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تشخیص: bidirectional ventricular tachycardia

  • Regular broad complex tachycardia
  • The frontal-plane axis swings 180 degrees from left to right with each alternate beat
  •  علت: دو دلیل عمده آن عبارت است از:


تغییرات بالینی و نواری در مسمومیت دیگوگسین

Clinical features

  • GIT: Nausea, vomiting, anorexia, diarrhoea
  • Visual: Blurred vision, yellow/green discolouration, haloes
  • CVS: Palpitations, syncope, dyspnoea
  • CNS: Confusion, dizziness, delirium, fatigue

Electrocardiographic Features

  • Digoxin can cause a multitude of dysrhythmias, due to increased automaticity (increased intracellular calcium) and decreased AV conduction (increased vagal effects at the AV node)
  • The classic dysrhythmia associated with digoxin toxicity is the combination of a supraventricular tachycardia (due to increased automaticity) with a slow ventricular response (due to decreased AV conduction), e.g.  ’atrial tachycardia with block’.

Other arrhythmias associated with digoxin toxicity are:

  • Frequent VEBs (the most common abnormality), including ventricular bigeminy and trigeminy
  • Sinus bradycardia or slow AF
  • Any type of AV block (1st degree, 2nd degree & 3rd degree)
  • Regularised AF = AF with complete heart block and a junctional or ventricular escape rhythm
  • Ventricular tachycardia, including polymorphic and bidirectional VT

Examples of digoxin toxicity:

bigeminy 590x121 Troubling Tachycardia

Sinus rhythm with frequent VEBs in a pattern of ventricular bigeminy

PAT with block and VEBs due to digoxin toxicity 590x204 Troubling Tachycardia

Atrial tachycardia with high-grade AV block and VEBs

regularized AF 590x222 Troubling Tachycardia

AF with third-degree heart block and an accelerated junctional escape rhythm


تغییرات بالینی و نواری در تاکیکاردی بطنی پلی مورفیک کاتکول آمینرژیک

Clinical features

  • An inherited arrhythmogenic disease characterised by episodic palpitations, syncope or cardiac arrest precipitated by exercise or acute emotion (i.e. catecholamine-triggered ventricular dysrhythmias)
  • Onset during childhood (mean age: 7-9 years old)
  • Family history of sudden cardiac death
  • Ventricular arrhythmias reproducible on exercise stress testing

Electrocardiographic Features

  • Bidirectional VT
  • Polymorphic VT
  • Ventricular fibrillation

ETT in a patient with CPVT

cpvt Troubling Tachycardia

Exercise stress test in a patient with CPVT. Progressively worsening ventricular arrhythmias are observed during exercise. Typical bidirectional VT develops after 1 minute of exercise with a sinus heart rate of approximately 120 beats per minute. Arrhythmias rapidly recede during recovery.

درمان مسمومیت با دیگوکسین

  • The antidote for acute or chronic digoxin toxicity is digoxin-specific immune Fab (‘Digibind’)
  • Initial empiric dosing of Digibind is 5 ampoules for acute overdose, 2 ampoules for chronic toxicity and up to 20 ampoules for cardiac arrest
  • AV block may respond to atropine 0.6 mg IV bolus, repeated to a maxium of 1.8 mg (20 mcg/kg in children)
  • Dysrhythmias may be treated with IV lignocaine 1mg/kg (max 100mg) over 2 minutes
  • Hyperkalaemia is treated in the usual way with insulin and dextrose, sodium bicarbonate… however, IV calcium is (traditionally) contraindicated!
  • DC cardioversion is unlikely to be successful in digoxin poisoning. Patients in cardiac arrest may require continuous CPR until Digibind can be sourced and administered.

درمان تاکیکاردی بطنی پلی مورفیک کاتکول آمینرژیک

  • Beta blockers (e.g. propranolol) are used for suppression of catecholamine-triggered ventricular tachydysrhythmias.
  • Electrical cardioversion / defibrillation may be required for haemodynamically unstable VT/VF, although patients often spontaneously revert to sinus rhythm.
  • Implantable cardioverter-defibrillator (ICD) insertion is considered for primary or secondary prevention of cardiac arrest.


  • Menduiña MJ, Candel JM, Alaminos P, Gómez FJ, Vílchez J. Bidirectional ventricular tachycardia due to digitalis poisoning. Rev Esp Cardiol. 2005 Aug;58(8):991-3. Spanish [PMID: 16053836] [Full text - English]
  • Murray L, Daly F, McCoubrie D, Soderstrom J, Pascu O, Armstrong J, Cadogan M. Toxicology Handbook, Second Edition. Churchill Livingstone (2010).
  • Napolitano C, Priori SG, Bloise R. Catecholaminergic Polymorphic Ventricular Tachycardia. 2004 Oct 14 [updated 2009 Jul 7]. In: Pagon RA, Bird TC, Dolan CR, Stephens K, editors. GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle (1993) [PMID: 20301466]
+ نوشته شده توسط دکتر جلال کریمی در شنبه دوم بهمن 1389 و ساعت 16:5 |

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