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| | ==Introduction== | | ==Introduction== |
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| − | '''Ventricular tachycardia''' (VT) is a '''rhythm disturbance''' classified as '''four or more [[Ventricular Premature Complexes|ventricular premature complexes]] (VPC's) in sequence''', producing a '''rapid''' heart rate. It is a serious condition which has the capability of causing '''[[Ventricular Fibrillation|ventricular fibrillation]]''' and '''sudden death'''. It most commonly occurs secondary to an existing systemic or cardiac abnormality. It is classed as a '''grade 4''' rhythm disturbance because it is '''electrically unstable''' and causes '''haemodynamic compromise'''.
| + | Ventricular tachycardia is a rhythm disturbance that produces a rapid, regular heart beat caused by continuous ventricular premature complexes (VPCs). It is a serious condition which has the capability of causing ventricular fibrillation and ultimately death. It is most likely to occur secondary to an existing abnormality in either the heart or the rest of the body. |
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| − | ==Small Animals==
| + | It is particularly common in Dobermanns secondary to Dilated Cardiac Myopathy. |
| − | It is particularly common in '''Dobermanns''' secondary to '''[[Dilated Cardiomyopathy|Dilated CardioMyopathy]]''' and in the '''Boxer''' secondary to '''Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)'''. The rhythm disturbance is much less common in cats and normally the result of end-stage cardiomyopathy. | |
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| − | ===Causes=== | + | ====Causes==== |
| − | * Significant '''structural damage to the heart, heart failure''' or a '''breed specific myopathy'''
| + | Significant myocardial damage to the heart or disease in other systems, Drug reactions, Hypoxia, Anaemia, Electrolyte and acid-base disturbances, etc. |
| − | * '''Systemic disease''' such as hypoxia, [[Anaemia|anaemia]], electrolyte and acid-base disturbances, [[Hyperthyroidism|hyperthyroidism]] (cats) etc.
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| − | * '''Drug reactions'''
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| − | ===Clinical Signs===
| + | ==Clinical Signs== |
| − | On cardiac auscultation, '''heart rate is abnormally high''' (>160-180 in dogs). There may be signs of '''haemodynamic compromise''' and '''output failure''' such as collapse, hypotension, syncope and congestive heart failure. '''Sudden death''' may be the only presenting sign, especially in predisposed breeds. | + | On cardiac auscultation, heart rate is abnormally high and irregular. The dog may present collapsed and have signs of output failure. |
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| − | ===Diagnosis===
| + | ==Diagnosis== |
| − | The condition can be diagnosed by '''[[ECG]]'''. The ECG shows''' wide and bizarre QRS complexes''' and '''P waves that are not consistently related''' to the QRS complexes. Heart rate is '''high (>160-180 in dogs)'''. QRS complexes can be '''monomorphic''' (similar in appearance with a regular R-R interval) or '''polymorphic''' (variable appearance and irregular R-R interval). A polymorphic appearance is suggestive of a more unstable myocardium. The P-P interval should be regular. | + | The condition can be diagnosed by ECG. The ECG shows wide and irregular QRS complexes, and P waves without QRS complexes following. |
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| − | Sustained Ventricular Tachycardia lasts for more than 30 seconds, unsustained VT lasts less than thirty seconds.
| + | ====Treatment==== |
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| − | ===Treatment=== | |
| | The underlying cause should be identified and treated where possible. | | The underlying cause should be identified and treated where possible. |
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| − | Treatment of the arrhythmia itself is always warranted because V-tach is classed as a grade 4 rhythm disturbance. The aim of treatment is to '''restore a normal sinus rhythm and reduce the ventricular rate''' thus improving cardiac output and preventing sinus arrest.
| + | '''Small Animals''' |
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| − | '''Dog:''' [[Local Anaesthetics|lidocaine]] (1st line of treatment), quinidine or procainamide (2nd line of treatment). Side effects of lidocaine include hypotension and gastrointestinal signs.
| + | Dog: lidocaine (1st line of treatment), quinidine or procainamide (2nd line of treatment) |
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| − | '''Cat:''' [[Heart Failure, Treatment|propranolol]] (1st line of treatment), small dose of lidocaine (2nd line of treatment). A high dose of lidocaine can cause neurotoxicity in the cat.
| + | Cat: propranolol (1st line of treatment), small dose of lidocaine (2nd line of treatment) |
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| − | Following 1st line treatment, serum [[Potassium|potassium]] levels should be assessed and corrected if necessary.
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| − | ===Prognosis===
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| − | Prognosis depends on the underlying cause of the arrhythmia and the success of its treatment.
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| − | ==Large Animals==
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| − | Ventricular tacycardia is most likely to be diagnosed and treated in the '''horse'''.
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| − | ===Causes===
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| − | VT normally occurs secondary to '''myocardial disease, endotoxaemia or electrolyte and acid-base abnormalities'''. It can also occur idiopathically.
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| − | | |
| − | ===Clinical Signs===
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| − | Cardiac auscultation should reveal an '''abnormally high heart rate'''. There may also be a history of exercise intolerance and dyspnoea.
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| − | | |
| − | ===Diagnosis===
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| − | The condition can be diagnosed by '''[[ECG]]'''. The ECG shows a '''fast heart rate with wide and bizarre QRS complexes''' and '''P waves that are not consistency related''' to the QRS complexes. QRS complexes can be '''monomorphic''' (similar in appearance with a regular R-R interval) or '''polymorphic''' (variable appearance and irregular R-R interval). A polymorphic appearance is suggestive of a more unstable myocardium. The P-P interval should be regular.
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| − | Sustained Ventricular Tachycardia lasts for more than 30 seconds, unsustained VT lasts less than thirty seconds.
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| − | | |
| − | ===Treatment===
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| − | '''Exercise''' should '''not''' be continued whist the horse has VT.
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| − | If the cause is thought to be idiopathic then '''box-rest''' and '''steroids''' are the treatment of choice. Otherwise the treatment options are:
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| − | *Procainamide (in the conscious horse) or lidocaine (in the unconscious horse)
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| − | *Quinidine Gluconate
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| − | *Magnesium Sulfate supplementation
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| − | ===Prognosis===
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| − | VT can progress to a '''fatal arrhythmia''' (ventricular fibrillation). Prognosis depends on the underlying cause of the arrhythmia and the success of its treatment.
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| − | {{Learning
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| − | |Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis02646.asp Ventricular tachycardia]
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| − | |flashcards = [[Small Animal Emergency and Critical Care Medicine Q&A 02]]
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| − | }}
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| − | ==References==
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| − | Dennis, S (2011) '''Ventricular arrhythmias''' RVC Cardiology Elective Course, ''Royal Veterinary College''
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| − | Menzies-Gow, N (2001) '''ECG interpretation in the horse''' ''In Practice 2001 23: 454-45''
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| − | RVC staff (2009) '''Cardiovascular System''' RVC Intergrated BVetMed Course, ''Royal Veterinary College''
| + | '''Large Animals''' |
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| | + | *Digitalis |
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| − | {{review}}
| + | *Quinidine Sulfate |
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| − | ==Webinars==
| + | *Magnesium Sulfate supplementation (used in horses) |
| − | <rss max="10" highlight="none">https://www.thewebinarvet.com/cardiology/webinars/feed</rss>
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| − | [[Category:Altered Ventricular Impulse Formations]] | + | [[Category:Altered Ventricular Impulse Formations]][[Category:To_Do_-_Cardiovascular]] |
| − | [[Category:Expert Review]] | + | [[Category: To Do - Siobhan Brade]] |
| − | [[Category:Cardiology Section]] | |
Introduction
Ventricular tachycardia is a rhythm disturbance that produces a rapid, regular heart beat caused by continuous ventricular premature complexes (VPCs). It is a serious condition which has the capability of causing ventricular fibrillation and ultimately death. It is most likely to occur secondary to an existing abnormality in either the heart or the rest of the body.
It is particularly common in Dobermanns secondary to Dilated Cardiac Myopathy.
Causes
Significant myocardial damage to the heart or disease in other systems, Drug reactions, Hypoxia, Anaemia, Electrolyte and acid-base disturbances, etc.
Clinical Signs
On cardiac auscultation, heart rate is abnormally high and irregular. The dog may present collapsed and have signs of output failure.
Diagnosis
The condition can be diagnosed by ECG. The ECG shows wide and irregular QRS complexes, and P waves without QRS complexes following.
Treatment
The underlying cause should be identified and treated where possible.
Small Animals
Dog: lidocaine (1st line of treatment), quinidine or procainamide (2nd line of treatment)
Cat: propranolol (1st line of treatment), small dose of lidocaine (2nd line of treatment)
Large Animals
- Magnesium Sulfate supplementation (used in horses)