heart author" faq
Bradycardia Management


Treatment of bradycardia depends on the severity of symptoms, the correlation of symptoms with the bradycardia, and the presence of possible reversible causes (see table of causes of bradycardia ). There are few indications for treatment of asymptomatic bradycardia.

The American Heart Association guidelines for implantation of pacemakers (see figures 84b, 85, 86, 87, 88, 89, 90, 91, 92a, 92b, 92c) list the following as universally accepted (class I) indications in asymptomatic patients:

1. Third degree AV block with documented asystole of 3 or more seconds (in sinus rhythm) or escape rates below 40 beats per minute in awake patients;

2. 3rd degree AV block or 2nd degree AV Mobitz type II block in patients with bifascicular and trifascicular block;

3. Congenital 3rd degree AV block with wide QRS escape rhythm, ventricular dysfunction, or bradycardia markedly inappropriate for age.

Potential (class II) indications for pacing in asymptomatic patients include the following:

1.3rd degree AV block with faster escape rates in patients who are awake,

2.2nd degree AV Mobitz type II block in patients without bifascicular or trifascicular block,

3.The incidental finding on electrophysiologic study of block below or with in the His bundle.

When bradycardia (even if extreme) is present only during sleep, pacing usually not indicated.

In symptomatic patients the keys to proper decision making are correlation of symptoms to bradycardia and reversibility of causative factors (see table of causes of bradycardia).

Symptoms definitely related to simultaneous, confirmed bradycardia that is caused by intrinsic sinus-node dysfunction or AV block, should be treated by permanent pacing using an internally implanted pacemaker (see figures 84b, 85, 86, 87, 88, 89, 90, 91, 92a, 92b, 92c)

The Sinus and AV nodes are relatively resistant to permanent injury by infarction (cell death due to lack of coronary blood flow) or infection. Normal function should recover over time. Thus, sinus bradycardia, or AV nodal block in these settings rarely require permanent pacing.

Permanent damage occurs more really to the bundle of His. Even transient complete AV block in the His-Purkinje system due to infarction or infection justifies the insertion of a pacemaker.

Among those with recurrent unconfirmed syncope and chronic bifascicular or trifascicular block, pacing is indicated if other likely causes (i.e. ventricular tachycardia) have been ruled out.

Symptomatic bradycardia due to extrinsic factors require clinical judgement.

A change in drug therapy should be considered if the bradycardia is due to a drug. But if a substitute drug is not efficacious, then pacing becomes indicated.

Pacing is also indicated with bradycardia-tachycardia syndrome if the drugs used to control the ventricular rate during atrial arrhythmias (see figures 2, 3a, 3b, 4, 5a, 5b, 10, 14) cause bradycardia during sinus rhythm.

Atrial based pacing is preferred in patients with sinus-node dysfunction because it reduces the incidence of atrial fibrillation, pacemaker syndrome, and formation of blood clots, which can break away from the heart's walls (embolus) and go to a peripheral vessel in the brain, legs, or other parts of the body.

Dual chambers pacing (with electrodes in both right atrium and ventricle) is needed if AV block is also present (see figures 84b, 85, 86, 87, 88, 89, 90, 91, 92a, 92b, 92c).

For neurocardiac syncope, patient education and drug trials are indicated before use of pacing.

In some cases of more profound bradycardia, reversible causes may be found responsible and are treatable (see figure 93b).

Patients with atrial fibrillation (a state of marked atrial irritability causing multiple, rapid, irregular excitation waves to bombard the AV node and hence rapid heart rates) may have great variability of heart rates (see figures 14, 15a and 15b).

In these patients prolonged ventricular pauses may occur frequently. Many have pauses longer than 2 seconds to 3 seconds. It is felt that these patients with atrial fibrillation and day time pauses of up to 2.8 seconds and night time pauses up to 4.0 seconds should be considered within expected limits. Hence, these episodes if asymptomatic are treated conservatively before pacemaker implantation.