The haemodynamic response to pregnancy in patients with left ventricular outflow tract obstruction

Pregnancy exacerbates left ventricular outflow tract (LVOT) gradients due to increased cardiac output (CO). This is amplified in patients with LVOT obstruction (LVOTO). Ascertaining whether gestational elevations in LVOT gradients are transient haemodynamic responses that regress postpartum, or predictors of disease progression or adverse outcomes, is critical.

A retrospective, observational study was conducted between 2009 and 2023 in two tertiary centres. Clinical and echocardiographic data were collected preconception, antenatally, and postpartum. Key measurements included peak and mean LVOT gradients, left ventricular ejection fraction, and aortic valve area. The primary endpoint was the need for postpartum intervention, while the secondary endpoints were a composite of adverse clinical outcomes and postpartum intervention.

A total of 78 women with LVOTO (109 pregnancies) were included. Gestational increases in LVOT gradients were transient, regressing to baseline levels postpartum for most. Postpartum intervention was required in 11% of pregnancies within a median of 6.3 (4.4-9.2) years. Predictors of the primary endpoint were baseline LVOTO severity (HR = 29.6, p < 0.01), antenatal LVOTO severity (HR = 21.1, p < 0.01), and postpartum LVOTO severity (HR = 18.3, p < 0.01). While patients with inherently severe LVOTO at baseline (n = 8, 10%) had a significantly increased risk of postpartum intervention, those with transiently severe LVOTO during pregnancy did not.

Pregnancy causes an increase in LVOT gradients but no significant disease progression warranting either antenatal or postpartum intervention, except in patients who had severe LVOTO preconception. The development of pregnancy-specific echocardiographic thresholds for severity is a critical need to prevent misdiagnoses and optimise maternal outcomes.