Serial change in the atrial transport function after the radial incision approach

Atrial remodelling and function: implications for atrial fibrillation surgery

The exact mechanism of atrial fibrillation (AF) is still incompletely understood. A number of alterations that impact focal electrical discharge, the atrial substrate and modulating factors contribute to its pathogenesis. Atrial remodelling (resulting in atrial cardiomyopathy) sets the stage for AF development. Once present, AF results in the loss of synchronized atrial contraction, which affects ventricular filling and atrial reservoir and conduit functions. Passive atrial function is particularly important in patients with left ventricular diastolic dysfunction. AF can cause tachycardiomyopathy, a mostly reversible cardiac alteration induced by tachycardia. At a structural level, atrial support is also instrumental to the function of atrioventricular valves. All of these functions can be recovered to variable degrees via rhythm control strategies. Surgical and hybrid ablation show very promising results, especially in patients with a more advanced disease substrate. This review highlights the pathophysiological aspects of AF related to left atrial function and their practical implications for surgical rhythm management.

Limited left atrial surgical ablation effectively treats atrial fibrillation but decreases left atrial function

AIMS

Limited left atrial (LA) surgical ablation with bipolar radiofrequency is considered to be an effective procedure for treatment of atrial fibrillation (AF). We studied whether limited LA surgical ablation concomitant to cardiac surgery is able to maintain LA function.

METHODS AND RESULTS

Thirty-six consecutive patients (age 66 ± 12 years, 53% male, 78% persistent AF) scheduled for valve surgery and/or coronary revascularization and concomitant LA surgical ablation were included. Epicardial pulmonary vein isolation (PVI) and additional endo-epicardial lines were performed using bipolar radiofrequency. An age- and gender-matched control group (n = 36, age 66 ± 9 years, 69% male, 81% paroxysmal AF) was selected from patients undergoing concomitant epicardial PVI only. Left atrial dimensions and function were assessed on two-dimensional echocardiography preoperatively and at 3- and 12-month follow-up. Sinus rhythm (SR) maintenance was 67% for limited LA ablation and 81% for PVI at 1-year follow-up (P = 0.18). Left atrial volume decreased from 72 ± 21 to 50 ± 14 mL (31%, P < 0.01) after limited LA ablation and from 65 ± 23 to 56 ± 20 mL (14%, P < 0.01) after PVI. Atrial transport function was restored in 54% of patients in SR after limited LA ablation compared with 100% of patients in SR after PVI. Atrial strain and contraction parameters (LA ejection fraction, A-wave velocity, reservoir function, and strain rate) significantly decreased after limited LA ablation. After PVI, strain and contraction parameters remained unchanged.

CONCLUSION

Even limited LA ablation decreased LA volume, contraction, transport function, and compliance, indicating both reverse remodelling combined with significant functional deterioration. In contrast, surgical PVI decreased LA volume while function remained unchanged.

Modified radial v/s biatrial maze for atrial fibrillation in rheumatic valvular heart surgery

BACKGROUND

Atrial fibrillation (AF) is commonest sustained atrial arrhythmia producing high morbidity. Although Cox's Maze III procedure cures AF in majority, reduced atrial transport function (ATF) is a concern. Radial approach with ablation lines radial from sinus node towards atrioventricular annulii and parallel to atrial coronary arteries, has shown better ATF.

METHODS

Single blind open randomized prospective study of 80 patients was undertaken in two groups (40 each) of modified Cox's maze III and modified radial approach, to evaluate conversion to normal sinus rhythm (NSR) and ATF. Patients undergoing surgery for rheumatic valvular heart disease with continuous AF were prospectively randomized. Ablation lines were created with radiofrequency (RF) bipolar coagulation with cryoablation for the isthmal lesions and coronary sinus. Results were compared at 6 months and ATF was evaluated by atrial filling fraction (AFF) and A/E ratio on echocardiography.

RESULTS

The rate of conversion to NSR in both groups was statistically insignificant by Fisher's exact test (p > 0.05). ATF was better in modified radial approach compared to modified Cox's Maze III (A/E compared by unpaired t test:0.52 ± 0.08 v/s 0.36 ± 0.10; p < 0.05. AFF compared using Mann Whitney U test: median AFF for radial group was 23 v/s 20 for biatrial group; p < 0.05).

DISCUSSION

In patients with AF undergoing rheumatic valvular surgery, radiofrequency radial approach is as effective as modified Cox's maze III for conversion to NSR with better atrial transport function.

Atrial Coronary Arteries in Areas Involved in Atrial Fibrillation Catheter Ablation

Background—

The proximity to vascular structures is a limiting factor during radiofrequency ablation. However, little or no attention has been given to the atrial arterial circulation during the development of atrial fibrillation (AF) catheter ablation techniques.

Methods and Results—

We examined the atrial arterial circulation in areas involved in AF ablation in 24 heart specimens by colored resin injection and careful dissection. The sinus node artery (SNA) arose from the circumflex artery in 42% of case; proximal to the LA appendage in 29%, crossing the left atrium (LA) anterior wall; and after the LA appendage in the remaining 13%, crossing the mitral isthmus and passing close to the left pulmonary veins (PVs), the LA roof, and the right superior PV. In 58%, the SNA arose from the right coronary artery. Major arteries (≥1 mm in external diameter) were found in the mitral isthmus in 54%, at the LA roof in 54%, and at the LA anterior wall in 29%. Around the left PV ostia, there were areas with major arteries in up to 37% (at the roof and inferior segments) and around the right PV ostia in up to 29% (at the roof segment).

Conclusions—

Major atrial coronary arteries, including the SNA, were commonly found in the areas involved in AF ablation and could cause difficulties in obtaining transmural lesions and electric isolation or even lead to ischemic sinus node or atrial dysfunction.

Atrial function after ablation procedure in patients with chronic atrial fibrillation using steady-state free precession magnetic resonance imaging

BACKGROUND

Surgical ablation procedures are an established surgical procedure for restoration of sinus rhythm and reestablishment of atrial function in patients with chronic atrial fibrillation. The purpose of this study was to evaluate the feasibility and reproducibility of steady-state free precession magnetic resonance imaging (SSFP MRI) for examination of atrial dimensions and function after ablation procedures.

METHODS

Nineteen patients (mean age, 63.1 +/- 11.7 years) being at least six months after surgical ablation procedure, with stable sinus rhythm, were selected for the study. They underwent cardiac MRI. End-diastolic and end-systolic volumes were measured using Simpson's rule. The presence of visual contraction was visually assessed.

RESULTS

In MRI evaluation mean end-diastolic volume of the right atrium and left atrium after an ablation procedure was 127 +/- 45 mL and 163 +/- 50 mL, respectively. Mean stroke volume was 23 +/- 15 mL and 26 +/- 12 mL for the right and left atrium. Mean ejection fraction of the right atrium was 0.19 +/- 0.14 and 0.17 +/- 0.1 for the left atrium. An atrial kick of both atria was observed in 8 of 19 (47%) patients. An atrial kick of only the right atrium was observed in an additional 13 of 19 (68%) patients.

CONCLUSIONS

The anticipated events after a surgical ablation procedure are the restoration of atrial contractility and the associated atrial kick, thereby enhancing cardiac output and decreasing the risk of thromboembolism. Evaluation of atrial function after an ablation procedure using SSFP MRI is feasible and allows a standardized documentation of postoperative atrial function, thus allowing evaluation of the surgical outcome in a reproducible way. Echocardiographic evaluation seems to underestimate the transport function of the atrium.

Assessment of Atrial Function

This article discusses the traditional and more recent echocardiographic measures that have been employed to evaluate atrial function. Conventional parameters commonly used and reported in the literature include the study of the various phases of atrial activity using atrial volume measurements, the peak A wave velocity, its velocity time integral (VTI) and the fraction of atrial contribution (all obtained from transmitral flow), as also the atrial ejection force. Newer parameters for atrial function assessment include Doppler tissue imaging (DTI) including segmental atrial contractility using colour Doppler tissue imaging (CDTI) and estimates of atrial strain and strain rate.

Current strategies in the surgical treatment of atrial fibrillation: review of the literature and Onze Lieve Vrouw Clinic's strategy

Atrial fibrillation is the most common rhythm disturbance in clinical practice. It is a major source of stroke and morbidity. Although the Cox maze procedure effectively eliminates atrial fibrillation in most patients, the procedure has not found widespread application. As a consequence, new operations that use alternative sources of energy, such as radiofrequency, microwave, cryothermy, laser, and ultrasound have emerged to surgically create lesion sets to treat atrial fibrillation. This article reviews the fundamentals and current strategies in the surgical treatment of atrial fibrillation.

A novel atrial volume reduction technique to enhance the Cox maze procedure: Initial results

OBJECTIVE

Large left atrial diameter is reported to be a predictor for recurrent atrial fibrillation after the Cox maze procedure, and left atrial diameter by itself influences the chance of sinus rhythm recovery, as well as maintenance of sinus rhythm. However, additional cut-and-sew procedures to decrease left atrial diameter extend operative time and can cause bleeding. Thus we developed a no-bleeding, faster, and therefore less invasive left atrial volume reduction technique to enhance the Cox maze procedure.

METHODS

The modified Cox maze III procedure with cryoablation or the left atrial maze procedure in association with mitral valve surgery was performed in 80 patients with atrial fibrillation and enlarged left atria (> or =60 mm). Among them, 44 patients had the concomitant volume reduction technique (VR group); continuous horizontal mattress sutures for left atrial plication were placed on the left atrial wall along the pulmonary vein isolation line. Cryoablation was applied to the suture line so that the plicated left atrium is anatomically and electrically isolated. Another 36 patients did not have the volume reduction technique (control group).

RESULTS

The VR group had preoperative left atrial diameters similar to those of the control group (67.1 +/- 7.8 vs 64.5 +/- 6.7 mm) and a longer preoperative duration of atrial fibrillation (14.1 +/- 5.4 vs 9.5 +/- 5.1 years, P < .05) but had smaller postoperative left atrial diameters (47.6 +/- 6.3 vs 62.1 +/- 7.9 mm, P < .01). There were no differences in mean crossclamp/bypass time and chest tube drainage for 12 hours between the groups. Twelve months after surgical intervention, the sinus rhythm recovery rate of the VR group was better than that of the control group (90% vs 69%, P < .05).

CONCLUSIONS

Even in patients with long-standing atrial fibrillation and an enlarged left atrium, maze procedures concomitant with the novel left atrial volume reduction technique improved the sinus rhythm recovery rate without increasing complications. Although further study with a larger number of patients and a longer follow-up period is needed, this safe and thus far potent technique that catheter-based ablation cannot copy might extend indication of the Cox maze procedure for patients with tough atrial fibrillation.

Effect of left atrial circumferential ablation for atrial fibrillation on left atrial transport function

BACKGROUND

The effects of left atrial (LA) circumferential ablation on LA function in patients with atrial fibrillation (AF) have not been well described.

OBJECTIVES

The purpose of this study was to determine the effect of LA circumferential ablation on LA function.

METHODS

Gated, multiphase, dynamic contrast-enhanced computed tomographic (CT) scans of the chest with three-dimensional reconstructions of the heart were used to calculate the LA ejection fraction (EF) in 36 patients with paroxysmal (n = 27) or chronic (n = 9) AF (mean age 55 +/- 11 years) and in 10 control subjects with no history of AF. Because CT scans had to be acquired during sinus rhythm, a CT scan was available both before and after (mean 5 +/- 1 months) LA circumferential ablation (LACA) in only 10 patients. A single CT scan was acquired in 8 patients before and in 18 patients after LACA ablation. Radiofrequency catheter ablation was performed using an 8-mm-tip catheter to encircle the pulmonary veins, with additional lines along the mitral isthmus and the roof.

RESULTS

In patients with paroxysmal AF, LA EF was lower after than before LACA (21% +/- 8% vs 32 +/- 13%, P = .003). LA EF after LA catheter ablation was similar among patients with paroxysmal AF and those with chronic AF (21% +/- 8% vs 23 +/- 13%, P = .7). However, LA EF after LA catheter ablation was lower in all patients with AF than in control subjects (21% +/- 10% vs 47% +/- 5%, P < .001).

CONCLUSION

During medium-term follow-up, restoration of sinus rhythm by LACA results in partial return of LA function in patients with chronic AF. However, in patients with paroxysmal AF, LA catheter ablation results in decreased LA function. Whether the impairment in LA function is severe enough to predispose to LA thrombi despite elimination of AF remains to be determined.

A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation

OBJECTIVE

The Cox maze III procedure has excellent long-term efficacy in curing atrial fibrillation. It has not been widely practiced because it is technically challenging and requires prolonged cardiopulmonary bypass. The aim of this study was to examine a simplified Cox maze III procedure that uses bipolar radiofrequency energy as an ablative source.

METHODS

Beginning January 2002, a total of 40 consecutive patients underwent a modified Cox maze III procedure with bipolar radiofrequency energy. Nineteen had a lone maze procedure and 21 had a maze procedure plus a concomitant operation. One month after the operation, the first 8 patients were investigated with high-resolution magnetic resonance imaging. Patients were followed up monthly with clinical examination and electrocardiography.

RESULTS

There was no operative deaths. The crossclamp times were 47 +/- 26 minutes for the modified lone Cox maze III procedure and 92 +/- 37 minutes for the Cox maze III procedure plus concomitant procedures. These were significantly shorter than our previous times for the traditional Cox maze III procedure (93 +/- 34 minutes and 122 +/- 37 minutes, respectively, P <.05). Follow-up magnetic resonance imaging showed no evidence of pulmonary vein stenosis, and atrial contractility was preserved in all patients. There were no late strokes. At 6-month follow-up, 91% of patients (21/23) were in sinus rhythm.

CONCLUSIONS

Bipolar radiofrequency ablation can be used to replace the surgical incisions of the Cox maze procedure. This energy source did not result in pulmonary vein stenosis. The modification of the Cox maze III procedure to use bipolar radiofrequency ablation simplified and shortened this procedure without sacrificing short-term efficacy.

Atrial Contraction After Surgical Isolation of the Left Atrial Posterior Wall Concomitant With Mitral Valve Replacement

BACKGROUND

Surgical isolation of the left atrial posterior wall (LA-PW isolation) can terminate chronic atrial fibrillation associated with mitral valve disease. However, atrial contraction after LA-PW isolation has not been evaluated.

METHODS AND RESULTS

The study group comprised 14 patients (mean age, 63+/-14 years) with mitral valve disease who recovered and maintained regular sinus rhythm after LA-PW isolation. Before the procedure, and 2-3 weeks and 1 year after the LA-PW isolation, the patients underwent an echocardiographic study. The left atrial (LA) diameter decreased after the LA-PW isolation and the change became significant 1 year later (before: 50.1+/-5.1 mm, after 2-3 weeks: 46.0+/-4.9 mm; p<0.05, after 1 year: 44.0+/-6.1 mm; p<0.05 vs before the operation). The left ventricular (LV) end-diastolic diameter, LV ejection fraction and LV fractional shortening did not change significantly from before the LA-PW isolation and after 1 year. The time - velocity integral of the atrial wave (Ai) and atrial filling fraction significantly increased (Ai: 4.5+/-2.1 cm vs 5.8+/-2.3 cm; p<0.05; atrial filling fraction: 15.4+/-7.7% to 19.2+/-8.3%; p<0.05) during the follow-up period.

CONCLUSION

LA-PW isolation can benefit the restoration of regular sinus rhythm and, furthermore, the recovery of atrial contraction.

Atrial fibrillation: current surgical options and their assessment

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with morbidity and mortality. Traditional surgical treatment of AF is the Cox-Maze III procedure, a complicated operation. New surgical approaches include alternate energy sources (radiofrequency, microwave, cryothermy) and simplified left atrial lesion sets. These operations cure AF in 70% to 80% of patients. This review describes contemporary and emerging surgical approaches to AF, synthesizes results of these operations, and proposes new standards for reporting results of AF treatment.

Atrial size and transport function after the Maze III procedure for paroxysmal atrial fibrillation

BACKGROUND

The Maze procedure is a curative surgical therapy for atrial fibrillation, restoring sinus rhythm and improving quality of life. Because the procedure results in tissue scarring, the atrial transport function is most likely affected.

METHODS

Seventeen patients with paroxysmal atrial fibrillation underwent the Maze III procedure without any concomitant valve operation. Atrial size and transport function were measured before and at 2, 6, and 24 months after operations with two-dimensional echocardiography and pulsed-wave Doppler.

RESULTS

Fifteen patients (88%) had signs of left atrial contractions as shown by the presence of a transmitral atrial filling wave on Doppler echocardiography at 6 months follow-up. The transmitral early filling wave and atrial filling wave were measured to calculate the early filling/atrial filling wave ratio, which increased from 1.2 before to 1.9 at 2 months after the Maze procedure (nonsignificant), and further to 2.8 at 24 months (p = 0.02). A decrease in the right and left atrial size was seen at 2 months after an operation, but no further decrease occurred.

CONCLUSIONS

In patients with paroxysmal atrial fibrillation, there is a progressive increase in the transmitral early filling/atrial filling wave ratio after the Maze procedure, consistent with a gradual decrease in the left atrial transport function.