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  • Title: [Circulatory failure in children with left-to-right shunt in the framework of congenital heart defects: pathophysiology and therapeutic results].
    Author: Wessel A, Buchhorn R, Bürsch J.
    Journal: Klin Padiatr; 2000; 212(2):53-9. PubMed ID: 10812553.
    Abstract:
    In children with large left-to-right shunts secondary to congenital heart defects the imbalance between the pulmonary and systemic perfusion may lead to circulatory congestion with clinical signs similar to those of heart failure. The circulatory function in this state was evaluated by using the invasive measurements performed during cardiac catheterisations in n = 64 young patients with ventricular septal defect (n = 56) or complete atrioventricular septal defect (n = 8) aging 0.1-23.7 years (median 1.1 years). The mean shunt ratio was Qp/Qs = 2.4 (range 1-8). With increasing shunt ratio the pulmonary perfusion raised (r = 0.84), but the systemic output dropped significantly (r = -0.77) while the total cardiac output (Qp + Qs) increased slightly not exceeding 141/min/m2. In infants, the systemic hypoperfusion affects the hemoglobin content: Hb = 14.9-1.01 x Qs, r = 0.63, p < 0.01. This may be due to the diminished oxygen extraction reserve of 46%. With dropping systemic output, the vascular resistance increases and the mean aortic pressure (MAP) remains normal. The actual pressure values layed near to the curve of the normal aortic pressure calculated as MAP = Qs x Rs. This pressure-flow-resistance diagram was used to interpret the effects of vasodilators established by 7 studies: ACE-Inhibitors, Hydralazine, and Na-Nitroprusside reduce the vascular resistance effectively but induce hypotension, because the systemic output fails to increase. In the chronic circulatory congestion secondary to a large intracardiac left-to-right shunt the pulmonary perfusion increases with the shunt ratio but the systemic output decreases and the total cardiac output is limited to a maximum of 141/min/m2. In this state vasodilators cause systemic hypotension thus offering no acceptable therapeutic option.
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