Peripartum cardiomyopathy: Causes, diagnosis, and treatment

Heart failure during pregnancy was recognized as early as 1849, but it was first described as a distinctive form of cardiomyopathy only in the 1930s.¹ In 1971, Demakis et al² described 27 patients who presented during the puerperium with cardiomegaly, abnormal electrocardiographic findings, and congestive heart failure, and named the syndrome peripartum cardiomyopathy.

The European Society of Cardiology³ recently defined peripartum cardiomyopathy as a form of dilated cardiomyopathy that presents with signs of heart failure in the last month of pregnancy or within 5 months of delivery.

Peripartum cardiomyopathy is relatively rare but can be life-threatening. The National Hospital Discharge Survey (1990–2002) estimated that it occurs in 1 in every 2,289 live births in the United States.⁴ The disease appears to be more common in African American women.¹ The rate varies in other populations: it is highest in Haiti, with 1 case in 300 live births, which is nearly 10 times higher than in the United States.⁵ The reason for such a variation remains unclear.

Although early reports suggested the death rate was nearly 50%, more recent reports show it to be 0 to 5% in the United States, and the higher numbers in the earlier reports likely represented publication bias.^5,6–9

WHAT CAUSES IT?

Peripartum cardiomyopathy is generally considered a form of idiopathic primary myocardial disease associated with the pregnant state. Although several plausible etiologic mechanisms have been suggested, none of them is definite. Some are discussed below.

Myocarditis

Myocarditis has been found on endomyocardial biopsy of the right ventricle in patients with peripartum cardiomyopathy,^10,11 with a dense lymphocytic infiltrate and variable amounts of myocyte edema, necrosis, and fibrosis. The prevalence of myocarditis in patients with peripartum cardiomyopathy ranged from 8.8% to 78% in different studies.^12,13 On the other hand, the presence or absence of myocarditis alone does not predict the outcome of peripartum cardiomyopathy.⁷

Cardiotropic viral infections

After a viral infection, a pathologic immune response might occur that is inappropriately directed against native cardiac tissue proteins, leading to ventricular dysfunction.

Bultmann et al¹⁴ found parvovirus B19, human herpes virus 6, Epstein-Barr virus, or cytomegalovirus DNA in endomyocardial biopsy specimens from 8 (31%) of 26 patients with peripartum cardiomyopathy that was associated immunohistologically with interstitial inflammation.

Kühl et al¹⁵ found, in patients with viral infection confirmed by endomyocardial biopsy, that the median left ventricular ejection fraction improved in those in whom the virus was cleared (from 50.2% before to 58.1% afterward, P < .001), whereas it decreased in those in whom the virus persisted (from 54.3% before to 51.4% afterward, P < .01).

Lyden and Huber¹⁶ found that mice developed worse myocarditis if they were experimentally infected with coxsackievirus and echovirus during pregnancy than if they were infected while not pregnant.

Chimerism

In a phenomenon called chimerism, cells from the fetus take up residence in the mother (or vice versa), sometimes provoking an immune response.^17,18

As reviewed by Ansari et al,¹⁹ the serum from patients with peripartum cardiomyopathy has been found to contain autoantibodies in high titers, which are not present in serum from patients with idiopathic cardiomyopathy. Most of these antibodies are against normal human cardiac tissue proteins of 37, 33, and 25 kD. The peripheral blood in these patients has a high level of fetal microchimerism in mononuclear cells, an abnormal cytokine profile, and low levels of CD4+ CD25lo regulatory T cells.

Warraich et al,²⁰ in a study from South Africa, Mozambique, and Haiti, found that the frequencies and reactivities of immunoglobulins were similar in distribution in patients with peripartum cardiomyopathy, irrespective of the geographic location.

Apoptosis and inflammation

Apoptosis (programmed cell death) of cardiac myocytes occurs in heart failure and may contribute to progressive myocardial dysfunction. ²¹ Experiments in mice suggest that apoptosis of cardiac myocytes has a role in peripartum cardiomyopathy.²²

Fas and Fas ligand are cell surface proteins that play a key role in apoptosis. Sliwa et al,²³ in a single-center, prospective, longitudinal study from South Africa, followed 100 patients with peripartum cardiomyopathy for 6 months. During this time 15 patients died, and those who died had significantly higher plasma levels of Fas/Apo-1 (P < .05). In the same study, plasma levels of C-reactive protein and tumor necrosis factor alpha (markers of inflammation) were elevated and correlated with higher left ventricular dimensions and lower left ventricular ejection fractions at presentation.

In the Studies of Left Ventricular Dysfunction,²⁴ circulating levels of tumor necrosis factor alpha and interleukin 6 increased in patients as their functional heart failure classification deteriorated.

An abnormal hemodynamic response

During pregnancy, blood volume and cardiac output increase. In addition, afterload decreases because of relaxation of vascular smooth muscle. The increases in volume and cardiac output during pregnancy cause transient and reversible hypertrophy of the left ventricle to meet the needs of the mother and fetus. Cardiac output reaches its maximum at around 20 weeks of pregnancy.²⁵

The transient left ventricular systolic dysfunction during the third trimester and early postpartum period returns to baseline once the cardiac output decreases.^26,27

Other possible factors

Other possible etiologic factors include prolactin,^28,29 relaxin,³⁰ immune complexes,³¹ cardiac nitric oxide synthase,³² immature dendritic cells,³³ cardiac dystrophin,³⁴ and toll-like receptors.³⁵