Cardiac disease in pregnancy

Associate Editor-In-Chief:

Definitions

 * Heart failure within last month of pregnancy or five months postpartum
 * Absence of prior heart disease
 * No determinable cause
 * Strict echocardiographic indication of left ventricular dysfunction:
 * Ejection fraction <45% and/or
 * Fractional shortening <30%
 * End-diastolic dimension >2.7 cm/m2 BSA (body surface area)

Epidemiology and Demographics

 * Cardiovascular disease complicates 1- 4% of all pregnancies
 * Together with DVT/PE has surpassed hemorrhage, infection, and hypertensive disorders as leading cause of maternal mortality (20-30%)
 * Increasing numbers of women with congenital heart disease are now reaching childbearing age

Physiology of Labor and Delivery

 * 1) Hemodynamics are altered substantially during labor and delivery secondary to anxiety, pain, and uterine contractions.  Oxygen consumption increases threefold, and cardiac output rises progressively during labor owing to increases in both stroke volume and heart rate.  Blood pressure is higher in the lateral position.  Both the systolic and diastolic blood pressure increase markedly during contractions with a greater augmentation during the second stage.  The form of anesthesia impacts the blood pressure.
 * 2) By the time of delivery the Cardiac output (CO) has increased by 50%, the plasma volume has increased by 40% and the red cell mass has increased by 25 to 30%.
 * 3) The work of labor may increase the CO by 60% over the baseline level.
 * 4) During the second stage of labor the patient is on her back there is venous stasis, heart rate increases to > 120/min and the BP may be > 150 mm Hg.
 * 5) Immediately following delivery, the uterus contracts and delivers a sudden bolus of 500-750 cc of blood to the circulatory system which may result in pulmonary edema in the patient with heart disease.

Hemodynamic effect of cesarean section:
To avoid the hemodynamic changes assocaited with vaginal delivery, cesarean section is frequently recommended for women with cardiovascular disease. This form of delivery can also be associated with hemodynamic fluctuations related to intubation, analgesic as well as anesthetic use. There can be a greater extent of blood loss as well as relief of caval compression.

Hemodynamic changes postpartum:
There can be a temporary increase in venous return immediately after delivery due to relief of caval compression in addition to blood shifting from the contracting uterus into the systemic circulation. This change and effective blood volume occurs despite blood loss during delivery and can result in a substantial rise in ventricular filling pressures, stroke volume, and CO that may lead to clinical deterioration.

Both heart rate and CO returned to prelabor values by one hour after delivery and the blood pressure and stroke volume at 24 hours after delivery.

Hemodynamic adaptation of pregnancy persists postpartum and gradually returns to prepregnancy values within 12-24 weeks after delivery.

Effect of Pregnancy on Maternal Physiology

 * 1) Corpus Luteum Produces Progesterone
 * 2) * increased progesterone -> decreased smooth muscle tone -> therefore decreased SVR
 * 3) * later in pregnancy the placenta produces progesterone
 * 4) Increased Estrogen Levels
 * 5) * may increase contractility of heart
 * 6) Increased Renin and Aldosterone Levels Caused by Increased Estrogen
 * 7) * enhances Na and water retention
 * 8) * compensates for the decreased SVR
 * 9) * by the middle trimester, plasma volume is increased by 40 to 45%.
 * 10) * hemodilution -> anemia, but total red cell mass is not decreased. Rate of rise in volume is more rapid than rate of rise in red cell mass. This occurs until week 30 and is referred to as the physiologic anemia of pregnancy. The hematocrit can be as low as 33% to 38%.
 * 11) * starts as early as 6 weeks
 * 12) * greater increase in blood volume among multigravidas
 * 13) Cardiac Output Increases by 50%
 * 14) * have a higher volume of more dilute blood to circulate
 * 15) * need well oxygenated blood to circulate to the fetus
 * 16) * begins to rise at 5th week, and cardiac output increases until week 24 at which time it plateaus
 * 17) * resting pulse rate increases by 10 to 15 beats per minute. Pregnancy with multiple fetuses is associated with even more rapid heart rates.
 * 18) * BP remains relatively unchanged when measured in the left lateral recumbent position
 * 19) * hemodynamics measured in the supine position are erroneous because the uterus compresses the IVC decreasing the return from the lower extremities. Therefore may have syncope when a gravid stands up from a supine position.
 * 20) * keep in mind that much of the blood is shunted to the placenta where it may pass from arterioles to venules bypassing the capillaries. May precipitate high cardiac output failure in some women.
 * 21) * cardiac output increases in the lateral position and declines in the supine position owing to caval compression by the gravid uterus.
 * 22) * the increase in CO in early pregnancy is due to an increase in stroke volume early on, but in the third trimester it is due to an increase in heart rate.
 * 23) Increased Respiratory Rate
 * 24) * secondary to increased abdominal pressure, elevation of the diaphragm
 * 25) * lowers carbon dioxide tension
 * 26) Blood Pressure
 * 27) * arterial pressure begins to fall during the first trimester reaches a nadir in mid pregnancy and returns toward pregestational levels before term.
 * 28) * because diastolic blood pressure decreases substantially more than systolic blood pressure, the pulse pressure widens.
 * 29) * reduction blood pressure is caused by a decline in systemic vascular resistance due to reduce vascular tone. This is mediated by gestational hormone activity, increased circulate levels of prostaglandins and atrial natriuretic peptides, as well as endothelial nitric oxide. Increased heat production by the developing fetus small and the creation of a lower resistance circulation in the uterus also play a role.
 * 30) * supine hypotensive syndrome of pregnancy: occurs in 11% of women. Associated with weakness, lightheadedness, nausea, dizziness and even syncope.  This is often explained by acute occlusion of the inferior vena cava by the enlarged uterus.  Symptoms usually subside when the supine position is abandoned.
 * 31) Gastrointestinal changes
 * 32) * Gastric emptying is slower – in pregnancy women have reduced gastrointestinal motility.
 * 33) * An incompetent gastro-oesophageal sphincter leads to gastro-oesophageal reflux with greater danger of aspiration of gastric contents into the trachea.
 * 34) * Increased intragastric pressure in late pregnancy
 * 35) Other changes in pregnancy
 * 36) * Flared ribs
 * 37) * Breast hypertropy (may impede effective resuscitation)

Fetal Physiology

 * 1) Uterine blood flow increases by a factor of 50 during pregnancy
 * 2) The uterine blood vessels remain dilated throughout pregnancy
 * 3) Transfer of O2 across the placenta is flow-limited.
 * 4) Fetal O2 tension is normally quite low (30 to 40 mmHg)
 * 5) Supplemental O2 to the mother is quite effective in increasing fetal O2, particularly with fetal distress.
 * 6) Normal fetal pH is 7.35. Fetal scalp pHs< 7.25 are abnormal.
 * 7) Labor can precipitate fetal distress because during uterine contractions, uterine blood flow is nearly occluded.
 * 8) In a mother with cyanosis, it is easier for problems to arise during labor because of the reduced reserve in O2 delivery.
 * 9) With contractions, there may normally be a reduction or deceleration in the fetal heart rate, but this rapidly returns to normal.
 * 10) In fetal distress, the decelerations are later in the contraction and persist, i.e. late decelerations.
 * 11) Fetuses do not die suddenly during labor, and there are many minutes or hours of fetal distress before death so that there is time to intervene.
 * 12) Placing the mother in the left lateral recumbent position and O2 will relieve many cases of fetal distress.
 * 13) Fetal monitoring should be used in the presence of maternal heart disease, cardiac surgery, cardioversion.

History and Symptoms
Often accompanied by symptoms of fatigue, decreased exercise capacity, hyperventilation, dyspnea, palpitations, lightheadedness, and even syncope. Leg edema is often observed late in pregnancy and can lead to an erroneous diagnosis of heart failure. The arterial pulsese are full and collapsing and are similar to those palpated in patiends with aortic insufficiency or hyperthyroidism.

Physical Examination

 * 1) Increased first heart sound
 * 2) Persistent split S2
 * 3) Third heart sound is uncommon
 * 4) Pulmonic midsystolic murmur
 * 5) Continuous murmur (mammary soufflé, cervical hum)
 * 6) Varicosities and ankle edema
 * 7) In general there are often innocent murmurs of pregnancy.  These are the result of a hyperkinetic circulation.  These murmurs are usually midsystolic and soft and heard best at the left lower sternal border and over the pulmonic area.

Electrocardiogram

 * The QRS axis may shift either to the left or the right, but usually lies within normal limits.

Chest X Ray

 * The pelvic area should be shielded if a chest x-ray is done. The heart may seem enlarged due to elevation of the diaphragm and this should be interpreted with caution.

MRI and CT

 * MRI: There are no known safety hazards but the experience with the technique is limited. Currently the FDA recommends prudence in using MRI during pregnancy.

Echocardiography or Ultrasound

 * Echo: There is a progressive increase in chamber dimension with approximately a 20% increase in the size of the right atrium and the right ventricle, a 12% increase in left atrial size, and a 6% increase in left ventricular size. Postpartum, the changes gradually returned to baseline. In addition, there is early and progressive dilation of the mitral, tricuspid, and pulmonary annuli which is associated with an increase in valvular regurgitation.


 * Fetal Echo:
 * 1) Risk factors for structural heart disease (i.e. who to ECHO):
 * 2) * women with a history of congenital heart disease themselves or in previous children
 * 3) * diabetes and collagen vascular disease predispose to congenital heart disease
 * 4) * a history of a fetal arrhythmia
 * 5) * consumption of teratogens
 * 6) Fetal ECHO
 * 7) * one study found a sensitivity of 96% in detecting major structural malformations (72/74 abnormalities identified among 1,022 fetuses)
 * 8) * useful for management during pregnancy, postpartum, and genetics counseling

Other Diagnostic Studies

 * Exercise stress testing: If this is done, there should be fetal monitoring.


 * Radiation: If the patient receives less than five rads, then they can be reassured a very likelihood of risk. If they received more than 15 rads, termination of the pregnancy is recommended. Routine chest x-ray is associated with radiation of 20 millirads to the chest. Standard fluoroscopy delivers 1-2 rads per minute. Cineangiography delivers 5-10 rads per minute. Only 5% of the radiation delivered is absorbed by the fetus. A lead apron should be used over the mother's pelvis. With the use of nuclear medicine procedures the radiopharmaceuticals collect in the bladder when the placenta is directly across from the fetus. The expected radiation with thallium-201 or Tc imaging is less than one rad per examination.


 * Pulmonary artery catheterization: Hemodynamic monitoring can be of great help in managing high-risk patients during pregnancy, labor, delivery, and the postpartum period. The pulmonary artery line should be placed without fluoroscopic guidance. Insertion is recommended throughout labor and delivery for any patient with symptomatic cardiac disease during pregnancy or with the potential for deterioration due to valvular, myocardial, or ischemic heart disease. Hemodynamic monitoring should be continued for at least several hours after delivery to ensure stability.


 * Cardiac catheterization: May be indicated in rare instances of cardiac decompensation. To minimize radion to the pelvic and abdominal areas, the brachial, rather than the femoral approach is preferred.

Pharmacotherapy
Antibiotic prophylaxis: The official American Heart Association (AHA) recommendation is that antibody prophylaxis is not necessary for an uncomplicated delivery except among patients with a prosthetic heart valve or surgically constructed systemic to pulmonary shunt. However, because of the difficulties in predicting complicated deliveries and the potential devastating consequences of endocarditis, antibiotic prophylaxis for vaginal delivery in all patients with congenital heart disease expect those with an isolated secundum type atrial septal defect and those six months or more after repair of septal defects or surgical ligation division of a patent duct is arteriosus, seems reasonable. At the time of delivery it is recommended that all women with valvular disease receive antibiotics, usually penicillin (PCN) and gentamycin. For those with a PCN allergy, vancomycin is used.

Aortic Stenosis

 * Most commonly bicuspid valve
 * Fixed cardiac output in response to stress
 * Patients with mild to moderate severity do very well
 * Severe cases have maternal mortality up to 17% and fetal mortality up to 32%
 * Critical cases need surgery / valvuloplasty
 * Any reduction in preload can lead to cardiac / cerebral ischemia and compromised uterine flow

Overview

 * Rapidly becoming most common cardiac problem among pregnant patients
 * Improved diagnostic techniques
 * Availability of corrective surgery
 * Children of affected mothers at increased risk of having similar lesions
 * Outcomes clearly linked to functional status pre-pregnancy

Classification of disease
Can classify lesions into 3 classes:

Volume Overload (L-->R shunt)

 * ASD, VSD, and PDA well tolerated if pulmonary hypertension not present
 * PVR and SVR falls to same degree
 * Degree of shunting does not change
 * Eisenmenger’s Syndrome
 * Maternal and fetal mortality ≥50%
 * Consider termination if detected early
 * Careful medical management
 * -Supplemental O2 during pregnancy
 * -Hospitalization at 20 weeks gestation
 * -Prompt treatment of CHF
 * -Avoid shifts in preload/afterload

Pressure Overload

 * AS, MS
 * Pulmonic Stenosis
 * Degree of obstruction determines outcome
 * Gradient >80 mm Hg mandates correction
 * Coarctation of the aorta
 * Accounts for 9% of all congenital disease in adults
 * Class I or II patients usually do well
 * Overall 3.5% mortality in unoperated patients (aortic dissection/rupture, CVA, CHF, endocarditis)
 * HTN needs careful management
 * HOCM
 * Early to mid pregnancy,  C.O. and end-diastolic dimension ↓ outflow tract obstruction (counteracted by SVR)
 * Avoid Valsalva
 * Encourage left lateral decubitus position


 * Maximum risk period during delivery when blood loss can result in increased gradient + systemic hypotension
 * Keep well hydrated
 * Avoid digoxin, simpathomimetics and excessive diuretics

Cyanotic Heart Disease (R-->L shunt)

 * Poor prognosticators:
 * Hematocrit > 60%
 * O2 sat<85%
 * Livebirth 12% vs. 92% is sat >90%


 * Systemic RV pressures
 * h/o recurrent syncope
 * Tetralogy of Fallot most common unrepaired defect
 * Drop in SVR leads to increased shunting, deeper cyanosis and rising HCT
 * Need to avoid Valsava during delivery
 * Maternal mortality more than 4%

Marfan's Syndrome

 * Autosomal dominant inheritance pattern (counseling is essential)
 * Major risk is aortic dissection
 * Most common in 3rd trimester or 1st stage of labor
 * Increases with enlarging aortic root diameter
 * Surgery recommended pre-conception if root diameter >40 mm
 * Surgery recommend during gestation if > 55 mm
 * Prophylactic Beta-blockers appear to be helpful


 * Close follow-up with serial echo

Mitral Stenosis
Overview


 * Most hemodynamically important valvular problem during pregnancy
 * Physiologic changes result in increased pulse and C.O. with augmentation of diastolic gradient
 * Atrial fibrillation can lead to rapid deterioration
 * Volume shifts during delivery can result in pulmonary hypertension or pulmonary edema

Management of MS in Pregnancy


 * Restriction of physical activity and salt intake. Avoid supine position
 * Beta-blockade to lengthen disatolic filling period
 * Diuretics if necessary (gentle)
 * Consideration of invasive monitoring
 * Replace blood losses during delivery carefully
 * Percutaneous Balloon Mitral Valvuloplasty can be performed during pregnancy if necessary (Class III,IV)

Overview

 * First reported case in 1922
 * Incidence ~1/10000
 * Ages range 16-45
 * Most common in 3rd trimester women > 33 years of age
 * Anterior wall most commonly involved
 * Maternal mortality 21% (most at time of MI or within 2 weeks- usually with labor and delivery)
 * Outcomes better if MI early in pregnancy
 * Fetal deaths usually associated with maternal deaths
 * Risk factors:
 * FH of CAD
 * Hyperlipidemia
 * Low HDL
 * High LDL
 * Smoking
 * Previous OCP use

Pathophysiology

 * Caths 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)

Diagnosis

 * EKG and enzymes are the gold standard
 * 37% of patients undergoing elective C-section have EKG changes suggestive of MI or ischemia
 * Echo to assess regional wall motion abnormalities can be useful
 * Nuclear imaging and diagnostic cath exposure to conceptus <0.01 Gy (0.05 Gy considered to be threshold value)

Drugs
Check with pharmacist or Maternal Fetal Medicine Specialist before any drug administration


 * ASA - low dose
 * Nitrates – use low dose to prevent fetal distress
 * Beta-1 selective Beta-blockers
 * Magnesium
 * Morphine sulfate
 * 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

Diagnostic criteria (Demakis et al, 1971)

 * Development of CHF/LV dysfunction in last month of pregnancy to 5 months postpartum
 * Absence of determinable cause
 * Absence of demonstrable cardiac disease before last month of pregnancy

Common Mimickers

 * Accelerated HTN
 * Infection/sepsis
 * Diastolic dysfunction
 * High output state of pregnancy

Demographics

 * Estimates of incidence 1/1300-15000
 * Previous studies likely overestimated
 * More common in women with:
 * Multiple pregnancies
 * African decent
 * h/o toxemia
 * Long-term tocolytic use
 * Age>30
 * Twin Pregnancy


 * Etiology remains unknown
 * Signs and sxs similar to those of nl pregnancy

Treatment of Peripartum CMP

 * Digoxin and diuretics are Class C
 * ACE inhibitors absolutely contraindicated prepartum (hydralazine drug of choice)
 * Anticoagulation recommended (Heparin prepartum and coumadin postpartum)

Outcome of Peripartum CMP

 * Mortality 25-50% (half deaths in first 3 months)
 * Remainder stable/recover within 6 months
 * Can recur with subsequent pregnancies
 * Favorable outcomes with cardiac transplantation

Managing Prosthetic Valves During Pregnancy

 * Pregnancy is a thrombogenic milieu
 * Coumadin use during 1st trimester associated with warfarin embryopathy
 * Coumadin use in other trimesters postulated to cause CNS abnormalities
 * Keeping Coumadin dose ≤ 5.0 mg/day appears safe
 * Recommendations based more on opinion than scientific evidence
 * SBE Prophylaxis at Delivery

Use of antithrombotic agents during pregnancy: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

 * In women with prosthetic heart valves, the guideline developers recommend:


 * 1) Adjusted-dose, twice-daily LMWH throughout pregnancy in doses adjusted either to keep a 4-hour postinjection anti-Xa heparin level at approximately 1.0 to 1.2 U/mL (preferable) or according to weight (Grade 1C), or
 * 2) Aggressive adjusted-dose UFH throughout pregnancy: i.e., administered SC every 12 hours in doses adjusted to keep the mid-interval aPTT at least twice control or to attain an anti-Xa heparin level of 0.35 to 0.70 U/mL (Grade 1C), or
 * 3) UFH or LMWH (as above) until the thirteenth week, change to warfarin until the middle of the third trimester, and then restart UFH or LMWH (Grade 1C).
 * Remark: Long-term anticoagulants should be resumed postpartum with all regimens


 * 1) In women with prosthetic heart valves at high risk, the guideline developers suggest the addition of low-dose aspirin, 75 to 162 mg/day (Grade 2C).

Regurgitant Valvular Lesions During Pregnancy

 * Usually tolerated very well during pregnancy
 * Severity may decrease during pregnancy due to drop in SVR
 * Vasodilators only if systemic HTN (avoid ACE-inhibitors)
 * Antibiotic prophylaxis important if infection suspected

Rheumatic Cardiac Disease in Pregnancy

 * Previously accounted for over 90% of CV disease during pregnancy
 * Recent studies show congenital disease now more common
 * Royal Infirmary at Edinburgh University: 94% (1928-47), 36% (68-77), 24% (73-77)
 * Remains common in less developed nations

Pulmonary Hypertension in Pregnancy

 * High maternal / perinatal mortality (~50%)
 * Vaginal delivery with limited anesthetics are preferred.

Resuscitation in Late Pregnancy
Cardiac arrest occurs in approximately one in 30,000 women in late pregnancy. Maternal mortality is caused by venous thromboembolism, severe preeclampsia or eclampsia, sepsis, amniotic fluid embolism, haemorrhage, trauma, iatrogenic causes including anaesthesia and drug errors or allergy, and congenital or acquired heart disease.

Consideration of urgent hysterotomy or Caesarean section should be made for the pregnant woman who has a cardiac arrest. If early resuscitation fails, birth of the fetus may improve maternal and fetal chance of survival. Infants over 24-25 weeks gestation have the best chance of survival if birthed within 5 minutes of maternal cardiac arrest. It is recommended that hysterotomy or Caesarean section be commenced 4 minutes after a cardiac arrest unless there has been a successful resuscitation and maternal perfusion restored within that time.

Obesity exaggerates the risks and physical changes in pregnant women.

Position of the pregnant women

 * Position the women on her back with the shoulders flat. Place padding/wedge under the right buttock to give an obvious pelvic tilt to the left.
 * The thighs of a rescuer may be used for resting the women on, and providing a lateral tilt.
 * An assistant may move the uterus further off the vena cava by lifting the uterus with two hands to the left and towards the woman’s head.

Airway management

 * The woman should be inclined laterally for suction, removing ill-fitting dentures or foreign bodies, and inserting airways.
 * Mouth to mouth or bag and mask ventilation is done with a pillow; the head and neck are fully extended.
 * Apply cricoid pressure until the airway is protected by a cuffed tracheal tube if sufficient staff are available to do this – this decreases risk of gastric aspiration.
 * A soon as possible tracheal intubation should be inserted – ensures adequate ventilation with increased intra-abdominal pressure.
 * Consider using a smaller tracheal tube if the airway is narrowed due to oedema and swellling.
 * Positioning for intubation - using one pillow helps to flex the neck and extend the head.

Circulation management

 * Adhesive defibrillator pads attachment are used to assist contact which may be difficult due to the larger breasts in the pregnant woman.
 * Hand position higher than the normal position for chest compressions may be needed to adjust for the elevation of the diaphragm and abdominal contents due to the gravid uterus.
 * Raising the woman’s legs will assist venous return.

Gastrointestinal management
Early intubation decreases the risk of gastric aspiration.

Intiating caesarean section
Immediately a pregnant woman collapses and requires resuscitation a staff member should collect the Caesarean Section Perimortem pack.

Sources:

 * Australian Government Health Pages

Acknowledgements
The content on this page was first contributed by C. Michael Gibson M.S., M.D.