[Second-degree atrioventricular block in a patient with coexistant intermittent preexcitation syndrome that masks the electrocardiographic features of past myocardial infarction - diagnostic difficulties and management].

We describe a case of a 60 year-old man after inferior wall myocardial infarction with intermittent preexcitation syndrome. In ECG, the pathologic Q waves in the inferior leads were masked by the intermittent preexcitation. In this patient, paroxysmal asymptomatic second-degree atrioventicular block coexists with inconstant atrioventricular conduction maintained by the accessory pathway, periodically 2:1.