Pregnancy increases the risk of acute myocardial infarction (MI) three- to four-fold, according to a literature review published in the Journal of the American College of Cardiology for July 15.

Pregnancy increases the risk of acute myocardial infarction (MI) three- to four-fold, according to a literature review published in the Journal of the American College of Cardiology for July 15.

"It's extremely important that physicians who take care of women during pregnancy and after delivery be aware of the occasional occurrence of acute MI in pregnancy and not overlook symptoms in these young patients," Dr. Uri Elkayam said in a statement.

Dr. Elkayam, at the USC Keck School of Medicine in Los Angeles, and Dr. Arie Roth, at the Sackler School of Medicine in Tel Aviv, Israel, reviewed published data on 95 women with pregnancy-related acute MI, along with their records on eight of their own such patients.

MI occurred at all stages of pregnancy and during the three-month postpartum period, and was more frequent in multigravidas (66 per cent), and in women older than 30 years (72 per cent).

Maternal mortality was 11 per cent, and fetal mortality was nine per cent (six of 68 fetuses, including two pregnancies terminated for potential drug teratogenicity). Mortality was higher in the peripartum period.

In 28 patients, coronary dissection, normally a rare occurrence, was the cause of MI. "The physiologic increase in blood volume and cardiac output may magnify shear forces of the blood column in large vessels, resulting in a greater propensity for dissection," the authors speculate.

Coronary artery atherosclerosis was observed in 41 cases, and coronary thrombosis in eight. The authors suggest that increased myocardial oxygen demand during pregnancy coupled with anemia and decreased diastolic blood pressure may also lead to infarction.

The researchers caution that while the diagnostic approach is "generally the same as in nonpregnant patients," fetal safety and normal pregnancy-related changes must be taken into account, particularly during labor and delivery. For example, ST-segment depression has been seen after induction of anesthesia for cesarean section and may be misleading. Biochemical markers may be altered during normal labor and delivery.

If exercise testing is used during pregnancy, the authors recommend a submaximal protocol (no more than 70 per cent of maximal predicted heart rate) with fetal monitoring. Also, they say, radiation should be kept to a minimum, and pregnancy termination may be considered if radiation doses exceed ten rads.

If revascularization is considered, drug-eluting stents should be avoided. The authors consider primary percutaneous coronary intervention preferable to thrombolytic therapy.

Limited information is available regarding the safety during pregnancy and breastfeeding for many of the drugs commonly used to treat acute MI. In terms of risk to the fetus, none is considered to be risk-free.

Little information is available regarding antiplatelet agents, and the authors recommend that a cesarean be considered when antiplatelet effects are present at the time of delivery.

The risks of statin use in pregnant women clearly outweigh any possible benefit.

Only ten patients underwent cesarean sections, suggesting that "vaginal delivery can be accomplished relatively safely in the stable patient with pregnancy-associated acute MI when measures aimed to reduce cardiac workload and oxygen demands are taken." Such measures include instrumental vaginal delivery, positioning the patient in the left lateral position, treatment of pain and fear, and continuous vital sign monitoring.

"For prevention or treatment of myocardial ischemia during labor, intravenous nitroglycerin, beta-blockers, and calcium antagonists can be used," but nitroglycerin and calcium channel blockers may prolong labor, according to the paper.