Preservation of the right atrial appendage improves reduced plasma atrial natriuretic peptide levels after the maze procedure

Considerations for Left Atrial Appendage Occlusion During Cardiac Surgery

Atrial fibrillation is associated with an increased risk of stroke secondary to thrombus formation in the left atrial appendage. Left atrial appendage occlusion (LAAO) is an effective method of reducing the risk of stroke in patients with atrial fibrillation. Although LAAO does not remove the requirement for anticoagulation, it reduces the risk of stroke when compared to anticoagulation alone. We critically analyze the data on LAAO in cardiac surgery. We also discuss the methods of LAAO, the risks of LAAO, and patient populations that could benefit from LAAO. We discuss high-level evidence that LAAO at the time of cardiac surgery reduces the risk of stroke in patients with a history of atrial fibrillation. In patients without a history of atrial fibrillation undergoing cardiac surgery, we suggest that LAAO should be considered in select patients at high risk of atrial fibrillation and stroke, when technically feasible.

Impact of epicardial ablation of concomitant atrial fibrillation on atrial natriuretic peptide levels and atrial function in 6 months follow-up: does preoperative ANP level predict outcome of ablation?

Background

Epicardial ablation concomitant to cardiac surgery is an easy and safe approach to treat atrial fibrillation (AF), but its efficacy in longstanding persistent (LsPe) AF remains intermediate. Although larger left atrial size has been associated with worse outcome after ablation, biochemical predictors of success are not well established. The aim of this study was to evaluate relationship between biochemical marker, echo-characteristic and cardiac rhythm in 6 months follow-up after epicardial ultrasound (HIFU) ablation.

Methods

We included 78 consecutive patients, who underwent elective cardiac surgery. 42 patients with AF (11.9% paroxysmal, 23.8% persistent, 64.3% LsPeAF) underwent concomitant HIFU ablation (AF ablation group), 16 with AF underwent cardiac surgery without ablation (AF control) and 20 had preoperatively normal sinus rhythm (SR control). We measured plasma ANP secretion before, on postoperative day (POD) 1, POD 7 as well as 3 and 6 months after surgery. Moreover, we estimated cardiac rhythm and atrial mechanical function by Atrial Filling Fraction (AFF) and A-wave velocity in follow-up.

Results

Baseline ANP levels were higher in patients with LsPeAF, as compared to the paroxysmal and permanent AF and to the SR control group. Patients with LsPeAF (n = 27) who converted to SR had preoperatively smaller left atrial diameter (LAD) and LA area (p < 0.05) and higher ANP level (p = 0.009) than those who remained in AF at 6 months after ablation. Multivariate regression analysis revealed that only preoperative ANP level was an independent predictor of cardiac rhythm after ablation. Patients with LsPeAF and preoperative ANP >7.5 nmol/l presented with SR in 80%, in contrast to those with ANP <7.5 nmol/l who converted to SR in 20%. We detected gradual increase of AFF and A-velocity at 6 months after ablation (p < 0.05) solely in AF ablation group. ANP levels were increased on POD 1 in ablation group (p < 0.05), without changes in further follow-up.

Conclusion

Our results indicate that preoperative ANP levels may be a new biochemical predictor of successful epicardial ablation in patients with concomitant LsPeAF. HIFU ablation caused a significant improvement of atrial mechanical function and gradual increase of AFF and did not associate with alteration of atrial endocrine secretion at 6 months follow-up.

Evidence-based percutaneous closure of the left atrial appendage in patients with atrial fibrillation

Atrial fibrillation is the most common cardiac arrhythmia, and its prevalence is increasing. Cardioembolic stroke, most of the times secondary to thrombus formation in the left atrial appendage, is its most feared and life threatening consequence. Oral anticoagulation with vitamin-K-antagonists is currently the most used prophylaxis for stroke in patients with atrial fibrillation; unfortunately, its benefits are limited by a narrow therapeutic window and an increased risk for bleeding, making it often undesired. Percutaneous occlusion of the left atrial appendage is a novel alternative strategy for cardioembolic stroke prophylaxis in patients with atrial fibrillation at a high risk of stroke but with contraindication for long-term oral anticoagulation therapy. At present, several devices have been developed specifically for percutaneous occlusion of the left atrial appendage. Current results show good feasibility and efficacy for these devices, with a high rate of successful implantation, although also associated with the inherent potential periprocedural complications. This work reviews the current state of the art of percutaneous left atrial appendage closure for stroke prophylaxis in patients with atrial fibrillation.

Stroke prevention in patients with atrial fibrillation: Is the transcatheter occlusion of left atrial appendage already an alternative to anticoagulation?

Cardiac emboli in patients with atrial fibrillation are one of the major causes of ischemic stroke. Because the vast majority of these cardiac emboli descend from the left atrial appendage (LAA), the therapeutic strategy of percutaneous transcatheter occlusion of the LAA by means of a mechanical implant was a logical consequence. Three different devices have been developed and used in humans: PLAATO, WATCHMAN, and ACP. The PLAATO implant, a “soccer ball” shaped self-expanding nitinol cage has demonstrated stroke prevention capability in small, uncontrolled studies. The WATCHMAN implant, a “half rugby ball” shaped self-expanding nitinol cage, has demonstrated non inferiority compared to warfarin treatment in the randomized, controlled PROTECT AF trial. The ACP implant is also a self-expanding nitinol cage. However, its design is of fundamental difference compared to the other two implants. ACP consists of two parts connected by a short waist, which are an “ice-hockey puck” shaped body for the implant fixation in the appendage wall, and a flexible disc for sealing the appendage ostium. Due to the very flexible connecting waist between the two parts, ACP implant adapts itself to the LAA, which appears in significant individual structural variabilities. The currently unpublished initial experience with ACP in Europe is encouraging. Transcatheter occlusion of the LAA offers an appealing way to reduce the incidence of cardioembolic stroke in patients with atrial fibrillation. However, the concerns about procedural safety and the need for long-term follow up should be addressed before this potentially important technology is deployed widely. The transcatheter occlusion of left atrial appendage, therefore, has the potential to become, but is not yet a real alternative to anticoagulation.

Cardioembolic stroke in atrial fibrillation-rationale for preventive closure of the left atrial appendage

Atrial fibrillation is the most common cardiac arrhythmias, and a major cause of morbidity and mortality due to cardioembolic stroke. The left atrial appendage is the major site of thrombus formation in non-valvular atrial fibrillation. Loss of atrial systole in atrial fibrillation and increased relative risk of associated stroke point strongly toward a role for stasis of blood in left atrial thrombosis, although thrombus formation is multifactorial, and much more than blood flow irregularities are implicated. Oral anticoagulation with vitamin-K-antagonists is currently the most effective prophylaxis for stroke in atrial fibrillation. Unfortunately, this treatment is often contraindicated, particularly in the elderly, in whom risk of stroke is high. Moreover, given the risk of major bleeding, there is reason to be skeptical of the net benefit when warfarin is used in those patients. This work reviews the pathophysiology of cardioembolic stroke and critically spotlights the current status of preventive anticoagulation therapy. Various techniques to exclude the left atrial appendage from circulation were discussed as a considerable alternative for stroke prophylaxis.

Nesiritide following maze and mitral valve surgery

BACKGROUND

Fluid retention following "maze" and mitral valve surgery has been associated with diminished levels of atrial natriuretic peptide (ANP). We hypothesized prophylactic administration of nesiritide (human recombinant brain natriuretic peptide, NES, Natrecor, Scios, Fremont, CA, USA), which has similar physiologic properties to ANP and would promote diuresis in maze and mitral patients postoperatively.

METHODS

Randomized, blinded, prospective pilot study comparing patients undergoing maze and mitral surgery including excision of the left atrial appendage. Three hours after cardiopulmonary bypass, patients received either a 72-hour infusion of NES at 0.01 mcg/kg/min (n = 9) or placebo (n = 10). Diuresis, diuretics, time to extubation, oxygenation, ANP, and serum Endothelin-1 levels were measured. Nonparametric analysis with Mann-Whitney test was performed with SPSS (SPSS Inc., Chicago, IL, USA).

RESULTS

In both groups, postoperative ANP levels fell from baseline (NES 330 to 280 ng/mL and control 220 to 150 ng/mL). There were no significant differences in patients receiving NES compared to controls in diuresis (1.33 mL/kg/hour urine output NES vs. 1.68 mL/kg/hour controls, p = 0.14); furosemide dosage (0.04 mg/kg/hour NES vs. 0.04 mg/kg/hour controls, p = 0.08); time to extubation (17.5 hours NES vs. 19.5 control, p = 0.42) or PaO2/FiO2 ratio at 48 hours (NES 200 vs. 273 control, p > 0.05). Endothelin-1 levels were higher at baseline with NES but not at 1 and 72 hours after cardiopulmonary bypass (NES 3.1, 3.8, 2.9 pg/mL vs. control 1.85, 4.05, 2.75 pg/mL; p = 0.01, 0.77, 0.47).

CONCLUSIONS

This pilot study did not demonstrate additional diuresis with nesiritide in postoperative mitral/maze patients already following a loop diuretic protocol.

Efficacy and safety of right and left atrial ablations on the beating heart with irrigated bipolar radiofrequency energy: a long-term animal study

OBJECTIVE

The Cox maze procedure is the most effective surgical treatment for atrial fibrillation; however, its complexity has limited its clinical utility. The purpose of this study was to simplify the procedure by using an irrigated bipolar radiofrequency ablation device on the beating heart without cardiopulmonary bypass.

METHODS

Six domestic pigs underwent median sternotomy. The pulmonary veins were circumferentially ablated. Electrical isolation was confirmed by pacing. Eight lesions were performed epicardially, and three lesions were performed through purse-string sutures with one of the jaws of the device introduced into the right atrium. After 30 days, magnetic resonance imaging was performed to assess atrial function, pulmonary vein anatomy, and coronary artery patency. Cholinergic stimulation and burst pacing were administered to induce atrial fibrillation. Histologic assessment of the heart was performed after the animal was killed.

RESULTS

A modified Cox maze procedure was successfully performed with the irrigated bipolar radiofrequency device with no deaths. In every instance, the pulmonary veins were electrically isolated. Cholinergic stimulation with burst pacing failed to produce atrial fibrillation. Imaging studies revealed tricuspid regurgitation without evidence of pulmonary vein stenosis, coronary artery stenosis, or intra-atrial thrombus. Total atrial ejection fraction was 16.9% +/- 7.5%, a significant reduction. Histologically, 99% of the lesions were transmural, and there was no evidence of coronary sinus injury.

CONCLUSION

Lesions on both the right and left atria can be created successfully on the beating heart with irrigated bipolar radiofrequency. The great majority of lesions with this device were transmural. This device should not be used on valvular tissue.

Left Atrial Appendage Occlusion Study (LAAOS): results of a randomized controlled pilot study of left atrial appendage occlusion during coronary bypass surgery in patients at risk for stroke

AIM

This pilot study assessed the safety and efficacy of left atrial appendage (LAA) occlusion, performed at the time of coronary artery bypass grafting (CABG).

METHODS AND RESULTS

At the time of CABG, 77 patients with risk factors for stroke were randomized to LAA occlusion or control. The LAA was occluded using sutures or a stapling device. Completeness of occlusion was assessed with transesophageal echocardiography. There were no significant differences in cardiopulmonary bypass duration, perioperative heart failure, atrial fibrillation, or bleeding between the 2 groups. During surgery, there were 9 appendage tears, all of which were repaired easily with sutures. Among patients having a postoperative transesophageal echocardiography, complete occlusion of the LAA was achieved in 45% (5/11) of cases using sutures and in 72% (24/33) using a stapler, P = .14. The rate of LAA occlusion by individual surgeons increased from 43% (9/21) to 87% (20/23) after performing 4 cases (P = .0001). After a mean follow-up of 13 +/- 7 months, 2.6% of patients had thromboembolic events.

CONCLUSIONS

LAA occlusion at the time of CABG is safe. The rate of complete occlusion improves, to acceptable levels, with increased experience and the use of a stapling device. A large trial is needed to determine if LAA occlusion prevents stroke.

Atrial reduction plasty Cox maze procedure: extended indications for atrial fibrillation surgery

BACKGROUND

The Cox maze procedure yields good results for atrial fibrillation (AF). However, patients with predictors of failure-chronic long-standing AF, low amplitude fibrillatory waves, and large left atriums-are generally thought not to benefit from a maze procedure. We report an aggressive approach for these patients, utilizing biatrial reduction plasty concomitantly with the Cox maze procedure for AF.

METHODS

A complete Cox maze procedure utilizing supplemental RF ablation was performed in 36 patients. All underwent resection of both atrial appendages and biatrial reduction plasty encompassing resection of the left atrial posterior wall from left to right pulmonary veins and from inferior pulmonary veins to the mitral annulus, as well as removal of the right atrial lateral wall. Mitral or tricuspid valve repair, or both, was performed on 32 patients.

RESULTS

These patients had a mean AF duration of 45 +/- 89 months. Their preoperative left atria measured 66 +/- 16 mm, with mean AF waves of 0.74 +/- 0.3 mm. Mean preoperative New York Heart Association class was 2.7 +/- 0.7 and left ventricular ejection fraction was 48 +/- 9. Cross clamp and bypass times were 91 +/- 35 minutes and 124 +/- 33 minutes, respectively. The average posterior left atrial tissue resected was 5.4 x 2.1 cm, and mean resected atrial weight was 10.3 +/- 2 g. There were no deaths and length of stay was 5.5 +/- 2 days. At a follow-up time of 19 +/- 16 months, 32 of the 36 patients were in normal sinus rhythm and New York Heart Association class I.

CONCLUSIONS

Aggressive biatrial reduction plasty Cox maze procedure was effective in 89% of these "low success" AF patients. This simple procedure can extend utilization of the Cox maze procedure to more patients with chronic AF.

Improved neurohormonal markers of ventricular function after restoring sinus rhythm by the Maze procedure

BACKGROUND

Clinical results of the Maze procedure for treatment of atrial fibrillation (AF) are excellent, suggesting improved ventricular function after restoring sinus rhythm. However, long-term corresponding effects on the release of cardiac natriuretic peptides and other vasoactive hormones are incompletely investigated after isolated Maze surgery.

METHODS

Plasma levels of brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP), antidiuretic hormone, aldosterone, and angiotensin II were measured in 15 patients (mean age, 52 +/- 11 years) undergoing isolated surgical Maze (III) procedures for medically refractory AF, preoperatively and 6 months postoperatively. At the time of blood sampling, hemodynamic correlates were obtained at baseline and after 6 and 12 minutes of rapid ventricular pacing at 150 stimulations/minute.

RESULTS

All patients were free of AF at 6-month follow-up. The measured plasma levels of BNP, ANP, and angiotensin II were all significantly lower (p = 0.03) late after the isolated Maze procedure. Cardiac output was significantly higher postoperatively (p < 0.01). Other hemodynamic values and left atrial size were unchanged after surgery. Ventricular pacing caused almost identical hemodynamic changes in atrial pressures before and late after surgery, but the associated plasma ANP response was significantly attenuated postoperatively (p < 0.001).

CONCLUSIONS

Levels of cardiac natriuretic peptides and angiotensin II as markers of ventricular function are improved in the long term after clinically successful isolated Maze procedures. ANP response to hemodynamic challenge by ventricular pacing was attenuated postoperatively, possibly due to atrial scarring.

Plasma atrial natriuretic peptide concentration inversely correlates with left atrial collagen volume fraction in patients with atrial fibrillation: plasma ANP as a possible biochemical marker to predict the outcome of the maze procedure

OBJECTIVES

We hypothesized that the plasma atrial natriuretic peptide (ANP) level reflects atrial degenerative change and may predict the outcome of the maze procedure.

BACKGROUND

Although a larger preoperative left atrial dimension and longer duration of atrial fibrillation (AF) have been reported in patients with persistent AF than in those with sinus rhythm (SR), these individual factors were not enough to predict the outcome of the maze procedure.

METHODS

Preoperative plasma ANP levels were measured in consecutive 62 patients who underwent the Kosakai's modified maze procedure. Moreover, we performed histological and molecular biological examinations in the resected left atrial tissues.

RESULTS

The preoperative plasma ANP was lower in the AF group (n = 13) than it was in the SR group (n = 49) (p < 0.001). Multiple logistic regression analysis revealed that duration of AF and plasma ANP were independently associated with postoperative cardiac rhythm. Among 41 patients with a higher plasma ANP or shorter duration of AF than the median value, SR was restored in 95% of patients. In contrast, in 21 patients with a lower plasma ANP and a longer duration of AF than the median value, SR was restored only in 48% of patients. Histological examination revealed that the collagen volume in the left atrial tissue was higher in AF than it was in SR and inversely correlated with plasma ANP. In addition, the messenger RNA expressions of ANP, collagen type I and type III were lower in AF than they were in SR.

CONCLUSIONS

These results suggest that a combination of plasma ANP and/or duration of AF may predict the success rate for the maze operation. Advanced atrial degenerative change may result in a decrease of atrial ANP secretion.

A new procedure for chronic atrial fibrillation: bilateral appendage-preserving maze procedure

BACKGROUND

Atrial transport and atrial natriuretic peptide secretion is severely reduced from normal after the maze III procedure. To improve these factors, we developed a bilateral appendage-preserving maze procedure (BAP-maze).

METHODS

Forty-six patients with chronic atrial fibrillation who underwent the BAP-maze procedure were compared with 40 patients who underwent the maze III procedure. The ratio of the peak velocity of the A and E waves of transmitral flow (transthoracic pulsed Doppler echocardiography), the left atrial appendage ejection fraction (transesophageal echocardiography), and the atrial natriuretic peptide secretory reserve during treadmill exercise test were measured at 6 months postoperatively.

RESULTS

Sinus rhythm was restored in 44 patients (95.7%) by the BAP-maze procedure and in 39 patients (97.5%) by the maze III procedure. The ratio of the peak velocity of the A and E waves was 0.52 +/- 0.22 in the BAP-maze group and 0.25 +/- 0.19 in the maze III group (p < 0.0001). The left atrial appendage ejection fraction was 44.7% +/- 11.5%, and the atrial natriuretic peptide secretory reserve was greater in the BAP maze group (p = 0.037).

CONCLUSIONS

The BAP-maze procedure improved atrial transport and atrial natriuretic peptide secretion as well as simplifying the maze operation, without decreasing its effectiveness against atrial fibrillation.