second degree atrioventricular block high degree atrioventricular block 2026-07-20T13:00:23Z 2nd degree, high-grade AV block High-grade AV block may result from either Mobitz I or Mobitz II AV block. High-grade AV block and Mobitz II are considered pathological and frequently progress to a complete (third-degree) heart block. high-degree atrioventricular block high-degree AV block an advanced form of second-degree atrioventricular (AV) block characterized by the presence of 2 or more consecutive, non-conducted P waves occurring at a constant physiologic rate, along with evidence of AV conduction; the P-to-QRS ratio is 3:1 or greater, producing an extremely slow ventricular rate MP:0031759 MPheno.ontology