Characterization of Left Atrial Tachyarrhythmias in Patients Following Atrial Fibrillation Ablation:Correlation of surface ECG with Intracardiac Mapping

Abstract

With expected success rates in excess of 80% for achieving long term arrhythmia control, catheter based ablation has become a popular treatment strategy in the management of patients with atrial fibrillation (AF). However, the success of AF ablation has been tempered by the occurrence of post procedure left atrial tachycardias and / or flutters, which can be seen in up to 30% of the patients. These arrhythmias are perpetuated either due to abnormalities of impulse formation (abnormal automaticity / triggered activity), or abnormalities of impulse conduction (micro / macroreentry). Regardless of the underlying mechanism, these tachycardias manifest distinct "P" or flutter waves on the surface ECG, recognition of which may facilitate their characterization / localization. However, because of the frequent overlap in the morphology of P waves, intracardiac mapping is often the only way to distinguish them apart. This is accomplished using a combination of activation, entrainment and electroanatomic mapping techniques. Tachycardias resulting from abnormalities of impulse formation and / or microreentry are characteristically focal and usually confined in and around pulmonary vein (PV) segments which have reconnected (septal aspect of right PVs and anterior aspect of left PVs). In contrast, macroreentrant tachycardias manifest a large circuit dimension involving zone(s) of slow conduction. These are most commonly seen to occur around the mitral valve but can develop in any part of the left atrium where "gaps" across prior ablation lesion sets create altered conduction. Successful ablation of focal tachycardias is usually accomplished by isolating the reconnected PV segment(s). In case of macroreentrant arrhythmias however, a more extensive ablation approach is typically required in order to achieve conduction block across isthmus of the circuit. Using these strategies, the majority of left atrial tachycardias occurring post AF ablation can be successfully cured with excellent long term results.

Figure 1.

Figure 2.. Shows ECG morphologies of mitral annular (MA) flutter. Counterclockwise (CCL) MA flutter typically manifests positive forces in the inferior limb leads, completely negative or predominantly negative forces in leads I and aVL and positive flutter wave morphology in the precordial leads (V1 – V6), although lead V2 may manifest a small initial negative component. In contrast, clockwise (CL) MA flutter manifests negative forces in the inferior leads, positive forces in leads I and aVL and predominantly positive complexes in the precordial leads,although leads V5-6 may manifest initial negative forces.

Figure 3.. Shows similarities and differences in the ECG manifestations of counterclockwise (CCL) mitral annular (MA) and clockwise (CL) typical right atrial (RA) flutter. The ECG morphology of CCL MA flutter can be identical to CL RA flutter except lead V1 which is predominantly or completely negative in the latter.

Figure 4.. Shows similarities and differences in the ECG manifestations of clockwise (CL) mitral annular (MA) and counterclockwise (CCL) typical right atrial (RA) flutter. The ECG morphology of CCL MA flutter can be identical to CL RA flutter except lead V1 which is predominantly or completely negative in the latter. The ECG morphology of CL MA flutter can be identical to CCL RA flutter except lead I which is positive in the former and either biphasic or negative in the latter. Lateral precordial leads (V5-6) can also be helpful in distinguishing between the two – in the latter they manifest predominantly negative forces as compared with CL MA flutter where these leads are predominantly positive.

Figure 5A.. Panel A represents the electroanatomic shell of the left atrium in left anterior oblique projection showing the macroreentrant circuit of counterclockwise mitral annular (MA) flutter circuit (arrows). Panel B shows shows the typical ECG morphology of this rhythm. MA flutter typically manifests positive forces in the inferior limb leads, completely negative or predominantly negative forces in leads I and aVL and positive flutter wave morphology in the precordial leads (V1 – V6), although lead V2 may manifest a small initial negative component.

Figure 5B.. Represents typical example of response to entrainment from the right atrium during counterclockwise mitral annular (MA) flutter. From top to bottom the recordings are arranged as follows: ECG leads I, aVF and V1, 10 bipoles of circular mapping (Lasso) catheter located in the common ostium of the left sided veins, distal (MAPD) and proximal (MAPP) bipoles of mapping catheter located at lateral MA, 5 biploes of decapolar catheter located in the coronary sinus (cs) and 5 bipoles of decapolar catheter located in the right atrium (RA) along the crista terminalis (CT). Aactivation pattern in the CS is proximal to distal. Following termination of pacing drive from the RA catheter (CT) the postpacing interval is ≥30 milliseconds (ms) longer than the tachycardia cycle length (225ms) which proves that RA is not is not participating in the circuit.

Figure 5C.. Represents the same patient as in Figure 5B with identical arrangement of recordings. Following termination of pacing drive from the proximal bipoles (near ostium) of the decapolar catheter located in the CS, the post-pacing interval is identical to tachycardia cycle length (225ms) which proves that proximal CS is in the circuit.

Figure 6.

Figure 5D.. Represents the same patient as in Figure 5B with identical arrangement of recordings. Following termination of pacing drive from the distal bipoles of the mapping catheter (MAPD) which located at 12 0’clock on the mitral annulus, the post-pacing interval is identical to tachycardia cycle length (225ms) which proves this part of the MA is in the circuit and proves that this is macroreentry.

Figure 5E.. Represents the same patient as in Figure 5B with identical arrangement of recordings. Lesions were delivered extending from the inferolateral aspect of mitral anulus to the left inferior pulmonary veins (see inset) with additional lesions required within the coronary sinus that resulted in termination of the flutter (see arrow)