Factors associated with the change in prevalence of cardiomyopathy at delivery in the period 2000-2009: a population-based prevalence study

Abstract

Objective: Cardiomyopathy (CM) at delivery is increasing in prevalance. The objective of this study was to determine which medical conditions are attributable to this increasing prevalance.

Design: Population prevalence study from 2000 to 2009.

Setting: The Nationwide Inpatient Sample (NIS).

Sample: Pregnant women admitted for delivery were identified in the NIS for the years 2000-2009.

Methods: Temporal trends in pre-existing medical conditions and in medical and obstetric complications at delivery admissions were determined by linear regression. The change in the prevalence of CM among all pregnant women was compared with the change in the prevalance of CM among pregnant women without pre-existing conditions or complications.

Main outcome measure: Prevalence of CM.

Results: The prevalence of CM increased from 0.25 per 1000 deliveries in 2000 to 0.43 per 1000 deliveries in 2009 (P < 0.0001). Women with chronic hypertension had increased odds of developing CM compared with women without chronic hypertension (odds ratio, OR, 13.2; 95% confidence interval, 95% CI, 12.5-13.7). The linear increase in chronic hypertension over the 10-year period was the single identified pre-existing medical condition that explained the increasing prevalence of CM at delivery (P = 0.005 for the differences in slopes for linear trends).

Conclusions: Pregnant women with chronic hypertenion are at an increased risk for CM at delivery, and the increasing prevalence of chronic hypertension is an important factor associated with the increasing prevalence of CM at the time of delivery. Among women without chronic hypertension, the prevalence of CM at delivery did not change during the time period.

Keywords: Cardiomyopathy; hypertension; mortality; nationwide inpatient sample; pregnancy.

Figure 1. Trends in the prevalence of cardiomyopathy, chronic hypertension, preeclampsia, and chronic hypertension with preeclampsia at delivery admissions, the 2000 – 2009 Nationwide Inpatient Sample (n = 43,226,239)

Error bars demonstrate 95% confidence intervals. A. There was an increase in the linear trend for cardiomyopathy diagnosed at delivery admissions during the 10-year study period (p<0.001, R²=0.90), increasing from 0.25 cases per 1000 deliveries in 2000 to 0.43 per 1000 deliveries in 2009. B and C. There was an increase in the linear trend for chronic hypertension (B. p<0.001, R²=0.99) and preeclampsia (C. p<0.001, R²=0.90), increasing from 10.1 per 1000 deliveries in 2000 to 19.6 per 1000 deliveries in 2009, and from 62.5 per 1000 deliveries in 2000 to 74.0 per 1000 deliveries in 2009, respectively. D. There was an increase in the linear trend for chronic hypertension with preeclampsia (D. p<0.001, R²=0.84), increasing from 1.8 per 1000 deliveries in 2000 to 4.7 per 1000 deliveries in 2009.

Figure 2. Trends in the prevalence of cardiomyopathy in women without hypertensive disorders of pregnancy compared to all women with cardiomyopathy at delivery admissions, the 2000 – 2009 Nationwide Inpatient Sample (n=43,226,239)

Error bars demonstrate 95% confidence intervals. To determine if pre-existing medical conditions or medical and obstetric complications occurring during a delivery admission were accounting for the increased prevalence of cardiomyopathy over the study period, the linear trend for cardiomyopathy among women who also did not have each of the preexisting medical conditions or medical and obstetrics complications listed (Tables 2 and 3) were compared to the linear trend for all women with cardiomyopathy. A. The difference in the slopes for the linear trends of all women with cardiomyopathy compared to women with cardiomyopathy who did not have chronic hypertension were significantly different (p=0.005), suggesting that chronic hypertension was contributing to the increasing prevalence of cardiomyopathy during the study time period. B. and C. In contrast, there were no differences in the slope for linear trend among all women with cardiomyopathy compared to women with cardiomyopathy who did not have preeclampsia (B) or compared to women with cardiomyopathy who did not have both chronic hypertension and preeclampsia (C). (Abbreviations: CM=cardiomyopathy, HTN=hypertension, Prex=preeclampsia)