Rare but Devastating: Study Examines Maternal Cardiac Arrest Rates

Rates and etiologies of maternal cardiac arrest in Canada are similar to those found in the United States, a study has concluded.

“This is the first Canadian study on maternal cardiac arrest,” said Leyla Baghirzada, MD, MPH, clinical assistant professor at the University of Calgary, in Alberta. She presented the study at the 2016 annual meeting of the Society for Obstetric Anesthesia and Perinatology.

Cardiac arrest during pregnancy is a rare but devastating event. The incidence of maternal cardiac arrest has been estimated at one in 20,000 to 50,000 cases in European studies, Dr. Baghirzada said. A recent evaluation of the U.S. Nationwide Inpatient Sample estimated cardiac arrest during pregnancy at one in 12,000 hospitalizations for delivery (Anesthesiology 2014;120:810-818). Until now, no studies have shed light on these rates in Canada.

Large Database

To fill the knowledge gap, Dr. Baghirzada and her colleagues conducted a retrospective, population-based cohort study that included all pregnant women in Canada hospitalized between April 1, 2002, and March 31, 2015. The study excluded early pregnancy with abortive outcomes and ectopic and molar pregnancy. Maternal cardiac arrest after 20 or more weeks of gestation was identified through International Classification of Diseases, 10th Revision codes and the Canadian Classification of Health Interventions.

Among the roughly 3.5 million hospitalizations for delivery (3,568,597), there were 286 cases of cardiac arrest. Of these, 71% survived the event and 29% died. Neonatal data were obtained for 94% of deliveries. Looking at neonatal data on 268 neonates of women who had cardiac arrest, 86% survived, 10% were stillborn and 4% died.

The incidence of maternal cardiac arrest varied between four and 10 cases per 100,000 deliveries, with an overall incidence of eight per 100,000 deliveries. The researchers did not detect any significant variation in rates between 2002 and 2015. Women who suffered from cardiac arrest were more likely to have gestational hypertension or gestational diabetes (Table).

Table. Medical Conditions Associated With Cardiac Arrest

Condition        Odds Ratio

Gestational hypertension        2.0

Gestational diabetes   2.0

Diseases of the nervous system          3.8

Diseases of the respiratory system     1.8

Heart failure   23

Obstetric embolism    17.3

Complications from anesthesia          9.4

Sepsis  3.6

Eclampsia       13.6

“The most common etiologies were postpartum hemorrhage, heart failure and obstetric embolism,” Dr. Baghirzada said. “Postpartum hemorrhage was associated with half of the cases. Heart failure, obstetric embolism, and complications from anesthesia, sepsis and eclampsia contributed to another half.”

She noted there was a significant increase over time of the incidence of postpartum hemorrhage, gestational hypertension, gestational diabetes, heart failure and obesity, which confirms previous observations that the obstetric population is becoming more and more complex. “It is reassuring to note that the incidence of cardiac arrest did not increase over time, despite an increase in associated conditions,” Dr. Baghirzada said.

Eclampsia, pulmonary edema, heart failure, antepartum and postpartum hemorrhage, obstetric embolism, sepsis, trauma and anesthesia-related complications were associated with a maternal survival rate of roughly 50%, whereas acute myocardial infarction and aortic aneurism had survival rates of less than 35%. There was no temporal or provincial difference in the incidence of survival.

The study was limited by factors inherent in large hospitalization studies, including the reliance on inpatient data, the possibility of miscoding, missing neonatal data (in 6% of cases), and the inability to determine the temporal relation between cardiac arrest and delivery.

“Our findings could contribute to guiding content development and delivery of future regular simulation drills in hospitals across Canada carin g for pregnant patients, so that patient safety can be improved further,” Dr. Baghirzada said. “Focusing on the effective treatment of the predisposing conditions identified in this review can help prevent the incidence of this dreadful complication.”

David Chestnut, MD, chief of the Division of Obstetric Anesthesiology at Vanderbilt University Medical Center, in Nashville, Tenn., who moderated the session, said the data were strikingly similar in terms of incidence, survival and etiologies to a study from the United States (Anesthesiology 2014;120:810-818) that found that approximately one in 12,000 hospitalizations for delivery is complicated by cardiac arrest, most frequently due to hemorrhage, heart failure, amniotic fluid embolism or sepsis.