Development and Validation of Elective and Nonelective Risk Prediction Models for In-Hospital Mortality in Proximal Aortic Surgery Using the National Institute for Cardiovascular Outcomes Research (NICOR) Database

Risk score for arch reconstruction under circulatory arrest with hypothermia: The ARCH score

OBJECTIVE

Currently, there is no risk scores built to predict risk in thoracic aortic surgery. This study aims to develop and internally validate a risk prediction score for patients who require arch reconstruction with hypothermic circulatory arrest.

METHODS

From 2002 to 2018, data for 2270 patients who underwent aortic arch surgery in 12 institutions in Canada were retrospectively collected. The outcomes modeled included in-hospital mortality and a modified Society of Thoracic Surgeons-defined composite for mortality or major morbidity. Multivariable logistic regression using least absolute shrinkage and selection operator selection method and mixed-effect regression model was used to select the predictors. Internal calibration of the final models is presented with an observed-versus-predicted plot.

RESULTS

There were 182 in-hospital deaths (8.0%), and the incidence of Society of Thoracic Surgeons-defined composite for mortality or major morbidity was 27.9%. Variables that increased risk of mortality are age, chronic obstructive pulmonary disease, atrial fibrillation, peripheral vascular disease, New York Heart Association class ≥III symptoms, acute aortic dissection or rupture, use of elephant trunk, concomitant surgery, and increased cardiopulmonary bypass time, with median c-statistics of 0.85 on internal validation. The c-statistics was 0.77 for the model predicting Society of Thoracic Surgeons-defined composite. Internal assessment shows good overall calibration for both models.

CONCLUSIONS

We developed and internally validated a risk score for patients undergoing arch surgery requiring hypothermic circulatory arrest using a multicenter database. Once externally validated, the ARCH (Arch Reconstruction under Circulatory arrest with Hypothermia) score would allow for better patient risk-stratification and aid in the decision-making process for surgeons and patient prior to surgery.

Temperature analysis of aortic repair with hypothermic circulatory arrest to quantify the injury by cooling

OBJECTIVES

We analyzed the temperature in proximal aortic repair with moderate hypothermic circulatory arrest (HCA) and evaluated the effect of the cooling status on postoperative outcomes.

METHODS

A total of 340 patients who underwent elective ascending aortic replacement or total arch replacement with moderate HCA from December 2006 to January 2021 were studied. The change in body temperature trends recorded during surgery was shown graphically. Several parameters, such as the nadir temperature, cooling speed and the degree of cooling (cooling area), which was the area under curve of inverted temperature trends from cooling to rewarming as calculated by the integral method, were analyzed. The relationships between these variables and a major adverse outcome (MAO) postoperatively defined as prolonged ventilation (>72 h), acute renal failure, stroke, reoperation for bleeding, deep sternal wound infection or in-hospital death were evaluated.

RESULTS

An MAO was observed in 68 patients (20%). The cooling area was larger in the MAO group than in the non-MAO group (1668.7 vs 1383.2°C min; P < 0.0001). A multivariate logistic model showed that old myocardial infarction, peripheral vascular disease, chronic renal dysfunction, cardiopulmonary bypass time and the cooling area were independent risk factors for an MAO (odds ratio = 1.1 per 100°C min; P < 0.001).

CONCLUSIONS

The cooling area, which indicates the degree of cooling, shows a significant relationship with an MAO after aortic repair. This finding indicates that the cooling status with HCA can affect clinical outcomes.

Subjective assessment underestimates surgical risk: On the potential benefits of cardiopulmonary exercise testing for open thoracoabdominal repair

Background

Initial clinical evaluation (ICE) is traditionally considered a useful screening tool to identify frail patients during the preoperative assessment. However, emerging evidence supports the more objective assessment of cardiorespiratory fitness (CRF) via cardiopulmonary exercise testing (CPET) to improve surgical risk stratification. Herein, we compared both subjective and objective assessment approaches to highlight the interpretive idiosyncrasies.

Methods

As part of routine preoperative patient contact, patients scheduled for major surgery were prospectively “eyeballed” (ICE) by two experienced clinicians before more detailed history taking that also included the American Society of Anesthesiologists score classification. Each patient was subjectively judged to be either “frail” or “not frail” by ICE and “fit” or “unfit” from a thorough review of the medical notes. Subjective data were compared against the more objective validated assessment of postoperative outcomes using established CPET “cut‐off” metrics incorporating peak pulmonary oxygen uptake, V̇O_2PEAK at the anaerobic threshold (V̇O₂‐AT), and ventilatory equivalent for carbon dioxide that collectively informed risk stratification. These data were retrospectively extracted from a single‐center prospective National Health Service database. Data were analyzed using the Chi‐square automatic interaction detection decision tree method.

Results

A total of 127 patients were examined that comprised 58% male and 42% female patients aged 69 ± 10 years with a body mass index of 29 ± 7 kg/m². Patients were poorly conditioned with a V̇O_2PEAK almost 20% lower than predicted for age, sex‐matched healthy controls with 35% exhibiting a V̇O₂‐AT < 11 ml/kg/min. Disagreement existed between the subjective assessments of risk with ∼34% of patients classified as not frail on ICE were considered unfit by notes review (p < .0001). Furthermore, ∼35% of patients considered not frail on ICE and ∼31% of patients considered fit by notes review exhibited a V̇O₂‐AT < 11 ml/kg/min, and of these, ∼28% and ∼19% were classified as intermediate to high risk.

Conclusions

These findings highlight the interpretive limitations associated with the subjective assessment of patient frailty with surgical risk classification underestimated in up to a third of patients compared to the validated assessment of CRF. They reinforce the benefits of a more objective and integrated approach offered by CPET that may help us to improve perioperative risk assessment and better direct critical care provision in patients scheduled for “high‐stakes” surgery including open thoracoabdominal aortic aneurysm repair.

On-line risk prediction models for acute type A aortic dissection surgery: validation of the German Registry of Acute Aortic Dissection Type A score and the European System for Cardiac Operative Risk Evaluation II

OBJECTIVES

The German Registry of Acute Aortic Dissection Type A (GERAADA) on-line score calculator to predict 30-day mortality in patients undergoing surgery for acute type A aortic dissection (ATAAD) was recently launched. Using the European System for Cardiac Operative Risk Evaluation II (EuroSCORE II), it is also possible to predict operative mortality for the same type of surgery. The goal of our study was to validate the prediction accuracy of these 2 on-line risk prediction models.

METHODS

Prospectively collected data for EuroSCORE II risk factors as well as all data for GERAADA scoring were extracted from an institutional database for 147 patients who underwent surgery for ATAAD between April 2018 and April 2021. The discriminative power was assessed using area under the receiver operating characteristic curve. The calibration of the models was tested by the Hosmer-Lemeshow statistics and by using the observed-to-expected (O/E) mortality ratio with the 95% confidence interval.

RESULTS

The observed operative mortality was 14.3%. The mean predicted mortality rates for the GERAADA score and the EuroSCORE II were 15.6% and 10.6%, respectively. The EuroSCORE II discriminative power (area under the curve = 0.799) significantly outperformed the discriminatory power of the GERAADA score (area under the curve = 0.550). The Hosmer-Lemeshow statistics confirmed good calibration for both models (P-values of 0.49 and 0.29 for the GERAADA score and the EuroSCORE II, respectively). The O/E mortality ratio certified good calibration for both scores [GERAADA score (O/E ratio of 0.93, 95% confidence interval: 0.53-1.33); EuroSCORE II (O/E ratio of 1.35, 95% confidence interval: 0.77-1.93)].

CONCLUSIONS

The EuroSCORE II has better discriminative power for predicting operative mortality in ATAAD surgery than the GERAADA score. Both scores confirmed good calibration ability.

Scoring Systems for Risk Stratification in Patients Undergoing Cardiac Surgery

Cardiac surgery is associated with significant mortality rates. Careful selection of surgical candidates is, therefore, vital to optimize morbidity and mortality outcomes. Risk scores can be used to inform this decision-making process. The European System for Cardiac Operative Risk Evaluation Score and the Society of Thoracic Surgeons score are among the most commonly used risk scores. There are many other scoring systems in existence; however, no perfect scoring system exists, therefore, additional research is needed as clinicians strive toward a more idealized risk stratification model. The purpose of this review is to discuss the advantages and limitations of some of the most commonly used risk stratification systems and use this to determine what an ideal scoring system might look like. This includes not only the generalizability of available scores but also their ease of use and predictive power.

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.

Challenges for learning health systems in the NHS. Case study: electronic health records in cardiology

Electronic health records (EHRs) are at the centre of advances in health informatics, but also many other innovations in healthcare. However, there are still obstacles to implementation and realisation of the full potential of EHRs as there are with learning health systems (LHS). Cardiovascular disease, in the UK and globally, carries greater morbidity and mortality than any other disease. Therefore, planning and delivery of health services represent major costs to individuals and populations. Both the scale of disease burden and the growing role of technology in cardiology practice make analysis of experiences with EHRs in cardiology a useful lens through which to view achievements and gaps to date. In this article regarding LHS, EHRs in cardiology are used as a case study of LHS in the NHS.

Predictive risk models for proximal aortic surgery

Predictive risk models help improve decision making, information to our patients and quality control comparing results between surgeons and between institutions. The use of these models promotes competitiveness and led to increasingly better results. All these virtues are of utmost importance when the surgical operation entails high-risk. Although proximal aortic surgery is less frequent than other cardiac surgery operations, this procedure itself is more challenging and technically demanding than other common cardiac surgery techniques. The aim of this study is to review the current status of predictive risk models for patients who undergo proximal aortic surgery, which means aortic root replacement, supracoronary ascending aortic replacement or aortic arch surgery.