3rd Degree AV blockJason Haag

Heart Block1st Degree AV Block

one-to-one relationship exists between P waves and QRS complexes, but the PR interval is longer than 200 ms

Heart Block2nd 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 Block2nd Degree Mobitz Type II AV Block

PR interval is constant, but occasionally P waves are not followed by the QRS complexes

Heart Block3rd Degree Heart Block

More P waves than the QRS complexes exist and no relationship exists between them

3rd Degree Heart BlockBlock can be in AV node or infranodal

conduction systemAV node

2/3 escape rhythms have narrow QRS (junctional)Fascicular or bundle branches

Wide QRS (subjunctional)

Rate typically in low 40s

FrequencyIn 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

HistorySyncope, near-syncope, and lightheadedness

Fatigue, dyspnea, and angina

Asymptomatic

Sudden cardiac death

PhysicalVital Signs (stable vs. unstable, always check

HR manually)Signs of heart failure – JVD, a waves,

Pulmonary edemaNew murmurs or gallopsTarget lesions (Lyme)Splinter hemm, Osler nodes, etc

(endocarditis)Neuromuscular changes (mytonic/muscular

dystrophy)

EtiologiesIdiopathic Progressive Cardiac Conduction Disease

½ of cases of AV blockLenegre’s disease

Progressive, fibrotic, sclerodegeneration of the conduction system

Younger individuals, may be hereditaryLev’s disease

Calcification extending from fibrous structures (aortic/mitral rings) into the conduction system

Older individuals, ? ESRDFibrosis NOS

Typically mitral and aortic rings Mitral narrow QRS Aortic wide QRS

Etiologies (cont.)Ischemic heart disease

40% of casesEither 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 MIBundle blocks (wide QRS) associated with anterior

wall MIDrugs

Calcium channel blockers, beta blockers, digoxin, amiodarone, adenosine, quinidine, procainamide

Etiologies (cont.)Infection

Lyme disease, endocarditis, Rheumatic fever, Chagas disease, myocarditis

Rheumatic diseaseAnkylosing spondylitis, Reiter syndrome,

relapsing polychondritis, rheumatoid arthritis, scleroderma

Infiltrative diseaseAmyloidosis, sarcoidosis, multiple myeloma,

hemachromatosis, Wilson’s disease

EtiologiesHyperthyroidismMetabolic

Hypoxia, hyperkalemiaNeuromuscular disease

Muscular dystrophy, dermatomyositis

TreatmentCorrect underlying problem – if you can

Correct K, stop AV blocking medications, etc.If unstable

Transcutaneous pacingIf stable

Plan for permanent pacemaker placement

Permanent PacemakerClass I - Conditions for which evidence

and/or general agreement exists that a given procedure or treatment is beneficial, useful, and effectiveThird-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 PacemakerClass 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.