Impact of Pre-Existing Ischemic Heart Disease on Severe Maternal Morbidity and Mortality During Delivery Hospitalizations

Abstract

Background: The impact of pre-existing ischemic heart disease (IHD) on pregnancy is incompletely described.

Objectives: The purpose of this study was to compare adverse pregnancy outcomes between those with IHD and those with a cardiac diagnosis categorized by the modified World Health Organization classification and those without a cardiac diagnosis.

Methods: This retrospective study used the 2015 to 2018 Nationwide Readmissions Database. Delivery hospitalizations, comorbidities, and outcomes were identified using diagnosis and procedure codes. The exposure was isolated IHD. The primary outcome was severe maternal morbidity (SMM) or death during the delivery hospitalization, analyzed using adjusted relative risk (aRR) regression and weighted to account for the Nationwide Readmissions Database's complex survey methods.

Results: Of 11,556,136 delivery hospitalizations, 65,331 had another cardiac diagnosis, and 3,009 had IHD alone. Patients with IHD were older and had higher rates of diabetes and hypertension. In unadjusted analyses, adverse outcomes were more common among patients with IHD alone than among patients with no cardiac disease and modified World Health Organization class I-II disease. After adjustment, patients with IHD alone were associated with a higher risk of SMM or death (aRR: 1.51; 95% CI: 1.19-1.92) than those without a cardiac disease. In comparison, the aRR was 1.90 (95% CI: 1.76-2.06) for WHO class I-II diseases and 5.87 (95% CI: 5.49-6.27) for WHO II/III-IV diseases. Nontransfusion SMM or death (aRR: 1.60; 95% CI: 1.11-2.30) and cardiac SMM or death (aRR: 2.98; 95% CI: 1.75-5.08) were also higher for those with IHD.

Conclusions: Isolated IHD in pregnancy is associated with worse outcomes than no cardiac disease during delivery hospitalization and approximates the risk associated with WHO I-II diagnoses.

Keywords: coronary artery disease; ischemic heart disease; maternal mortality; modified World Health Organization classification; severe maternal morbidity.

Graphical abstract

Figure 1

Subject Inclusion Flow Chart Delivery hospitalizations captured in the Nationwide Readmissions Database (NRD) from October 2015 to December 2018 were included in this study. A total of 6,109,133 delivery hospitalizations are included in the database. The sample was weighted as recommended by the data vendor to create a sample representative of the entire United States, including states not included in the NRD, yielding a total sample size of 11,556,136. Of the delivery hospitalizations, there were 65,331 with cardiac disease, of whom, 3,009 had pre-existing ischemic heart disease. IHD = ischemic heart disease; mWHO = modified World Health Organization Classification of Maternal Cardiovascular Risk.

Figure 2

Bar Plot of Unadjusted Probability of Primary and Secondary Outcomes Bar plot demonstrating unadjusted probabilities of subjects with no cardiac disease, mWHO I-II cardiac disease, mWHO II/III-IV cardiac disease, and pre-existing ischemic heart disease (IHD only) experiencing severe maternal morbidity and death, nontransfusion severe maternal morbidity and death, cardiac severe maternal morbidity and death, or preterm birth. The unadjusted probabilities of the primary and secondary outcomes were significantly higher for IHD only compared to no cardiac disease. IHD = ischemic heart disease; mWHO = modified World Health Organization Classification of Maternal Cardiovascular Risk.

Central Illustration

Pregnancy in the Setting of Pre-existing Ischemic Heart Disease May Be Considered Safe But Is Not Without Risk Pre-existing IHD is associated with worse outcomes at the time of delivery than no cardiac diagnosis. This risk approximates that of a patient with other low-risk cardiac diagnoses classified as either mWHO class I or II. Pregnancy in the setting of pre-existing ischemic heart disease is likely safe, but patients should be counseled that pregnancy is not without risk entirely. Forest plot of adjusted relative risk for severe maternal morbidity (SMM) and death, nontransfusion SMM and death, cardiac SMM and death, and preterm birth for those with IHD only, mWHO class I-II cardiac disease, and mWHO class II/III-IV cardiac disease compared to no cardiac disease. The adjusted relative risk of SMM and death, nontransfusion SMM and death, and cardiac SMM and death were significantly higher for those with IHD only than for those with no cardiac disease and most closely approximates the risk posed by lesions included in mWHO class I-II. mWHO = modified World Health Organization Classification of Maternal Cardiovascular Risk.