Postoperative atrial fibrillation: The role of the inflammatory response.

OBJECTIVE: Abnormal atrial conduction has been shown to be a substrate for postoperative atrial fibrillation (POAF). This study aimed to determine the relationship between the location of the atrial reentry responsible for POAF, and degree of atrial inflammation. METHODS: Normal mongrel dogs (n = 18) were divided into 3 groups: anesthesia alone (anesthesia), lateral right atriotomy (atriotomy), and lateral right atriotomy with anti-inflammatory therapy (steroid). Conduction properties of the right and left atria (RA and LA) were examined 3 days postoperatively by mapping. Activation was observed during burst pacing-induced AF. The RA and LA myeloperoxidase activity was measured to quantitate the degree of inflammation. RESULTS: Sustained AF (>2 minutes) was induced in 5 of 6 animals in the atriotomy group, but in none in the anesthesia or steroid groups. All sustained AF originated from around the RA incision. Three of these animals had an incisional reentrant tachycardia around the right atriotomy and 2 had a focal activation arising from the RA during AF. The LA activations in these animals were passive from the RA activation. The RA activation of the atriotomy group was more inhomogeneous than that of the anesthesia group (inhomogeneity index: 2.0 ± 0.2 vs 1.0 ± 0.1, P < .01). Steroid therapy significantly normalized the RA activation after the atriotomy (1.2 ± 0.1, P < .01). The inhomogeneity of the atrial conduction correlated with the myeloperoxidase activity (r = 0.774, P < .001). CONCLUSIONS: Reentrant circuits responsible for POAF are dependent on the degree of inflammation and rotate around the atriotomy. Anti-inflammatory therapy decreased the risk of postoperative AF.

Performing the Left Atrial Maze Ablation Pattern Without Atriotomy.

The need to perform an additional atriotomy is a major concern that keeps many surgeons from performing an extended left atrial lesion set in patients with atrial fibrillation during procedures such as aortic valve replacement. This does result either in a suboptimal lesion set or even in ignoring the rhythm disorder, leaving the patient exposed to an increased risk of stroke and possible hemodynamic compromises. This report describes a technique how pulmonary vein isolation, an isolation of the posterior left atrial wall and an anterior mitral annular line, which substitutes for the mitral isthmus line in order to prevent perimitral atrial flutter, can be performed during aortic valve replacement without the need for an atriotomy. This technique allows for an optimal time management by minimizing additional cardiopulmonary bypass-time and cross-clamp-time; however, its equivalent efficacy in successfully treating atrial fibrillation compared to the left atrial Maze IV ablation pattern needs to be revealed in future trials.

Bipolar radiofrequency maze procedure through a transseptal approach.

We report how to perform a complete open-heart ablation with bipolar radiofrequency through a transseptal incision. The connecting left atrial lines were performed by inserting one jaw of the clamp through a stab wound in the posterior left atrium, beneath the right inferior pulmonary vein. Twenty-five patients underwent concomitant ablation with the described technique in three different centers. All the left lines were easily performed. No ablation-related complication occurred. At 11 +/- 6 months, 80% of the patients were free from arrhythmias.

Animal studies of epicardial atrial ablation.

The Cox maze procedure is an effective treatment of atrial fibrillation, with a long-term freedom from recurrence greater than 90%. The original procedure was highly invasive and required cardiopulmonary bypass. Modifications of the procedure that eliminate the need for cardiopulmonary bypass have been proposed, including use of alternative energy sources to replace cut-and-sew lesions with lines of ablation made from the epicardium on the beating heart. This has been challenging because atrial wall muscle thickness is extremely variable, and the muscle can be covered with an epicardial layer of fat. Moreover, the circulating intracavitary blood acts as a potential heat sink, making transmural lesions difficult to obtain. In this report, we summarize the use of nine different unidirectional devices (four radiofrequency, two microwave, two lasers, one cryothermic) for creating continuous transmural lines of ablation from the atrial epicardium in a porcine model. We define a unidirectional device as one in which all the energy is applied by a single transducer on a single heart surface. The maximum penetration of any device was 8.3 mm. All devices except one, the AtriCure Isolator pen, failed to penetrate 2 mm in some nontransmural sections. Future development of unidirectional energy sources should be directed at increasing the maximum depth and the consistency of penetration.

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.

Microwave ablation for atrial fibrillation: dose-response curves in the cardioplegia-arrested and beating heart.

BACKGROUND: Microwave ablation has been used to replace the traditional incisions used in the surgical treatment of atrial fibrillation. However, dose-response curves have not been established in surgically relevant models. The purpose of this study was to develop dose-response curves for the Flex 10 (Guidant, Inc) microwave device in both the acute cardioplegia-arrested heart and on the beating heart. METHODS: Twelve domestic pigs (40 to 45 kg) were subjected to microwave ablation in either the arrested (n = 6) or beating heart (n = 6). The cardioplegia-arrested heart was maintained at 10 degrees to 15 degrees C while six atrial endocardial and seven right ventricular epicardial lesions were created in each animal. On the beating heart, six right atrial and seven ventricular epicardial lesions were created. Ablations were performed for 15, 30, 45, 60, 90, 120, and 150 seconds (65 W, 2.45 GHz). The tissue was stained with 2,3,5-triphenyl-tetrazolium chloride, and sectioned at 5-mm intervals. Lesion depth and width were determined from digital micrographs. RESULTS: Mean atrial wall thickness was 2.8 mm (range, 1 to 8 mm). In the arrested heart, 94% of atrial lesions were transmural at 45 seconds and 100% were transmural at 90 seconds. In the beating heart, only 20% of atrial lesions were transmural despite prolonged ablation times (90 seconds). Ventricular lesion width and depth increased with duration of application, and were similar on the arrested and beating hearts. CONCLUSIONS: Microwave ablation produces linear dose-response curves. Transmural lesions can be reliably produced on the arrested heart, but not consistently on the beating heart.

Laser assistance for extraction of chronically implanted endocardial leads: infectious versus noninfectious indications.

BACKGROUND: Powered sheaths, including Excimer laser sheaths, were introduced for the removal of transvenous pacing and defibrillator leads. The purpose of this study was to develop an algorithm to better predict which patients are likely to benefit from these devices. METHODS: We reviewed 283 consecutive patients in whom a total of 500 leads (302 pacing and 198 defibrillator leads) were extracted over a 5-year period at our operative facilities. Laser assist was utilized whenever moderate traction failed. RESULTS: In 128 patients, 203 leads were removed for noninfectious indication. In 155 patients, 297 leads for infectious indications, including sepsis 22% (111), pocket infection 23% (115), and erosion 14% (71). Laser assistance was required for 6%+/- 5% (+/- 95% confidence interval) of septic leads, 51%+/- 7% of leads associated with erosion or pocket infection and 60%+/- 7% of noninfected leads (P = 0.001). Laser assistance was necessary more often for leads implanted >12 months (53%+/- 5%) than 12 months or less (6%+/- 5%) (P = 0.001) and for ventricular (52%+/- 6%) compared to atrial (35%+/- 7%) leads (P = 0.001). CONCLUSIONS: Chronically implanted leads (>12 months), especially noninfected leads and leads associated with erosion or pocket infection, should be referred for extraction with powered sheaths to ensure successful removal. However, leads that are associated with systemic sepsis can generally be removed without powered sheaths.

Right atrial and ventricular adaptation to chronic right ventricular pressure overload.

BACKGROUND: Increased mortality in patients with chronic pulmonary hypertension has been associated with elevated right atrial (RA) pressure. However, little is known about the effects of chronic right ventricular (RV) pressure overload on RA and RV dynamics or the adaptive response of the right atrium to maintain RV filling. METHODS AND RESULTS: In 7 dogs, RA and RV pressure and volume (conductance catheter) were recorded at baseline and after 3 months of progressive pulmonary artery banding. RA and RV elastance (contractility) and diastolic stiffness were calculated, and RA reservoir and conduit function were quantified as RA inflow with the tricuspid valve closed versus open, respectively. With chronic pulmonary artery banding, systolic RV pressure increased from 34+/-7 to 70+/-17 mm Hg (P<0.001), but cardiac output did not change (P>0.78). RV elastance and stiffness both increased (P<0.05), suggesting preserved systolic function but impaired diastolic function. In response, RA contractility improved (elastance increased from 0.28+/-0.12 to 0.44+/-0.13 mm Hg/mL; P<0.04), and the atrium became more distensible, as evidenced by increased reservoir function (49+/-14% versus 72+/-8%) and decreased conduit function (51+/-14% versus 28+/-8%; P<0.002). CONCLUSIONS: With chronic RV pressure overload, RV systolic function was preserved, but diastolic function was impaired. To compensate, RA contractility increased, and the atrium became more distensible to maintain filling of the stiffened ventricle. This compensatory response of the right atrium likely plays an important role in preventing clinical failure in chronic pulmonary hypertension.

Dose response curves for microwave ablation in the cardioplegia-arrested porcine heart.

INTRODUCTION: Microwave ablation has been used clinically for the surgical treatment of atrial fibrillation, particularly during valve procedures. However, dose- response curves have not been established for this surgical environment. The purpose of this study was to examine dosimetry curves for the Flex 4 and Flex 10 microwave devices in an acute cardioplegia-arrested porcine model. METHODS: Twelve domestic pigs (40-45 kg) were acutely subjected to Flex 4 (n = 6) and Flex 10 (n = 6) ablations. On a cardioplegically arrested heart maintained at 10-15(o)C, six endocardial atrial and seven epicardial ventricular lesions were created in each animal. Ablations were performed for 15 s, 30 s, 45 s, 60 s, 90 s, 120 s, and 150 s (65 W, 2.45 GHz). The tissue was stained with 2,3,5-triphenyl-tetrazolium chloride and lesions were sectioned at 5 mm intervals. Lesion depth and width were determined from digital photomicrographs of each lesion (resolution +/- .03 mm). RESULTS: Average atrial thickness was 2.88 +/- .4 mm (range 1.0 to 8.0 mm). 94% of ablated atrial sections created by the FLEX 4 (n = 16) and the FLEX 10 (n = 16) were transmural at 45 seconds. 100% of atrial sections were transmural at 90 seconds with the FLEX 10 (n = 14) and at 60 seconds with the Flex 4 device (n = 15). Lesion width and depth increased with duration of application. CONCLUSION: Both devices were capable of producing transmural lesions on the cardioplegically arrested heart at 65 W. These curves will allow surgeons to ensure transmural ablation by tailoring energy delivery to the specific atrial geometry.

Inflammation of atrium after cardiac surgery is associated with inhomogeneity of atrial conduction and atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is common after cardiac surgery. Abnormal conduction is an important substrate for AF. We hypothesized that atrial inflammation alters atrial conduction properties. METHODS AND RESULTS: Normal mongrel canines (n=24) were divided into 4 groups consisting of anesthesia alone (control group); pericardiotomy (pericardiotomy group); lateral right atriotomy (atriotomy group); and lateral right atriotomy with antiinflammatory therapy (methylprednisolone 2 mg/kg per day) (antiinflammatory group). Right atrial activation was examined 3 days after surgery. Inhomogeneity of conduction was quantified by the variation of maximum local activation phase difference. To initiate AF, burst pacing was performed. Myeloperoxidase activity and neutrophil cell infiltration in the atrial myocardium were measured to quantify the degree of inflammation. The inhomogeneity of atrial conduction of the atriotomy and pericardiotomy groups was higher than that of the control group (2.02+/-0.10, 1.51+/-0.03 versus 0.96+/-0.08, respectively; P<0.005). Antiinflammatory therapy decreased the inhomogeneity of atrial conduction after atriotomy (1.16+/-0.10; P<0.001). AF duration was longer in the atriotomy and pericardiotomy groups than in the control and antiinflammatory groups (P=0.012). There also were significant differences in myeloperoxidase activity between the atriotomy and pericardiotomy groups and the control group (0.72+/-0.09, 0.41+/-0.08 versus 0.18+/-0.03 DeltaOD/min per milligram protein, respectively; P<0.001). Myeloperoxidase activity of the antiinflammatory group was lower than that of the atriotomy group (0.17+/-0.02; P<0.001). Inhomogeneity of conduction correlated with myeloperoxidase activity (r=0.851, P<0.001). CONCLUSIONS: The degree of atrial inflammation was associated with a proportional increase in the inhomogeneity of atrial conduction and AF duration. This may be a factor in the pathogenesis of early postoperative AF. Antiinflammatory therapy has the potential to decrease the incidence of AF after cardiac surgery.

Surgical treatment of atrial fibrillation: predictors of late recurrence.

OBJECTIVE: The Cox maze procedure was introduced in 1987 for the treatment of atrial fibrillation. This study evaluated the predictors of late atrial fibrillation recurrence in 276 consecutive patients who underwent this procedure at our institution. METHODS: From 1987 through June 2003, 276 patients (79 female and 197 male patients; mean age, 55 +/- 11 years) underwent the Cox maze procedure. Thirty-three patients had Cox maze procedure I, 16 patients had Cox maze procedure II, and 197 patients had Cox maze procedure III. The last 30 patients underwent a modified procedure (Cox maze procedure IV) with bipolar radiofrequency ablation. There were 113 (41%) patients who had a concomitant operation, most commonly either a mitral valve procedure (19%) or coronary artery bypass grafting (20%). Data were analyzed by means of univariate analysis, with preoperative and perioperative variables used as covariates. Patient follow-up was conducted by means of questionnaire, physician examination, and electrocardiographic documentation. All patients had a minimum of 6 months of follow-up. RESULTS: Patient follow-up was achieved in 92.8% of cases, with a mean follow-up time of 5.8 +/- 3.6 years. Risk factors for late atrial fibrillation recurrence were duration of preoperative atrial fibrillation (P = .01) and Cox maze procedure version (P = .001). There was no difference in actuarial 10-year survival between the Cox maze procedure versions. CONCLUSION: The Cox maze procedure remains the gold standard for the treatment of atrial fibrillation and has excellent long-term efficacy. The most significant predictor of late recurrence was duration of preoperative atrial fibrillation, suggesting that earlier surgical intervention would further increase efficacy.

Reservoir and conduit function of right atrium: impact on right ventricular filling and cardiac output.

The purpose of this study was to investigate the relationship between right atrial (RA) reservoir and conduit function and to determine how hemodynamic changes influence this relationship and its impact on cardiac output. In 11 open-chest sheep, RA reservoir and conduit function were quantified as RA inflow with the tricuspid valve closed versus open, respectively. Conduit function was separated into early (before A wave) and late (after A wave) components. The effects of inotropic stimulation, partial pulmonary artery occlusion, and pericardiotomy were tested. At baseline with the pericardium intact, reservoir function accounted for 0.56 (SD 0.13) of RA inflow, early conduit for 0.29 (SD 0.07), and late conduit (during RA contraction) for 0.16 (SD 0.11). Inotropic stimulation decreased conduit function and increased reservoir function, but these effects did not reach statistical significance. With partial pulmonary artery occlusion, early conduit function fell to 0.20 (SD 0.11) (P < 0.04), and the conduit-to-reservoir ratio decreased by 41% (P < 0.03). Similarly, after pericardiotomy, early conduit function fell to 0.14 (SD 0.09) (P < 0.004), reservoir function increased to 0.72 (SD 0.08) (P < 0.04), and, consequently, the early conduit-to-reservoir ratio decreased by 63% (P < 0.006). Cardiac output was inversely related to the conduit-to-reservoir ratio (r = 0.39, P < 0.001). This study demonstrated that the right atrium adjusts its ability to act more as a reservoir than a conduit in a dynamic manner. The RA conduit-to-reservoir ratio was directly related to the right ventricular pressure-RA pressure gradient at the time of maximum RA volume, with increased ventricular pressures favoring conduit function, but it was inversely related to cardiac output, with an increase in the reservoir contribution favoring improved cardiac output.

A prospective multicenter trial of bipolar radiofrequency ablation for atrial fibrillation: early results.

BACKGROUND: The Cox-Maze III remains the gold standard for the surgical treatment of atrial fibrillation. However, the "cut-and-sew" technique is time consuming and technically challenging. The pulmonary veins are the source of ectopy in the majority of patients with atrial fibrillation. The safety and efficacy of bipolar radiofrequency to electrically isolate the pulmonary veins was evaluated in a prospective multi-center trial. METHODS: Beginning in January 2002, 30 patients at three medical centers underwent pulmonary vein isolation using bipolar radiofrequency and were followed for 6 months. Twenty-four of the patients also underwent a modified Cox-Maze III. Electrical isolation of the pulmonary veins was confirmed with intraoperative pacing. Pulmonary vein patency was assessed by magnetic resonance imaging or three-dimensional computed tomography in 15 patients at 1 month. RESULTS: Mean age was 60.9 +/- 11.7 years. Nineteen patients had paroxysmal atrial fibrillation. All pulmonary veins were isolated in every patient. The left pulmonary veins underwent 3.0 +/- 1.4 applications for a total of 26.4 +/- 10.5 seconds. The right pulmonary veins underwent 2.8 +/- 1.1 applications for a total of 26.3 +/- 12.6 seconds. There was no operative mortality. At 1 month, imaging revealed no evidence of pulmonary vein stenosis. At 6 months, 96% of patients were in normal sinus rhythm. CONCLUSIONS: The use of bipolar radiofrequency for electrical isolation of pulmonary veins and to replace other Cox-Maze III incisions is safe and effective at controlling atrial fibrillation. This emerging technology may shorten and simplify the surgical management of atrial fibrillation.

Successful performance of Cox-Maze procedure on beating heart using bipolar radiofrequency ablation: a feasibility study in animals.

BACKGROUND: The Cox-Maze procedure is the gold standard for the surgical treatment of atrial fibrillation with proven long-term efficacy. However, its application has been limited by its complexity and significant morbidity. The purpose of this study was to test the feasibility and safety of performing the Cox-Maze procedure using bipolar radiofrequency ablation on the beating heart without cardiopulmonary bypass. METHODS: After median sternotomy, 6 Hanford mini-pigs underwent a modified Cox-Maze procedure using bipolar radiofrequency energy. The animals survived for 30 days. Atrial function, coronary artery, pulmonary vein anatomy, and valve function were assessed by magnetic resonance imaging. At reoperation, pacing documented electrical isolation of the pulmonary veins. Induction of atrial fibrillation was attempted by burst pacing with cholinergic stimulation. Histologic assessment was performed after sacrifice. RESULTS: There were no perioperative mortalities or neurologic events. At 30 days, atrial fibrillation was unable to be induced, and pulmonary vein isolation was confirmed by pacing. Magnetic resonance imaging assessment revealed no coronary artery or pulmonary vein stenoses. Although atrial ejection fraction decreased slightly from 0.344 +/- 0.0114 to 0.300 +/- 0.055 (p = 0.18), atrial contractility was preserved in every animal. Histologic assessment showed all lesions to be transmural, and there were no significant stenoses of the coronary vessels or injuries to the valves. CONCLUSIONS: Virtually all of the lesions of the Cox-Maze procedure can be performed without cardiopulmonary bypass using bipolar radiofrequency energy. There were no late stenoses of the pulmonary veins. Clinical trials of this new technology on the beating heart are warranted.

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.

Donor heart preservation with pinacidil: the role of the mitochondrial K ATP channel.

BACKGROUND: Pinacidil solutions have been shown to have significant cardioprotective effects. Pinacidil activates both sarcolemmal and mitochondrial potassium-adenosine triphosphate (K(ATP)) channels. This study was undertaken to compare pinacidil solution with University of Wisconsin (UW) solution and to determine if the protective effect of pinacidil involved mitochondrial or sarcolemmal K(ATP) channels. METHODS: Thirty-two rabbit hearts received one of four preservation solutions in a Langendorff apparatus: (1) UW; (2) a solution containing 0.5 mmol/L pinacidil; (3) pinacidil with Hoechst-Marion-Roussel 1098 (HMR-1098), a sarcolemmal channel blocker; and (4) pinacidil with 5-hydroxydecanote, a mitochondrial channel blocker. Left ventricular pressure-volume curves were generated by an intraventricular balloon. All hearts were placed in cold storage for 8 hours, followed by 60 minutes of reperfusion. RESULTS: Postischemic developed pressure was better preserved by pinacidil than by UW. This cardioprotective effect was eliminated by 5-hydroxydecanote and diminished by HMR-1098. Diastolic compliance was better preserved by pinacidil when compared with UW. This protection was abolished by the addition of 5-hydroxydecanote and moderately decreased by HMR-1098. CONCLUSIONS: Our results support the superiority of pinacidil over UW after 8 hours of storage. The cardioprotective role of pinacidil is mediated primarily by the mitochondrial K(ATP) channel.

The long-term outcome of patients with coronary disease and atrial fibrillation undergoing the Cox maze procedure.

BACKGROUND: A significant number of patients presenting for coronary revascularization have chronic atrial fibrillation. Although the Cox maze III procedure is the gold standard for the surgical treatment of this arrhythmia, few of these patients undergo atrial fibrillation operations at the time of their coronary bypass grafting. This study examined the long-term outcome of patients with ischemic heart disease who underwent the Cox maze procedure at our institution. METHODS: From 1990 to 2002, 47 patients undergoing operations for ischemic heart disease underwent a concomitant Cox maze III procedure. All patients underwent coronary bypass grafting, and 7 (15%) patients underwent coronary bypass grafting plus a mitral valve repair. Follow-up was performed by means of mail and telephone questionnaires with both the patients and their cardiologists. All patients who had any history of arrhythmia or who were taking medications had their rhythm documented by electrocardiogram. RESULTS: The mean age of these patients was 62 +/- 8 years, with a marked male predominance (45 men and 2 women). Twenty-eight (60%) of the patients had paroxysmal atrial fibrillation, and the remainder had persistent arrhythmias. The mean duration of atrial fibrillation was 7.6 +/- 6.5 years. The operative mortality in this series was 2%. Nine (19%) patients required postoperative pacemakers. At last follow-up (mean of 5.7 +/- 3.3 years), 98% of patients were free of atrial fibrillation. CONCLUSION: The Cox maze III procedure has a low operative mortality and excellent long-term efficacy in patients with ischemic heart disease. These data suggest a more widespread use of this procedure in these patients.

Impact of pericardial restraint on right atrial mechanics during acute right ventricular pressure load.

Optimization of right atrial (RA) mechanics is important for maintaining right ventricular (RV) filling and global cardiac output. However, the impact of pericardial restraint on RA function and the compensatory role of the right atrium to changes in RV afterload remain poorly characterized. In eight open-chest sheep, RA elastance (contractility) and chamber stiffness were measured (RA pressure-volume relations) at baseline and during partial pulmonary artery (PA) occlusion. Data were collected before and after pericardiotomy. With the pericardium intact and partial PA occlusion, RA elastance increased by 28% (P < 0.04), whereas RA stiffness tended to rise (P = 0.08). However, after pericardiotomy, there was a significant fall in both RA elastance (54%, P < 0.04) and stiffness (39%, P < 0.04), and subsequent PA occlusion failed to induce a change in elastance (P > 0.19) or stiffness (P > 0.84). After pericardiotomy, RA elastance and stiffness fell dramatically, and the compensatory response of the right atrium to elevated RV afterload was lost. The ability of the right atrium to respond to changes in RV hemodynamics is highly dependent on pericardial integrity.