1️⃣st degree: PR constant 👉Look for 1:1 P:QRS ratio 👉PR >0.20 sec (25mm/sec) 2️⃣nd degree type I (Mobitz I): PR variable 👉Look for a progressive lengthening of the PR interval preceding dropped QRS 👉Expect PR to reset following dropped QRS 2️⃣ nd degree type Il (Mobitz lI): PR constant 👉Look for constant PR interval preceding dropped QRS *(2:1 AV block = not likely enough information to determine type I vs type ll) 3️⃣rd degree: PR variable (not a true PR) 👉Look for a variable and constant