Abhishek Sundaram

Development and Validation of a Risk Calculator for Prediction of Cardiac Risk After Surgery

Background— Perioperative myocardial infarction or cardiac arrest is associated with significant morbidity and mortality. The Revised Cardiac Risk Index is currently the most commonly used cardiac risk stratification tool; however, it has several limitations, one of which is its relatively low discriminative ability. The objective of the present study was to develop and validate a predictive cardiac risk calculator. Methods and Results— Patients who underwent surgery were identified from the American College of Surgeons 2007 National Surgical Quality Improvement Program database, a multicenter (>250 hospitals) prospective database. Of the 211 410 patients, 1371 (0.65%) developed perioperative myocardial infarction or cardiac arrest. On multivariate logistic regression analysis, 5 predictors of perioperative myocardial infarction or cardiac arrest were identified: type of surgery, dependent functional status, abnormal creatinine, American Society of Anesthesiologists class, and increasing age. The risk model based on the 2007 data set was subsequently validated on the 2008 data set (n=257 385). The model performance was very similar between the 2007 and 2008 data sets, with C statistics (also known as area under the receiver operating characteristic curve) of 0.884 and 0.874, respectively. Application of the Revised Cardiac Risk Index to the 2008 National Surgical Quality Improvement Program data set yielded a relatively lower C statistic (0.747). The risk model was used to develop an interactive risk calculator. Conclusions— The cardiac risk calculator provides a risk estimate of perioperative myocardial infarction or cardiac arrest and is anticipated to simplify the informed consent process. Its predictive performance surpasses that of the Revised Cardiac Risk Index.

Preoperative anemia is an independent predictor of postoperative mortality and adverse cardiac events in elderly patients undergoing elective vascular operations.

Objective: The objective of this study was to assess the impact of preoperative anemia (hematocrit <39%) on postoperative 30-day mortality and adverse cardiac events in patients 65 years or older undergoing elective vascular procedures. Background: Preoperative anemia is associated with adverse outcomes after cardiac surgery, but its association with postoperative outcomes after open and endovascular procedures is not well established. Elderly patients have a decreased tolerance to anemia and are at high risk for complications after vascular procedures. Methods: Patients (N = 31,857) were identified from the American College of Surgeons 2007–2009 National Surgical Quality Improvement Program—a prospective, multicenter (>250) database maintained across the United States. The primary and secondary outcomes of interest were 30-day mortality and a composite end point of death or cardiac event (cardiac arrest or myocardial infarction), respectively. Results: Forty-seven percent of the study population was anemic. Anemic patients had a postoperative mortality and cardiac event rate of 2.4% and 2.3% in contrast to the 1.2% and 1.2%, respectively, in patients with hematocrit within the normal range (P < 0.0001). On multivariate analysis, we found a 4.2% (95% confidence interval, 1.9–6.5) increase in the adjusted risk of 30-day postoperative mortality for every percentage point of hematocrit decrease from the normal range. Conclusions: The presence and degree of preoperative anemia are independently associated with 30-day death and adverse cardiac events in patients 65 years or older undergoing elective open and endovascular procedures. Identification and treatment of anemia should be important components of preoperative care for patients undergoing vascular operations.

Development and validation of a risk calculator for prediction of mortality after infrainguinal bypass surgery.

OBJECTIVEnFor peripheral arterial disease, infrainguinal bypass grafting (BPG) carries a higher perioperative risk compared with peripheral endovascular procedures. The choice between the open and endovascular therapies is to an extent dependent on the expected periprocedural risk associated with each. Tools for estimating the periprocedural risk in patients undergoing BPG have not been reported in the literature. The objective of this study was to develop and validate a calculator to estimate the risk of perioperative mortality ≤30 days of elective BPG.nnnMETHODSnWe identified 9556 patients (63.9% men) who underwent elective BPG from the 2007 to 2009 National Surgical Quality Improvement Program data sets. Multivariable logistic regression analysis was performed to identify risk factors associated with 30-day perioperative mortality. Bootstrapping was used for internal validation. The risk factors were subsequently used to develop a risk calculator.nnnRESULTSnPatients had a median age of 68 years. The 30-day mortality rate was 1.8% (n = 170). Multivariable logistic regression analysis identified seven preoperative predictors of 30-day mortality: increasing age, systemic inflammatory response syndrome, chronic corticosteroid use, chronic obstructive pulmonary disease, dependent functional status, dialysis dependence, and lower extremity rest pain. Bootstrapping was used for internal validation. The model demonstrated excellent discrimination (C statistic, 0.81; bias-corrected C statistic, 0.81) and calibration. The validated risk model was used to develop an interactive risk calculator using the logistic regression equation.nnnCONCLUSIONSnThe validated risk calculator has excellent predictive ability for 30-day mortality in a patient after an elective BPG. It is anticipated to aid in surgical decision making, informed patient consent, preoperative optimization, and consequently, risk reduction.

Risk index for predicting perioperative stroke, myocardial infarction, or death risk in asymptomatic patients undergoing carotid endarterectomy

OBJECTIVEnThe latest guidelines recommend performance of carotid endarterectomy (CEA) on asymptomatic patients with high-grade carotid stenosis, only if the combined perioperative stroke, myocardial infarction (MI), or death risk is ≤3%. Our objective was to develop and validate a risk index to estimate the combined risk of perioperative stroke, MI, or death in asymptomatic patients undergoing elective CEA.nnnMETHODSnAsymptomatic patients who underwent an elective CEA (nxa0= 17,692) were identified from the 2005-2010 National Surgical Quality Improvement Program, a multicenter, prospective database. Multivariable logistic regression analysis was performed with primary outcome of interest being the composite of any stroke, MI, or death during the 30-day periprocedural period. Bootstrapping was used for internal validation. A risk index was created by assigning weighted points to each predictor using the β-coefficients from the regression analysis.nnnRESULTSnFifty-eight percent of the patients were men with a median age of 72 years. Thirty-day incidences of stroke, MI, and death were 0.9% (nxa0= 167), 0.6% (nxa0= 108), and 0.4% (nxa0= 72), respectively. The combined 30-day stroke, MI, or death incidence was 1.8% (nxa0= 324). On multivariable analysis, six independent predictors were identified and a risk index created by assigning weighted points to each predictor using the β-coefficients from the regression analysis. The predictors included age in years (<60: 0 point; 60-69: -1 point; 70-79: -1 point; ≥80: 2 points), dyspnea (2 points), chronic obstructive pulmonary disease (3 points), previous peripheral revascularization or amputation (3 points), recent angina within 1 month (4 points), and dependent functional status (5 points). Patients were classified as low (<3%),xa0intermediate (3%-6%), or high (>6%) risk for combined 30-day stroke, MI, or death, based on a total point score ofxa0<4, 4-7, and >7, respectively. There were 15,249 patients (86.2%) in the low-risk category, 2233 (12.6%) in the intermediate-risk category, and 210 (1.2%) in the high-risk category.nnnCONCLUSIONSnThe validated risk index can help identify asymptomatic patients who are at greatest risk for 30-day stroke, MI, and death after CEA, thereby aiding patient selection.

Development of a risk index for prediction of mortality after open aortic aneurysm repair

OBJECTIVEnOpen infrarenal abdominal aortic aneurysm (oAAA) repair is associated with significant morbidity and mortality. Although there has been a shift toward endovascular repair, many patients continue to undergo an open repair due to anatomic considerations. Tools currently existing for estimation of periprocedural risk in patients undergoing open aortic surgery have certain limitations. The objective of this study was to develop a risk index to estimate the risk of 30-day perioperative mortality after elective oAAA repair.nnnMETHODSnPatients who underwent elective oAAA repair (n = 2845) were identified from the American College of Surgeons 2007 to 2009 National Surgical Quality Improvement Program (NSQIP), a prospective database maintained at >250 centers. Univariable and multivariable analyses were performed to evaluate risk factors associated with 30-day mortality after oAAA repair and a risk index was developed.nnnRESULTSnThe 30-day mortality after oAAA repair was 3.3%. Multivariable analysis identified six preoperative predictors of mortality, and a risk index was created by assigning weighted points to each predictor using the β-coefficients from the regression analysis. The predictors included dyspnea (at rest: 8 points; on moderate exertion: 2 points; none: 0 points), history of peripheral arterial disease requiring revascularization or amputation (3 points), age >65 years (3 points), preoperative creatinine >1.5 mg/dL (2 points), female gender (2 points), and platelets <150,000/mm(3) or >350,000/mm(3) (2 points). Patients were classified as low (<7%), intermediate (7%-15%), and high (>15%) risk for 30-day mortality based on a total point score of <8, 8 to 11, and >11, respectively. There were 2508 patients (88.2%) patients in the low-risk category, 278 (9.8%) in the intermediate-risk category, and 59 (2.1%) in the high-risk category.nnnCONCLUSIONSnThis risk index has excellent predictive ability for mortality after oAAA repair and awaits validation in subsequent studies. It is anticipated to aid patients and surgeons in informed patient consent, preoperative risk assessment, and optimization.

In-hospital and postdischarge venous thromboembolism after vascular surgery

OBJECTIVEnRecent single-center reports demonstrate a high (up to 10%) incidence of postoperative venous thromboembolism (VTE) after major vascular surgery. Moreover, vascular patients rarely receive prolonged prophylaxis despite evidence that it reduces thromboembolic events after discharge. This study used a national, prospective, multicenter database to define the incidence of overall and postdischarge VTE after major vascular operations and assess risk factors associated with VTE development.nnnMETHODSnPatients with VTE who underwent elective vascular procedures (nxa0= 45,548) were identified from the 2007-2009 National Surgical Quality Improvement Program (NSQIP) database. The vascular procedures included carotid endarterectomy (CEA; nxa0= 20,785), open thoracoabdominal aortic aneurysm (TAAA) repair (nxa0= 361), thoracic endovascular aortic repair (TEVAR; nxa0= 732), open abdominal aortic (OAA) surgery (nxa0= 6195), endovascular aneurysm repair (EVAR; nxa0= 7361), and infrainguinal bypass graft (BPG; nxa0= 10,114). Univariable and multivariable analyses were performed to ascertain risk factors associated with VTE.nnnRESULTSnVTE was diagnosed in 187 patients (1.3 %) who underwent aortic surgery, with TAAA repair having the highest rate of VTE (4.2%), followed by TEVAR (2.2%), OAA surgery (1.7%), and EVAR (0.7%). In this subgroup, pulmonary embolisms (PE) were diagnosed in 52 (0.4%) and deep venous thrombosis (DVT) in 144 (1%). VTE rates were 1.0% and 0.2% for patients who underwent a BPG or CEA, respectively. Forty-one percent of all VTEs were diagnosed after discharge. The median (interquartile range) number of days from surgery to PE and DVT were 10 (5-15) and 10 (4-18), respectively. On multivariable analyses, type of surgical procedure, totally dependent functional status, disseminated cancer, postoperative organ space infection, postoperative cerebrovascular accident, failure to wean from ventilator ≤48 hours, and return to the operating room were significantly associated with development of VTE. In those experiencing a DVT or PE, overall mortality increased from 1.5% to 6.2% and from 1.5% to 5.7% respectively (Pxa0< .05 for both).nnnCONCLUSIONSnPostoperative VTE is associated with the type of vascular procedure and is highest after operations in the chest and abdomen/pelvis. About 40% of VTE events in elective vascular surgery patients were diagnosed after discharge, and the presence of VTE was associated with a quadrupled mortality rate. Future studies should evaluate the benefit of DVT screening and postdischarge VTE prophylaxis in high-risk patients.

Readmission and Risk Factors for Readmission Following Esophagectomy for Esophageal Cancer

IntroductionReadmission after esophagectomy for esophageal cancer has not been systematically evaluated.Study ObjectiveThe objectives of this study were to determine national 30-day readmission rates after esophagectomy for esophageal cancer and evaluate risk factors associated with readmission.MethodsRetrospective review of the 2011–2012 National Surgical Quality Improvement Program dataset was performed to identify patients who underwent elective esophagectomy for esophageal cancer.ResultsOne thousand sixty-eight patients satisfied study criteria. One hundred and thirty-five patients were admitted within 30xa0days resultingxa0in a readmission rate of 12.6xa0%. Patients with a history of pulmonary disease were 3.9 times more likely to be readmitted. Patients who developed postoperative wound-related complications were 9 times more likely to be readmitted than patients who did not develop wound-related complications. Increasingxa0length ofxa0hospital stay was associated with a marginal but significant decrease in risk of readmission.ConclusionsNational 30-day readmission rate after esophagectomy for esophageal cancer is around 12.6xa0%. Risk factors associated with 30-day readmission include history of pulmonary disease, postoperative wound-related complications, and length of hospital stay.

Response to Letter Regarding Article, “Development and Validation of a Risk Calculator for Prediction of Cardiac Risk After Surgery”

We thank Drs Lee and Goldman for their comments on our publication.1The doctors state that the ratio of postoperative cardiac arrest to myocardial infarction (MI) is 2.5:1 in our study in comparison with a ratio of 0.3:1 in their study.2 Based on this finding, they contend that cardiac arrests in our study should more appropriately be attributed to noncardiac causes, and thus the Revised Cardiac Risk Index (RCRI) more accurately estimates the risk of cardiac complications after surgery.nnIt should be remembered that, among the patients in the dataset used to develop the RCRI (n=2893) in 1999, 56 (2%) patients developed a major cardiac complication. There were only 9 (0.3%) with cardiac arrest, 2 (0.1%) with complete heart block, 28 (1%) with …

High Resolution Impedance Manometry Findings in Nutcracker Esophagus

Stricture was defined as dysphagia promoting endoscopic dilatation. Risk factors for development of stricture were identified using univariate and multivariate logistic regression analyses. Results Esophagectomy was performed in 526 patients. The median age was 66 yrs (2189) and 423 (80.4%) were male. Benign strictures developed in 125 (23.4%) patients at a median of 55 days (range 18-2230) after surgery, requiring a median of 2 dilatations (range: 1-25); 113 (85%) needed less than 4 dilatations. Of the 125 patients, 75 (60%) developed stricture within 60 days after esophagectomy. Prior chemoradiation (OR 2.602, 95% CI (1.635-4.141), p<0.001) and retrosternal placement of conduit (OR 2.806, 95% CI (1.3495.838), p=0.006) were independent predictive factors on multivariate analysis. Organ used for esophageal replacement, anastomtoic leakage, the site of anastomosis, and medical complications were not. When refractory stricture was defined by those requiring 4 or more dilatations, the only predictive factor was delayed appearance of stricture at 60 days or more after operation (OR 2.562, 95% CI (1.082-6.067), p=0.032). Conclusions Neoadjuvant chemoradiation and retrosternal placement of conduit were independent predictors for development of benign anastomotic strictures after esophagectomy. Most patients required less than 4 dilatations. Delayed in appearance of stricture (more than 60 days after surgery) predicted the need of more dilatations.

Changes in Re-Operative Intervention for Failed Anti-Reflux Surgeries Over the Past 19 Years in Our Practice

Background: Parallel with the increasing number of laparoscopic anti-reflux operations there is increasing number of re-operative interventions for failed procedures. We have performed 316 re-operative procedures from Feb/1992 to Nov/2010. The aim of this study was to compare presenting symptoms, endoscopic findings and operative approaches over the years. Methods: A retrospective review of a prospectively maintained database was performed of patients who underwent re-operative intervention after one or more previous anti-reflux surgeries. After institutional board review the database and charts were reviewed and analyzed for presenting symptoms, pre-operative endoscopic findings and operative procedures. Results: There was a significant increase in the number of re-operative interventions over the years (first 5 yrs: 8 procedures, second 5 yrs: 63 operations, third 5 yrs: 105 operations, last 4 yrs: 140 operations). The procedure was the first re-operation in 289 cases, second in 25 cases, third in 1 case and in 1 case it was the fourth re-operation. We divided the 316 operations into two halves, the first 158 patients (Group 1) were operated on from 2/ 1/1992 to 6/5/2006, the second half (Group 2) was operated on from 6/15/2006 to 11/2/ 2010. The most common indications for a re-operative procedure were heartburn (27% and 26%) and dysphagia (33% and 28% in each group) and did not change over the years. Preoperative upper endoscopy revealed a recurrent sliding hiatus hernia (> 2cm) in 61 and 71 patients, disrupted fundoplication in 74 and 89 patients, twisted fundoplication or twocompartment stomach in 20 and 26 cases, slipped fundoplication in 56 and 54 patients and a paraesophageal hernia in 32 and 37 patients in each group respectively. There was no significant difference in the pattern of failure over the years. Re-operation consisted of redo-fundoplication in 141 and 81 patients; Roux-en-Y reconstruction (RNY) in 14 and 70 patients and esophagectomy was performed in 3 and 7 patients, respectively. A significantly higher number of procedures were done laparoscopicaly in the second group (108 vs 80, p=0.001). A large hiatus hernia (> 2 cm) with a slipped fundoplication was found in 29 and 38 patients in the two groups. In this subset of patients a significantly larger number of RNY reconstructions were performed in the second group (3 vs 20, p=0.0003), while gastroplasty was used more frequently in the first group (8 vs 0, p=0.0001). Discussion: While there has been no significant change in the presenting symptoms and anatomical derangements encountered in patients undergoing re-operative intervention for failed fundoplication, a larger number of cases have been completed laparoscopically with an increasing utilization of RNY construction.