Atrial flutter and fibrillation in the same patient. Is this related to lower loop re-entrant tachycardia?
... sinus (6F CS decapolar lead, St Jude Medical), right ventricle (6F RV quadripolar lead, Dot Medical), high right atrium (6F HRA quadripolar lead, Dot Medical), and His bundle (5F quadripolar lead, St Jude Medical). Intra-cardiac signals recorded from HRA showed discrete high amplitude deflections, with a variable A-A interval (by as much as 70 ms). Simultaneous distal CS recording showed fragmented, low amplitude A-signals (Fig. 1). Right atrial mapping with a Halo catheter (20 pole Cordis Biosense Webster) confirmed clockwise (atypical) atrial flutter. Due to significant variability of the A-A interval entrainment was not proven by HRA pacing. Isthmus pacing was performed with effective capturing of the low right atrium. This reliably and reproducibly terminated the tachycardia into sinus rhythm on five separate occasions. The arrhythmia re-initiated each time by an atrial ectopic beat that appeared to originate from the low right atrium and then degenerate, probably through the inter-atrial septum, into fibrillation in the left atrium (Fig 2). The rhythm morphology then spontaneously changed so that the variable A-A interval regularised and the fragmented low-amplitude CS signals transformed into discrete and regular atrial signals (Fig. 3). This was consistent with typical counter-clockwise atrial flutter. It was therefore felt that the arrhythmia in the right atrium was isthmus-dependent despite the fact that it could not be entrained earlier. Isthmus ablation was then performed during common type flutter converting the tachycardia into sustained sinus rhythm. A total of eight radiofrequency burns were given and bi-directional block was demonstrated. Subsequent RV and HRA pacing revealed normal retrograde and antegrade conduction curves but failed to induce further arrhythmias. Burst atrial pacing down to 220 ms also failed to initiate any further tachycardias. 6 months following the procedure the patient has not experienced any further symptoms, whereas previously she used to have daily episodes. Discussion: Lower loop re-entrant tachycardia is a right atrial arrhythmia that forms around the inferior vena caval orifice. It can occur in both counter-clockwise and clockwise directions, and can also co-exist along with the classical flutter re-entrant activation circuit around the tricuspid annulus to form a figure-8 double loop re-entry. In either case, the resultant flutter (counter-clockwise or clockwise) is isthmus dependent. Atrial flutter can spontaneously convert into fibrillation. Occasionally a pattern of lower loop re-entry is observed prior to transition into AF 3. In such patients, bi-directional cavotricuspid isthmus block was quoted to be associated with control of AF in approximately 50% of patients. In this patient, we have demonstrated the simultaneous presence of atypical and typical flutter in the right atrium, and fibrillation in the left atrium. Both arrhythmias were terminated by isthmus pacing but re-initiated spontaneously each time by a low right atrial ectopic beat, suggesting a lower loop re-entry mechanism through which the left atrium was passively driven by the right atrium. Previous studies which investigated the effect of combined ablation of pulmonary vein-left atrial junction and cavotricuspid isthmus versus pulmonary vein-left atrial junction disconnection alone, and studies which looked at the rate of recurrence of both flutter and fibrillation following cavotricuspid isthmus ablation have concluded that the incidence of AF is not reduced by isthmus ablation 4. Other studies suggest that isthmus ablation combined with PV focal ablation may be effective in mixed AF and typical atrial flutter 5. On the other hand some studies have demonstrated some symptomatic improvement / relief of AF symptoms following isthmus ablation 6&7. In this particular case, isthmus ablation has clearly resulted in symptomatic improvement indicating that perhaps most of the patient’s previous symptoms were due to atrial flutter. However, it is difficult to rule out that some of those symptoms might have been due to AF, an arrhythmia that she was demonstrated to have at least on one occasion, in which case isthmus ablation appears to have been beneficial. References: 1. Murgatoyd F, Krahn A, Klein GJ, et al. Handbook of Cardiac Electrophysiology, A Practical Guide to Invasive EP Studies and Catheter Ablation. ReMEDICA Publishing Limited., 2002, pp 68-69. 2. Tada ...