Rarely associated w HLA-B27 and aortic insufficiency (Ann IM 1997;127:621)

Sx:

1st-degree heart block usually causes no sx

2nd-degree may cause dizziness or dyspnea

3rd-degree may cause syncope, especially on standing

Si:

1st-degree heart block = PR >0.22 sec

2nd-degree = some unconducted P waves

3rd-degree = no relationship between Ps and QRSs

1st-degree heart block usually benign if not associated with organic disease (Nejm 1986;315:1183)

r/o: Lyme disease if from endemic area, even if no other sx, w serology, rx with antibiotics and temporary not permanent pacer (Ann IM 1989;110:339)

Athletes' arrhythmia's (Sports Med 1998;25:139), eg, 1st- and 2nd-degree (Mobitz I) heart blocks, sinus bradycardia, junctional rhythms; all from incr vagal tone, all go away w exercise and deconditioning

Lab:

Noninv:EKG; Holter monitor may still miss a majority of intermittent heart blocks (Nejm 1989;321:1703)

• Mobitz I (Wenckebach) heart block; intranodal; progressively incr PR, then dropped beat w progressively shortening R-R; usually in AV node, especially w digoxin or inferior MI/ischemia, but can occur in SA node (detect by closer and closer R-Rs), or in distal system if BBB conduction pattern
• Mobitz II heart block, infranodal; fixed PR and dropped beats; R-R intervals of drop are exactly 2 × the normal R-R interval, unlike Mobitz I; if several in a row, may have distal escape rhythm; usually going to need permanent pacing; r/o hyperkalemia and rarely meds (procainamide, quinidine, amiodareone) as causes

Rx: 1st degree may not need rx; 2nd and 3rd degree: isoproterenol iv or sl, atropine iv, theophylline 100 mg/min iv up to 250 mg (Ann IM 1995;123:509), or external pacer, until can get transvenous pacemaker

Transvenous pacemaker, temporary 1st, then permanent unless inferior MI, which will usually reverse spontaneously. Prophylactic pacers in bifascicular blocks only if 2 or more syncopes and even then questionable (Nejm 1982;307:137, 180). Placement with EKG guidance, sample leads (Nejm 1972;287:651). Coronary sinus placement ok for temporary; tip is seen posteriorly on lateral chest xray.

Permanent pacemaker: (rv—Jama 2002;287:1848; Ann IM 2001;134:1130; Nejm 1996;334:89; Mod Concepts Cardiovasc Dis 1991;60:31); dual and triple (RA, RV, LV) chamber “physiologic” types more expensive, use when need atrial kick?, in sick sinus syndrome (Nejm 2002;346:1854), may decr later Afib incidence (Nejm 2000;342:1385) but much dispute about what is best (Nejm 2005;353:145, 202) especially in elderly Table 2.5

Table 2.5 Pacer Nomenclature

R added to designation if rate adaptive capability present. Thus a VVI pacer paces the ventricle, and senses ventricular beats by inhibiting the next paced beat.