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Bradycardia: Difference between revisions
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Paroxysmal atrioventricular block (PAVB), is characterized by a sudden and unexpected block of the atrial impulse. Due to the delayed emerge of an escape rhythm, these patients often present with syncope. However, if a escape rhythm is established patients may present themselves without symptoms. Two different variations of the PAVB are commonly distinguished; | Paroxysmal atrioventricular block (PAVB), is characterized by a sudden and unexpected block of the atrial impulse. Due to the delayed emerge of an escape rhythm, these patients often present with syncope. However, if a escape rhythm is established patients may present themselves without symptoms. Two different variations of the PAVB are commonly distinguished; | ||
<b>1. Pause-dependent PAVB</b> | <b>1. Pause-dependent PAVB</b><br/> | ||
The PD-PAVB occurs after the onset of a pause. This pause can be compensatory after a premature beat, overdrive suppression of sinus rhythm or other disorders of impulse formation. There are several hypothesis to explain this phenomenon, amongst them phase 4 depolarization (see Phase 4 abberation). | The PD-PAVB occurs after the onset of a pause. This pause can be compensatory after a premature beat, overdrive suppression of sinus rhythm or other disorders of impulse formation. There are several hypothesis to explain this phenomenon, amongst them phase 4 depolarization (see Phase 4 abberation). | ||
<b>2. Tachycardia-dependent PAVB</b> | <b>2. Tachycardia-dependent PAVB</b><br/> | ||
The TD-PAVB occurs more frequently in patients due to the increased rate of the atria. TD-PAVB is associated with 2nd degree Mobitz block and Adam-Stokes Syndrome. However, some occurrences of TD-PAVB occur without a noticeable increase in atrial rate, due to minor electrophysiological changes due to changes in autonomic tone or coronary perfusion. The mechanism responsibly for the occurrence of TD-PAVB is probably repetitive concealed conduction.<cite>Elsherrif</cite> | The TD-PAVB occurs more frequently in patients due to the increased rate of the atria. TD-PAVB is associated with 2nd degree Mobitz block and Adam-Stokes Syndrome. However, some occurrences of TD-PAVB occur without a noticeable increase in atrial rate, due to minor electrophysiological changes due to changes in autonomic tone or coronary perfusion. The mechanism responsibly for the occurrence of TD-PAVB is probably repetitive concealed conduction.<cite>Elsherrif</cite> | ||
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===Device Therapy=== | ===Device Therapy=== | ||
Implantable pacemakers activate cardiac myocardium with electrical stimulation, leading to muscle contraction. Due to the nature of a pacemaker, the activation is different from the physiological conduction system, there are electrical and mechanical consequences. It is therefore important to adjust pacemaker setting to the individual patient. The type of pacemakers and their settings are extensively covered in the device chapter of cardiac arrhythmias. The indications for pacemaker implantation in patients with bradyarrhythmias are mentioned below. | Implantable pacemakers activate cardiac myocardium with electrical stimulation, leading to muscle contraction. Due to the nature of a pacemaker, the activation is different from the physiological conduction system, there are electrical and mechanical consequences. It is therefore important to adjust pacemaker setting to the individual patient. The type of pacemakers and their settings are extensively covered in the device chapter of cardiac arrhythmias. The indications for pacemaker implantation in patients with bradyarrhythmias are mentioned below. | ||
* <b>Sinus node disease:</b> Pacemaker implantation should be strongly considered in patients with sinus node disease which manifests as symptomatic bradycardia in which the symptom-rhythm correlation must have been 1) spontaneously occurring or 2) drug-induced where alternative drug therapy is lacking.<cite>Kay, Epstein</cite> Other reasonable eligible candidates for permanent pacing are patients with syncope with sinus node disease, spontaneously occurring or induced at electrophysiological study or patients with symptoms clearly associated to bradycardia but without documentation of this bradycardia. | * <b>Sinus node disease:</b> | ||
Pacemaker implantation should be strongly considered in patients with sinus node disease which manifests as symptomatic bradycardia in which the symptom-rhythm correlation must have been 1) spontaneously occurring or 2) drug-induced where alternative drug therapy is lacking.<cite>Kay, Epstein</cite> Other reasonable eligible candidates for permanent pacing are patients with syncope with sinus node disease, spontaneously occurring or induced at electrophysiological study or patients with symptoms clearly associated to bradycardia but without documentation of this bradycardia. | |||
Patients with sinus node disease without symptoms including use of bradycardia-provoking drugs, patients with symptoms of sinus node dysfunction occurring in the absence of the bradycardia or patients with symptomatic sinus node dysfunction where symptoms can reliably be attributed to non-essential medication do not have an indication for permanent pacemaker therapy.<cite>Epstein</cite> | Patients with sinus node disease without symptoms including use of bradycardia-provoking drugs, patients with symptoms of sinus node dysfunction occurring in the absence of the bradycardia or patients with symptomatic sinus node dysfunction where symptoms can reliably be attributed to non-essential medication do not have an indication for permanent pacemaker therapy.<cite>Epstein</cite> | ||
* <b>Atrioventricular Block:</b> The following patients with AV conduction block have an strong indication for pacemaker therapy; 1) chronic symptomatic third or second degree (Mobitz I or II) atrioventricular block including induced third or second degree atrioventricular block by required medication<cite>Kastor, Dreifus, Epstein</cite> 2) asymptomatic patients with third or second degree (Mobitz I or II) atrioventricular block and documented asystole greater than 3.0 seconds in SR or 5.0 seconds in AF, an escape rhythm less than 40 bpm (or >40 bpm with left ventricular dysfunction) or infranodal escape rhythm <cite>Epstein, Ecktor, Shaw</cite>3) neuromuscular diseases (e.g. myotonic muscular dystrophy, Kearns–Sayre syndrome, etc.) with third-degree or second-degree atrioventricular Block<cite>Stevenson, James</cite> or 4) third or second degree (Mobitz I or II) atrioventricular block after catheter ablation of the atrioventricular junction or after valve surgery when the block is not expected to resolve<cite>Langberg, Kim, Glikson, Epstein</cite> and 5) patient with third or second degree AV block during exercise with no myocardial ischemia<cite>Chokski, Epstein</cite>. Patients with asymptomatic first degree atrioventricular block, asymptomatic second degree Mobitz I with supra-Hisian conduction block or atrioventricular block expected to resolve do not require a pacemaker implantation.<cite>Mymin, Strasberg, Epstein</cite> | * <b>Atrioventricular Block:</b> The following patients with AV conduction block have an strong indication for pacemaker therapy; 1) chronic symptomatic third or second degree (Mobitz I or II) atrioventricular block including induced third or second degree atrioventricular block by required medication<cite>Kastor, Dreifus, Epstein</cite> 2) asymptomatic patients with third or second degree (Mobitz I or II) atrioventricular block and documented asystole greater than 3.0 seconds in SR or 5.0 seconds in AF, an escape rhythm less than 40 bpm (or >40 bpm with left ventricular dysfunction) or infranodal escape rhythm <cite>Epstein, Ecktor, Shaw</cite>3) neuromuscular diseases (e.g. myotonic muscular dystrophy, Kearns–Sayre syndrome, etc.) with third-degree or second-degree atrioventricular Block<cite>Stevenson, James</cite> or 4) third or second degree (Mobitz I or II) atrioventricular block after catheter ablation of the atrioventricular junction or after valve surgery when the block is not expected to resolve<cite>Langberg, Kim, Glikson, Epstein</cite> and 5) patient with third or second degree AV block during exercise with no myocardial ischemia<cite>Chokski, Epstein</cite>. Patients with asymptomatic first degree atrioventricular block, asymptomatic second degree Mobitz I with supra-Hisian conduction block or atrioventricular block expected to resolve do not require a pacemaker implantation.<cite>Mymin, Strasberg, Epstein</cite> | ||