Rheumatic heart disease (RHD) has been one of the major forms of heart disease in developing countries like India. Pregnancy associated with any form of heart disease has been a challenge for Obstetricians and Cardiologists and is one of the major causes of maternal and foetal morbidity and mortality. It is the most prevalent organic valve disease encountered in pregnant women in south Asia.1 Almost 80% of the rheumatic valvular lesions are mitral stenosis,2-6 thus being the commonest form of RHD associated with pregnancy.

Normal pregnancy is associated with a hyperdynamic circulatory state characterized by an increase in blood volume, heart rate, stroke volume and a decrease in the systemic vascular resistance.7-10 Increased cardiac output, usually by 50%, may lead to the unmasking of a previously asymptomatic valve lesion and worsening of already symptomatic lesion.11 Mitral stenosis poses special problems in pregnancy as the already compromised heart is stressed further with hypervolaemia of pregnancy and stress of labour. In patients with mitral stenosis (MS), increased blood volume and tachycardia impair the left atrial emptying and can lead to a significant rise in the venocapillary pulmonary pressure. This haemodynamic stress along with other factors like anaemia, atrial fibrillations and thromboembolism may precipitate acute pulmonary oedema and cardiogenic shock leading to unacceptable maternal and foetal mortality.7,12,13 Foetus-in-utero also suffers from chronic placental insufficiency and anoxia resulting in to intrauterine growth retardation (IUGR) and preterm deliveries.

Open and closed mitral commissurotomy can be performed but the procedure still carries a significant morbidity and mortality.14-18 Over the years, management of mitral stenosis has changed from medical-symptomatic to open surgical therapy to minimally invasive cardiac surgery. Today, Balloon Mitral Valvuloplasty (BMV) has made its place due to its technical simplicity and reproducibility, if required.

Present study aims at the evaluation of pregnant patients with rheumatic mitral stenosis treated with BMV in terms of maternal and foetal outcome.

Material and Methods

This is a retrospective study of 52 pregnant patients with rheumatic mitral stenosis attending for Obstetric care over a 5 year period at a tertiary hospital of a teaching Institute.

The two dimensional (2-D) echocardiography was performed before the procedure to measure the mitral valve area (MVA) and assess the valve morphology.19 The BMV was performed under local anaesthesia with abdomino-pelvic shielding and under fluoroscopic guidance using Inoue balloon catheter technique in the Cardiology department. After the procedure the valve area was reassessed by 2-D echocardiography. Procedure was considered successful if there was significant increase in the valve area with symptomatic improvement in the functional class within 24 hours.

All these cases were evaluated for success of the procedure and maternal - foetal outcome.

Maternal parameters included age, parity, timing of BMV, fluoroscopy time, functional status as per New York Heart Association (NYHA) and 2-D echocardiographic findings (MVA – pre and post BMV), mode of delivery and evidence of any medical/ obstetrics complications (morbidity/mortality).

Foetal outcome included prematurity, birth weight, IUGR, stillbirths, need of intensive neonatal care and survival.

Obstetric monitoring

All patients underwent detailed antenatal evaluation including ultrasonography (USG) and biophysical monitoring for foetal well being before and after the procedure until delivery.

Patients were allowed to go in spontaneous labour unless having any obstetric indication for induction of labour or caesarean section.

Observations and analysis
Patient Profile (Age and Gravida) (Table 1)

Majority of patients were between 20 and 25 years of age. 19 patients were primigravidas and remaining were multigravidas, 9 being gravida four and above.

All these women were receiving Penicillin prophylaxis. On admission most of the patients were symptomatic in spite of medical line of treatment.

Timing of BMV (Table 2)
In 5 patients BMV was performed before pregnancy. All these were primigravidas. In 47 patients BMV was performed during pregnancy.

To avoid detrimental effects during organogenesis the optimal time for BMV is considered to be after 20 weeks of gestation. In the present study all the patients were above 20 weeks of gestation including 8 patients who were more than 32 weeks of gestation at the time of BMV. In one of the patients of this group BMV could not be performed because of onset of labour.

Functional Class (NYHA) and Mitral Valve Area (MVA) (Table 3)
Pre-procedure mitral valve area (MVA) evaluated by echocardiography was in the range of 0.6 - 1.2 cm2 with mean of 0.82 cm2 .

New York Heart Association (NYHA) classification was used to determine the functional class of the patients. 20 patients (38.46%) belonged to functional class III while 7 patients (13.46%) belonged to class IV as per NYHA criteria.

Result of the procedure (Table 3)
Study revealed that BMV procedure was effective in 50 patients with significant increase in mitral valve area and symptomatic relief within 24 hours (success - 96%). Mean mitral valve area increased from 0.82 cm2 to 1.73 cm2 (mean increase – 0.9 cm2) after BMV procedure.

Functional improvement was seen at least by one grade as per NYHA criteria. Almost all the cases belonging to the Functional class (FC)- III and IV were reverted to FC - II or I, except one case belonging to FC- IV. This patient, a fourth gravida second para with one abortion, was seriously ill and had critical mitral stenosis with severe pulmonary hypertension at 24 weeks of gestation. She developed pulmonary oedema and in spite of all measures deteriorated within 48 hours and could not be revived.

2 patients developed complication of pulmonary oedema. One could be revived but the other could not be revived.

Obstetric outcome (Table 4)
Maternal Outcome
Obstetric outcome was good with 38 (76%) vaginal deliveries with 8 (21.05%) forceps applications to cut short the second stage of labour. There were 10 (20%) caesareans for obstetric indications and only 2 (4%) abortions. There were 2 (3.9%) cases of pulmonary oedema and one (1.96%) maternal death.

Foetal Outcome
Majority no.-32 (66.6%) of the babies were more than 2.5 kg at birth. There were only 4 (8.3%) preterm deliveries while a high percentage of them no.-44 (91.6%) had term deliveries. Only 9 (18.75%) babies were small for gestation (IUGR).There was only one (2.03%) stillbirth and 9 (18.75%) required neonatal intensive care without any neonatal mortality.

Discussion
Rheumatic heart disease remains the commonest type of heart disease in pregnant women in many countries and upto 75-80% of these pregnant women have dominant MS.2,3,20

Deterioration may occur in as many as 25% patients.11 The maternal death rate is 1% and varies directly with the NYHA functional class ( 0.4 % for Class-I and II and 6.8 % for Class-III and IV).7-10,12 It can be as high as 17% with complications like atrial fibrillations, highest risk being during the stress of labour and delivery.11

Ideally the condition needs treatment before the patient conceives; but it rarely happens so. Either the pregnancy unmasks the underlying condition for the first time or even when diagnosed earlier no treatment is sought for till patient becomes pregnant.20,21 Untreated mitral stenosis poses a threat to maternal and foetal life and hence active treatment needs urgent consideration to avoid morbidity and mortality.

Most of the times patients are managed medically, but patients of severe mitral stenosis managed only on medical line pose a difficult challenge with unacceptable maternal and foetal complications.11 Thus in symptomatic patients with dominant mitral stenosis (MVA < 1.5 cm2) and not stabilized on medical line, surgical intervention to increase the valve area should be undertaken.

Open heart surgery during pregnancy is associated with 15-33% risk of foetal mortality associated with the use of extracorporeal circulation (use of high dose Heparin and hypotension) and induced hypothermia22 and also with high maternal mortality.14,18

BMV by Inoue balloon technique offers an alternative safe method to these surgically high-risk pregnant women due to its simplicity, short time in expert hands, use of only local anaesthesia and effectiveness in terms of increase in the mitral valve area. The procedure has established its safety during pregnancy and is being performed widely over the last decade for cases of severe mitral stenosis.21,23-29.

Although the procedure is effective, long term effects of foetal exposure to radiation during the use of fluoroscopy is a matter of concern and needs to be studied further. Most of the radiation received by the foetus is from the scatter and this has been estimated to be on an average 0.2 rads during the procedure.30 Also, beyond doubt it is now clear that radiation exposure after 20 weeks of gestation is unlikely to produce any form of major abnormalities.31-33 Most of the centres take only short time (Table 5)28,34,11,35 for the procedure and use abdomino-pelvic shielding very judiciously , thus minimizing the radiation exposure to the foetus.

At our centre too, we had excercised these precautions strictly ( timing of BMV – after 20 weeks of gestation, adequate use of abdomino-pelvic shield and average time of fluoroscopy – 4.2 min) and therefore we believe that the risk of radiation was negligible to our patients. Multiple studies have reported safety of this procedure in terms of radiation exposure.21,26,36 Mangione et al showed in his 5 year follow-up that all children exposed to radiation during such a procedure had normal growth and development without any clinical abnormalities.26 Therefore, if the procedure is carried out after 20 weeks of gestation with adequate abdomino-pelvic shielding and fluoroscopy is used only when required, the benefits of the procedure far outweigh the risks associated.

According to Barbosa et al20 mitral valve area (MVA) as measured by 2-D echocardiography and the functional class (NYHA) are the most important predictor variables to determine the outcome. In the study by Barbosa et al, progression to class III or IV from I or II was the most common (48.8%) maternal complication in pregnant women with mitral stenosis.20 The maternal death rate is nearly 1% and varies directly with the functional class (0.45% for FC - I, II and 6.8% for FC - III, IV).7-10, 12 In addition to the functional class, mitral valve area (MVA < 1.5 cm2) also strongly and significantly correlated with the maternal events.20

In contrast to the maternal complications, Barbosa et al found that, the foetal/neonatal complications do not correlate with the mitral valve area (MVA) or functional class.20 This finding could be explained in part by high percentage of premature births and low birth weights even among patients with less severe heart disease.20,37,38 However, Barbosa et al further stated that in a restricted group of women with MVA < 1.5 cm2, BMV contributed to a reduction in the incidence of foetal/neonatal complications.20

Thus, though functional class is not, MVA (< 1.5 cm2) is an important predictor of future neonatal complications and it seems sensible to offer this procedure to pregnant women with severe mitral stenosis regardless of their functional class.

In the present series, BMV was offered to all pregnant women, symptomatic in spite of medical line of management, with severe mitral stenosis (MVA < 1.5 cm2, range : 0.6 cm2 - 1.2 cm2) regardless of their functional class (FC : I and II – 24 patients, FC : III and IV – 27 patients). Procedure could be performed in 51 patients as one patient had onset of labour at the beginning of the procedure. It was successful in 50 patients (Success -96%), with average increase in the MVA of 0.9 cm2 and showing symptomatic improvement in 24 hours. The mean increase in the mitral valve area in this study (0.9 cm2) is comparable with Kore et al34(0.9 cm2). Our success rate (96%) is comparable with Karla et al28 (96.2%) and Mishra et al11 (94%). Different studies have reported increase in the MVA from 0.7 cm2 to 1.25 cm2 with success rates of 92 –100 % (Table 5).11,28,34,35

Functional Class improvement was seen by at least one grade as per NYHA. All the cases belonging to FC- III and IV were reverted to FC- I and II, except one. This patient who did not show improvement was a seriously ill patient with critical mitral stenosis and severe pulmonary hypertension at 24 weeks of gestation. She developed pulmonary oedema, deteriorated rapidly in 48 hours and died in spite of all resuscitative measures (maternal mortality – 1.96%). One more patient developed pulmonary oedema but could be revived (2 patients of pulmonary oedema, morbidity - 3.9%). Barbosa et al20 has reported 2 –3 % maternal deaths in untreated pregnant women with severe mitral stenosis. In a smaller series (20 patients), Kore et al34 have reported no maternal death after BMV while our series reports only one (1.96%) maternal death. Thus BMV clearly reduces the maternal mortality by bringing about the functional class improvement.

There was 4% incidence of abortions in our series which is closely comparable with 5% incidence reported by Kore et al.34 38 (79.1%) women in our series delivered vaginally as compared to 90% vaginal deliveries reported by Kore et al34 and 95.6% reported by Fawzy et al.39 Though Kore et al34 and Fawzy et al39 have shown higher vaginal deliveries, Abouzied et al40 have shown less incidence (68.7%) of vaginal deliveries as compared to our series. Out of 38 vaginal deliveries, 8 (21.05%) had prophylactic application of forceps to cut short the second stage of labour. Kore et al34 reported 33% forceps applications to cut short the second stage. In our study, incidence of caesarean deliveries was 20.83%,

Thus, overall Obstetric outcome was significantly improved without any additional risk of the procedure to either the mother or the foetus. Multiple studies have established safety of this procedure when performed after 20 weeks of gestation.21,26,33,34,36 In expert hands BMV is very quick and effective producing consistent symptomatic and haemodynamic improvement.11 Facing these facts and the low incidence of maternal and foetal complications observed when BMV is used during pregnancy,41-46 this procedure should be seriously considered for the treatment of pregnant women with severe mitral stenosis independently of their functional class.

Conclusion
Incidence of rheumatic mitral stenosis in pregnant women continues to be high in India. Balloon Mitral Valvuloplasty (BMV) is a quick, effective and safe method for treating severe mitral stenosis during pregnancy with favourable maternal–foetal outcome and should be offered to all pregnant women with severe mitral stenosis irrespective of their functional class.

Those unfortunate victims of this disease, who have missed the early detection and treatment, still have a ray of hope for safe motherhood in the form of BMV therapy.

Acknowledgement
We are thankful to the Department of Cardiology and Anaesthesiology, Grant Medical College and J J Hospital, for their constant help in the management of the cases and contribution to this study.

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