Tachycardia classification

According to ECG width:
A narrow complex tachycardia (NCT) , (QRS<120 msec) reflects rapid activation of the ventricles via the normal His-Purkinje system (supraventricular tachycardia).
• A widened QRStachycardia (WCT) (≥120 msec) occurs when ventricular activation is abnormally slow.

According to stability:
Unstable (1- syncope or change in mental status 2- chest pain 3- heart failure 4- shock)
• Stable (no above sign)

Clinical challenge with the wide QRS tachycardia:
1- Diagnosing the arrhythmia is difficult
2- Urgent therapy is often required

 

General management

Confirm if the patient is stable or unstable? :  Check vital sign and level of consciousness to determine patient are stable or unstable.

During these period other should :

  • Administer supplemental oxygen
  • Establish intravenous access
  • Send blood for appropriate initial studies
  • Attach the patient to a continuous cardiac monitor
  • Obtain a 12-lead electrocardiogram (ECG)
  • If patient is in cardiac arrest follow the cardiac arrest algorithm

If patient is in cardiac arrest (unresponsive and no pulse and breathing) :

  • Start CPR from chest compression (30:2 )
  • Apply AED to the patient.
  • check the rhythm if VT and VF give unsynchronized DC shock (150-200 J Bi phasic and 360 J monophasic)
  • Start the CPR (30:2) for 2/min.
  • If  still in VF and VT give again unsynchronized DC shock and start CPR 30:2 for 2minute.
  • Check rhythm if VF and VT after 3 shock give 1mg adrenalin IV and 300mg amiodarone.
  • Continue adrenaline every 3 to 5 minute.
  • Repeat the cycle of CPR till the perfussing rhythm establish.
  • If there was no response think about 4H and 4T.{hypothermia , hyperkalemia/hypokalemia , hydrogen Ione excess (acidosis) , hypovolemia , tamponade , tension pneumothorax , toxic (drug and poisoning) , trauma}
  • If WCT give  120-200 J synchronized cardioversion
  • If  NCT give  100 j synchronized cardioversion
  •  Don’t forget sedation (Propofol or midazolam)
  • If first EC don’t respond upward titration dose of EC.
  • If second EC was unsuccessful give adrenaline 1mg and third EC was unsuccessful give 300mg amiodarone in 10-20/ min.(1)

 

Stable patients with uncertain WCT etiology

• You can spent time and attempting to determine the diagnosis.
• If the initial diagnosis of WCT was made from a single-lead rhythm strip, a full 12-lead ECG should be obtained.
• A trial of vagal maneuvers and/or pharmacologic intervention (may be diagnostic).
• It is important to determine if the rhythm is regular or irregular.

Causes of Regular wide QRS tachycardia:

  • Sinus tachycardia with (aberrancy)
  • Atrial tachycardia with aberrancy
  • Atrial flutter with aberrancy (in some cases)
  • AV nodal reentrant tachycardia with LBBB
  • Antidromic  AV reentrant tachycardia
  • Monomorphic VT
  • Tachycardia in patient with pacemaker and ICD (may sometime irregular)(2)

Hemodynamically stable patients with WCT which is regular and monomorphic in whom the etiology of the WCT remains uncertain:

  • Perform vagal maneuver
  • Administer adenosine (6 and then 12mg) , effect is like vagal maneuver
  • Avoidance other pharmacologic agent (Beta blocker, Ca channel blocker, Digoxin)
  • Further treatment is directed to the result of vagal maneuver and adenosine and may to VT. (3)
  • Synchronized electrical cardioversion

The effect of adenosine and vagal maneuver on different tachycardia:

  •  Sinus tachycardia gradually slow and reappeared at the end.
  • Atrial tachycardia or atrial flutter, the ventricular rate will decrease and flutter waves will appear.
  • A PSVT (either AVNRT or AVRT) will frequently terminate (dependence on the AV node).
  • VT is generally unaffected.
  •  But some time right ventricular out flow tract VT respond to adenosine.
  • If after adenosine administration Ventricular rate don’t change , WCT is likely VT. (exception : wrong administration of adenosine)
  • If ventricular activity   temporarily become slow the flutter wave and other atrial is typically easily seen and the diagnosis confirmed.
  • The second dose 12mg adenosine is appropriate in in known SVT but not in unknown WCT. (third dose not advised right now)(3)

 

Stable patient with known WCT etiology

VT should be suspected in : AV dissociation, QRS concordance , right superior axis (axis shift from baseline more than 40 degree), patient with structural heart disease

SVT should be suspected in : Young patient without structural heart disease and without historical (family history of sudden cardiac death). Physical & ECG criteria supporting VT are not present.(3)

The causes of WCT with irregular rhythm : AF with LBBB, AF with pre-excitation conduction, Atrial flutter with variation and aberrancy, Polymorphic VT

The best approach for WCT and irregular rhythm from unknown etiology is electric cardioversion (special in unstable patient). All patients with WCT and irregular rhythm need cardiologist consultation to confirm the diagnosis and best approach.
In patient with WCT and hemodynamic stable from unknown etiology don’t administer amiodarone and other AV blocker (the best choice is procainamide in this condition)(3)


Approach to patient with known Ventricular tachycardia: Determine if the patient is stable or unstable. For stable patient we can choose between pharmacologic cardioversion or electric cardioversion. (D<E)

    Electrical cardioversion :

  • Administer IV analgesic, sedation (concern is hemodynamically unstable)
  •  If QRS complex and T wave can be distinguished perform synchronized electrical cardioversion 100 J (Bi or monophasic)
  •  If QRS and T wave cannot be distinguished perform unsynchronized electrical cardioversion 120 to 200 J Bi and 360 j with monophasic.

    If pharmacologic approach is the chosen :

  • Amiodarone 150 mg IV/10m flowed with 1mg/m for next six hour.
  • Procainamide 20 – 50 mg / m till arrhythmia terminate or a maximum dose of 17mg/kg (these drugs cause hypotension and may patient need for EC)
  • Any associated conditions should be treated (ischemia , CHF , electrolyte imbalance)
  • AED should be ready in all stage of management to use it if the patients become deteriorate.

    If SVT is AVNRT or AVRT or if the specific SVT is uncertain the following treatment is advised : 

  • Vagal maneuver
  • Adenosine (if vagal maneuver failed) – 6mg if not respond repeat one single dose 12mg.
  • In patient with central catheter the initial dose should not exceed 3mg and may be as little as 1mg.
  • It stops the AVNRT and AVRT and will slow the rhythm of atrial flutter and AF and establish the diagnosis of Supraventricular. 
  • Ca channel blocker or beta blocker (verapamil 2.5mg IV or diltiazem 5-20mg IV or metoprolol 5 to 10mg IV)
  • Ca channel blocker and beta blocker will terminate AVRT, AVNRT as well as some atrial tachycardia and will slow the rate and determine if there be AF and Atrial flutter.
  • Cardioversion: for SVT it is rarely necessary.
  • If the rhythm is AF, atrial flutter chose between  rhythm control , rate control and do anticoagulation.(3)

 

Patient with pacemaker and tachycardia

Patient with pacemaker are prone to WCT like patient without pacemaker. Rarely WCT can result from pacemaker tracking an underlying atrial arrhythmia. Or due to pacemaker mediated tachycardia. Most patients with pacemaker and WCT have stable condition.(3)

If the WCT is due to the function of pacemaker :

  • The appropriate treatment is placement a magnet over the pacemaker will terminate the WCT.
  • The magnet will disable all pacemaker sensing and terminate the ability to track atrial impulses.
  • With magnet the pacemaker will function in an asynchronous , fixed-rate mode (VOO or DOO).
  • In this situation there will be pacemaker stimuli that don’t sense P wave or QRS complex with a fixed rate ( lower rate limit of the pacemaker).
  • If WCT is due to PMT or pseudo PMT (non reentrant repetitive VA synchrony) transient magnet application will terminate the WCT and sinus rhythm will ensue when the magnet removed.
  • If WCT is due to inappropriate tracking of atrial fibrillation and atrial flutter the WCT will likely resume once magnet is removed.(3)

Patient with ICD :

  • Patient with ICD (primary and secondary) and WCT are at high risk for VT.
  •  All patients with ICD and WCT should be treated as VT until proven otherwise.
  • If ICD therapy is not possible (lake of equipment, personal, or patient instability) the initial management should proceed as if no ICD were present.(3)

The reason of WCT in patient with ICD :

  • In patient with a persistent or recurrent WCT may the ICD has reach the limit of programmed therapies. (VT storm with an underlying trigger like ischemia and hypokalemia or SVT with aberrancy which recurs or persist in spite of the ICD therapies.
  •  Patient with ICD and WCT will not receive therapy from the ICD if the WCT rate is lower than the programmed rate for ICD therapy.
  • Multiple shock from ICD without tachycardia most likely have device malfunction. (most likely from lead malfunction).

ICD malfunction can manage with magnet application and the WCT can temporarily suspended and prevent further deterioration. Magnet application is also recommend for patient receiving shock for narrow complex tachyarrhythmia. ICD with endovascular right ventricular can not sense and track atrial rhythm and not subject of WCT.  (Only ICD with atrial and ventricular lead cause WCT). Magnet application asynchronous pacing in ICDs and will therefore not terminate PMT in patient with ICD. (3)

 

Recurrent or refractory WCT

Recurrent or refractory WCT need pharmacologic intervention and further evaluation for arrhythmia triggers (ischemia , electrolyte imbalance and drug toxicity)
Amiodarone is the most effective agent for treatment of recurrent or refractory WCT particularly VT.
Amiodarone (150mg/10 minute followed by 1mg/minute for six hour and then 0.5mg/minute for an additional 18 hours or longer). Repeated boluses can be administered if necessary.
Procainamide is an alternative to amiodarone (15 to 18mg/kg as slow infusion over 25 to 30 minute followed by 1-4mg/minute by continuous infusion.
Procainamide suppress conduction over a bypass tract, and is recommended if Antidromic AVRT or an SVT conducting over a bypass tract is suspected.
For pre-excitation atrial fibrillation and atrial flutter intravenous procainamide or ibutilide is recommended, amiodarone and AV blocking agent not recommended.
For patient with a known SVT that recurs or persists , intravenous verapamil , diltiazem or beta blockers may be used.(3)

Chronic management :

  • VT : all patient with VT should undergo ICD implantation.
  • If patient with ICD have recurrent symptomatic VT or those who have received multiple ICD therapies may need antiarrhythmic agent.
  • In some cases radiofrequency catheter ablation may be an option.
  •  Idiopathic VT is treated with ablation or pharmacologic therapy, not with ICD.
  • AVNRT or reciprocating tachycardia (AVRT) with concealed accessory path may require no therapy (self-terminate arrhythmia with vagal maneuvers) , may pharmacologic therapy, or may need catheter ablation.
  • Patient with AV reciprocating tachycardia with a manifest accessor pathway or pre-excited atrial fibrillation or atrial flutter (patient with arrhythmia related to WPW ) should undergo for EP study and catheter ablation. (small risk of sudden cardiac death in patient with symptomatic WPW syndrome.
  • The approach to a patient with atrial fibrillation include ventricular rate control , rhythm control and or catheter ablation.(3)

 

Bibliography

1. Mark S. Link, Chair, et al., et al.Adult Advanced Cardiovascular Life Support ,2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Dallas, Greenville Avenue,, USA : s.n., december 4, 2015.
2. Robert W. Neumar, Charles W. Otto, Mark S. Link, Steven L. Kronick, Michael Shuster, Clifton et all.Part 8: Adult Advanced Cardiovascular Life Support: 2010 American Heart Association,. Dallas, Dallas, 7272 Greenville Avenue : Circulation , 2010. Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care.1524-4539.
3. leonard I Ganz, MD,FHRS,FACC.UPTODATE. [Online] OCTOBER 22, 2015. [Cited: 0CTOBER 8, 2016.] WWW.UPTODATE.COM.

 

 

Dr Mohammad Naseem Saba MD Consultant Cardiologist, Head of Thoracic medicine of Late Sardar Mohammad Dawod Khan Hospital, Kabul Afghanistan