Prevention of Short Term Reversible Chronic Atrial Fibrillation by Permanent Pacing at the Triangle of Koch

Objectives: The purpose of this study was to investigate if single lead interatrial septum pacing could be effective in maintaining sinus rhythm in patients in whom restoration of sinus rhythm was only possible for a period of 2–24 hours after one or more previous electrical cardioversions, and in whom a sinus bradycardia was documented before arrhythmia restarted. The two hours limit was chosen because it was considered a sufficient time to implant a dual chamber pacemaker. Background: Alternative atrial pacing techniques have been demonstrated to be successful in preventing recurrences of atrial fibrillation (AF) in patients with sinus bradycardia. Excluding the AF occurring after only a few sinus beats, at 24 hours from electrical cardioversion an early restart of chronic AF has been reported in 12[emsp4 ]% to 17[emsp4 ]% of the patients. Methods: After sinus rhythm was restored by internal electrical cardioversion, 17 patients, 7 ablated at the AV junction, underwent a dual chamber rate response (DDDR) pacemaker implantation with a screw-in atrial lead placed in the interatrial septum. Results: After a follow-up period of 17±5 months (range 12 to 27 months) persistence of sinus rhythm was observed in 11 patients (65[emsp4 ]%). Six patients (35[emsp4 ]%) had recurrences of paroxysmal attacks, while five (30[emsp4 ]%) were totally free of AF. Recurrence of chronic AF was observed in six cases (35[emsp4 ]%) after 2 days–12 months from implantation. No dislodgements of the atrial lead and no complications were observed at implantation and during follow-up. Conclusions: Interatrial septum pacing is a safe and feasible technique with a satisfying success rate (65[emsp4 ]%) in long-term maintaining sinus rhythm in previously unsuccessfully cardioverted patients.     

Catheter ablation of atrial flutter due to amiodarone therapy for paroxysmal atrial fibrillation.

AIMS: Antiarrhythmic drug treatment for atrial fibrillation can cause atrial flutter-like arrhythmias. The aim of this study was to clarify the effect of catheter ablation of the tricuspid annulus-vena cava inferior isthmus on amiodarone-induced atrial flutter and to determine the incidence of atrial fibrillation after catheter ablation of amiodarone-induced atrial flutter in comparison to regular typical flutter. METHODS AND RESULTS: Among 92 consecutive patients with typical atrial flutter who underwent isthmus ablation 28 patients had atrial flutter without a history of previous atrial fibrillation (group I), 10 patients had atrial flutter following the initiation of amiodarone therapy for paroxysmal atrial fibrillation (group II) and 54 patients had atrial flutter and atrial fibrillation (group III). Atrial cycle length during atrial flutter in amiodarone-treated patients (group II) (277+/-24 ms) was significantly longer as compared to the cycle length of atrial flutter in group I (247+/-33 ms) and group III patients (235+/-28 ms). The rate of successful transient entrainment and overdrive stimulation to sinus rhythm was not different between patients with (60%) or without amiodarone therapy (group I: 71%, group III: 53%). Successful isthmus ablation with bidirectional conduction block eliminating right atrial flutter was achieved in 90% of amiodarone-treated patients and 93% of patients without amiodarone therapy. In the amiodarone-treated patient group atrial conduction times during pacing in sinus rhythm were significantly prolonged by 20-30% before and after ablation in all regions of the reentrant circuit. During a mean follow-up of 8+/-3 months post-ablation, atrial fibrillation recurred in two of 10 patients on continued amiodarone therapy after successful isthmus ablation. Thus, successful catheter ablation of atrial flutter due to amiodarone therapy was associated with a markedly lower recurrence rate of paroxysmal atrial fibrillation (20%) as compared to patients with atrial flutter plus preexisting paroxysmal atrial fibrillation (76%) and was similar to the outcome of patients with successful atrial flutter ablation without preexisting atrial fibrillation (25%). CONCLUSION: These data suggest that isthmus ablation with bidirectional block and continuation of amiodarone therapy is an effective therapy for the treatment of atrial flutter due to amiodarone therapy for paroxysmal atrial fibrillation.     

Effects of amiodarone and diltiazem on persistent atrial fibrillation conversion and recurrence rates: a randomized controlled study

Purpose: To assess the effects of amiodarone and diltiazem on atrial fibrillation (AF) induced atrial electrical remodeling and their clinical implications. Methods: Persistent AF patients were randomly assigned to three treatment groups over a period from 6 weeks before to 6 weeks after internal cardioversion: group A (35 patients, oral diltiazem), group B (34 patients, oral amiodarone) and group C (37 patients, no antiarrhythmic drugs). Several electrophysiological parameters were assessed 5 min and 24 h after cardioversion. Results: Compared with controls, group B patients had significantly higher conversion rates (83% vs. 100%, p = 0.041) and a higher probability to maintain sinus rhythm (p = 0.037). Patients of group B had longer fibrillatory cycle length intervals than patients of group A and C (180 ± 18 ms vs. 161 ± 17 ms vs. 164 ± 19 ms, p = 0.001) and longer atrial effective refractory periods (211 ± 22 ms vs. 198 ± 16 ms vs. 194 ± 17 ms, p = 0.003) as assessed 5 min after conversion. Post-conversion density of supraventricular ectopics was significantly lower in group B compared to groups A and C (p = 0.001). Conclusions: Oral amiodarone increases conversion rates, prolongs fibrillatory cycle length and atrial effective refractory period and preserves sinus rhythm after cardioversion in persistent AF patients by suppressing the atrial ectopics that trigger AF.     

Activation Effects of Single-Site and Dual-Site Right Atrial Pacing in Canine

Medical therapy for managing atrial fibrillation remains less than satisfactory. Electrical therapy such as right atrial (RA) pacing was shown to reduce rate of recurrence of atrial fibrillation, while evidently dual-site pacing was more effective than single-site pacing. However, similarities and/or differences in the electrophysiological consequences of single-site and dual-site RA pacing are unclear. Our objective was to simultaneously map RA and left atrial (LA) activation patterns and compare intra-atrial and interatrial activation properties during single-site and dual-site RA pacing in the normal canine heart. Basket-shaped catheters carrying 64 electrodes were deployed under the guidance of fluoroscopy and echocardiography into both the RA and LA of 7 dogs. Basket unipolar electrograms were simultaneously recorded while pacing at high lateral RA (HRA) alone, at inferior RA septum (RAS) alone, and at both sites simultaneously. We found that pacing at HRA alone resulted in the longest interatrial conduction time (47±6[emsp4 ]ms). Pacing at RAS alone significantly shortened interatrial conduction time (29±5[emsp4 ]ms) and completely activated both the RA and LA simultaneously (70±6[emsp4 ]ms and 69±8[emsp4 ]ms, respectively). Dual-site pacing at HRA and RAS significantly abbreviated RA complete activation time (52±7[emsp4 ]ms), but did not alter interatrial conduction time or LA activation pattern compared to pacing at RAS alone. In conclusion, single-site pacing at RAS shortened interatrial conduction time compared to HRA and completely activated both atria simultaneously in canines with normal atria. In addition to shortening interatrial conduction time, dual-site pacing at HRA and RAS abbreviated RA complete activation time.     

Incidence and modes of onset of early reinitiation of atrial fibrillation after successful internal cardioversion, and its prevention by intravenous sotalol

OBJECTIVES—To study the incidence and mode of onset of early reinitiation of atrial fibrillation (ERAF) following successful internal cardioversion of chronic atrial fibrillation, and to determine the effects of sotalol in the prevention of ERAF.
DESIGN—The incidence and modes of onset of ERAF and the acute effects of intravenous sotalol in the prevention of ERAF were studied retrospectively.
SETTING—Electrophysiology laboratory at a university teaching hospital.
PATIENTS—64 patients, mean (SD) age 62 (10) years, who underwent internal cardioversion of chronic atrial fibrillation (mean duration of atrial fibrillation 31 (39) months).
MAIN OUTCOME MEASURES—ECGs and intracardiac electrograms recorded during the internal cardioversion of atrial fibrillation using 3/3 ms biphasic, R wave synchronised shocks.
RESULTS—52 patients (81%) had successful electrical cardioversion, and 20 (31%) of these had ERAF during the procedure. There was no clinical predictor for the occurrence of ERAF. Fifty eight episodes of ERAF were observed. Five ERAF episodes (9%) had preceding bradycardia and 53 (91%) of these were triggered by atrial premature beats with normal preceding heart rate. Atrial premature beats that reinitiated atrial fibrillation had a shorter coupling interval (333 (43) ms v 396 (100), p < 0.001) and a lower prematurity index (0.44 (0.11) v 0.55 (0.14), p < 0.001) than those that did not reinitiate atrial fibrillation. Repeated shock delivery and increasing the defibrillation energy did not prevent ERAF. Intravenous sotalol infusion decreased the numbers of atrial premature beats and prolonged their coupling interval, and prevented ERAF after repeated defibrillation in 83% of patients with ERAF.
CONCLUSIONS—ERAF is a significant clinical problem after successful internal cardioversion of chronic atrial fibrillation, and was observed in up to 31% of patients. In most episodes, ERAF was triggered by short coupling atrial premature beats with preceding normal heart rate. Intravenous sotalol was effective in preventing ERAF in most cases.


Keywords: atrial fibrillation; low energy cardioversion; sotalol     

Effectiveness of Ibutilide in Cardioversion of Persistent Atrial Fibrillation in Patients with Dual Chamber Stimulation

Aim of the study: To evaluate the effectiveness of Ibutilide in cardioversion of persistent atrial fibrillation in patients with sinus node disease wearing a dual chamber pacemaker and to assess the potential role of overdrive ventricular pacing in prevention of drug related proarrhythmia. Methods and Results: Fifty-three sinus node disease patients (35 males; mean age 75 ± 9.5 years), implanted with a dual chamber pacing system, with persistent atrial fibrillation, lasting for 328 ± 416 days, received 1–2 mg of intravenous Ibutilide. Pacing mode was programmed in VVI at 90 ppm, in order to suppress spontaneous ventricular activity. All patients were monitored for 4 hours. Late occurrence of ventricular arrhythmias was evaluated using the pacemaker memory. Ventricular pacing threshold, spontaneous electrogram amplitude and pacing impedance were measured before and after Ibutilide infusion. Cardioversion to sinus rhythm occurred in twenty-two patients (41.5%). Treatment success was significantly related to shorter atrial fibrillation duration. Paced QT interval duration increased from 412 ± 36 ms to 481 ± 40 ms (p < 0.0001), without differences between responders and non responders; QRS width did not change significantly (from 152 ± 25 ms to 161 ± 25 ms; p = n.s.). No early or late episodes of sustained or non sustained polymorphic ventricular tachycardia were observed. Pacing and sensing threshold did not show any significant variation. Conclusions: Ibutilide showed a good effectiveness in treating persistent atrial fibrillation in paced patients. Overdrive ventricular pacing may have played a role in preventing drug induced ventricular proarrhythmia. No adverse effect on pacing threshold was observed.     

Evaluation of Atrial Refractoriness and Atrial Fibrillation Inducibility Immediately after Internal Cardioversion in Patients with Chronic Persistent Atrial Fibrillation

Summary. Objective: To prospectively evaluate right atrial refractoriness and sustained atrial fibrillation (AF) inducibility at programmed electrical stimulation in two groups of patient: a series of patients with chronic persistent AF, studied immediately after successful low energy internal atrial cardioversion, and a group of control patients without history of supraventricular arrhythmias.Patients: Nineteen patients with chronic persistent AF (mean AF duration 11 ± 10 months, range 2–61 months) submitted to successful internal low energy atrial cardioversion in fully conscious state and 11 control patients without history of supraventricular arrhythmias.Methods: An electrophysiological evaluation was performed to measure atrial refractoriness and AF inducibility, by delivering single atrial extrastimuli in high right atrium, at decremental coupling, during spontaneous sinus rhythm and after 8 beats at 600, 500, 400 and 330 ms cycle length. If sustained AF was induced the protocol was terminated.Results: During programmed atrial stimulation sustained AF was induced in 8 out 19 (42%) of the AF patients but in none of the control group. Atrial effective refractory period was significantly shorter in AF patients compared to controls both at basic cycle length, at 600 ms, 500 ms and 400 ms cycle length, meanwhile no statistically significant differences were found at 330 ms cycle length. An altered relationship between atrial effective refractory period and cycle length was found in AF patients compared to controls: the slope of linear correlation slope was significantly lower in AF group than in controls (0.04 ± 0.07 vs 0.17 ± 0.10, p < 0.002).Conclusions: Marked abnormalities of atrial refractoriness and of its heart rate relationship are observed after internal cardioversion of chronic persistent AF in humans and these abnormalities are associated with an high vulnerability to AF. These observations may explain the high risk of AF recurrences in the early phases following successful cardioversion. In this scenario antiarrhythmic drug therapy seems to be mandatory for reducing arrhythmia relapses.     

Atrial pacing for suppression of early reinitiation of atrial fibrillation after successful internal cardioversion.

AIMS: To evaluate the efficacy of atrial pacing in the suppression of early reinitiation of atrial fibrillation after successful internal cardioversion. METHODS AND RESULTS: The efficacy of atrial pacing in suppressing early reinitiation of atrial fibrillation was studied in 12 of 45 (29%) patients with early reinitiation of atrial fibrillation after successful cardioversion. These patients were randomized to undergo either repeated defibrillation alone or repeated defibrillation followed by high right atrial pacing at 500 ms in a crossover fashion. In patients with persistent early reinitiation of atrial fibrillation despite atrial pacing at 500 ms and repeated defibrillation, atrial pacing at 300 ms was tested. Lastly, if early reinitiation of atrial fibrillation persisted, administration of intravenous sotalol (1.5 mg. kg(-1)) was tested. Atrial pacing at 500 ms after defibrillation prevented early reinitiation of atrial fibrillation in five of 12 (42%) patients, and was significantly more effective than repeated defibrillation (0/9 patients, 0%, P<0.05). During atrial pacing at 500 ms, the density of atrial premature depolarizations (APDs) was significantly decreased (2.4+/-2.4 APDs. min(-1)vs 16.4+/-9.8 APDs. min(-1), P<0. 05) and the coupling interval of atrial premature depolarization was significantly increased (420+/-32 ms vs 398+/-19 ms, P<0.05) as compared to no pacing. In the remaining seven (58%) patients, atrial pacing at 500 ms failed to prevent early reinitiation of atrial fibrillation, but significantly decreased the density of atrial premature depolarization (3.4+/-2.4 APDs. min(-1)vs 14.2+/-4.8 APDs. min(-1), P<0.05) and delayed the onset of early reinitiation of atrial fibrillation (33+/-17s vs 11+/-11 s, P<0.05). Atrial pacing at 300 ms decreased the coupling interval of atrial premature depolarization as compared to no pacing and during atrial pacing at 500 ms (P<0.05), but without early reinitiation of atrial fibrillation suppression. Administration of intravenous sotalol was effective in preventing early reinitiation of atrial fibrillation in five of seven (71%) patients where pacing failed to suppress early reinitiation of atrial fibrillation. CONCLUSION: The results of this study suggest that atrial pacing can be useful when combined with transvenous defibrillation in patients with early reinitiation of atrial fibrillation.     

Oral amiodarone increases the efficacy of direct-current cardioversion in restoration of sinus rhythm in patients with chronic atrial fibrillation.

AIMS: Direct current cardioversion of persistent atrial fibrillation is one of the most widely used and effective treatments for the restoration of sinus rhythm, but may be hampered by a low success rate and a high percentage of early recurrence. Pre-treatment with amiodarone or a glucose-insulin-potassium solution could improve the efficacy of electrical cardioversion by reversing the partially depolarized diastolic potential of the subsidiary pacemakers in atrial fibrillation. In a controlled randomized study, we assessed the effectiveness of electrical cardioversion in patients with persistent atrial fibrillation after pre-treatment with amiodarone or potassium infusion and the efficacy of amiodarone in maintaining sinus rhythm after electrical cardioversion. METHODS AND RESULTS: Ninety-two patients with persistent atrial fibrillation (>2 weeks duration) were prospectively randomized into three matched groups: A (n=31, oral amiodarone 400 mg. day(-1)1 month before and 200 mg. day(-1)2 months after cardioversion), B (n=31, 180 mg. day(-1)oral diltiazem 1 month before and 2 months after cardioversion and 80 mmol potassium, 50 UI insulin in 500 ml 30% glucose solution 24 h before cardioversion) and C (n=30, control patients, 180 mg. day(-1)oral diltiazem 1 month before and 2 months after cardioversion). Before cardioversion all patients were under 4 weeks effective oral anticoagulant therapy (warfarin). Before electrical cardioversion, the rate of spontaneous conversion to sinus rhythm was higher in group A (25%) than groups B (6%) or C (3%) (P<0.005). Electrical cardioversion was more successful in group A (88%) than groups B (56%) or C (65%) (P<0.05), while the electrical thresholds for effective cardioversion were lower in group B than the other groups (P<0.05). Twenty-four hours after cardioversion, the early recurrence of atrial fibrillation was similar in the three groups (P=ns), while at 2 months the recurrence rate was lower in group A (32%) than groups B (56%) or C (52%) (P<0.01). CONCLUSION: Pre-treatment with low-dose oral amiodarone, compared with oral diltiazem or glucose-insulin-potassium treatments, induces a significantly high percentage of instances of spontaneous conversion, increases electrical cardioversion efficacy and reduces atrial fibrillation recurrence.     

The Spatial Dispersion of Atrial Refractoriness and Atrial Fibrillation Vulnerability

The local dispersion of conduction and refractoriness has been considered essential for induction of atrial arrhythmias. This study sought to determine whether a difference of refractoriness and vulnerability for induction of atrial fibrillation between trabeculated and smooth as well as high and low right atrium may contribute to initiation of atrial fibrillation in dogs.In 14 healthy mongrel dogs weighing 22.4 ± 1 kg, closed-chest endocardial programmed stimulation was performed from four distinct right atrial sites. Atrial refractory periods and vulnerability for induction of atrial fibrillation or premature atrial complexes were determined during a basic cycle length of 400 and 300 ms and an increasing pacing current strength.For a pacing cycle length of 300ms, atrial refractory periods were longer on the smooth, as compared to the trabeculated right atrium (102 ± 25 vs. 97 ± 17ms, p < 0.05), whereas for a pacing cycle length of 400ms, there was no significant difference. The duration of the vulnerability zone for induction of atrial fibrillation was longer on the smooth right atrium, for a cycle length of both 400 ms (40 ± 30 vs. 31 ± 22 ms; p < 0.05) and 300 ms (33 ± 25 vs. 23 ± 21 ms; p < 0.01). When comparing high and low right atrium, refractory periods were longer on the the low right atrium, for a cycle length of both 400 ms (111 ± 23 vs. 94 ± 24ms; p < 0.01) and 300 ms (104 ± 20 vs. 96 ± 23ms; p < 0.01). For a pacing cycle length of 300 ms, the duration of the atrial fibrillation vulnerability zone was longer for the high, as compared to the low right atrium (34 ± 22 vs. 22 ± 22, p < 0.01). Seven dogs with easily inducible episodes of atrial fibrillation demonstrated significantly shorter refractory periods as compared to 7 non-vulnerable dogs, regardless of pacing site and current strength.In conclusion, significant differences in refractoriness and vulnerability for induction of atrial fibrillation can be observed in the area of the crista terminalis in healthy dogs. Thus, local anatomic factors may play a role in the initiation of atrial fibrillation.     

Amiodarone in restoration and maintenance of sinus rhythm in patients with chronic atrial fibrillation after unsuccessful direct-current cardioversion

Background: When direct-current (DC) cardioversion is used, sinus rhythm can be restored, at least temporarily, in 80–90% of patients with atrial fibrillation. However, there is a small but significant group of patients with chronic atrial fibrillation in whom DC cardioversion has failed to restore sinus rhythm. The value of antiarrhythmic drug pretreatment before DC cardioversion is still controversial. Hypothesis: The aim of our study was to assess (1) the effecti veness of repeat DC cardioversion in patients with chronic atrial fibrillation after pretreatment with amiodarone, and (2) the efficacy of amiodarone in maintaining sinus rhythm after repeat cardioversion. Methods: Forty-nine patients with chronic atrial fibrillation after ineffective DC cardioversion were included in the study. Repeat DC cardioversion was performed after loading with oral amiodarone, 10–15 mg/kg body weight/day for a period necessary to achieve the cumulative dose of over 6.0 g. Results: Spontaneous conversion to sinus rhythm during amiodarone pretreatment was achieved in 9 of 49 patients (18%). Direct-current cardioversion was performed in 39 patients and sinus rhythm was achieved in 23 of these patients (59%). Mean heart rate decreased from 95 beats/min before to 68 beats/min after DC cardioversion (p<0.001). Systolic blood pressure significantly (p<0.05) decreased from 126 ± 23 to 108 ± 25 mmHg. Complications occurring in four patients just after electroconversion were well tolerated and of short duration. After 12 months, 52% of patients maintained sinus rhythm on low dose (200 mg/day) amiodarone therapy. Conclusion: Pretreatment with amiodarone and repeat DC cardioversion allows for restoration of sinus rhythm in about 65% of patients with chronic atrial fibrillation after first ineffective DC cardioversion. Direct-current cardioversion can be performed safely with the use of standard precautions in patients who are receiving amiodarone. At 12 months' follow-up, more than 50% of patients maintain sinus rhythm on low-dose amiodarone after successful repeat cardioversion.     

Endocardial Stimulation of Efferent Parasympathetic Nerves to the Atrioventricular Node in Humans: Optimal Stimulation Sites and the Effects of Digoxin

The purposes of this study were to identify optimal sites of stimulation of efferent parasympathetic nerve fibers to the human atrioventricular node via an endocardial catheter and to investigate the interaction between digoxin and vagal activation at the end organ. Methods: The ventricular rate was measured during atrial fibrillation, prior to and during parasympathetic nerve stimulation, in 8 patients taking digoxin and in 10 controls. High frequency electrical stimuli were delivered via an hexapolar or quadripolar electrode catheter, placed at the posteroseptal right atrium near the atrioventricular node (n=18 patients) or in the coronary sinus (n=12 of 18 patients). In 4 patients, stimulation was repeated after intravenous administration of 1 to 2[emsp4 ]mg of atropine. Results: Nerve stimulation prolonged the R-R interval in all patients. Stimulation close to the posteroseptal right atrium led to maximal atrioventricular nodal slowing. The mean R-R intervals at baseline and during parasympathetic nerve stimulation (60[emsp4 ]mA) from the posteroseptal right atrium and the proximal coronary sinus were 581±79[emsp4 ]ms, 2440±466, and 900±228[emsp4 ]ms respectively (p=0.0001). The response to nerve stimulation was greater in patients taking digoxin than in patients not taking the drug (p=0.02). Junctional rhythm occurred during nerve stimulation in 8/8 patients taking digoxin and 0/10 not taking the drug (p=0.0001). The response to stimulation was eliminated after atropine (p=0.01). Conclusions: Parasympathetic nerves to the atrioventricular node were stimulated from the proximal coronary sinus as well as the posteroseptal right atrium. Stimulation at the posteroseptal right atrium resulted in the greatest response, and digoxin enhanced this response. The augmented response suggests that an interaction may exist between parasympathetic stimulation and digoxin at the end organ.     

Effect of 60 Minutes of Rapid Atrial Pacing on Atrial Action Potential Duration in the In-Situ Canine Heart

Right atrial monophasic action potentials were recorded before and after 60 minutes of rapid atrial pacing (pacing cycle length (CL); 127 ± 10 ms) in 12 closed-chest dogs. The right atrial (RA) monophasic action potential (MAP) duration at 90% repolarization (RAMAPD) was measured at CLs of 400 ms and 250 ms. CL-dependent changes in RAMAPD (CL 400 ms – 250 ms) before and after rapid atrial pacing were 24 ± 1 ms and 16 ± 5 ms, respectively (p < 0.02). RAMAP was recorded at each atrial pacing CL starting at 240 ms decreasing by 10-ms increments. RAMAPD alternans was observed in 10 of 12 dogs at a CL of 163 ± 17 ms before and in 10 of 12 dogs at s CL of 198 ± 29 ms (p < 0.01) after rapid atrial pacing. Sustained atrial fibrillation (AF) (>5 minutes) was induced in 1 of 12 dogs at a pacing CL of 130 ms before rapid atrial pacing and in 4 of 12 dogs at a pacing CL of 135 ± 17 ms after rapid atrial pacing. Onset of AF was always preceded by the RAMAPD alternans. Sixty minutes of rapid atrial pacing leads to diminution of rate adaptation of atrial action potential duration (APD) and appearance of APD alternans of greater magnitude at longer CL, both of which may contribute to the initiation and perpetuation of AF during its early phase.     

心房颤动电复律与胺碘酮节律控制的效果——附53例临床观察

目的：观察电复律＋胺碘酮维持治疗对持续性心房颤动（房颤）节律控制的效果及安全性。方法：回顾分析2007年8月至2010年12月在我院行心脏电复律＋胺碘酮维持治疗的53例持续性房颤患者的资料,对复律≥2年的24例患者进行随访,其中维持窦性心律1.5年者16例（复律组）,房颤复发者8例（复发组）。结果：53例有50例达到复律早期成功,早期成功率为94.3%,与电复律前比较,电复律后患者的总心室率[（109777±6757）次/min比（81083±5036）次/min]、平均心率[（81±8）次/min比（62±6）次/min]、最快心室率[（145±13）次/min比（123±11）次/min]、最慢心室率[（67±7）次/min比（45±6）次/min]明显减低（P〈0.05）;与复律组比较,复发组的房颤持续时间[（4.36±1.47）月比（8.7±2.15）月]、左房内径[（35.85±2.07）mm比（43.15±1.95）mm]、年龄[（54.3±11.7）岁比（72.1±8.3）岁]均明显增大（P〈0.01～〈0.001）。所有病人无明显副作用。结论：电复律联合小剂量胺碘酮维持治疗对大部分持续性房颤患者有效、安全、简便,应该推广。     

Impact of biphasic electrical cardioversion of atrial fibrillation on early recurrent atrial fibrillation and shock efficacy

INTRODUCTION: Early recurrent atrial fibrillation (ERAF) after external cardioversion of atrial fibrillation (AF) occurs in 12% to 26% of patients. Whether biphasic cardioversion has an impact on the incidence of ERAF after cardioversion of AF is unclear. METHODS AND RESULTS: Consecutive patients (n = 216, mean age 66 years, 71% male, 88% with structural cardiovascular disease or hypertension) underwent cardioversion with a biphasic (Bi) or monophasic (Mo) shock waveform in randomized fashion. Energies used were 120-150-200-200 Ws (Bi) or 200-300-360-360 Ws (Mo). The two study groups (Bi vs Mo) did not differ with regard to age, sex, body mass index, underlying cardiovascular disease, left atrial diameter, left ventricular ejection fraction, duration of AF fibrillation, and antiarrhythmic drug therapy. Mean delivered energy was significantly lower in the Bi group (Bi: 186 +/- 143 Ws vs Mo: 324 +/- 227 Ws; P < 0.001). Overall incidence of ERAF (AF relapse within 1 minute after successful cardioversion) was 8.9% and showed no difference between the two groups (Bi: 8.1% vs Mo: 9.7%, P = NS). Cardioversion was successful in 95.4% of patients. The success rate was comparable in both groups (Bi: 94.3% vs Mo 96.8%; P = NS). First shock efficacy did not differ between Bi and Mo (76.4% vs 67.7%; P = NS). Mean number of shocks were 1.4 shocks per patient in both groups. CONCLUSION: Biphasic cardioversion allows comparable success rates with significantly lower energies. However, the incidence of ERAF is not influenced by biphasic cardioversion. With the energies used, biphasic and monophasic shock waveforms are comparable with regard to first shock and cumulative shock efficacy.     

Impact of Consistent Atrial Pacing Algorithm on Premature Atrial Complexe Number and Paroxysmal Atrial Fibrillation Recurrences in Brady-Tachy Syndrome: A Randomized Prospective Cross Over Study

Aim of the study: The Consistent Atrial Pacing (CAP) algorithm has been designed to achieve a high percentage of atrial pacing to suppress paroxysmal atrial fibrillation. The aim of our study was to compare the impact of DDDR+CAP versus DDDR pacing on paroxysmal atrial fibrillation recurrences and triggers in patients with Brady-Tachy Syndrome. Methods: 61 patients, 23 M and 38 F, mean age 75±9 y, affected by Brady-Tachy Syndrome, implanted with a DDDR pacemaker, were randomized to DDDR or DDDR+CAP pacing with cross over of pacing modality after 1 month. Results: 78 % of patients in DDDR pacing and 73 % in DDDR+CAP pacing (p=n.s.) were free from symptomatic paroxysmal atrial fibrillation recurrences. During DDDR+CAP pacing, the atrial pacing percentage increased from 77±29 % to 96±7 % (p<0.0001). Automatic mode switch episodes/day were 0.73±1.09 in DDDR and 0.79±1.14 (p=n.s.) in DDDR+CAP. In patients with less than 50 % of atrial pacing during DDDR, automaticmode switch episodes/day decreased during DDDR+CAP from 1.13±1.59 to 0.23±0.32 (p<0.05) and in patients with less than 90 % from 1.23±1.27 to 0.75±1.10 (p<0.001). The number of premature atrial complexes per day decreased during DDDR+CAP from 2665±4468 to 556±704 (p<0.02). Conclusion: CAP algorithm allowed continuous overdrive atrial pacing without major side effects. Triggers of paroxysmal atrial fibrillation induction, such as premature atrial complexes, were critically decreased. Paroxysmal atrial fibrillation episodes were reduced in patients with atrial pacing percentage lower than 90 % during DDDR pacing.     

Internal Cardioversion of Persistent Atrial Fibrillation Using Rectilinear Biphasic Waveform

Internal electrical cardioversion is currently used in patients with persistent atrial fibrillation resistant to external electrical cardioversion. In external cardioversion, biphasic waveforms have shown a greater efficacy than monomorphic waveforms. The present study aimed to test the safety and efficacy of rectilinear biphasic waveform in converting patients with persistent atrial fibrillation to sinus rhythm using internal electrical cardioversion, and to compare it with that of classical monophasic waveform. Twenty-seven consecutive patients with persistent AF received 31 internal cardioversions, using monophasic waveform in 11 (group I), and rectilinear biphasic waveform in 20 cases (group II). Baseline patients characteristics were similar in both groups. Multipolar catheters were positioned in the distal coronary sinus and in the high right atrium. Synchronised shocks were delivered using an escalating protocol of 2, 5, 10, 15, 20, 30, and 50 Joules. In group I, 1 patient was resistant to maximal energy (success rate 91%). The mean energy of the maximal shock was 18 ± 13 J. In group II, all patients were converted to sinus rhythm. The mean energy of the maximal shock was 9 ± 5 J (p < 0.01 vs. group I). No significant complications occurred. At 3 months follow-up, 45% of group I and 60% of group II patients remained in sinus rhythm (p = NS).We conclude that internal cardioversion using rectilinear biphasic waveform is feasible and safe, and requires less energy than classical monophasic waveforms.     

Akuttherapie lebensbedrohlicher tachykarder Rhythmusstörungen

Life-threatening supraventricular tachyarrhythmias include atrial fibrillation, atrial flutter, AV-nodal reentrant tachycardia with rapid ventricular response and preexcitation syndromes combined with atrial fibrillation. Ventricular tachyarrhythmias still remain one of the leading causes of death; these arrhythmias include monomorphic and polymorphic ventricular tachycardia, torsade de pointes tachycardia, ventricular fibrillation and ventricular flutter. In all patients with tachycardias, an attempt should be made to differentiate between narrow (QRS duration < 0.12 s) or wide QRS complex (QRS duration ≥ 0.12 s) tachycardias. In the assessment of patients (pts) with supraventricular/ventricular tachyarrhythmias, attention should be given to identify whether the tachycardia is associated with worsening angina or low cardiac output. In pts with narrow QRS complex tachycardias or pts with atrial fibrillation and preexcitation syndromes immediate synchronized cardioversion should be performed if signs or symptoms of instability (hypotension, evidence of end-organ dysfunction, worsening angina) exist. In pts with a stable hemodynamic situation, vagal maneuvers, adenosine or calcium channel blockers can be used. Management of atrial flutter usually centers on cardioversion or rapid atrial pacing to normal sinus rhythm. In the treatment of patients with deemed unstable ventricular tachycardia (VT), electrical cardioversion is the treatment of choice. In more stable patients, ajmaline is the preferred agent after myocardial infarction and lidocaine if myocardial ischemia is present. In pts with torsade de pointes tachycardias aggressive steps must be taken to prevent degeneration of this rhythm to ventricular fibrillation (VF). Magnesium sulfate has recently been demonstrated efficacious and is currently considered first-line drug therapy. Transcutaneous overdrive pacing should be attempted if magnesium is unsuccessful. The pt with pulseless VT or VF demands early electrical countershock.     

Apparent Bidirectional Conduction Block Following Radiofrequency Catheter Ablation of Typical Atrial Flutter

Objective: The purpose of this study is to determine the reliability of activation sequence mapping in assessing the presence of bidirectional conduction block (BCB) in typical atrial flutter (AFL) ablation. Introduction: Radiofrequency ablation (RFA) can cure typical AFL by creating BCB across the right atrial isthmus. Effective conduction block across this region can prevent AFL recurrence, but accurate assessment of isthmus conduction may be flawed. Methods: BCB was measured before and after RFA by pacing at multiple rates on both sides of the isthmus during sinus rhythm. Pacing was performed from a low lateral tricuspid annulus site (proximal to the isthmus) and a coronary sinus Os site (distal to the isthmus), while recording simultaneously from 8–10 right atrial sites bordering the isthmus (4–5 free wall sites; 4–5 septal sites) as well as from an isthmus site. After ablation reinduction of atrial flutter was attempted from both sides of the block with rapid atrial pacing after BCB was established in all patients. In some patients lines of conduction block were evident at the isthmus (using the ablation catheter to map). Results: Of 65 patients undergoing RFA of AFL, 59 had typical AFL. In all 59 patients, BCB was demonstrated at all pacing cycle lengths 30[emsp4 ]min after RFA applications. In 6 of these 59, AFL was inducible with atrial pacing despite apparent BCB. Further RFA resulted in non inducibility in all 6 patients. In the remaining 53/59 patients, BCB was associated with noninducibility at 30[emsp4 ]min. A total of 8 recurrences were seen during a mean 19.3[emsp4 ]±[emsp4 ]8.3 (SD) month follow-up. Conclusion: Apparent BCB as determined by activation sequence mapping outside of the isthmus is an excellent marker, but, as measured, may be a misleading method of assessing the presence or absence of conduction through the isthmus. It is necessary to attempt reinduction of AFL after apparent success. Elimination of typical AFL does not preclude other AFLs.     

Recovery of electrophysiological parameters after conversion of atrial fibrillation.

We investigated the recovery of electrophysiological parameters from electrical remodeling after conversion of chronic lone atrial fibrillation in humans. Clinical studies have shown that the longer atrial fibrillation lasts, the more difficult it becomes to maintain the sinus rhythm after cardioversion. To explore the effects of the duration of atrial fibrillation on changes of electrophysiological parameters after conversion, we determined the atrial effective refractory period and P wave duration during right atrial pacing at 1 and 24 h after electrical cardioversion in 15 patients with chronic lone atrial fibrillation (median duration, 6 months). By 24 h after cardioversion, the effective refractory period at a pacing cycle length of 600 ms increased from 225+/-19 to 254+/-27 ms. However, the P wave duration did not decrease significantly 24 h after conversion. As the duration of atrial fibrillation became longer, the prolongation of effective refractory period was more delayed (P<0. 001, r=0.82), and the shortening of P wave duration was significantly smaller within 24 h after cardioversion (P<0. 001, r=0.67). After cardioversion of chronic lone atrial fibrillation, the recovery of shortened atrial refractoriness and prolonged intraatrial conduction time is dependent on the duration of preexisting atrial fibrillation.