Contemporary Surgical Treatment for Atrial Fibrillation

Traditional surgical treatment of AF is the Cox-Maze III procedure. The Cox-Maze III procedure cures AF in >90% of patients and virtually eliminates the risk of stroke. Recent understanding of the importance of the pulmonary veins and left atrium in the pathogenesis of AF has resulted in the development of new surgical approaches. New operations to ablate AF use alternate energy sources (radiofrequency, microwave, cryothermy) and simplified left atrial lesion sets. These operations cure AF in 70–80% of patients. This article describes contemporary and emerging surgical approaches to AF, synthesizes results of these operations, and proposes a strategy for choice of operation based on patient presentation. (PACE 2003; 26[Pt. II]:1641–1644)     

Maze 3 for Atrial Fibrillation: Two Cuts Too Few?

The Maze procedure has been developed as a surgical approach to the management of patients with atrial fibrillation refractory to medical treatment. The recent modification of the technique (Maze 3) achieves good rate control with coordinated AV contractions. However, the procedure involves cuts that completely isolate a block of left atrial (LA) wall, including the four ostia of the pulmonary veins. The electrical and mechanical activity of this isolated LA block are dissociated from the rest of the atrium, and the area may, in fact, continue to fibrillate. This may provide a nidus for the development of mural thrombus. The weight and endocardial surface area of the LA block and of the entire LA were estimated in ten formalin fixed hearts from trauma victims with no evidence of cardiac disease. In these samples, the LA block represented 35% of the endocardial surface area of the entire LA and 29% of the weight. The LA block is of sufficient size to allow macroreentrant circuits to form and has the potential to fibrillate if isolated from the rest of the atrium. We modified the Maze 3 procedure to recruit the otherwise isolated LA block by using two additional cuts around each pair of pulmonary veins as they enter the LA. The first patient who underwent the modified procedure demonstrated sinus rhythm on Holter monitoring postoperatively and remained in sinus rhythm following burst atrial pacing at 300 and 420 beats/min each for 30 seconds. In addition, atrial contractions were found to contribute 19% of the cardiac output. The majority of the atrial wall and, in particular, the recruited area between the pulmonary veins contracted well, as demonstrated by transesophageal echocardiography. We suggest that this modification of Maze 3 has a potential advantage over the standard procedure by recruiting the entire LA without leaving any dyskinetic endocardial surface for thrombus formation. This should in turn reduce the risk of thromboembolic complications.     

Prophylactic Amidarone Treatment for Atrial Fibrillation After Coronary Artery Bypass Surgery

In this study we performed a retrospective chart review to evaluate the efficacy of short-term postoperative oral amiodarone therapy on postoperative atrial fibrillation (POAF) after coronary artery bypass surgery. The incidence of POAF in 372 patients (60.6%) without prophylactic amiodarone therapy was compared with that in 240 patients (39.4%) receiving the medication immediately after the surgery. Patients who received prophylactic amiodarone developed significantly less POAF than those without prophylactic treatment (17.0% versus 25.9%, P = .01), with relative and absolute risk reductions of 0.7% and 8.9%, respectively. Postoperative oral amiodarone therapy is simple to administer and may be a valuable adjunct therapy for patients after coronary artery bypass surgery.     

Persistent Atrial Fibrillation is Associated with Inability to Recover Atrial Contractility after MAZE IV Surgery in Rheumatic Disease

Background: MAZE IV surgery is effective in restoring sinus rhythm (SR) and atrial contraction (AC) in patients with nonrheumatic persistent atrial fibrillation (AF). However, there is less information on its effectiveness to restore AC in patients with rheumatic disease. Aims: To assess the effectiveness of the MAZE IV surgery in restoring AC in patients with rheumatic disease and long persistent AF. Methods: Prospective, consecutive study in patients who underwent cardiovascular surgery and had long persistent AF in whom MAZE IV surgery was performed. The presence of AC was assessed by lateral mitral annulus tissue Doppler. Results: A total of 75 patients were included. Mean age 60 years (±11.7); 27 men (36%). AF duration was 63 months (±34.1). Primary indication for surgery: rheumatic mitral stenosis 67 patients and mitral insufficiency eight patients. Mean left ventricular ejection fraction (LVEF) was 51.8% (±12.1) and mean left atrial area was 37 cm(2) (±10.3). After a mean follow-up of 28 months (±9.3), 69 patients remained alive and 59 were in SR. AC was detected in 37.3% (Group A) and absent in 62.7% (Group B). The mean difference between groups was the high prevalence of AF longer than 5 years in group B (P = 0.000001). There were no differences related to left atrial size, LVEF, and age. Conclusions: In patients with rheumatic disease, the absence of correlation between SR recovery and AC recovery post MAZE IV surgery is significant. A history of long persistent AF lasting more than 5 years was a strong predictor for the absence of AC. (PACE 2012; 35:999-1004).     

Epicardial, Biatrial Synchronous Pacing for Prevention of Atrial Fibrillation after Cardiac Surgery

About 30% of patients develop AF after open heart surgery. Biatrial synchronous pacing (BSP) has been shown to promote sinus rhythm in patients with paroxysmal AF refractory to drug therapy. We conducted a prospective, randomized study to test the effect of BSP via epicardial electrodes on the incidence of AF after heart surgery, as compared to conventional therapy. To apply BSP, we attached two epicardial electrodes to the right and one to the left atrium. Immediately following surgery, BSP was initiated in the AAI-Mode at a rate of 10 beats/min above the underlying rhythm (maximum 110 beats/min) and continued for 3 days, during which the rhythm was continually monitored. After 21 (age 63 +/- 9 years) of the planned 200 patients, the study was prematurely aborted because of the proarrhythmic effect of BSP: 6 of the 12 patients treated with BSP developed sensing failure (P amplitude < 1 mV), which provoked AF in 5 of these 6 patients. BSP was discontinued due to diaphragmal stimulation in two patients and due to ventricular stimulation by a dislocated left atrial electrode in one patient. Two patients in the control group (n = 9) developed AF. Using the available standard technology, BSP via epicardial electrodes is not suitable to suppress AF after heart surgery, primarily due to postoperative deterioration of atrial sensing and its profibrillatory effect. In patients requiring atrial pacing after heart surgery, sensing thresholds must be closely monitored to prevent induction of AF.     

Efficacy of Type 1C Antiarrhythmic Agents for Treatment of Resistant Atrial Fibrillation

In order to determine the efficacy of type lC agents (flecainide, encainide, propafenone) in patients with atrial fibrillation who have failed to maintain sinus rhythm with type 1A agents (quinidine, procainamide, disopyramide), 147 patients, that were admitted into the John Dempsey Hospital with new or recurrent atrial fibrillation between 1987–1991, were studied retrospectively. Out of the total, 29 patients converted spontaneously to sinus rhythm, 14 patients were left in atrial fibrillation, and 104 patients were given a type 1A antiarrhythmic. Sixty-five of these patients remained in sinus rhythm (54% converted on drug alone, 46% required electrical cardioversion) for at least 6 months. Of the remaining 39 patients, 28 were given a type 1C antiarrhythmic; 13 were successfully converted (61% chemical, 39% electrical) to and remained in sinus rhythm for at least 6 months; the remaining 15 either failed to convert or reverted to atrial fibrillation. New onset atrial fibrillation had a significantly lower incidence of congestive heart failure (10%) than recurrent atrial fibrillation (33%; P < 0.01). No differences in digoxin, beta blocker use, or other clinical characteristics were seen either between type 1A or type 1C successes or failures. Similarly, echocardiographic dimensions did not predict success or failure with either class of agent. In conclusion, type lC antiarrhythmics for suppression of recurrent atrial fibrillation represent a reasonable therapeutic alternative for suppression of atrial fibrillation in patients who have failed type lA agents. Prognostic factors predicting success or failure remain undetermined.     

Pathophysiology of the Pulmonary Vein as an Atrial Fibrillation Initiator:

The basic electrophysiologic studies have proved the arrhythmogenic mechanisms of the pulmonary vein as an atrial fibrillation initiator; the mechanisms include enhanced automaticity, triggered activity, and microreentry from myocardial sleeves inside pulmonary veins. Immunohistology study has proved the conduction characteristics of pulmonary vein myocardium, and further study of ionic currents are important for understanding atrial fibrillation initiation from the pulmonary vein. (PACE 2003; 26[Pt. II]:1576–1582)     

Specificity of Atrial Mode Switching in Detecting Atrial Fibrillation Episodes:

The number of automatic mode switch (AMS) has been used to measure the efficacy of atrial pacing in limiting atrial fibrillation (AF). We investigated the impact of length and contiguity on the specificity of AMS in detecting AF episodes in 24 recipients of dual chamber pacemakers with sick sinus syndrome and paroxysmal AF. An AMS algorithm and intracardiac electrogram recordings (IEGM) were activated in all patients to distinguish true arrhythmic events from unnecessary AMS. The length of AMS and the contiguity, that is, the probability of occurrence of another AMS within 5 minutes before or after AMS were examined to increase the specificity of the AMS. During a mean follow-up of 5 ± 3 months, 250 AMS were collected. The IEGM analysis confirmed a true AF episode in 193 of 250 AMS (77.2%). Using the contiguity criterion, 47 of 57 (82.5%) inappropriate AMS episodes were isolated (there were no other AMS within 5 minutes), whereas 54 of 193 (27.9%) appropriate AMS episode were isolated. Adopting both length and contiguity criteria the specificity of AMS in detecting true AF episodes increased from 77.2% to 93.2% at the cost of 11.9% loss of original sensitivity. Combining the length and contiguity criteria, we were able to improve the specificity of the AMS in the detection of AF.     

Temporary Atrial Pacing in the Prevention of Postoperative Atrial Fibrillation

Background: Atrial fibrillation (AF) is a common complication after coronary artery bypass grafting (CABG). Since its prevention with prophylactic drug therapy has limited success, alternative approaches are desirable. This study examined the efficacy of atrial or biatrial pacing, compared with no pacing, on the incidence of AF after isolated CABG.
Methods: From August 2002 to September 2004, 240 patients underwent CABG. After surgery, right and left atrial epicardial pacing wires were implanted for 72 hours of temporary pacing. Patients were randomly assigned to one of three groups: no pacing (control group), right atrial (RA), and biatrial (BiA) pacing. Cardiac rhythm was monitored continuously during intensive care, or daily on the ward. The primary endpoints of this study were an episode of AF occurring up to 72 hours after CABG and the risk factors correlated with this event.
Results: Atrial and BiA pacing significantly lowered the incidence (1.25% vs 25%, P = 0.001) of AF episodes, and were both correlated (odd ratio 0.038; 95% confidence interval 0.005–0.29) with a decrease in rates of postoperative AF. Multivariable analysis identified older age (odd ratio 1.074; 95% confidence interval 1.024–1.12) and no pacing as independent risk factors of postoperative AF.
Conclusions: Temporary right atrial or biatrial pacing after CABG significantly decreased the postoperative incidence of AF. Multivariable analysis identified older age and no pacing as predictors of AF occurrence .     

Long-Term Follow-Up After Right Atrial Radiofrequency Catheter Treatment of Paroxysmal Atrial Fibrillation

Catheter ablation of paroxysmal atrial fibrillation using long linear lesions in the right atrium is still under investigation, and its long-term follow-up is unknown. Methods: Thirty-six men and nine women (aged 51 ± 12 years) with symptomatic daily episodes of AF for 6 ± 5 years despite the use of 4.7 ± 1.5 antiarrhythmic drugs were studied between July 1994 and January 1996. Progressively longer ablation lines were performed in 3 groups of 15 consecutive patients each, using a 14-electrode catheter or a single-electrode dragging technique. Success was defined as atrial fibrillation elimination or recurrence for no longer than 6 hours over 3 months of observation. Patients who had fewer than 6 hours of atrial fibrillation per month were considered "improved." Medium- (11 ± 4 months) and long-term (26 ± 5 months) results were assessed clinically from a patient's diary and from Holter recordings. Results: After a follow-up of 11 months, 24 patients had a favorable result of the ablation procedure with or without additional antiarrhythmic drug therapy, representing 53% of the original cohort. After 26 ± 5 months of follow-up, these successful results were reduced to 17 patients (37%). Conclusions: After linear atrial ablation, a significant long-term attrition of arrhythmia-free patients was observed. This may be due to a combination of disease progression, incomplete linear block, and ineffective ablation of arrhythmogenic triggers.     

Prevalence and Predictors of New-Onset Atrial Fibrillation After Elective Surgery for Colorectal Cancer

There are only limited data on the prevalence and risk factors for postoperative atrial fibrillation (AF) after elective abdominal surgery. We retrospectively studied the clinical characteristics and hospital outcomes in 563 consecutive patients (mean age: 67 ± 13 years, 245 men) with colorectal cancer who underwent elective colectomy. The baseline clinical characteristics of patients who underwent open (OC) versus laparoscopic colectomy (LC) were similar. Postoperative AF developed in 25 patients (4.4%). Patients who developed postoperative AF were older (P = 0.017), had a higher prevalence of hypertension (P = 0.05), more major postoperative events (P = 0.02), an elevated neutrophil count on postoperative day (POD) 1 (P = 0.007), longer hospitalizations (P = 0.02), and were more likely to undergo OC (P = 0.067). In multiple regression analysis, independent predictors of postoperative AF were OC (odd ratio: 3.3 , 95% confidence interval: 1.3–8.0, P = 0.008), and an elevated neutrophil count on POD 1 (odd ratio: 3.2 , 95% confidence interval: 1.3–7.8, P = 0.01). The incidence of postoperative AF after elective colorectal cancer surgery was approximately 4%. Postoperative AF was more commonly observed in patients with OC versus LC and in those with elevated postoperative neutrophil counts.     

自主神经对冠状动脉搭桥术后心房颤动的影响

目的:通过心率变异性(heart rate variability,HRV)分析,探察CABG术后的自主神经活性对发生AF的作用。方法:对CABG术后发生AF的20例患者进行24 h动态心电图记录,并进行HRV时域、频域分析,同时设年龄、性别、一般临床特征相匹配的CABG术后非AF(NAF)患者为对照。结果:AF组心率明显快于NAF组。HRV各时域、频域指标两组比较无统计学意义。结论:交感神经过度激活可能是CABG术后AF发生的机制之一。     

Improved Efficacy of Mode Switching During Atrial Fibrillation Using Automatic Atrial Sensitivity Adjustment

Automatic mode switching (AMS) during atrial fibrillation (AF) in a dual chamber pacemaker is dependent on the accurate detection of an atrial electrogram. As atrial amplitude is often reduced during AF compared with sinus rhythm, this may result in failure of the AMS and a rapid ventricular response. In addition, undersensing of AF may result in competitive atrial pacing that sustains AF. We hypothesize that the use of automatic atrial sensitivity adjustment (ASA) may enhance AF sensing in a dual chamber pacemaker. We studied the AMS response with and without ASA of the Marathon DDDR (model 294–09, Intermedics, Inc.) pacemaker in 10 patients with paroxysmal AF. Intracardiac atrial electrograms during sinus rhythm and induced AF were recorded onto an analog tape recorder. They were replayed into the pacemaker to assess the AMS response at various starting atrial sensitivities from 3.5 to 0.8 mV with ASA activated and without. Atrial amplitude was reduced during AF. The higher the initial atrial sensitivity, the better is the AMS response and the lower the incidence of AF undersensing. The percentage of AMS before ASA ranged from 2.1% at an atrial sensitivity 3.5 mV to 95.6% at highest sensitivity of 0.5 mV (P < 0.05). After 10 minutes of ASA, the AMS response was improved from 1.7% to 50.6% and from 9.5% to 50.9% at starting atrial sensitivities of 3.5 mV and 2.5 mV, respectively (P < 0.05 in both instances). Undersensing during AF was also significantly reduced after ASA from 70% to 10% at a sensitivity of 3.5 mV and from 33.8% to 10.8% at 2.5 mV. There was no increase in oversensing. In four patients with paroxysmal AF with an implanted pacemaker, ASA improved AMS response in patients with a low implant atrial amplitude. In conclusion, efficacy of mode switching and AF sensing are dependent on the programmed atrial sensitivity, which can be enhanced with the use of ASA, particularly when P wave sensing during AF is borderline.     

非瓣膜性房颤患者的左心耳特点分析

目的：分析非瓣膜性房颤患者左心耳入口内径、左心耳长度及左心耳射血速率的特点。方法：以我院收治的237例房颤患者为研究对象,回顾性分析阵发性房颤与持续性房颤患者左心耳入口内径、长度及左心耳射血速率的差异,并分析房颤患者左心耳入口内径、长度及射血速率的临床相关因素。结果：与阵发性房颤组相比,持续性房颤组左心耳入口内径显著增大,具有统计学意义（P<0.05）,而两组患者的左心耳长度及左心耳射血速率无统计学差异。Spearman相关分析显示左心耳入口内径与身高、房颤病史长短、左房前后径、左室收缩末内径（left ventricular end-systolic diameter LVESD）、左室舒张末内径（left ventricular end-diastolic diameter LVEDD）呈正相关（P<0.05）,与左室射血分数（left ventricular ejection fraction LVEF)呈负相关（P<0.05）;左心耳长度与左房前后径、LVESD、LVEDD呈正相关（P<0.05）,与LVEF呈负相关(P<0.05);左心耳射血速率与年龄、房颤病史长短、左房前后径、LVESD呈负相关（P<0.05）,与LVEF呈正相关(P<0.05)。结论：持续性房颤患者左心耳入口内径大于阵发性房颤患者,左心耳的入口内径、长度、射血速率与多种因素相关。     

Spontaneous Reinitiation of Atrial Fibrillation Following Transvenous Atrial Defibrillation

Spontaneous reinitiation of atrial fibrillation (AF) has not been systematically looked at in patients undergoing transvenous AF. This study involved 11 patients, the mean age 60 ± 8 years. 3 male and 8 female, in whom transvenous atrial defibrillation successfully converted AF to sinus rhythm. Eight patients had paroxysmal AF and three patients had chronic persistent AF for 4 weeks or more. Four patients were taking antiarrhythmic medications at the time of testing. Multipolar transvenous catheters were positioned inside the coronary sinus, right atrium, and the right ventricle. Atrial defibrillation testing was performed using the METRIX atrial defibrillation system in nine patients and the Ventritex HVSO2 in the remaining two patients. A total of 64 therapeutic shocks (range 3–11) were delivered in the 11 patients, and 31 of these successfully converted AF to sinus rhythm. In four patients spontaneous AF was reinitiated following 12 successful transvenous atrial defibrillation episodes. The mean time to reinitiation of AF following shock delivery and restoration of sinus rhythm was 8.26 ± 5.25 seconds, range 1.8–19.9 seconds. All 12 episodes of spontaneous AF were preceded by a spontaneous premature atrial complex. The coupling interval of the premature atrial complexes was 443 ± 43 ms, range 390–510 ms. None of the patients taking antiarrhythmic medications or those demonstrating no premature atrial complexes had spontaneous reinitiation of AF. In conclusion, spontaneous reinitiation of AF can occur in a significant proportion of patients with AE undergoing transvenous atrial defibrillation. This phenomenon is preceded by the occurrence of atrial premature complex. Findings of this study may have significant clinical implications.(PACE 1998; 21:1105–1110)     

Dynamics of Focal Fibrillation Waves during Persistent Atrial Fibrillation

The incidence and appearance of focal fibrillation waves on the right and left atrial epicardial surface were visualized during 10 seconds of persistent atrial fibrillation in a 71‐year‐old woman with valvular heart disease. The frequent, nonrepetitive, widespread, and capricious distribution of focal waves suggests that transmural conduction of fibrillation waves is most likely the mechanism underlying focal fibrillation waves.     

Mode Switch Despite Undersensing of Atrial Fibrillation in ODD Pacing

Mode switching algorithms are commonly used to protect the ventricles against high rates induced by atrial tachycardia. In the case of atrial fibrillation (AF), the response of these algorithms depends on the quality of atrial sensing. The Chorum 7234 DDDR pacemaker uses a new mode switching algorithm, based on a statistical analysis of the atrial rhythm. It includes two criteria of diagnosis: "high" if more than 28 of 32 cycles are abnormally accelerated; and "low" if more than 36 of 64 cycles are abnormally accelerated. Methods: From a taped database of electrophysiological studies, episodes of AF lasting more than 2 minutes were selected. A tape recorder replayed the atrial signals into an external Chorum device. Each episode was replayed eight times with a programmed atrial sensitivity increasing from 0.4 –2.0 mV. For each criterion of diagnosis and each programmed sensitivity, the percentage of atrial sensing, the time to switching, and the mean ventricular rate were measured. Ten episodes of AF from 10 patients (9 men and 1 woman; ages 62 ± 16 years) were included: 1.95 ± 0.97 mV and 196 ± 64 ms. The sensitivity of the algorithm to diagnose atrial tachycardia reached 100%, for an atrial sensitivity set between 0.4 and 1.0 mV. The mean percentages of atrial sensed events were 74%± 18% and 46%± 9% for the "high" and "low" criteria, respectively. The mean diagnostic times were 28 ± 26 seconds and 68 ± 27 seconds, respectively. Sensing of < 23% of AF events resulted in failure to diagnose the arrhythmias by both algorithms. In the event of diagnostic failure, the mean ventricular pacing rate was 79 ± 9 ppm. Conclusion: Up to an atrial sensitivity of 1 mV, 100% of AF episodes were diagnosed. The Chorum mode switching algorithms are 100% reliable if > 45% of the AF waves are sensed. In the event of switching failure, the ventricle is protected by an average rate remaining below 80 ppm. (PACE 1996;     

Long-Term Results of Hybrid Therapy in Patients with Atrial Fibrillation Who Develop Atrial Flutter During Flecainide Infusion

The flecainide infusion test has been proposed to screen candidates for hybrid pharmacological and ablation therapy. We report the long-term follow-up of 154 consecutive patients with paroxysmal or persistent atrial fibrillation (AF) who developed atrial flutter (AFL) during flecainide infusion (IC AFL), treated with inferior vena cava-tricuspid annulus isthmus catheter ablation and oral flecainide (hybrid therapy). Over a mean of 54.1 ± 13.1 months 82 patients (53%) remained free of AF and AFL. Flecainide was discontinued because of adverse effects in 6 patients (4%). A history of persistent AF, and the documentation of ≥1 spontaneous AFL episode before the flecainide test were independent predictors of successful hybrid therapy. In patients with paroxysmal AF without documented spontaneous AFL, the long-term efficacy of hybrid therapy was 38.5% (P = 0.03). The flecainide infusion test reliably detects candidates for hybrid therapy. The efficacy of this therapy is maintained over the long-term with a high patient compliance.