The correct answer is: A. No, but slight increases throughout the pregnancy within the normal range (0-100 pg/ml) can be seen normally.

A rise within the normal range of values can occur in normal pregnancies.

B: A BNP > 100 pg/ml can be linked to decompensated heart failure in pregnancy.

C: There are hemodynamic stresses associated with pregnancy; however a normal heart can accommodate these demands without excessive stretch on the myocardium. An increase within the normal BNP range can occur in normal pregnancy; however an elevation above this range should prompt further evaluation.

An echocardiogram was ultimately performed on our patient which showed a mildly dilated left ventricle (LVIDd: 5.85 cm, Normal range: 3.5-5.6) with moderately depressed LV systolic function. LVEF 30-35%. Mild global hypokinesis with apical akinesis. Mild mitral regurgitation. RV size and function were preserved. Elevated PA systolic and right sided filling pressures were also present.

Pregnancy increases the demands of the cardiovascular system. Normal and expected changes include an increase in cardiac output by 30-50%, increase in preload, decrease in afterload due to decreased SVR, and an increase in maternal heart rate by 15-20 beats per minute.¹ Pregnancy signs and symptoms can mimic cardiac decompensation and sometimes can be difficult to diagnose.

Pregnancy changes can unmask an underlying cardiomyopathy or can exacerbate a new cardiomyopathy. In the case of an underlying cardiomyopathy, it can be difficult to identify a pathologic process prior to pregnancy, unless a careful history is taken.

Peri-partum cardiomyopathy by definition occurs in the final month of pregnancy or the first five months post-partum.²

Several risk factors have been identified. Some of these include extremes of reproductive age, multiparity, multi-gestation births and smoking.² Our patient had several of these risk factors.

Pregnancy associated cardiomyopathy is another form of cardiomyopathy that can occur prior to the last month of pregnancy, as in the case of our patient. This is a rarer form, but has been illustrated in the literature.

Treatment of these cardiomyopathies is similar to other forms of heart failure with the exception of avoidance of ACE inhibitors/ARBs if the patient is still pregnant. Also, in many cases, delivery of the fetus may be warranted to protect life of mother and fetus.

In the case of peri-partum cardiomyopathy, normalization of LVEF occurs in 50% of patients within six months of delivery and is most likely to normalize if LVEF >30% at the time of delivery. Recurrence during subsequent pregnancies can occur in up to 30%.² Women should be counseled extensively about this higher risk.

The most common cause of death is worsening heart failure, arrhythmias, and thromboembolic events as the incidence of LV thrombus in these patients is high.²

Early diagnosis is critical to prevent a delay in treatment.

Our patient's BNP was elevated; however, given the demands of pregnancy with the increased preload and potential increase in myocardial stretch, should we see an expected elevation of BNP?

BNP levels do increase but should remain in the normal range. Any elevation above the normal range should make one suspicious for decompensated congestive heart failure.

A longitudinal analysis of 29 healthy pregnant women with BNP levels drawn each trimester were compared to 25 non-pregnant healthy controls. The average BNP level for pregnant women was 20 pg/ml in the first trimester, 18 pg/ml in the second, 26 pg/ml in the third and 18 pg/ml in the post-partum period compared to 10 pg/ml in the controls. Even though the BNP levels were nearly double that of non-pregnant women, these values are still well within normal limits.⁵

In normal pregnancies, median BNP levels are < 20 pg/ml (range 5-70 pg/ml) and remain stable throughout gestation.³ There is an intrinsic ability to adapt to the hemodynamic stress of pregnancy. A BNP value < 100 pg/ml appears to have a high negative predictive value for ruling out decompensated heart failure during pregnancy.¹

In summary, a BNP level within the normal range (< 100 pg/ml) appears to be highly predictive of ruling out decompensated heart failure in pregnancy. A value above the normal range (> 100 pg/ml) may suggest a diagnosis of decompensated heart failure during pregnancy and further work up should be considered.

References

1. Tanous D, Siu SC, Mason J, Greutmann M, Wald RM, Parker JD, Sermer M, Colman JM, Silversides CK. B-type natriuretic peptide in pregnant women with heart disease. J Am Coll Cardiol 2010;56:1247-1253.
2. Demakis JG, Rahimtoola SH, Sutton GC, Meadows WR, Szanto PB, Tobin JR, Gunnar RM. Natural course of peripartum cardiomyopathy. Circulation 1971;44:1053-1061.
3. Resnik JL, Hong C, Resnik R, Kazanegra R, Beede J, Bhalla V, Maisel A. Evaluation of b-type natriuretic peptide (bnp) levels in normal and preeclamptic women. Am J Obstet Gynecol. 2005;193:450-454.
4. Yurteri-Kaplan L, Saber S, Zamudio S, Srinivasan D, Nyirenda T, Alvarez M, Al-Khan A. Brain natriuretic peptide in term pregnancy. Reprod Sci. 2012;19:520-525.
5. Hameed AB, Chan K, Ghamsary M, Elkayam U. Longitudinal changes in the b-type natriuretic peptide levels in normal pregnancy and postpartum. Clin Cardiol. 2009;32:E60-E62.