Cardiac Structure and Function in Morbidly Obese Parturients: An Echocardiographic Study

METHODS: This prospective cross-sectional study was performed in 2 referral maternity units in Cape Town, South Africa, over a 3-month period. Forty morbidly obese pregnant women of BMI ≥40 kg·m⁻² (group O) were compared to 45 pregnant women of BMI ≤30 kg·m⁻² (group N). Cardiac structure and function were assessed by transthoracic echocardiography, according to the recommendations of the British Society of Echocardiography. The 2-sample t-test with unequal variances was used for the comparison of the mean values between the groups.

RESULTS: Acceptable echocardiographic images were obtained in all obese women. Statistical significance was defined as P < .0225 after applying the Benjamini–Hochberg correction for multiple testing. Mean (standard deviation) mean arterial pressure was higher in group O (91 [8.42] vs 84 [9.49] mm Hg, P < .001). There were no between-group differences in heart rate, stroke volume, or cardiac index (84 [12] vs 79 [13] beats·minute⁻¹, P = .103; 64.4 [9.7] vs 59.5 [13.5] mL, P = .069; 2551 [474] vs 2729 [623] mL·minute⁻¹·m⁻², P = .156, for groups O and N, respectively). Stroke volume index was lower, and left ventricular mass was higher in group O (30.14 [4.51] vs 34.25 [7.00] mL·m⁻², P = .003; 152 [24] vs 115 [29] g, P < .001). S′ septal was lower in group O (8.43 [1.20] vs 9.25 [1.64] cm·second⁻¹, P = .012). Considering diastolic function, isovolumetric relaxation time was significantly prolonged in group O (73 [15] vs 61 [15] milliseconds, P < .001). The septal tissue Doppler index E′ septal was lower in group O (9.08 [1.69] vs 11.28 [3.18], P < .001). There were no between-group differences in E′ average (10.7 [2.3] vs 12.0 [2.7], P = .018, O versus N) or E/E′ average (7.85 [1.77] vs 7.27 [1.68], P = .137, O versus N). Right ventricular E′/A′ was lower in group O (1.07 [0.47] vs 1.29 [0.32], P = .016).

CONCLUSIONS: Cardiac index did not differ between obese pregnant women and those with normal BMI. Their increased left ventricular mass and lower stroke volume index could indicate a limited adaptive reserve. Obese women had minor decreases in septal left ventricular tissue Doppler velocity, but the E/E′ average values did not suggest clinically significant diastolic dysfunction.