Nationwide Data Shed Light on Timing, Predictors of Acute MI in Pregnancy

Acute MI in the context of pregnancy, either during or after, is associated with a spate of modifiable and nonmodifiable risk factors, nationwide US data confirm. Better understanding of these characteristics may aid in both prevention and treatment, researchers say.

This is especially true because acute MI in this setting is so rare—just 0.008% over more than a decade’s worth of pregnancies—so these events may be underrecognized, senior author Kathleen Stergiopoulos, MD, PhD (St. Francis Hospital, The Heart Center, Roslyn, NY), told TCTMD. Still, she pointed out, they are becoming ever more common and can have devastating consequences, with an in-hospital mortality rate of 4.5%.

While pregnancy as a cardiovascular “stress test” isn’t a new concept, what’s been less fleshed out are the predictors and timing of acute MI, said Stergiopoulos. Awareness of these complications among clinicians is still “relatively low,” she added. “There isn’t a lot of knowledge in general about this group of women. There isn’t a lot of literature.”

Physicians caring for women throughout pregnancy “often forget about the postpartum period, but that’s a period of high risk because of changes in the maternal cardiovascular system—it’s sort of like the forgotten trimester,” she said, adding that during this high-risk period “most patients have left the hospital by the time symptoms begin. With a new baby at home, the last place mothers want to be is back in the hospital” and, especially for a younger woman, a heart attack may not even be “on her radar.”

Cardio-obstetrics, an emerging specialty that involves multidisciplinary teams well versed in women’s CV needs during pregnancy, are becoming more common but tend to be located at academic medical centers, Stergiopoulos observed. As advised by an American Heart Association scientific statement, women with existing CVD or at high risk of developing it while pregnant should seek this level of coordinated care, she said.

The new results were published online recently in the Journal of the American Heart Association.

An ‘Interplay’

Led by Courtney A. Balgobin, MS (Stony Brook University Medical Center, NY), the researchers identified 913 instances of acute MI among more than 11 million recorded pregnancies in the National Inpatient Sample (NIS) between 2003 and 2015, over which time the rate rose from around 0.006% to 0.011%.

“Increases in AMI incidence have occurred in lockstep with increases in maternal age”—and its accompanying comorbidities—"as well as a global rise in obesity and metabolic syndrome,” the investigators say.

Nearly three-quarters of the women who experienced acute MI (72.4%) were aged 30 or older. One-third had CAD prior to their acute MI. Around in one in five had used tobacco, and 13% had a history of high cholesterol. Eclampsia/preeclampsia were present in 18.3% of women. Fully 44.9% were on public insurance (Medicaid or Medicare), and 55.2% were below the 50th median percentile for income. Compared with women who didn’t develop acute MI, those who did were more likely to be Black (23.4% vs 12.0%) and less likely to be white (38.4% vs 43.3%) or Hispanic (12.7% vs 18.8%).

Half of the acute MIs occurred postpartum (50.8%), while 37.0% happened during pregnancy and 12.2% during labor/delivery.

Most of the NIS records (59.4%) lacked information on what had caused the acute MI. For those with these details, 28.3% were attributed to coronary atherosclerosis of the native artery and 15.0% to coronary artery dissection. Far less common were chronic ischemic heart disease, chronic total occlusion, primary and secondary thrombophilia hypercoagulable state, arterial embolism, and thrombosis.

Sixty percent of the acute MIs were subendocardial. Only 51.6% of women were listed as having undergone revascularization.

With a new baby at home, the last place mothers want to be is back in the hospital. Kathleen Stergiopoulos

Known CAD was the strongest cardiac predictor of acute MI (OR 517.4; 95% CI 420.8-636.2), joined by heart failure (OR 8.2; 95% CI 1.9-35.2), prior valve replacement (OR 6.4; 95% CI 2.4-17.0), and atrial fibrillation (OR 2.7; 95% CI 1.5-4.7). Traditional risk factors for CVD, like hyperlipidemia, obesity, smoking history, substance abuse, and thrombophilia, also were associated with acute MI, as were eclampsia (OR 6.0; 95% CI 3.3-10.8) and preeclampsia (3.2; 95% CI 2.5-4.2). Obstetric risk factors included postpartum hemorrhage, placental abruption, uterine rupture, postpartum infections, and thrombotic events.

Major adverse cardiovascular and cerebrovascular events—spanning arterial embolism and thrombosis, acute renal failure, arrhythmia, bleeding/transfusion, cardiac arrest, cardiac complications of anesthesia or other sedation in labor and delivery, cardiogenic shock, heart failure, in-hospital death, obstetrical pulmonary embolism, postpartum hemorrhage, respiratory failure or arrest, stroke, atheroembolism, pulmonary embolism, and infarction—were observed in 60.9% of women with acute MI. Nearly two-thirds of these MACCE occurred in the postpartum period.

Women whose acute MIs developed in pregnancy or during labor/delivery were at higher risk of MACCE than those whose events were postpartum. Preeclampsia/eclampsia on the backdrop of hypertension increased MACCE risk. Other influential factors were prior PCI, fluid and electrolyte imbalance, and inferoposterior MI location.

Important to recognize, the investigators say, is that the “interplay of modifiable and nonmodifiable risk factors as well as obstetric issues, postpartum timing, and known cardiac disease can lead to adverse outcomes.” These nuances can be explored during prepregnancy counseling, they suggest, so that, when possible, women can take steps to reduce risk.