Pregnancy is accompanied by major physiological changes, which place extra demands on the cardiovascular system. These include an increase in plasma volume (up to 40%) and cardiac output (30–50%). The increased cardiac output is mainly attributable to augmented stroke volume and a modest increase in heart rate. The increase in stroke volume is secondary to an increase in blood volume, as well as a reduction in systemic vascular resistance. Additional stresses are placed on the cardiovascular system during labour and delivery. During labour cardiac output increases by a further 20% during each uterine contraction because of the increased venous return from the contracting uterus and the sympathetic response to pain. Delivery can result in significant blood loss.8–10
Although these changes may be expected to affect the course of pregnancy in women with hypertrophic cardiomyopathy there have been few systematic studies. This analysis of 127 women with hypertrophic cardiomyopathy assessed 271 pregnancies over 40 years. In the total population the majority (92; 71.5%) of women were asymptomatic during pregnancy; over 90% of women who reported symptoms had experienced similar symptoms before pregnancy. Prepregnancy symptoms worsened in the minority, although palpitations occurred more frequently during pregnancy in women who had previously reported them. Some patients reported an improvement in their symptoms during pregnancy. Symptoms did not necessarily reoccur in subsequent pregnancies and significant symptom deterioration was not reported. Pulmonary oedema was seen in two women postnatally. These two women have not reported any long term deterioration in their health since pregnancy. The explanation for pulmonary oedema in these two patients is not clear; in one case pulmonary oedema may have been related to excessive use of intravenous fluid to treat hypotension.
Hypertrophic cardiomyopathy was diagnosed in the majority of women in this study (89; 70%) before, during, or in between pregnancies. However, hypertrophic cardiomyopathy was diagnosed after completion of all pregnancies in 30% of women, thus raising the possibility that these patients were unaffected at the time. Ten (26.3%) of these women, however, reported cardiac symptoms before pregnancy and, as hypertrophy normally develops during or shortly after adolescence,11,12
it is a reasonable expectation that the majority of these women were affected at the time of pregnancy. Even when these patients were excluded from the analysis the number of reported and observed complications remained low.
This series of women with hypertrophic cardiomyopathy included patients with and without risk factors for sudden cardiac death, as well as patients who had undergone myectomy, dual chamber pacing, and ICD implantation before and after pregnancy. No clinical or echocardiographic feature was associated with a poor outcome during pregnancy. Indeed, given the low frequency of adverse events seen in pregnancy, correlations between clinical and echocardiographic features and adverse events would be difficult to show.
One of the most important concerns is whether there is an increased risk of death during pregnancy in hypertrophic cardiomyopathy. In this series no maternal deaths occurred. Interrogation of the extended database of 400 women seen at this centre since 1989 found 45 recorded deaths (mean (SD) age 47 (19) years, range 7–82 years). The cause of death was sudden unexplained death in 23, heart failure related in 14, and unrelated to hypertrophic cardiomyopathy in eight women. No patient died during pregnancy or soon after—that is, within six months. Data from the Confidential Enquires into Maternal Deaths, which registers and investigates all maternal deaths in the UK, also confirms a low mortality in pregnancy. Two of 446 maternal deaths between 1991 and 1996 (figures from 1996 onwards are not yet published) were related to hypertrophic cardiomyopathy.13,14
One woman known to have hypertrophic cardiomyopathy died of congestive cardiac failure four weeks after delivery. The other had a sudden death five days after delivery and necropsy showed hypertrophic cardiomyopathy.
Epidural anaesthesia has generally not been advised during pregnancy in women with hypertrophic cardiomyopathy because of its potential to cause venous pooling, to reduce filling pressures, and potentially to exacerbate left ventricular outflow tract gradient.15,16
In this study, women who received epidural anaesthesia reported few complications; however, some women may have been unaware of complications and not all obstetric records were available. Moreover, few women had documented left ventricular outflow tract obstruction before pregnancy. In those who reported hypotension or dizziness it is unclear whether this was an exaggeration of a normal response to epidural anaesthesia or whether this was a function of worsening labile left ventricular outflow tract gradient. Thus, until more information becomes available epidural anaesthesia should continue to be used cautiously in women with outflow tract gradient.
Much of the data concerning the safety of cardioactive medications during pregnancy have come from either isolated case reports or uncontrolled data. Amiodarone has been associated with neurotoxicity and fetal/neonatal hypothyroidism, and both β blockers and amiodarone have been associated with intrauterine growth retardation and death. In this study all the recorded fetal intrauterine deaths occurred in women taking β blockers, amiodarone, or both during pregnancy. Although the small numbers of patients makes it difficult to derive definitive conclusions, these and earlier data suggest that where possible medication should be reduced in pregnancy.
The main limitation of this study lies in its retrospective nature; however, a large prospective analysis is unlikely given the inherent difficulties encountered when studying the effects of pregnancy in an uncommon disease.
Questionnaires may be subject to responder bias but where possible the results were validated by review of the medical and obstetric notes. Only a minority of symptomatic complaints remained unconfirmed.
We acknowledge that only surviving women were targeted with questionnaires. However, as already stated, no patient reviewed at our institution has died during or within six months of pregnancy. Thirty five women (18%) did not return questionnaires; these patients could not be traced because of recent change of address. However, all but one of these patients were aged over 40 when last reviewed at this centre and are therefore unlikely to contribute to pregnancy related mortality data.
These data suggest that patients with hypertrophic cardiomyopathy generally tolerate pregnancy well without significant symptoms or complications. The cohort studied was representative of the general population of patients with hypertrophic cardiomyopathy including patients with typical symptoms (chest pain, breathlessness, and syncope), patients with one or more risk markers for sudden cardiac death, and patients having undergone myectomy or other invasive procedures. There were no deaths, and no particular clinical or echocardiographic feature was associated with a poor outcome. Although the presence of a significant left ventricular outflow tract gradient did not affect maternal outcome, the effect of epidural could not be fully evaluated in these patients. This study did not include patients with previous heart failure or severe restrictive physiology. These phenomena are rare in hypertrophic cardiomyopathy and such patients rarely contemplate pregnancy. However, the physiological demands of pregnancy in these patients would be expected to lead to haemodynamic compromise and therefore we would not recommend pregnancy in these patients.