Ventricular tachycardia

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Ventricular tachycardia in a German Shepherd

Ventricular tachycardia (ventricular arrhythmia) is a heart disease of dogs characterized by a series of ventricular premature complexes (VPC) usually greater than 100 beats per minute.

In this condition, the RR interval on the ECG is usually regular, but nonconducted sinus P waves may be superimposed on or between the ventricular complexes. This is usually unrelated to the VPCs because the AV node and/or ventricles are in a refractory period (physiological AV dissociation)[1].

The term 'capture beat' refers to the successful conduction of a sinus P wave into the ventricles uninterrupted by another VPC. If the normal ventricular activation sequence is interrupted by another VPC, a fusion complex can result[2].

Causes include:

Clinically affected dogs present frequently with syncope, weak femoral pulses, pale mucous membranes, panting, weakness, exercise intolerance, sudden death and tachycardia audible on auscultation[14]. The syncope, commonly seen in the Boxer dog with normal echocardiograms, is thought to be due to secondary ischemic bradycardia which ensues as a result of ventricular tachycardia[15].

This condition is life-threatening as ventricular tachycardia can quickly degenerate into ventricular fibrillation, which leads invariably to poor cardiac contractility, reduced ventricular diastolic functioning and eventual congestive heart failure[16].

Diagnosis can be rapidly achieved on ECG examination, but 24-hour Holter monitors are usually required to definitively confirm the suspicion[17].

Use of a defibrillator may be required to restore normal heart beats[18], followed by intravenous constant rate infusion of lidocaine[19].

The underlying cause of ventricular fibrillation must be address for long-term survival of cardiac patients.

References

  1. Santilli RA et al (2012) Orthodromic atrioventricular reciprocating tachycardia conducted with intraventricular conduction disturbance mimicking ventricular tachycardia in an English Bulldog. J Vet Cardiol 14(2):363-370
  2. Nelson, RW & Guillermo Couto, C (1998) Small animal internal medicine. Mosby, Missouri. pp:22-23
  3. Winter RL et al (2010) ECG of the month. Arrhythmogenic right ventricular cardiomyopathy in a Boxer. J Am Vet Med Assoc 236(9):961-963
  4. Cruickshank J et al (2009) Genetic analysis of ventricular arrhythmia in young German Shepherd Dogs. J Vet Intern Med 23(2):264-270
  5. Gelzer AR et al (2010) Combination therapy with mexiletine and sotalol suppresses inherited ventricular arrhythmias in German shepherd dogs better than mexiletine or sotalol monotherapy: a randomized cross-over study. J Vet Cardiol 12(2):93-106
  6. Rodríguez-Morales O et al (2012) Plasmid DNA immunization with Trypanosoma cruzi genes induces cardiac and clinical protection against Chagas disease in the canine model. Vet Res 43(1):79
  7. Ginn JA et al (2013) Systemic hypertension and hypertensive retinopathy following PPA overdose in a dog. J Am Anim Hosp Assoc 49(1):46-53
  8. Matos J et al (2012) Myocardial damage and paroxysmal ventricular tachycardia in a dog after Albuterol intoxication. Schweiz Arch Tierheilkd 154(7):302-305
  9. Kraus MS et al (2009) Toxicity in Doberman Pinchers with ventricular arrhythmias treated with amiodarone (1996-2005). J Vet Intern Med 23(1):1-6
  10. Thompson DJ et al (2011) Haemangiosarcoma of the interventricular septum in a dog. N Z Vet J 59(6):332-336
  11. Langs LL (2009) Budd-Chiari-like syndrome in a dog due to liver lobe entrapment within the falciform ligament. J Am Anim Hosp Assoc 45(5):253-256
  12. Santilli RA et al (2009) Outflow tract segmental arrhythmogenic right ventricular cardiomyopathy in an English Bulldog. J Vet Cardiol 11(1):47-51
  13. Santilli RA et al (2011) Ventricular tachycardia in English bulldogs with localised right ventricular outflow tract enlargement. J Small Anim Pract 52(11):574-580
  14. MacKie BA et al (2010) Retrospective analysis of an implantable loop recorder for evaluation of syncope, collapse, or intermittent weakness in 23 dogs (2004-2008). J Vet Cardiol 12(1):25-33
  15. Thomason JD et al (2008) Bradycardia-associated syncope in 7 Boxers with ventricular tachycardia (2002-2005). J Vet Intern Med 22(4):931-936
  16. Wu W et al (2008) Application of quantitative tissue velocity imaging to evaluate left ventricular early diastolic dysfunction in dogs with heart failure due to rapid ventricular pacing. J Am Soc Echocardiogr 21(11):1269-1276
  17. Santilli RA et al (2010) Evaluation of the diagnostic value of an implantable loop recorder in dogs with unexplained syncope. J Am Vet Med Assoc 236(1):78-82
  18. Pariaut R et al (2011) Implantable cardioverter-defibrillator in a German shepherd dog with ventricular arrhythmias. J Vet Cardiol 13(3):203-210
  19. Prosek R (2010) Electrical cardioversion of sustained ventricular tachycardia in three Boxers. J Am Vet Med Assoc 236(5):554-557
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