Daniel J. Bertges

The Vascular Study Group of New England Cardiac Risk Index (VSG-CRI) predicts cardiac complications more accurately than the Revised Cardiac Risk Index in vascular surgery patients

OBJECTIVE The Revised Cardiac Risk Index (RCRI) is a widely used model for predicting cardiac events after noncardiac surgery. We compared the accuracy of the RCRI with a new, vascular surgery-specific model developed from patients within the Vascular Study Group of New England (VSGNE). METHODS We studied 10,081 patients who underwent nonemergent carotid endarterectomy (CEA; n = 5293), lower extremity bypass (LEB; n = 2673), endovascular abdominal aortic aneurysm repair (EVAR; n = 1005), and open infrarenal abdominal aortic aneurysm repair (OAAA; n = 1,110) within the VSGNE from 2003 to 2008. First, we analyzed the ability of the RCRI to predict in-hospital major adverse cardiac events, including myocardial infarction (MI), arrhythmia, or congestive heart failure (CHF) in the VSGNE cohort. Second, we used a derivation cohort of 8208 to develop a new cardiac risk prediction model specifically for vascular surgery patients. Chi-square analysis identified univariate predictors, and multivariate logistic regression was used to develop an aggregate and four procedure-specific risk prediction models for cardiac complications. Calibration and model discrimination were assessed using Pearson correlation coefficient and receiver operating characteristic (ROC) curves. The ability of the model to predict cardiac complications was assessed within a validation cohort of 1873. Significant predictors were converted to an integer score to create a practical cardiac risk prediction formula. RESULTS The overall incidence of major cardiac events in the VSGNE cohort was 6.3% (2.5% MI, 3.9% arrhythmia, 1.8% CHF). The RCRI predicted risk after CEA reasonably well but substantially underestimated risk after LEB, EVAR, and OAAA for low- and higher-risk patients. Across all VSGNE patients, the RCRI underestimated cardiac complications by 1.7- to 7.4-fold based on actual event rates of 2.6%, 6.7%, 11.6%, and 18.4% for patients with 0, 1, 2, and >or=3 risk factors. In multivariate analysis of the VSGNE cohort, independent predictors of adverse cardiac events were (odds ratio [OR]) increasing age (1.7-2.8), smoking (1.3), insulin-dependent diabetes (1.4), coronary artery disease (1.4), CHF (1.9), abnormal cardiac stress test (1.2), long-term beta-blocker therapy (1.4), chronic obstructive pulmonary disease (1.6), and creatinine >or=1.8 mg/dL (1.7). Prior cardiac revascularization was protective (OR, 0.8). Our aggregate model was well calibrated (r = 0.99, P < .001), demonstrating moderate discriminative ability (ROC curve = 0.71), which differed only slightly from the procedure-specific models (ROC curves: CEA, 0.74; LEB, 0.72; EVAR, 0.74; OAAA, 0.68). Rates of cardiac complications for patients with 0 to 3, 4, 5, and >or=6 VSG risk factors were 3.1%, 5.0%, 6.8%, and 11.6% in the derivation cohort and 3.8%, 5.2%, 8.1%, and 10.1% in the validation cohort. The VSGNE cardiac risk model more accurately predicted the actual risk of cardiac complications across the four procedures for low- and higher-risk patients than the RCRI. When the VSG Cardiac Risk Index (VSG-CRI) was used to score patients, six categories of risk ranging from 2.6% to 14.3% (score of 0-3 to 8) were discernible. CONCLUSIONS The RCRI substantially underestimates in-hospital cardiac events in patients undergoing elective or urgent vascular surgery, especially after LEB, EVAR, and OAAA. The VSG-CRI more accurately predicts in-hospital cardiac events after vascular surgery and represents an important tool for clinical decision making.

Factors associated with amputation or graft occlusion one year after lower extremity bypass in northern New England

BACKGROUND Optimal patient selection for lower extremity bypass surgery requires surgeons to predict which patients will have durable functional outcomes following revascularization. Therefore, we examined risk factors that predict amputation or graft occlusion within the first year following lower extremity bypass. METHODS Using our regional quality-improvement initiative in 11 hospitals in northern New England, we studied 2,306 lower extremity bypass procedures performed in 2,031 patients between January 2003 and December 2007. Sixty surgeons contributed to our database, and over 100 demographic and clinical variables were abstracted by trained researchers. Cox proportional hazards models were used to generate hazard ratios and surrounding 95% confidence intervals (CIs) for our combined outcome measure of major amputation (above-knee or below-knee) or permanent graft occlusion (loss of secondary patency) occurring within the first year postoperatively. RESULTS We found that within our cohort of 2,306 bypass procedures 17% resulted in an amputation or graft occlusion within 1 year of surgery. Of the 143 amputations performed (8% of all limbs undergoing bypasses), 17% occurred in the setting of a patent graft. Similarly, of the 277 graft occlusions (12% of all bypasses), 42% resulted in a major amputation. We identified eight preoperative patient characteristics associated with amputation or graft occlusion in multivariate analysis: age <50, nonambulatory status preoperatively, dialysis dependence, diabetes, critical limb ischemia, need for venovenostomy, tarsal target, and living preoperatively in a nursing home. While patients with no risk factors had 1-year amputation/occlusion rates that were <1%, patients with three or more risk factors had a nearly 30% chance of suffering amputation or graft occlusion by 1 year postoperatively. When we compared risk-adjusted rates of amputation/occlusion across centers, we found that one center in our region performed significantly better than expected (observed/expected ratio 0.7, 95% CI 0.6-0.9, p < 0.04). CONCLUSION Preoperative risk factors allow surgeons to predict the risk of amputation or graft occlusion following lower extremity bypass and to more precisely inform patients about their operative risk and functional outcomes. Additionally, our model facilitates comparison of risk-adjusted outcomes across our region. We believe quality-improvement measures such as these will allow surgeons to identify best practices and thereby improve outcomes across centers.

Optimal selection of asymptomatic patients for carotid endarterectomy based on predicted 5-year survival.

OBJECTIVE Although carotid endarterectomy (CEA) is performed to prevent stroke, long-term survival is essential to ensure benefit, especially in asymptomatic patients. We examined factors associated with 5-year survival following CEA in patients with asymptomatic internal carotid artery (ICA) stenosis. METHODS Prospectively collected data from 4114 isolated CEAs performed for asymptomatic stenosis across 24 centers in the Vascular Study Group of New England between 2003 and 2011 were used for this analysis. Late survival was determined with the Social Security Death Index. Cox proportional hazard models were used to identify risk factors for mortality within the first 5 years after CEA and to calculate a risk score for predicting 5-year survival. RESULTS Overall 3- and 5-year survival after CEA in asymptomatic patients were 90% (95% CI 89%-91%) and 82% (95% CI 81%-84%), respectively. By multivariate analysis, increasing age, diabetes, smoking history, congestive heart failure, chronic obstructive pulmonary disease, poor renal function (estimated glomerular filtration rate <60 or dialysis dependence), absence of statin use, and worse contralateral ICA stenosis were all associated with worse survival. Patients classified as low (27%), medium (68%), and high risk (5%) based on number of risk factors had 5-year survival rates of 96%, 80%, and 51%, respectively (P < .001). CONCLUSIONS More than four out of five asymptomatic patients selected for CEA in the Vascular Study Group of New England achieved 5-year survival, demonstrating that, overall, surgeons in our region selected appropriate patients for carotid revascularization. However, there were patients selected for surgery with high risk profiles, and our models suggest that the highest risk patients (such as those with multiple major risk factors including age ≥ 80, insulin-dependent diabetes, dialysis dependence, and severe contralateral ICA stenosis) are unlikely to survive long enough to realize a benefit of prophylactic CEA for asymptomatic stenosis. Predicting survival is important for decision making in these patients.

Perioperative management with antiplatelet and statin medication is associated with reduced mortality following vascular surgery

OBJECTIVE Many patients undergoing vascular surgical procedures are not on appropriate medical therapy. This study sought to examine the variation and impact of antiplatelet (AP) and statin therapy on early and late mortality in patients undergoing vascular surgery in our region. METHODS We studied all patients (n = 14,489) undergoing elective carotid endarterectomy (n = 6978), carotid stenting (n = 524), and suprainguinal (n = 763) and infrainguinal bypass (n = 3053), as well as patients with known coronary risk factors undergoing open (n = 1044) and endovascular (n = 2127) abdominal aortic aneurysm repair from 2005 to 2012 in the Vascular Study Group of New England. Optimal medical management was defined as treatment with both AP and statin agents, preoperatively and at discharge. We analyzed temporal, procedural, and center variation of medication use. Multivariable analyses were used to determine the adjusted impact of AP and statin therapy on 30-day mortality and 5-year survival. RESULTS Optimal medical management improved over the study interval (55% in 2005 to 68% in 2012; P trend < .01) with carotid interventions having the highest rates of optimal medications use (carotid artery stenting, 78%; carotid endarterectomy, 74%) and abdominal aortic aneurysm repair in patients with known cardiac risk factors having the lowest (open, 57%; endovascular aneurysm repair, 56%). Optimal medication use varied by center as well (range, 40%-86%). Preoperative AP and statin use was associated with reduced 30-day mortality (odds ratio, 0.76; 95% confidence interval [CI], 0.5-1.05; P = .09). AP and statin prescription at discharge was additive in survival benefit with improved 5-year survival (hazard ratio, 0.5; 95% CI, 0.4-0.7; P < .01) that was consistent across procedure types. Patients prescribed AP and statin at discharge had 5-year survival of 79% (95% CI, 77%-81%) compared with only 61% (95% CI, 52%-68%; P < .001) for patients on neither medication. CONCLUSIONS AP and statin therapy preoperatively and at discharge was associated with reduced 30-day mortality and an absolute 18% improved 5-year survival after vascular surgery. However, one-third of patients are suboptimally managed in real world practice. This demonstrates an opportunity for quality improvement that can substantially improve survival after vascular surgery.

A regional quality improvement effort to increase beta blocker administration before vascular surgery.

OBJECTIVE To determine if a regional quality improvement effort can increase beta-blocker utilization prior to vascular surgery and decrease the incidence of postoperative myocardial infarction (POMI). METHODS A quality improvement effort to increase perioperative beta blocker utilization was implemented in 2003 at centers participating in the Vascular Study Group of New England (VSGNE). A 90% target was set and feedback given at biannual meetings. Beta blocker utilization (<1 month preoperative versus chronic) and POMI rates were prospectively collected for patients undergoing open abdominal aortic aneurysm (AAA) repair (n = 926) and lower extremity bypass (LEB; n = 2,123) from 2003 through 2008. Predictors of POMI were determined using multivariate logistic regression. Rates of beta blocker administration and POMI were analyzed over time, and across strata of patient risk based on a multivariate model. RESULTS Perioperative beta blocker treatment increased from 68% of patients in the first 3 months of 2005 to 88% by the last 3 months of 2008 (P < .001). In 2003, 44% of patients not on chronic beta blockers were treated with preoperative beta blockers; by 2008, 78% of patients not on chronic beta blockers were started perioperatively on these medications (P < .001). Beta blocker utilization increased across all centers and surgeons participating during the study period, and increased in patients of low, medium, and high cardiac risk. However, the rate of POMI did not change over time (5.2% in 2003, 5.5% in 2008; P = .876), although a trend towards lower POMI rate was seen in patients on preoperative beta blockers (4.4% in 2003-2005, 2.6% in 2006-2008; P = .43). In multivariable modeling we found that age >70 (odds ratio [OR], 2.1), positive stress test (OR, 2.2), congestive heart failure (CHF; OR, 1.7), chronic beta blocker administration (OR, 1.7), resting heart rate <70 (OR, 1.8), and diabetes (OR, 1.6) were associated with POMI. Resting heart rate was similar for patients on chronic (67), preoperative (70), and no beta blockers (70; P = .521). CONCLUSIONS Our regional quality improvement effort successfully increased perioperative beta blocker utilization. However, this was not associated with reduced rates of POMI or resting heart rate. While this demonstrates the effectiveness of regional quality improvement efforts in changing practice patterns, further work is necessary to more precisely identify those patients who will benefit from beta blockade at the time of vascular surgery.

Outcomes of symptomatic abdominal aortic aneurysm repair

OBJECTIVE Operative mortality of patients undergoing symptomatic abdominal aortic aneurysm (Sx-AAA) repair has been reported at 6% to 30% during the past 25 years. We used a multicenter regional database to describe the contemporary outcomes of patients undergoing repair of Sx-AAA. METHODS All patients undergoing infrarenal AAA repair in 11 hospitals comprising the Vascular Study Group of Northern New England (VSGNNE) between 2003 and 2009 were studied. Sx-AAA was prospectively defined as an AAA accompanied by abdominal or back pain or tenderness, but without rupture. The primary study end point was in-hospital mortality. Secondary end points included in-hospital postoperative major adverse events (MAE) and late survival. These outcomes were compared between symptomatic patients and contemporary VSGNNE cohorts of elective (E-AAA) and ruptured AAAs (R-AAAs) treated within the same study period. RESULTS During the study period, 2386 AAA repairs were performed, comprising 1959 (82%) E-AAAs, 156 (7%) Sx-AAAs, and 271 (11%) R-AAAs. Repair was endovascular in 945 (48%) E-AAAs, 60 (38%) Sx-AAAs, and 33 (12%) R-AAAs. Hospital mortality was 1.7% for E-AAA repair and 1.3% for Sx-AAA repair, but was 34.7% for R-AAA repair (P < .001). The MAE rates were 20%, 35%, and 63%, respectively, for E-AAA, Sx-AAA, and R-AAA repairs (P < .001). The mean Glasgow Aneurysm Score (GAS) for Sx-AAA patients who survived was 79 +/- 12. Those who died had an average score of 92 +/- 7, and 83% of all Sx-AAA and R-AAA patients who died had a GAS >85. Kaplan-Meier analysis demonstrated that at 1 and 4 years, Sx-AAA repair was associated with intermediate survival (83% and 68%) compared with E-AAA repair (89% and 73%) and R-AAA repair (49% and 35%; P < .001). CONCLUSION The operative mortality of patients with Sx-AAA in contemporary practice appears better than that previously reported in the literature. Despite low operative mortality, MAE and late survival are intermediate compared with E-AAA and R-AAA repair. Review of previous series shows a trend for lower operative mortality after Sx-AAA repair in more recent series, which likely reflects improved perioperative care and more use of endovascular aneurysm repair.

Comparison of graft patency, limb salvage, and antithrombotic therapy between prosthetic and autogenous below-knee bypass for critical limb ischemia.

BACKGROUND The autogenous vein is the preferred conduit in below-knee vascular reconstructions. However, many argue that prosthetic grafts can perform well in crural bypass with adjunctive antithrombotic therapy. We therefore compared outcomes of below-knee prosthetic versus autologous vein bypass grafts for critical limb ischemia and the use of adjunctive antithrombotic therapy in both settings. METHODS Utilizing the registry of the Vascular Study Group of New England (2003-2009), we studied 1227 patients who underwent below-knee bypass for critical limb ischemia, 223 of whom received a prosthetic graft to the below-knee popliteal artery (70%) or more distal target (30%). We used propensity matching to identify a patient cohort receiving single-segment saphenous vein yet had remained similar to the prosthetic cohort in terms of characteristics, graft origin/target, and antithrombotic regimen. Main outcome measures were graft patency and major limb amputation within 1 year. Secondary outcomes were bleeding complications (reoperation or transfusion) and mortality. We performed comparisons by conduit type and by antithrombotic therapy. RESULTS Patients receiving prosthetic conduit were more likely to be treated with warfarin than those with greater saphenous vein (57% vs. 24%, P<0.001). After propensity score matching, we found no significant difference in primary graft patency (72% vs. 73%, P=0.81) or major amputation rates (17% vs. 13%, P=0.31) between prosthetic and single-segment saphenous vein grafts. In a subanalysis of grafts to tibial versus popliteal targets, we noted equivalent primary patency and amputation rates between prosthetic and venous conduits. Whereas overall 1-year prosthetic graft patency rates varied from 51% (aspirin+clopidogrel) to 78% (aspirin+warfarin), no significant differences were seen in primary patency or major amputation rates by antithrombotic therapy (P=0.32 and 0.17, respectively). Further, the incidence of bleeding complications and 1-year mortality did not differ by conduit type or antithrombotic regimen in the propensity-matched analysis. CONCLUSIONS Although limited in size, our study demonstrates that, with appropriate patient selection and antithrombotic therapy, 1-year outcomes for below-knee prosthetic bypass grafting can be comparable to those for greater saphenous vein conduit.

Evaluation of Simulation-Based Training Model on Vascular Anastomotic Skills for Surgical Residents

Introduction Reduced work hours and concerns over patient safety have encouraged surgical educators to find methods to advance resident skills more efficiently. Simulation provides the opportunity to improve technical surgical skills outside the operating room. We hypothesized that practice on surgical task simulators would improve residents’ technical performance of vascular anastomotic technique. Methods Senior general surgery residents at an academic medical center completed pretests and posttests on 3 vascular surgery simulators: femoral-popliteal bypass, carotid endarterectomy, and abdominal aortic aneurysm repair. The initial training sessions began with a 15-minute instructional video on how to perform the procedures, followed by supervised sessions in anastomotic technique with attending vascular surgeons. Initial individual sessions were videotaped as a pretest, and the final attempt was videotaped as the posttest. Each test was evaluated by a single experienced attending vascular surgeon blinded to the examinees. Anastomoses were graded using a performance rating and a modified objective structured assessment of technical skill rating. Results were analyzed using mixed model P values. Results The residents showed statistically significant improvement between the pretest and the posttest in both their performance rating (1.9 vs. 2.4, P = 0.02) and the objective structured assessment of technical skill (2.6 vs. 3.1, P = 0.01), as well as in most subsets of each assessment scale. Conclusions We conclude that practice using simulated anastomotic models leads to measurable improvement in vascular anastomotic technique in senior general surgery residents.

The influence of gender on functional outcomes of lower extremity bypass

OBJECTIVE Our aim was to evaluate the effect of gender on early and late procedural and functional outcomes of lower extremity bypass (LEB). METHODS We reviewed the records of 2576 patients (828 women; 32%) who underwent LEB for claudication or critical limb ischemia (CLI) in the Vascular Study Group of New England from 2003 to 2010. Logistic regression and proportional hazards models were used to adjust for potential confounding differences between genders. Morbidity, mortality, graft patency, freedom from major amputation, ambulation, and living status were analyzed postoperatively and over 1 year. RESULTS Women were older (70 vs 68 years; P < .001), had more hypertension (89% vs 85%; P = .006), less coronary artery disease (35% vs 39%; P = .03), smoking (73% vs 88%; P < .001), and preoperative statin use (60% vs 64%; P = .04). Women were more likely to have CLI (76% vs 71%; P = .003), and ambulate with assistance at presentation (19% vs 16%; P = .02). Morbidity was similar except women had higher rates of reoperation for thrombosis (4% vs 2%; P < .001) without differences in major amputation (2% vs 1%; P = .13) or in-hospital mortality (1.7% vs 1.7%; P = .96). Women and men with claudication had similar 1-year graft patency rates. Women with CLI had lower rates of primary (hazard ratio [HR], 1.24; 95% confidence interval [CI], 1.03-1.48; P = .02), assisted primary (HR, 1.42; 95% CI, 1.15-1.76; P = .001) and secondary patency (HR, 1.40; 95% CI, 1.10-1.77; P = .006) during the first year compared with men. Freedom from amputation was similar for men and women with CLI (HR, 1.17; 95% CI, 0.84-1.63; P = .36). There were no differences in late survival between women and men with claudication (HR, 0.89; 95% CI, 0.60-1.31; P = .36) or CLI (HR, 0.94; 95% CI, 0.81-1.09; P = .39). More female claudicants were not independently ambulatory at discharge (30% vs 19%; P = .002) and were discharged to a nursing home (15% vs 5%; P < .001) but these differences did not persist at 1 year. Women with CLI were more likely to be nonambulatory at discharge (13% vs 9%; P = .006) and at 1 year (13% vs 8%; P < .001). More women with CLI were discharged to a nursing home (44% vs 35%; P = .01) and resided there at 1 year (11% vs 7%; P = .02). CONCLUSIONS Women have complication rates similar to men with inferior early and late functional outcomes after LEB. The reduced patency rates in women with CLI did not translate into differences in limb salvage. These findings might help define physician and patient expectations for women before revascularization.

Preoperative β-blockers do not improve cardiac outcomes after major elective vascular surgery and may be harmful.

OBJECTIVE Routine initiation β-blocker medications before vascular surgery is controversial due to conflicting data. The purpose of this analysis was to determine whether prophylactic use of β-blockers before major elective vascular surgery decreased postoperative cardiac events or mortality. METHODS The Society for Vascular Surgery Vascular Quality Initiative (SVS-VQI) data set was used to perform a retrospective cohort analysis of infrainguinal lower extremity bypass (LEB), aortofemoral bypass (AFB), and open abdominal aortic aneurysm (AAA) repair patients. Chronic (>30 days preoperatively) β-blocker patients were excluded, and comparisons were made between preoperative (0-30 day) and no β-blocker groups. Patients were risk stratified using a novel prediction tool derived specifically from the SVS-VQI data set. Propensity-matched pairs and interprocedural specific risk stratification comparisons were performed. End points included in-hospital major adverse cardiac events (MACEs), including myocardial infarction (MI; defined as new ST or T wave electrocardiographic changes, troponin elevation, or documentation by echocardiogram or other imaging modality), dysrhythmia, and congestive heart failure, and 30-day mortality. RESULTS The study analyzed 13,291 patients (LEB, 68% [n = 9047]; AFB, 11% [n = 1474]; and open AAA, 21% [n = 2770]); of these, 67.7% (n = 8999) were receiving β-blockers at time of their index procedure. Specifically, 13.2% (n = 1753) were identified to have been started on a preoperative β-blocker, 54.5% (n = 7426) were on chronic β-blockers, and 32.3% (n = 4286) were on no preoperative β-blockers. Among the three procedures, patients had significant demographic and comorbidity differences and thus were not combined. A 1:1 propensity-matched pairs analysis (1459 pairs) revealed higher rates of postoperative MI with preoperative β-blockers (preoperative β-blocker relative risk, 1.65; 95% confidence interval, 1.02-2.68; P = .05 vs no β-blocker), with no difference in dysrhythmia, congestive heart failure, or 30-day mortality. When stratified into low-risk, medium-risk, and high-risk groups within each procedure, all groups of preoperative β-blocker patients had no difference or higher rates of MACEs and 30-day mortality, with the exception of high-risk open AAA patients, who had a lower rate of MI (odds ratio, 0.35; 95% confidence interval, 011-0.87; P = .04). CONCLUSIONS Exclusive of high-risk open AAA patients, preoperative β-blockers did not decrease rates of MACEs or mortality after LEB, AFB, or open AAA. Importantly, exposure to prophylactic preoperative β-blockers increased the rates of some adverse events in several subgroups. Given these data, the SVS-VQI cannot support routine initiation of preoperative β-blockers before major elective vascular surgery in most patients.