polymorphic ventricular tachycardia 2023
Ventricular tachycardia is a potentially lifethreatening cardiac arrhythmia.If the rate is very fast, hemodynamic deteriorationcan occur rapidly.On the ECG, ventricular tachycardia can bedefined as three or more ventricular ectopicbeats occurring in a sequence at a rate morethan 100 per minute.Ventricular tachycardia which gets spontaneouslyterminated within 30 seconds is called nonsustained ventricular tachycardia (NSVT).Sustained ventricular tachycardia is one whichdoes not get spontaneously terminated within30 seconds or needs cardioversion before thatdue to hemodynamic compromise.Based on the morphology, ventricular tachycardiacan be classified into monomorphic and polymorphicventricular tachycardias.Monomorphic VT is usually due to reentrantcircuits within the myocardial conductiontissue, while polymorphic VT is due to earlyafterdepolarizations.Classical example of polymorphic ventriculartachycardia is torsade de pointes associatedwith congenital or acquired QT interval prolongation.Another rare form of ventricular tachycardiais bidirectional ventricular tachycardia.Monomorphic ventricular tachycardia is usuallytreated with an amiodarone bolus dose followedby infusion.Monomorphic ventricular tachycardia in thesetting of acute myocardial ischemia can alsobe treated by intravenous lignocaine bolusfollowed by infusion.
Predisposing causes for ventricular tachycardialike ischemia and electrolyte imbalance hasto be treated simultaneously to prevent recurrence.Ventricular tachycardia not responding topharmacotherapy and those having hemodynamiccompromise at presentation need direct currentcardioversion after appropriate sedation.Monitor screen shot showing ventricular tachycardiaand restoration of sinus rhythm followingcardioversion with a direct current shock.Chronic recurrent monomorphic VT like fasciculartachycardia and right ventricular outflowtract tachycardia are also amenable to electrophysiologicalmapping and ablation.Recurrent ventricular tachycardia in spiteof radiofrequency catheter ablation needsan implantable cardioverter defibrillator.Those at risk of recurrent VT with previousmyocardial infarction and left ventriculardysfunction also need an implantable defibrillator.
Polymorphic VT is managed by intravenous magnesiumand measures to increase heart rate like pacingas it occurs most often in the setting ofbradycardia and QT interval prolongation.Associated hypokalemia which is often presenthas to be corrected.Offending drug has to be withdrawn in caseof drug induced polymorphic VT.Recurrent polymorphic VT in the setting ofcardiac channelopathies or primary electricaldisorders of the heart need implantation ofa cardioverter defibrillator as response topharmacotherapy is often poor.Beta blockers are needed in addition, formost persons with congenital long QT syndrome.Some of the polymorphic VTs in Brugada syndromemay be prevented by quinidine, though implantationof a defibrillator cannot be avoided by thismethod.
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