Intraoperative TEE during mitral valve repair: does it predict early and late postoperative mitral valve dysfunction?

Comparison of post-operative transesophageal and transthoracic echocardiogram findings following atrioventricular septal defect repair

Success of atrioventricular septal defect repair is defined by post-operative atrioventricular valve function and presence of residual intracardiac shunting. We evaluated differences in interpretation of atrioventricular valve function and residual defects between transesophageal and transthoracic echocardiography in a contemporary cohort of infants undergoing atrioventricular septal defect repair. Among 106 patients, we identified an increase in left and right atrioventricular valve regurgitation, right atrioventricular valve inflow gradient, and increased detection rate of residual intracardiac shunting on transthoracic compared to transesophageal echocardiograms, although residual shunts identified only on transthoracic echocardiogram were not haemodynamically significant. Findings may help inform expectation of post-operative transthoracic echocardiogram findings based on intraoperative assessment.

Every day mitral valve reconstruction: What has changed over the last 15 years?

OBJECTIVE

Mitral valve reconstruction (MVR) is one of the cardiosurgical procedures which cannot be substituted by any intervention owing to the quality of the quasi-anatomical, physiological repair. However, technique and strategies have changed over the years. We looked at procedural characteristics and outcome in an all-comer, non-selected cohort of patients.

METHODS

738 out of 1.977 patients were retrospectively analyzed receiving MVR with and without concomitant procedures. The cohort was divided into three periods. P1: 2004-2009 (134 pts.); P2: 2010-2014 (294 pts.), and P3: 2015-2019 (310 pts.).

RESULTS

Early mortality increased from P1 to P2 and decreased from P2 to P3 (9% P1, 13% P2, 10% P3). All patients received an annuloplasty-ring. In P1 resection measures dominated. In P3 artificial chordae were dominant. Age, BMI, and risk scores correlated with early mortality. Survival rates were 66% (5-years), 55% (10-years), 44% (15-years) in P1, 63% (5-years), 50% (10-years) in P2, and 80% (5-years) in P3. Odds ratio for reduced long-term survival were concomitant venous only bypass surgery (10-years 2,701, p = 0.026). 10-year survival was positively influenced by isolated MVR (0.246, p = 0.001), concomitant isolated arterial bypass (IMA) (0.153, p = 0.051), posterior leaflet measure (0.178, p<0.001), and use of artificial chordae (5-years 0.235, p<0.001).

CONCLUSION

Indication for ring implantation remained mandatory while preference changed alongside improved designs. Procedural characteristics changed from mainly resection maneuvers to predominant use of artificial chordae. Long-term results were negatively influenced by co-morbidities and positively influenced by posterior leaflet repair and artificial chordae. MVR underwent a qualitative evolution and remains a valuable cardiosurgical procedure.

Immediate Post-Procedural and Discharge Assessment of Mitral Valve Function Following Transcatheter Edge-to-Edge Mitral Valve Repair: Correlation and Association with Outcomes

The correlation between residual mitral regurgitation (rMR) grade or mitral valve pressure gradient (MVPG), at transcatheter edge-to-edge mitral valve repair (TEEMr) completion and at discharge, is unknown. Furthermore, there is disagreement regarding rMR grade or MVPG from which prognosis diverts. We retrospectively studied 82 patients that underwent TEEMr. We tested the correlation between rMR or MVPG and evaluated their association, with outcomes. Moderate or less rMR (rMR ≤ 2) at TEEMr completion was associated with improved survival, whereas mild or less rMR (rMR ≤ 1) was not. Patients with rMR ≤ 1 at discharge demonstrated a longer time of survival, of first heart failure hospitalization and of both. The correlation for both rMR grade (r = 0.5, p < 0.001) and MVPG (r = 0.51, p < 0.001), between TEEMr completion and discharge, was moderate. MR ≤ 2 at TMEER completion was the strongest predictor for survival (HR 0.08, p < 0.001) whereas rMR ≤ 1 at discharge was independently associated with a lower risk of the combined endpoint (HR 4.17, p = 0.012). MVPG was not associated with adverse events. We conclude that the assessments for rMR grade and MVPG, at the completion of TEEMr and at discharge, should be distinctly reported. Improved outcome is expected with rMR ≤ 2 at TEEMr completion and rMR ≤ 1 at discharge. Higher MVPG is not associated with unfavorable outcomes.

2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

This executive summary of the valvular heart disease guideline provides recommendations for clinicians to diagnose and manage valvular heart disease as well as supporting documentation to encourage their use.

METHODS

A comprehensive literature search was conducted from January 1, 2010, to March 1, 2020, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, Cochrane, Agency for Healthcare Research and Quality Reports, and other selected database relevant to this guideline. Structure: Many recommendations from the earlier valvular heart disease guidelines have been updated with new evidence and provides newer options for diagnosis and treatment of valvular heart disease. This summary includes only the recommendations from the full guideline which focus on diagnostic work-up, the timing and choice of surgical and catheter interventions, and recommendations for medical therapy. The reader is referred to the full guideline for graphical flow charts, text, and tables with additional details about the rationale for and implementation of each recommendation, and the evidence tables detailing the data considered in developing these guidelines.

Durability of mitral valve repair: A single center experience

Background

This study aims to present clinical outcomes of mitral valve repair in patients with different etiologies.

Methods

Between June 2006 and August 2017, a total of 421 consecutive patients (266 males, 155 females; mean age 53.1±15.6 years; range, 5 to 89 years) who underwent mitral valve repair with or without concomitant cardiac procedures were retrospectively analyzed. All pre-, intra-, and postoperative data were collected. Echocardiographic examinations were performed at discharge and during follow-up. Kaplan-Meier analysis was used to estimate overall survival and from residual severe mitral regurgitation, endocarditis and reoperation-free survival rates.

Results

The mean follow-up was 58.9±35.1 months. Of the patients, 12 (2.8%) had previous cardiac operations. The most predominant pathology was degenerative disease in 265 patients (62.9%). Repair techniques included ring annuloplasty (n=366, 86.9%), artificial chordae implantation (n=185, 44%), and commissurotomy (n=38, 9%). Overall in-hospital mortality rate was 1.2% (n=5). Echocardiography before discharge showed no/trivial mitral regurgitation in 64.9% (n=270) and mild mitral regurgitation in 34.85% (n=145) of the patients. At the late postoperative period, transthoracic echocardiography revealed moderate mitral regurgitation in 23 patients (5.7%) and severe in 11 patients (2.7%). The mean late survival and freedom from endocarditis, reoperation, and recurrent severe mitral regurgitation rates were 92±0.03%, 98.5±0.07%, 98.1±0.01%, and 94.7±0.02%, respectively.

Conclusion

Our study results suggest that mitral valve repair is a safe and effective procedure associated with favorable longterm outcomes in experienced centers.

A Comparison of the Degree of Residual Mitral Regurgitation by Intraoperative Transoesophageal and Follow-up Transthoracic Echocardiography following Mitral Valvuloplasty

Patients who undergo mitral valve repair for mitral regurgitation and have mild residual mitral regurgitation may have an increased risk of re-operation in future years. Intraoperative transoesophageal echocardiography has now become a standard of practice for mitral valve repair surgery. We identified 106 patients who underwent attempted mitral valve repair over a three-year period in our institution. We retrospectively reviewed the grade of residual mitral regurgitation assigned following successful mitral valve repair (‘mild’ or less residual regurgitation) by intraoperative transoesophageal echocardiography and compared it to the observed grade of mitral regurgitation seen at follow-up transthoracic echocardiography. No patient had unexpected moderate or severe mitral regurgitation postoperatively, suggesting that intraoperative transoesophageal echocardiography performed in a medium-sized department is a sensitive tool for the early detection of failed mitral repair. Mild residual mitral regurgitation on intraoperative transoesophageal echocardiography was not reliably associated with mild mitral regurgitation on follow-up transthoracic echocardiography. In fact, 61% of patients with mild mitral regurgitation identified by intraoperative transoesophageal echocardiography had reduced mitral regurgitation at follow-up transthoracic echocardiography (to nil/trace residual mitral regurgitation). This observation, in conjunction with the limitations of the data supporting the goal of ‘echo perfect’ repair, suggests that a second attempt at repair should not be made based on the intraoperative transoesophageal echocardiography finding of mild residual mitral regurgitation alone.

Residual Mitral Regurgitation After Repair for Posterior Leaflet Prolapse-Importance of Preoperative Anterior Leaflet Tethering

Background

Carpentier's techniques for degenerative posterior mitral leaflet prolapse have been established with excellent long‐term results reported. However, residual mitral regurgitation (MR) occasionally occurs even after a straightforward repair, though the involved mechanisms are not fully understood. We sought to identify specific preoperative echocardiographic findings associated with residual MR after a posterior mitral leaflet repair.

Methods and Results

We retrospectively studied 117 consecutive patients who underwent a primary mitral valve repair for isolated posterior mitral leaflet prolapse including a preoperative 3‐dimensional transesophageal echocardiography examination. Twelve had residual MR after the initial repair, of whom 7 required a corrective second pump run, 4 underwent conversion to mitral valve replacement, and 1 developed moderate MR within 1 month. Their preoperative parameters were compared with those of 105 patients who had an uneventful mitral valve repair. There were no hospital deaths. Multivariate analysis identified preoperative anterior mitral leaflet tethering angle as a significant predictor for residual MR (odds ratio, 6.82; 95% confidence interval, 1.8–33.8; P=0.0049). Receiver operator characteristics curve analysis revealed a cut‐off value of 24.3° (area under the curve, 0.77), indicating that anterior mitral leaflet angle predicts residual MR. In multivariate regression analysis, smaller anteroposterior mitral annular diameter (P<0.001) and lower left ventricular ejection fraction (P=0.002) were significantly associated with higher anterior mitral leaflet angle, whereas left ventricular and left atrial dimension had no significant correlation.

Conclusions

Anterior mitral leaflet tethering in cases of posterior mitral leaflet prolapse has an adverse impact on early results following mitral valve repair. The findings of preoperative 3‐dimensional transesophageal echocardiography are important for consideration of a careful surgical strategy.

Anatomical features of acute mitral valve repair dysfunction: Additional value of three-dimensional echocardiography

Recurrence of mitral regurgitation after mitral valve repair is correlated with unfavourable left ventricular remodelling and poor outcome. This pictorial review describes the echocardiographic features of three types of acute mitral valve repair dysfunction, and the additional value of three-dimensional echocardiography.

Analysis of Recurrent Mitral Regurgitation after Mitral Valve Repair

Mitral valve repair was performed in 437 patients with mitral regurgitation from January 1994 to January 2002. The causes of mitral regurgitation were degenerative in 238 (54%), rheumatic in 134 (31%), and others in 65 (15%). The most frequently employed surgical techniques were ring annuloplasty in 417 (95%) cases, new chordae formation in 216 (50%), and quadrangular resection in 117 (27%). The mean follow-up was 29.04 ± 22.81 months. There were 5 (1.2%) early and 5 (1.2%) late deaths. The reoperation rate was 1.6% with 41 (9%) cases of recurrent mitral regurgitation. Of these 22 were procedure-related: incomplete repair in 13, discordant new chordal length in 7, suture dehiscence and leaflet perforation in 1 case each. There were 19 cases of valve related failures: progression of rheumatic disease in 18 and subacute infective endocarditis in 1. Valve-related failure strongly correlated with progression of rheumatic disease. As initial operative success was the prime determinant of repair durability, intraoperative repair assessment with transesophageal echocardiography was essential.

Lifting posterior mitral annuloplasty for enhancing leaflet coaptation in mitral valve repair: midterm outcomes

BACKGROUND

We evaluated the midterm outcomes of lifting posterior mitral annuloplasty for enhancing leaflet coaptation in mitral valve repair.

METHODS

Between October 2007 and December 2012, 341 consecutive patients with significant mitral regurgitation underwent lifting posterior mitral annuloplasty using a specially designed fabric annuloplasty strip that lifts the middle portion of the posterior annulus. Associated procedures for mitral valve repairs, such as patch valvuloplasty for posterior leaflet prolapse (n=80), new chord placement for anterior leaflet prolapse (n=33), commissurotomy (n=29), and posterior leaflet extension (n=23), were performed in 141 patients (41.3%).

RESULTS

Thirty-day mortality was 0.9%. Nine late deaths (2.6%) occurred. Mean overall survival at 5 years was 96.0%±1.1%. During the mean follow-up period of 38±17 months, six patients (1.8%) underwent valve-related reoperation (5-year freedom from valve-related reoperation, 98.1%±0.8%). At 5 years, mean freedom from recurrence of mitral regurgitation grade 3+ to 4+ (moderate to severe) was 95.1%±1.6%. The mean valve pressure gradient (PG) was 3.2±1.5 mmHg across all strip sizes at the time of follow-up.

CONCLUSIONS

Lifting posterior mitral annuloplasty using an innovative annuloplasty strip in mitral valve repair has a low rate of recurrent regurgitation or valve-related reoperation with rare relevant complications.

Leakage test during mitral valve repair

Mitral valve repair is the preferred surgical treatment for mitral regurgitation. Cardiac surgeons must increasingly pursue high-quality mitral valve repair, which ensures excellent long-term outcomes. Intraoperative assessment of a competency of the repaired mitral valve before closure of the atrium is an important step in accomplishing successful mitral valve repair. Saline test is the most simple and popular method to evaluate the repaired valve. In addition, an "Ink test" can provide confirmation of the surface of coaptation, which is often insufficient in the assessment of saline test. There are sometimes differences between the findings of the leakage test in an arrested heart and the echocardiographic findings after surgery. Assessment of the mitral valve in an arrested heart may not accurately reflect its function in a contractile heart. Assessment of the valve on the beating heart induced by antegrade or retrograde coronary artery perfusion can provide a more physiological assessment of the repaired valve. Perfusion techniques during beating heart surgery mainly include antegrade coronary artery perfusion without aortic cross-clamping, and retrograde coronary artery perfusion via the coronary sinus with aortic cross-clamping. It is the most important point for the former approach to avoid air embolism with such precaution as CO2 insufflation, left ventricular venting, and transesophageal echocardiography, and for the latter approach to maintain high perfusion flow rate of coronary sinus and adequate venting. Leakage test during mitral valve repair increasingly takes an important role in successful mitral valve reconstruction.

Ischemic mitral regurgitation: pathophysiology, diagnosis and surgical treatment

Ischemic mitral valve regurgitation often complicates acute myocardial infarction and also represents a negative prognostic factor for long-term survival in patients undergoing surgical myocardial revascularization. While severe mitral regurgitation should always be corrected during a coronary artery bypass operation, the decision making is more difficult in patients with a mild-to-moderate degree of regurgitation. Recent studies and experimental protocols have elucidated the pathophysiological mechanisms leading to mitral regurgitation with great interest in annular modifications and subvalvular alterations. These data suggest that new and integrated surgical approaches that address annuloplasty ring sizing, ring type selection and tethering phenomenon (i.e., chordal cutting, 'edge-to-edge' technique and left-ventricular plasty techniques) are required for a safer and durable valve repair. Transthoracic and transesophageal echocardiography are useful in determining the etiology and the degree of mitral regurgitation, to assess mitral deformation and to measure indexes of global and regional left-ventricular remodeling. Stress echocardiography may unmask higher degrees of mitral regurgitation. More data are needed in order to confirm the promising and interesting preliminary experimental findings of magnetic resonance imaging in diagnosis and clinical evaluation of ischemic mitral regurgitation.

Improvement of mitral valve coaptation with supraannular plication of the posterior annulus--a newly designed strip for posterior annular plication--

PURPOSE

The aim of this study was to evaluate a newly-designed mitral annuloplasty strip (the Mitra-Lift(®) strip) in patients undergoing mitral valve repair for mitral regurgitation (MR).

METHODS

A total of 30 patients who underwent posterior mitral strip annuloplasty for moderately severe to severe MR were evaluated in this study. The strip annuloplasty (SA) consisted of the use of the newly-designed strip and the suture of the supra-annular atrial wall of 5.0 mm width and the posterior annulus. In addition to SA, six patients (20.0%) with tethered posterior leaflets required posterior leaflet augmentation. Improvement in MR and hemodynamic parameters of the valve with the fixed strip were assessed.

RESULTS

After SA, all patients exhibited little or no MR, with no individual exhibiting signs of exacerbation during the follow-up period. A stable coaptation occurred below the strip and the posterior annulus due to forward movement and lifting of the posterior annulus without significant reduction of intercommissural dimension. During the cardiac cycle, the intercommissural dimensions showed considerable changes, which meant a dynamic motion of the anterior leaflet and the commissures.

CONCLUSIONS

Formation of a stable leaflet coaptation was associated with a dynamic change of the intercommissural dimension during the cardiac cycle and resulted in a reliable, annuloplasty strip, representing a new concept in annuloplasty.

Intraoperative echocardiography in valvular heart disease: an evidence-based appraisal

Intraoperative (IO) transesophageal echocardiography (TEE) is widely used for assessing the results of valvular heart disease (VHD) surgery. Epiaortic ultrasonography (EAU) has been recommended for prevention of perioperative strokes. To what extent does high-quality evidence justify the widespread use of these imaging modalities? In March 2009, we searched MEDLINE (PubMed and OVID interfaces) and EMBASE for studies published in English using database-specific controlled vocabulary describing the concepts of IOTEE, cardiac surgery, VHD, and EAU. We found no randomized trials or studies with control groups assessing the impact of IOTEE in VHD surgery. Pooled analysis of 8 observational studies including 15,540 patients showed an average incidence of 11% for prebypass surgical changes and 4% for second pump runs, suggesting that patients undergoing VHD surgery may benefit significantly from IOTEE, particularly from postcardiopulmonary bypass IOTEE in aortic repair and mitral repair and replacement, but less so in isolated aortic replacement. Further available indirect evidence was satisfactory in the test accuracy and surgical quality control aspects, with low complication rates for IOTEE. The data supporting EAU included 12,687 patients in 2 prospective randomized studies and 4 nonrandomized, controlled studies, producing inconsistent outcome-related results. Despite low-quality scientific evidence supporting IOTEE in VHD surgery, we conclude that indirect evidence supporting its use is satisfactory and suggests that IOTEE may offer considerable benefit in valvular repairs and mitral replacements. The value of IOTEE in isolated aortic valve replacement remains less clear. Evidence supporting EAU is scientifically more robust but conflicting. These findings have important clinical policy and research implications.

Discrepancy Between Intraoperative Transesophageal Echocardiography and Postoperative Transthoracic Echocardiography in Assessing Congenital Valve Surgery

BACKGROUND

The purpose of this study was to investigate the discrepancy between intraoperative transesophageal and postoperative transthoracic echocardiography in assessing residual regurgitation in children undergoing valve repair.

METHODS

Forty-two consecutive children (median age, 5.1 years) who underwent valve repair for valvar regurgitation from 2001 to 2004 were retrospectively analyzed. The patients were divided into two groups: atrioventricular valve group (n = 33) and aortic valve group (n = 9). Regurgitation grade, fractional shortening, and atrioventricular inflow velocity obtained by intraoperative transesophageal echocardiography were compared with those obtained by transthoracic echocardiography at discharge (median, 11 days) and at follow-up (median, 8 months).

RESULTS

Intraoperative transesophageal echocardiography revealed specific residual lesions in 4 patients, leading to successful re-repair. Fractional shortening obtained by intraoperative transesophageal echocardiography was lower than that obtained by predischarge transthoracic echocardiography (p < 0.01). In the atrioventricular valve group, the regurgitation grade obtained by intraoperative transesophageal echocardiography was lower than that obtained by predischarge transthoracic echocardiography (0.7 +/- 0.8 versus 1.4 +/- 0.9; p < 0.01), and agreement between the two examinations was found in 12 patients (38%). Peak atrioventricular inflow velocity obtained by intraoperative transesophageal echocardiography was lower than that obtained by predischarge transthoracic echocardiography (p < 0.01). In the aortic valve group, there was no significant difference between the regurgitation grades in the two examinations (0.8 +/- 0.8 versus 1.1 +/- 0.9), and complete agreement in regurgitation grade was found in 5 (56%) of 9 patients.

CONCLUSIONS

There were considerable discrepancies between the examinations in evaluation of residual atrioventricular valve regurgitation and potential atrioventricular valve stenosis: most of the residual regurgitations were underestimated by intraoperative transesophageal echocardiography. In contrast, reasonable agreement was found between the two examinations in evaluation of aortic valve regurgitation.

Tearing of the mitral valve during vent removal after a successful mitral valve repair: a beneficial role of transesophageal echocardiography

In this case, a successful mitral valve repair was confirmed by transesophageal echocardiography (TEE) at the end of a cardiopulmonary bypass. The left ventricular vent was placed through the mitral valve to remove the air after the TEE examination, and on its way out, the left ventricular vent damaged the anterior mitral leaflet (AML). Re-examination of the valve with TEE detected the new mitral valve insufficiency. The CPB was reinstituted, and tearing of the lateral third part of the anterior mitral leaflet was found. This case emphasizes the importance of TEE in the operating room as a continuous monitor, not only to evaluate the result of the cardiac surgery, but also to detect any unpredictable events during the surgery.

Mitral Valve Repair for Anterior Leaflet Prolapse With Expanded Polytetrafluoroethylene Sutures

BACKGROUND

This study was a long-term Doppler echocardiographic assessment of mitral valve repair for anterior mitral leaflet prolapse using expanded polytetrafluoroethylene sutures.

METHODS

Between April 1992 and December 2003, we performed mitral valve repair using expanded polytetrafluoroethylene sutures in 204 patients (mean age, 54.6 years) with severe mitral regurgitation (MR) having anterior mitral leaflet prolapse. The cause of valve disease was degenerative in 181 patients (88.7%). Postoperative serial transthoracic echocardiographic studies were performed in all hospital survivors. Residual MR flow detected by color Doppler echocardiography was classified according to the maximum regurgitant jet area.

RESULTS

The 30-day mortality of 204 patients was 1.4% (3 deaths). There were 12 late deaths and 14 reoperations in this series. Kaplan-Meier survival and freedom from reoperation at 12 years were 84.6% +/- 4.0% and 89.9% +/- 2.9%, respectively. Postoperative transthoracic echocardiographic assessment after discharge (mean follow-up, 4.2 +/- 3.0 years) showed less than mild regurgitation (maximum regurgitant jet area < 4.0 cm2) in 80.9% of the patients. Overall, freedom from severe MR (maximum regurgitant jet area > or = 7.0 cm2) estimates at 12 years were 88.1% +/- 3.1%. Freedom from severe MR at 12 years for 114 patients with no MR (maximum regurgitant jet area = 0 cm2) on intraoperative transesophageal echocardiography and 77 patients with MR was 95.3% +/- 2.1% and 82.9% +/- 5.1%, respectively (p = 0.033).

CONCLUSIONS

Twelve-year echocardiographic follow-up demonstrates good long-term results of chordal replacement with expanded polytetrafluoroethylene sutures for anterior mitral leaflet prolapse. To avoid recurrence of regurgitation, a significantly high level of competence of the valve is essential in the repair of anterior mitral leaflet prolapse.

Dynamic Quantitative Echocardiographic Evaluation of Mitral Regurgitation in the Operating Department

Hemodynamic modifications induced by general anesthesia could lead to underestimation of mitral regurgitation (MR) severity in the operating department and potentially serious consequences. The intraoperative severity of MR was prospectively compared with the preoperative baseline evaluation using dynamic quantitative transesophageal echocardiography in 25 patients who were stable with MR 2/4 or greater undergoing coronary bypass, mitral valve operation, or both. Significant changes in the severity of MR using transesophageal echocardiographic criteria occurred after the induction of general anesthesia and with phenylephrine. Quantitative transesophageal echocardiographic evaluation of MR using effective orifice area and vena contracta, and the use of phenylephrine challenge, were useful to avoid underestimating MR severity in the operating department.

Impact of preoperative and postoperative atrial fibrillation on outcome after mitral valvuloplasty for nonischemic mitral regurgitation

OBJECTIVE

We sought to determine the impact of preoperative or postoperative atrial fibrillation on survival, stroke, and cardiac function after mitral valvuloplasty for mitral regurgitation.

METHODS

Between 1991 and 2003, 1026 patients with nonischemic/noncardiomyopathy mitral valve regurgitation underwent mitral valve plasty in 3 centers; 663 patients remained in sinus rhythm (group A), and 363 patients had atrial fibrillation or flutter preoperatively (group B) with concomitant maze procedures (group BM, n = 163) or without maze procedures (group BN, n = 200).

RESULTS

Eight-year freedom from cardiovascular-related death was better in group A (99.3%) than group B (BM: 96.9%, BN: 81.6%) ( P < .001) and also better in group BM than group BN ( P = .007). The adjusted hazard ratio of group B versus group A for preoperative differences was 5.1 (95% confidence interval: 1.8-14.8). Eight-year freedom from stroke was better in group A (99.2%) than group B (BM: 98.2%, BN: 82.6%) ( P < .001) and also better in group BM than group BN ( P < .001). Patients with preoperative atrial fibrillation had larger left atria and left ventricular systolic dimensions. The adjunct maze procedure improved left ventricular systolic dimensions over mitral repair alone (group A vs B: P = .359; group BM vs BN: P = .001).

CONCLUSION

Preoperative permanent/persistent atrial fibrillation was associated with a dilated left atrium and reduced left ventricular function in patients with mitral regurgitation. Including the maze procedure with mitral repair improved survival, late cardiac function, and freedom from late stroke.

Transesophageal echocardiography

Anesthesiologists are increasingly using transesophageal echocardiography in both cardiac and noncardiac cases. In cardiac anesthesia, considerable progress has been made in the evaluation of mitral valvular disease. Transesophageal echocardiography has also become more useful in the hemodynamic evaluation of patients undergoing coronary artery bypass grafting. It is particularly valuable in minimally invasive surgery and in heart surgery to correct congenital defects.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.