Out-of-Hospital Cardiac Arrest Protocol With Cooling, Angiography Gets ‘Extraordinary’ Results

Data from the HACORE registry show what can be done with a strategic approach and should discourage complacency, the editorialist says.

Out-of-Hospital Cardiac Arrest Protocol With Cooling, Angiography Gets ‘Extraordinary’ Results

Therapeutic hypothermia and coronary angiography likely play an important role in improving survival following out-of-hospital cardiac arrest (OHCA), according to a new study that followed a strict protocol which included both strategies.

Real-world data from the HACORE registry imply that adhering to this multifaceted protocol can slash mortality rates, even in patients similar to those included in a previous study, the TTM trial, that led to “severe uncertainty” about the value of therapeutic hypothermia in this setting, investigators say.

The protocol, employed at a single German center, incorporates CT imaging, cardiac catherization and revascularization, active hemodynamic support for cardiogenic shock, and mandatory therapeutic hypothermia at 32°C for 24 hours. Results of the experience were published online earlier this week in JACC: Cardiovascular Interventions.

Overall 30-day mortality was 41% in the registry. Homing in on the patients that matched the inclusion/exclusion criteria of the TTM trial—whose results in 2013 led to questions about the benefits of cooling to 33°C versus maintaining a core temperature of 36°C—the rate was 27%. By comparison, 30-day mortality was 44% in the TTM trial.

Asked by TCTMD how much of their protocol’s benefit comes from therapeutic hypothermia, senior author Andreas Schäfer, MD (Hannover Medical School, Germany), said it’s impossible to isolate.

“We cannot identify one of the parts of our protocol and attribute the observed effect on it alone. But it is very likely that therapeutic hypothermia plays an important role,” he explained via email, citing the experience of another group in Australia, whose mortality rate and neurological outcomes worsened when they switched from hypothermia to normothermic therapy.

“However,” Schäfer continued, “we believe that we cannot save all patients with hypothermia without revascularizing the ones with occluded coronaries, and not all of them have ST-segment elevations. Our strategy aims to treat all reversible causes of arrest and provide the best neurological protection [that has] been tested in other trials.”

Michael Mooney, MD (Minneapolis Heart Institute Foundation, MN), who wrote an editorial accompanying the paper, told TCTMD that the central point of the paper is that “they’re showing they can get extraordinary results. And if they can get them using systems of care, then the onus is on us to replicate that by developing systems of care that allow for similar success. It takes us away from the idea that we can be comfortable with where we are.”

Knowing that such good outcomes can be obtained with therapeutic hypothermia and standardized protocols for cardiac arrest management, he added, should “make us uncomfortable” and spur action. The potential for impact is great, said Mooney, who points out in his editorial that 300,000 people in the United States, for example, experience OHCA each year. “Survival rates are notoriously dismal (6% to 9%), and adverse neurological sequelae are common and disabling among survivors, with a minority experiencing a return to pre-event functional status,” he writes.

HACORE Registry

The researchers, led by Muharrem Akin, MD, and Jan-Thorben Sieweke, MD (Hannover Medical School), looked at 233 consecutive patients (median age 64 years; 78% men), with OHCA who were treated at their center between 2011 and 2015 according the Hannover Cardiac Resuscitation Algorithm before intensive care admission. Nearly three-quarters (72%) had ventricular fibrillation as the primary rhythm. The cause of OHCA was spontaneous acute MI in 49%, non-acute MI-triggered malignant arrhythmia in 39%, acute pulmonary embolism in 3%, and “other” in 9%. OHCA was witnessed 80% of the time, and 62% of cases received bystander CPR.

Return of spontaneous circulation was reached after a median of 20 minutes. Most patients underwent immediate coronary angiography (95%) and coronary intervention (56%). A critical coronary stenosis requiring PCI was seen in 62% of patients with and 52% of those without ST-segment elevation on ECG.

Admittedly, employing such a comprehensive strategy for OHCA care, while “not rocket science,” is difficult, Mooney noted to TCTMD. “It’s hard to do because there are a lot of moving parts and a lot of people who have to pull on the same rope, but . . . it can be done. That for me was a big takeaway.”

Leveraging regional STEMI networks, as was done by the Minneapolis Heart Institute’s Cool It protocol starting in 2006, may help get things started, he said. “We have already this well-oiled machine for acute MI. Why not build in a module for therapeutic hypothermia and cardiac arrest?”

Given the number of OHCAs occurring each year, there should be no complacency, Mooney stressed. Not everyone will survive, he said, “but a lot of these people are very salvageable—30- and 40-year-olds, 50- and 60-year-olds—and can be meaningfully helped. It’s hard work. It’s not sexy. It involves . . . a lot of suffering and families to talk to that aren’t happy with how things are going.” That said, with the right management, a sizeable proportion of individuals can live through their event, he added.

Further clarity on therapeutic hypothermia will likely come from the CAPITALCHILL trial comparing moderate versus mild cooling at 31°C or 34°C, respectively, in comatose survivors of OHCA, Mooney said.

But rather than waiting on more data, it’s important for clinicians to reflect on their outcomes and ask what can be done now, he emphasized. “The things that lead to improvement are knowable and they’re actionable, and they’re realistic to get done. It just requires a commitment to do it.”

For the Hannover group, Schäfer said, “a real step forward” in finalizing the strategy was cooperation among both the departments starting the protocol and the ones that would be affected by its implementation. Patient flow varies according to local conditions, but upfront planning helps, he explained.

  • This study was supported by the Deutsche Forschungsgemeinschaft, Klinische Forschergruppe 311, TP1.
  • Akin and Sieweke report no relevant conflicts of interest.
  • Schäfer reports receiving lecture fees from ZOLL and Abiomed and a research grant from Abiomed.
  • Mooney reports having served on the steering committee for ZOLL.