Ventricular tachycardia ablation in patients with coronary heart disease: beyond the reentry circuit.

INTRODUCTION: Patients with coronary heart disease and left ventricular dysfunction are at increased risk for the development of ventricular tachycardia (VT) related to areas of myocardial fibrosis. Although the mechanism and the circuit of this arrhythmia are well understood, little is known about the triggers that precipitate VT episodes. Purkinje fiber potentials may be responsible for idiopathic VT, and recent studies have related them to polymorphic VT and ventricular fibrillation. METHODS: Between January 2002 and December 2003, we performed ablation in 10 patients with coronary heart disease, left ventricular systolic dysfunction and VT refractory to pharmacological therapy. All patients had implantable cardioverter-defibrillators. Electroanatomical activation and voltage mapping (CARTO) and electrophysiological criteria (premature activation during VT, pace mapping, and presence of diastolic potentials) were used to define scar regions, slow conduction areas and the reentry circuit isthmuses. RESULTS: Spike potentials were recorded in the scars of three patients. These potentials were almost fused with the ventricular electrogram during sinus rhythm, and were more premature during VT, probably reflecting local activation of Purkinje fibers. During ablation, we were able to dissociate the spike from the ventricular electrogram, thus terminating the VT. In the cases with conduction recovery, ventricular; ectopic beats recurred, preceded by a spike and degenerating into short runs of VT. The ablation strategy was not modified since persistence of the VT required the isthmus. CONCLUSION: The results suggest that residual Purkinje fibers may be present in scar regions and that the activity of these fibers may trigger VT in pre-established circuits.

Atrial flutter ablation: correlation between isthmic activation times and flutter cycle.

BACKGROUND: Ablation of typical atrial flutter relies on the suppression of electrical conduction along the cavo-tricuspid isthmus. Bidirectional isthmus block is a criterion of successful ablation and is associated with the presence of different activation times on each side of the ablation line. OBJECTIVE: The aim of this study was to determine whether the difference in isthmic activation times correlates with the length of the atrial flutter cycle. POPULATION AND METHODS: We studied 31 patients with typical atrial flutter (93.6% male, mean age 66 +/- 9 years) who underwent successful ablation during tachycardia. CARTO electroanatomic mapping was used to confirm diagnosis of isthmus-dependent atrial flutter, guide the ablation line creation and assess its efficacy. At the end of the procedure, a three-dimensional activation map of the right atrium was constructed, under pacing from the coronary sinus ostium (with a 500 ms cycle). Activation times on the lateral (right) and septal (left) sides of the ablation line were measured. The difference between these two activation times was termed the difference in isthmic activation times (delta IAT), and was compared to the flutter cycle length. RESULTS: Mean activation times were 173.7 +/- 34.3 ms on the lateral border of the ablation line and 19.1 +/- 12.5 ms on the septal border. Mean delta IAT was 154.6 +/- 27.8 ms and mean atrial flutter cycle length was 257.5 +/- 30.6 ms. delta IAT and flutter cycle length were significantly correlated (r = 0.503, p = 0.0039). The linear regression equation that best described this result was: delta IAT = 37 + (0.46 x flutter cycle). CONCLUSION: After atrial flutter ablation, a difference in isthmic activation times of more than half the flutter cycle length was associated with isthmus conduction block.

Epicardial electroanatomical mapping for intraoperative evaluation of bilateral pulmonary vein isolation.

UNLABELLED: Eight patients (pts; 2 female, 58 +/- 12 yrs) with paroxysmal atrial fibrillation (AF) (duration 39 +/- 20 months) underwent AF surgery, with concomitant myocardial revascularization in 2 pts and myomectomy in 1 (HOCM). AF was idiopathic in the remaining 5 pts. AF surgery consisted of bilateral isolation of the pulmonary veins (PV) using radiofrequency (RF) energy applied epicardially by a heptapolar catheter (Thermaline) in 5 pts and by a new system (Atricure) in 3 pts. For the former, each set of 7 simultaneous applications aimed at a maximum duration of 2 + 2 min., preset temperature 80 degrees C and output 150 watts. With the new system, bipolar applications were carried out; energy delivery was controlled by impedance monitoring and applications were ended after abrupt, sustained elevation of impedance. Epicardial bipolar voltage mapping (CARTO) was performed before and after each RF procedure. Using the navigator catheter, points were recorded at the insertion of each PV and at the non-isolated left atrial posterior wall. The amplitude of the local electrograms (LE) was measured before and after RF applications. If the LE amplitude inside the isolated zone was not 0.1 mV and not reduced by > 80%, a second application was performed. A maximum of 2 epicardial applications were carried out in each pt and if the final result was unsatisfactory, further endocardial applications were performed. RESULTS: Baseline LE amplitudes were > 1 mV in all cases. Successful isolation of right PVs was achieved in 7 pts, after one set of applications in 5 and a second set in 2. Left PV isolation required 2 sets of epicardial applications in all pts, being successful in only 2; 4 pts (one with associated myomectomy and 3 with idiopathic AF) received endocardial applications. Overall, bilateral PV isolation was achieved in 5 pts. CONCLUSIONS: CARTO bipolar voltage mapping is a fast, simple means for evaluation of epicardial PV isolation.

Percutaneous ablation of atrial fibrillation: assessment of outcomes at 1-year follow-up.

OBJECTIVE: Current non-pharmacologic treatment strategies for atrial fibrillation (AF) involve discrete ablation of ectopic foci or isolation of the pulmonary vein (PV) ostia, which have been implicated in the genesis of this rhythm disorder. The aim of this study was to determine intermediate and long-term outcomes after percutaneous AF ablation and predictors of successful treatment. POPULATION AND METHODS: We studied 29 consecutive patients (72% male, mean age 52.3 +/- 13 years) who underwent percutaneous ablation of AF refractory to antiarrhythmic drug therapy. AF was idiopathic in 22 patients and the remaining 7 patients were hypertensive. Six patients had permanent AF and the others had recurrent paroxysmal AF (with at least 1 episode a week). Left atrial size was 40.3 +/- 6.1 mm. A total of 35 ablation procedures were performed, 12 using the focal ablation technique and 23 by PV isolation. Six patients underwent a redo procedure. Patients were evaluated at 1-year follow-up (symptoms, medication, ECG and Holter monitoring). Predictors of successful treatment were identified among baseline clinical variables (age, gender, hypertension), LA size, AF sub-type, ablation technique, and number of isolated PV, using multivariable logistic regression. RESULTS: At 1-year follow-up, 20 patients presented sinus rhythm (69%), of whom 7 were taking antiarrhythmic drugs and remained free of AF relapse. Out of the total of 35 procedures, 2 immediate complications occurred: pericardial tamponade in one patient and right phrenic nerve palsy in another. Predictors of long-term success were absence of a prior history of hypertension and isolation of at least three PV (p = 0.01 for both independent predictors). CONCLUSION: Two out of three patients who underwent AF ablation presented sinus rhythm one year after the intervention. Isolation of at least three PV and idiopathic etiology are independent predictors of successful treatment.

Electronanatomical mapping and ablation of atrial tachycardias with the CARTO system.

UNLABELLED: Variable success rates in the ablation of atrial tachycardias using conventional electrophysiology have been achieved. There is no precise relation between P wave morphology in surface ECG and atrial electrophysiology, and this fact makes it more difficult to locate ectopic atrial foci. The CARTO system creates atrial activation maps that relate an anatomical location to an electrical potential. The aim of this study was to evaluate the efficacy of CARTO guided radiofrequency (RF) ablation of atrial foci. The population consisted of 10 consecutive patients with atrial tachycardia resistant to more than 2 drugs, 7 female, mean age 45 +/- 12 years. CARTO activation maps were constructed based on atrial tachycardia or premature beats. Radiofrequency energy was applied to the earliest activation zone. Immediate success was defined as suppression of ectopic atrial activity. Ectopic foci were located on the ostium of the coronary sinus (3 patients), crista terminalis (1 patient), right atrial appendage (1 patient), interatrial septum (1 patient) and in the pulmonary veins (4 patients). The activation maps contained 85 +/- 35 points. The number of RF applications ranged from 1 to 11 (mean 4). Immediate and 6 month success rate was 90%. We were not able to treat one patient with a focus in the right atrial appendage. No attempt was made to limit procedure or fluoroscopy time in our study. Nonetheless all procedures lasted less than 150 min, and fluoroscopy times were less than 30 minutes. CONCLUSIONS: The CARTO system precisely located ectopic atrial foci, allowing a high success rate in the ablation of focal atrial tachycardias.