Hypertrophic Cardiomyopathy and Pregnancy: A Retrospective Analysis From a Tertiary Care Hospital

In this retrospective analysis, we collected clinical, imaging, management, and follow-up data on patients from the HCM registry maintained in the cardiology department. Obstetric history was also recorded. In addition, we obtained data on all women with HCM who were registered in the cardio-obstetric clinic and who delivered between January 2010 and June 2019. The diagnostic criterion for HCM was unexplained left ventricle hypertrophy of at least 13 mm or greater than 2 SDs as corrected for body surface area by echocardiography.¹  Patients with any disorder that could produce that magnitude of left ventricular hypertrophy, including aortic stenosis and systemic hypertension, were excluded from our study. The study was approved by the Postgraduate Institute of Medical Education and Research ethics committee.

Clinical data, mode of delivery, weeks' gestation at delivery, and antenatal, intrapartum, and postpartum complications were noted. The modified WHO class, the severity of left ventricular hypertrophy, the presence of LVOTO, and previous procedures or arrhythmias were also noted. Significant and marked LVOTO were defined as gradients, either at rest or with provocation, of at least 30 mm Hg and at least 50 mm Hg, respectively.¹⁰ 

We identified 7 women (mean [SD] age, 25 [3.3] years) who had HCM and who had a total of 15 pregnancies (range per woman, 1–4) during the study period. All 7 women were part of the cardiology department's HCM cohort, and 3 were registered in the cardio-obstetric clinic. The most common symptoms were exertional breathlessness and palpitations. Only 1 patient (patient 3) had a syncopal attack during pregnancy. Mean (SD) left ventricular wall thickness was 19.71 (2.56) mm. Left ventricular outflow tract obstruction was present in 7 pregnancies (Fig. 1), whereas nonobstructive HCM occurred during 8 pregnancies. Arrhythmias, including atrial fibrillation, were not recorded in any patient. Detailed clinical characteristics and pregnancy outcomes of all 7 patients are presented in Table I. All patients tolerated labor well with no aggravation of symptoms. One patient (patient 4) developed progressive breathlessness, chest pain, and palpitations (New York Heart Association class III) after her first pregnancy. She underwent successful alcohol septal ablation with abolition of the gradient 2 years after her first pregnancy (Fig. 2). The patient remained asymptomatic during 2 subsequent pregnancies. Only 1 patient (patient 6) had a restrictive filling pattern on echocardiography during pregnancy; however, the pattern was transient and was not seen on postdelivery echocardiograms.

We have reported clinical and outcomes data on 15 pregnancies in 7 women over a 9-year period. Only 1 woman was diagnosed as having HCM during pregnancy, whereas 6 had been diagnosed before pregnancy. In our institute, 52,868 deliveries took place during this period. Assuming a prevalence of HCM of 1 in 500 in the general population, we would expect more than 100 of these women to have HCM.¹  In our previous study, we showed that HCM often remained undiagnosed during pregnancy.⁵  This is because most pregnant women with HCM in the community either remain asymptomatic or have only mild symptoms that do not bring attention to the underlying condition.^3,11  Our current findings show that underdiagnosis of HCM holds true in the current era. There was no overlap of patients between our 2 studies. Only women in whom key symptoms developed during pregnancy or who were previously diagnosed as having HCM come to medical attention. The true prevalence of HCM in pregnant women can be determined only if routine echocardiographic screening is performed in this group.

Our study population was a high-risk cohort, with 7 (46.7%) pregnancies falling in modified WHO class III. Most of the 7 patients tolerated pregnancy well; 3 patients were asymptomatic, and 2 had only mild symptoms. Two women had severe symptoms (New York Heart Association class III or IV) in the third trimester, but symptoms resolved for both of them within 1 week after delivery. Six of the 15 pregnancies (40%) were low risk according to the (modified WHO class II, and the women tolerated pregnancy well.

Maternal and fetal outcomes in previous studies of pregnancy in women with HCM are summarized in Table II.^3–9,11  Although maternal deaths were rare, heart failure and arrhythmias were reported in approximately 30% of the pregnancies in some series.^6,11  The larger studies lack detailed clinical profiles of patients in whom complications developed.^3,4 

Left ventricular outflow tract obstruction is associated with a higher risk of pregnancy complications.²  In our study, LVOTO was present in 7 pregnancies. Patients were asymptomatic in 3 of the pregnancies, whereas mild exertional breathlessness occurred in 2. Severe symptoms developed in 2 pregnancies (28.6%) in the third trimester, but improved within 2 days of delivery. Pregnancy can have a variable effect on LVOTO. The increase in preload during pregnancy can potentially reduce the left ventricular outflow tract gradient, whereas increased contractility and reduction in afterload can increase the gradient.^12,13  Overall, left ventricular out-flow tract gradients tend to increase in pregnancy.²  One woman in this study also developed LVOTO for the first time in her fourth pregnancy. This likely was caused by hemodynamic changes in pregnancy, because the gradient decreased from 103 mm Hg to 25 mm Hg after delivery. In other women with LVOTO in our study, the gradient did not decrease after delivery.

Left ventricular outflow tract obstruction was absent in 8 pregnancies. These patients tolerated pregnancy well. Only 1 woman had transient breathlessness at rest after intravenous fluid infusion. This patient had a restrictive filling pattern on echocardiography, which was not seen on postdelivery echocardiograms. The restrictive filling pattern was likely caused by plasma volume expansion and an increase in preload during pregnancy in the presence of diastolic dysfunction caused by HCM.¹⁴ 

One patient had 2 pregnancies after successful alcohol septal ablation. She was asymptomatic during pregnancy and in the postpartum period. Because of a paucity of data, patients who have undergone alcohol septal ablation have not been included in the modified WHO classification for maternal cardiovascular risk.²  This holds true even for risk stratification for sudden death. Patients who have undergone alcohol septal ablation or myectomy are also excluded from the HCM risk scores for sudden death.^2,10 

Labor is usually well tolerated in women with HCM. Only 9% of pregnant women develop transient aggravation of symptoms.³  Vaginal delivery is recommended for women with HCM.²  In our study, cesarean deliveries were conducted only for obstetric indications. All patients tolerated labor well. The only drugs used were metoprolol in 4 pregnancies and loop diuretics in 2. Adverse maternal outcomes, including death, were not seen in any patient. One pregnancy ended preterm. There were 2 spontaneous abortions, and 1 fetus had intrauterine growth retardation. All women who became symptomatic during pregnancy had relief of symptoms after delivery.

Hypertrophic cardiomyopathy commonly remains undiagnosed during pregnancy. Our findings show that most women were asymptomatic or had only mild symptoms. Of the women with LVOTO, 28.6% had severe symptoms that improved after delivery. No adverse maternal outcomes were noted. Pregnancies were well tolerated after successful alcohol septal ablation.

Conflict of Interest Disclosure: None

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