Joelci Tonet

Identification and catheter ablation of a zone of slow conduction in the reentrant circuit of ventricular tachycardia in humans

Three patients who had incessant ventricular tachycardia and in whom a zone of slow conduction was identified are presented. Each patients tachycardia was refractory to multiple antiarrhythmic drugs and was being treated with amiodarone at the time of the electrophysiologic study. The ventricular tachycardia cycle length was 500 to 580 ms. In Patients 1 and 2, a single site at the posterolateral wall or low septum in the left ventricle was identified at which overdrive pacing during ventricular tachycardia resulted in ventricular capture with a stimulus to QRS interval of 280 to 400 ms and with little or no change in the configuration of the QRS complexes during pacing as compared with during ventricular tachycardia. In Patient 3, the same phenomenon was observed at two areas in the left ventricle: at the inferior wall, overdrive pacing during ventricular tachycardia resulted in a stimulus to QRS interval of 440 to 470 ms, whereas at the posterolateral wall, the stimulus to QRS interval was 320 to 360 ms. Transcatheter shocks of 100 to 240 J delivered at the pacing sites have been successful in preventing recurrences of ventricular tachycardia over a follow-up period of 10 to 11 months. These observations may be explained by the pacing site being located within a reentrant circuit in a zone of slow conduction bounded by inexcitable tissue between the pacing site and the exit site of the reentrant circuit. In Patient 3, the variable stimulus to QRS intervals are explained by variable proximity of the pacing sites within the slow conduction zone to the exit site of the reentrant circuit.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term efficacy of low doses of quinidine on malignant arrhythmias in Brugada syndrome with an implantable cardioverter-defibrillator: A case series and literature review

BACKGROUND To prevent the recurrence of ventricular arrhythmias (VA) in Brugada syndrome (BrS), only quinidine has been consistently reported to have a beneficial effect. Recommended doses are ≥ 1 g/d. The efficacy of lower doses of quinidine has been suggested on the basis of a few isolated experiences. OBJECTIVES To describe the efficacy and safety of doses ≤ 600 mg/d of quinidine after cardioverter-defibrillator implantation in BrS at 2 referral centers and to compare those results with a comprehensive review of the literature. METHODS In a retrospective analysis of medical records from the 2 centers, 6 men with BrS who received ≤ 600 mg/d of quinidine sulfate or hydroquinidine after cardioverter-defibrillator implantation were identified. Quinidine was initiated after arrhythmic syncope or appropriate shocks, including arrhythmic storm in 4. A literature search was performed to find previous cases with symptomatic BrS reported as having received ≤ 600 mg/d of quinidine. RESULTS Quinidine prevented recurrence of VA in all patients from our series without side effects during a median follow-up of 4 years (from 2 to 8 years). In the literature review, 14 additional adults were found. With the exception of 3, quinidine effectively suppressed arrhythmic events in all of them. Four subjects who discontinued the medication experienced VA recurrence, successfully treated by restarting quinidine. CONCLUSIONS Low doses of quinidine were well tolerated and effective to prevent the recurrence of VA, including arrhythmic storm, in subjects with BrS with an implantable cardioverter-defibrillator. Effectiveness of quinidine or hydroquinidine in doses ≤ 600 mg/d is 85%.

Time- and Frequency-Domain Analyses of the Signal-Averaged ECG in Patients With Arrhythmogenic Right Ventricular Dysplasia

BACKGROUND Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by recurrent ventricular tachycardia of right ventricular origin and a cardiomyopathy with hypokinetic areas involving the free wall of the right ventricle. Subjects have a risk of sudden cardiac death, particularly during sports and strenuous exercise. Routine clinical examinations may be normal, but fragmented or delayed electrograms are usually recorded in the right ventricle of these patients. However, the frequency with which late potentials are detected by conventional time-domain analysis of the signal-averaged ECG (SAECG) is not high. This study evaluated the usefulness of the frequency-domain analysis of the SAECG in addition to the conventional time-domain analysis for a screening test to detect patients with ARVD. METHODS AND RESULTS SAECG was recorded by using a bipolar X, Y, and Z lead system in 28 patients with ARVD (mean age, 38 +/- 13 years) and 35 age-matched normal subjects (mean age, 35 +/- 11 years). The conventional time-domain analysis of the SAECG was performed at two different high-pass filter settings, 25 and 40 Hz, and the low-pass cutoff frequency was fixed at 250 Hz. The fast-Fourier transform analysis of SAECG was performed using a Blackman-Harris window. Area ratio 1 (area of 20 to 50 Hz)/(area of 0 to 20 Hz) and area ratio 2 (area of 40 to 100 Hz)/(area of 0 to 40 Hz) were calculated. In the conventional time-domain analysis, 20 (71%) and 18 (64%) patients had positive criteria at filter settings of 25 and 40 Hz, respectively. In the frequency-domain analysis, 18 (64%) and 20 (71%) patients had abnormal values in area ratios 1 and 2, respectively. Combining the time- and frequency-domain analyses, all patients were judged positive, with a sensitivity of 100% and a specificity of 94%. CONCLUSIONS Each result of the time- and frequency-domain analyses revealed that both methods had equivalent value. Combining the two domain analyses improved the sensitivity without reducing the specificity. These findings suggest that combining the time- and frequency-domain analyses of the SAECG may be useful as a screening test to detect patients with ARVD.

Frequency of supraventricular tachyarrhythmias in arrhythmogenic right ventricular dysplasia

Abstract The incidence of supraventricular tachyarrhythmias in patients with arrhythmogenic right ventricular dysplasia (ARVD) is unknown. 1–5 We report on 72 consecutive patients with the diagnosis of ARVD studied at Jean Rostand Hospital.

Effects of inadvertent atrioventricular block on clinical outcomes during cryoablation of the slow pathway in the treatment of atrioventricular nodal re-entrant tachycardia

AIMS The study aimed at evaluating the long-term effects of transient atrioventricular (AV) block on clinical outcomes during atrioventricular nodal re-entrant tachycardia (AVNRT) cryoablation. METHODS AND RESULTS In 150 consecutive patients (39 +/- 14 years, ineffective anti-arrhythmic drugs 1.9 +/- 1.3), slow-pathway cryoablation for AVNRT was performed. A 7 Fr 6 mm-tip cryocatheter was used. After successful cryomapping (-30 degrees C), defined as jump abolition or AV nodal refractory period prolongation, cryoablation (-80 degrees C for 4 min) was applied if no AV block occurred. Atrioventricular nodal re-entrant tachycardia inducibility was checked after 30 min. Acute success (AVNRT non-inducibility) was achieved in 142 patients (95%). Overall, after a follow-up of 18 +/- 10 months, 118 of 150 patients (79%) were recurrence-free (including 2 patients for whom the procedure was unsuccessful). Among successful procedures, 116 of 142 (82%) patients were recurrence-free. During cryoablation, inadvertent transient AV block of varying degrees occurred in 34 patients (22.7%), namely, increased PR in 17 patients and a 2nd-3rd AV block in the remaining 17. In 24 patients, AV block occurred at the last effective site (increased PR in 13 patients and a 2nd-3rd AV block in 11). In the study population as a whole, univariate predictors of recurrence in the follow-up were AVNRT inducibility (P < 0.001), increased PR at the last effective site (P < 0.001), residual jump (P < 0.02), and small Kochs triangle (X-ray distance < 11 mm between the His and coronary sinus ostium catheters; P < 0.02). Atrioventricular nodal re-entrant tachycardia inducibility (P < 0.03), increased PR (P < 0.01), and small Kochs triangle (P< 0.04) were independently significant. For attempts at the last effective site, 3 groups of patients were compared: 13 patients with increased PR duration (Group A), 11 with a 2nd-3rd AV block (Group B), and 126 without AV block (Group C). Cryo-application time was 277 +/- 203 s in Group A, 75 +/- 87 s in Group B, and 253 +/- 135 s in Group C (A vs. B, P < 0.01; B vs. C, P < 0.001; and C vs. A, P= NS). There was no statistical difference among groups in the atriogram/ventriculogram amplitude ratio at the site of the last attempt, unsuccessful acute procedure, small Kochs triangle, and residual jump. Actuarial incidence of recurrence-free status at 12 months was 38% in A, 82% in B, and 82% in C (A vs. B, P < 0.05; B vs. C, P = NS; and C vs. A, P < 0.001). CONCLUSION All AV blocks occurring during cryoablation were transient, confirming the safety of this method. An increased PR duration at the last effective site is associated with a higher recurrence rate, whereas a 2nd-3rd degree AV block has a recurrence rate similar to that of patients without AV block despite a shorter cryo-application time at the last site.

Efficacy and Safety of Low Doses of Beta-Blocker Agents Combined with Amiodarone in Refractory Ventricular Tachycardia

Twenty patients aged 55 ± 16 years with 40 chronic ventricular tachycardias (VT) refractory to 4.6 ± 1.9 antiarrhythmic drugs, used alone or in combination, were managed by low doses of beta‐blocker agents combined with oral amiodarone (Am), either after loading (1.2 g for 7 days, n: 5) or reloading (1.2 g for 4 days, n: 15) of Am. All patients proved refractory to Am alone. Seven VT were also refractory to endocardial catheter fulguration in six patients. Thirteen patients had coronary artery disease, three had arrhythmogenic right ventricular dysplasia, two had dilated cardiomyopathy, one had valvular disease, and one had no structural heart disease. Ten patients had an EF <30%. Ten patients were in NYHA functional class three. VT was permanent in three patients, daily in three, weekly in seven, paroxysmal in seven. In 11 patients, VT occurred both at day and night. In 11 patients, decrease of the sinus cycle preceeded VT. Oral administration of a daily low dose of a beta blocker agent (acebutolol 100 mg, betaxolol 5–10 mg, metoprolol 50 mg, nadolol 20–40 mg, pindolol 2.5 mg, propanolol 30 mg, sotalol 80–160 mg, terta‐tolol 2.5 mg) combined with 400 mg/day of Am suppressed VT episodes in all patients. None presented heart failure or collapse. The mean reduction of the heart rate was 15% (65 to 55/min). At discharge, exercise ECG (n: 14) induced non sustained VT in two patients. At programmed electrical stimulation (PES) (n: 15), VT was no longer inducible in 4 patients, was slower, well‐tolerated in nine patients, and remained inducible at the same rate in only two patients. Chronic treatment prevents recurrence of VT in 19 patients during a follow‐up of 14 ± 9 months (range 2 to 33). Conclusions: (1) beta blockers agents and Am have strong synergistic effects; (2) antiarrhythmic treatment with low doses of beta blockers could be managed by PES; (3) at the doses used in (his study, all beta blockers presented the same safety; (4) combination of low doses of beta blockers agents with chronic Am therapy inhibit VT.

Cryoablation of atrioventricular nodal reentrant tachycardia: a clinical review.

Slow‐pathway ablation is the treatment of choice for atrioventricular nodal reentrant tachycardia (AVNRT). Cryoablation is effective and safe, but its widespread use seems to be limited by a slightly lower long‐term clinical efficacy when compared to radiofrequency (RF) ablation. However, the occurrence of atrioventricular block requiring permanent pacing with RF remains clinically relevant (about 1%). This review summarizes current experiences accumulated during the last decade with cryotechnology in terms of acute and long‐term results for AVNRT and compares it with those of RF ablation. We describe the advantages of cryo compared to RF ablation. Our data suggest that pursuing procedural endpoint up to slow pathway complete ablation may improve long‐term clinical success of cryoablation. We also focus on potential benefit that can be expected by using cryocatheters leading to larger and deeper freeze. For high‐risk ablations, cryoenergy should be used systematically. (PACE 2012; 35:233–240)

Correlations between long-term results after cryoablation for atrioventricular nodal reentry tachycardia and a residual jump associated or not with a single echo

AIMS While in radiofrequency ablation for atrioventricular nodal reentry tachycardia (AVNRT) a residual jump and a single echo do not seem to substantially modify long-term results, in cryoablation procedures their effects are still under evaluation. The purpose of this study was to evaluate if a residual jump associated or not with an isolated echo is correlated with outcome. METHODS AND RESULTS INCLUSION CRITERIA acute successful slow pathway cryoablation for slow-fast AVNRT. EXCLUSION CRITERIA use of a 4 mm tip cryocatheter, no baseline elicitable jump or inducible AVNRT, and unwanted persistent first degree atrioventricular (AV) block at the end of the procedure. Cryoablation (-80°C × 4 min) was applied after successful cryomapping. Atrioventricular nodal reentry tachycardia inducibility was checked 30 min later on and off isoproterenol. Acute success was defined as AVNRT non-inducibility. Among 332 patients (pts) who had undergone cryoablation from May 2002 to March 2010 in our institutions, 245 of them fulfilled the entry criteria (173 women, mean age 41 ± 16 years, ineffective drugs 1.3 ± 1.1). A 7-Fr 6-mm tip cryocatheter (CryoCath®) was used in all cases. Baseline AV nodal effective refractory period (ERP) was 271 ± 55 ms, post-procedural ERP 331 ± 60 ms (P< 0.001), and the mean of the difference between baseline and post-procedural ERP 63 ± 38 ms. A/V ratio at successful site was 1 ± 0.4. Forty-four pts (18%) had a residual jump at the end of the procedure, and 14 of them had an associated single echo. Global cryoapplication time was 993 ± 797 s. During a follow-up of 40 ± 10 months, 43 pts (17.5%) had recurrences. At 12 months follow-up, actuarial rate of recurrence-free pts was 85% in the group without residual jump (201 pts), 63.3% with residual jump and no echo (30 pts), and 60.6% with residual jump associated with a single echo (P< 0.003 among groups). Univariate predictors of recurrences were persistence of a residual jump (P< 0.001) and total cryoapplication time (P< 0.02). In a multivariate model, only residual jump was independently correlated with recurrences (P< 0.01). CONCLUSIONS In patients undergoing AVNRT cryoablation, slow-pathway suppression is correlated with a better outcome. A single echo is associated with a recurrence risk similar to residual jump without echo. It may be suggested that pursuing a procedural endpoint up to slow pathway complete suppression may improve long-term success.

Techniques and Methods for Catheter Endocardial Fulguration

Fulguration is a new and promising technique for the treatment of cardiac arrhythmias. This paper discusses the methods and equipment used at Jean Rostand Hospital for invasive experimental research related to fulguration. The importance of catheter testing and selection is demonstrated. The most important features of the measurement techniques for both His bundle and ventricular tachycardia recordings are described. The main components of the protocols for fulguration and early post‐operative surveillance are reported. The ODAM Fulgucor is used, augmented by the incorporation of additional pieces of equipment to allow monitoring of current and voltage curves. An electromechanic relay allows for automatic switching from the recording amplifier to the energy source. The video system used includes recording of the image of the last fluoroscopic event with a character generator and an electronic pointer superimposed (when necessary). Computer programs for appropriate timing of predominant events have been developed.

A case of inappropriate sinus tachycardia after atrio-ventricular nodal reentrant tachycardia cryoablation successfully treated by ivabradine

We illustrate a case of persistent inappropriate sinus tachycardia after slow pathway atrio-ventricular (AV) nodal reentrant tachycardia cryoablation, and inadvertent fast pathway lesion with residual first-degree AV block in a 72-year-old man with a small Kochs triangle. At the end of the cryoprocedure, the patient presented with sinus tachycardia 100 b.p.m., while PR was 300 ms. An accelerated sinus rhythm and a PR prolongation persisted over time. The patient was successfully treated with ivabradine with no effect on atrioventricular node conduction.