Congenital atrioventricular block in right atrial isomerism (asplenia). A case due to atrionodal discontinuity.

The association of complex congenital heart disease with asplenia syndrome and congenital AV block is described in a newborn. Cardiovascular lesions were right atrial isomerism, d-loop, discordant ventriculoarterial connection, pulmonary stenosis, total anomalous pulmonary venous drainage, absent right pulmonary artery, and bilateral superior vena cava. The ECG recording disclosed complete AV block with narrow QRS (suprahisian block). The histology of the conduction system revealed two AV nodes, one anterior and one posterior, none of which connected with the atrial myocardium; only the posterior node was continuous with a penetrating and bifurcating bundle. The histologic findings were consistent with the suprahisian AV block due to lack of connection between the atria and the regular posterior AV specialized junction.