unidirectional block

u·ni·di·rec·tion·al block

block that prevents passage of an impulse when it approaches from one direction but not from the other, as when block in the AV node prevents anterograde conduction to the ventricles whereas retrograde conduction to the atria remains intact.

unidirectional block

[-direk′shənəl]
Etymology: L, unus + dirigere, to direct; Fr, bloc
a pathological failure of cardiac impulse conduction in one direction while conduction is possible in the opposite direction.
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