Long term post Ventricular tachycardia ablation guided by non contact mapping system in a single center study
Long Term Success After Radiofrequency Catheter Ablation of Monomorphic Post Myocardial Infarction Ventricular Tachycardias guided by the Non Contact Mapping System <ul><li>Salah Atta*, Hassan Khalid **, Ahmad Abdul-aziz**, Lars Eckardt***, Michael Ribbing***, Wilhelm Haverkamp***, Nadia Selim*, Günter Breithardt***. </li></ul><ul><li>*Cardiology Dep., Assiut University; ** Critical Care Dep., Cairo University; </li></ul><ul><li>***Cardiology and Angiology Dep., Muenster University Hospital, Germany. </li></ul><ul><li>ECAS, 2004 </li></ul>
<ul><li>-About 3% of the patients who survive the acute phase of myocardial infarction develop sustained ventricular tachycardias between 48 hr and 6 weeks after the onset of infarction. An uncertain percentage develop infarct related ventricular tachycardias at a still later stage. The bulk of evidence supports the concept that this arrhythmia is caused by reentry . </li></ul><ul><li>(de Bakker 1988, Borgg-refe et al. 1991, Stevenson et al. 1991, 1992). </li></ul>
Functional components of reentry circuits. (Stevenson 1996). <ul><li>The circulating reentrant wave front propagates through a slow conduction zone (SCZ) in the scar which have an enterance and an exit. The QRS begins at the Exit from the scar. </li></ul><ul><li>The reentrant wavefront may return to the slow conduction zone through two different types of loops (outer loop and inner loop). </li></ul><ul><li>The SCZ does not generate electrical activity detectable in the surface electrocardiogram but locally it can be detected by diastolic activity. </li></ul>
Functional components of reentry circuits. (Stevenson 1996).
<ul><li>-Due to the complexity of the substrate and possible haemodynamic instability, only 10% of patients have been considered suitable for catheter ablation by conventional mapping (Morady et al. 93) . New mapping tools have been developed, which either provide global mapping data (non-contact and basket mapping techniques) (Schilling et al. 1999, Schalij et al 1998) or create maps that correlate anatomy with electrical activation [Carto, Localisa, Realtime Position Management]. (Gepstein et al 1997, Wittkampf et al 1999). </li></ul>
Aim of The Study <ul><li>- To assess the feasibility , short and long term outcome of RF catheter ablation guided by the non contact catheter mapping technique in the control of monomorphic post-infarction VT. </li></ul><ul><li>-To compare the outcome of these procedures in case of ablation using isolated RF lesions at target sites shown by the non contact mapping system, with the outcome of performing substrate modification using the RF lesions guided by the same system. </li></ul>
Patients and Methods <ul><li>- This study included initially 19 consecutive patients with monomorphic post myocardial infarction VT in whom non-contact catheter guided RF ablation was attempted. Shifting to conventional mapping and abortion of the procedure in 4 patients was due to atherosclerotic Ileofemoral disease hindering retrograde placement of the balloon catheter in the LV in 2 patients, or non induciblity of the clinical VT after placement of the balloon catheter in LV in other 2 pts. </li></ul>
<ul><li>So the procedure was done in 15 patients (13 men) with a mean age of 67 ± 6.7 (range from 55-77) years admitted to Muenster University Hospital in the period between Mai 1999 and January 2002. The patients had a sustained monomorphic VT and a history a history of a remote anterior (n=6), inferior (n=6), or both anterior and inferior (n=3) MI. </li></ul><ul><li>The indications for ablation of VT were incessant VT in 8, recurrent episodes of documented monomorphic VT in 3 patients , and frequent ICD shocks in 4 patients. 3 of these VTs were poorly tolerated by the patients. </li></ul>
<ul><li>All patients were subjected initially to clinical assessment, 12 lead ECG, x- ray chest, echocardiographic assessment to exclude left ventricular thrombus and assess LV function and coronary angiography and revascularisa-tion if needed. </li></ul>
<ul><li>The Electrophysiologic study (EPS) and ablation procedure: </li></ul><ul><li>- The inducibility of VT was tested by pacing with programmed ventricular stimulation from the right ventricular apex and outflow tract at four different cycle lengths with up to three premature extrastimuli. </li></ul><ul><li>-A 7F deflectable quadripolar 4-mm cooled tip (Chilli 3500) catheter was introduced into the right femoral artery and advanced retrogradely via the aortic valve into the left ventricle and used for navigation and ablation. </li></ul>
Mapping process with the non contact mapping system (The Ensite 3000, Endocardial solutions) <ul><li> The system consists of : </li></ul><ul><ul><li>-A catheter-mounted multielectrode array (MEA) mounted on a 7.6 ml balloon on a 9F catheter. </li></ul></ul><ul><ul><li>-A custom-built amplifier system, and </li></ul></ul><ul><ul><li>-A Silicon Graphics workstation to run a specially designed system software. </li></ul></ul>
The non inflated balloon catheter on the left, the inflated balloon catheter in the middle and a magnified electrode on the balloon array on the right. (Schilling et al., 1998).
Construction of the geometry by the Ensite system <ul><li>The system is able to locate any conventional catheter in space with respect to the MEA. This is used for constructing a 3-dimensional computer model of the endocardium (virtual endocardium) at the onset of the procedure in sinus rhythm. </li></ul><ul><li>The potential field created on the MEA surface is related to the MEA–endocardial geometry matrix. When this is known, it is possible to compute endocardial electrograms from the MEA potentials by inverse solution of Laplace's equation thus the system can reconstruct and interpolate > 3300 electrograms simultaneously over the virtual endocardium. </li></ul>
<ul><li>Mapping procedures : </li></ul><ul><li>Mapping was performed by first inducing and recording the VT even for few beats. Then analysis by aligning the map time course with the time of QRS onset and then finely adjusting the color controls to reveal the exit site. This was done using the virtual electrograms and isopotential maps which are colour coded voltage maps with negative unipolar potentials in white on a purple backgrounds, producing a unipolar activation map. </li></ul>
Ablation Policy <ul><li>Group I: (first 7 patients, 9 targted VTs, 7 of them with RBBB morphology , CL 445 ± 93 ms) </li></ul><ul><li>The Ensite system was used to trace the exit sites, presystolic activity, identify sites of diastolic activation during VT and zones of slow conduction. Each of these was used to identify potential target sites for ablation by by isolated RF applications. </li></ul>
Functional components of reentry circuits. (Stevenson 1996). With target ablation by isolated RF applications demo-nstrated
Group II: The next 8 patients with 12 targeted VTs, 9 of them with RBBB morphology, CL 445 ± 93 ms) in whom Modification of the arrhythmogenic substrate by linear or area RF ablation according to the substrate mapped by Ensite.
<ul><li>-In inferior infarction (3pts.), special attention was given to the submitral isthmus and the ablation line was extended up to the mitral valve ring. </li></ul><ul><li>-In anterior infarction (3pts.), the linear lesions were extended from the exit zone to an area of "dead" myocardium with very low amplitude electrograms through areas of diastolic activities and/or slow conduction shown by the isopotential map of the Ensite system. </li></ul><ul><li>-Exit isolation with RF lesions (Area ablation) was performed in two patients. </li></ul>
Post ablation follow up <ul><li>-Programmed ventricular stimulation was repeated only at the end of the sequence of RF applications. </li></ul><ul><li>-All successfully ablated patients underwent a control electrophysiological study 5 days post ablation befoe discharge. </li></ul><ul><li>- Thereafter, the patients were seen at regular 3-month intervals in the outpatient clinic. </li></ul>
Definitions of outcome <ul><li>We defined: </li></ul><ul><li>- immediate success as non inducibility of the previously inducible targeted VTs at the end of the procedure. </li></ul><ul><li>- Acute success as no early clinical recurrence during the hospital stay and non inducibility of the ablated VT during the 5 days post ablation EPS. </li></ul><ul><li>- Long term success referred to no clinical recurrence of previously considered ablated VTs during the period of follow up. </li></ul>
RESULTS <ul><li>-The Ensite system could show exit sites of all tachycardias except in two VTs. It could show diastolic activity in 17 VTs ranging between 50 and 230 ms before the onset of the QRS complex during the VT with a mean of 105 ± 70 ms. </li></ul><ul><li>-The ablation procedure was complicated by femoral arteriovenous fistula in one patient, femoral artery thrombosis in another patient while perforation of the Ensite balloon and leakage of the contrast material occurred in one case with no consequences. </li></ul>
RESULTS 79 RF, 4-24 (9.3 ± 4.9) RF applications (P < 0.001). 7-40 pulses, total 142 (17.5±12.2) (p= 0.067). 36-97 (64.8 ±18.8) min (p. 0.766). 345-630 min., 437,67 ± 89.6 min (p. 0.766) Group II (31 pulses) had a mean of 4.4 ± 2.2. 77 RF applications (mean of 8.7 ± 3.8 per patient) 48 –116 min,77.6 ± 20.5 min) 300-480 min., 397± 64.9 min Group I RF pulses in sinus rhythm Total RF pulses X-ray exposure time Procedurduration
<ul><li>In the 2nd group, The lines of RF lesions were in the range between 2.4-7.6 cm with a mean of 3.9 ± 1.8 cm. To achieve this, the number of RF pulses per patient was in the range of 7-40 pulses, with a total of 142 RF pulses and an average 17.5±12.2. This was not significanty differnrt from gp I (p= 0.067). </li></ul><ul><li>Out of these, 79/142 RF applications were during sinus rhythm with a range between 4-24 per patient and a mean of 9.3 ± 4.9 RF pulses, this was significantly more than in group I. Considering the 3 poorly tolerated VTs alone, substrate modification by 19 RF pulses (17 RFs in sinus rhythm), could prevent reinducibility of the 3 VTs at the end of the procedure . </li></ul>
The figure, shows exit of a VT as shown by the Ensite isopotential colour coded map and a line of ablation lesions extended from the exit through the diastolic pathway inside the scar in a patient with anterior infarction. On the left is the virtual endocardium in RAO with some rotation to show the line of ablation on the anterior wall. On the right are the surface (upper three) , local catheter recoeded (the middle two), and virtual electrograms (the lower four electrograms).
Compared outcome throughout the follow up period 52% 16, 76.5% 21 All patients: in our study 9(75%) P.=0.028 10(83%) P.= 0.032 0 0 10(83%) P.= 0.585 12 Group II 2 (22%) 3 (33%) 2 (22%) 1(11%) 6 (66%) 9 Group I Long term ablated VT s Discharge resul(7 days post Ab.) Reinducible VTs in control EPS Early recurrences Acutely ablated VTs Targeted VTs
Compared outcome throughout the follow up period
Conclusions : <ul><ul><li>RF ablation in post MI monomorphic VT patients guided by the non contact mapping system is safe and have a good immediate as well as short and long term outcome. </li></ul></ul><ul><ul><li>Substrate modification guided by the non contact mapping system may improve the short and long term outcome of RF ablation in these patients and carries hopes in haemodynamically unstable VTs not controllable by other therapies as they may be ablated in sinus rhythm guided by the system. </li></ul></ul>
Conclusions : <ul><li>On the other hand , The use of the non contact mapping system may not produce the excpected reduction in x-ray exposure , procedure duration and number of RF pulses needed for ablation. </li></ul><ul><li>Mechanical difficulties in introducing the Balloon catheter to the suitable position, possible supression of VT induction or difficulties in reaching target sites by the ablation catheter and increased femoral arterial complications are of the limitations of the use of the non contact mapping system. </li></ul>