Postpartum cardiomyopathy (PPCM) is a rare and severe form of heart failure that emerges in previously healthy women near the end of pregnancy or in the months immediately following delivery. As a type of dilated cardiomyopathy, PPCM involves a weakening of the heart muscle that significantly impairs its ability to pump blood effectively. Because the causes are complex and not fully understood, research focuses on the unique biological changes that occur during the perinatal period.
Understanding Postpartum Cardiomyopathy
Postpartum cardiomyopathy is a heart muscle disorder that occurs during the final month of pregnancy or up to five months after childbirth. The condition is characterized by systolic dysfunction, meaning the left ventricle, the heart’s main pumping chamber, cannot contract forcefully enough. This results in a reduced left ventricular ejection fraction (LVEF), the measurement of blood pumped out with each beat, falling below the normal range.
The weakened heart muscle leads to symptoms of congestive heart failure, which are often difficult to distinguish from the discomforts of late pregnancy. Women with PPCM commonly experience persistent shortness of breath, which can worsen when lying flat, and significant fatigue. Other signs include swelling in the feet and legs due to fluid retention and a rapid or fluttering heart rate. Diagnosis requires that there is no prior history of heart disease and no other identifiable cause for the heart failure.
Primary Biological Mechanisms of PPCM
The most prominent scientific theory for PPCM centers on an abnormal hormonal pathway involving the pituitary hormone prolactin. While prolactin normally stimulates milk production, high levels of oxidative stress are believed to be present in the heart and blood vessels during the peripartum period in women who develop PPCM.
This increased oxidative stress acts as a trigger, causing the full-length prolactin hormone (23-kDa) to be cleaved by an enzyme called Cathepsin D. The resulting fragment is a smaller, highly toxic piece known as 16-kDa prolactin. This 16-kDa fragment is antiangiogenic, meaning it prevents the formation of new blood vessels necessary for proper heart function.
The toxic fragment directly damages the endothelial cells lining the heart’s blood vessels, leading to widespread microvascular dysfunction. This process starves the surrounding heart muscle tissue of oxygen and nutrients, triggering cell death and inflammation. The 16-kDa prolactin fragment also promotes inflammation and cellular apoptosis in the heart muscle cells. Blocking the production of this toxic fragment, such as with the drug bromocriptine in clinical trials, has shown promise in treatment.
Another biological contributor involves an abnormal inflammatory and immune response. Pregnancy involves complex shifts in the immune system, and in some PPCM patients, the body’s defenses may mistakenly target the heart tissue. Researchers have also noted the involvement of sFlt1, a protein released by the placenta that inhibits vascular endothelial growth factor (VEGF).
Elevated levels of sFlt1 are often seen in conditions like preeclampsia and twin pregnancies, contributing to widespread vascular damage and inflammation. The combination of high sFlt1 and the toxic 16-kDa prolactin fragment creates a hostile environment that severely compromises blood flow and injures heart muscle cells. A less common hypothesis suggests that a preceding viral infection, leading to myocarditis, may act as a trigger in genetically susceptible individuals.
Factors That Increase Susceptibility
While PPCM can affect any pregnant woman, several pre-existing conditions and demographic factors increase susceptibility. One consistently identified risk factor is a pregnancy with multiple gestations, such as twins or triplets. This increased fetal mass places a greater hemodynamic strain on the maternal cardiovascular system and is associated with higher levels of placental factors like sFlt1.
Maternal age is also relevant, as the risk of PPCM increases for women over 30 years old. Pre-existing hypertensive disorders, particularly preeclampsia and eclampsia, are strong predictors of PPCM due to shared underlying mechanisms of oxidative stress and vascular damage. A woman who has previously experienced PPCM faces a high risk of recurrence in subsequent pregnancies.
Other medical comorbidities that increase susceptibility include gestational diabetes, obesity, and a history of substance use. While PPCM is considered a sporadic disease, a small percentage of cases appear to have a genetic component, suggesting the predisposition can be inherited. Certain ethnic backgrounds, such as women of African heritage, also show a statistically higher incidence of PPCM.
Detection and Initial Management
Detection of PPCM begins when a doctor suspects heart failure based on a patient’s symptoms, which are often dismissed as normal effects of pregnancy or the postpartum period. A laboratory blood test for B-type natriuretic peptide (BNP) or N-terminal pro-BNP is a common first step, as elevated levels of these cardiac biomarkers indicate heart muscle stress.
The definitive diagnosis relies on a heart ultrasound called an echocardiogram, which visually assesses heart function. PPCM is confirmed if the left ventricular ejection fraction (LVEF) is found to be less than 45%, indicating significantly reduced pumping strength. Initial management focuses on stabilizing the patient and preventing complications associated with heart failure.
Treatment immediately aims to reduce the fluid overload that stresses the heart, often through the use of diuretics. Medications commonly used for other forms of heart failure, such as beta-blockers, are initiated to slow the heart rate and allow the heart muscle recovery time. Patients with PPCM are at an increased risk of developing blood clots, so blood-thinning medication is frequently prescribed, especially if heart function is severely impaired.