Bilal H. Kirmani

Comparison of the EuroSCORE II and Society of Thoracic Surgeons 2008 risk tools

OBJECTIVES Risk stratification in cardiac surgery is uniquely detailed, led latterly by the EuroSCORE and the Society of Thoracic Surgeons (STS) risk calculators. The recently published EuroSCORE II (ES2) algorithms update estimated mortality in a broad spectrum of cardiac procedures. The 2008 STS tool, in comparison, predicts multiple outcomes for specific procedures. We sought to identify and compare the external validity of both contemporaneous tools in our population. METHODS Data from our hospital database were collated for the period February 2001 to March 2010. Logistic regression coefficients from the risk calculations were applied to the data and the results presented as receiver-operating characteristic (ROC) curves. Statistical analyses were performed using the area under the ROC curve (AUROC) and the Hosmer-Lemeshow (H-L) goodness-of-fit test, with comparisons using the DeLong method. RESULTS A total of 15 497 procedures were identified, of which 14 432 were appropriate for STS risk scoring (i.e. valve and/or graft procedures with no tricuspid valve operations etc.). For all procedures, ES2 and STS were equivalent (AUROC 0.818 vs 0.805, respectively, P = 0.343). For procedures appropriate for STS risk scoring, results were similar (AUROC ES2 vs STS, 0.816 vs 0.810, P = 0.714), whereas for procedures excluded by STS, the result was marginally worse (AUROC ES2 vs STS, 0.773 vs 0.784, P = 0.751). Goodness of fit in all cases was poor, primarily where risk was higher than 15% (H-L P < 0.0001). CONCLUSIONS EuroSCORE II and STS both provide equivalent discrimination in predicting mortality in a British population, including those undergoing procedures for which the STS does not normally predict. Accounting for decile-grouped Hosmer-Lemeshow tests not being ideal for the assessment of calibration, both tools show good calibration for patients with low to moderate risk, with divergence from ~15% predicted risk.

The effect of patient sex on survival in patients undergoing isolated coronary artery bypass surgery receiving a radial artery

OBJECTIVES To determine whether patient sex makes a difference to in-hospital mortality and survival in patients undergoing isolated coronary artery bypass graft surgery (CABG) receiving a radial artery graft. METHODS Analysis of consecutive patients on a validated prospective cardiac surgery database was performed for patients undergoing isolated CABG. Uni- and multivariate analyses were performed for in-hospital mortality and long-term survival. A propensity analysis was also performed. RESULTS Overall mortality was 2.1% (n = 284) for all cases, n = 13 369. Median follow-up was 7.0 (interquartile range 4.1-10.1) years. Of the cases 28.2% of males (n = 384) and 29.7% of females (n = 764) had a radial artery utilized. Univariate analysis demonstrated that in-hospital mortality was significantly lower in male patients, P < 0.001, and radial artery use was associated with increased survival in males, P < 0.0001, but not in females, P = 0.82. In male patients, multivariate analysis failed to identify the radial artery as a risk factor for in-hospital death. The radial artery was identified as a significant prognostic factor, associated with improved long-term survival (hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.69-0.88, P = 0.0001). Propensity analysis confirmed this finding (HR 0.76, 95% CI 0.67-0.86, P < 0.0001). In female patients, multivariate analysis failed to identify the radial artery as a significant factor determining in-hospital mortality or long-term survival. Propensity analysis confirmed these findings. CONCLUSION Males derive a significant survival advantage if they receive a radial artery graft when undergoing isolated CABG. The radial artery makes no difference to long-term survival in female patients. Radial artery use does not affect in-hospital mortality regardless of patient sex.

Stage migration: results of lymph node dissection in the era of modern imaging and invasive staging for lung cancer

OBJECTIVES Lung cancer staging has improved in recent years. Assuming that contemporary detailed preoperative staging may yield a lower rate of stage change after surgery, we were interested to determine the impact of our lymph node dissections performed at the time of surgical resection. METHODS We retrospectively analysed a database in our surgical unit that prospectively captured information on all patients assessed and treated for lung cancer. We reviewed the data on patients who underwent lung cancer surgery with curative intent between January 2006 and August 2010 so as to reflect contemporary practice. Prior to potentially curative treatment, patients systematically underwent staging computerized tomography (CT), integrated positron emission tomography (PET) with CT and brain imaging. Enlarged and/or PET-positive nodes were subject to invasive evaluation to establish the nodal status in line with the current guidelines. This was performed by needle aspiration or biopsy usually with ultrasound guidance, endobronchial or endo-oesophageal ultrasound with needle biopsy; mediastinoscopy; mediastinotomy; video-assisted or open surgery. RESULTS Three hundred and twelve lung cancer resections were performed (a mean age of 68 years [range 42-86] and a male-to-female ratio of 1.14:1). Despite thorough preoperative evaluations, 25.3% of patients had a change in nodal status after lung resection and lymph node dissection; of which 20.8% of patients had a nodal status upstaging. Occult N2 disease was identified in 31 (9.9%) of 312 patients. Patients with cT1 tumours showed a nodal upstaging of 12.3% compared with 25.3% in cT2 tumours. There was no difference in the rate of N2 disease for different tumour histological types. CONCLUSIONS Despite systematic preoperative staging, there continues to be a high rate of nodal status change following surgical resection and lymph node dissection. If considering non-surgical treatments for the early stage lung cancer, the impact of this discrepancy should be considered. If not, errors in prognosis and in determining correct adjuvant treatment may arise.

External validity of the Society of Thoracic Surgeons risk stratification tool for deep sternal wound infection after cardiac surgery in a UK population

OBJECTIVES Deep sternal wound infection (DSWI) is a devastating complication of cardiac surgery, with a historical incidence of 0.4-5%. Predicting which patients are at higher risk of infection may help instituting various preventive measures. Risk calculations for mortality have been used as surrogates to estimate the risk of deep sternal wound infection, with limited success. The Society of Thoracic Surgeons (STS) 2008 Risk Calculator modelled the risk of DSWI for cardiac surgical patients, but it has not been validated since its publication. We sought to assess the external validity of the STS-estimated risk of DSWI in a United Kingdom (UK) population. METHODS Using our prospectively captured database, we retrospectively calculated the risk of DSWI for 14 036 patients undergoing valve, coronary artery bypass grafts or combined procedures between February 2001 and March 2010. DSWI was identified according to the Centre for Disease Control and Prevention definition. The receiver operator characteristic (ROC) curve was employed to test the performance of the model using the area under the ROC curve (AUROC). The calibration of the model was interrogated using the Hosmer-Lemeshow test for Goodness of Fit. RESULTS A total of 135 (0.95%) patients developed DSWI. Although there was a statistically significant difference in the calculated risk of patients who contracted DSWI (0.44% ± 0.01) vs those who did not (0.28% ± 0.00, P < 0.0001), the AUROC of 0.699 (95% confidence interval: 0.6522-0.7414) denoted a modest discriminatory power, with the Hosmer-Lemeshow Goodness of Fit statistic (P < 0.001) suggesting poor calibration. A risk-adjusted modifier improved the calibration (P = 0.08). CONCLUSIONS The STS risk calculator lacks adequate discriminatory power for estimating the isolated risk of developing deep sternal wound infection in a UK population. The discrimination is similar to the tools validation c-statistic and may have a place in an integrated calculator.

Long-Term Survival and Freedom From Reintervention After Off-Pump Coronary Artery Bypass GraftingClinical Perspective

Background: The long-term outcomes of off-pump coronary artery bypass grafting (CABG) are the subject of speculation. Our institution has >15 years of experience performing CABG both off-pump (OPCAB) and on cardiopulmonary bypass (CPB). Our null hypothesis was that there would be no difference in a long-term composite of death and revascularisation between the 2 methods. Methods: We performed a retrospective cohort study of all isolated CABG at our institution from 2001 to 2015. We used an intention-to-treat analysis, performing risk adjustment with adjustment for and matching to propensity score. In total, 13 226 patients had CABG: 5882 had OPCAB and 7344 had CPB, with a median follow-up of 6.2 years. Results: Of the 5882 OPCAB, 76 (1.3%) converted to CPB. One-, 5-, and 10-year survivals in each group were similar (OPCAB vs CPB: 96.7%, 87.9%, 72.1% vs 96.2%, 87.4%, 72.8%). No difference was found in long-term survival (adjusted hazards ratio [HR] 1.03; 95% confidence interval [CI]: 0.94–1.11 for OPCAB vs CPB; P=0.56) or freedom from death and reintervention (HR 0.98; 95% CI: 0.92–1.06 for OPCAB vs CPB; P=0.23). Patients receiving OPCAB had higher EuroSCOREs (median [quartiles]: 2.81 [1.53–5.57] vs 2.73 [1.51–5.22]; P=0.01), fewer grafts (mean±SD: 3.0±0.9 vs 3.3±0.9; P<0.001), but more total arterial grafting (45.9% vs 8.4%; P<0.001). OPCAB also had more trainee first operators (15.3% vs 12.5%), lower cardiac enzyme rise, shorter length of stay, and fewer complications (such as myocardial infarction). Conclusions: OPCAB is associated with similar long-term outcomes to CABG performed on CPB in our institution. Our low conversion rate to CPB, while training junior surgeons, demonstrates that OPCAB can be taught safely. The number of grafts performed between the 2 approaches is clinically comparable, if statistically different, and appears to provide equal benefits to survival and freedom from reintervention as on-pump CABG.

Should dialysis-dependent patients with upper limb arterio-venous fistulae undergoing coronary artery bypass grafting avoid having ipsilateral in situ mammary artery grafts?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether dialysis-dependent patients with upper limb arterio-venous fistulae (AVFs) undergoing coronary artery bypass grafting should avoid having ipsilateral in situ internal mammary artery (IMA) grafts. A literature search performed yielded 28 peer reviewed articles, of which 21 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. The papers identified included 478 patients, of whom 219 had in situ IMA grafts with ipsilateral upper limb arterio-venous fistulae. There was a substantial variation between the papers, from single case reports to small retrospective cohort studies, but no randomized, controlled trials. The largest retrospective study included 155 patients and followed up for up to 5 years. Methods used to determine coronary steal included clinical assessment, electrocardiogram or echocardiographic changes, Doppler ultrasound of mammary arteries and angiography. The aggregate evidence suggested that 61 of the 219 patients with ipsilateral IMA grafts developed some clinical or physiological evidence of malperfusion during the use of the AVFs for dialysis. Comparisons with the contralateral IMA suggested that 27 of the 61 patients suffered similar problems when dialysis was applied. A number of studies used controls, including in situ right internal mammary artery (RIMA) flow and patients not on dialysis. In total, 32 patients had their in situ RIMA flow measurements studied, of which none showed any statistically significant flow alteration. While further strong evidence to demonstrate long-term outcomes is required, we recommend the avoidance, where possible, of ipsilateral in situ IMA grafts in patients with an upper limb AVF. There is sufficient experimental and anecdotal evidence to suggest that steal occurs and that in some patients, this has clinical implications on both morbidity and mortality. In this scenario, the use of the contralateral mammary is strongly advocated to maximize the patency of grafts in an already high-risk population.

Left ventricular apical masses: distinguishing benign tumours from apical thrombi

Differential diagnoses for cardiac left ventricular apical masses presenting following acute myocardial infarction include thrombi and cardiac tumours. We present two such cases and the multidisciplinary assessment that is required to assist with diagnosis.

Long term and disease-free survival following surgical resection of occult N2 lung cancer

Background Despite systematic investigation with computed tomography (CT), positron emission tomography (PET)/CT, CT or magnetic resonance imaging (MRI) brain imaging and supplementary investigation using endobronchial ultrasound guided biopsy (EBUS), endo-oesophageal ultrasound guided biopsy (EUS), fine needle aspiration (FNA), mediastinoscopy or mediastinotomy, there is an approximately 10% rate of occult N2 disease identified at pathological staging. It has been hypothesised that such occult disease, too small or inactive to be identified during pre-operative multi-modality staging, may represent low volume disease that may have equivalent survival to patients with similar stage at clinical, pre-operative assessment. We compared the long-term survival and disease-free survival of patients with the same clinical TNM stage with and without occult N2 disease. Methods We retrospectively analysed a database that prospectively captured information on all patients assessed and treated for lung cancer in our surgical unit. We reviewed data on patients who underwent lung cancer surgery with curative intent between January 2006 and August 2010. Results A total of 312 lung cancer resections were performed [mean age 68 (range, 42-86) years old and male:female ratio 1.14:1]. Occult N2 disease was identified in 28 (8.7%) of 312 patients. There was no difference in the rate of N2 disease for different tumour histological types. Five-year survival with occult N2 disease was 35.8% vs. 62.5% without. Median survival was 34 months with occult N2 disease vs. 84 months without. Conclusions With contemporary staging techniques, so-called occult N2 disease, even with low volume and PET non-avid disease, does not have an indolent course and should still be considered a risk factor for poorer prognosis.

Conversion after off-pump coronary artery bypass grafting: where are the quality markers?

We read with interest the recent paper by Stevens et al. [1] describing the predictors of emergent conversion from off-pump coronary artery bypass grafting and the outcomes of those patients converted. Data came from the CORONARY trial, which has recently published 5-year outcomes between offpump and on-pump coronary artery bypass grafting, finding no difference in morbidity or mortality [2]. The overall rate of conversion was 7.9% which the authors noted was 50% higher than pooled figures from meta-analyses and nearly 4 times higher than national audit data. The elective conversion rate was 4.7% suggesting that apparently experienced off-pump surgeons were rejecting 1 in 20 patients for anatomical reasons. In two-thirds of cases, conversion was settled upon before even manipulating the heart. In such circumstances, concerns about the off-pump expertise of the surgeons should be raised. The CORONARY trial recruited 4752 patients over 5 years from 79 hospitals. This represents an average of just 12 cases per unit per year: disappointing recruitment rates for a study with relatively liberal inclusion criteria. One-third of institutions recruited less than 25 patients over 5 years. It comes as little surprise, then, that low-surgeon experience with off-pump grafting was their greatest independent predictor of conversion. The CORONARY trial employed an intention-to-treat approach to analysis, meaning that some ‘conversions’ were effectively treated as on-pump cases before the point of pericardiotomy. Less than half of cases were converted due to haemodynamic instability. In technical terms, therefore, these patients had on-pump surgery from the outset. Had these electively converted patients been randomized to on-pump surgery, they would have suffered the same complications—but for the purposes of analysis, the complications were tallied against off-pump surgery. We have previously demonstrated that matched conversions from off-pump have the same outcome as on-pump cases [3]. While the authors argued that early, prophylactic conversion is a ‘wise decision’ and safer than emergent crash onto cardiopulmonary bypass, we contend that a wiser decision still would be for surgeons inexperienced in off-pump surgery to decline participation in such trials. Per-protocol analysis found that at 1 year, off-pump surgery had better outcomes than on-pump surgery. While we agree with the authors’ recommendation that the conclusions drawn from this must not be overstated, neither should the exploratory implications be understated, as we feel they have been. Emergent conversions should be considered a failure (we prefer the term ‘complication’) of the offpump technique; but, equally, conversion prior to assessment for suitability for off-pump should not be. The CORONARY trial aimed to address some of the criticisms of the muchmaligned ROOBY trial [4] by demanding independent surgeon experience of >100 cases and >2 years. In practice, however, this did not translate to an acceptable level of expertise: neither by the standards of a ‘dedicated off-pump surgical team’ such as our own (conversions 1.3%) [5] nor by national standards from the Society of Thoracic Surgeons (conversions 2.2%). National benchmarks should be the quality marker for off-pump expertise. Whilst this study goes some way to demonstrating the real-world outcomes following off-pump surgery, a trial comparing the 2 techniques where adequate competence in off-pump is demonstrated is still awaited.