72 year old male presents to your Emergency Department with a 4-5 hour history of palpitations. He appears well and has no associated symptoms.
BP 146/88, SaO2 99% (RA), chest clear.
- Atrial fibrillation
- Automatic implantable cardioverter-defibrillator [AICD]
- Sick sinus syndrome with inducible VT on electrophysiology study
Standard rate & calibration.
- 150 bpm.
- Regular without obvious P waves.
- Rightward axis [+129*].
- PR ~ n/a.
- QRS ~ 160 msec [RBBB morphology]
- QTc ~ 580 msec.
- QRS:T wave discordance
- Features suggesting VT.
- Fusion beats seen below (red & blue circles)
- Monomorphic R-wave in V1.
- Features suggesting VT.
Broad complex tachycardia with RBBB appearance and features of AV dissociation, highly concerning for ventricular tachycardia.
DDx: Atrial flutter (2:1) + RBBB.
My approach to any dysrhythmia, fast or slow, is to detect and correct;
Meanwhile, the patient stays connected to a monitor with defibrillator pads placed for good measure. He is advised to stay nil by mouth, pending the need for sedation. You also arrange for his AICD to be interrogated.
We top up his magnesium and obtain this second ECG….
For more information on VT versus SVT with aberrancy see;
ie. ventricular tachycardia with co-existing atrial fibrillation !!
Double tachycardia is a relatively uncommon type of tachycardia. It is classically defined as the simultaneous occurrence of organised atrial and ventricular tachycardias, or junctional and ventricular tachycardias.
Reported causes include;
- Digitalis toxicity
- Left ventricular dysfunction
- Catecholamine abuse
They can be difficult to diagnose and often require electrophysiology studies for further assessment. Interestingly, the presence of dual-lead ICDs now allow for this non-invasively.
Atrial Fibrillation with AICDs.
Atrial fibrillation is a very common dysrhythmia in patients requiring an AICD.
- ~20% have AF at time of implantation
- >50% of patients develop AF during the lifespan of their device.
In the setting of an AICD, AF can result in inappropriate ventricular shocks, ventricular arrhythmia induction & thromboembolism (after ventricular shocks in the presence of unknown AF).
Dual chamber rate-responsive pacing may prevent AF by improving haemodynamics, optimising ventricular filling and preventing retrograde atrial conduction. New overdrive pacing algorithms have been introduced to add incremental anti-arrhythmic benefits to physiological pacing. The aim is that consistent atrial pacing acts to suppress atrial fibrillation.
The PR Logic dual-chamber detection algorithm is widely used in dual-chamber Medtronic ICDs. It discriminates SVTs from ventricular tachycardias using hierarchal rules & timing of atrial and ventricular events.
An amiodarone bolus was administered and an infusion commenced following the AICD interrogation. Interestingly, his AICD was programmed to intervene on VT only at a rate exceeding 170 beats per minute.
Approximately 45 minutes into his infusion, our patient dropped his blood pressure into the 70’s with associated clamminess and distress. He received some ketamine sedation and was cardioverted to sinus rhythm.
He was discharged home two days later.
- Washizuka, T., Niwano, S., Tsuchida, K., & Aizawa, Y. (1999). AV reentrant and idiopathic ventricular double tachycardias: complicated interactions between two tachycardias. Heart, 81(3), 318–320.
- Santini, M., & Ricci, R. (2001). Atrial fibrillation coexisting with ventricular tachycardia: a challenge for dual chamber defibrillators. Heart, 86(3), 253–254.
- Weng, K.-P., Chiou, C.-W., Kung, M.-H., Lin, C.-C., & Hsieh, K.-S. (2005). Radiofrequency catheter ablation of coexistent idiopathic left ventricular tachycardia and atrioventricular nodal reentrant tachycardia. Journal of the Chinese Medical Association : JCMA, 68(10), 479–483. doi:10.1016/S1726-4901(09)70078-4
- Chowdhry, I. H., Hariman, R. J., Gomes, J. A., & El-Sherif, N. (1983). Transient digitoxic double tachycardia. Chest, 83(4), 686–687.
- Brown, M. L., Christensen, J. L., & Gillberg, J. M. (2002). Improved discrimination of VT from SVT in dual-chamber ICDs by combined analysis of dual-chamber intervals and ventricular electrogram morphology, 117–120.
- Jason’s Blog: ECG Challenge of the Week for Feb. 24th – March 3rd – another example of a double tachycardia case !!