2. Introduction Paroxysmal SVT is a common arrhythmia in the emergency room, outpatient clinic and EP laboratory. Quality of life of patients suffering from PSVT is frequently poor. Non paroxysmal SVT is less frequent. Tachycardiomyopathy with LVSD results from incessant SVT – usually reversible after permanently abolishing the arrhythmia. AVNRT – young,no heart disease,AT – structural or pulmonary. Patients >55yrs can have spontaneous cure or death due to HF. Can be usually cured by catheterablation techniques. Surgery has no role today in treatment of SVT . Incidence is 35 cases /1,00,000 person/year. Prevalence is 2.25/1000 …
5. REENTRY circuit Reentry occurs when a propagating impulse fails to die after normal activation of the heart and persists to excite the heart after expiration of the refractory period. The circuitous propagation of an impulse around an anatomic or functional obstacle leading to the reexcitation of the heart describes a circus movement reentry. Continous circulating excitation.
6. CRITERIA for REENTRANT CIRCUIT to occur( MINES and GARREY ) An area of unidirectional block must exist. The excitatory wave progresses along a distant pathway ,returning to its point of origin and the following the same path again. Interruption of the reentrant circuit at any point along its path should terminate the circus movement.
7. TYPES OF REENTRANT CIRCUIT Four distinct models of reentry have been described: 1.The ring model 2.The leading circle model 3.The figure of eight model 4.The spiral wave model. Ring model -- an anatomical obstacle is required. Others --- functional obstacle Functional – VF due to MI,brugadasyndrome.LQTS.
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12. ENHANCED AUTOMATICITY It is due to the subsidiary pacemakers taking the role of giving impulses when the SAnode is inactive or degenerated. Pacing does not provoke.
13. TRIGGERED ACTIVITY It is due to EAD of the phase 3,LAD of phase 4 of action potential. Attributed to an increase in intracellular calcium accumulation It is due to the increased catecholamines,adrenergic drive. Seen in postoperative cases.. Subsides on removal of the stimulus or cause. EAD –TDP LAD – atrial,junctional,fasicular ,catecholamine sensitive VT Can be provoked by pacing
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15. SUPRAVENTRICULAR TACHYCARDIA Supraventricular tachycardia is any tachycardia that originates in the atria or that uses the atrium or AVjunction and that requires the participation of the tissue above the bifurcation of the bundle of HIS for propagation as a critical component of the tachycardia circuit….CRAWFORD SVT – include all tachyarrhythmias that either originate from or incorporate supraventricular tissue in a reentrant circuit…HURST
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17. TERMS PAROXYSMAL – one with sudden onset and termination and which is recurrent. PERSISTENT – the one which exists and terminates with treatment. INCESSANT– the one that continues without stopping on itself. PERMANENT –which persists despite treatment –refractory,chronic PREEXCITATION – activation of the part of ventricle by an anomalous connection before it is depolarised by the normal AV conducting system. RECIPROCATING – same time existant one being active other being refractory during conduction of an impulse.
18. TACHYCARDIAS due to reentry circuits are usually paroxysmal,rarelyincessant.they occur in normal hearts. Those due to automaticity,triggered activity are persistent and have phenomenon of warm up . They occur in the background of structural heart disease. Physiological sinus tachycardia has gradual onset and termination
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20. Approach to a patient With Narrow QRS complex TACHYCARDIA
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22. STEP wise Look for QRS duration. QRS complex regular/irregular. Then look for presence of p waves. P waves morphology P waves and QRSrelationship 1:1 AVblock present. QRS alternation Termination initiation of tachycardia. Effect of BBBon tachycardia cycle length.
26. In brief from the diagram clues Response to carotid sinus massage or adenosine –with termination of arrhythmia with Pwave –AVNRT with atrial premature beat . Termination with QRS complex –ventricular reciprocating rhythm. Tachycardia persists with AV block –AT,AFL,SANRT Pseudo r ‘ wave in V1 –AVNRT SHORT RP interval – AVNRT,AVRT Long RP interval – AT,SANRT,AVNRT atypical
36. AVNRT Presence of a narrow complex tachycardia with regular R-R intervals and no visible p waves. P waves are retrograde and are inverted in leads II,III,avf. P waves are buried in the QRS complexes –simultaneous activation of atria and ventricles – most common presentation of AVNRT –66%. If not synchronous –pseudo s wave in inferior leads ,pseudo r’ wave in lead V1---30% cases . P wave may be farther away from QRS complex distorting the ST segment ---AVNRT ,mostly AVRT.
44. AVRT Typical – RP interval < PR interval RP interval > 80 milli sec Atypical –RP interval > PR interval Concealed bypass tract – only retrograde conduction Manifest bypass tract– both anterograde and retrograde. Electrical alternans –the amplitude of QRS complexes varies by 5 mm alternatively. Rate related BBB occuring and the rate of tachycardia is decreasing –then the bypass tract is on the same side of the block.
49. WPW syndrome Two types Orthodromic Antidromic Antidromic is wide complex tachycardia In NSR detected by delta wave. Can ppt into AF and VF on use of AV nodal blockers MEMBRANE ACTIVE ANTIARRHTYHMIC DRUGS are safe. CONCEALED WPW syndrome – no delta wave .less risk of AF
56. Focal Atrial Tachycardia P wave morphology changes. PR interval > 0.12 sec . Second,third degree AV block can occur. Tachycardia terminates with a qrs complex .. Right atrial origin– p wave inverted in V1. If biphasic in V1—initially positive then negative. Upright in lead AVL Opposite if of left atrial origin Superior origin –upright p waves in inferior leads Inferior origin –p waves are inverted in inferior leads.
59. Multifocal Atrial Tachycardia At least three consequtive p waves with different morphologies with a rate > 100 bpm to be present. Isoelectric baseline between p waves. Also called as choaticatrial tachycardia Mostly seen in COPD ,electrolyte abn,theophylline Rate usually does not exceed 130-140 bpm.
61. SANRT Microreentrant tachycardia Usually precipitated and terminated by premature atrial complexes. Atrial rate is usually 120-150 bpm. IART - Large or small reentrant circuit. AV block can occur.
62. Junctionaltachycardias Non paroxysmal – accelerated junctional rhythm Rate < 100 bpm Usually junctional node 40-60 bpm Paroxysmal or focal junctional tachycardia is rare –automaticity. 110-250bpm. P waves may be before or after QRS complex Infrequent and nonsustained episodes –no treatment Acute termination of SVT and establish the mechanism of SVT in case of acute setting. Long term goal is abolishing the arryhthmia substrate. Precipitating factors – electrolyte imbalance,hypoxia,ischemia,hyperthyroidism to be sought out.
64. A 12 lead ECG during tachycardia and NSR. No delay in therapy if the mechanism of SVT is not known. Perform CAROTID SINUS MASSAGE,or give 6mg bolus adenosine. In case of severe hemodynamic compromise a synchronisedcardioversion to be given.
65. Carotid sinus massage Check for carotid bruit before massage. At the level of cricoidcartilage,at the angle of mandible the carotid sinus is situated. Gentle pressure is applied over the carotid sinus for 5 -10 seconds. ECG recording to be present. In case of no response – try on the other side. Simultaneous pressure not to be applied both sides. Alternative manuevres are valsalva,gagreflex,ice water pouring over the face.
66. If SVT is suspected to be AVNode dependent – drug of choice is adenosine and CCBs verapamil and diltiazem. Useful for sustained cases of AV node independent tachycardias. But digoxin,BBs,CCBs better control of ventricular response in atrialtachycardias Class I agents to be combined with AV nodal blocking drugs – to eliminate 1:1 conduction of atrial to ventricles.
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69. Pharmacologic Agents for Short-Term Treatment of Supraventricular Tachycardia (SVT). Delacrétaz E. N Engl J Med 2006;354:1039-1051.
75. Pill in the pocket approach In whom recurrences are infrequent. But sustained.well tolerated hemodynamically. Patients who have had only a single episode of SVT.. 100-200mg of flecainide at the onset of SVT is a reasonable approach…until he reaches the hospital. 40-160 mg verapamil –without preexcitation, Betablockers Propafenone 150-450 mg. 80% cases interrupted with a combination of CCBand BB in 2 hrs…
76. Long term control of SVT Frequency and severity of episodes. LVF Cost benefits of radiofrequency ablation over the pharmacotherapy . Pharmacotherapy is considered in patients who defer catheter ablation,whom in which ablation failed,or carries a risk of AV block. Multifocal atrial tachycardia Trial and error Accessory pathway – class Ia,Ic,III AV node blocking drugs Young patients – Ia drugs Class I agents LVD < 35% not used.
77. Catheter guided Radiofrequency Ablation Several multipolar catheters are introduced High right atrium ,bundle of his ,RVapex,Coronary sinus. Radiofrequency is delivered at the site of earlier activation Success is defined by elimination of the tachycardia or loss of pre excitation. 90-98% success in AV node dependent 60-80% in case of AV node independent. Cryoablation more useful…
79. Pacemakers Temporary role in case of digoxin toxicity. Permanent in case of long term control To terminate the tachycardia Revert into sinus rhythm Prevent the occurrence. Overdrive suppression RF induced atrial pacing are used No role of surgery presently in PSVT rx .
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81. Some important points Rxof PSVT given for patient comfort except in IHD,MS When the QRS complex is wide and VT is mistaken as SVT with ABERRANT conduction IV verapamil – not recommended decreases BP. If DC cardioversion to be avoided because of possible adverse response to digitalis adm …pacing Rt atrium and ventricle via temp pacing. In WPW syndrome avoid VERAPAMIL,LIDOCAINE . Avoid digoxin. In SANRT ,IART –class IA,IC ,BB SANRT –digoxin.
82. Cont… Rx of ectopic atrial tachycardia – consider digitalis toxicity,chronic lung disease,metabolicabn,electrolyteabnormalities,acute MI ----temporary pacing. Unsuccessful is EC Removal or reversal of inciting factor Surgical excision of focus. Rx of MAT –chronic lung disease,metabolic,rare is digitlais toxicity ---CCBS,BBs ..no role of cardioversion,devices ,surgery.
94. Special problems 1.Coexisting Double Tachycardias May not be identified during noninvasive testing ..needs EP study. Ex—typical AVNRT and AT. Concentric –eccentric –concentric. AVNRT –both APC,VPC AT only APC 2.Pseudo AF- infrequent presentation of PSVT. Occurs during onset and termination of tahcycardia. Multiple accessory AV pathways. In young who have AF without other risk factors. 5% of AVNRT. Group beating is seen
