NBME Step 2 CK Form 8 Second-degree atrioventricular block (NBME Answers)

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Rhythm strip shows progressively prolonged PR interval until a QRS complex is dropped
First-degree AV block = Prolonged PR interval (>200 ms or one big box) but every p wave is followed by a QRS
Second-degree type 1 block = PR interval becomes increasingly prolonged until a QRS complex is dropped (p wave not followed by QRS)
Second-degree type 2 block = PR interval prolonged with random QRS complexes that are dropped
Third-degree block = Atria and ventricles beat independently of one another, with QRS complexes occurring at rates ~40 beats/min and p waves occurring at rates ~80 beats/min

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kingfriday aye OME and UW say that type 2 AV block have normal PR interval but the QRS drops randomly Mobitz Type I - due to delay or break of cardiac electrical signal pathway from atria to ventricles - epidemiology: associated with drugs that block the AV nodes (digioxin, CCB, BB) Benign rhythm -> low risk for complete heart block thus treatment is observation in an asymptomatic pt and attempt to correct reversible causes (holding meds that would impact the AV node) Mobitz type II due to his-purkinje system below AV node - can progress to third degree AV block which requires a pacemaker - QRS in type II can be wider than Mobitz Type I +