ESTIMATION OF POSTOPERATIVE CARDIAC COMPLICATIONS WITH V-POSSUM MODEL IN PATIENTS PREPARED FOR MAJOR ELECTIVE VASCULAR SURGERY

The Vascular Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity (V-POSSUM) is a vascular surgical modification of POSSUM. The aim of the study is to investigate role of V-POSSUM in estimation of major adverse cardiac events (MACE) in patents after major elective vascular surgery. We also wanted to examine relationship of various clinical and demographic data with postoperative cardiac complications. We prospectively enrolled all 122 patients prepared for major open elective vascular surgery (abdominal aortic aneurysm repair, inferior inguinal arterial reconstruction, or carotid endarterectomy). The analysis of the Kaplan-Meier curve showed that patients with a morbidity assessment of V-POSSUM score > 27 had a statistically significantly shorter time to develop cardiac complications in the first month compared to other patients (p = 0.026). Neither of clinical and demographic characteristics was not associated with postoperative cardiovascular events. V-POSSUM represents a way to improve the stratification for postoperative cardiac complications in patients prepared for major elective vascular surgery. Acta Medica Medianae 2019;58(1):39-43.


Introduction
The Vascular Physiological and Operative Severity Score for the enumeration of Mortality and Morbidity (V-POSSUM), is a vascular surgical modification of POSSUM in which the original developers examined 62 physiological parameters and used multi-variate analysis to identify the most powerful predictors of mortality.This eventually reduced the 62 to 12 physiological and 6 operative parameters.In the preoperative period only the 12 physiological parameters can be collected.The 12 physiological parameters required include age, evidence of cardiac failure (categorised based on current cardiac medication and on clinical evidence of heart failure), evidence of pulmonary disease (categorised based on severity of dyspnoea or evidence of consolidation), preoperative ECG changes (based on rate, ectopics, Qwaves and ST changes), systolic BP, resting pulse rate, Glasgow Coma Scale scoring, and serum levels of haemoglobin, white cell count, urea, sodium and potassium (1).These were placed into the online V-POSSUM calculator at www.riskprediction.org.uk to calculate individual scores.The aim of the study is to investigate role of V-POSSUM in estimation of major adverse cardiac events (MACE) in patents after major elective vascular surgery.We also wanted to examine relationship of various clinical and demographic data with postoperative cardiac complications.

Material and methods
The study was approved by the Ethics Committee of Medical Faculty University of Nis, Serbia.During 2017, we prospectively enrolled all 122 patients prepared for major open elective vascular surgery (abdominal aortic aneurysm repair, infrainguinal arterial reconstruction, or carotid endarterectomy) in Clinic for Cardiovascular and Transplantation Surgery, Clinical Center Niš, Niš, Serbia.Exclusion criteria were: 1) patients younger than 21 years, 2) unstable coronary disease and 3) decompensated heart failure.All procedures were performed during general anesthesia.All patients initially underwent detail evaluation of medical history, physical examination, routine hematologic and biochemical blood analysis, 12-lead electrocardiogram, and chest radiography.We used online risk calculator software for V-POSSUM (http://www.riskprediction.org.uk/vascindex.php).During the 30-days after the procedure, major adverse cardiac events such as: myocardial infarction, ventricular arrhythmias, decompensating heart failure, and new onset atrial fibrillation were recorded.

Statistical analysis
The obtained data are entered into the database, arranged by tables and shown graphically.As part of descriptive statistics, data are presented in the form of arithmetic mean and standard deviation, median and interquartile differences, minimum and maximum values, or in the form of absolute or relative numbers.Testing of the normality of data is carried out by Kolmogorov-Smirnov test.For the com-parison of two groups of data, if a normal distribution was satisfied, a t-test was used, if the data distribution was not normal, Mann-Whitney's U test was used.For the comparison of three or more data sets, if the normal distribution was satisfied, ANOVA was used, and the Tukey test was used as a post hoc analysis.If the normal distribution was not satisfied when comparing three or more data sets, a Kruskal-Wallis test was used, in which case Mann-Whitney's U test was used as a post hoc analysis.To compare the attributes, a Hi-square test, or Fisher's Exact Probability Test, was used.Statistical data processing was carried out in the SPSS 16.0 program package (SPSS Inc., Chicago, Ill., USA).Statistical significance was determined for a p value of less than 0.05.
The analysis of the Kaplan-Meier curve showed that patients with a morbidity assessment of V-POSSUM score > 27 had a statistically significantly shorter time to develop cardiac complications in the first month compared to other patients (p = 0.026) (Table 5).

Discussion
V-POSSUM is a more reliable model then original POSSUM in the stratification of patients in vascular surgery (1).Its importance is known in the prediction of short-term mortality in elective and urgent major vascular surgery (2,3).In this study, we wished to examine the role of V-POSSUM in the estimation of MACE.However, there is no unique definition of MACE.We define MACE as a large group of cardiovascular morbidities unlike in other definitions.Earlier our concern was to describe geographic variations in the accuracy of this model (4).We assumed that such good model characteristics in the prediction of mortality would have to be reflected in the assessment of postoperative cardiac complications.Neither of clinical and demographic characteristics was associated with postoperative cardiovascular events.A part of this group is independent predictors of major cardiac events, except renal failure, which is incorporated in Revised Cardiac Risk Index (RCRI).In this study, we could not determine the statistical significance of these factors.We consider it due to the fact that: 1) RCRI had a lower discriminatory potential for adverse cardiac events estimation; 2) narrow definition of MACE; 3) there was less than a quarter major vascular surgery patients (5).In this study, the patients with V-POSSUM > 27 had significantly shorter time to cardiovascular complications during the first month.A study that included a similar number of respondents as ours, in open elective abdominal aortic aneurysm repair, showed V-POSSUM as a valuable tool in stratification for MACE defined as a non-fatal myocardial infarction and cardiac death (6).

Conclusion
V-POSSUM represents a way to improve the stratification for postoperative cardiac complications in patients prepared for major elective vascular surgery.

Table 1 .
Clinical characteristics

Family history of cardiac diseases 49
40.2 Graph 1. Representation of operative procedures

Table 2 .
Cardiac complications during first month

Table 3 .
Relation of cardiac and demographic characteristics with postoperative cardiac complications in first postoperative month

Table 4 .
Impact of type of the surgery

Table 5 .
Kaplan-Meier's curve of survival after cardiac complications in the first month compared to V-POSSUM values > 27