ECG: Fascicular VT

Prof .Dr.K.H.NOORUL AMEEN’S unit M6 Dr.G.ARUN KUMAR ECG OF THE WEEK

13 year old boy admitted with complaints loose stools- 3 days h/o gidiness+ No h/o fever No h/o abdominal pain No h/o chest pain

O/E- pt drowsy obeys oral commands Moves all limbs afebrile dehydration +++ CVS - S1S2+ tachycardia+ RS – NVBS+ P/A – Soft BP 80/60 mmHg PR 140/min

During tachycardia During SR RHYTHM To be defined SR RATE Ventricular 184 82 Atrial 184 82 QRS duration AXIS QRS -60 to -90 +60 to +90 P +30 to +60 RP’ (RP) interval 70ms 600ms P’R (PR) interval 260ms 130ms P’R (PR) relation 1:1 (AV dis - nil) V:A conduction1:1 1:1 Min Max 80 122 Min Max 70 80

Chamber enlargement Nil Nil ST – T CHANGES Sec changes+ T inv II III avf V3 – V6 QRS alternans Nil Nil Cycle length alternans Nil Nil Block Bundle branch RBBB (wide R) Nil Pseudo r NIL Nil Pseudo s Nil Nil Epsilon waves Nil Nil RS ratio (v6) 25 % Only R RS interval < 40 ms < 40 ms

HR>100 ORS<120 QRS>120 REGULAR IRREGULAR VT OR UNEX PLAINED RYTHM SVT WITH ABERRANCY AF WITH ABERR AF WITH WPW POLY VT REGULAR IRREGULAR AF MAT EAT AFL WITH VARIABLE BLOCK ST WITH PACs P WAVE NO YES RP INTERVAL RP< 50% RR RP> 50% RR TYPICAL AVNRT O-AVRT JT ST OR EAT WITH 1 AV BLOCK INAPPROPRIATE ST SANRT ATYPICAL AVNRT EAT AVRT AVNRT AT AFL

Step 1: Lack of RS Complex An RS complex was present in at least one precordial lead in all SVTs with aberrant conduction so this finding is 100% specific for the diagnosis of ventricular tachycardia. However, only 26% of VTs did not have an RS complex in any precordial lead. In other words if you do not see an RS complex it is VT , but if you see an RS complex you need to go to Step 2 because RS complexes are seen in both SVTs and some Ventricular Tachycardias RS COMPLEX PRESENT

Step 2: Whether the R to S interval in any precordial lead is greater than 100 ms This is measured from the beginning of the R wave to the deepest portion of the S wave. An RS interval greater than 100 msec was not observed in any SVT with aberrant conduction. Half of the VTs which did have an RS complex in at least one precordial lead had an RS interval less than 100 msec and the other half of the VTs had an RS interval of greater than 100 msec. Thus, an RS interval of more than 100 msec in any precordial lead when an RS complex was present (Step 2) were each 100% specific for the diagnosis of VT. RS interval 40 ms

Step 3: AV Dissociation When looking at an ECG of a wide complex tachycardia it is always nice to see AV dissociation because it is 100% specific for the diagnosis of VT. NO AV Dissociation

Step 4: Morphology Criteria If we do not make the diagnosis of VT with Steps 1-3 then the morphology criteria are analyzed in leads V1 and V6. If both leads have a morphology compatible with the diagnosis of VT, the diagnosis of VT is made. Otherwise, the diagnosis of SVT with aberrant conduction is made by exclusion.

Tachycardia with a right bundle branch block-like QRS Lead V1 Monophasic R or QR or RS favors VT Triphasic RSR' favors SVT Lead V6 R to S ratio <1 (R wave smaller than S wave) favors VT QS or QR favors VT Monophasic R favors VT Triphasic favors SVT R to S ratio >1 (R wave larger than S wave)favors SVT

Tachycardia with a left bundle branch block-like QRS Lead V1 or V2 Any of following R >30 msec, >60 msec to nadir S, notched S favors VT Lead V6 Presence of any Q wave, QR or QS favors VT The absence of a Q wave in lead V6 favors SVT

FINDINGS VT RBBB PATTERN LEFT AXIS DEVIATION

FASICULAR VT ARISING FROM LEFT POSTERIOR FASICLE

Fascicular tachycardia has been classified into three subtypes: (1) left posterior fascicular VT with a right bundle branch block (RBBB) pattern and left axis deviation (common form); (2) left anterior fascicular VT with RBBB pattern and right-axis deviation (uncommon form) (3) upper septal fascicular VT with a narrow QRS and normal axis configuration (rare form) Fascicular Ventricular Tachycardia

Fascicular VT The arrhythmia mechanism appears to be macro reentry involving calcium-dependent slow response fibers that are part of the Purkinje network, although automatic tachycardias have also been observed. Idiopathic LV septal VT is unique in its suppression with verapamil. Beta blockers have also been used with some success as primary or effective adjunctive therapy. Catheter ablation is very effective therapy for VT resistant to drug therapy or in patients reluctant to take daily therapy, with anticipated successful elimination of VT in >90% of patients.

In general ventricular tachycardias have wide QRS complexes. One of the earliest descriptions of ventricular tachycardia (VT) with a narrow QRS complex was by Cohen et al in 1972 . Their description was a left posterior fascicular tachycardia with relatively narrow QRS. In 1979, Zipes et al reported three patients with ventricular tachycardia characterized by QRS width of 120 to 140 ms, right bundle branch block morphology and left-axis deviation. These patients were young and had no major cardiac abnormalities.

A pre systolic or diastolic potential preceding the QRS, presumed to originate from the Purkinje fibers can be recorded during sinus rhythm and ventricular tachycardia in many patients with fascicular tachycardia Intravenous verapamil is effective in terminating the tachycardia. However the efficacy of oral verapamil in preventing tachycardia relapse is variable Radiofrequency is the procedure of choice.

Since fascicular VT is sometimes difficult to induce despite pharmacological provocation, some workers (Gupta et al) prefer primary ablation. In a recent report, seven cases of incessant fascicular VT were successfully ablated with no recurrence . They reported a shorter procedure time, significantly lower fluoroscopy time and lesser number of radiofrequency energy deliveries in the primary versus elective groups. The longer procedural time during elective ablation was mainly due to the time spent in induction of fascicular VT.

REFERENCE Indian Pacing Electrophysiology J.2004 Jul–Sep; 4(3):98–103. Published online 2004 July 1.Francis et al. Zipes bed side electro physiology Washington medical therapeutics

ECG: Fascicular VT

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ECG: Fascicular VT