Although the term peripartum cardiomyopathy has been used widely, at least until recently, little evidence supported a unique pregnancy-induced cardiomyopathy. Pearson (2000) reported findings of a workshop of the National Heart, Lung, and Blood Institute that established the following diagnostic criteria: 1.
Development of cardiac failure in the last month of pregnancy or within 5 months after delivery, 2.
Absence of an identifiable cause for the cardiac failure, 3.
Absence of recognizable heart disease prior to the last month of pregnancy, and 4.
Left ventricular systolic dysfunction demonstrated by classic echocardiographic criteria, such as depressed ejection fraction or fractional shortening along with a dilated left ventricle (Fig. 49-5).
he etiology of peripartum cardiomyopathy remains unknown, and proposed causes include viral myocarditis, abnormal immune response to pregnancy, aberrant response to the greater hemodynamic burden of pregnancy, hormonal interactions, malnutrition, inflammation, and apoptosis (Elkayam, 2011). Another suggests that oxidative stress during late pregnancy leads to the proteolytic cleavage of prolactin (Hilfiker-Kleiner, 2014). The resulting 16-kDa prolactin
FIGURE 49-5 Peripartum cardiomyopathy with mild pulmonary edema. Anterior-posterior projection chest radiograph of a woman with an abnormally enlarged heart and mild perihilar opacification consistent with dilated cardiomyopathy.
fragment is cardiotoxic and can impair cardiomyocyte metab olism and contractility. Bromocriptine therapy has been suggested because it inhibits prolactin secretion. In one pre liminary study, bromocriptine improved recovery of afected women, and a randomized trial is currently recruiting patients (Haghikia, 2015; Sliwa, 2010).
Hypertensive disorders frequently coexist with peripartum cardiomyopathy, and another proposed mechanism links peripartum cardiomyopathy to preeclampsia (Cunningham, 2012; Fong, 2014; Patten, 2012). Antiangiogenic factors-already known to be associated with preeclampsia-can induce peripartum cardiomyopathy in susceptible mice. hus, cardiomyopathy may be precipitated by antiangiogenic factors in a host made susceptible because of insuicient proangiogenic factors.
Several investigators describe a common pathway linking these suggested etiologies (Arany, 2016; Hiliker-Kleiner, 2014). Specifically, unbalanced oxidative stress and a high level of prolactin leads to production of the 16-kDa prolactin fragment that seems to both initiate and propagate the disease. The fragment, which mainly afects the endothelium, together with additional antiangiogenic factors might disturb the angiogenic balance during the puerperium and thereby impair cardiac function.
With no proven etiology, the diagnosis of peripartum cardiomyopathy currently requires that other causes of cardiac dysfunction be excluded. Biiltmann and coworkers (2005) studied endomyocardial biopsy specimens from 26 women with peripartum cardiomyopathy and reported that more than half had histological evidence of "borderline myocarditis." hey noted viral genomic material for parvovirus B 19, human herpesvirus 6, Epstein-Barr virus, and cytomegalovirus. From Parland Hospital, otherwise "idiopathic" heart failure was found to be caused by hypertensive heart disease, clinically silent mitral stenosis, obesity, or viral myocarditis (Cunningham, 1986). Indeed, 20 percent of women with treated chronic hypertension in pregnancy have concentric hypertrophy (Ambia, 2017).