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• narroe complex ventricular tachycardia should be included in the differential diagnosis
  oscar,m jolobe
  Published on: 8 July 2020

• Published on: 8 July 2020

  narroe complex ventricular tachycardia should be included in the differential diagnosis

  • oscar,m jolobe, retired geriatrician manchester medical society

  For the sake of completeness, the approach to narrow complex tachycardia(1), and the differential diagnosis of that disorder, should also include the entity of fascicular ventricular tachycardia, in which the duration of the QRS complex does not exceed 120 ms during ventricular tachycardia(VT)(2)(3). There are 3 subtypes, namely, left posterior fascicular VT with right bundle branch(RBBB) morphology and left axis deviation, left anterior fascicular VT with RBBB pattern and right axis deviation, and upper septal fascicular VT with a narrow QRS and normal axis configuration(2).
  Talib et al evaluated 10 patients aged 14-66 with upper septal ventricular tachycardia in whom there was no structural heart disease, and in whom the QRS duration amounted to < 120 ms during VT. In 8 instances VT could be terminated by administration of verapamil. In the other 2 instances no attempt had been made to terminate the episodes of VT with that drug. In the verapamil-responsive subjects, the episodes of VT were characterised by QRS duration amounting to 75 ms, 90 ms(two patients), 93 ms, 96 ms, 105 ms, 115 ms, and 118 ms, respectively. In 4 patients precordial QRS configuration during VT was identical to QRS configuration during sinus rhythm. In the other four, QRS configuration was of the RBBB subtype during VT(3).
  Narrow complex VT can also be a manifestation of coronary artery disease, but, in this context, there appears to be no involvement of the His-Purki...

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  For the sake of completeness, the approach to narrow complex tachycardia(1), and the differential diagnosis of that disorder, should also include the entity of fascicular ventricular tachycardia, in which the duration of the QRS complex does not exceed 120 ms during ventricular tachycardia(VT)(2)(3). There are 3 subtypes, namely, left posterior fascicular VT with right bundle branch(RBBB) morphology and left axis deviation, left anterior fascicular VT with RBBB pattern and right axis deviation, and upper septal fascicular VT with a narrow QRS and normal axis configuration(2).
  Talib et al evaluated 10 patients aged 14-66 with upper septal ventricular tachycardia in whom there was no structural heart disease, and in whom the QRS duration amounted to < 120 ms during VT. In 8 instances VT could be terminated by administration of verapamil. In the other 2 instances no attempt had been made to terminate the episodes of VT with that drug. In the verapamil-responsive subjects, the episodes of VT were characterised by QRS duration amounting to 75 ms, 90 ms(two patients), 93 ms, 96 ms, 105 ms, 115 ms, and 118 ms, respectively. In 4 patients precordial QRS configuration during VT was identical to QRS configuration during sinus rhythm. In the other four, QRS configuration was of the RBBB subtype during VT(3).
  Narrow complex VT can also be a manifestation of coronary artery disease, but, in this context, there appears to be no involvement of the His-Purkinje system, although the underlying mechanism has yet to be fully elucidated(4). In the latter example, a 54 year old man had a previous history of ST segment inferior myocardial infarction characterised by right coronary artery occlusion. One month later he experienced an episode of tachycardia (ventricular rate 140 beats/min) characterised by QRS duration amounting to 120 ms and atrioventricular dissociation(4).
  Of all the patients with narrow complex VT the ones most likely to be confused with supraventricular tachycardia are the ones described by Talib et al, in whom QRS duration amounted to < 120 ms during VT. In some of those patients diagnostic confusion would have been compounded by the fact that QRS configuration was the same during sinus rhythm and VT. In those with RBBB during VT a potential diagnostic trap would be attribution of RBBB to rate-dependent aberrant conduction.
  I have no funding and no conflict of interest
  References
  (1)Shah RL., Badhwar N
  Approach to narrow complex tachycardia: non-invasive guide to interpretation and management
  Heart 2020;106:772-783
  ((2)Ramprakash B., Jaishankar S., Rao H., Narasimhan C
  Catheter ablation of fascicular ventricular tachycardia
  Indian Journal Pacing and Electrophysiology
  www.ipej.org 193-201
  (3)Talib AK., Nogami A., Nishiuchi S et al
  Verapamil-sensitive upper septal idiopathjic left ventricular tachycardia
  JACC;Clinical Electrophysiology 2015;1:369-380
  (4)Sakamoto T., Fujiki A., Nakatani Y. et al
  Narrow QRS ventricular tachycardia from the posterior mitral annulus without involvement of the His-Purkinje system in a patient with prior inferior myocardial infarction
  Heart Vessels 2010;25;170-173

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  Conflict of Interest:
  None declared.

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