Download Morning Report 7/31/07

3rd Degree AV block
Jason Haag
Heart Block
 1st Degree AV Block
 one-to-one relationship exists between P waves and QRS
complexes, but the PR interval is longer than 200 ms
Heart Block
 2nd Degree Mobitz Type I AV Block (Wenckebach)
 PR interval is prolonging with each P wave to the point
when the P wave is no longer conducted
Heart Block
 2nd Degree Mobitz Type II AV Block
 PR interval is constant, but occasionally P waves are not
followed by the QRS complexes
Heart Block
 3rd Degree Heart Block
 More P waves than the QRS complexes exist and no
relationship exists between them
rd
3
Degree Heart Block
 Block can be in AV node or infranodal conduction
system
 AV node

2/3 escape rhythms have narrow QRS (junctional)
 Fascicular or bundle branches

Wide QRS (subjunctional)
 Rate typically in low 40s
Frequency
 In the US: 0.02%
 Internationally: 0.04%.
 Age: Bimodal peak, at infancy given congenital
complete AV block and at advance d age due to
progressive fibrosis and ischemia
History
 Syncope, near-syncope, and lightheadedness
 Fatigue, dyspnea, and angina
 Asymptomatic
 Sudden cardiac death
Physical
 Vital Signs (stable vs. unstable, always check HR
manually)
 Signs of heart failure – JVD, a waves, Pulmonary
edema
 New murmurs or gallops
 Target lesions (Lyme)
 Splinter hemm, Osler nodes, etc (endocarditis)
 Neuromuscular changes (mytonic/muscular
dystrophy)
Etiologies
 Idiopathic Progressive Cardiac Conduction Disease
 ½ of cases of AV block
 Lenegre’s disease


Progressive, fibrotic, sclerodegeneration of the conduction system
Younger individuals, may be hereditary
 Lev’s disease
 Calcification extending from fibrous structures (aortic/mitral rings)
into the conduction system
 Older individuals, ? ESRD
 Fibrosis NOS
 Typically mitral and aortic rings
 Mitral  narrow QRS
 Aortic  wide QRS
Etiologies (cont.)
 Ischemic heart disease
 40% of cases
 Either from chronic ischemia or acute MI


Acute MI AV blocks (20% of patients)
 1st degree (8%)
 2nd degree (5%)
 3rd degree (6%)
LBBB/RBBB (10-20%)
 AV nodal block (narrow QRS) associated with inferior wall MI
 Bundle blocks (wide QRS) associated with anterior wall MI
 Drugs
 Calcium channel blockers, beta blockers, digoxin,
amiodarone, adenosine, quinidine, procainamide
Etiologies (cont.)
 Infection
 Lyme disease, endocarditis, Rheumatic fever, Chagas
disease, myocarditis
 Rheumatic disease
 Ankylosing spondylitis, Reiter syndrome, relapsing
polychondritis, rheumatoid arthritis, scleroderma
 Infiltrative disease
 Amyloidosis, sarcoidosis, multiple myeloma,
hemachromatosis, Wilson’s disease
Etiologies
 Hyperthyroidism
 Metabolic
 Hypoxia, hyperkalemia
 Neuromuscular disease
 Muscular dystrophy, dermatomyositis
Treatment
 Correct underlying problem – if you can
 Correct K, stop AV blocking medications, etc.
 If unstable
 Transcutaneous pacing
 If stable
 Plan for permanent pacemaker placement
Permanent Pacemaker
 Class I - Conditions for which evidence and/or general
agreement exists that a given procedure or treatment is
beneficial, useful, and effective
 Third-degree AV block and advanced second-degree AV
block at any anatomic level associated with any one of
the following conditions:

Bradycardia with symptoms, heart failure, arrhythmias,
pauses greater than 3 seconds, escape rate < 40 bpm
Permanent Pacemaker
 Class IIa - Weight of evidence or opinion is in favor of
usefulness or efficacy
 Asymptomatic third-degree AV block at any anatomic
site with average awake ventricular rates of 40 bpm or
faster, especially if cardiomegaly or left ventricular (LV)
dysfunction is present
References
 Gregoratos G, Abrams J, Epstein AE, et al: ACC/AHA/NASPE 2002 guideline
update for implantation of cardiac pacemakers and antiarrhythmia devices:
summary article: a report of the American College of Cardiology/American
Heart Association Task Force on Practice Guidelines. Circulation 2002 Oct 15;
106(16): 2145-61.
 Kojic EM, Hardarson T, Sigfusson N, Sigvaldason H: The prevalence and
prognosis of third-degree atrioventricular conduction block: the Reykjavik
study. J Intern Med 1999 Jul; 246(1): 81-6.
 McEnvoy GK, ed: AHFS Drug Information 2000. Bethesda, Md: American
Society of Health-System Pharmacists; 2000: 1187-95.
 Ostaner LD, Brandt RL, Kjelsberg MI, et al: Electrocardiographic findings
among the adult population of a total natural community. 1965; 31: 888-98.
 Rardon DA, Miles WM, Mitrani RD, et al: Electrocardiographic Recognition:
Atrioventricular Block and Dissociation. In: Zipes DP, Jalife J, eds. Cardiac
Electrophysiology From Cell to Bedside, 2nd ed. Philadelphia, Pa: WB
Saunders; 1995.