a troublesome tachycardia
The Case.
An 11 year old boy is bought to ED by his mother on a busy weekday evening. Mum reports that he has been ‘a little bit off’ over the past 24 hours, in particular he’s not keeping down his food or fluids. She is also worried about his colour, stating ‘he looks a little pale and sweaty’.
You find him a little wheezy on auscultation, with room air saturations of 93%. Of concern is his pulse rate of greater than 150 per minute.
This is his ECG…
[DDET What’s your interpretation ? What would you do next ??]
For extra info, here’s his CXR.
My Interpretation:
Rate: 166 / min.
Rhythm: Sinus (p waves present)
Axis:
* Abnormal P-wave axis (negative in II, III, aVF + positive aVR & V1) ?retrograde P-waves
* QRS Axis – normal.
PR short ~80msec. Narrow complex QRS ~80-90msec. QTc ~ 440msec
LVH by voltage.
?delta waves (I, II, aVL)
DDx.
? Sinus tachycardia (with ectopic atrial pacemaker)
? Junctional tachycardia with retrograde atrial activation
?? Re-entry pathology (short PR)
[/DDET]
[DDET You refer to the ‘experts’ !!]
The progress & referral…
- ECG faxed to tertiary paediatric cardiology service… No immediate diagnosis.
- Patient has ongoing diaphoresis, increasing breathlessness and progressive hypotension.
- Transfer to tertiary PICU
- Cardiogenic shock (LVEF 26%)
- Chemical & electrical cardioversion unsuccessful
- Placed on ECMO….
Whilst the team considers further options including LVAD & transplant, another Cardiologist reviews the initial (above ECG) and makes the following diagnosis….
[/DDET]
[DDET The diagnosis…]
Permanent junctional reciprocating tachycardia
OF COURSE !!!
What is this ?
An unusual form of SVT with a 1:1 AV relationship, classically occuring in children.
It is an AV re-entry tachycardia (described as a long R-P tachycardia) with a postero-septal accessory pathway. It has a very long retrograde conduction time & therefore only ever conducts to the ventricle via the normal AV-node/HIS bundle. It is characterised by incessant (& sometimes permanent) narrow complex tachycardia, which may be the patient’s predominant rhythm.
The ECG reveals inverted P-waves in the inferior leads (as well as left-lateral leads) along with a P-R interval shorter than R-P interval during the tachycardia. The characteristic ECG feature is a long R-P interval consistent with slow retrograde conduction.
Why do we care ?
It is a rare, but documented cause of tachycardia-induced cardiomyopathy in children & is frustratingly refractory to drug therapy.
Can we fix it ?
Yes we can! (well the electrophysiology team can).
The cure lies with radiofrequency ablation.
This is exactly what happened to our 10 year patient.
– Whilst on ECMO he undergoes ablation of his accessory pathway.
– I met this fella 2 years down the road. He has a normal ECG & CXR. He plays soccer with his mates. A normal 12 year old….
[/DDET]
[DDET Was there a clue in the original ECG?]
The P-Wave Axis.
The first depolarisation encountered in the normal cardiac cycle; representing both right & left atrial depolarisation.
Axis is usually directed inferiorly and to the left (as the atria depolarise from SA –> AV node).
- +45 to +60 degrees in frontal plane
- P-wave has most prominent positive deflection in lead II (up to 2.5mm) & negative deflection in aVR (it may often be biphasic in lead V1).
An abnormal P-wave axis can result from:
- Pulmonary disease (right-ward axis; P-pulmonale, from RA enlargement)
- Congenital heart disease (right or left atrial enlargement, left-ward axis)
- Limb electrode reversal
- Dextrocardia
- Ectopic atrial activity (other than SA node)
- Multifocal atrial tachycardia
- Retrograde P-waves (from impulse near AV node, depolarising atria towards SA node)
- Inverted P’s in inferior leads
- Tall peaked P in V1
- P may be buried within subsequent QRS complex
[/DDET]
[DDET References]
- Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
- Vaksmann G et al. Permanent junctional reciprocating tachycardia in children: a multicentre study on clinical profile and outcome. Heart. 2006 Jan;92(1):101-4. Epub 2005 Apr 14.
- Bensler JM et al. Tachycardia-Mediated Cardiomyopathy and the Permanent Form of Junctional Reciprocating Tachycardia. Tex Heart Inst J. 2010; 37(6): 695–698.
- Semizel E et al. Permanent form of junctional reciprocating tachycardia and tachycardia-induced cardiomyopathy treated bycatheter ablation: a case report. Turk J Pediatr. 2003 Oct-Dec;45(4):338-41.
- http://www.cardiologyhd.com/All-EP/persistent-junctional-reciprocating-tachycardia-pjrt.html
- http://www.med.nus.edu.sg/paed/resources/cardiac_thumbnail/arrhythmias/pjrt.htm
[/DDET]
