Interesting Cases
Title: Atrial Tachycardia originating from outside of the heart chambers
A 58 year old lady was referred to us due to frequent episodes of palpitation refractory to Flecainide and Amiodarone. An EP study had been performed 6 month prior to referral in another center and ablation was not tried because of presumed para-hisian atrial tachycardia .
We decided to plan an EP study in another session after the drugs were discontinued for 5 half time intervals. The diagnostic catheters were placed in High RA, His, RV apex, Coronary Sinus and Tricuspid Ring (halo). The arrhythmia was induced easily after initiation of low dose isopreterenol infusion. The following tracing (fig.1) illustrates the pattern of atrial wave conduction.
fig.1 Intracardiac recording shows the earlieat A potential recorded in His region
With respect to the short cycle lenght of the arrhythmia ,atrial flutter was suspected but ruled out by entrainment mapping in right and left isthmuses and also by very high variation in cycle lenght (>15%) which is very unusual for flutters .As we expected, in this tracing the earliest A wave was recorded in the catheter positioned in His region before the potentials recorded in HRA, Tricuspid Ring (Halo catheter) and also before posterior portion of Mitral ring (CS catheter) ;This finding implies that the origin of AT may be near the His bundle.
Considering the high risk of AV block resulting from RF application near His region, other potential origins of AT mimicking this pattern should be ruled out before decision. So left atrial mapping was performed after septostomy. The recorded A wave potentials in LA (including right upper pulmonary vein) were pretty later than that recorded in the His region. Although a second arrhythmia with different pattern was ablated at the ostium of the left upper pulmonary vein, the first arrhythmia showed up immediately (fig.2)
Fig.4 The earliest potential recorded in NCC and ablation here terminated the arrhythmia
Discussion:
Although atrial tachycardia is less frequent than other atrial arrhythmias such as AF, AVNRT and AVRT, it is usually more challenging for physicians because of severe symptoms that are not easily controlled by drug treatment. In this regard RF ablation would be an appropriate treatment due to the high success rate and rare complications. The foci responsible for induction of AT are almost limited to some well known regions. The most freuent foci are crista terminalis, coronary sinus ostium, regions around the mitral or tricuspid ring and the ostia of pulmonary veins. The morphology of P wave can be a useful clue to predict the focus before ablation. With this guide, finding the origin of the arrhythmia is usually feasible after placement of recording catheters and using diagnostic maneuvers.
However, unusual sites are rarely encountered which requires prompt awareness of the operator. In recent years the aortic cusps have been found to be the potential sources of arrhythmias. Abnormal muscle fibers can cause automatic or triggered activity which produces atrial or ventricular arrhythmias. Due to the close contact of the right and left aortic cusps with ventricles, arrhythmias originating from these cusps present with PVC's or VT ( click to see our reported case with left cusp PVC) but non- coronary cusp of the aorta with its posterior orientation is in the vicinity of the right atrium and ectopic pulses from here conduct to atrial chambers resulting in PAC's or AT.
To conclude, with improving technology and knowledge about arrhythmias and techniques of ablation, interventional approaches have been used as reliable and effective tool for treatment of arrhythmias even as the first line of therapy . In this regard the familiarity and trust of cardiologists with these procedures play a major role for better management of patients.
Dr. Ali Kharazi
Dr. Hamid Bonakdar
We decided to plan an EP study in another session after the drugs were discontinued for 5 half time intervals. The diagnostic catheters were placed in High RA, His, RV apex, Coronary Sinus and Tricuspid Ring (halo). The arrhythmia was induced easily after initiation of low dose isopreterenol infusion. The following tracing (fig.1) illustrates the pattern of atrial wave conduction.
fig.1 Intracardiac recording shows the earlieat A potential recorded in His regionWith respect to the short cycle lenght of the arrhythmia ,atrial flutter was suspected but ruled out by entrainment mapping in right and left isthmuses and also by very high variation in cycle lenght (>15%) which is very unusual for flutters .As we expected, in this tracing the earliest A wave was recorded in the catheter positioned in His region before the potentials recorded in HRA, Tricuspid Ring (Halo catheter) and also before posterior portion of Mitral ring (CS catheter) ;This finding implies that the origin of AT may be near the His bundle.
Considering the high risk of AV block resulting from RF application near His region, other potential origins of AT mimicking this pattern should be ruled out before decision. So left atrial mapping was performed after septostomy. The recorded A wave potentials in LA (including right upper pulmonary vein) were pretty later than that recorded in the His region. Although a second arrhythmia with different pattern was ablated at the ostium of the left upper pulmonary vein, the first arrhythmia showed up immediately (fig.2)
fig.2 termination of the second arrhythmia after ablation at LUPV ostium and immediate initiation of the
first arrhythmia (look at different rate and patterns)
Despite all documents obtained in EP study favoring para-hisian origin of AT, fearing of the consequences of ablation near His region forced us to look for another option. Based on some published reports, AT may be originated from the non-coronary cusp of the aorta and with respect to the vicinity of this focus to the His region the pattern of electrical conduction resembles that of a para-hisian AT.
So the catheter of ablation was retrogradely placed in NCC of the aorta (fig.3)
fig.3 the ablation catheter positioned retrogradely in NCC ( looking backward in RAO view)
The potential recorded here was definitely earlier than the recorded potential in the His region and RF ablation here terminated the arrhythmia just after 2 seconds (fig.4) and it was not inducible thereafter at all. The patient has been asymptomatic for one month after ablation despite cessation of antiarrhythmic drugs.
first arrhythmia (look at different rate and patterns)
Despite all documents obtained in EP study favoring para-hisian origin of AT, fearing of the consequences of ablation near His region forced us to look for another option. Based on some published reports, AT may be originated from the non-coronary cusp of the aorta and with respect to the vicinity of this focus to the His region the pattern of electrical conduction resembles that of a para-hisian AT.
So the catheter of ablation was retrogradely placed in NCC of the aorta (fig.3)
fig.3 the ablation catheter positioned retrogradely in NCC ( looking backward in RAO view)The potential recorded here was definitely earlier than the recorded potential in the His region and RF ablation here terminated the arrhythmia just after 2 seconds (fig.4) and it was not inducible thereafter at all. The patient has been asymptomatic for one month after ablation despite cessation of antiarrhythmic drugs.
Fig.4 The earliest potential recorded in NCC and ablation here terminated the arrhythmiaDiscussion:
Although atrial tachycardia is less frequent than other atrial arrhythmias such as AF, AVNRT and AVRT, it is usually more challenging for physicians because of severe symptoms that are not easily controlled by drug treatment. In this regard RF ablation would be an appropriate treatment due to the high success rate and rare complications. The foci responsible for induction of AT are almost limited to some well known regions. The most freuent foci are crista terminalis, coronary sinus ostium, regions around the mitral or tricuspid ring and the ostia of pulmonary veins. The morphology of P wave can be a useful clue to predict the focus before ablation. With this guide, finding the origin of the arrhythmia is usually feasible after placement of recording catheters and using diagnostic maneuvers.
However, unusual sites are rarely encountered which requires prompt awareness of the operator. In recent years the aortic cusps have been found to be the potential sources of arrhythmias. Abnormal muscle fibers can cause automatic or triggered activity which produces atrial or ventricular arrhythmias. Due to the close contact of the right and left aortic cusps with ventricles, arrhythmias originating from these cusps present with PVC's or VT ( click to see our reported case with left cusp PVC) but non- coronary cusp of the aorta with its posterior orientation is in the vicinity of the right atrium and ectopic pulses from here conduct to atrial chambers resulting in PAC's or AT.
To conclude, with improving technology and knowledge about arrhythmias and techniques of ablation, interventional approaches have been used as reliable and effective tool for treatment of arrhythmias even as the first line of therapy . In this regard the familiarity and trust of cardiologists with these procedures play a major role for better management of patients.
Dr. Ali Kharazi
Dr. Hamid Bonakdar
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