Unmasking the borderline coarctation: the utility of isoproterenol in the paediatric cardiac catheterisation laboratory

Background: One indication for intervention in coarctation of the aorta is a peak-to-peak gradient >20 mmHg. Gradients may be masked in patients under general anaesthesia and may be higher during exercise. Isoproterenol was given during cardiac catheterisation to simulate a more active physiologic state. Objectives: We aimed to describe the haemodynamic effects of isoproterenol in patients with coarctation and the impact of intervention on the elicited gradients. Methods: A retrospective study was performed on two-ventricle patients who underwent cardiac catheterisation for coarctation with isoproterenol testing. Results: 25 patients received isoproterenol before and after intervention. With isoproterenol, the mean diastolic (p = 0.0015) and mean arterial (p = 0.0065) blood pressures proximal to the coarctation decreased significantly. The mean systolic, diastolic, and mean arterial blood pressures distal to the coarctation decreased significantly (p < 0.0001). In patients with a baseline gradient <= 20 mmHg (n= 17) at catheterisation, the median gradient increased from 10 (0-20) to 30 (15-50) mmHg (p <0.0001) with isoproterenol. Of these, 15 patients developed a gradient >20 mmHg. Post intervention, the median gradient decreased to 2 (0-29) mmHg, versus baseline, p = 0.005, and with isoproterenol it decreased to 8 (0-27)mmHg, versus pre-intervention isoproterenol, p <0.0001. There were significant improvements in the gradients by Doppler (<0.0001) and by blood pressure cuff (p = 0.0313). The gradients on isoproterenol best correlated with gradients by blood pressure cuff in the awake state (R-2 = 0.76, p <0.0001). Conclusions: Isoproterenol can be a useful tool to assess the significance of a coarctation and the effectiveness of an intervention. Percutaneous interventions can effectively reduce the gradients elicited by isoproterenol.