Surgery for Paroxysmal Atrial Fibrillation in the Setting of Mitral Valve Disease: A Role for Pulmonary Vein Isolation?

BACKGROUND

It is unknown whether pulmonary vein isolation or a complete Cox-Maze procedure is needed to ablate paroxysmal atrial fibrillation in patients with mitral valve disease. Our objective was to assess the impact of different surgical treatments for this arrhythmia in patients undergoing mitral valve surgery.

METHODS

From July 1993 to January 2004, 152 patients underwent combined surgical treatment of paroxysmal atrial fibrillation and mitral valve disease. Ablation procedures included pulmonary vein isolation alone (n = 31, 20%), pulmonary vein isolation with left atrial connecting lesions (n = 80, 53%), and Cox-Maze (n = 41, 27%). The latter had longer durations of atrial fibrillation than the former (p < 0.0001). Rhythm documented on 1,225 postoperative electrocardiograms was used to estimate prevalence of, and risk factors for, atrial fibrillation across time. Ablation failure was defined as occurrence of atrial fibrillation any time beyond 6 months after operation.

RESULTS

Prevalence of postoperative atrial fibrillation peaked at 22% at 2 weeks and declined to 9% at 1 year. Risk factors included older age (p = 0.09), larger left atrium (p = 0.05), and rheumatic (p = 0.003) and degenerative etiologies (p = 0.03). Freedom from ablation failure was 84% at one year. Ablation procedure did not affect prevalence of atrial fibrillation or incidence of ablation failure.

CONCLUSIONS

Pulmonary vein isolation alone may be adequate treatment for patients with paroxysmal atrial fibrillation undergoing mitral valve surgery, particularly when it is of short duration. A randomized trial is necessary to examine this strategy, especially in patients with longer duration of paroxysmal atrial fibrillation.

The Cox maze procedure in mitral valve disease: Predictors of recurrent atrial fibrillation

OBJECTIVES

The Cox maze procedure is the gold standard for ablation of atrial fibrillation in patients undergoing mitral valve surgery, and new approaches to atrial fibrillation ablation must be compared with it. Therefore, we sought to determine the time-related prevalence of atrial fibrillation and its risk factors after combined Cox maze and mitral valve surgery.

METHODS

From November 1991 through January 2004, 263 patients (mean left atrial diameter, 5.8 +/- 1.2 cm) underwent combined mitral valve surgery (repair in 71%) and a cut-and-sew Cox maze procedure for atrial fibrillation (permanent, 74%; persistent, 7%; paroxysmal, 16%). Rhythm documented on 2367 postoperative electrocardiograms was used to estimate the prevalence of atrial fibrillation across time.

RESULTS

Hospital mortality was 1.9%. Postoperative atrial fibrillation prevalence peaked at 36% at 2 weeks, decreasing to 21% at 5 years. Risk factors for higher postoperative atrial fibrillation prevalence varied with time and included longer duration of preoperative atrial fibrillation (P = .003), larger left atrial diameter (P = .01), older age (P = .0002), and higher left ventricular mass index (P = .02).

CONCLUSIONS

In some patients undergoing mitral valve surgery and a Cox maze procedure, atrial fibrillation recurs over time, mandating close, long-term follow-up of heart rhythm. Earlier operation and left atrial size reduction should be considered to improve results in selected patients.

Surgical ablation of atrial fibrillation with bipolar radiofrequency as the primary modality

OBJECTIVES

In studying cardiac surgical patients undergoing atrial fibrillation ablation with bipolar radiofrequency, we sought to (1) quantify the time-related prevalence of atrial fibrillation postoperatively and identify its risk factors and (2) determine time-related ablation failure and its risk factors.

METHODS

From November 2001 to January 2004, 513 patients underwent atrial fibrillation ablation (bipolar radiofrequency alone or with cryothermy) and other cardiac operations. Rhythm documented on 3495 postoperative electrocardiograms was used to estimate the prevalence of and risk factors for atrial fibrillation across time. Ablation failure was defined as occurrence of atrial fibrillation any time beyond 6 months after operation.

RESULTS

Prevalence of postoperative atrial fibrillation peaked at about 1 month, decreased to 13% at 6 months, and gradually increased thereafter. Risk factors associated with increased prevalence varied by time period and included older age ( P = .004) for early occurrence, lesion set in permanent atrial fibrillation ( P = .02) for late occurrence, and larger left atrial diameter ( P = .02) and permanent atrial fibrillation ( P < .0001) for occurrence across the entire time span. Freedom from ablation failure was 72% at 12 months. Risk factors for ablation failure included lesion set in permanent atrial fibrillation ( P = .001), longer duration of atrial fibrillation ( P = .01), and larger left atrial diameter ( P = .03).

CONCLUSIONS

Bipolar radiofrequency enables extension of ablation to most cardiac surgical patients with atrial fibrillation. Recurrence is influenced by the type and duration of atrial fibrillation, choice of lesion set in permanent atrial fibrillation, and left atrial size. Early operation, careful choice of lesion set, and left atrial reduction might enhance results.

Usefulness of Doppler assessment of pulmonary vein and left atrial appendage flow following pulmonary vein isolation of chronic atrial fibrillation in predicting recovery of left atrial function

Atrial fibrillation (AF) is a widespread condition that causes significant morbidity and mortality. Recently, pulmonary venous (PV) isolation using radiofrequency ablation has been used successfully to exclude the pulmonary venous ostia, resulting in correction of AF. Further, miniaturized high-frequency ultrasound phased-array transducers currently provide Doppler and 2-dimensional imaging during the ablation procedure. We examined atrial function and its determinants using intracardiac echocardiography before and after PV isolation in 45 patients who had chronic AF (56 +/- 11 years old). PV, left atrial (LA) appendage, and mitral and tricuspid flows were recorded. Recovery of booster pump function (defined by the presence of mitral inflow A wave, LA appendage a-wave, and PV A-reversal wave velocities >10 cm/s) was observed in 39 of 45 patients (86.6%). PV flow systolic wave before and after ablation correlated with the degree of LA booster pump function after PV isolation. An early systolic PV flow peak velocity >57.47 cm/s predicted "good" LA booster pump function recovery with 96% specificity. Diastolic LA appendage emptying in AF correlated (p <0.001) and predicted good LA booster pump function with 92% specificity for velocities >46.4 cm/s. Thus, monitoring LA function during PV isolation for chronic AF is feasible. Most patients recovered LA booster pump function immediately after PV isolation, and the degree of recovery correlated with LA reservoir function. Preserved reservoir function during AF is predictive of satisfactory recovery of booster pump function after PV isolation.

Response to Pharmacological Challenge of Dissociated Pulmonary Vein Rhythm

Dissociated pulmonary vein rhythm.

INTRODUCTION

Characterization of the electrophysiologic behavior of the pulmonary vein (PV) triggers initiating atrial fibrillation (AF) is still lacking. We conducted the current study to evaluate the behavior of the dissociated PV rhythm (PVD) observed after electrical disconnection from the left atrium of the PV responsible for initiation of AF.

METHODS AND RESULTS

Four hundred and seven consecutive patients (102 women; mean age 55+/-11 years) presented for ablation of symptomatic AF to our laboratory. After isolation, sustained dissociated rhythm (>10 minutes) was documented in 2.1% (34 of 1,568 PVs) of the PVs (initiating AF prior to isolation). Adenosine (18 mg IV bolus), verapamil (10 mg IV bolus), phenylephrine (200 mcg bolus followed by infusion at 100 mcg/hour), and isoproterenol (infusion rate of 15 mcg/hour) were administered in these patients. The cycle length of the PV rhythm before and after the administration of drugs was measured. Adenosine prolonged the sinus node (SN) cycle length (from 750+/-105 to 1,900+/-200 ms; P<0.05) and suppressed the PVD. Isoproterenol shortened both the SN (from 750+/-105 to 420+/-150 ms; P<0.05) and the PVD (from 2,225+/-300 to 800+/-190 ms; P<0.05) cycle length. A similar response to adenosine and isoproterenol of the PV firing was observed prior to isolating the arrhythmogenic PV. Phenylephrine prolonged the cycle length of both the SN (from 740+/-115 to 960+/-90 ms; P<0.05) and the PV rhythm (from 2,200+/-300 to 2,355+/-280 ms; P=0.87). Verapamil did not cause a significant change either in the SN or in the PVD cycle length.

CONCLUSION

Our data suggest that the PVD within isolated PV responsible for initiating AF exhibits a response to pharmacologic agents similar to the SN cells.

Incessant nonreentrant tachycardia due to simultaneous conduction over dual atrioventricular nodal pathways mimicking atrial fibrillation in patients referred for pulmonary vein isolation

It has been reported that conduction over the fast and slow pathways of the AV node can occur simultaneously, leading to a double ventricular response from each atrial beat. We report the cases of two patients referred to us for evaluation of symptomatic, incessant, and irregular narrow-complex tachycardia, misdiagnosed as atrial fibrillation, for consideration of pulmonary vein isolation. At presentation, careful evaluation of the electrograms revealed the presence of two ventricular activations for each atrial beat. At electrophysiologic study, both patients were found to have nonreentrant tachycardias arising from simultaneous conduction over the fast and slow pathways of the AV node. In one patient, the tachycardia had resulted in cardiomyopathy. Slow AV nodal pathway ablation performed in both patients resulted in cure of their tachycardias and recovery of ventricular function in the patient with cardiomyopathy.

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.

Moricizine induced increase in pacing threshold

A 72-year-old woman who was experiencing incessant ventricular tachycardia and recurrent automatic implantable cardioverter defibrillator (AICD) firing despite amiodarone therapy was referred to the Cleveland Clinic Foundation. Myocardial ischemia and infarction were ruled out by standard means. Several antiarrhythmic medications were tried previously without success. Moricizine, 200 mg three times daily, was initiated and controlled the ventricular tachycardia. However, after the dose of moricizine was titrated upward, the patient became symptomatically bradycardic and the ECG exhibited 2:1 block of her paced rhythm and an increased ventricular pacing threshold.

Circumferential ultrasound ablation for pulmonary vein isolation: analysis of acute and chronic failures

INTRODUCTION

In patients undergoing circumferential isolation of the pulmonary veins with an ultrasound ablation system, we analyzed the temperatures achieved while delivering circumferential ostial lesions in the pulmonary veins. We also reviewed the angiograms obtained during the procedure and identified anatomic variants that could be responsible for ineffective lesion formation.

METHODS AND RESULTS

During the early clinical use in 33 patients, a total of 85 veins were ablated. A mean of 16.9 +/- 12.3 ablations were delivered per patient, and a mean of 6.7 ablations per vein were applied. Entry block was assessed by placing a deflectable octapolar or a circular catheter in the vein. The following anatomic characteristics and technical limitations were identified as possible reasons for ineffective energy delivery: (1) funnel-shaped ostium; (2) ostial diameter larger than the balloon diameter; (3) inability to deliver the catheter to the right inferior or other vein ostia; (4) ostial instability; (5) early branching of the vein; and (6) eccentric position of the ultrasound transducer in the vein. In patients with recurrence of atrial fibrillation, 40% of the ostial lesions reached a temperature >60 degrees C. However, in patients cured by the ablation, 64% of the ostial lesions reached a temperature >60 degrees C (P < 0.06). At least 12 of the 20 chronic recurrences could have been related to technical limitations of the first system. Duration of atrial fibrillation and eccentric deployment of the ultrasound transducer were more frequent in patients with recurrence of arrhythmias at follow-up.

CONCLUSION

Ostial anatomy of the veins may affect delivery of ultrasound energy to achieve circumferential lesions. Energy delivery at the ostium with a temperature > 60 degrees C may be important to maximize success. Reconfiguration of the system to overcome the shortcomings identified in the initial experience could increase its performance.

Matching approved "nondedicated" hardware to obtain biventricular pacing and defibrillation: feasibility and troubleshooting

Biventricular ICDs may offer increased benefit for patients with severe congestive heart failure and ventricular arrhythmia. Currently there are no approved dedicated biventricular ICDs available. Twenty-one consecutive patients who had approved nondedicated hardware implanted for biventricular pacing and defibrillation were included in this study. All device therapies were evaluated using stored electrograms. During mean follow-up at 13 +/- 7 months, 8 (36%) patients had inappropriate shocks. Ventricular fibrillation therapy was delivered for slow ventricular tachycardia because of double counting in two patients. In one patient, AV nodal reentrant tachycardia below detection rate cut off triggered device therapy because of ventricular double counting. Sinus tachycardia or premature atrial contraction initiating AV conduction and ventricular double counting resulted in shocks in five patients. The number of shocks per patient ranged from 1 to 64. Two patients required transient disconnection of the LV lead and subsequent ICD generator replacement for premature battery depletion. Two patients required AV junction ablation and three needed slow pathway ablation. Two patients were treated by upgrading to a device that was capable of a higher atrial tracking rate. The patients with impaired AV conduction or constant ventricular pacing did not have inappropriate therapy for sinus tachycardia or supraventricular arrhythmia. Use of conventional nondedicated hardware for biventricular pacer/defibrillator is feasible but should be considered only in patients with poor AV node function or less likely to require antitachycardic therapy, to avoid ICD double counting of ventricular sensed events and consequent high incidence of inappropriate therapies.