Preserved left ventricular ejection fraction following atrioventricular junction ablation and pacing for atrial fibrillation

Introduction: Right ventricular apical (RVA) pacing creates ventricular dyssynchrony and may compromise left ventricular ejection fraction (LVEF). The impact of RVA pacing in patients who have undergone atrioventricular junction (AVJ) ablation for atrial fibrillation (AF) is unclear. We sought to determine whether RVA pacing after AVJ ablation for patients with AF compromises LVEF in the short- or long-term.
Methods/Results: We studied 286 patients with AF who underwent AVJ ablation and RVA pacing at our institution between 1990 and 2002. Patients were stratified into a short-term follow-up group (LVEF reassessed by echocardiography within a year after AVJ ablation, n = 134) and a long-term group (LVEF reassessed after a year, n = 152). Among all 286 patients (mean follow-up 20 months), we observed no change in mean LVEF after AVJ ablation and RVA pacing (48% before vs. 48% after, P = 0.42). Short-term follow-up patients had a statistically significant improvement in mean LVEF (46% before vs. 49% after, P = 0.03), whereas there was no statistically significant change in mean LVEF in long-term follow-up patients (49% before vs. 48% after, P = 0.37). Only 9% of short-term patients, 15% of long-term patients, and 1% of patients with baseline LVEF ≤ 40% experienced ≥10% absolute decrease in LVEF. Baseline LVEF > 40% was a multivariate predictor of LVEF decline.
Conclusions: RVA pacing after AVJ ablation does not compromise LVEF in the short- or long-term for the vast majority of patients. Better predictors are needed to help us select patients for biventricular pacing after AVJ ablation.     

Electrocardiographic determinants of efficacy of 8-Joule shocks for ablation of the atrioventricular node

Factors determining the success of a single, low-energy, direct current-shock to achieve chronic complete heart block were studied in a consecutive group of 14 patients. A shock of 8 J was delivered by a modified device (Sirecust BS1, Siemens). If the first shock did not produce persistent complete block, multiple shocks were given. Standard 6 French U.S.C.I. catheters were used for all procedures. Chronic complete heart block was achieved with a single shock in six cases (43%; Group I); in eight others multiple shocks were needed (Group II). Neither polarity of the bipolar and of the distal His bundle recording nor the presence of sinus rhythm before the first shock were important factors to predict the outcome. The amplitude of the first recording of the bipolar His electrogram was 225 +/- 55 microV in Group I and 138 +/- 105 microV in Group II (P = 0.029). The duration of the HV interval before the first shock was 55 +/- 12 ms in Group I and 45 +/- 11 ms in Group II (NS). It is concluded that complete permanent heart block can be achieved with a single 8-J shock in 43% of the patients. The long-term success (follow-up at least 1 month, with a range of 1 to 8) of a single 8-J shock is predicted by a large amplitude of the bipolar and distal unipolar His bundle deflection, but not by its polarity or the HV interval.     

Late ventricular arrhythmia and sudden death following direct-current catheter ablation of the atrioventricular junction.

Early reports of direct-current catheter ablation (DCCA) of the atrioventricular (AV) junction for resistant AV tachycardias documented efficacy of DCCA with little morbidity. Nine patients underwent DCCA at our institution 4 to 9 years ago: 3 patients had DCCA in the coronary sinus for permanent junctional reciprocating tachycardia, 2 patients had His ablation, 2 had coronary sinus and His ablation for permanent junctional reciprocating tachycardia, and 2 had DCCA for congenital tachycardia, and 2 had DCCA for congenital junctional ectopic tachycardia. Shocks (total 1 to 5) ranged from 12.5 to 400 J. Five patients had pacemaker implant at the time of DCCA. During follow-up, 3 patients developed clinical ventricular tachycardia: all 3 had DCCA of the His bundle. One asymptomatic patient with ventricular tachycardia, who had DCCA of the bundle of His, died suddenly 6 years later with ventricular fibrillation. Autopsy revealed 2 ventricular scars: 1 extending from the AV junction and 1 in the outflow tract. No patient with DCCA limited to the coronary sinus developed ventricular tachycardia. DCCA of the His bundle can result in late ventricular arrhythmias, possibly a result of extension of the DCCA lesion into the ventricle. These late findings should be considered in evaluating the safety and efficacy and follow-up for patients undergoing radiofrequency ablation.     

Tako-tsubo cardiomyopathy following transcatheter radiofrequency ablation of the atrioventricular node.

A 66-year-old woman with atrial fibrillation and hypertension developed tako-tsubo cardiomyopathy following acutely uneventful radiofrequency catheter ablation of the atrioventricular (AV) node. We speculate that the increase in sympathetic activity that accompanies AV node ablation contributed to the pathophysiological process, which involves increased catecholamines and/or apical adrenoreceptor density and responsiveness.     

Catheter ablation of the atrioventricular node using radiofrequency energy

Background: Catheter ablation of the atrioventricular (AV) junction using stored direct current (DC) energy from a standard DC Cardioverter defibrillator was first reported in 1982. Since then many patients have been treated using this procedure for refractory supraventricular arrhythmias, usually atrial fibrillation and flutter. Undesirable thermal effects such as barotrauma and arcing are largely responsible for complications associated with the use of DC energy. This report details our experience of catheter ablation of the AV junction using radiofrequency (RF) energy in a series of 30 consecutive patients. Methods: RF ablations were performed using steerable Mansfield (Webster Laboratories) 4 mm tipped electrodes and locally assembled RF energy delivery system. Results: The procedure was successful in 27/30 (90%) patients using RF energy, while three patients required DC energy to achieve successful AV junction ablation. General anaesthesia was required in nine patients, six of whom required this for cardioversion to sinus rhythm so that an adequate His Bundle spike could be recorded and three for DC ablation. Dual chamber permanent pacemakers with automatic mode switching were implanted in four patients who had paroxysmal atrial fibrillation or flutter and the remainder had ventricular rate responsive pacemakers. Conclusions: In patients with drug refractory paroxysmal atrial fibrillation and flutter and in patients with established atrial fibrillation where control of the ventricular rate is difficult, catheter ablation of the AV junction using RF energy is a safe and effective procedure with a high success rate.     

Identification and characterization of atrioventricular parasympathetic innervation in humans

INTRODUCTION: We hypothesized that in humans there is an epicardial fat pad from which parasympathetic ganglia supply the AV node. We also hypothesized that the parasympathetic nerves innervating the AV node also innervate the right atrium, and the greatest density of innervation is near the AV nodal fat pad. METHODS AND RESULTS: An epicardial fat pad near the junction of the left atrium and right inferior pulmonary vein was identified during cardiac surgery in seven patients. A ring electrode was used to stimulate this fat pad intraoperatively during sinus rhythm to produce transient complete heart block. Subsequently, temporary epicardial wire electrodes were sutured in pairs on this epicardial fat pad, the high right atrium, and the right ventricle by direct visualization during coronary artery bypass surgery in seven patients. Experiments were performed in the electrophysiology laboratory 1 to 5 days after surgery. Programmed atrial stimulation was performed via an endocardial electrode catheter advanced to the right atrium. The catheter tip electrode was moved in 1-cm concentric zones around the epicardial wires by fluoroscopic guidance. Atrial refractoriness at each catheter site was determined in the presence and absence of parasympathetic nerve stimulation (via the epicardial wires). In all seven patients, an AV nodal fat pad was identified. Fat pad stimulation during and after surgery caused complete heart block but no change in sinus rate. Fat pad stimulation decreased the right atrial effective refractory period at 1 cm (280 +/- 42 msec to 242 +/- 39 msec) and 2 cm (235 +/- 21 msec to 201 +/- 11 msec) from the fat pad (P = 0.04, compared with baseline). No significant change in atrial refractoriness occurred at distances >2 cm. The response to stimulation decreased as the distance from the fat pad increased. CONCLUSION: For the first time in humans, an epicardial fat pad was identified from which parasympathetic nerve fibers selectively innervate the AV node but not the sinoatrial node. Nerves in this fat pad also innervate the surrounding right atrium.     

射频消融房室结慢径对老年人房室结电生理功能的影响

目的　分析和比较应用射频消融房室结慢径治疗房室结折返性心动过速对老年人和青年人房室结电生理功能的影响。方法　 76例仅患有慢 快型房室结折返性心动过速的患者分为两组 ,老年组 (≥ 6 0岁 ) 36例和青年组(14～ 4 5岁 ) 4 0例 ,均为行慢径消融术成功病例 ,对比消融前后和两组间的房室结功能参数 ,分析和比较这两组患者在射频消融前后房室结电生理特点的异同。结果　所有病例均消融成功。两组病例消融后较消融前房室结前传文氏周期及最长A2 H2 间期均缩短 ,而老年组的心动过速周长、消融前后窦性心率周长及消融后房室结前传文氏周期均较青年组延长。结论　老年人的房室结前传电生理特性较青年人为差 ,而对房室结折返性心动过速患者的慢径有效消融后 ,房室结电生理特性的变化规律不受年龄因素影响     

Ventricular fibrillation occurring after atrioventricular node ablation despite minimal difference between pre- and post-ablation heart rates

We report the case of an 82-year-old man presenting with ventricular fibrillation (VF) occurring acutely after atrioventricular node (AVN) ablation. This patient had severe valvular cardiomyopathy, chronic atrial fibrillation (AF), and underwent prior to the AVN ablation a biventricular implantable cardiac defibrillator positioning. The VF was successfully cardioverted with one external electrical shock. What makes this presentation original is that the pre-ablation spontaneous heart rate in AF was slow (84 bpm), and that VF occurred after ablation despite a minimal heart rate drop of only 14 bpm. VF is the most feared complication of AVN ablation, but it had previously only been described in case of acute heart rate drop after ablation of at least 30 bpm (and more frequently > 50 bpm). This case report highlights the fact that VF may occur after AVN ablation regardless of the heart rate drop, rendering temporary fast ventricular pacing mandatory whatever the pre-ablation heart rate.     

自主神经节丛消融对窦房结及房室结功能的急性期影响

目的探讨神经节丛(GP)消融对窦房结(SAN)及房室结(AVN)功能的影响。方法 7条犬开胸并在左、右心房及肺静脉缝置多极电极导管以备记录及刺激,对左侧及右侧GP分别进行消融,消融前后分别测定静息心率、SAN及AVN功能,SAN功能包括测定6个不同水平起搏周长(380,350,330,300,280及250 ms)时SAN恢复时间(SNRT)以及校正的SNRT(cSNRT);AVN功能包括AH间期(H is束电图记录的房室结传导时间)、递增起搏时出现文氏房室传导阻滞时起搏周长、出现2∶1房室传导阻滞时起搏周长、右房短阵超速起搏诱发心房颤动(简称房颤)时的平均心室率。结果 GP消融后窦性心率无显著改变,长起搏周长时SNRT及cSNRT无显著变化,而短起搏周长时则显著减少(P0.05)。各起搏周长下AH间期、出现文氏房室传导阻滞及2∶1房室传导阻滞时的起搏周长、房颤时平均心室率在GP消融前后均无显著变化。结论 GP消融在较短起搏周长情况下增强了SAN功能,但对AVN功能无明显影响,可能与GP消融时同时破坏了副交感及交感神经成分有关。     

Postcardiac injury syndrome complicating radiofrequency ablation of the atrioventricular node

Radiofrequency ablation, which is increasingly used in the treatment of cardiac arrhythmia, can be complicated with pericardial effusion and one case of Dressler's syndrome has already been reported after an atrioventricular pathway ablation. This case reports a second case complicating an atrioventricular node radiofrequency ablation procedure.     

Comparison of Left Ventricular Ejection Fraction Calculation Methods

Left ventricular ejection fraction (LVEF) has been used for many years to assess left ventricular systolic function. Over time, patients may have LVEF measurements performed with the use of different imaging modalities. It is important for the clinician to appreciate how these different methods compare with each other. The purpose of this study was to determine the correlation among three such LVEF measurement methods: two echocardiographic methods (Teichholz and Quinones) and gated thallium three-dimensional (3-D) scintigraphic method. Eighteen patients underwent both echocardiographic and nuclear imaging studies. The nuclear and echo images were completed within 1 hour of each other. The Teichholz method resulted in consistently larger LVEF estimates but correlated well with the Quinones method (r = 0.88, SEE = 8.41). The Teichholz method did not correlate well with the gated thallium 3-D method and again gave consistently larger estimates that were even higher than when compared with the Quinones method (r = 0.7, SEE = 12.6). The Quinones method and gated thallium 3-D method correlated well (r = 0.87, SEE = 9.6) and gave a line of best fit close to the line of identity. In conclusion, the Teichholz method consistently overestimates LVEF compared with the Quinones and gated thallium 3-D methods. The Quinones echocardiographic and gated thallium 3-D methods appear to result in similar absolute LVEF measurements.     

Ventricular performance and prognosis after primary ventricular fibrillation complicating acute myocardial infarction

To examine the relationship between early arrhythmias, infarctsize and prognosis, we compared 22 consecutive patients survivingacute myocardial infarction (AMI) and primary ventricular fibrillation(VF) with a control population after AMI uncomplicated by primaryVF. Left ventricular ejection fraction (EF) was measured byradionuclide ventriculography before discharge from hospital.Mean EF was significantly reduced below normal following AMIwith or without primary VF (normal 0.57±0.05, mean±SD;P<0.01). Mean EF was lower among patients who survived primaryVF than among those with infarction uncomplicated by primaryarrhythmia (0.33 ±0.12 v. 0.46 ±0.07; P<0.01).There were striking differences in EF between those patientswith anterior and those with inferior infarction. Mean EF forthose surviving primary VF after transmural anterior infarction(0.23±0.06) was lower than those who had primary VF aftertransmural inferior infarction (0.43±0.06; P<0.01J.Normal left ventricular function was seen in four individualswho developed no further complications. Recurrent primary ventriculararrhythmia was seen v only in those individuals subsequentlyshown to have reduced EF. Low EF (< 0-35) was seen in 12patients with primary VF in the context of anterior infarction,five developed breakthrough ventricular arrhythmias despitetherapy and in a limited follow-up period, three have died.     

Randomized controlled trial of fixed rate versus rate responsive pacing after radiofrequency atrioventricular junction ablation: quality of life, ventricular refractoriness, and paced QT dispersion

INTRODUCTION: Ablation of the AV junction is a widely accepted treatment of drug-refractory atrial fibrillation. Long-term pacing of the right ventricular (RV) apex following AV junction ablation can result in adverse cardiac remodeling. However, anecdotal studies report that pacing too slowly following AV junction ablation was associated with propensity to sudden cardiac death. The aim of this study was to provide information about the balance between measures of quality of life versus measures of electrical remodeling achieved by pacing with different rate modalities in a randomized pilot clinical trial. METHODS AND RESULTS: Patients with permanent atrial fibrillation were randomized to VVI (80 beats/min) versus VVIR (minimum rate 80 beats/min), whereas patients with paroxysmal atrial fibrillation were randomized to DDI versus DDDR pacing at discharge from hospital. Serially, measurements of exercise capacity, quality of life, cycle length dependence of QT dispersion (QTdisp), RV refractoriness, and the incidence of nonsustained ventricular tachycardia were made in 28 patients over a 6-month follow-up period. Time-dependent increases in QTdisp were observed in patients randomized to the rate responsive mode (RR-ON) but only when paced at 40 beats/min. This was paralleled by time-dependent increases in RV refractoriness (270 +/- 11 ms at baseline to 302 +/- 5 ms at 6 months) in patients with RR-ON. RR-ON also was associated with trends to an increasing incidence of episodes of nonsustained ventricular tachycardia and worsening of some measures of quality of life. Exercise capacity was not substantially different in the randomized groups. CONCLUSION: Rate responsive pacing results in electrical remodeling of the ventricle following AV junction ablation, but exercise capacity was similar in groups with RR-ON or RR-OFF.     

Ventricular Tachycardia in Patients with Impaired Left Ventricular Function: The Role of Propafenone

The combined occurrence of left ventricular dysfunction and -ventricular tachyarrhythmias portends a high annual mortality. Anti arrhythmic drugs can ameliorate ventricular arrhythmia and may reduce the risk of sudden cardiac death. We administered propafenone to 15 patients with ventricular tachyarrhythmias and left ventricular ejection fractions 40%. Propafenone significantly reduced isolated ventricular premature depolarizations, couplets, and ventricular tachycardia on ambulatory monitoring. Propafenone eliminated all exercise provocable ventricular tachycardia. Propafenone additionally abolished ventricular tachycardia inducible by programmed stimulation in 4 of 7 patients. In 8 patients studied before and during therapy, there was no significant change in left ventricular ejection fraction as determined by nuclear ventriculography. Propafenone was discontinued in 4 patients due to side effects. Seven patients receiving continuing propafenone therapy remain alive with only one patient suffering arrhythmia recurrence. Propafenone is an effective drug for the management of ventricular tachyarrhythmias and may be used for patients with impaired left ventricular function.     

Effects of atrioventricular block on ventricular fibrillation threshold in dog.

The effects of complete atrioventricular block (CAVB) on ventricular vulnerability were studied 1 week after a transcatheter electrical ablation of the AV junction in 18 closed-chest dogs. All dogs exhibited CAVB and a stable ventricular escape rhythm with a mean cycle length of 1795 +/- 600 ms. Although QT interval during CAVB was significantly prolonged compared with that during the sinus rhythm, QTc interval was significantly shortened. The ventricular fibrillation threshold was significantly elevated after creation of the block (from 9.35 +/- 2.28 to 12.3 +/- 3.69 mA, p less than 0.01). Thus, CAVB which is not associated with QTc prolongation would be even less likely to play an important role in producing ventricular fibrillation presumably including torsades de pointes or polymorphous ventricular tachycardia.     

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.


Keywords: atrial fibrillation; embolism; atrioventricular node ablation; pacemaker implantation     

Left Ventricular Systolic Function in a Population Sample of Elderly Men

BACKGROUND: The present study was designed to evaluate the usefulness and discriminatory power of different echocardiographic indices of left ventricular (LV) systolic function in a healthy screening sample of 584 men who were 70 years old. METHODS: Ejection fraction (EF), fractional shortening (FS), stroke index (SI), left ventricular diameter in systole (LVESD), and cardiac index (CI) were evaluated, in addition to LV wall motion score and atrioventricular plane displacement (AVPD). RESULTS: Subjects with hypertension or coronary heart disease (CHD), but not those with diabetes mellitus, showed impairments in EF, FS, LVESD, AVPD, and LV wall motion scores compared with the healthy subjects in the sample (P < 0.01-0.001). SI and CI findings in those with hypertension or CHD were, however, no different from those in the healthy group. The index of LV systolic function that discriminated best between diseased and healthy subjects was LV wall motion score, being correlated with EF, LVESD, and AVPD but only poorly with SI and CI. SI evaluated with use of the Teichholz formula was correlated to LV end-diastolic diameter (r = 0.72, P < 0.0001), whereas the corresponding correlation between SI measured with Doppler (aortic flow) and LVEDD was weak. The difference between the Teichholz and Doppler evaluations of SI was dependent on LV end-diastolic diameter (r = 0.51, P < 0.001) but not on LV systolic function. An index, the systolic two-dimensional index, which takes into account both the longitudinal motion (AVPD) and movement along the short axis (LVESD) during systole, was suggested by the formula AVPD + 5/LVESD. CONCLUSIONS: Impaired LV systolic function was found in both elderly men with hypertension and those with CHD. SI was normal in these groups, however, although overestimated when measured with the Teichholz formula in this population with a large proportion of subjects with LV dilatation. AVPD appears to be applicable in the present population, and a new systolic index consisting of LVESD and AVPD is suggested for the evaluation of LV systolic function in two dimensions.     

房室结消融加永久起搏器植入治疗难治性房扑房颤

目的评价房室结消融加永久起搏器植入治疗难治性房扑房颤的安全性和有效性。方法在临时起搏器保护下，对一例阵发性房扑房颤患者实施射频消融房室结并植入永久起搏器；观察其术中、术后及随访情况。结果该患者手术成功，未发生与射频相关性猝死；术后生活质量改善。结论房室结消融加永久起搏器植入可作为多种治疗无效的房扑房颤患者控制心室率的适当方法，该方法简单有效。     

急性左室心肌梗塞患者右室射血分数的影响因素

分析了５１例急性左室心肌梗塞患者，右室射血分数的影响因素。结果表明，右室射血分数主要受左心功能指标，尤其是左室射血分数的影响，梗塞面积及梗塞部位对右室射血分数的影响不大。