approch narrow complex tachycardia

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SUPRAVENTRICULAR TACHYCARDIA

APPROACH TO NARROW QRS COMPLEX TACHYCARDIADr Dharam Prakash SaranSTEP wiseLook for QRS duration.QRS complex regular/irregular.Then look for presence of p waves.P waves morphologyP waves and QRS relationship 1:1AV block present.Termination initiation of tachycardia.Effect of BBB on tachycardia cycle length.

In brief from the diagram cluesResponse to carotid sinus massage or adenosine with termination of arrhythmia with Pwave AVNRTTachycardia persists with AV block AT,AFL,SANRTPseudo r wave in V1 AVNRT SHORT RP interval AVNRT,AVRTLong RP interval AT,SANRT,AVNRT atypical

ECG findings

Differentiation of AVNRT from AVRT

AVNRTPresence 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.AV NODAL REENTRANT TACHYCARDIA

Figure 2. Diagram of AV nodal reentrant tachycardia (AVNRT). The electrical impulse travels in a circle using extra fibers in and around the AV node.

AVRTTypical RP interval < PR intervalRP interval > 80 milli secAtypical RP interval > PR intervalConcealed bypass tract only retrograde conductionManifest 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.AV REENTRANT TACHYCARDIA

Figure 3. A diagram of AV reentrant tachycardia (AVRT). The electrical impulse travels down the AV node to the ventricles and back to the atrium via extra fibers that connect the atria and ventricles.

PRinterval RP intervalPR interval

WPW syndrome

Two typesOrthodromicAntidromicAntidromic is wide complex tachycardiaIn NSR detected by delta wave.Can ppt into AF and VF on use of AV nodal blockersMEMBRANE ACTIVE ANTIARRHTYHMIC DRUGS are safe.CONCEALED WPW syndrome no delta wave .less risk of AF

Focal Atrial TachycardiaP 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.Upright in lead AVL Opposite if of left atrial originSuperior origin upright p waves in inferior leadsInferior origin p waves are inverted in inferior leads.

Multifocal Atrial TachycardiaAt least three consequtive p waves with different morphologies with a rate > 100 bpm to be present.Isoelectric baseline between p waves.Also called as choatic atrial tachycardiaMostly seen in COPD ,electrolyte abn,theophyllineRate usually does not exceed 130-140 bpm.

Multifocal Atrial Tachycardia

SANRTMicroreentrant tachycardiaUsually precipitated and terminated by premature atrial complexes.Atrial rate is usually 120-150 bpm.AV block can occur.Junctional tachycardiasNon paroxysmal accelerated junctional rhythmRate < 100 bpm Usually junctional node 40-60 bpmParoxysmal or focal junctional tachycardia is rare automaticity.110-250bpm.P waves may be before or after QRS complexInfrequent and nonsustained episodes no treatmentAcute termination of SVT 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.

TREATMENT OF SVTA 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 synchronised cardioversion to be given.Carotid sinus massageCheck for carotid bruit before massage.At the level of cricoid cartilage,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,gag reflex,ice water pouring over the face. If SVT is suspected to be AVnode dependent drug of choice is adenosine and CCBs verapamil and diltiazem.But digoxin,BBs,CCBs better control of ventricular response in atrial tachycardiasClass I agents to be combined with AV nodal blocking drugs to eliminate 1:1 conduction of atrial to ventricles.

DRUGDOSESIDE EFFECTSAV NODAL BLOCKERSADENOSINE6-12 mg bolusFlushing ,dyspneaChest painVERAPAMIL0.15 mg/kg over 2 minHypotension bradycardiaDILTIAZEM0.25-0.35 mg/kg -2 minsameDIGOXIN0.5-1.0 mg --- 2-10 minDigoxin toxicityPROPANOLOL1-3mg over I min Hypotension bradycardiaCLASS I AADQUINIDINE6-10MG/KG at 10 mg/minhypotensionPROCAINAMIDE10-15mg/kg at 50 mg/minhypotensionDISOPYRAMIDE1-2 mg/kg at 10 mg/minhypotensionPROPAFENONE1-2mg/min at 10 mg/minBradycardia,GI disturbanceFLECAINIDE2 mg/kg at 10 mg/minBradycardia,dizzinessCLASS IIISOTALOL1-1.5mg/kg at 10 mg/minHypotension,proarrythmicAMIODARONE1.5 mg/kg during 15 minHypotension,bradycardia

Algorithm for Short term management of SVT

41Figure 3. Algorithm for the Short-Term Management of Supraventricular Tachycardia (SVT).If the diagnosis of SVT with aberration or SVT with preexcitation is not certain, tachycardia with a wide QRS complex must be considered as an unknown mechanism and treated as such. SVT with preexcitation can be the result of either antidromic atrioventricular reentry or, uncommonly, another type of SVT (e.g., atrial tachycardia) with an accessory pathway that is not critical for the maintenance of the arrhythmia. BBB denotes bundle-branch block, VT ventricular tachycardia, IV intravenous, and ECG electrocardiogram. Adapted from Blomstrom-Lundqvist et al.8

Algorithm for long term Management of SVT42Figure 4. Algorithm for the Long-Term Management of Supraventricular Tachycardia.In many circumstances, patient preference is an important consideration in the selection of therapy. Referral to an electrophysiologist should be considered for discussion of the risks and benefits of catheter ablation.

Pill in the pocket approachIn 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 approachuntil he reaches the hospital.40-160 mg verapamil without preexcitation,BetablockersPropafenone 150-450 mg.80% cases interrupted with a combination of CCBand BB in 2 hrs

Long term control of SVT Frequency and severity of episodes.LVFCost 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, Accessory pathway class Ia,Ic,IIIAV node blocking drugsYoung patients Ia drugsClass I agents LVD < 35% not used.

Adenosine

not to be used in bronchospastic pulmonary disease.Adenosine precipitates asthmaGiven rapidly in 1-2 sec.If given by peripheral vein uplift the arm..Max dose is 30 mg6- 12-12 mg Terminates AVNRT .AFL with 2:1 blockPotentiated by dipyradimole,carbamazepine decrease dose to 3 mg. Other drugsCalcium channel blockers,beta blockers ,digoxin are the next drugs to be used if not responded to adenosineUsually 60 % cases respond to a dose of 6 mg and 95 % cases at 12 mg.Type 1 a AAD, 1c,iii,AMIODARONE in refractory cases.Beta blockers not to used IV in heart failure.Long term treatment in case of recuurent episodes,hemodynamic instability.Catheter guided Radiofrequency AblationSeveral multipolar catheters are introducedHigh 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

Catheter Ablation of Cardiac Arrhythmias.49Figure 5. Catheter Ablation of Cardiac Arrhythmias.One to four catheter electrodes are introduced into the cavities of the heart through femoral (or, alternatively, internal jugular or subclavian) venous access after local anesthesia is administered. Radiofrequency current a low-voltage, high-frequency (500 kHz) form of electrical energy used for electrocautery in surgery is delivered through a catheter electrode to create small lesions through thermal injury in the myocardial tissue, the conduction system, or both, which have been identified as critical for mediating the cardiac arrhythmia. In patients with arrhythmias mediated by an abnormal accessory pathway, the catheter is positioned so that it is in contact with the pathway, and the application of radiofrequency current blocks conduction over the accessory pathway within a few seconds. For left-sided accessory pathways, a retrograde approach through the femoral artery and the aortic valve can be used. Alternatively, a transseptal puncture can be performed to gain access to the left atrium. Cryothermal ablation is an effective approach in patients with atrioventricular (AV) nodal reentrant tachycardia or an accessory pathway close to a His bundle because of the reversibility of the initial effect and the negligible risk of AV block. Most ablation procedures take one to three hours. Catheter ablation of supraventricular tachycardia can be performed as a one-day outpatient procedure, or it may require overnight hospitalization. Treatment with aspirin is often recommended for several weeks after ablation that has been performed in the left side of the heart to reduce the potential

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