OHCA in Pregnancy: Extremely Rare, Often Deadly

Out-of-hospital cardiac arrest (OHCA) is extremely infrequent among pregnant and postpartum women and often occurs in the absence of CV risk factors and known heart disease, according to Australian registry data.

As the study authors report, the devastating events tended to be deadly, with a survival rate of 12.5%.

Just eight women in the state of Victoria, with a population of 6.7 million, experienced OHCA in conjunction with pregnancy over a recent 2-year period. This translates to 5.2 cases per 100,000 pregnancies, or around one in 20,000, much lower than the incidence rate of 23.1 per 100,000 seen there among all women of childbearing age.

Lead author Elizabeth D. Paratz, MBBS (Baker Heart and Diabetes Institute, Prahran, Australia), told TCTMD that their study, published this week as a research letter in JACC: Advances, is only the third ever to look specifically at the population of patients who have OHCA during or shortly after their pregnancy. “Cardio-obstetrics is a field that really is becoming a lot more recognized, . . . but we still lack data for a lot of important decision points,” she said.

Paratz pointed out that the OHCAs studied here are very different from pregnancy-associated in-hospital cardiac arrests, which tend to be related to obstetric or anesthetic issues. The in-hospital events “tend to be quite survivable. You’ve got the whole resource team on hand. Out-of-hospital cardiac arrests much more commonly have a cardiac problem underlying [them] and really high fatalities for the moms, unfortunately. . . . They’re two really different entities.”

Every woman who is pregnant should have their heart listened to. Elizabeth D. Paratz

Also noteworthy is that none of the women with OHCA were previously known to have a heart problem, she said. This is a reminder that pregnancy is a key time to check to see if there are any underlying issues that need to be addressed. For “women who are anticipating pregnancy, it’s a great time to evaluate their health and their cardiac risk factors, particularly with moms getting older and older and having more risk factors as they enter into pregnancy,” Paratz advised. “And of course, every woman who is pregnant should have their heart listened to, to make sure they don’t have a valve problem or hypertrophic cardiomyopathy.”

Half Died on the Scene

This research is part of a bigger project, the EndUCD (End Unexplained Cardiac Death) registry. “We built a statewide registry of ambulance, hospital, and forensic data across the state of Victoria, Australia. It captures every young, sudden cardiac arrest,” Paratz said.

Among the eight women in this analysis, seven were pregnant (gestational range 8 to 22 weeks) and one was 8 weeks postpartum. Their average age was 29.9 years. Apart from two women with obesity, there were no other CV risk factors present. None had seen a cardiologist or been evaluated at a specialized cardiac pregnancy clinic. One had a history of amphetamine and alcohol abuse.

Although five of the OHCAs were witnessed, just three of these women received bystander CPR. Two patients were found to have a shockable cardiac rhythm, and both underwent defibrillation. Two additional women had pulseless electrical activity and four presented with asystole.

Cardio-obstetrics is a field that really is becoming a lot more recognized, . . . but we still lack data for a lot of important decision points. Elizabeth D. Paratz

Half of the patients died on the scene, and half were hospitalized. Only one woman survived her hospital stay. None of the women had a cesarean section, as none of their fetuses were of viable age.

Importantly, “no OHCAs were directly attributable to the pregnancy,” the investigators note.

Five of the eight OHCAs (62.5%) had cardiac causes, with one each due to hypertrophic cardiomyopathy, nonischemic cardiomyopathy, and ischemic heart disease. For two, the etiology was unknown. The three OHCAs with a noncardiac cause involved two intracerebral hemorrhages and one splenic artery aneurysm. Of the five women who underwent autopsy, one tested positive for cannabis. The others showed no signs of illicit drug use.

The fact that none of the women with OHCA had been to a cardio-obstetrics clinic may be a sign that the specialty’s approach is working, Paratz suggested. “Although the numbers are small, maybe that speaks to the success of women who are linked in with multidisciplinary teams. They are not cardiac arrests. They’re being really well counselled and managed. It’s the ones who don’t know they have a problem who we saw in our data set.”

Paratz said that, as a result of their research, the ambulance service in Victoria will now routinely be collecting pregnancy status. Hopefully with an increase in knowledge it will be possible to implement primary prevention strategies, she noted. Their group is now planning to look back over a 20-year time span to get an even more comprehensive view of pregnancy-associated OHCA.