Paradoxical hypertensive events can complicate the post-operative course after the repair of coarctation of the aorta.
Coarctation of the aorta is a congenital heart defect characterized by narrowing of the lumen of the aorta. It is present in around 4 per 10,000 live births, more commonly in males. Coarctation often occurs in association with Turner’s syndrome, and when the aortic valve has two cusps (bicuspid) rather than the normal three.
The infantile or pre-ductal type of coarctation of the aorta occurs distal to the subclavian artery and proximal to the ductus arteriosus. The ultimate result of the narrowing is that blood flow is decreased distally and increased proximally to the obstruction. Pediatricians should keep this lesion in mind in the differential diagnosis of secondary hypertension in kids, which results from activation of the renin-angiotensin system.
The conventional approach to the treatment of severe manifestations of coarctation is to improve the ventricular function, keep the ductus open by administering prostaglandins (PGE-1), and surgical repair, in the form of stenting (balloon dilatation) or end-to-end anastomosis. Although both approaches are successful in decreasing the coarctation gradient and relieving the symptoms, a large fraction of patients experience paradoxical hypertension after the repair. It is reported to be present in 37% to 100% of the patients undergoing repair for coarctation of aorta.
These potentially fatal hypertensive episodes tend to occur in two distinct periods after the surgery. The first episode, occurring within the first 24 hours, is due to baseline overstimulation of the carotid baroreceptors. After the obstruction of the aorta is removed, there is a decreased stretch on the carotid and aortic baroreceptors which eventually signals an increase in sympathetic activity, resulting in a hypertensive episode. The second or delayed episode of hypertension is induced by inflammation of the arteries arising from the aorta below the coarctation; this phenomenon is mostly seen in adults.
Both types of paradoxical hypertensive events can be thought of as misdirected adaptation mechanisms. Beta blockers, angiotensin converting enzyme inhibitors and vascular smooth muscle relaxants are used to treat these episodes.
Nakagawa TA, Sartori SC, Morris A, Schneider DS. Intravenous nicardipine for treatment of postcoarctectomy hypertension in children. Pediatr Cardiol 2004