safe with only a small delay time in reperfusion, it did not significantly reduce [infarct size],” the researchers conclude.

But Dr. Erlinge and colleagues say it is “logical to further explore the potential cardioprotective effects of hypothermia in a new study focusing only on anterior STEMI with short duration (< 4 hours from symptom onset to PCI).”

In an e-mail, Dr. Erlinge told TCTMD that anterior STEMI patients are at greatest “risk of developing severe heart failure and risk of malignant arrythmias with a need for ICD implantation. So this is the group with a need for cardioprotection and improved treatment.”

Another lesson of the current study, he said, is the feasibility of the technique. “[H]ypothermia was easily adopted at 9 sites and well tolerated by patients. We did not see any adverse effects,” Dr. Erlinge noted. “The time to place the cooling catheter is just a few minutes, and with a short cooling protocol of 1 hour, it has very little effect on standard of care.”

Study Details

Mean time from symptom onset to randomization was 132 minutes in the hypothermia group and 129 minutes in the control group. All but 3 patients received PCI, and 1 attempted PCI case was unsuccessful. TIMI 3 flow was established in 93% of hypothermia patients and 90% of controls. Most patients were treated using ticagrelor or prasugrel (89% of hypothermia and 84% of control patients) and thrombus aspiration (59% and 69%, respectively).

Meperidine was given to all hypothermia patients in the cath lab to suppress shivering. Additionally, 71% received buspirone.

 

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Source:
Erlinge D, Götberg M, Lang I, et al. Rapid endovascular catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction (The CHILL-MI trial): A randomized, controlled study of the use of central venous catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction. J Am Coll Cardiol. 2014;Epub ahead of print.

 

 

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