Correspondence |
An unusual twist: ventricular tachycardia induced by a loop in a right ventricular pacing wire
Sir,An 80-year-old lady presented to our Accident and Emergency department with episodes of recurrent syncope that were preceded by shortness of breath, but no chest pain or palpitations. She had a past history of ischaemic heart disease and complete heart block, for which a dual-chamber pacemaker had been inserted 4 months previously. All the episodes of syncope had occurred following pacemaker implantation, and a Holter monitor had been fitted to investigate them.
On examination, her heart rate was 70 bpm and regular. She exhibited signs of heart failure; jugular venous pressure was raised and bilateral crepitations were heard at the lung bases. Chest X-ray confirmed pulmonary oedema (Figure 1), but the penetration of the study did not allow us to visualize the pacing lead within the cardiac silhouette. An ECG at the time showed an atrial sensed and ventricular paced rhythm. Cardiac troponin I was raised, at 1.8, but the biochemical profile and thyroxine level were normal. A pacemaker check revealed the pacemaker was functioning appropriately. The patient's heart failure responded well to medical management with frusemide and nitrates.
|
Subsequent analysis of her Holter monitor revealed a three-minute run of ventricular tachycardia (VT), with a total of 16 episodes in 24 h. We proceeded to coronary angiography, where it was noted during screening that the patient's right ventricular pacing wire had wrapped around the tricuspid annulus (Figure 2). We repositioned the ventricular pacing wire, and subsequent Holter monitoring showed that the runs of VT had resolved. After this, the patient reported no further episodes of collapse.
|
An acutely ischaemic myocardium is more prone to ventricular arrhythmias due to abnormal automaticity or re-entry of the electrical impulse.1 Our case was unusual in that VT was initiated by mechanical stimulation of ischaemic myocardium by a displaced loop of pacing wire.
Two features suggest that this was the most likely cause. Firstly, the patient had never experienced blackouts prior to implantation of her pacemaker, but only dizziness. Secondly, the episodes of VT resolved when the pacing wire was repositioned. Diagnosis was made difficult as the loop in the right ventricular wire could not be visualized on a standard chest X-ray, particularly that on presentation which showed florid pulmonary oedema, and it was not until coronary angiography was performed that its aberrant position was noted. Ventricular tachycardia induced by permanent pacing systems has previously been recognized, and previous causes have included factory-programmed cycle length variability,2 ventricular tachycardia induced and sustained by correctly timed pacemaker impulses3 and ventricular extrasystoles merging with pacing beats.4,5
This case illustrates two points in particular. Firstly, a single postero-anterior radiograph is insufficient to accurately determine the position of pacemaker leads; a lateral film is mandatory. Secondly, myocardial excitability is greatly increased in the setting of ischaemic heart disease, and particularly in the setting of acute ischaemic episodes. In such cases, the development of malignant arrhythmias is easily precipitated by any mechanical or biochemical abnormality.
St. Mary's Hospital, London
email: alistair.lindsay{at}btinternet.com
References
1. Janse MJ and Wit AL. Electrophysiological mechanisms of ventricular arrhythmias resulting from myocardial ischaemia and infarction. Physiological Review 1989; 69:1049–69.
2. Goldman DS and Levine PA. Pacemaker-mediated polymorphic ventricular tachycardia. Pacing Clin Electrophysiol 1998; 21:1993–5.[CrossRef][Medline]
3. Lau C-P. Sensors and pacemaker mediated tachycardias. Pacing Clin Electrophysiol 1991; 14:495–8.[Medline]
4. Lefroy DC, Crake T, Davies DW. Ventricular tachycardia: an unusual pacemaker-mediated tachycardia. Br Heart J 1994; 71:481–3.
5. Karbenn U, Borggrefe M, Breithardt G. Pacemaker-induced ventricular tachycardia in normally functioning ventricular demand pacemakers. Am J Cardiol 1989; 63:120–2.[CrossRef][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||