Artificial heart valve in pregnancy

Preconceptual evaluation

(A)cardiac function should be assessed-Clinical/Echo/Exercise testing
moderately or severely symptomatic (class III and IV) should be advised against pregnancy

(B)Fetal risks-abortion/prematurity/intrauterine growth restriction/congenital abnormalities-due to warfarin/inheritance in patient's with congenital heart disease


Inheritance of congenital heart disease


(C)Anticoagulation should be discussed-if anticoagulation is altered there is an increased risk thromboembolism. If thromboembolism occurs during pregnancy the risk to the fetus increased again.

(D) management planned by multi disciplinary team(Obstetrician/cardiologist/Cardiothoracic surgeon)


2 major types of valves



1.mechanical- Suggested INR is 3-4.Failure to anticoagulate could result in valve thrombosis and stroke.Subcutaneus heparin anticoagulation may inadequate in patients with artifial valves.
three categories : caged-ball tilting-disc bileaflet valves


2.bioprosthetic or homograft-
three categories heterografts homografts autografts.

They don't require anticoagulation but shorter lives than mechanical valve.Patients may need anticoagulation if they develop Atrial fibrillation.

Opinion varies as to whether pregnancy accelerate homograft valve deterioration.

Fetal risks of Warfarin
1.Miscarriage
2.Teratogenesis
Chodroysplasia punctata
Optic atropy
Microcephaly

Factors determining the choice of anticoagulation
1.Site of valve replacement(mitral more thrombogenic aortic)

2.Type of valve ( ball & cage more thrombogenic than bileaflet valves)

3.Past history of thromboembolic events

4.No of mechanical valves

5.patient choice



Anticoagulation regimens-3 broad possibilities

1.Warfarin throughout the pregnancy
2.Heparin & warfarin alternatively Heparin between 6-12 weeks & after 36 weeks
3.Heparin throughout the pregnancy

Aspirin is a useful adjunct when heparin is used.


If LMWH is used anti Xa levels should be monitored 4-6 hrs post injection.LMWH doesn't cross placenta

Advantages of LMWH

1.fewer bleeding complications
2.lower frequency of thrombocytopenia
3.lower incidence of osteoporosis
4.longer half life
5.more predictable dose response




The following is the commonly used regime


Conception is difficult to time & risk of congenital malformation is likely to be minimal in the first 4 weeks, so patient could conceive on warfarin.

Then patients are given intravenous heparin aiming to double APTT during 6-12 weeks.


Patient can be converted to warfarin from 12 weeks.

At 37 weeks patient us converted to continuous intravenous heparin.


If patients goes into labour while on warfarin vitamin K & FFP should be given & heparin should be commenced.
Heparin & LMWH can be reversed with protamine sulphate.

Postpartum patient continues on heparin for 3-7 days.Patient can breast feed while in heparin or warfarin.


Patients on dindevan shouldn't breast feed.



Antibiotic prophylaxis is indicated in patient with artificial valve.
Current recommendations amoxicillin 2g i.v & gentamicin 1.5 mg/kg i.v


Heart failure in pregnancy

medicine that can be used:digoxin, diuretics, nitrates, hydralazine, and
beta blockers.

medicine that should be avoided:angiotensin-converting enzyme
inhibitors and angiotensin receptor antagonist amiodarone sodium metroprusside


Valve thrombosis in pregnancy

Thrombolysis is the first line approach
Surgery is reserved for patients in thrombolysis is contraindicated.

References
1. Nelson-Piercy C. Handbook of obstetric medicine. Taylor & Francis; 2002.


2. Swiet MD. Medical disorders in obstetric practice. Wiley-Blackwell; 2002.


3. Elkayam U, Bitar F. Valvular Heart Disease and Pregnancy: Part II: Prosthetic Valves. J Am Coll Cardiol. 2005 Aug 2;46(3):403-410.



4.The Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy