title: Atypical Wenckebach block and concealed conduction.
abstract: Following exercise testing, a 71-year-old man developed atrial tachycardia with a unusual form of conduction disturbance: 4:2 atrioventricular (A-V) block. This pattern of A-V block is explainable by two different mechanisms of concealed conduction: two different levels of block in the A-V nodal region and dual A-V nodal pathways with concealed retrograde conduction of P waves. These concepts can also explain a variety of other unusual conduction disturbances.
mesh_terms: D000368:Aged; D000787:Angina Pectoris / Q000150:complications; D001283:Atrioventricular Node / Q000503:physiopathology*; D005080:Exercise Test / Q000009:adverse effects; D006327:Heart Block / Q000209:etiology* / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male