The impact of hospital size on national trends and outcomes in isolated open proximal aortic surgery.

OBJECTIVE: To determine the impact of hospital size on national trend estimates of isolated open proximal aortic surgery for benchmarking hospital performance. METHODS: Patients age >18 years who underwent isolated open proximal aortic surgery for aneurysm and dissection from 2002 to 2014 were identified using the National Inpatient Sample. Concomitant valvular, vessel revascularization, re-do procedures, endovascular, and surgery for descending and thoracoabdominal aorta were excluded. Discharges were stratified by hospital size and analyzed using trend, multivariable regression, propensity-score matching analysis. RESULTS: Over a 13-year period, 53,657 isolated open proximal aortic operations were performed nationally. Although the total number of operations/year increased (∼2.9%/year increase) and overall in-hospital mortality decreased (∼4%/year; both P < .001 for trend), these did not differ by hospital size (P > .05). Large hospitals treated more sicker and older patients but had shorter length of stay and lower hospital costs (both P < .001). Even after propensity-score matching, large hospital continued to demonstrate superior in-hospital outcomes, although only statistically for major in-hospital cardiac complications compared with non-large hospitals. In our subgroup analysis of dissection versus non-dissection cohort, in-hospital mortality trends decreased only in the non-dissection cohort (P < .01) versus dissection cohort (P = .39), driven primarily by the impact of large hospitals (P < .01). CONCLUSIONS: This study demonstrates increasing volume and improving outcomes of isolated open proximal aortic surgeries nationally over the last decade regardless of hospital bed size. Moreover, the resource allocation of sicker patients to larger hospital resulted shorter length of stay and hospital costs, while maintaining similar operative mortality to small- and medium-sized hospitals.

Current Readings: Single vs Bilateral Internal Mammary Artery in Coronary Artery Bypass Grafting.

There is strong retrospective data demonstrating that bilateral internal mammary artery (BIMA) grafting leads to better long-term survival as compared to left internal mammary artery grafting. However, this survival advantage was not corroborated by the interim results of the Arterial Revascularization Trial. Today, there are barriers to widespread adoption of BIMA grafting. One of the main disadvantages of the use of BIMA grafts is the higher risk of deep sternal wound infection. Deep sternal wound infections can be minimized by skeletonized harvesting of the internal mammary artery grafts, which preserve blood flow to the sternum. Also, utilizing the BIMA graft as a "Y" graft may lead to more complete revascularization compared to its in situ use. BIMA grafting on average takes 25 minutes longer operating time with a higher in-hospital costs. We eagerly await the 10-year results of the Arterial Revascularization Trial to determine the truly unbiased randomized long-term effectiveness of BIMA grafting.

Parsimonious assessment for reoperative aortic valve replacement; the deterrent effect of low left ventricular ejection fraction and renal impairment.

BACKGROUND: Patient comorbidities play a pivotal role in the surgical outcomes of reoperative aortic valve replacement (re-AVR). Low left ventricular ejection fraction (LVEF) and renal insufficiency (Cr >2 mg/dL) are known independent surgical risk factors. Improved preoperative risk assessment can help determine the best therapeutic approach. We hypothesize that re-AVR patients with low LVEF and concomitant renal insufficiency have a prohibitive surgical risk and may benefit from transcatheter AVR (TAVR). METHODS: From January 2002 to March 2013, we reviewed 232 patients who underwent isolated re-AVR. Patients older than 80 years were excluded to adjust for unobserved frailty. We identified 37 patients with a ≤35% LVEF (low ejection fraction group-LEF) and 195 patients with >35% LVEF (High ejection fraction group-HEF). RESULTS: The mean age was 68.4±11.5 years and there were more females (86.5% versus 64.1%, P=0.007) in the LEF group. The prevalence of renal insufficiency was higher in LEF patients (27% versus 5.6%, P=0.001). Higher operative mortality (13.5% versus 3.1%, P=0.018) was observed in the LEF group. Stroke rates were similar in both groups (8.1% versus 4.1%, P=0.39). Unadjusted cumulative survival was significantly lower in LEF patients (6.6 years, 95% CI: 5.2-8.0, versus 9.7 years, 95% CI: 8.9-10.4, P=0.024). In patients without renal insufficiency, LEF and HEF had similar survival (8.3 years, 95% CI: 7.1-9.5, versus 9.9 years, 95% CI: 9.1-10.6, P=0.90). Contrarily, in patients with renal insufficiency, LEF led to a significantly lower survival (1.1 years, 95% CI: 0.1-2.0, versus 4.8 years, 95% CI: 2.2-7.3, P=0.050). Adjusted survival analysis revealed elevations in baseline creatinine (HR =4.28, P<0.001) and LEF (HR =5.33, P=0.041) as significant predictors of long-term survival, with a significant interaction between these comorbidities (HR =7.28, P<0.001). CONCLUSIONS: In re-AVR patients, low LVEF (≤35%) is associated with increased operative mortality. Concomitant renal insufficiency in these patients results in a prohibitively low cumulative survival. These reoperative surgical outcomes should warrant expanding the role of TAVR for reoperative patients with LEF and renal impairment.

Evaluation of The Society of Thoracic Surgeons Online Risk Calculator for Assessment of Risk in Patients Presenting for Aortic Valve Replacement After Prior Coronary Artery Bypass Graft: An Analysis Using the STS Adult Cardiac Surgery Database.

BACKGROUND: Accurate risk assessment in patients presenting for aortic valve replacement (AVR) after prior coronary artery bypass grafting (CABG) is essential for appropriate selection of surgical versus percutaneous therapy. METHODS: We included 6,534 patients in The Society for Thoracic Surgeons (STS) Adult Cardiac Surgery Database (October 2009 through December 2013) who underwent elective, isolated reoperative AVR for aortic stenosis after prior CABG. Case-specific PROM was calculated and observed-to-expected ratios were inspected across the spectrum of risk. A cohort-specific recalibration equation was derived using logistic regression: = expit(-0.6453+0.6147*logit(PROM) -0.0709*logit(PROM)(ˆ)2), where PROM is the predicted risk of mortality. The proportion of patients reclassified as low (PROM < 4%), intermediate (4% to < 8%), high (8% to < 12%), and very high risk (≥ 12%) was calculated using the recalibration equation. The performance of the cohort-specific recalibration equation was then compared with the generic recalibration for quarterly STS reports. RESULTS: The STS online risk calculator overestimates risk for low, intermediate, and high risk categories. Using the recalibrated risk equation, a substantial proportion of patients were reclassified as the following: 25.5% from intermediate to low risk; 39.7% from high to intermediate risk; and 41.5% from very high to high risk. Comparison of the cohort-specific recalibration equation to the generic quarterly STS recalibration demonstrated very similar results. CONCLUSIONS: In patients presenting for AVR after prior CABG, the STS online risk calculator overestimates risk for all but the highest risk patients. Using a cohort-specific recalibration equation, a substantial proportion of patients would be downgraded to lower risk categories. The cohort-specific recalibration correlates well with the existing generic quarterly STS recalibration. The findings of this study support recommendations for periodic recalibration of the online risk calculator in order to facilitate clinical decision making in real time.

Mechanical versus bioprosthetic mitral valve replacement in patients <65 years old.

OBJECTIVE: Because of its durability, the mechanical valve is typically chosen for young patients undergoing mitral valve replacement (MVR). However, a bioprosthetic valve might have the benefit of valve-in-valve transcatheter valve replacement when valve failure occurs. We examined the outcomes in patients who had undergone mechanical valve MVR (MVRm) versus bioprosthetic valve MVR (MVRb) in patients aged <65 years. METHODS: A total of 768 consecutive patients aged <65 years, who had undergone MVR from January 1991 to June 2012 were identified. Propensity matching was used to derive a case-control subset for analysis. Long-term outcomes were collected by chart review, routine patient follow-up, and query of the Social Security Death Index. The postoperative and long-term outcomes of interest included combined stroke and embolic events, reoperations, and mortality. RESULTS: Of 768 consecutive patients, 627 were in the MVRm and 141 in the MVRb group. Propensity score matching yielded a cohort of 125 MVRb (89%) and 125 control MVRm patients with similar etiology mixes. The groups were similar in age (MVRm, 53.2 ± 9.0 years; MVRb, 53.8 ± 10.6 years; P = .617) and other preoperative characteristics. The postoperative outcomes were also similar between the 2 groups, including reoperation for bleeding, stroke, deep sternal infection, sepsis, and length of hospital stay. The operative mortality was also similar (MVRm, 5.6%; MVRb, 8.0%; P = .617). However, Kaplan-Meier analysis showed the MVRb group had a greater reoperation rate (P = .001) and shorter estimated survival (11.3 vs 13.5 years, P = .004). The incidence of bleeding and stroke or embolic events between the 2 groups was similar. CONCLUSIONS: In the present report, MVRb for patients <65 years old was associated with a high reoperation rate and decreased survival. Although a future transcatheter valve-in-valve technique for a failed bioprosthetic valve might reduce the risk of reoperation, this finding confirms the safety of mechanical valves in this group.

A shifting approach to management of the thoracic aorta in bicuspid aortic valve.

OBJECTIVES: The scientific understanding of aortic dilation associated with bicuspid aortic valve (BAV) has evolved during the past 2 decades, along with improvements in diagnostic technology and surgical management. We aimed to evaluate secular trends and predictors of thoracic aortic surgery among patients with BAV in the United States. METHODS: We used the 1998-2009 Nationwide Inpatient Sample, an administrative dataset representative of US hospital admissions, to identify hospitalizations for adults aged 18 years or more with BAV and aortic valve or thoracic aortic surgery. Covariates included age, gender, year, aortic dissection, endocarditis, thoracic aortic aneurysm, number of comorbidities, hospital teaching status and region, primary insurance, and concomitant coronary artery bypass surgery. RESULTS: Between 1998 and 2009, 48,736 ± 3555 patients with BAV underwent aortic valve repair or replacement and 1679 ± 120 patients with BAV underwent isolated thoracic aortic surgery. The overall number of surgeries increased more than 3-fold, from 4556 ± 571 in 1998/1999 to 14,960 ± 2107 in 2008/2009 (P < .0001). The proportion of aortic valve repair or replacement including concomitant thoracic aortic surgery increased from 12.8% ± 1.4% in 1998/1999 to 28.5% ± 1.6% in 2008/2009, which mirrored an increasing proportion of patients with a diagnosis of thoracic aortic aneurysm. Mortality was equivalent for patients undergoing aortic valve repair or replacement with thoracic aortic surgery and those undergoing isolated aortic valve repair or replacement (1.8% ± 0.3% vs 1.5% ± 0.2%; multivariable odds ratio, 1.02; 95% confidence interval, 0.67-1.57), with decreasing mortality over the study period (from 2.5% ± 0.6% in 1998/1999 to 1.5% ± 0.2% in 2008/2009; multivariable odds ratio per 2-year increment, 0.89; 95% confidence interval, 0.81-0.99; P = .03). Total charges for BAV surgical hospitalizations increased more than 7.5-fold from approximately $156 million in 1998 to $1.2 billion in 2009 (inflation-adjusted 2009 dollars). CONCLUSIONS: There was a marked increase in the use of thoracic aortic surgery among patients with BAV.

Comparison of the utility of preoperative versus postoperative B-type natriuretic peptide for predicting hospital length of stay and mortality after primary coronary artery bypass grafting.

BACKGROUND: Preoperative B-type natriuretic peptide (BNP) is known to predict adverse outcomes after cardiac surgery. The value of postoperative BNP for predicting adverse outcomes is less well delineated. The authors hypothesized that peak postoperative plasma BNP (measured postoperative days 1-5) predicts hospital length of stay (HLOS) and mortality in patients undergoing primary coronary artery bypass grafting, even after adjusting for preoperative BNP and perioperative clinical risk factors. METHODS: This study is a prospective longitudinal study of 1,183 patients undergoing primary coronary artery bypass grafting surgery. Mortality was defined as all-cause death within 5 yr after surgery. Cox proportional hazards analyses were conducted to separately evaluate the associations between peak postoperative BNP and HLOS and mortality. Multivariable adjustments were made for patient demographics, preoperative BNP concentration, and clinical risk factors. BNP measurements were log10 transformed before analysis. RESULTS: One hundred fifteen deaths (9.7%) occurred in the cohort (mean follow-up = 4.3 yr, range = 2.38-5.0 yr). After multivariable adjustment for preoperative BNP and clinical covariates, peak postoperative BNP predicted HLOS (hazard ratio [HR] = 1.28, 95% CI = 1.002-1.64, P = 0.049) but not mortality (HR = 1.62, CI = 0.71-3.68, P = 0.25), whereas preoperative BNP independently predicted HLOS (HR = 1.09, CI = 1.01-1.18, P = 0.03) and approached being an independent predictor of mortality (HR = 1.36, CI = 0.96-1.94, P = 0.08). When preoperative and peak postoperative BNP were separately adjusted for within the clinical multivariable models, each independently predicted HLOS (preoperative BNP HR = 1.13, CI = 1.05-1.21, P = 0.0007; peak postoperative BNP HR = 1.44, CI = 1.15-1.81, P = 0.001) and mortality (preoperative BNP HR = 1.50, CI = 1.09-2.07, P = 0.01; peak postoperative BNP HR = 2.29, CI = 1.11-4.73, P = 0.02). CONCLUSIONS: Preoperative BNP may be better than peak postoperative BNP for predicting HLOS and longer term mortality after primary coronary artery bypass grafting surgery.

Heparin dose response is independent of preoperative antithrombin activity in patients undergoing coronary artery bypass graft surgery using low heparin concentrations.

BACKGROUND: Unfractionated heparin's primary mechanism of action is to enhance the enzymatic activity of antithrombin (AT). We hypothesized that there would be a direct association between preoperative AT activity and both heparin dose response (HDR) and heparin sensitivity index (HSI) in patients undergoing coronary artery bypass graft surgery. METHODS: Demographic and perioperative data were collected from 304 patients undergoing primary coronary artery bypass graft surgery. AT activity was measured after induction of general anesthesia using a colorimetric method (Siemens Healthcare Diagnostics, Tarrytown, NY). Activated coagulation time (ACT), HDR, and HSI were measured using the Hepcon HMS Plus system (Medtronic, Minneapolis, MN). Heparin dose was calculated for a target ACT using measured HDR by the same system. Multivariate linear regression was performed to identify independent predictors of HDR. Subgroup analysis of patients with low AT activity (<80% normal; <0.813 U/mL) who may be at risk for heparin resistance was also performed. RESULTS: Mean baseline ACT was 135 ± 18 seconds. Mean calculated HDR was 98 ± 21 s/U/mL. Mean baseline AT activity was 0.93 ± 0.13 U/mL. Baseline AT activity was not significantly associated with baseline or postheparin ACT, HDR, or HSI. Addition of AT activity to multivariable linear regression models of both HDR and HSI did not significantly improve model performance. Subgroup analysis of 49 patients with baseline AT <80% of normal levels did not reveal a relationship between low AT activity and HDR or HSI. Preoperative AT activity, HDR, and HSI were not associated with cardiac troponin I levels on the first postoperative day, intensive care unit duration, or hospital length of stay. CONCLUSION: Although enhancing AT activity is the primary mechanism by which heparin facilitates cardiopulmonary bypass anticoagulation, low preoperative AT activity is not associated with impaired response to heparin or to clinical outcomes when using target ACTs of 300 to 350 seconds.