Bradycardia

大林慈濟醫院心臟內科 李易達醫師101.09.09

竇房節 (SA node)

房室結 (AV node)希氏束 (Bundle of His)

浦金氏纖維 (Purkinje fiber)

Normal sinus rhythmHR: 87bpm, PR interval: 150ms

Normal sinus rhythm

• Heart rate: 60~100bpm

• A P wave before every QRS complex

• Normal P axis (upright in lead II)

• PR interval >0.12 second

HR: 61bpm, PR: 128ms

Ectopic atrial rhythm

Rhythm evaluation on ECG

• Rate– Regularity

• P wave ?• P wave morphology• P wave axis

– Normal P wave axis: upright in lead II

• PR interval (P & QRS relationship)– Normal PR interval: 120~200ms– Constant

Bradycardia

• Bradycardia: heart rate < 60bpm

• May be a normal physiological phenomenon or result from a cardiac or non-cardiac disorder– During sleeping– Athletes

• Symptoms: – Dizziness, near syncope, syncope, ischemic

chest pain, and hypoxic seizures

Pathological etiologies of bradycardia

• Medication– B-blocker– Ca channel blocker– Digoxin– Class IA, IC, III

• Myocardial infarction• Inflammation/infection

– Myocarditis– Infectivce endocarditis– Lyme disease

• Metabolic effect– Electrolytes– Hypothyroidism– Hypothermia

• Autoimmune diseases– SLE

• Surgery• Degeneration

– Sick sinus syndrome

Bradyarrhythmia

• Sinus node dysfunction– Symptomatic sinus bradycardia– Sinus pause/sinus arrest– Sino-atrial exit block– Tachycardia-bradycardia syndrome

• AV block• Junctional/ventricular escape rhythm• Atrial fibrillation with slow ventricular response

Marked sinus bradycardia

• May be symptomatic if heart rate < 45bpm

• Usually related to– Increased vagal tone– Medication: b-blocker, Ca channel blocker– Sick sinus syndrome (SA node dysfunction)

Marked sinus bradycardiaHR: 42bpm, PR: 184ms

Sinus pause/arrest

• Transient cessation of impulse formation at the sinoatrial node

• A prolonged pause without P activity

• The pause is unrelated to the length of the P-P cycle

Sinus pause/arrest

SA exit block

• A transient failure of sinus impulse conduction to the atrial myocardium

• SA exit block

– 1st degree SA block

– 2nd degree SA block• Type I: group beating, shortened PP interval• Type II: the pause length was two times of PP

interval

– 3rd degree SA block: escape rhythm

SA exit block

2nd degree SA exit block type IHR: 91bpm, PR:142bpm

2nd degree SA exit block type II

Tachycardia-bradycardia syndrome

• Common in sick sinus syndrome (sinus node dysfunction)

• Paroxysmal atrial tachyarrhythmia followed by sinus bradycardia, sinus pause or escape rhythm

Tachycardia-bradycardia syndrome

EPS to evaluate sinus node function• Sinus node recovery time (SNRT)

– SNRT < 1500 ms– cSNRT (SNRT - BCL) < 550 ms– SNRT/NSR < 150%

EPS to evaluate SA conduction

• Sinoatrial conduction time (SACT)

– 45~125ms

Atrio-ventricular block

• First degree AV block

• Second degree AV block

– Mobitz type I

– Mobitz type II

– Advance AV block: 2:1, 3:1, 4:1,… AV block

• Three degree (Complete) AV block

1st Degree AV block

• Simple prolongation of PR interval (> 0.2 seconds)

• No dropped QRS complexes

• All P waves are conducted

1st degree AV blockHR: 57bpm, PR: 350ms

2nd degree Mobitz type I AV block(Wenckebach phenomenon)

• PR interval progressively increases before dropped QRS

• Intermittent dropping of the QRS• RR interval may progressively decrease• Grouping of QRS

2nd degree Mobitz type I AV block(Wenckebach phenomenon)

HR: 44bpm, PR: 292ms

2nd degree Mobitz type II AV block

• Fixed PR interval before dropped QRS complex

2nd degree Mobitz type II AV blockHR: 59bpm, PR: 136ms

2:1 AV block

• QRS complex dropped in every other beat

• Constant PR interval

• Mobitz type I or II

2:1 AV blockHR: 41bpm, PR: 192ms

HR: 40bpm, PR: 186ms

2: 1 AV block

Three degree (Complete) AV block

• Complete interruption of atrial conduction

• Independent atrial and ventricular rhythms (AV dissociation)

• Regular PP and RR interval

• Atrial rate > ventricular rate

• P wave march through the QRS complexes

Three degree (Complete) AV block

HR: 43bpm

HR: 45bpm

Complete AV block

HR: 67bpm, PR: 207ms

Non-conducted APC

Escape rhythm

• When the ventricles are not stimulated as a result of automaticity or conduction problems

• Marked sinus bradycardia, sinus pause, complete AV block

• Junctional vs. ventricular escape rhythm

– Junctional: narrow, rate: 40~60bpm

– Ventricular: wide, rate: 20~40bpm

Escape rhythmHR: 36bpm

Sinus bradycardia with junctional escape rhythm

HR: 50bpm

Complete AV block with ventricular escape rhythm

HR: 27bpm

Atrial fibrillation with slow ventricular response

• Atrial rate in Af: 350~700bpm

• The ventricular rate depends on the AV conduction ability

• Impaired AV conduction

Atrial fibrillation with slow ventricular response

HR: 48bpm

Af with regular RR interval

Af with complete AV block and junctional escape rhythm

感恩聆聽 !