Cumulative sum failure analysis of a policy change from on-pump to off-pump coronary artery bypass grafting

Learning curve of mitral valve repair: cumulative sum failure analysis from single high-volume center

Background

Mitral valve (MV) repair has become the gold standard for treating degenerative mitral regurgitation (MR), yet the success rate of MV repair is still low in clinical practice. While studies focused on the learning process of MV repair are scarce, fully understanding the learning curve could provide valuable information for education and the quality control of MV repair, thus benefiting patients. This observational study aimed to evaluate the learning process and performances of individual surgeon for MV repair for degenerative mitral disease using data from a single high-volume center.

Methods

Profiles of patients who underwent MV repair for degenerative MR at our institution from January 2003 to December 2016 were analyzed retrospectively. Overall and individual learning curves for the repair rate and major adverse events were calculated using sequential probability cumulative sum failure analysis. Average learning curves for major adverse events and operative time were also analyzed, by calculating the average incidence of adverse events and operative time of all operations stratified by accumulated operation numbers of individual surgeon. Altogether, we evaluated 2,482 operations performed by 14 surgeons.

Results

There was an obvious learning curve for the repair rate at the institution and individual surgeon levels. Altogether, 50 to 200 operations were needed to overcome the repair rate learning curve, yet wide variation was observed among individual surgeons. The learning process for individual surgeons became faster after the turning point in the institutional learning curve appeared. No obvious learning curve was observed at the institution or individual level for major adverse events and in-hospital mortality.

Conclusions

The number of cases required to overcome the learning curve for repair rate is substantial, although there is marked variation among surgeons. Individuals’ learning curves accelerate as the institution accumulates experience. MV repair is safe in experienced high-volume center. Close monitoring is necessary when surgeons begin to practice new techniques.

Quantifying the learning curve of emergent total arch replacement in acute type A aortic dissection

Background

Acute type A aortic dissection with arch involvement is a life-threatening condition, which requires immediate surgical attention. Emergent total arch replacement and root reconstruction is a technically demanding operation with varying outcomes based on surgeon experience. The human factors in total arch replacement in the emergent setting have never been systematically investigated. The ability of surgeons with low volumes to achieve acceptable results in their start-up period is not known.

Methods

From January 2013 to December 2016, patients with acute type A aortic dissection who underwent emergent total arch replacement with three surgeons were enrolled. Basic characteristics, procedural and postoperative outcomes were collected. The time of critical surgical steps and operative mortality were calculated using descriptive statistics and cumulative SUM (CUSUM) analysis.

Results

A total of 300 patients (age 53.8±11.5 years, female 63, 21.0%) with acute type A aortic dissection underwent emergent total arch replacement. A total of 219 patients (73.0%) had root reinforcement, 295 patients (98.3%) underwent frozen elephant trunk repair. Mean circulatory arrest and cross-clamp times were 29.8±9.8 and 112.3±32.1 min, respectively. The operative mortality was 6.7%, the stroke rate was 4.0%. The mean length of postoperative ICU and hospital stays were 8.4±10.6 and 18.0±12.2 days, respectively. By CUSUM depictions, surgeons appeared to have different learning curves with regards to operative time. By CUSUM failure analysis on operative mortality, two newly appointed surgeons in their start-up period stayed in an acceptable range, while one senior surgeon with higher volumes experienced superior outcomes and better performance.

Conclusions

Although emergent total arch replacement for acute type A dissection is a complex scenario, surgeons well-trained in adult cardiac surgery are able to achieve acceptable results in their start-up period.

Cumulative sum analysis of the learning curve for the preclosure technique using Proglide

OBJECTIVES

Our study aims to assess the technical quality and the learning curve of the preclosure technique for a vascular surgeon using Proglide using cumulative sum analysis (CUSUM analysis).

METHODS

This study was designed retrospectively and enrolled 81 consecutive patients with 88 access sites who underwent endovascular aortic repair or thoracic endovascular aortic repair with the preclosure technique using Proglide between July 2017 and February 2018. The patients were divided into 2 groups chronologically: (A) the first 40 cases and (B) the latter 41 cases. Logistic regression analysis was used to assess the impact of technical risk factors on the success of the preclosure technique, and the χ2 test and 1-way ANOVA were applied to analyse the distribution of individual characteristics and risk factors between the 2 groups. CUSUM analysis was adapted to analyse the learning curve and to monitor the technical quality, with a predetermined target failure rate of 5%, an alternative failure rate of 20% and calculated 80% 'alert', 95% 'alarm' and 80% 'reassurance' lines.

RESULTS

Primary technical success was obtained in 81 (92.05%) access sites. There were no significant correlations between primary technical success and risk factors, including, common femoral artery diameter (P = 0.88), common femoral artery depth from the skin (P =0.94), the level of common femoral artery calcification (P =0.86) and size of sheath (P =0.96). Moreover, the distribution of related risk factors was not significantly different between groups A and B. CUSUM analysis showed that the cumulative failure rate never crossed the 80% 'alert' and 95% 'alarm' lines. Additionally, the failure rate began to approach the 80% 'reassurance' line after ∼22 cases and crossed the 80% 'reassurance' line after 36 cases.

CONCLUSIONS

The technique of totally percutaneous access using Proglide is safe and effective for an experienced vascular surgeon, even if the operator has no previous experience with any preclosure techniques. CUSUM analysis showed that 36 cases are necessary to achieve the target failure rate of 5%.

Six-year single-centre experience in minimally invasive mitral valve repair - impact of the team learning curve on in-hospital clinical outcome

Introduction

Minimally invasive mitral repair is less traumatic and more acceptable for the patient than traditional surgery. However, it is a challenging procedure that requires effort from all the personnel involved.

Aim

To investigate the results of the minimally invasive mitral valve repair learning curve at the institution.

Material and methods

The indication for the surgery was severe mitral regurgitation. Patients with other valvular insufficiency, body mass index (BMI) > 30 kg/m², ejection fraction (EF) < 45%, aortic dilatation, reoperation, pleural adhesions, coronary artery disease requiring invasive treatment, and pregnant women were disqualified. The patients were assigned to one of three groups regarding their surgery date – group 1 (2012–2013), group 2 (2014–2015) and group 3 (2016–2017). The primary endpoints were death, myocardial infarction, stroke, an reoperation for mitral dysfunction. The investigation was performed to determine preoperative parameters (EuroSCORE, age, sex, BMI, arrhythmias, EF), intraoperative parameters (procedure, cross-clamp, extracorporeal circulation), and postoperative parameters (chest revision, transfusion, drainage, ventilation time, pleurocentesis, hospitalization time).

Results

There were 173 patients in total. One patient from group 1 (0.6% overall) died. No myocardial infarction or stroke was observed in any of the three groups. Chest revision count (5 vs. 1 vs. 1; p = 0.0004), total drainage (797.20 vs. 517.92 vs. 449.69; p = 0.0018) and hospitalization time (7.89 vs. 7.18 vs. 6.73; p = 0.0005) were significantly different among the groups. The ventilation time, transfusion number and pleurocentesis count did not differ significantly.

Conclusions

The procedure is safe and ensures optimal perioperative results. The number of complications is low and acceptable.

Cardiac-Referenced Leukocyte Telomere Length and Outcomes After Cardiovascular Surgery

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Short leukocyte telomeres have been associated with adverse cardiovascular outcomes in population studies, but this relationship has not translated to patient care. The authors report a telomere length autologous referencing strategy that has the potential to mark biological aging and to identify high-risk individuals.

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Among 163 patients who underwent cardiovascular surgery, telomeres in leukocytes and skeletal muscle displayed age-related shortening, whereas the telomere length in the cardiac right atrium was stable during 6 decades of life.

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The magnitude of the telomere length gap between cardiac atrial tissue and leukocytes was associated with post-operative complications and length of stay in the intensive care unit.

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This study provided proof of concept that a single-time, internally referenced assessment of leukocyte telomere shortening behavior could inform acute risks in patients with cardiovascular disease.

Leukocyte telomere shortening reflects stress burdens and has been associated with cardiac events. However, the patient-specific clinical value of telomere assessment remains unknown. Moreover, telomere shortening cannot be inferred from a single telomere length assessment. The authors investigated and developed a novel strategy for gauging leukocyte telomere shortening using autologous cardiac atrial referencing. Using multitissue assessments from 163 patients who underwent cardiovascular surgery, we determined that the cardiac atrium-leukocyte telomere length difference predicted post-operative complexity. This constituted the first evidence that a single-time assessment of telomere dynamics might be salient to acute cardiac care.

Myocardial revascularization without extracorporeal circulation; Why hasn't it convinced yet?

Extracorporeal circulation has led to a great development in cardiovascular surgery during the last five decades. Its time-proven efficacy and safety have made on-pump coronary artery bypass grafting (CABG) the gold standard method of surgical revascularization. However, coronary revascularization on cardiopulmonary bypass and the accompanying aortic manipulation are related to plenty of deleterious complications. Therefore, off-pump CABG surgery was established to avoid complications. Nevertheless, despite the initial enthusiasm on this technique, only 20% of myocardial revascularization procedures worldwide are performed off-pump. Not only are off-pump cardiac procedures more technically difficult but also they do not provide better results in terms of graft patency, completeness of revascularization, repeat revascularization requirement, cost, and quality of life. Completeness of revascularization and anastomotic quality should not be compromised to avoid cardiopulmonary bypass.

Off-Pump Surgery: A Choice in Unstable Angina

The benefit and safety of off-pump coronary artery bypass surgery in patients with unstable angina was assessed retrospectively. From February 1996 to October 2001, 5,306 patients underwent multivessel off-pump coronary artery bypass, of whom 920 (17%) had unstable angina. In these 920 patients, ejection fractions ranged from 15% to 70%, 203 (22%) had an ejection fraction of 20%–35%, and 11 (1%) had an ejection fraction < 20%. Triple-vessel disease was present in 625 patients. Preoperative intraaortic balloon pump support was used in 28 patients. Operative approaches included mid sternotomy (86%), lower partial sternotomy (9%), and left anterior thoracotomy (2%). The number of grafts ranged from 1 to 5 with a mean of 2.43 ± 0.86, and 92.3% of patients received a left internal mammary artery graft. Twenty-two patients need intraoperative intraaortic balloon pumping. Ten patients (1%) suffered perioperative myocardial infarction. The mean hospital stay was 7.8 ± 4.3 days. Hospital mortality was 2/920 (0.22%). Intraaortic balloon pumping was helpful in these cases of unstable angina refractory to medical therapy. Off-pump coronary artery surgery was found to be safe and beneficial in these patients.

Use of graphical statistical process control tools to monitor and improve outcomes in cardiac surgery

BACKGROUND

Graphical Statistical Process Control (SPC) tools have been shown to promptly identify significant variations in clinical outcomes in a range of health care settings. We explored the application of these techniques to qualitatively inform the routine cardiac surgical morbidity and mortality (M&M) review process at a single site.

METHODS

Baseline clinical and procedural data relating to 4774 consecutive cardiac surgical procedures, performed between the 1st January 2003 and the 30th April 2011, were retrospectively evaluated. A range of appropriate performance measures and benchmarks were developed and evaluated using a combination of CUmulative SUM (CUSUM) charts, Exponentially Weighted Moving Average (EWMA) charts and Funnel Plots. Charts have been discussed at the unit's routine M&M meetings. Risk adjustment (RA) based on EuroSCORE has been incorporated into the charts to improve performance.

RESULTS

Discrete and aggregated measures, including Blood Product/Reoperation, major acute post-procedural complications and Length of Stay/Readmission<28 days have proved to be usable measures for monitoring outcomes. Monitoring trends in minor morbidities provides a valuable warning of impending changes in significant events. Instances of variation in performance have been examined and could be related to differences in individual operator performance via individual operator curves.

CONCLUSION

SPC tools facilitate near "real-time" performance monitoring allowing early detection and intervention in altered performance. Careful interpretation of charts for group and individual operators has proven helpful in detecting and differentiating systemic vs. individual variation.

Cardiac displacement-induced hemodynamic instability during off-pump coronary artery bypass surgery and its predictors

BACKGROUND

Emergent conversion to an on-pump procedure during an off-pump coronary artery bypass surgery (OPCAB) due to hemodynamic instability is associated with increased morbidity and mortality. The aim of this study was to evaluate the predictors of hemodynamic instability associated with mechanical heart displacement during OPCAB and the fate of these patients.

METHODS

Data of 494 patients who underwent elective, isolated OPCAB between December 2006 and April 2010 were reviewed. Hemodynamic instability was defined as mixed venous oxygen saturation (SvO(2) ) <60% during grafting. Pre-operative variables including the presence of diastolic dysfunction and mitral regurgitation (MR) were evaluated for their predictive value for hemodynamic instability by logistic regression analysis. Outcome variables were also compared between patients who developed hemodynamic instability and those who did not.

RESULTS

In univariate analysis, body mass index, diabetes mellitus, chronic obstructive pulmonary disease (COPD), left ventricular ejection fraction, diastolic dysfunction, MR ≥ grade 1, higher creatinine and the use of diuretics were identified as risk factors. In multivariate analysis of these variables, COPD and creatinine remained as independent risk factors for hemodynamic instability. These patients also had significantly lower cardiac output and SvO(2) after sternum closure and a higher incidence of composite morbidity end points.

CONCLUSION

COPD and pre-operative creatinine level were identified as independent risk factors of mechanical heart displacement-induced hemodynamic instability during OPCAB. As these patients were associated with significantly lower SvO(2) even at the end of surgery and with adverse outcome, consideration may be given to initiate preemptive measures to increase SvO(2) before or during grafting.

A risk-adjusted CUSUM in continuous time based on the Cox model

In clinical practice, it is often important to monitor the outcomes associated with participating facilities. In organ transplantation, for example, it is important to monitor and assess the outcomes of the transplants performed at the participating centers and send a signal if a significant upward trend in the failure rates is detected. In manufacturing and process control contexts, the cumulative summation (CUSUM) technique has been used as a sequential monitoring scheme for some time. More recently, the CUSUM has also been suggested for use in medical contexts. In this article, we outline a risk-adjusted CUSUM procedure based on the Cox model for a failure time outcome. Theoretical approximations to the average run length are obtained for this new proposal and for some discrete time procedures suggested in the literature. The proposed scheme and approximations are evaluated in simulations and illustrated on transplant facility data from the Scientific Registry of Transplant Recipients.

Cumulative sum failure analysis for eight surgeons performing minimally invasive direct coronary artery bypass

OBJECTIVE

Analysis of average and individual surgical performance for minimally invasive direct coronary artery bypass was used to enhance quality control for that operation.

METHODS

A total of 1441 standard minimally invasive direct coronary artery bypass procedures performed from August 1996 to January 2006 were analyzed for mortality and 10 other major perioperative complications. Learning curves and assessment of perioperative outcome were calculated using descriptive statistics and cumulative sum observed minus expected failure analysis for 8 involved surgeons with a personal experience ranging from 27 to 443 procedures.

RESULTS

The incidence of in-hospital mortality was 0.9% and compared favorably with the predicted mortality calculated by the logistic EuroSCORE (3.6%, P < .01). Cumulative sum analysis revealed that 2 surgeons crossed the 95% reassurance boundary after 50 operations and that 2 surgeons crossed the 95% reassurance boundary after 100 operations. There were significant differences between surgeons with regard to the learning curves and perioperative complications (3.6%-29.6%, P < .01). Two surgeons crossed the 95% alarm-line indicating unacceptably high failure rates.

CONCLUSIONS

Minimally invasive direct coronary artery bypass has become a procedure with low mortality and low complication rates, but results are case-load and surgeon dependent. Cumulative sum analysis is a valuable method allowing for a breakdown of complication rates over time displaying individual surgeons' strengths.

Impact of the opening of a specialized cardiac surgery recovery unit on postoperative outcomes in an academic health sciences centre

PURPOSE

It is controversial as to whether cardiac surgery patients are optimally managed in a mixed medical-surgical intensive care unit (ICU) or in a specialized postoperative unit. We conducted a prospective cohort study in an academic health sciences centre to compare outcomes before and following the opening of a specialized cardiac surgery recovery unit (CSRU) in April 2005.

METHODS

The study cohort included 2,599 consecutive patients undergoing coronary artery bypass grafting (CABG), valve and combined CABG-valve procedures from April 2004 to March 2006. From April 2004 to March 2005 (year 1) all patients received postoperative care in mixed medical-surgical ICUs at two different sites staffed by critical care consultants, fellows and residents. From April 2005 until March 2006 (year 2) patients were cared for in a newly-established CSRU on one site staffed by cardiac anesthesiology fellows, a nurse practitioner and consultants in critical care, cardiac anesthesiology and cardiac surgery. The effect of this change on in-hospital mortality, the incidence of ten major postoperative complications, postoperative ventilation hours, readmission rates and case cancellations due to a lack of capacity was assessed using Chi-square or Wilcoxon tests, where appropriate.

RESULTS

Coronary artery bypass grafting, valve and combined CABG-valve mortality rates were similar in years 1 and 2. There was a significant reduction in the composite major complication rate (16.3% to 13.0%, P=0.02) and in median postoperative ventilation hours (8.8 vs 8.0 hr, P=0.005) from year 1 to 2. On multivariable logistic regression analysis, the pre-merger interval (year 1) was a significant independent predictor of the occurrence of death or major complications.

CONCLUSION

A specialized CSRU with a multi-disciplinary consultant model was associated with stable or improved outcomes postoperatively, when compared to a mixed medical- surgical ICU model of cardiac surgical care.

Quality control of surgical and interventional procedures: a review of the CUSUM

BACKGROUND

The report of the CUSUM across surgical and interventional procedures has spawned a fair confusion in the literature.

AIM

To assess the use of the CUSUM and to clarify its utilisation in the perspective of future studies. Nature of the study: Retrospective review.

METHODS

A systematic literature search of Medline was carried out. From each article, data regarding the design of the study, the specialty, the performance criterion, the unit under control, the methodology and the model of the CUSUM used, the use of a graph, the use of a test and the type of test applied were retrieved.

RESULTS

31 studies were found relevant. The design was mainly retrospective for the analysis of the learning curve. The main performance criteria under control were morbidity, mortality and success of the procedure. A graph was plotted in all studies as a CUSUM plot or as cumulative sums of non-negative values. A test was used in 17 studies. Mislabelling of the plot and the test, and misuse of control limits were the most commonly reported mistakes.

CONCLUSION

The CUSUM tool is not yet properly reported in the surgical literature. Therefore, reporting of the CUSUM should be clarified and standardised before its use widens.

Improved survival after introduction of an emergency endovascular therapy protocol for ruptured abdominal aortic aneurysms

BACKGROUND

The study was conducted to demonstrate improved survival (30-day mortality) after the introduction of an emergency endovascular therapy protocol for ruptured abdominal aortic aneurysms (rAAA). Numerous authors have successfully demonstrated reduced mortality in patients with rAAA using endovascular techniques. Comparison of endovascular aneurysm repair (EVAR) with open repair for rAAA may be misleading, however, because EVAR cannot be performed on all patients, and selection bias may explain the superior performance of any given surgical or endovascular strategy. We developed a model to predict mortality in patients before the introduction of EVAR (preprotocol population), applied this model to predict 30-day mortality among prospective patients (postprotocol population), and compared observed vs expected results.

METHODS

We assessed 126 patients with rAAA. Primary outcome was 30-day mortality. Potential confounding variables were age, sex, presurgical lowest recorded systolic blood pressure (SBP), and glomerular filtration rate (GFR). A logistic regression model incorporating significant confounders was used to evaluate changes in 30-day mortality for all patients with rAAA after introduction of the EVAR protocol. Separate logistic regressions were done to compare 30-day mortality for preprotocol vs patients receiving EVAR and preprotocol vs patients receiving postprotocol open repair. Cumulative sum (CUSUM) analysis was used to assess shifts in the performance of the rAAA program over time.

RESULTS

Significant confounders were SBP, absence of SBP, and GFR. Logistic regression found evidence of lower mortality after the protocol was introduced, 17.9% vs 30.0% (odds ratio [OR], 0.385; 95% confidence interval [CI], 0.141 to 0.981; P = .046). Comparison of all open repairs (preprotocol and postprotocol) and EVAR demonstrated decreased risk for EVAR of 5.0% vs 28.3% (OR, 0.109; 95% CI, 0.013 to 0.906; P = .0084). Unstable patients (SBP <or=80) showed a trend towards improved survival with EVAR relative to open repair (14.3% vs 56.0%, P = .061). Comparison of preprotocol surgery with open repair after the introduction of the protocol found no evidence of a difference between mortality rates for the open procedures-30.0% (preprotocol) vs 25.0% (postprotocol; OR, 0.688; 95% CI, 0.335 to 1.415, P = .3031)-demonstrating that the improved performance observed with CUSUM analysis was related to the introduction of the EVAR protocol.

CONCLUSION

Our predictive model using "weighted" CUSUM analysis (a measure of performance over time) demonstrated that a predefined strategy of management of rAAA that includes EVAR is associated with improved (P < .05) mortality. Unstable patients with rAAA may be particularly benefited by EVAR and should not be excluded from repair. Appropriate patients with rAAA who are undergoing treatment in experienced vascular centers should be offered EVAR as the treatment of choice.

Off-pump coronary artery bypass graft surgery is standard of care: where do you stand?

The cardiopulmonary bypass (CPB) has allowed the establishment of coronary artery bypass graft surgery (CABG) to be a safe and effective treatment for patients with ischemic heart disease. However, the concern that CPB may be responsible for CABG-related morbidity has been raised, and it has been suggested that CABG itself would be safer without CPB. The development of commercially available cardiac stabilization devices resulted in several large, nonrandomized retrospective case series. The studies demonstrated that CABG can be performed safely without CPB (off-pump surgery), and suggested that there are benefits compared with conventional CABG. However, the randomized controlled studies published to date have been, as a whole, unable to conclusively demonstrate advantages of off-pump CABG. The results of these randomized studies are likely responsible for the failure of off-pump CABG to become established as the standard of care.

Off-pump CABG with synchronized arterial flow ensuring system

PURPOSE

We developed a synchronized, arterial-flow, ensuring system to perform coronary anastomoses safely without any ischemia-related event.

DESCRIPTION

Arterial blood is removed from the femoral artery. The resulting blood passes a switching valve and is pumped out to a syringe pump. This pump controller provides pulsatile arterial blood flow synchronized with the diastolic phase on an electrocardiogram. The arterial blood is perfused to the coronary artery through a fine flexible cannula during anastomosis.

EVALUATION

From February 1999, 524 consecutive patients were operated on using the synchronized arterial flow ensuring system. Mean duration for each anastomosis was 7.6 +/- 3.3 minutes (range, 4 to 20 min). There were no intraoperative fatal arrhythmias, ventricular arrhythmias, or short-run or hemodynamic deterioration during anastomoses. No hospital death was observed, and postoperative myocardial infarction occurred in 2 patients (0.4%). Postoperative angiography showed a 98.1% patency rate.

CONCLUSIONS

The early clinical and angiographical results for off-pump CABG with the synchronized arterial flow ensuring system were excellent without mortality. We believe that off-pump CABG can be more safely performed using the synchronized arterial flow ensuring system based on our favorable results.

Acquiring proficiency in off-pump surgery: traversing the learning curve, reproducibility, and quality control

As the risk profile of patients considered for surgical revascularization worsens, the cumulative benefit of off-pump coronary artery bypass (OPCAB) over conventional coronary artery bypass grafting, in terms of lower morbidity and reduced healthcare costs, may increase. There is still resistance to the introduction of OPCAB surgery however, its practice is variable and surgical residents are rarely trained in these techniques. This article considers how the learning curve in OPCAB may be negotiated and prospectively monitored to ensure quality control. The evidence suggests that situations in which suitable senior expertise exists, OPCAB surgery can be introduced into surgical practice and safely taught to trainees without detriment to patients. This is achieved by a progressive increase in the complexity of the case mix and careful early supervision. The introduction of OPCAB has coincided with the increasing use of control charts as quality control tools. Performance monitoring provides reassurance that patients are not being put at risk during the introduction of OPCAB; control chart methods can be used prospectively for real time performance monitoring by consultant surgeons and residents alike. These techniques may ultimately be used to determine proficiency and accreditation. Increasing use of parallel training techniques, the development of structured training programs that encompass OPCAB and other new technologies in cardiac surgery, coupled with objective performance monitoring are warranted to meet the needs of a changing patient population.

Direct comparison of risk-adjusted and non–risk-adjusted CUSUM analyses of coronary artery bypass surgery outcomes

OBJECTIVE

We previously applied non-risk-adjusted cumulative sum methods to analyze coronary bypass outcomes. The objective of this study was to assess the incremental advantage of risk-adjusted cumulative sum methods in this setting.

METHODS

Prospective data were collected in 793 consecutive patients who underwent coronary bypass grafting performed by a single surgeon during a period of 5 years. The composite occurrence of an "adverse outcome" included mortality or any of 10 major complications. An institutional logistic regression model for adverse outcome was developed by using 2608 contemporaneous patients undergoing coronary bypass. The predicted risk of adverse outcome in each of the surgeon's 793 patients was then calculated. A risk-adjusted cumulative sum curve was then generated after specifying control limits and odds ratio. This risk-adjusted curve was compared with the non-risk-adjusted cumulative sum curve, and the clinical significance of this difference was assessed.

RESULTS

The surgeon's adverse outcome rate was 96 of 793 (12.1%) versus 270 of 1815 (14.9%) for all the other institution's surgeons combined (P = .06). The non-risk-adjusted curve reached below the lower control limit, signifying excellent outcomes between cases 164 and 313, 323 and 407, and 667 and 793, but transgressed the upper limit between cases 461 and 478. The risk-adjusted cumulative sum curve never transgressed the upper control limit, signifying that cases preceding and including 461 to 478 were at an increased predicted risk. Furthermore, if the risk-adjusted cumulative sum curve was reset to zero whenever a control limit was reached, it still signaled a decrease in adverse outcome at 166, 653, and 782 cases.

CONCLUSIONS

Risk-adjusted cumulative sum techniques provide incremental advantages over non-risk-adjusted methods by not signaling a decrement in performance when preoperative patient risk is high.

Transplant center quality assessment using a continuously updatable, risk-adjusted technique (CUSUM)

Access to timely, risk-adjusted measures of transplant center outcomes is crucial for program quality improvement. The cumulative summation technique (CUSUM) has been proposed as a sensitive tool to detect persistent, clinically relevant changes in transplant center performance over time. Scientific Registry of Transplant Recipients data for adult kidney and liver transplants (1/97 to 12/01) were examined using logistic regression models to predict risk of graft failure (kidney) and death (liver) at 1 year. Risk-adjusted CUSUM charts were constructed for each center and compared with results from the semi-annual method of the Organ Procurement and Transplantation Network (OPTN). Transplant centers (N = 258) performed 59 650 kidney transplants, with a 9.2% 1-year graft failure rate. The CUSUM method identified centers with a period of significantly improving (N = 92) or declining (N = 52) performance. Transplant centers (N = 114) performed 18 277 liver transplants, with a 13.9% 1-year mortality rate. The CUSUM method demonstrated improving performance at 48 centers and declining performance at 24 centers. The CUSUM technique also identified the majority of centers flagged by the current OPTN method (20/22 kidney and 8/11 liver). CUSUM monitoring may be a useful technique for quality improvement, allowing center directors to identify clinically important, risk-adjusted changes in transplant center outcome.

Learning curve of coronary surgery by a cardiac surgeon in Japan with the use of cumulative sum analysis

OBJECTIVE

Case-volume has been believed to be of paramount importance in becoming a good cardiac surgeon. However, for a training cardiac surgeon there is no evidence regarding the specific number of necessary cases to attain the medico-legally acceptable level. We attempted to observe the learning curve in performing coronary surgery with the use of the cumulative sum (CUSUM) method to provide some evidence.

METHODS

From April 2000 to March 2004, a cardiac surgeon, being board-certified but not being on the attending staff, performed 50 coronary artery bypass grafting (CABG) under supervision of three different chief attending surgeons at three different hospitals. His learning curve was analyzed with the use of CUSUM. Mortality and morbidity and the average time of crossclamp and operation at each hospital were examined. Also, the learning curve of 100 left internal mammary artery (LIMA) harvestings were analyzed via CUSUM in terms of harvesting time and injury rate.

RESULTS

The CUSUM curve tended to come closer to the alert line (0.80 confidence) until the 23rd case, but never reached the alert line thereafter until the 50th case. The CUSUM curve never transgressed the alarm line (0.95 confidence) throughout 50 cases. The CUSUM curve of LIMA harvesting approached the alert line in the 38th case and the 59th case, but thereafter never reached the alert line and remained below the reassurance line from the 73rd case.

CONCLUSION

Tentatively, it is inferred that approximately 23 cases of CABG may be sufficient to allow for independent practice and that 73 cases of LIMA harvesting are sufficient to allow independent practice.

Off-pump coronary artery bypass graft surgery: where should we stand?

Coronary artery bypass grafting (CABG) performed with cardiopulmonary bypass has become a well-established treatment modality for patients with coronary artery disease. However, there is increasing evidence that cardiopulmonary bypass may be responsible for some of the morbidity associated with CABG surgery. Thus, it has been proposed that CABG surgery would be safer if cardiopulmonary bypass could be avoided. The development of cardiac stabilization devices has allowed for the creation of safe and reproducible coronary anastomoses on the beating heart. Several large, non-randomized, retrospective case series have demonstrated that CABG surgery can be performed safely without cardiopulmonary bypass (off-pump) and have in fact suggested benefits when compared with conventional CABG. However, the randomized controlled studies published to date have, as a whole, been unable to conclusively demonstrate the advantages of off-pump surgery. Taken together, the evidence to date suggests that a large-scale, prospective, randomized trial may be required to resolve the dilemma.

A cumulative analysis of an individual surgeon's early experience with elective open abdominal aortic aneurysm repair

BACKGROUND

Several studies have reviewed the role of hospital and surgeon case volumes in determining early mortality after elective open abdominal aortic aneurysm (AAA) repair. Few, however, have analyzed this relationship at the individual surgeon level. The purpose of this study was to display the usefulness of a unique statistical tool as a form of an ongoing practice audit.

METHODS

All patients who underwent an elective open AAA repair by an individual surgeon at a university-affiliated medical center over a 5-year period were analyzed. The cumulative sum failure method was used to analyze the results over time. Failure was defined as the presence of early mortality, myocardial infarction, or a complication resulting in another surgical procedure or prolonged hospitalization. A target failure rate of 10% was chosen, and 80% alert and 95% alarm boundary lines were established.

RESULTS

One hundred thirty-eight patients underwent elective AAA repair by this surgeon over a 5-year period (1998-2003). There were 5 early mortalities (3.6%), 15 myocardial infarctions (10.9%), and 3 major morbidities (2.2%). These results were plotted on a cumulative sum curve as an example of an ongoing practice audit.

CONCLUSIONS

The cumulative sum failure method provides a tool whereby a surgeon can prospectively audit his practice and recognize trends in performance before their recognition by standard statistical tools.

Monitoring the performance of residents during training in off-pump coronary surgery

OBJECTIVE

Control charts (eg, cumulative sum charts) plot changes in performance with time and can alert a surgeon to suboptimal performance. They were used to compare performance of off-pump coronary artery bypass surgery between a consultant and four resident surgeons and to compare performance of off-pump coronary artery bypass surgery and conventional coronary artery bypass grafting within surgeons.

METHODS

Data were analyzed for consecutive patients undergoing coronary artery bypass grafting who were operated on by one consultant or one of four residents. Conversions were analyzed by intention to treat. Perioperative death or one or more of 10 adverse events constituted failure. Predicted risks of failure for individual patients were derived from the study population. Variable life-adjusted displays and risk-adjusted sequential probability ratio test charts were plotted.

RESULTS

Data for 1372 patients were analyzed; 769 of the procedures were off-pump coronary artery bypass operations (56.0%). The consultant operated on 382 patients (293 off-pump, 76.7%), and the residents operated on 990 (474 off-pump, 47.9%). Patients operated on by residents tended to be older, more obese, more likely to require an urgent operation, and more likely to need a circumflex artery graft but less likely to have triple-vessel disease. There were 7 conversions (consultant 5, residents 2). The overall failure rate was 8.5% (9.2% for consultant's operations and 8.2% for residents' operations), including 10 deaths (0.7%). Predicted and observed risks of failure were similar for all five surgeons. After 100 off-pump coronary artery bypass operations, performance was the same or better for the residents as for the consultant. For all surgeons, performance was the same or better for off-pump as for conventional coronary artery bypass grafting.

CONCLUSIONS

Off-pump coronary artery bypass surgery can be safely taught to cardiothoracic residents. Implementation of continuous performance monitoring for residents is practicable.

Does technical failure of revascularization during coronary artery bypass grafting predict severity of poststernotomy mediastinitis?

BACKGROUND AND AIMS

To assess the impact of unsuccessful revascularization in relation to poststernotomy mediastinitis (PSM), which affects long-term outcome after coronary artery bypass grafting (CABG).

MATERIAL AND METHODS

An active approach for the follow-up of PSM involved a step by step treatment protocol of conventional surgery and plastic reconstructive surgery. 47 patients treated for PSM after CABG were identified and further evaluated. Complete revascularization was considered unsuccessful when technical hazards were reported during CABG. When PSM subsided after thorough debridement and sternal refixation without plastic reconstructive surgery, such as omentoplasty or muscle transposition, PSM was categorized as mild PSM. If treatment required plastic reconstructive surgery, PSM was categorized as severe PSM. Preoperative coronary artery angiographic status and success of revascularization were compared to postoperative outcome in relation to mild and severe PSM.

RESULTS

36 patients suffered from mild PSM and 11 patients from severe PSM. Preoperative clinical status did not differ among patients. Two patients (4.3 %) died during hospitalization. The need for plastic reconstructive surgery was significant (p < 0.05) among patients with unsuccessful revascularization. 35 out of 41 patients (85 %) without problems of graft anastomosis during CABG (successful revascularization) were associated with mild PSM, whereas only 6 out of 41 patients (15 %) with successful revascularization during CABG required plastic reconstructive surgery (p < 0.05). Technical failure of graft anastomosis (3 cases) or poor outflow of internal thoracic artery (2 cases) were statistically associated with severe PSM.

CONCLUSION

Technical failures of revascularization during CABG may delay recovery from PSM.

Off-pump versus on-pump coronary artery bypass surgery: does the pump influence outcome?1 1No competing interests declared

BACKGROUND

This study assessed hospitalization outcome differences for patients undergoing off-pump coronary artery bypass (OPCAB) grafting compared with patients having coronary artery bypass grafting with cardiopulmonary bypass.

STUDY DESIGN

We conducted a nested case-control study from an 8-year, hospitalization cohort (n = 7,905) in which the data were collected prospectively. Inclusion criteria included a coronary artery bypass graft only and age greater than 18 years. Cases were patients undergoing OPCAB (n = 360) and controls were patients undergoing coronary artery bypass grafting with cardiopulmonary bypass (n = 1,080). Cases were matched to controls 1:3 on five variables: age (+/- 3 years), gender, diabetes, New York Heart Association Functional Classification, and surgical year (+/- 3 years). The 13 outcomes of interest were mortality, length of hospitalization, ICU length of stay, return to ICU, ventilator time, intraoperative complications, pulmonary complications, neurologic complications, renal complications, gastrointestinal complications, sternal wound infections, highest postoperative creatine kinase level, and units of blood products given during the procedure. Using logistic regression we controlled for eight confounding variables.

RESULTS

Patients undergoing OPCAB had a significantly shorter length of hospitalization (relative risk [RR] = 0.95; 95% CI, 0.91-0.99%), fewer pulmonary complications (RR = 0.45; 95% CI, 0.22-0.88%), fewer intraoperative complications (RR = 0.04; 95% CI, 0.0048-0.31%) fewer blood product units given (RR = 0.31; 95% CI, 0.14-0.42%) and lower postoperative creatine kinase (RR = 0.99; 95% CI, 0.98-0.99%). There were no considerable differences for the remaining nine outcomes, including mortality and neurologic complications.

CONCLUSIONS

Patients undergoing OPCAB had a considerably shorter length of hospitalization, had fewer pulmonary and intraoperative complications, and received a lower volume of blood products.

Cumulative sum failure analysis of the learning curve with endovascular abdominal aortic aneurysm repair

PURPOSE

The purpose of this study was to evaluate the importance of experience and the learning curve with endovascular abdominal aortic aneurysm (AAA) repair.

METHODS

A retrospective analysis was performed of all elective endovascular AAA repairs attempted by an individual surgeon and radiologist over a 4-year period. The primary outcome variable was achievement and 30-day maintenance of initial clinical success as defined by the Society for Vascular Surgery/American Association of Vascular Surgery reporting standards. Following standard statistical analysis, the cumulative sum (CUSUM) method was used to analyze the learning curve, with a predetermined acceptable failure rate of 10% and calculated 80% alert and 95% alarm lines.

RESULTS

Ninety-six elective endovascular AAA repairs were attempted by this team between 1998 and 2002 (mean age 74 +/- 0.8 years; mean aneurysm diameter 5.98 +/- 0.8 cm). Initial clinical success was achieved and maintained in 85 of 96 patients (88.5%). Although results were acceptable throughout the study period, improved results with respect to the target failure rate (10%) were not achieved until 60 patients were treated. The learning or CUSUM curves did not differ for different device manufacturers, with improved results being achieved following 20 implantations of each device. The results did differ when comparing aortouniiliac grafts (n = 27) and bifurcated grafts (n = 64). Results with bifurcated grafts remained consistent throughout the study period, whereas with aortouniiliac grafts, results improved after only a few procedures in comparison with the target failure rate.

CONCLUSION

Success rates with endovascular aneurysm repair will improve with an individual's experience. The CUSUM method is a valuable tool in the evaluation of this learning curve, which has credentialing and training implications. Although acceptable results were obtained throughout the study period, this analysis indicates that 60 endovascular aneurysm repairs, or 20 with an individual device, are necessary before optimal rates of initial clinical success can be achieved. These results can be achieved more readily with aortouniiliac grafts than with bifurcated grafts.

Conversion in off-pump coronary artery bypass grafting: an analysis of predictors and outcomes

BACKGROUND

The incidence, predictive factors, and outcomes related to conversion from off-pump coronary artery bypass (OPCAB) to on-pump coronary artery bypass grafting (ONCAB) have not been well defined. We sought to determine the incidence of conversion, predictive factors, and any associated adverse consequences.

METHODS

From January 2000 through June 2002, 1,644 patients underwent nonemergent OPCAB with 61 patients requiring conversion from OPCAB to ONCAB. These groups were retrospectively compared by univariate and multivariate regression analysis. The converted group was then computer matched 1:3, to a cohort of ONCAB patients to determine differences in outcomes.

RESULTS

The overall conversion rate was 3.71%. Converted patients compared with a computer-matched ONCAB patients had a higher incidence of operative mortality (18.0% versus 2.7%, p < 0.001). Urgently converted patients had a higher incidence of postoperative cardiac arrest (25% versus 1.1%, p < 0.001), multisystem organ failure (10.7% versus 0.6%, p < 0.001), vascular complications (7.1% versus 1.1%, p = 0.03), and perioperative myocardial infarction (10.7% versus 1.1%, p = 0.02). Predictive factors for conversion were surgeon early in OPCAB experience (odds ratio [OR] 4.4), previous CABG (OR 2.8), and congestive heart failure (OR 2.0). The need for urgent-emergent conversion was highly predictive for operative mortality (OR 7.3) compared with elective conversion.

CONCLUSIONS

Patients undergoing urgent-emergent but not elective conversion from OPCAB to ONCAB had a significantly higher risk of mortality and morbidity compared with patients whose procedure was initially ONCAB. Variables predictive of conversion included previous CABG, congestive heart failure, and surgeons early in OPCAB experience.

Analysis of the learning curve in telerobotic, beating heart coronary artery bypass grafting: a 90 patient experience

BACKGROUND

Recent articles have commented on the "learning curve" in robotic-assisted coronary artery bypass grafting. We systematically studied this phenomenon using standard statistical and cumulative sum (CUSUM) failure methods.

METHODS

Ninety patients underwent internal thoracic artery (ITA) takedown and an attempt at ITA to coronary bypass on the beating heart using the Zeus telerobotic system from September 1999 to December 2001. The rates of mortality and 11 predefined major complications were compared in five quintiles of 18 consecutive patients each and a CUSUM curve was generated for the entire cohort.

RESULTS

All patients but one underwent successful endoscopic ITA takedown. Thirteen patients had a totally endoscopic anastomosis, whereas in 61 a small mini-thoracotomy or mini-sternotomy was used. Sixteen patients (17.8%) were converted electively to a sternotomy: 11 patients underwent off-pump and 5 patients on-pump surgery. There were no deaths; 13 patients (14.4%) incurred one or more of the 11 major complication(s), including 5, 1, 2, 3, and 2 in each of the five quintiles (p = 0.39). Standard statistical analyses identified a significant decrease in operating room time (p < 0.0001), as well as a decrease in the incidence of an occluded graft or wrong vessel grafted from quintiles 1 to 5 (p = 0.03). On CUSUM analysis, the failure curve was steep for the first 18 to 20 patients, before moderating its slope for the remainder of the experience.

CONCLUSIONS

Robotic ITA to coronary bypass on the beating heart has a moderately steep learning curve, which is mitigated by further experience. CUSUM analysis complimented standard statistical methods in detecting a cluster of suboptimal results during the early experience with this procedure.

Complications related to off-pump bypass grafting

Surgical myocardial revascularization is a technique undergoing critical reevaluation in an attempt to reduce operative morbidity and mortality. As the age and number of comorbidities in the surgical population presenting for bypass increases, improved strategies to lessen operative risk have evolved. The use of off-pump bypass grafting to avoid the detrimental effects of extracorporeal circulation demonstrates great promise in reducing operative complications. However, with new techniques come new challenges. Avoidance of the cardiopulmonary bypass circuit has been linked to the development of a hypercoagulable state postoperatively. Complications related to the unique management of the ascending aorta and target vessels during the performance of beating heart surgery are also being reported. Moreover, despite increasing experience in a number of centers, hemodynamic collapse does occur during off-pump bypass, thereby requiring rapid institution of cardiopulmonary bypass. Continued scientific investigation and research should provide the tools to manage the unique obstacles encountered with off-pump coronary artery bypass.

Effect of off-pump coronary artery bypass grafting on risk-adjusted and cumulative sum failure outcomes after coronary artery surgery

BACKGROUND AND AIM

We have shown that cumulative sum (CUSUM) failure analysis may be more sensitive than standard statistical methods in detecting a cluster of adverse patient outcomes after cardiac surgical procedures. We therefore applied CUSUM, as well as standard statistical techniques, to analyze a surgeon's experience with off-pump coronary artery bypass grafting (OPCAB) and on-pump procedures to determine whether the two techniques have similar or different outcomes.

METHODS

In 320 patients undergoing nonemergent, first time coronary artery bypass grafting, preoperative patient characteristics, rates of mortality and major complications, and ICU and hospital lengths of stay were compared between the on-pump and OPCAB cohorts using Fisher's exact tests and Wilcoxon two sample tests. Predicted mortality and length of stay were determined using previously validated models of the Cardiac Care Network of Ontario. Observed versus expected ratios of both variables were calculated for the two types of procedures. Furthermore, CUSUM curves were constructed for the on-pump and OPCAB cohorts. A multivariable analysis of the predictors of hospital length of stay was also performed to determine whether the type of coronary artery bypass procedure had an independent impact on this variable.

RESULTS

The predicted mortality risk and predicted hospital length of stay were almost identical in the 208 on-pump patients (2.2 +/- 3.9%; 8.2 +/- 2.5 days) and the 112 OPCAB patients (2.0 +/- 2.2%; 7.8 +/- 2.1 days). The incidence of hospital mortality and postoperative stroke were 2.9% and 2.4% in on-pump patients versus zero in OPCAB patients (p = 0.09 and 0.17, respectively). Mechanical ventilation for greater than 48 hours was significantly less common in OPCAB (1.8%) than in on-pump patients (7.7%, p = 0.04). The rate of 10 major complications was 14.9% in on-pump versus 8.0% in OPCAB patients (p = 0.08). OPCAB patients experienced a hospital length of stay that was a median of 1.0 day shorter than on-pump patients (p = 0.01). The observed versus expected ratio for length of stay was 0.78 in OPCAB patients versus 0.95 in on-pump patients. On CUSUM analysis, the failure curve in OPCAB patients was negative and was flatter than that of on-pump patients throughout the duration of the study. Furthermore, OPCAB was an independent predictor of a reduced hospital length of stay on multivariable analysis.

CONCLUSIONS

OPCAB was associated with better outcomes than on-pump coronary artery bypass despite a similar predicted risk. This robust finding was documented on sensitive CUSUM analysis, using standard statistical techniques and on a multivariable analysis of the independent predictors of hospital length of stay.

A CUSUM analysis of ruptured abdominal aortic aneurysm repair

Studies have investigated the role of hospital and surgeon case volume in outcome after ruptured abdominal aortic aneurysm repair (rAAA). Few have analyzed the learning curve of an individual surgeon. The purpose of this study was to analyze this learning curve in reducing morbidity and mortality after rAAA repair. Thirty-two consecutive patients who underwent rAAA repair during the initial 2.5 years of a vascular surgeon's career were reviewed retrospectively. They were divided temporally into two groups of 16 patients (groups 1 and 2). Outcome measures included mortality, postoperative myocardial infarction, stroke, and renal and respiratory failure. Perioperative variables previously associated with increased mortality were analyzed. The cumulative sum (CUSUM) method was used to analyze the learning curve with respect to published acceptable event rates and predetermined 80% alert and 95% alarm boundary lines. Groups 1 and 2 did not differ statistically in age, preoperative blood pressure, hemoglobin or creatinine. There was no difference in transfusion requirements (6.8 +/- 1.2 units vs. 6.4 +/- 1.0 units; p = 0.78), urine output (340 +/- 65 mL vs. 389 +/- 94 mL; p = 0.72) or clamp position. There was no difference in the incidence of postoperative myocardial infarction, stroke, or respiratory or renal failure. Thirty-day mortality in group 2 was 12% as compared to 50% in Group 1 (p = 0.03). On CUSUM analysis, the cumulative failure rate in group 2 progressed lower than the 80% reassurance line, indicating improved results with time. Mortality after rAAA repair decreased over time during an early period of an individual surgeon's career. The CUSUM method is a valuable tool in analyzing an individual surgeon's experience and shows promise in quality control in vascular surgery.

Innovation in surgery: the rules of evidence

The intellectual infrastructures of evidence-based medicine (EBM) are the levels of evidence and the grades of recommendation for the following types of research articles: therapy/prevention, etiology/harm, prognosis, diagnosis, differential diagnosis/symptom prevalence study, economic analysis/decision analysis. The levels of evidence for therapy (1 to 5) progress from systematic reviews (with homogeneity) of randomized control trials (RCT) of high quality, level 1, to level 5-expert opinion without explicit critical appraisal, or based on physiology, bench research, or "first principles." The grades of recommendation (A, B, C, D) are founded on the quality of the evidence defined by its level. These grades are aimed at helping clinicians understand the source from whence came statements in, for example, guidelines. The development of surgical procedures and their introduction into practice has not depended upon the RCT but rather upon an enthusiast performing a case series, sometimes with clearly defined results. Should all operations and procedures be evaluated by an RCT? Clearly not, and the levels of evidence support this quite clearly with the "all or none" research category as level 1c. This relates to frequent clinical situations requiring a solution often immediate, eg, pus, a ruptured aneurysm, a sucking chest wound, that do not lend themselves to a trial, as the control regimen (doing nothing) would lead to death. Techniques evolve with experience usually based on an understanding of pathophysiology. At what point should an RCT enter into the resolution of surgical therapies? Can observational studies correctly designed and carried out do the job? Two new study classifications have been introduced: in level 1, category c "all or none" studies; and in level 2, category c "outcomes" research. In neither is there much definition. Are these the areas into which the evaluation of new surgical procedures and technology should be placed? The surgical community is faced with dramatic changes in technology and evolving techniques, and needs to define the rules of evidence applicable to their discipline with the same rigor that the EBM gurus have used, in order for surgeons to define evidence-based surgical practice.