Catheter ablation of atrioventricular nodal reentrant tachycardia in patients with a prolonged PR interval at sinus rhythm

Radiofrequency transcatheter ablation is an effective and safe treatment for atrioventricular node reentry tachycardia. Slow pathway ablation is considered the ablative technique of choice, but when atrioventricular nodal reentrant tachycardia is associated with a prolonged PR interval at sinus rhythm, a higher risk of delayed atrioventricular (AV) block has been reported. Studies on the subject are few, enrolling low numbers of patients with variable selection criteria and producing different results. Hence, optimal ablation strategy remains controversial. The aim of this study is to review the available knowledge on the topic. Experience from our centers is also briefly reported.

Substrate and Trigger Ablation for Reduction of Atrial Fibrillation (STAR AF): a randomized, multicentre, international trial

AIMS

This multicentre, randomized trial compared three strategies of AF ablation: ablation of complex fractionated electrograms (CFE) alone, pulmonary vein isolation (PVI) alone, and combined PVI + CFE ablation, using standardized automated mapping software.

METHODS AND RESULTS

Patients with drug-refractory, high-burden paroxysmal (episodes >6 h, >4 in 6 months) or persistent atrial fibrillation (AF) were enrolled at eight centres. Patients (n = 100) were randomized to one of three arms. For CFE alone (n = 34), spontaneous/induced AF was mapped using validated, automated CFE software and all sites <120 ms were ablated until AF termination/non-inducibility. For PVI (n = 32), all four PV antra were isolated and confirmed using a circular catheter. For PVI + CFE (n = 34), all four PV antra were isolated, followed by AF induction and ablation of all CFE sites until AF termination/non-inducibility. Patients were followed at 3, 6, and 12 months with a visit, ECG, 48 h Holter. Atrial fibrillation symptoms were confirmed by loop recording. Repeat procedures were allowed within the first 6 months. The primary endpoint was freedom from AF >30 s at 1 year. Patients (age 57 +/- 10 years, LA size 42 +/- 6 mm) were 35% persistent AF. In CFE, ablation terminated AF in 68%. Only 0.4 PVs per patient were isolated as a result of CFE. In PVI, 94% had all four PVs successfully isolated. In PVI + CFE, 94% had all four PVs isolated, 76% had inducible AF with additional CFE ablation, with 73% termination of AF. There were significantly more repeat procedures in the CFE arm (47%) vs. PVI (31%) or PVI + CFE (15%) (P = 0.01). After one procedure, PVI + CFE had a significantly higher freedom from AF (74%) compared with PVI (48%) and CFE (29%) (P = 0.004). After two procedures, PVI + CFE still had the highest success (88%) compared with PVI (68%) and CFE (38%) (P = 0.001). Ninety-six percent of these patients were off anti-arrhythmics. Complications were two tamponades, no PV stenosis, and no mortality.

CONCLUSION

In high-burden paroxysmal/persistent AF, PVI + CFE has the highest freedom from AF vs. PVI or CFE alone after one or two procedures. Complex fractionated electrogram alone has the lowest one and two procedure success rates with a higher incidence of repeat procedures. ClinicalTrials.gov identifier number NCT00367757.

Characteristics of recurrent ventricular fibrillation associated with inferolateral early repolarization role of drug therapy

OBJECTIVES

Our purpose was to evaluate the efficacy of antiarrhythmic drugs (AADs) in recurrent ventricular fibrillation (VF) associated with inferolateral early repolarization pattern on the electrocardiogram.

BACKGROUND

Although an implantable cardioverter-defibrillator is the treatment of choice, additional AADs may be necessary to prevent frequent episodes of VF and reduce implantable cardioverter-defibrillator shock burden or as a lifesaving therapy in electrical storms.

METHODS

From a multicenter cohort of 122 patients (90 male subjects, age 37 +/- 12 years) with idiopathic VF and early repolarization abnormality in the inferolateral leads, we selected all patients with more than 3 episodes of VF (multiple) including those with electrical storms (> or =3 VF in 24 h). The choice of AAD was decided by individual physicians. Follow-up data were obtained for all patients using monitoring with implantable defibrillator. Successful oral AAD was defined as elimination of all recurrences of VF with a minimal follow-up period of 12 months.

RESULTS

Multiple episodes of VF were observed in 33 (27%) patients. Electrical storms (34 +/- 47 episodes) occurred in 16 and were unresponsive to beta-blockers (11 of 11), lidocaine/mexiletine (9 of 9), and verapamil (3 of 3), while amiodarone was partially effective (3 of 10). In contrast, isoproterenol infusion immediately suppressed electrical storms in 7 of 7 patients. Over a follow-up of 69 +/- 58 months, oral AADs were poorly effective in preventing recurrent VF: beta-blockers (2 of 16), verapamil (0 of 4), mexiletine (0 of 4), amiodarone (1 of 7), and class 1C AADs (2 of 9). Quinidine was successful in 9 of 9 patients, decreasing recurrent VF from 33 +/- 35 episodes to nil for 25 +/- 18 months. In addition, quinidine restored a normal electrocardiogram.

CONCLUSIONS

Multiple recurrences of VF occurred in 27% of patients with early repolarization abnormality and may be life threatening. Isoproterenol in acute cases and quinidine in chronic cases are effective AADs.

Size dependence of the Mössbauer recoilless fraction in β-Sn nanocrystals

We study the size dependence of the Mössbauer recoilless fraction in β-Sn nanocrystals by performing conversion electron Mössbauer spectroscopy at different temperatures. The Mössbauer recoilless fraction is intimately related to dynamical processes involving the nuclei during the γ-ray emission. The β-Sn nanocrystals are embedded in a SiO(2) matrix, and they have a mean diameter ranging from 7 to 17 nm. A lowering of the recoilless fraction with decreasing cluster size is observed. The smallest nanocrystals reveal a 60% reduction of the recoilless fraction compared to the bulk value, while for the largest clusters we observe the same Mössbauer recoilless fraction as in the bulk. This suggests that the dynamical properties of the β-Sn nanocrystals in SiO(2) approach those of the bulk for a critical mean diameter above 16 nm. The experimental results are compared with theoretical values obtained by a continuum model in which the relevant parameters are determined ab initio.

Early complications of pulmonary vein catheter ablation for atrial fibrillation: A multicenter prospective registry on procedural safety

BACKGROUND

Data on the procedural safety of pulmonary vein radiofrequency catheter ablation for atrial fibrillation (AF) are as yet scant.

OBJECTIVE

The aims of the present study were to prospectively evaluate the incidence of early complications of pulmonary vein ablation for AF in an unselected population of consecutive patients, and to identify possible predictors.

METHODS

From April 2005 to October 2006, data from 1,011 consecutive patients who were undergoing radiofrequency catheter ablation for every type of AF in 10 Italian centers were collected. All complications occurring from the admission of the patient up to the 30th day were considered.

RESULTS

No procedure-related death was observed. Complications occurred in 40 patients (3.9%): 12 (1.2%) had peripheral vascular complications, 8 (0.8%) had conservatively treated pericardial effusion, 6 (0.6%) had cardiac tamponade (successfully drained), 5 (0.5%) had cerebral embolisms, 4 (0.4%) presented pulmonary vein stenosis >50%, and 5 (0.5%) presented other isolated adverse events. History of coronary artery disease (odds ratio 5,603, 95% confidence interval 1,559 to 20,139, P < .008) characterized patients who presented with hemorrhagic complications.

CONCLUSION

Early complications of pulmonary vein catheter ablation seem to be fewer than in the early years of AF ablation, but still occur in 3.9% of procedures.

Development of a parallel-plate avalanche counter to perform conversion electron Mössbauer spectroscopy at low temperatures

We describe an experimental setup based on a sealed parallel-plate avalanche counter, which allows conversion electron Mössbauer spectroscopy at temperatures down to 120 K. A study of the counting gas performances is carried out in order to find out the appropriate operating conditions. The detector can work in a wide range of pressures and voltages at room and low temperatures, for both iron- and tin-based Mössbauer transitions. An estimation of the gas gain is obtained by using a simple approach, which considers the avalanche gas process in parallel-plate geometry. The gas gain as a function of the filling pressure shows a maximum at room temperature and a monotonic increase at low temperature. The experimental setup has been tested with the determination of the Debye temperature of beta-Sn, SnO(2), and epsilon-FeSi.

Treatment of macro-re-entrant atrial tachycardia based on electroanatomic mapping: identification and ablation of the mid-diastolic isthmus

AIMS

This multicentre prospective study evaluated the ability of electroanatomic mapping (EAM) using a specific parameter setting to identify clearly the mid-diastolically activated isthmus (MDAI) and guide ablation of macro-re-entrant atrial tachycardia (MAT).

METHODS AND RESULTS

Consecutive patients with MAT, different from typical isthmus-dependent atrial flutter, were enrolled. EAM was performed using a specific setting of the window of interest, calculated to identify the MDAI and guide ablation of this area. Sixty-five patients exhibiting 81 MATs (mean cycle length 308 +/- 68 ms) were considered. Thirty-two (49.2%) had previous heart surgery. In 79 of 81 morphologies (97.5%), EAM reconstructed 95.9 +/- 4.3% of the tachycardia circuit and identified the MDAI; 23 of the 79 morphologies (29.1%) were double-loop re-entry. Mapping of two morphologies was incomplete due to MAT termination after catheter bumping. In 73 of 79 mapped morphologies (92.4%), abolition of the MAT was obtained by 13.2 +/- 12.4 applications. During the 14 +/- 4 month follow-up, MAT recurred in 4 of the successfully treated patients (6.8%).

CONCLUSION

EAM using a specific parameter setting proved highly effective at identifying the MDAI in MAT, even in patients with previous surgery and multiple re-entrant loops. Ablation of the MDAI yielded acute arrhythmia suppression with low rate of recurrence during follow-up.

A clinical and health-economic evaluation of pulmonary vein encircling ablation compared with antiarrhythmic drug treatment in patients with persistent atrial fibrillation (Catheter Ablation for the Cure of Atrial Fibrillation-2 study)

AIMS

Catheter Ablation for the Cure of Atrial Fibrillation 2 study is a prospective, randomized trial aimed to demonstrate the efficacy of catheter ablation with combined lesions in the right and left atria, in preventing atrial fibrillation (AF) recurrences among patients with recurrent persistent AF refractory to one antiarrhythmic drug, in comparison with the best pharmacological therapy.

METHODS AND RESULTS

Enrolment is limited to patients aged between 18 and 70 years who have experienced at least one documented relapse of persistent AF during antiarrhythmic drug therapy. One hundred and twenty-six patients will be randomized to ablation or antiarrhythmic drug therapy in a 2 : 1 manner. In the ablation group, the patients will undergo right and left atrial linear ablation. Control group patients will be treated with the best antiarrhythmic drug. After an initial blanking period of 2 months patients will be followed for 24 months. Primary endpoint of the study is the absence of documented persistent atrial tachyarrhythmias relapse during the first 24 months after the blanking period. Enrolment is scheduled in 14 centres in Italy, UK, Austria, and Finland. Seventy-two patients have currently been enrolled.

CONCLUSION

This study will provide important data about the efficacy of catheter ablation in comparison with antiarrhythmic drugs for the treatment of persistent AF.

Anatomical and electrophysiological approach to atrial fibrillation ablation: technical limitations

OBJECTIVE

Pulmonary vein (PV) disconnection by radiofrequency (RF) catheter ablation has been reported to cure atrial fibrillation (AF). Different techniques have been proposed. The aim of this study was to evaluate the technical limitations of both anatomical and electrophysiological approaches.

METHODS

A total of 110 PVs were ablated in 26 consecutive patients (23 male, 3 female, mean age 51 +/- 9.5 years) with paroxysmal (n = 19, 73%), persistent (n = 3, 12%) or permanent (n = 4, 15%) AF. Accurate reconstructions of the PV ostia were obtained using fluoroscopy, electrophysiology, and the CARTO mapping system. Electrophysiological mapping was attempted in all PVs by means of a decapolar circular catheter. RF ablation was performed in a single-blind fashion in order to anatomically create circumferential lines around each PV. Completeness of anatomically-guided, circumferential RF lesions around the PVs was established by the physician using the CARTO system, who was unaware of the decapolar circular catheter electrophysiological recordings of the PVs. If PV potentials persisted, RF delivery was targeted to the electrophysiological breakthroughs.

RESULTS

All PV ostia were anatomically ablated by performing circumferential RF lesions. Among 110 PVs, 73 (66%) were fully mapped by use of circular catheters. After anatomical ablation, electrical disconnection was achieved in 44/73 PVs (60%). In the remaining 29 PVs (40%), a median of one RF pulse (mean 1.8 +/- 1.4) was necessary to achieve complete PV disconnection. Total procedure duration, fluoroscopy time, and RF delivery time were 232 +/- 29, 50 +/- 16 and 39 +/- 11 min, respectively. Pericardial effusion occurred in one patient after the procedure. After 10.5 +/- 6.4 months, 21 patients (81%) were in stable sinus rhythm and 13 of them (62%) discontinued all drugs after 6 months. Only 4 patients (15%) required two procedures.

CONCLUSIONS

Electrical PV disconnection cannot be achieved in many PVs by means of a pure anatomical approach. On the other hand, electrophysiological mapping cannot be performed in many PVs owing to anatomical variations. An integrated approach might overcome these limitations.

Comparison Between Anatomical and Integrated Approaches to Atrial Fibrillation Ablation: Adjunctive Role of Electrical Pulmonary Vein Disconnection

INTRODUCTION

The aim of this study was to compare the outcome of anatomical pulmonary vein (PV) radiofrequency (RF) ablation with that of an integrated approach (anatomical with electrophysiological confirmation of PV disconnection).

METHODS

Sixty consecutive patients affected by drug-refractory paroxysmal (39), persistent (13), and permanent (8) atrial fibrillation (AF) were assigned to an anatomical (group A: 30 patients; 25 male, 5 female, mean age: 55 +/- 7 years) or integrated approach (group B: 30 patients; 26 male, 4 female, mean age: 52 +/- 9 years). In all cases, RF ablation was performed by means of the Carto system in order to anatomically create circumferential lines around PVs. In group B, the persistence of PV potentials was then assessed with a multipolar circular catheter. If PV potentials persisted, RF pulses targeting the electrophysiological breakthroughs were delivered to disconnect PVs.

RESULTS

Total procedure duration, fluoroscopy time, and RF delivery time were similar in both groups: 227 +/- 43, 50 +/- 23, and 43 +/- 16 minutes (group A); 232 +/- 32, 55 +/- 15, and 42 +/- 10 minutes (group B), respectively (ns). One asymptomatic PV stenosis and one pericardial effusion occurred in group A and B, respectively. After 15.4 +/- 7.4 months, 17 (57%) group A patients and 25 (83%) group B patients were in stable sinus rhythm (P = 0.02) (RR 1.78; 95% CI: 1.7-2.9).

CONCLUSIONS

PV ablation by means of an integrated anatomical and electrophysiological approach seems more effective than a purely anatomical RF ablation approach. Electrophysiological confirmation of PV disconnection could be a useful marker of successful RF treatment of AF.

Pace mapping of Koch's triangle reduces risk of atrioventricular block during ablation of atrioventricular nodal reentrant tachycardia

INTRODUCTION

Slow pathway (SP) ablation of AV nodal reentrant tachycardia (AVNRT) can be complicated by second- to third-degree AV block. We assessed the usefulness of pace mapping of Koch's triangle in preventing this complication.

METHODS AND RESULTS

Nine hundred nine consecutive patients undergoing radiofrequency ablation of AVNRT were analyzed. Group 1 (n=487) underwent conventional slow pathway ablation. Group 2 (n=422) underwent ablation guided by pace mapping of Koch's triangle, which located the anterogradely conducting fast pathway (AFP) based on the shortest St-H interval obtained by stimulating the anteroseptal, midseptal, and posteroseptal aspects of Koch's triangle. In group 2, AFP was anteroseptal in 384 (91%), midseptal in 33 (7.8%), and posteroseptal or absent in 5 (1.2%). In 32 of 33 patients with midseptal AFP, slow pathway ablation was performed strictly in the posteroseptal area. In 4 of 5 patients with posteroseptal or no AFP, retrograde fast pathway was ablated. Two patients refused ablation. Persistent second- to third-degree AV block was induced in 7 (1.4%) of 487 group 1 patients versus 0 (0%) of 422 group 2 patients (P=0.038). Ablation was successful in all patients in whom ablation was performed.

CONCLUSION

Pace mapping of Koch's triangle identifies patients in whom the AFP is absent or is abnormally close to the slow pathway. In these cases, guiding ablation helps to avoid AV block.

Different Clinical Courses and Predictors of Atrial Fibrillation Occurrence After Transisthmic Ablation in Patients with Preablation Lone Atrial Flutter, Coexistent Atrial Fibrillation, and Drug Induced Atrial Flutter

The aim of this prospective study was to compare the long-term follow-up after transisthmic ablation of patients with preablation lone atrial flutter, coexistent AF, and drug induced atrial flutter to determine if postablation AF followed a different clinical course and displayed different predictors in these groups. The study evaluated 357 patients who underwent transisthmic ablation for typical atrial flutter. These were divided into four groups according to their preablation history. Group A included patients with typical atrial flutter and without preablation AF (n=120, 33.6%). Group B included patients with preablation AF and spontaneous atrial flutter (n=132, 37.0%). Group C patients had preablation AF and atrial flutter induced by treatment with IC drugs (propafenone or flecainide) (n=63, 17.6%) Group D included patients with preablation AF and atrial flutter induced by treatment with amiodarone (n=42, 11.8%). During a mean follow-up of 15.2 double dagger 10.6 months (range 6-55 months) AF occurred more frequently in groups B (56.1%) and C (57.1%) patients than in groups A (20.8%, P <0.0001) and D (31.0%, P <0.0001) patients. The results of multivariate analysis revealed that different clinical and echocardiographical variables were correlated with postablation AF occurrence in the different groups. Patients with atrial flutter induced by amiodarone have a significantly lower risk of postablation AF than patients with spontaneous atrial flutter and AF, and those with atrial flutter induced by IC drugs. Different clinical and echocardiographical variables predict postablation AF occurrence in different subgroups of patients.

Long term follow up of radiofrequency catheter ablation of atrial flutter: clinical course and predictors of atrial fibrillation occurrence

OBJECTIVES

To evaluate the time to onset and the predictors of atrial fibrillation (AF) during long term follow up of patients with typical atrial flutter (AFL) treated with transisthmic ablation.

DESIGN

Prospective multicentre study.

METHODS AND RESULTS

383 patients (75.4% men, mean (SD) age 61.7 (11.1) years) who underwent transisthmic ablation for typical AFL were investigated. In 239 patients (62.4%) AF was present before ablation. Ablation proved successful in 367 patients (95.8%). During a mean (SD) follow up of 20.5 (12.4) months, 41.5% of patients reported AF. The cumulative probability of postablation AF increased continuously as time passed: it was 22% at six months, 36% at one year, 50% at two years, 58% at three years, and 63% at four years.

CONCLUSIONS

AF occurred in a large proportion of patients after transisthmic catheter ablation of typical AFL. The occurrence of AF was progressive during follow up. Preablation AF, age < 65 years, and left atrial size > 50 mm are associated with postablation AF occurrence.

Left Atrial Radiofrequency Ablation During Cardiac Surgery in Patients with Atrial Fibrillation

INTRODUCTION

Intraoperative left atrial radiofrequency (RF) ablation recently has been suggested as an effective surgical treatment for atrial fibrillation (AF). The aim of this study was to verify the outcome of this technique in a controlled multicenter trial.

METHODS AND RESULTS

One hundred three consecutive patients (39 men and 65 women; age 62 +/- 11 years) affected by AF underwent cardiac surgery and RF ablation in the left atrium (RF group). The control group consisted of 27 patients (6 men and 21 women; age 64 +/- 7 years) with AF who underwent cardiac surgery during the same period and refused RF ablation. Mitral valve disease was present in 89 (86%) and 25 (92%) patients, respectively (P = NS). RF endocardial ablation was performed in order to obtain isolation of both right and left pulmonary veins, a lesion connecting the previous lines, and a lesion connecting the line encircling the left veins to the mitral annulus. Upon discharge from the hospital, sinus rhythm was present in 65 patients (63%) versus 5 patients (18%) in the control group (P < 0.0001). Mean time of cardiopulmonary bypass was longer in the RF group (148 +/- 50 min vs 117 +/- 30 min, P = 0.013). The complication rate was similar in both groups, but RF ablation-related complications occurred in 4 RF group patients (3.9%). After a mean follow-up of 12.5 +/- 5 months (range 4-24), 83 (81%) of 102 RF group patients were in stable sinus rhythm versus 3 (11%) of 27 in the control group (P < 0.0001). The success rate was similar among the four surgical centers. Atrial contraction was present in 66 (79.5%) of 83 patients in the RF group in sinus rhythm.

CONCLUSION

Endocardial RF left atrial compartmentalization during cardiac surgery is effective in restoring sinus rhythm in many patients. This technique is easy to perform and reproducible. Rare RF ablation-related complications can occur. During follow-up, sinus rhythm persistence is good, and biatrial contraction is preserved in most patients.

Supraventricular arrhythmia before and after surgical closure of atrial septal defects: spectrum, prognosis and management

Supraventricular arrhythmias are often observed in patients before and after atrial septal defect repair. Although several papers report different incidences of sustained supraventricular arrhythmias, postoperative 'incisional' macroreentrant tachycardias have not been systematically investigated.

METHODS

We reviewed 136 consecutive patients (79 female, 57 male, mean age 36.8+/-17.8 years) who underwent atrial septal defect repair at our institutions between January 1990 and January 1999. Coexisting valve disease requiring surgical intervention was noted in 13 patients (9.5%). The mean follow-up period was 78.8+/-30.1 months.

RESULTS

Sustained supraventricular arrhythmias occurred in 12 patients (8.8%) before surgery (atrial fibrillation in 11 patients). Using multivariate analysis the occurrence of arrhythmia significantly correlated with the presence of coexisting heart disease (P< 0.001) and age at surgery (P=0.011) After surgery sustained supraventricular arrhythmias were recorded in 16 patients (11.7%). Eleven of them had atrial fibrillation, permanent in 8 cases, 4 'incisional' macroreentrant atrial tachycardia and 1 atrioventricular re-entry tachycardia. There was a significant correlation between pre and postoperative arrhythmia (P< 0.001). Two of the 4 patients with macroreentrant atrial tachycardia underwent successful radiofrequency catheter ablation, whereas the arrhythmia was controlled medically in the remaining 2 patients.

CONCLUSIONS

Atrial fibrillation remains the most frequent form of arrhythmia before and after surgical closure of atrial septal defects in adulthood, and relates to age at the time of repair and coexisting heart disease. Incisional macroreentrant atrial tachycardia is an identifiable, albeit less common, form of tachycardia, which can be treated by transcatheter ablation.

Radiofrequency ablation of atrioventricular nodal reentrant tachycardia: the risk of intraprocedural, late and long-term atrioventricular block. The Veneto Region multicenter experience

BACKGROUND

Radiofrequency ablation of either the fast or the slow pathway in atrioventricular nodal reentrant tachycardia (AVNRT) can be complicated by transient or permanent atrioventricular (AV) block. Little is known about the possibility of AV block occurring during the first weeks after the procedure and nothing about the risk of AV block during the long-term follow-up.

METHODS

To clarify these latter points, from February 1990 to December 2000 we enrolled 510 consecutive patients (56 males, 454 females, mean age 55 +/- 16 years) with AVNRT. The target of ablation was the fast pathway in 29 patients (group A) and the slow pathway in 474 (group B), while in 7 (group C) the slow pathway was targeted after unsuccessful fast pathway ablation. Follow-up was available for 488/510 (95.6%). The length of follow-up was 8.2 +/- 2.4 years in group A, 3.4 +/- 2.4 years in group B (83 group B patients had a follow-up > 6 years: 7.3 +/- 0.8 years), and 7.3 +/- 2.4 years in group C.

RESULTS

The success rates were 93, 99 and 100% in the three groups respectively. Intraprocedural II-III degree AV block occurred in 6/29 patients (20%) of group A, in 11/474 patients (2.3%) of group B and in 3/7 patients (42%) of group C. In all patients of groups A and C, the II-III degree AV block was transient. In contrast, in 6/474 patients of group B (1.2%, 2 II degree and 4 III degree AV block) the block still persisted at the end of the procedure. Within 7 days of the procedure, a late persistent II-III degree AV block developed in 1/29 patients (3.4%, 1 III degree) of group A, in 1/474 patients (0.2%, 1 II degree) of group B and in 0/7 patients of group C. In 1 out of 6 patients of group B who developed an intraprocedural persistent AV block, 1:1 conduction resumed within the first week. A definitive pacemaker was implanted for permanent III degree AV block in 1/29 patients of group A (3.4%), in 4/474 patients (0.8%) of group B and in 0/7 patients of group C. In the remaining 2/474 group B patients with permanent II degree AV block, a pacemaker was not implanted. During follow-up, no patient presented with a II-III degree AV block related to the ablation. In group B, 2 patients received a pacemaker implant for reasons unrelated to the ablation (1 sick sinus syndrome, 1 progressive intraventricular conduction disease).

CONCLUSIONS

The risk of permanent AV block in patients who undergo fast or slow pathway ablation is low and limited to the procedure or to the days immediately after the procedure, and there is no risk of II-III degree AV block during long-term follow-up.

Pacemapping of the triangle of Koch: a simple method to reduce the risk of atrioventricular block during radiofrequency ablation of atrioventricular node reentrant tachycardia

Slow pathway ablation in common AVNRT can be complicated by total AV block. When radiofrequency energy is delivered to the posterior aspect of the triangle of Koch, total AV block may be the consequence of the absence of anterograde conduction along the fast pathway or of inadvertent damage to a fast pathway abnormally located close to the slow pathway. To localize the anterogradely conducting fast pathway, the triangle of Koch was pacemapped in 72 patients who underwent the ablation of common AVNRT. In all cases, before ablation the St-H interval was calculated by stimulating the anteroseptal (AS), mid-septal (MS), and posteroseptal (PS) aspect of the triangle of Koch at a rate slightly faster than the sinus rate. In all patients, common AVNRT was induced. In 64 (89%) of 72 patients (group A) the shortest St-H interval was recorded on stimulating the AS region. In six (8%) patients (group B) the shortest St-H interval was recorded on stimulating the MS region. Finally, in two (3%) patients (group C) the shortest St-H interval was recorded stimulating in the PS region. In group C, AH interval, calculated on stimulating in the AS region, was significantly longer than in patients of groups A and B (200 +/- 99 ms vs 64 +/- 18 and 62 +/- 3, respectively). In group A, on stimulating in the AS, MS, and PS regions, the AH interval remained constant in all patients. In contrast, in groups B and C on stimulation in the MS and PS regions, AH interval shortened (in group B from 56 +/- 8 to 27 +/- 37 and 37 +/- 14, respectively; in group C from 200 +/- 99 to 170 +/- 100 and to 137 +/- 109, respectively). In groups A and B, a posteroseptal slow pathway, and in group C, an anteroseptal retrograde fast pathway were successfully ablated without AV block. Pacemapping of the triangle of Koch can help to recognize patients in whom the anterograde conducting fast pathway is abnormally located far from the anteroseptal region or in whom anterograde conduction of the fast pathway is absent. In these cases the risk of AV block can be reduced by performing slow pathway ablation in a site sufficiently far from the site of the anterograde fast pathway or ablating the retrogradely conducting fast pathway.

Long-term follow-up after atrioventricular nodal ablation and pacing: low incidence of sudden cardiac death

Sudden cardiac death (SCD) has been reported in patients with drug refractory AF who underwent AV nodal ablation and pacing. However, whether SCD in these patients is related to the underlying heart disease or to the ablating and pacing procedure remains uncertain. Between May 1987 and January 1997, AV nodal ablation was performed in 585 patients (mean age 66 +/- 11 years) with drug-resistant, paroxysmal (n = 308) or chronic (n = 277) AF in 12 Italian centers. Lone AF was present in 133 patients. After AV junction ablation, patients underwent VVIR (454 patients) or DDDR (131 patients) pacemaker implantation. At a follow-up of 33.6 +/- 24.2 months, 80 (13.7%) deaths were recorded: 40 noncardiac, 23 nonsudden, and 17 sudden cardiac death (3%, 1.04% per year). Among five variables, including age. NYHA functional class, presence of heart disease, paroxysmal or chronic AF, previous embolic events, and LVEF, the presence of heart disease (P = 0.007) and a LVEF < 0.45, (P = 0.003) were associated with a higher risk of SCD. Analysis of SCD-free survival by log-rank test showed a higher incidence of SCD in patients with LVEF < 0.45 (P = 0.0001) and with coronary artery disease (P = 0.005). In this large cohort, a low incidence of long-term SCD after AV nodal ablation and pacing for drug-refractory AF was observed. The presence of underlying heart disease and the extent of baseline LV dysfunction were associated with an increased likelihood of SCD.

Orthodromic tachycardia with atrioventricular dissociation: evidence for a nodoventricular (Mahaim) fiber

We describe a patient in whom two tachycardias with AV dissociation were inducible by ventricular extrastimulation. The first tachycardia was characterized by a narrow QRS preceded by a His deflection with an HV interval identical to that recorded in sinus rhythm (40 ms). Premature ventricular depolarization delivered when the His bundle was refractory advanced the next His deflection. These findings suggest the presence of a nodoventricular bypass tract involved in an orthodromic tachycardia. The second tachycardia was induced after propafenone infusion and exhibited a wide QRS complex with left bundle branch block morphology; each ventricular complex was consistently associated with a His deflection with a HV interval of -15 ms. The second tachycardia may be considered to represent an antidromic tachycardia through the nodoventricular tract. However, a ventricular tachycardia cannot be excluded.

Thromboembolism after atrioventricular node ablation and pacing: long term follow up

OBJECTIVE

To assess the incidence of arterial embolic events in patients with high rate, drug resistant, severely symptomatic paroxysmal and chronic atrial fibrillation who have undergone atrioventricular (AV) node ablation and permanent pacing.

DESIGN

Multicentre retrospective cohort study. PATIENTS AND MANAGEMENT: From May 1987 to January 1997, AV node ablation was performed in 585 severely symptomatic patients (mean (SD) age 66 (11) years) with high rate, drug resistant paroxysmal atrial fibrillation (308) or chronic atrial fibrillation (277). Lone atrial fibrillation was present in 133 patients, while the remaining 452 suffered from dilated, ischaemic, or valvar heart disease. Patients underwent VVIR (454) or DDDR (131) pacemaker implantation, after AV node ablation. Antiplatelet agents were given to 202 patients, warfarin to 187 patients.

RESULTS

During a follow up of 33.6 (24.2) months, thromboembolic events were observed in 17 patients (3%); the actuarial occurrence rates of thromboembolism were 1.1%, 3%, 4.2%, and 7.4% after one, three, five, and seven years, respectively. Among five variables, univariate analysis showed that only the presence of chronic atrial fibrillation at the time of ablation (relative risk (RR) = 1.8, 95% confidence interval (CI) = 1.02 to 3. 20, p = 0.04) and the need for warfarin treatment (RR = 1.6, 95% CI 1.00 to 2.71, p = 0.048) were associated with a significantly higher risk of occurrence of thromboembolic events. On multivariate analysis the only predictor of embolic events during the follow up was the presence of chronic atrial fibrillation.

CONCLUSIONS

Data from this large cohort of patients indicate a fairly low incidence (1.04% per year) of thromboembolic events after AV node ablation and pacing for drug refractory, high rate atrial fibrillation.

[Permanent junctional reciprocating tachycardia (Coumel type): an unusual location of a retrograde accessory pathway]

Permanent junctional reentrant tachycardia (PJRT) is an uncommon form of tachycardia that is usually due to an atrioventricular reentry via a right posteroseptal accessory pathway with decremental properties. We describe a case of PJRT that showed evidence of two accessory pathways located both left and right. A 63-year-old woman was referred to our institution for radiofrequency (RF) ablation of a permanent form of regular narrow QRS tachycardia (T) (cycle length 520 ms) with long RP interval (380 ms); P wave was negative in inferior leads, negative in D1 and flat in aVL. During sinus rhythm, AH and HV intervals were 110 ms and 50 ms respectively. The atrioventricular anterograde conduction curve was continuous. A decremental retrograde conduction via a left posterior pathway until ventricular effective refractory period (210 ms) was evident. Tachycardia inducible with both atrial and ventricular programmed stimulation was almost incessant. During tachycardia, a premature ventricular depolarization delivered when His bundle was refractory was able to advance the next atriogram, and tachycardia could be interrupted by a ventricular depolarization without atrial capture. During right atrial mapping, an earliest atrial activation was found in the mid-septal position just above the coronary sinus ostium and RF application caused a transient interruption of T (3 minutes). Tachycardia resumed with basal characteristics, but no evidence of earlier right atrial activation was found during atrial mapping. Successful RF ablation was performed via retrograde aortic catheterization in the left posterior region. This case showed evidence of a left posterior pathway causing PJRT. However, the transient successful ablation in the right mid-septal region and the lack of evidence of right early atrial activation after RF application could account for the presence of an additional right accessory pathway or a strand of the same broad left pathway.

Clinical usefulness of slow pathway ablation in patients with both paroxysmal atrioventricular nodal reentrant tachycardia and atrial fibrillation

Some patients with atrioventricular (AV) node reentrant tachycardia (AVN RT) also presented with atrial fibrillation (AF). In this study we demonstrate that slow pathway ablation is able to suppress both AVN RT and AF in subjects without structural heart abnormalities, whereas in patients with structural heart abnormalities after ablation AF frequently recurs.

Efficacy of intravenous propafenone in termination of atrial flutter by overdrive transesophageal pacing previously ineffective

Fifty patients with symptomatic type I atrial flutter in whom termination of the arrhythmia with transesophageal stimulation was unsuccessful were randomized to undergo a repeat procedure after intravenous propafenone (n = 25) or placebo (n = 25). Immediate sinus rhythm recovery rate was 36% in the propafenone group and 4% in the placebo group (p = 0.005), indicating that intravenous propafenone increases the rate of successful transesophageal stimulation and can be used when a first attempt at conversion is ineffective.

Global and regional left ventricular function in heart transplant patients: an angiographic follow-up study

We studied the global and regional left ventricular function, its determinants and its modification with time, in orthotopic heart transplant recipients. We reviewed the left ventricular cineangiography performed 1 (50 patients), 2 (33 patients), 3 (18 patients), and 4 (seven patients) years after operation. Regional wall motion was quantitatively evaluated by the area method. All patients had angiographically normal coronary arteries and no evidence of acute rejection at the time of the study. One year after heart transplantation, cardiac index and left ventricular ejection fraction were mildly but significantly lower than normal. Cardiac index was more than 2.5 L/min/m2 in all but one patient, and ejection fraction was more than 50% in all patients. Only previous acute cardiac rejection necessitating therapy and arterial hypertension showed some influence on the left ventricular function. Two years after operation, the left ventricular end-diastolic volume was increased, and left ventricular mass-volume ratio decreased compared with year 1. Three years after operation, an increase of left ventricular end-diastolic pressure and of left ventricular ejection fraction was also evident. Four years after operation, the heart rate was higher, compared with previous years. Even if the changes in the parameters of left ventricular function were significant, they were small in terms of absolute value. Regional hypokinesia was detected 1 year after heart transplantation in eight patients, involving one segment in six patients and two segments in two patients.(ABSTRACT TRUNCATED AT 250 WORDS)

[An aneurysm of the interatrial septum associated with Ebstein's anomaly: a case report]

Atrial septal aneurysm (ASA) is a known morphologic abnormality and has been largely investigated with two-dimensional echocardiography. Its association with other congenital or acquired diseases has also been described. However, the presence of ASA and concomitant Ebstein's anomaly in the same patient is a very unexpected finding in an adult subject. We therefore present the case of a young asymptomatic woman with this association.

[The behavior of the arterial pressure at rest and under exertion in normotensive and hypertensive subjects exposed to acute hypoxia at a median altitude]

In order to evaluate blood pressure changes at rest and during effort in response to moderate altitude acute hypoxia, we performed noninvasive blood pressure monitoring and maximal bicycle stress testing in 10 normotensive and 13 untreated mild hypertensive subjects at sea-level and in a mountain resort (m. 2572). Blood pressure was measured every 10 minutes by the Spacelabs 5200 pressurometer and bicycle stress test was performed at initial workload of 50 watts and steps of 50 watts every 3 minutes until exhaustion. Mean systolic blood pressure resulted unchanged in the normotensive subjects (120.8 +/- 10.6 vs 121.5 +/- 6.9 NS) while in the hypertensive ones it increased slightly at 2572 m. (131.0 +/- 12.3 vs 137.0 +/- 13.1 NS). Mean diastolic blood pressure did not increase significantly at 2572 m in either group (respectively from 74.5 +/- 90 to 80.1 +/- 7.9 NS and from 88.3 +/- 10.2 to 94.7 +/- 10.7 NS) even if blood pressure increase was relevant in some hypertensive subjects. During the monitoring, heart rate increased at 2752 m in both groups, even if this difference was significant in the hypertensive group only (respectively 82.8 +/- 11.8 vs 94.3 +/- 13.2 in normotensive subjects-NS-and 88.0 +/- 6.3 vs 104.0 +/- 7.8 in hypertensive subjects-p less than 0.001). During the ergometric test submaximal systolic blood pressure (100 and 150 watts) increased slightly in both groups, but this difference was significant in hypertensive subjects at a workload of 150 watts only (208.3 +/- 18.2 vs 219.3 +/- 19.2 p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[The effects of enalapril on basal arterial pressure at rest and during exercise and on cardiac performance in hypertensive athletes]

A dose of 10 mg of enalapril was administered once a day to regularly trained hypertensive athletes (mean age 39 +/- 8.9 range 29-51) in order to evaluate the effect of the drug on ambulatory blood pressure and on blood pressure and physical performance during stress testing. STUDY DESIGN. This investigation was a randomized, double blind, cross-over versus placebo trial. At first, subjects whose blood pressure met the entry criteria (casual diastolic blood pressure greater than or equal to 95 mmHg), were subjected to 24-hour ambulatory blood pressure monitoring and maximal upright bicycle stress testing including measurement of O2 uptake. Then they were randomly assigned to treatment with placebo or enalapril. After one month they repeated stress testing and then they were crossed over. Stress testing was repeated in all subjects after two months. The 24-hour ambulatory blood pressure monitoring was repeated in all subjects during enalapril treatment only, by a non-blind investigator. RESULTS. Ambulatory blood pressure decreased significantly during enalapril and no changes in heart rate were observed during the monitoring. The results of bicycle stress testing, both in basal and during the placebo test were comparable as regards blood pressure response, maximal workload, effort duration, maximal heart rate and VO2 max. With enalapril systolic and diastolic blood pressure decreased significantly during stress testing both versus basal test and placebo test at each workload considered including maximal workload. No changes were observed during enalapril as regards maximal workload, effort duration, maximal heart rate and VO2 max. CONCLUSION. Our results suggest that enalapril could be effective in treating hypertensive athletes because it reduces blood pressure during physical effort without affecting physical performance. We conclude that enalapril could be considered a first-choice drug in hypertensive athletes doing aerobic sports.

[Evaluation of the efficacy and tolerability of sustained-release nifedipine in arterial hypertension. Continuous monitoring of arterial pressure]

The anti-hypertensive efficacy of slow-release nifedipine 20 mg twice a day was investigated in 20 consecutive patients (13 females and 7 males, mean age 50.3 +/- 9.9 years) with mild to moderate hypertension (mean casual BP 162.2 +/- 7.5/103.1 +/- 4.7 mmHg) continuous blood pressure monitoring and routine laboratory tests were performed before and after three months of continuous therapy, whereas casual blood pressure was assessed after one and three months of therapy.

RESULTS

In 4 patients, all female, adverse effects (headache) led to discontinuation of therapy. In the other 16 patients casual blood pressure decreased to 149.8 +/- 12.7/95.3 +/- 6.6 after one month and to 148.7 +/- 11.7/91.4 +/- 7.1 after three months (p less than 0.05 and became normal after three months in 11 patients (68%). Continuous blood pressure monitoring showed a significant fall in systolic and diastolic day time blood pressure (from 132.8 +/- 6.0/87.9 +/- 5.1 - p less than 0.02) and in systolic night time blood pressure (from 117.1 +/- 6.6 to 107.1 +/- 5.1 - p less than 0.02) without changing the shape of the circadian profiles. No significant changes in systolic blood pressure variability were observed. There was no correlation between pretreatment blood pressure levels and the extent of blood pressure fall during therapy. Heart rate, body weight and all biochemical parameters remains unchanged.

CONCLUSION

Our findings confirm the antihypertensive efficacy of slow release nifedipine. This study does not concord with other reports regarding the tolerability of this drug in women. However the small number of patients does not allow any firm conclusions to be drawn.

Enzymatic decyanation of cyanocobalamin in rat tissues

Cyanocobalamin is decyanated in vitro to hydroxocobalamin by rat liver and kidney. This appears to be due to an enzyme system which we have called “cyanocobalamindecyanase”. The enzyme is in the soluble fraction of the cells; it requires reduced cozymases and flavins and has an optimum pH of 7.2 under anaerobic conditions. This is consistent with the fact that conversion of cyanocobalamin to hydroxocobalamin and/or its reduced forms (B12r, B12s) involves a reductive process in the earliest stage of the biosynthesis of coenzyme B12.