Internal Medicine

P1: SBT

0521779407-05 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 20:49

Atrioventricular Block 199

■Degenerative: Lenegre disease, Lev disease

■Infection: rheumatic fever, myocarditis, Lyme borreliosis, Chagas

disease and endocarditis

■Immune/inflammatory processes: ankylosing spondylitis, rheuma-

toid arthritis, scleroderma and Reiter disease

■Infiltrative processes: amyloidosis, sarcoidosis

■Iatrogenic: medications: digoxin, beta and calcium channel blockers,

Class I and III antiarrhythmic drugs. Post-heart surgery (CABG and

aortic valve replacement).

■AV Wenckebach second-degree block

➣Progressive increase in the A-C venous pulse interval before the

non-conducted P wave

➣Progressive decrease in the intensity of the first heart sound

■AV dissociation

➣Intermittent cannon A wave in the venous pulse and variable

intensity of the first heart sound

Signs & Symptoms

■Rarely symptomatic in first-degree AV block or Type I second-degree

(Wenckebach) AV block

■High-degree AV block:

➣Transient dizziness, lightheadedness, near-syncope or syncope,

fatigue, worsening of congestive heart failure

tests

■Basic Tests

➣12-lead ECG:

➣First-degree AV block: PR interval > 0.21 sec

➣Second degree AV block:

➣Type I AV block (Mobitz I or Wenckebach AV block):

Regular sinus P-P intervals

Progressive prolongation of PR intervals (but with decreasing

increment) before non-conduction of P wave occurs

Progressive decrease in R-R intervals; the longest R-R interval

(pause) is shorter than 2 times the shortest R-R interval. QRS

occurs in groups.

➣Atypical AV Wenckebach: several unchanged PR intervals or

irregular change in PR intervals

➣Type II AV block (Mobitz II AV block): Constant regular sinus P-P

intervals and R-R intervals before the AV block