Paroxysmal AV Block Differential Diagnosis
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Overview
Considering that a number of conditions may present with a history of syncope and presyncope, paroxysmal AV block must treated as a diagnosis of exclusion. Vasaovagal syncope, situational syncope, carotid sinus hypersensitivity, seizures, structural heart defects such as aortic stenosis, hypertrophic cardiomyopathy and conduction defects such as atrial fibrillation, atrial flutter are a few conditions that need to be ruled out initially.
Differential Diagnosis
| 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 | 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 | P waves associated with 1:1 atrioventricular conduction and a PR interval >200 ms (this is more accurately defined as atrioventricular delay because no P waves are blocked) [1] |
| 2nd Degree AV Block | P waves with a constant rate (<100 bpm) where atrioventricular conduction is present but not 1:1. Mobitz Type 1: P waves with a constant rate (<100 bpm) with a periodic single nonconducted P wave associated with P waves before and after the nonconducted P wave with inconstant PR intervals. Mobitz Type 2 : P waves with a constant rate (< 100 bpm) with a periodic single nonconducted P wave associated with other P waves before and after the nonconducted P wave with constant PR intervals (excluding 2:1 atrioventricular block) [1] |
| 3rd Degree AV Block | No evidence of atrioventricular conduction. [1] |
| 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)".
References
- ↑ 1.0 1.1 1.2 Kusumoto FM, Schoenfeld MH, Barrett C, Edgerton JR, Ellenbogen KA, Gold MR; et al. (2019). "2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society". J Am Coll Cardiol. 74 (7): 932–987. doi:10.1016/j.jacc.2018.10.043. PMID 30412710.