Paroxysmal AV block

Paroxysmal AV block Microchapters
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Case #1
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Akash Daswaney, M.B.B.S[2]

Synonyms and keywords:

Overview

• Paroxysmal AV block is defined as a delayed escape rhythm which repetitively blocks conduction from the atria to the ventricles, thereby causing syncope, conduction defects such as asystole and sudden cardiac death.
• It may or may not be associated with Phase 3 or Phase 4 conduction defects.
• It may be due to an increased vagal tone, innately low adenosine levels or an intrinsic conduction defect, all of which lead to different ECG presentations.
• Insufficient data is available regarding the exact etiology, diagnostic study of choice and treatment of paroxysmal AV blocks.
• It can be thought of more as a disease of exclusion. However,efforts must be made to have a standardized approach to such patients.

Historical Perspective

Famous cases

Classification

Based on Cause

Pathophysiology

Intrinsic AV Block | Extrinsic Vagal AV Block | Extrinsic Idiopathic AV Block

Epidemiology and Etiology

Epidemiology | Etiology

Disease	Findings
Vasaovagal Syncope	Occurs secondary to emotional distress, prolonged standing, painful stimuli. Seen more in women and may be diagnosed by tilt table testing. Not associated with periods of asystole.
Situational Syncope	Due to cardioinhibitory and vasopressor mechanisms. Syncope may be associated with cough, micturition and defecation. Not associated with periods of asystole.
Carotid Sinus hypersensitivity	Common causes of unexplained syncope in individuals more than 40 years of age. Syncope may be associated with wearing shirts with tight collars. Not associated with periods of asystole.
Aortic Stenosis	Presents with syncope, angina and dyspnea on exertion. Not associated with periods of asystole but may show features of left ventricular hypertrophy. On Physical examination,pulsus parvus et tardus may be noted and a systolic click followed by a crescendo decrescendo murmur may be heard over the aortic area.
Hypertrophic Cardiomyopathy	Hypertrophic Cardiomyopathy – Common cause of sudden cardiac death in adolescents during physical activity. Family history is often present. Not associated with periods of asystole.
1st Degree AV Block	Associated with persistently prolonged PR interval with or without narrow QRS complexes. Not associated with periods of asystole.
2nd Degree AV Block	Mobitz type 1 is associated with progressively prolonged PR interval till one p wave does not conduct a QRS complex and group beating. Mobitz type 2 is associated with an episodic and unpredictable absence of conduction.
3rd Degree AV Block	Complete dissociation between P and QRS complexes. Narrow or wide junctional or escape rhythms may be present. May present with syncope, asystole and sudden cardiac death.
Atrial Fibrillation	May present with syncope, presyncope, lightheadedness or palpitations. Associated with irregular RR intervals and absence of clearly defined P waves.
Congenital long QT syndrome/ Torsade de pointes	Associated with electrolyte abnormalities such as hypokalemia, hypomagnesemia, hypocalcemia or congenital conditions such as Jervell- Lange- Nielsen Syndrome and Romano ward Syndrome which may degenerate into a life threatening polymorphic ventricular tachycardia.
Seizures	May be associated with generalized tonic clonic movements, tongue bite, bowel or bladder incontinence, a post ictal state and Todd’s paralysis. Following a loss of consciousness, there is a delayed recovery time.
Others	Atrial Flutter,Subclavian Steal syndrome, Vertebrobasilar Transient Ischemic Attacks, Sick Sinus Syndrome, Psychogenic Pseudosyncope, Psychogenic Non epileptic Seizures.

"ESC Guidelines on Syncope (Diagnosis and Management of)".

Diagnosis

Initial Approach | History and Symptoms | Electrocardiogram, Holter Monitoring, External Loop Recorder | Implantable Loop Recorder | Electrophysiologic studies | Vagal Maneuvers,Carotid Sinus Massage and Tilt Table testing | Laboratory Findings and Stimulation tests | Diagnostic Summary Table |

Treatment

Cardiac Pacing |Treatment for Reflex Syncope|Theopylline |

Case Studies

Case #1

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