Heart disease in pregnancy: Risk stratification

Heart disease in pregnancy: Risk stratification


It is needless to say that heart disease in pregnancy is a challenge for the obstetrician and the cardiologist. Hemodynamic changes in pregnancy and labor can adversely affect many of the significant cardiac lesions. Increase in blood volume and heart rate are the important factors during pregnancy. In general stenotic lesions and pulmonary hypertension are poorly tolerated, while regurgitant lesions are better tolerated. Specific risks like aortic dissection and rupture are there for coarctation of aorta. Several risk stratification schemes have been developed for assessing the risk of pregnancy with heart disease over the years. This discussion covers mWHO, CARPREG (oldest – 2001), ZAHARA and CARPREG II (latest – May 2018) risk scores.

Modified World Health Organization (mWHO) classification [1]

Obstetric patients with heart disease are classified into:

Class I: Very low risk
Class II: Low to moderate risk
Class III: High risk
Class IV: Extremely high risk – pregnancy is contraindicated

Class I: Mild pulmonary stenosis, small patent ductus arteriosus and mitral valve prolapse. Successfully repaired simple lesions which include atrial and ventricular septal defects, patent ductus arteriosus and anomalous pulmonary venous drainage. Isolated atrial or ventricular ectopic beats.

 Class II: Unoperated atrial or ventricular septal defects, repaired tetralogy of Fallot and most arrhythmias. 

Mild left ventricular dysfunction, hypertrophic cardiomyopathy, Marfan syndrome without aortic dilatation, bicuspid aortic valve associated with aortic disease having aortic diameter less than 45 mm, native and tissue valvular disease which is not included in Class I or IV and repaired coarctation may be included in either Class II or III depending on individuals situations.

Class III: Mechanical heart valves, systemic right ventricle (as after atrial switch operation for transposition of great arteries), Fontan circulation, unrepaired cyanotic heart disease, other complex congenital heart diseases, Marfan syndrome with aortic diameter between 40-45 mm and bicuspid aortic valve with aortic dilatation in the range of 45-50 mm.

Class IV (Pregnancy contraindicated): Pulmonary arterial hypertension of any cause,  severe systemic ventricular dysfunction with left ventricular ejection fraction below 30%, New York Heart Association (NYHA) III–IV, previous peripartum cardiomyopathy with any residual left ventricular dysfunction, severe mitral stenosis and severe symptomatic aortic stenosis, Marfan syndrome with aortic dilatation more than 45 mm, aortic dilatation more than 50 mm associated with bicuspid aortic valve and severe native coarctation of aorta.

CARPREG risk score [2]

This risk score was published in Circulation in 2001 by the CARPREG investigators from Canada and actually predates the mWHO scoring system which came in Heart in 2006.

Four predictors of primary cardiac events were:

  1. Prior cardiac event: Heart failure, transient ischemic attack or stroke prior to pregnancy or arrhythmia.
  2. Baseline NYHA class above II or cyanosis.
  3. Left heart obstruction: Mitral valve area less than 2 sq cm, aortic valve area less than 1.5 sq cm or peak left ventricular outflow tract (LVOT) gradient more than 30 mm Hg by echocardiography.
  4. Reduced systemic ventricular systolic function with ejection fraction less than 40%.

ZAHARA risk predictors [3]

  1. History of arrhythmic event
  2. NYHA functional class above II
  3. Left heart obstruction with peak gradient above 50 mm Hg
  4. Mechanical prosthetic valve
  5. Moderate or severe systemic atrioventricular (AV) valve regurgitation possibly related to ventricular dysfunction
  6. Moderate or severe sub-pulmonary AV valve regurgitation possibly related to ventricular dysfunction
  7. Use of cardiac medication during pregnancy
  8. Repaired or unrepaired cyanotic heart disease

CARPREG II risk score, the latest in the series [4].

CARPREG II has been published in May 2018 in the Journal of American College of Cardiology. It improves upon their CARPREG scoring system and is based on nearly two thousand pregnancies with heart disease from two advanced centers in Canada. The score is based on ten predictors. Each predictor is assigned a weighted point score. The sum of points represents the risk score.

CARPREG II risk predictors and their points:

  1. Prior cardiac events or arrhythmias: 3
  2. Baseline NYHA class III-IV: 3
  3. Mechanical valve: 3
  4. Ventricular dysfunction: 2
  5. High risk left sided valve disease/LVOT obstruction: 2
  6. Pulmonary hypertension: 2
  7. Coronary artery disease: 2
  8. High risk aortopathy: 2
  9. No prior cardiac intervention: 1
  10. Late pregnancy assessment: 1

References

  1. Thorne S, MacGregor A, Nelson-Piercy C. Risks of contraception and pregnancy in heart disease. Heart. 2006 Oct;92(10):1520-5.
  2. Siu SC, Sermer M, Colman JM, Alvarez AN, Mercier LA, Morton BC, Kells CM, Bergin ML, Kiess MC, Marcotte F, Taylor DA, Gordon EP, Spears JC, Tam JW, Amankwah KS, Smallhorn JF, Farine D, Sorensen S; Cardiac Disease in Pregnancy (CARPREG) Investigators. Prospective multicenter study of pregnancy outcomes in women with heart disease. Circulation. 2001 Jul 31;104(5):515-21.
  3. Drenthen W, Boersma E, Balci A, Moons P, Roos-Hesselink JW, Mulder BJ, Vliegen HW, van Dijk AP, Voors AA, Yap SC, van Veldhuisen DJ, Pieper PG; ZAHARA Investigators. Predictors of pregnancy complications in women with congenital heart disease. Eur Heart J. 2010 Sep;31(17):2124-32.
  4. Silversides CK, Grewal J, Mason J, Sermer M, Kiess M, Rychel V, Wald RM, Colman JM, Siu SC. Pregnancy Outcomes in Women With Heart Disease. The CARPREG II Study. J Am Coll Cardiol. 2018;71(21):2419-30.