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Valvular heart disease
Original research
Prediction of adverse cardiac events in pregnant women with valvular rheumatic heart disease
  1. Jyoti Baghel1,
  2. Anish Keepanasseril1,
  3. Ajith Ananthakrishna Pillai2,
  4. Nivedita Mondal3,
  5. Yavanasuriya Jeganathan1,
  6. Pankaj Kundra4
  1. 1 Obstetrics & Gynaecology, Jawaharlal Institute of Post-graduate Medical Education and Research (JIPMER), Puducherry, India
  2. 2 Cardiology, Jawaharlal Institute of Post-graduate Medical Education and Research (JIPMER), Puducherry, India
  3. 3 Neonatology, Jawaharlal Institute of Post-graduate Medical Education and Research (JIPMER), Puducherry, India
  4. 4 Anaesthesiology & Critical Care, Jawaharlal Institute of Post-graduate Medical Education and Research (JIPMER), Puducherry, India
  1. Correspondence to Dr Anish Keepanasseril, Obstetrics & Gynecology, Jawaharlal Institute of Post Graduate Medical Education and Research, Puducherry 605006, India; keepan_r{at}yahoo.com

Abstract

Objective To assess the incidence of adverse cardiac events in pregnant women with rheumatic valvular heart disease (RHD) and to derive a clinical risk scoring for predicting it.

Methods This is an observational study involving pregnant women with RHD, attending a tertiary centre in south India. Data regarding obstetric history, medical history, maternal complications and perinatal outcome till discharge were collected. Eight-hundred and twenty pregnancies among 681 women were included in the analysis. Primary outcome was composite adverse cardiac event defined as occurrence of one or more of complications such as death, cardiac arrest, heart failure, cerebrovascular accident from thromboembolism and new-onset arrhythmias.

Results Of the 681 women with RHD, 180 (26.3%) were diagnosed during pregnancy. Composite adverse cardiac outcome during pregnancy/post partum occurred in 122 (14.9%) pregnancies, with 12 of them succumbed to the disease. In multivariate analysis, prior adverse cardiac events (OR=8.35, 95% CI 3.54 to 19.71), cardiac medications at booking (OR=0.53, 95% CI 0.32 to 0.86), mitral stenosis (mild OR=2.48, 95% CI 1.08 to 5.69; moderate OR=2.23, 95% CI 1.19 to 4.18; severe OR=7.72,95% 4.05 to 12.89), valve replacement (OR=2.53, 95% CI 1.28 to 5.02) and pulmonary hypertension (OR=6.90, 3.81 to 12.46) were predictive of composite adverse cardiac events with a good discrimination (area under the curve=0.803) and acceptable calibration. A predictive score combining these factors is proposed for clinical utility.

Conclusion Heart failure remains the most common adverse cardiac event during pregnancy or puerperium. Combining the lesion-specific characteristics and clinical information into a predictive score, which is simple and effective, could be used in routine clinical practice.

  • pregnancy
  • valvular heart disease

https://doi.org/10.1136/heartjnl-2020-316648

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    Introduction

    Even though the global trend of rheumatic valvular heart disease (RHD) and associated complications is showing a downward trend with advances in medicine and use of preventive strategies, it remains a matter of concern especially in low-income to middle-income countries of South Asia and sub-Saharan Africa.1 2 It continues to be a disease of poverty, where lack of awareness, accessibility and affordability to healthcare along with the initial dormant disease poses a challenge to the health systems. Various strategies following millennium development goals has shown a decline in overall rates and the proportion of direct causes contributing to maternal mortality and morbidity.3 4 Cardiac disorders remain as one of the main contributors to indirect causes of mortality and the proportion of these are increasing.3 5

    RHD is the most common acquired cardiac disorder encountered during pregnancy, especially in low-income to middle-income countries.6–9 Physiological changes in pregnancy, especially the circulatory changes can pose a threat to the life of mother and/or fetus in these women.6 10 Women in the low-income to middle-income countries, who often do not receive preconceptional care and lack access/affordability to intervention which may optimise their conditions, may be diagnosed for the first time during pregnancy.6 11 12 Various scoring systems and risk stratification tools are reported in the literature to predict the likelihood of maternal adverse cardiac events during pregnancy and post partum. These risk assessment tools include the modified World Health Organisation (WHO) score, Zwangerschap bij vrouwen met een Aangeboren HARtAfwijking (ZAHARA) score, Cardiac Disease in Pregnancy (CARPREG) I score and CARPREG II score, with all of them formulated from the western cohort with only one-third or less were with acquired valvular disease and most women had access to advanced cardiac care facilities.9 13–16 Since there is high prevalence of RHD in low-income to middle-income countries where the cardiac facilities are mainly limited to regional or tertiary centres, a model to stratify the risk in these women can help optimal utilisation of resources by early referral and management of those at high risk in these centres. The aim of the study was (i) to assess the cardiac complications in pregnant women with RHD and (ii) to derive a clinical risk scoring for the prediction of adverse cardiac events in these women.

    Methods

    This study was conducted on a cohort of pregnant women with RHD admitted to a regional cum tertiary referral cum teaching institute in South India during the time period from January 2011 to December 2018. This hospital provides tertiary care, mainly to the rural population in the south-eastern region of India and has an annual delivery rate of 15 000–16 000 per year. Details of pregnancies complicated with RHD from January 2011 to August 2015 were collected from the records, that is, from the admission register to the labour and antenatal wards and obstetric intensive care unit. Those who attended the hospital from August 2015 to December 2018 were recruited prospectively after taking informed consent.

    Pregnant women with RHD undergoes assessment at booking and then followed serially throughout the pregnancy and till 6 weeks post partum in the hospital. Evaluation of these women will be done periodically by the treating obstetric team under a consultant (not later than every 2 weeks till 32 weeks and then weekly till admission/delivery) and by cardiology team (seen once a month or earlier based on cardiac status). Grading of the valvular heart disease was based on the European Association of Echocardiography and American Society of Echocardiography recommendations.17 18 As per the hospital policy, all women with cardiac disorders following delivery are observed for 72 hours post partum and discharged after a review by cardiology team.

    Details of the clinical history, examination and investigation including the echocardiography reports at time of first visit to hospital were collected. This included maternal age, parity, cardiac lesion, prior cardiac intervention, New York Heart Association (NYHA) functional class, history of any adverse cardiac events such as heart failure, arrythmia, infective endocarditis and thromboembolic events and also the medication received. Obstetric details including the development of pregnancy-specific complications, labour and delivery details, fetal/neonatal outcomes were also collected. Fetal and neonatal outcomes studied included the rates of stillbirth, fetal growth restriction, low birth weight, admission to neonatal intensive care unit and neonatal death. Details of any complications till the time of discharge from the hospital were noted and data entry was done using predesigned proforma created in the REDCap database. Adverse cardiac events occurring during antepartum, labour and delivery or post partum till discharge from the hospital were noted and verified with the members of the research team.

    Primary outcome was the occurrence of composite adverse cardiac events, defined as the occurrence of one or more of cardiac complications such as cardiac death, cardiac arrest, heart failure defined as a clinical symptoms of acute onset dyspnoea with signs of fluid retention (crepitations in lung bases and oedema), left-sided heart failure defined as pulmonary oedema, cerebrovascular accident such as stroke or transient ischaemic attack from thromboembolism (diagnosed by clinical examination and neuroimaging) and new-onset arrhythmias such as atrial fibrillation requiring treatment.19 20 Secondary outcomes included decline in ≥2 NYHA functional classes and need for emergency invasive cardiac interventions.

    .

    Statistical analysis

    Statistical testing was performed using STATA software V.13.1 (StataCorp, Texas, USA). Categorical variables are presented as percentage and continuous variables as mean with SD or median and range depending on their distribution. Univariate analysis was done using Student’s t-test and χ2 test as appropriate. Given that each woman could have >1 pregnancy, analyses took into consideration the non-independent nature of the data structure. Generalised estimating equations were used to produce regression models to account for the clustering occurring due to this. Multivariate predictors of cardiovascular events were assessed using generalised estimating equation regression models. Probability value of 0.05 was considered to be statistically significant.

    To reduce the overfit of the created model, internal validation was performed with bootstrapping. We bootstrapped 500 times. In each of these 500 new data sets, the same multivariate logistic regression was assessed. By analysing the difference among the predictive models, a shrinkage factor was calculated. The model was corrected by this shrinkage factor, and the prediction formula was extracted from the data.

    To evaluate the discriminative performance of the model, the area under the receiver operating characteristic (ROC) curve was calculated. The results of the multivariate model were converted into a point-based risk score. Sensitivity and specificity of the model was calculated from the derived model. To assess the agreement between the predicted and observed outcomes, calibration of the model was assessed. The reliability of the model was estimated with Hosmer-Lemeshow test for goodness of fit.

    Results

    Among the 117 613 deliveries during the 8-year study period, cardiac disorders complicated 1407 (1.2%) pregnancies and 842 (0.7%) pregnancies among them were complicated with RHD. After excluding 22 pregnancies (age <18 years (n=3) and those pregnancies whose records were not traceable (n=19)), 820 (58.3%) pregnancies among 681 women diagnosed with RHD were finally included in the analysis. Of the 681 women with RHD, 180 (26.3%) were diagnosed during pregnancy and the mean age at diagnosis was 18.5 years. Baseline characteristics in the study population is shown in table 1. Mitral regurgitation (MR) was the most common type of lesion (n=548, 80.5%), followed by mitral stenosis (MS) in 57.0% (n=388) with severe MS in 146 women (37.6%) (table 2). Two hundred and ninety-six women had either isolated MS (n=84) or MR (n=212). Multivalvular or combination of stenosis with regurgitation lesions were observed in 287 cases (42.1%). Among those with combination of lesions involved, majority had MS with MR (75/287, 26.1%) followed by mitral stenosis and regurgitation with tricuspid regurgitation (13/287, 4.5%). Nearly one-fifth (19.9%, n=136/681) of the pregnant women with valvular heart disease underwent cardiac intervention either before or during the pregnancy, with majority (81.6%) performed in prepregnancy period. One hundred thirteen women underwent balloon mitral valvotomy, among which 37 were done in late second/early third trimester (24–34 weeks).

    View this table:
    Table 1

    Baseline characteristics in the study population

    View this table:
    Table 2

    The distribution of cardiac lesions

    One or more composite cardiac outcome during pregnancy/post partum occurred in 122 (14.9%) pregnancies. Among those who had either heart failure or pulmonary oedema, majority (69.0%) had it in the antenatal period. There were total 12 (1.8%) maternal deaths during the study period, most were due to pulmonary oedema in women with severe MS (online supplementary table S1). There were two deaths following prosthetic valve thrombosis in first trimester, when the patient herself stopped the anticoagulants due to fear of teratogenic effects to the anticoagulants.

    Supplemental material

    Univariate analysis and the crude ORs assessing predictors of composite adverse cardiac outcome during pregnancy is shown table 3. Using stepwise backward logistic regression analysis, prior adverse cardiac events, taking cardiac medications at the booking visit, MS, valve replacement and pulmonary hypertension were found to be predictive of composite adverse cardiac events in pregnant women with RHD (figure 1). Area under the ROC curve, as shown in figure 2 is 0.803 (95% CI 0.756 to 0.850), which indicates good discriminative performance of the model to distinguish those who develop composite adverse cardiac outcomes from those who will not develop it. Comparison of predicted probability and observed rates of composite adverse cardiac outcome using the plot (figure 2B) suggested that the predictions by the model does not significantly deviate from the observed rates (p=0.992). Goodness-of-fit test confirmed this analysis, suggesting a good overall performance of this model (Hosmer-Lemeshow χ2 statistics=5.40, p=0.494).

    Figure 2
    Figure 2

    (A) Receiver operating characteristics graph showing the area under the curve of the final model; (B) calibration plot showing the relation with the predicted and observed outcome.

    View this table:
    Table 3

    The univariate analysis and the crude ORs assessing predictors of composite adverse cardiac outcome during pregnancy

    Figure 1
    Figure 1

    The frequency of adverse cardiac outcome.

    Internal validation by bootstrapping, to check the predictive accuracy for overoptimism, yielded an overoptimism in area under the curve (AUC) of the original model of 0.022. Subtracting this, an optimism-adjusted discrimination of the final model was 0.781, indicating a possible overfit up to 2.82% in an external population. Thus, the shrinkage factor obtained from bootstrap results was 0.972.

    Chance of one of the composite adverse cardiac outcomes to occur in a pregnant woman with RHD can be derived from the multivariable model using the formula (adjusted for shrinkage factor):

    Embedded Image

    Where y=[0.972×(−2.871+(2.12×prior adverse cardiac event)−(0.640×use of cardiac medications at booking)+(0.930×valve replacement)+(1.958×pulmonary hypertension)+(0.907×mild MS)+(0.803×moderate MS)+(1.978×severe MS))]. Where each variable is given 1 if present (yes) and 0 if absent (no). For designing a scoring system, which could be used in clinical practice, weighted value was assigned to each variable based on the coefficient obtained in the model as shown in table 4. Using a cut-off of 20% probability for adverse cardiac outcome, with a false positive rate of 12.2%, the model predicted 83.8% of outcomes correctly; with a specificity of 87.8% and sensitivity of 60.7%. The positive predictive value was 46.5% and a negative predictive value of 92.7%.

    View this table:
    Table 4

    New prognostic score (DEVI’s score) to predict composite adverse cardiac outcome in pregnant women with rheumatic valvular heart disease

    For example, for a pregnant woman with previous cardiovascular event (pulmonary oedema) (score: +4) having severe mitral stenosis (score: +4) and pulmonary hypertension (score: +4), taking cardiac medications (score: −1), DEVI’s score will be 11.

    Among 820 pregnancies complicated with RHD, 17 (2.1%) underwent medical termination of pregnancy in view of heart disease and 34 (4.2%) women had spontaneous abortions. Among the 769 pregnancies which crossed 20 weeks of gestation, 363 (47.2%) were hospitalised at least once before 37 weeks because of either cardiac/obstetric complication. Obstetric complications, labour and delivery details are shown in table 5. Preterm birth complicated 158 (20.6%) pregnancies; including spontaneous preterm birth in 78 pregnancies. Epidural labour analgesia was given in 39 cases during the study period. Fetal distress was the most common indication for caesarean section. Six women underwent caesarean for cardiac reason; four along with concurrent mitral valve replacement (in view of severe MS with moderate to severe MR) and two for active labour on warfarin therapy.

    View this table:
    Table 5

    The obstetric complications, delivery details and pregnancy/neonatal outcome

    Discussion

    Main findings

    Composite adverse cardiac outcomes occurred in (14.9%) pregnancies among women with RHD. A model comprising prior adverse cardiac events, taking cardiac medications at the booking visit, mitral stenosis, mechanical valve replacement and presence of pulmonary hypertension was found to predict the composite adverse cardiac events during pregnancy and immediate post partum in these women, with a good precision (AUC=0.803). Internal validation done by boot strapping suggested good performance of this predictive model. Combining these factors into a predictive score, which is simple and effective, could be used in routine clinical practice.

    Strengths and limitations

    This was a single-centre study from a low-resource setting, catering to the rural population belonging to the lower socioeconomic strata in whom the prevalence of RHD is high, over a period of 8 years. Since it was a large population with RHD alone, it helped to identify clinical and lesion-specific characteristics associated with adverse cardiac outcome which could be easily recognised and used clinically. As the physiological changes in the first trimester such as increase in heart rate and cardiac output increases the risk of maternal decompensation in lesions such as MS, unlike previous reports, pregnancies terminating at <20 weeks were also included.9 14 15 Performance of internal validation with boot strapping, derivation of the final regression equation corrected for the possible overfitting, assessment of calibration and discrimination yield good performance (even after correcting the overfitting) could be considered as strength of the study. Since it was a concurrent cohort, inability to retrieve data not documented in the medical records such as body mass index and use of tobacco products, resulted in inability to assess the importance of these factors. A lower frequency of women with factors such as NYHA functional class III/IV at conception, precluded its assessment as a risk factor, as shown in the earlier studies.14 15

    Interpretations

    Various initiatives following the Millennium Development Goals 5 resulted in higher proportion of women receiving antenatal care and delivery with skilled heathcare personnel/institutions; even in low-income to middle-income countries.1 21–23 This lead to identification of high-risk factors which aided in unmasking/detecting underlying disorders, those otherwise would have presented with complications during pregnancy. Nearly one-fourth of cases (26.3%) were diagnosed during pregnancy, as similar to the earlier reports.19 24 Since access to the healthcare varies in these low-income to middle-income countries, depending on the socioeconomic status and the limited availability of specialist services, a criterion for early referral can provide a window of opportunity for optimisation of maternal condition.22

    Haemodynamic changes in pregnancy and puerperium, such as increase in heart rate, cardiac output and changes in blood pressure, with pregnancy being a procoagulant state, increase the risk of various cardiac complications in these time period. Incidence of adverse cardiac events were 15% and was similar to the rates noted in CARPREG I and CARPREG II, both of which included a heterogenous population of all cardiac lesion complicating pregnancy.9 14 However, these rates were much lower compared with the ROPAC study on mitral valve disease in pregnancy, which reported 26.7% with heart failure and arrythmia in 5% pregnancies.19 However, in those with RHD, heart failure either left sided or congestive cardiac failure predominates as the complication even in the CARPREG score reports similar to that observed in the index study and as reported from results of ROPAC registry.9 14 19 24 Higher preterm birth and the lower overall caesarean section rates were observed compared with the ROPAC study which may be explained by the various practices of induction of labour and wide difference in the institutional polices for intrapartum caesarean section.

    RHD is a disease of poor/low socioeconomic groups, whose main concern is affordability (medication/intervention such as balloon procedure/valve replacement) and accessibility of specialist services limited to regional tertiary centres. In addition, adolescent girls/women in such societies also have to overcome the cultural constraints, so they tend to seek intervention at an advanced stage of the disease that can affect the outcome of even definitive treatment such as valve replacement and subsequent pregnancy outcomes, which need to be assessed in future studies.25 26

    Prior adverse cardiac events, as reported in the previous studies, were found to be an important predictor of composite adverse event during pregnancy and puerperium. Initial CARPREG index score did not include the lesion-specific characteristics; however in the subsequent version (CARPREG II), it was included along with general factors associated with adverse cardiac events.9 14 In the present study, a model involving lesion-specific characteristics such as presence of mitral stenosis, pulmonary hypertension, mechanical heart valve combined with general characteristics such as history of cardiac intervention and prior cardiac medication was found to predict the adverse cardiac events. Higher score in the weighted score, for prior adverse cardiac events, presence of severe mitral stenosis and pulmonary hypertension, signifies the importance of a meticulous cardiovascular assessment at booking for stratifying the risk. This may enable early referral to appropriate levels of care for optimising the maternal and fetal outcome and also aid in better utilisation of available resources. As the proposed scoring is based on a setting of variable access to the advanced cardiac care/expert maternity team, the score may perform well in centres with universal access to maternal fetal medicine specialist services and state-of-the-art cardiac facilities. An external validation in a different group of women is currently initiated, so as to access the usefulness and ascertain the generalisability of the proposed score in routine clinical practice.

    Conclusions

    RHD remains the most common cardiac lesion which complicates pregnancies and can lead to maternal mortality and morbidity. Heart failure remains the most common adverse cardiac event, with MS noted to have higher risk than the regurgitant lesions, during pregnancy or puerperium. Proposed risk score, comprising lesion-specific characteristics and clinical information, could be calculated following a careful cardiovascular clinical assessment. Once externally validated, this could aid in early identification and timely referral to higher centres of pregnant women with RHD at risk of adverse cardiac events, especially in low-income to middle-income countries with limited resources.

    Key messages

    What is already known on this subject?

    • Various risk assessment/stratification tools available currently to predict the likelihood of maternal adverse cardiac events during pregnancy and post partum are formulated from the western cohort, with better access to advanced cardiac care facilities and with only one-third or less with rheumatic valvular heart disease (RHD).

    • RHD remains the most common acquired cardiac disorder, especially in low-income to middle-income countries, encountered during pregnancy.

    What might this study add?

    • Composite adverse cardiac outcomes were observed in (14.9%) pregnancies among women with RHD.

    • A model comprising prior adverse cardiac events, taking cardiac medications at the booking visit, mitral stenosis, mechanical valve replacement and presence of pulmonary hypertension was found to predict the composite adverse cardiac events during pregnancy and immediate post partum in these women, with a good precision (area under the curve=0.803).

    • Combining these factors from the model to a predictive score is proposed for clinical utility.

    How might this impact on clinical practice?

    • High prevalence of RHD in low-income to middle-income countries where the cardiac facilities are mainly limited to regional or tertiary centres, a model to stratify the risk in these women can help optimal utilisation of resources by early referral and management of those at high risk in these centres.

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    Footnotes

    • Contributors AK and AAP conceived the study. All authors contributed to the design. JB and YJ carried out the data collection and guarantees data integrity. AK performed statistical analyses. AAP, NM and PK reviewed the analysis and AK and JB wrote the first draft. All authors contributed to revising and finalisation of the manuscript. AK (corresponding author) guarantees all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

    • Patient and public involvement Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.

    • Patient consent for publication Not required.

    • Ethics approval This study was done as per the ethical standards set by the Institute Scientific Advisory and Ethical committee (Human Studies), in accordance with the 1964 Helsinki Declaration and its later amendments. Protocol of the study and waiver of consent for the collection of the details of the women from the records from 2011 to 2015 was approved by the Institute Ethics Committee (Human studies). Informed consent was obtained from women who were prospectively enrolled (approval number: JIP/IEC/2016/1079).

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement Data are available on reasonable request to the corresponding author.

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