Sinus bradycardia during therapeutic hypothermia lowered mortality after cardiac arrest

Patients undergoing therapeutic hypothermia after out-of-hospital cardiac arrest who experienced sinus bradycardia had a lower mortality rate compared with patients who did not experience sinus bradycardia, researchers reported at Acute Cardiovascular Care 2014.

An observational cohort study included 234 comatose survivors of out-of-hospital cardiac arrest who underwent a 24-hour therapeutic hypothermia protocol, in which the body was cooled to 33°C. All patients had a shockable primary rhythm.

The researchers hypothesized that sinus bradycardia achieved during therapeutic hypothermia might confer less neurological damage and better mortality.

The patients’ heart rhythms were registered hourly during the protocol and were stratified by incident sinus bradycardia, defined as less than 50 bpm, or no sinus bradycardia. The primary endpoint of the study was mortality at 180 days.

Forty-nine percent of patients experienced incident sinus bradycardia during therapeutic hypothermia, according to data presented during the Young Investigator Award session. Those with sinus bradycardia were, on average, younger (57 years vs. 63 years; P<.001) and less likely to have known HF (7% vs. 19%; P<.01) compared with those who did not experience sinus bradycardia.

The 180-day mortality rate was 17% for patients who experienced sinus bradycardia compared with 30% for patients who did not experience sinus bradycardia (HR=0.38; 95% CI, 0.22-0.65).

Sinus bradycardia remained independently associated with a lower 180-day mortality rate after adjustment for sex, age, comorbidity, witnessed arrest, bystander cardiopulmonary resuscitation and time to return of spontaneous circulation (HR=0.51; 95% CI, 0.29-0.9).

“We also found that sinus bradycardia was directly associated with a better neurological status 180 days after the arrest,” Jakob Hartvig Thomsen, PhD candidate in the department of cardiology at The Heart Centre, Copenhagen University Hospital Rigshospitalet, said in a press release. “Now when we observe that a patient experiences sinus bradycardia below 50 bpm within the first 24 hours, we can tell families that their relative may have a chance of recovery. Our findings provide an early marker of patients who may do well. Hopefully in the future, together with other tools, we will be able to differentiate between those with a very good or very poor prognosis so we can prioritize intensive care resources.”

For more information:

Thomsen JH. Abstract #505. Presented at: Acute Cardiovascular Care 2014; Oct. 18-20, 2014; Geneva.

Disclosure: Thomsen reports no relevant financial disclosures.