Cardiac disease in pregnancy and acute myocardial infarction

Overview
In general, women of childbearing age are at relatively low risk for coronary artery disease. While rare, the risk of acute myocardial infarction (AMI) is 3-4 times higher during pregnancy, and negative fetal and maternal outcomes are associated with this condition.

Historical Perspective

 * First reported case in 1922

Epidemiology and Demographics

 * Incidence ~1/10000
 * Ages range 16-45
 * Maternal mortality rate is 11% (most at time of MI or within 2 weeks- usually with labor and delivery) and a fetal mortality rate is 9%.

Cause
Cardiac catheterization in 54% of published cases:
 * CAD with or without thrombus 43% (58% in prepartum period)
 * Thrombus without CAD 21%
 * Normal coronaries 29% (75% in peripartum period MIs)
 * Coronary dissection 16% (33% in postpartum period)

Pathophysiology
Acute myocardial infarction can occur at all stages of pregnancy, and is more common in multi-gravid patients.

The etiology of coronary dissection in pregnant patents is thought to be related to an excess of progesterone, which causes changes in the vessel wall, including loss of normal corrugation elastin fibers, fragmentation of reticular fibers, and decreases in the amount of acid mucopolysaccharides. The increase in blood volume and cardiac output that occurs with pregnancy magnifies shear forces of the blood column in large vessels, which in combination with the vessel wall changes leaves these patients predisposed to coronary dissection.

In a review performed in 2008, myocardial infarction (MI) location was mostly (78%) in the anterior wall and involved the left anterior descending artery; the most common cause was coronary artery dissection.

Risk Factors

 * Family history of coronary artery disease
 * Hyperlipidemia
 * Low HDL
 * High LDL
 * Smoking
 * Previous oral contraceptive use

Diagnosis
The following should be considered in diagnosis and treatment of this condition:
 * Criteria for diagnosis of AMI in pregnant women are in general the same as in non pregnant patients (symptoms, exam, ECG, biomarkers, +/- imaging/angiography). 37% of patients undergoing elective C-section have EKG changes suggestive of MI or ischemia. Echocardiography to assess regional wall motion abnormalities can be useful.


 * Note that creatine kinase and its MB fraction can increase nearly 2-fold within 30 minutes after delivery, as can troponin levels.


 * If exercise stress testing is indicated, a submaximal protocol (<70% of maximal predicted heart rate) with fetal monitoring is preferred.


 * Radionuclide imaging using 99m technetium-labeled sestamibi or 201 thallium, as well as cardiac catheterization or interventional procedure, are expected to yield<11 rad of radiation to the conceptus, which is generally considered safe; termination of pregnancy is generally recommended at a level of 10 rads.

Pharmacotherapy
The treatment of pregnant women with AMI and its complications should follow the usual standard of care; a cardiologist should work in tandem with an obstetrician in order to tailor therapy to both the mother and the fetus

Common drugs used in patients with CAD and their Pregnancy Categories

 * Morphine Sulfate (Risk Category C)
 * Organic Nitrates (Risk Category B: Nitroglycerin; Risk Category C: Isosorbide dinitrate)
 * Beta-Adrenergic Blocking Agents ''(Risk Category B: Metoprolol; Risk Category C: Atenolol)
 * Calcium Channel Blockers (CCBs) (Risk Category C: Nifedipine, Diltiazem, Verapamil)


 * Angiotensin Converting Enzyme Inhibitors and Angiotensin Receptor Antagonists (Risk Category C) teratogenic


 * Eplerenone (Risk Category B)


 * HMG-CoA Reductase Inhibitors (Statins) (Risk Category X)


 * Unfractionated (UFH) and Low Molecular Weight Heparin (LMWH) (Risk Category B: LMWH; Risk Category C: UFH)


 * Aspirin (Risk Category C)


 * Thienopyridine derivatives (Risk Category B)


 * Glycoprotein IIb/IIIa inhibitors (Risk Category B: eptifibatide, tirofiban; Risk Category C: abciximab)

Drugs to be Avoided

 * Avoid ACE inhibitors and warfarin due to teratogenicity
 * Thrombolytics mostly untested
 * Greatest experience in massive pulmonary embolism
 * Streptokinase does not cross placental membrane in animals, but Ab found in neonatal spinal cord fluid
 * Urokinase not teratogenic in mice/rats
 * Risk for maternal hemorrhage (1 case of placental abruption reported); increased risk when given at time of delivery
 * Delivery best delayed at least 2-3 weeks

Prognosis

 * Outcomes better if MI early in pregnancy

Related Chapter
For a more broad discussion on coronary artery disease, please click here.