Relationship of hospital size, case volume, and cost for coronary artery bypass surgery: analysis of 12,774 patients operated on in Massachusetts during fiscal years 1995 and 1996.

OBJECTIVE: This study investigates the relationship between the cost of coronary artery bypass graft surgery and both hospital size and case volume. METHODS: Retrospective administrative and cost data were obtained for all 12,774 patients who underwent isolated coronary bypass surgery at 12 Massachusetts hospitals during 1995 and 1996. Hospitals were stratified by number of operating beds into 3 groups (group I, <250 beds; group II, 250-450 beds; group III, >450 beds). Total (diagnosis-related groups 106 + 107) annual coronary bypass cases per hospital varied from 271 to 913 (mean 532). Univariate and multivariable analyses were used to study the relationship between the direct and total cost and a number of patient (age, sex, acuity class, payer) and hospital (bed capacity, annual case volume per diagnosis-related group, cardiothoracic residency) predictor variables. For each hospital, we also studied the relationship between changes in coronary bypass case volume and the corresponding changes in average cost from 1995 to 1996. RESULTS: Scatterplots revealed a broad range of mean direct cost of coronary bypass surgery among hospitals with comparable case volumes. When annual cases were analyzed as continuous variables, there was no linear relationship of case volume with direct or total cost of coronary bypass (r = -0.05 to +0.08) for any diagnosis-related group or year. When hospital bed capacity and case volume were grouped into strata and studied by analysis of variance, there was no evidence of an inverse relationship between these variables and cost. In multivariable analysis, patient acuity class and diagnosis-related group were the most important predictors of cost. Beds and case volume met inclusion criteria for most models but added little to the "explanation" of variability R(2), often less than 1%. Finally, substantial interhospital differences were noted in the magnitude and direction (direct vs inverse) of their 1995 to 1996 change in volume versus change in cost. CONCLUSIONS: Within the range of hospital size and case volume represented in this study, there is no evidence that either variable is related to the cost of performing coronary bypass surgery. Massachusetts hospitals appear to function on different segments of different average cost curves. It is not possible to predict the relative cost of coronary bypass grafting at a given hospital based primarily on volume.

Cardiac surgery report cards: comprehensive review and statistical critique.

Public report cards and confidential, collaborative peer education represent distinctly different approaches to cardiac surgery quality assessment and improvement. This review discusses the controversies regarding their methodology and relative effectiveness. Report cards have been the more commonly used approach, typically as a result of state legislation. They are based on the presumption that publication of outcomes effectively motivates providers, and that market forces will reward higher quality. Numerous studies have challenged the validity of these hypotheses. Furthermore, although states with report cards have reported significant decreases in risk-adjusted mortality, it is unclear whether this improvement resulted from public disclosure or, rather, from the development of internal quality programs by hospitals. An additional confounding factor is the nationwide decline in heart surgery mortality, including states without quality monitoring. Finally, report cards may engender negative behaviors such as high-risk case avoidance and "gaming" of the reporting system, especially if individual surgeon results are published. The alternative approach, continuous quality improvement, may provide an opportunity to enhance performance and reduce interprovider variability while avoiding the unintended negative consequences of report cards. This collaborative method, which uses exchange visits between programs and determination of best practice, has been highly effective in northern New England and in the Veterans Affairs Administration. However, despite their potential advantages, quality programs based solely on confidential continuous quality improvement do not address the issue of public accountability. For this reason, some states may continue to mandate report cards. In such instances, it is imperative that appropriate statistical techniques and report formats are used, and that professional organizations simultaneously implement continuous quality improvement programs. The statistical methodology underlying current report cards is flawed, and does not justify the degree of accuracy presented to the public. All existing risk-adjustment methods have substantial inherent imprecision, and this is compounded when the results of such patient-level models are aggregated and used inappropriately to assess provider performance. Specific problems include sample size differences, clustering of observations, multiple comparisons, and failure to account for the random component of interprovider variability. We advocate the use of hierarchical or multilevel statistical models to address these concerns, as well as report formats that emphasize the statistical uncertainty of the results.

Selection of a cardiac surgery provider in the managed care era.

OBJECTIVE: Many health planners promote the use of competition to contain cost and improve quality of care. Using a standard econometric model, we examined the evidence for "value-based" cardiac surgery provider selection in eastern Massachusetts, where there is significant competition and managed care penetration. METHODS: McFadden's conditional logit model was used to study cardiac surgery provider selection among 6952 patients and eight metropolitan Boston hospitals in 1997. Hospital predictor variables included beds, cardiac surgery case volume, objective clinical and financial performance, reputation (percent out-of-state referrals, cardiac residency program), distance from patient's home to hospital, and historical referral patterns. Subgroup analyses were performed for each major payer category. RESULTS: Distance from patient's home to hospital (odds ratio 0.90; P =.000) and the historical referral pattern from each patient's hometown (z = 45.305; P =.000) were important predictors in all models. A cardiac surgery residency enhanced the probability of selection (odds ratio 5.25; P =.000), as did percent out-of-state referrals (odds ratio 1.10; P =.001). Higher mortality rates were associated with decreased probability of selection (odds ratio 0.51; P =.027), but higher length of stay was paradoxically associated with greater probability (odds ratio 1.72; P =.000). Total hospital costs were irrelevant (odds ratio 1.00; P =.179). When analyzed by payer subgroup, Medicare patients appeared to select hospitals with both low mortality (odds ratio 0.43; P =.176) and short length of stay (odds ratio 0.76; P =.213), although the results did not achieve statistical significance. The commercial managed care subgroup exhibited the least "value-based" behavior. The odds ratio for length of stay was the highest of any group (odds ratio = 2.589; P =.000) and there was a subset of hospitals for which higher mortality was actually associated with greater likelihood of selection. CONCLUSIONS: The observable determinants of cardiac surgery provider selection are related to hospital reputation, historical referral patterns, and patient proximity, not objective clinical or cost performance. The paradoxic behavior of commercial managed care probably results from unobserved choice factors that are not primarily based on objective provider performance.

Papillary fibroelastomas.

Papillary fibroelastomas are rare benign neoplasms, predominantly involving cardiac valves, that have been discovered with increasing frequency through the use of echocardiography. Most are papillary lesions, less than 1 cm in size, connected to the valve or mural endocardium by a small stalk. Although often asymptomatic, embolization from the lesion or attached thrombus may cause serious neurological or cardiac events. All symptomatic papillary fibroelastomas should be removed unless there are compelling contraindications, in which case anticoagulation is an acceptable but unreliable alternative. Surgical removal is safe, simple, effective, and permanent. Asymptomatic lesions of the left side of the heart should be removed because of their potentially serious or fatal consequences, whereas those arising from the right side of the heart may be observed.

Readmission after cardiac operations: prevalence, patterns, and predisposing factors.

OBJECTIVES: This study was undertaken (1) to determine the prevalence of hospital readmission within 1 month of discharge after cardiac operations, (2) to categorize diagnoses responsible for readmission, and (3) to examine predischarge patient factors that influenced readmission. METHODS: Data at 1 month after discharge were obtained for 1665 (98.4%) of 1692 patients who underwent cardiac operations between January 1996 and July 1998. RESULTS: Two hundred twenty-five patients (13.5%) were readmitted to a hospital within a 1-month period after discharge. Forty-eight percent of readmissions were to other hospitals. The most common readmission problems were congestive heart failure (15.6%), atrial fibrillation (12.9%), chest pain (12.0%), wound problems (10.2%), and gastrointestinal problems (8.0%). Hospital discharge on or before the fifth postoperative day was associated with a lower prevalence of subsequent readmission. The independent predictors of a readmission for congestive heart failure were postoperative stay longer than 5 days, diabetes, New York Heart Association functional class IV, preoperative congestive heart failure, total blood product use, the need for postoperative inotropes, body mass index greater than 28 kg/m(2), and reoperation for bleeding. CONCLUSIONS: The prevalence of rehospitalization during the first month after discharge is not trivial. Other than postoperative atrial fibrillation, readmission is probably the single most likely adverse event to befall a patient in the early postoperative period. Patients who are discharged early do not appear to be at increased risk. Patterns in readmission diagnoses suggest opportunities for preventive strategies.

Reduction of neurologic injury after high-risk thoracoabdominal aortic operation.

BACKGROUND: Of all aortic operations, thoracoabdominal aortic repairs have the highest risk of spinal cord neurologic injury, manifest by lower limb paraplegia or paraparesis. Cerebrospinal fluid drainage combined with intrathecal papaverine (CSFDr + IP) may reduce the risk and severity of neurologic injury. The objective of this study was to evaluate the effect of CSFDr + IP to prevent neurologic injury after high-risk thoracoabdominal aneurysm repairs. METHODS: We screened 64 patients before operation with descending thoracic or thoracoabdominal aneurysms for possible inclusion in a prospective, randomized study. Thirty-three patients with high-risk type I and II thoracoabdominal aneurysms met inclusion criteria and 17 were randomly assigned to CSFDr + IP and 16 to the control group. The study was terminated early after interim analysis revealed a significant difference. RESULTS: Of 64 patients screened, 2 patients died after operation (3.1%, 2/64); both were in the randomized study (6%, 2/33), and neither had a neurologic injury. Neurologic injury developed in 2 CSFDr + IP patients and 7 control patients (p = 0.0392). Control patients also had lower postoperative motor strength scores (p = 0.0340). On multivariate analysis, risk factors for neurologic injury included (p < 0.05) longer cross-clamp time, failure to actively cool with bypass, and postoperative hypotension, whereas CSFDr + IP was protective. Logistic regression showed that CSFDr + IP and active cooling significantly reduced the risk of injury and that the two combined modalities were additive. Of 64 patients screened, only 2 (3%) had a permanent neurologic deficit preventing ambulation. CONCLUSIONS: For high-risk thoracoabdominal aneurysms, CSFDr + IP was effective in reducing the incidence and severity of neurologic injury. Active cooling may be further additive to CSFDr + IP protection, although this needs to be confirmed in a larger study.

Coronary artery bypass risk prediction using neural networks.

BACKGROUND: Neural networks are nonparametric, robust, pattern recognition techniques that can be used to model complex relationships. METHODS: The applicability of multilayer perceptron neural networks (MLP) to coronary artery bypass grafting risk prediction was assessed using The Society of Thoracic Surgeons database of 80,606 patients who underwent coronary artery bypass grafting in 1993. The results of traditional logistic regression and Bayesian analysis were compared with single-layer (no hidden layer), two-layer (one hidden layer), and three-layer (two hidden layer) MLP neural networks. These networks were trained using stochastic gradient descent with early stopping. All prediction models used the same variables and were evaluated by training on 40,480 patients and cross-validation testing on a separate group of 40,126 patients. Techniques were also developed to calculate effective odds ratios for MLP networks and to generate confidence intervals for MLP risk predictions using an auxiliary "confidence MLP." RESULTS: Receiver operating characteristic curve areas for predicting mortality were approximately 76% for all classifiers, including neural networks. Calibration (accuracy of posterior probability prediction) was slightly better with a two-member committee classifier that averaged the outputs of a MLP network and a logistic regression model. Unlike the individual methods, the committee classifier did not overestimate or underestimate risk for high-risk patients. CONCLUSIONS: A committee classifier combining the best neural network and logistic regression provided the best model calibration, but the receiver operating characteristic curve area was only 76% irrespective of which predictive model was used.

Screening carotid ultrasonography and risk factors for stroke in coronary artery surgery patients.

BACKGROUND: The role of noninvasive carotid artery screening in relation to other clinical variables in identifying patients at increased risk of stroke after coronary artery bypass grafting was examined. METHODS: Preoperative, intraoperative, and postoperative clinical data were prospectively collected for 1,835 consecutive patients undergoing first-time isolated coronary artery bypass grafting between March 1990 and July 1995, 1,279 of whom had screening carotid ultrasonography. All patients with postoperative neurologic events were identified and reviewed in detail. Average patient age was 65.3 years (range, 33 to 92 years), and 9.3% (171 patients) had a prior permanent stroke or transient ischemic attack. Hospital and 30-day mortality was 2.2% (41 patients). Forty-five patients (2.5%) had a transient or permanent postoperative neurologic event. The data were analyzed by stepwise logistic regression to determine the independent predictors of both significant carotid stenosis and stroke. RESULTS: On multivariate analysis, the clinical predictors of significant carotid stenosis were age (p < 0.0001), diabetes (p = 0.0123), female sex (p = 0.0026), left main coronary stenosis greater than 60% (p < 0.0001), prior stroke or transient ischemic attack (p = 0.0008), peripheral vascular disease (p = 0.0001), prior vascular operation (p = 0.0068), and smoking (p < 0.0001). When all variables were evaluated for those patients who underwent noninvasive carotid artery screening, the independent predictors of postoperative neurologic event were prior stroke or transient ischemic attack (p < 0.0001), peripheral vascular disease (p = 0.0037), postinfarction angina pectoris (p = 0.0319), postoperative atrial fibrillation (p = 0.0014), carotid stenosis greater than 50% (p = 0.0029), cardiopulmonary bypass time (p = 0.0006), significant aortic atherosclerosis (p = 0.0054), postoperative amrinone or epinephrine use (p = 0.0054), and left ventricular ejection fraction less than 0.30 (p = 0.0744). CONCLUSIONS: The etiology of postoperative stroke is multifactorial. Selective use of carotid ultrasonography is of value in identifying patients who are at greater risk of postoperative stroke independent of other variables and should be considered before coronary artery bypass grafting, particularly in patients with a history of neurologic event or peripheral vascular disease.

Applications of statistical quality control to cardiac surgery.

BACKGROUND: Although originally developed for use in manufacturing statistical quality control techniques may be applicable to other frequently performed, standardized processes. METHODS: We employed statistical quality control charts (X- s, p, and u) to analyze perioperative morbidity and mortality and length of stay in 1,131 nonemergent, isolated, primary coronary bypass operations conducted within a 17-quarter time period. RESULTS: The incidence of the most common adverse outcomes, including death, myocardial infarction, stroke, and atrial fibrillation, appeared to follow the laws of statistical fluctuation and were in statistical control. Postoperative bleeding, leg-wound infection, and the summation of total and major complications were out of statistical control in the early quarters of the study period but showed progressive improvement, as did postoperative length of stay. CONCLUSIONS: The incidence of morbidity and mortality after primary, isolated, nonemergent coronary bypass operations may be described by standard models of statistical fluctuation. Statistical quality control may be a valuable method to analyze the variability of these adverse postoperative events over time, with the ultimate goal of reducing that variability and producing better outcomes.

Circadian variation in defibrillation energy requirements.

BACKGROUND: Reports have demonstrated a circadian variation in the incidence of acute myocardial infarction, ventricular arrhythmias, and sudden cardiac death. We tested the hypothesis that a similar circadian variation exists for defibrillation energy requirements in humans. METHODS AND RESULTS: We reviewed the time of defibrillation threshold (DFT) measurements in 134 patients with implantable cardioverter-defibrillators (ICDs) who underwent 345 DFT measurements. The DFT was determined in 130 patients at implantation, in 121 at a 2 months, and in 94 at 6 months. All patients had nonthoracotomy systems. The morning DFT (8 AM to 12 noon) was 15.1 +/- 1.2 J compared with 13.1 +/- 0.9 J in the midafternoon (12 noon to 4 PM) and 13.0 +/- 0.7 J in the late afternoon (4 to 8 PM), P < .02. In a separate group of 930 patients implanted with an ICD system with date and time stamps for each therapy, we reviewed 1238 episodes of ventricular tachyarrhythmias treated with shock therapy. To corroborate the hypothesis that energy requirements for arrhythmia termination vary during the course of the day, we plotted the failed first shock frequency for all episodes per hour. There was a significant peak in failed first shocks in the morning compared with other time intervals (P = .02). CONCLUSIONS: There is a morning peak in DFT and a corresponding morning peak in failed first shock frequency. This morning peak resembles the peaks seen in other cardiac events, specifically sudden cardiac death. These findings have important implications for appropriate ICD function, particularly in patients with marginal DFTs.

Timing of surgery after acute myocardial infarction.

OBJECTIVE: We wished to determine if timing of surgery, when other co-morbid variables are controlled, influenced outcome after operations for acute myocardial infarction. DESIGN: Between 3/20/1990 and 6/17/1994, data was prospectively collected on 338 patients undergoing operation for either evolving infarcts (n=73) or up to 21 days after infarction (mean 7.9 days). SETTING: Tertiary hospital referral center. PATIENTS: Infarction was diagnosed by CK enzymes or EKG Q-waves preoperatively in 338 patients undergoing surgery. The mean age of the patients was 66.1 years (SD+/-10.5 years), 76 had emergency operations immediately after catheterization (50 following PTCA complications), 223 had urgent operations, and 39 were elective. INTERVENTIONS: Seventy-three had preoperative ballon pumps, and 259 had one or more mammary artery bypasses with a mean of 3.27 (SD+/-1.0) distal anastomoses. RESULTS: In-hospital and 30-day survival rate was 95.6% (323/338). Of the 73 variables evaluated by step-wise logistic regression analysis, the multivariate independent preoperative predictors of death were: aortic valve regurgitation, chronic pulmonary disease, preoperative diuretic administration, preoperative balloon pump, preoperative inotropes, and the need for additional concomitant noncardiac surgery. Including the operative variables, the predictors were: preoperative balloon pump, preoperative inotropes, the presence of left main stenosis, preoperative renal failure, chronic pulmonary disease, valve disease, ischemic arrhythmia, pump perfusion time, valve surgery, and homologous blood transfusion volume required. When the postoperative variables were included, the predictors were: preoperative inotropes, postoperative balloon pump, postoperative epinephrine, postoperative permanent stroke, and postoperative acute renal failure. The time between infarction and operation was not an independent prediction (p>0.4) in any of the logistic regression models. CONCLUSION: Early operation after acute infarction is not in itself a risk factor, rather comorbid disease and preoperative hemodynamic status determine outcome after surgery.

Anterior ischemic optic neuropathy after open heart operations.

BACKGROUND: The overall incidence of anterior ischemic optic neuropathy after open heart operations at the Lahey Clinic is less than 0.5%. However, during the 2-year period, March 1, 1990, to March 1, 1992, an increased incidence (8 of 602 patients or 1.3%) of this complication was observed. METHODS: A rigorous analysis was conducted of all 602 patients who underwent operation during this period. RESULTS: No preoperative risk factors were identified. The development of anterior ischemic optic neuropathy was associated with prolonged cardiopulmonary bypass time, low hematocrit levels, excessive perioperative body weight gain, and the use of epinephrine and amrinone. Other hypothetical risk factors include systemic hypothermia, anemia, increased intraocular pressure, and microembolization. Treatment options include the use of corticosteroid medications, reduction of intraocular pressure, and optic nerve fenestration, although recent evidence and our experience indicate that the fenestration procedure is of no benefit. CONCLUSIONS: Because all methods of treatment have had limited success, efforts to prevent this complication are of paramount importance.

Endarterectomy for calcified porcelain aorta associated with aortic valve stenosis.

BACKGROUND: A calcified porcelain aorta may complicate aortic valve insertion and require an alternative, more complex method for valve replacement. The reason for this is that sutures cannot be inserted through the calcific plates in the annulus and ascending aorta. METHODS: In 6 patients with an average age of 73.8 years (range, 65 to 81 years), we performed the simpler procedure of aortic endarterectomy of the calcific plates with the aortic valve replacement. We realized that there may be an increased risk of postoperative complications, particularly stroke. The calcific plates were fractured to allow debridement of the calcium. In addition, an end-arterectomy was performed of the left main coronary ostium in 2 patients, and 5 patients also had coronary artery bypass grafting performed. RESULTS: All 6 patients underwent successful operations without major complications. On follow-up, echocardiography or computed tomographic scans in 3 patients have not shown dilation of the ascending aorta. CONCLUSION: Endarterectomy of the aorta may be an option in the management of patients with calcification of the aorta.

The role of coronary revascularization in recipients of an implantable cardioverter-defibrillator.

The impact of adjuvant coronary revascularization was studied in a group of 138 recipients of an implantable cardioverter-defibrillator, all of whom had ischemic heart disease as the cause of their arrhythmias. Patients chosen for revascularization had more severe anatomic, symptomatic, or physiologic evidence of active ischemia. There were no operative deaths among 23 patients who actually underwent coronary artery bypass combined with cardioverter-defibrillator implantation; however, operative mortality by the intention-to-treat principle was 8% (2/25). Total cardiac survival was better for patients who underwent revascularization than for those patients who had "high-risk" characteristics and did not undergo revascularization. Stratified subgroup analysis demonstrated significant survival advantages favoring revascularization in patients with three-vessel or left main coronary artery disease, class III or IV angina, and an ejection fraction greater than 25%. Multivariate analysis revealed that low ejection fraction and left main coronary artery disease were independent predictors of decreased survival.

Transvenous versus transthoracic cardioverter-defibrillator implantation. A comparative analysis of morbidity, mortality, and survival.

The hypothesis that transvenous implantation of a cardioverter-defibrillator is associated with less morbidity than use of a transthoracic approach was investigated in a retrospective series of 146 patients. None of these patients had concomitant heart procedures, and the preoperative characteristics of the two groups were similar. When analyzed by actual technique used (transvenous, 57 patients; transthoracic, 89 patients) and by the intention-to-treat method (transvenous, 65 patients, 8 of whom actually underwent thoracotomy; thoracotomy, 81 patients), transvenous implantation was associated with a lower incidence of postoperative respiratory complications and atrial fibrillation. Total cardiac mortality and freedom from sudden cardiac death in the transvenous and transthoracic groups were comparable at 2 years.

Anti-Jkb delayed hemolytic transfusion reaction after coronary bypass surgery.

Delayed hemolytic transfusion reaction occurred in a 74-year-old woman after coronary bypass. Antibodies were not detected during preoperative screening but did appear late after exposure to Jkb-positive red blood cells, probably as an anamnestic response to previous exposure during childbirth or remote transfusion. The incidence, pathophysiology, clinical presentation, diagnosis, and management of this syndrome are discussed.

Transvenous cardioverter defibrillators: cost implications of a less invasive approach.

To assess the economic impact of a transvenous lead system for an implantable cardioverter defibrillator (ICD), we evaluated the hospital charges for two groups of patients: group I patients (n = 23) underwent implantation of an ICD generator with an epicardial lead system via a thoracotomy and group II patients (n = 25) underwent implantation of the same generator using transvenous leads. There was no difference in demographics between the two groups. There was a 15% decrease in total charges for the transvenous group compared to the thoracotomy group ($54,142 vs $63,359, P < 0.05). Evaluation of the component charges revealed that the decline could be attributed to a reduction in implant ($27,328 vs $29,285, P < 0.02) and convalescent charges ($7,703 vs $15,179, P < 0.01) for the transvenous group. There was a corresponding decrease in length of stay for the transvenous group (22 vs 29 days, P < 0.05) largely secondary to a 38% reduction in convalescent length of stay (8 vs 13 days, P < 0.05). We conclude that the use of transvenous lead systems for the ICD results in a significant reduction in hospital charges as well as hospital length of stay.

Etiology and management of chronic valve disease in antiphospholipid antibody syndrome and systemic lupus erythematosus.

Unlike the Libman-Sacks vegetations of acute systemic lupus erythematosus (SLE), which are usually asymptomatic, valve involvement in chronic SLE and primary antiphospholipid antibody syndrome (APLAS) is similar to that of chronic rheumatic disease. Typical findings include valve thickening and nodularity, poor coaptation, and regurgitation. Elevated levels of antiphospholipid antibodies have been associated with the development of these valvular abnormalities in some but not all reported cases, and there are undoubtedly other etiologic cofactors. When cardiac valvular replacement is required, special attention must be given to preoperative reduction of elevated antibody levels, prevention of intraoperative thromboembolism, and prompt and aggressive postoperative anticoagulation.

Cardiac papillary fibroelastoma.

Papillary fibroelastomas are rare cardiac tumors, but they are the most common primary tumor of the heart valves. These lesions occur on any of the valves or endothelial surfaces of the heart and may be detected by echocardiography, cardiac catheterization, during open heart operation for other conditions, or at autopsy. Because of their potential for cerebral and coronary embolization, even small papillary fibroelastomas should be excised.