ORIGINAL ARTICLE Year : 2022  |  Volume : 9  |  Issue : 5  |  Page : 385-390

Comparative study of cardiac risk indices to predict perioperative cardiovascular outcome in patients with peripheral vascular diseases

Vivek Kumar Singh1, Sudhir Rai2, Vembu Anand3, Nitu Singh4
1 Department of Vascular Surgery, Command Hospital, Chandi Mandir, Haryana, India
2 GM Medical Services, Tata Steel Ltd, Professor Surgery & Vascular Surgery, Department of Surgery, Jamshedpur, Jharkhand, India
3 Professor Surgery and Vascular Surgery, Department of Surgery, Command Hospital, Lucknow, Uttar Pradesh, India
4 Department of ENT, Command Hospital, Pune, Maharashtra, India

Date of Submission05-Sep-2022Date of Acceptance18-Oct-2022Date of Web Publication13-Jan-2023

Correspondence Address:
Dr. Nitu Singh
Department of ENT, Command Hospital, Pune, Maharashtra
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/ijves.ijves_59_22

Introduction: Existing methodologies and risk stratification indices for predicting peri-operative cardiac complications in vascular surgery patient lack sufficient predictive value and therefore cannot be recommended for risk stratification. There are no Indian studies for preoperative cardiac risk scores for patients who undergo vascular and endovascular procedures. Therefore, an attempt was made to risk stratify and compare two existing cardiac risk indices (i.e., Detsky's modified cardiac risk index vs. Revised cardiac risk index [RCRI]) to predict peri-operative morbidity and mortality due to cardiac causes. The aim of this study: (a) To compare Detsky's modified cardiac risk index and RCRI to predict perioperative cardiovascular outcome in patients with peripheral vascular disease undergoing surgical intervention. (b) To predict perioperative cardiovascular outcome based on cardiac risk index in patients with peripheral vascular disease undergoing surgical intervention. Materials and Methods: This is an observational, prospective, longitudinal, controlled cohort study, which assessed 103 patients admitted at vascular centre for a period of 2 years. All patients undergoing vascular surgical procedure and evaluated by a cardiologist in the preoperative period were included in the study. Results: Eighteen patients (17.4%) had cardiac complications. The Detsky's index was found to be a satisfactory predictor of postoperative cardiac events (P < 0.001) as compared to RCRI which had a P < 0.003. There were a total of 10 mortalities (9.7%). Detsky's model and RCRI had positive predictive value (PPV) of 73.3% and 31.4%, specificity of 94.1% and 72.7%, respectively. Discussion: The overall sensitivity, specificity, PPV, negative predictive value of the Detsky's risk index, and RCRI in the prediction of cardiac events were 31.4%, 94.1%, 73.3%, 72.7% and 73.3%, 72.7%, 31.4%, 94.1%, respectively. In our study, the area under ROC for Detsky class was 0.76 versus 0.75 and superior to C statistic. However, the area under ROC for RCRI class was 0.72 versus 0.75 and inferior to C statistic. One important inference from the study was that 77.6% patients were smoker in the study group which emphasize the direct relation of peripheral vascular disease with smoking. Conclusion: The study concluded that patients with good surgical risk and profile undergoing minor vascular procedures can be operated without further testing. For other patients, the next step would be to incorporate the Detsky index. A Detsky score of 20 or more is comparable to a major clinical predictor in the American College of Cardiology/American Heart Association scheme.

Keywords: American College of Cardiology/American Heart Association Guidelines, cardiac risk index, Detsky's cardiac risk index, major adverse cardiac events, revised cardiac risk index

How to cite this article:
Singh VK, Rai S, Anand V, Singh N. Comparative study of cardiac risk indices to predict perioperative cardiovascular outcome in patients with peripheral vascular diseases. Indian J Vasc Endovasc Surg 2022;9:385-90
How to cite this URL:
Singh VK, Rai S, Anand V, Singh N. Comparative study of cardiac risk indices to predict perioperative cardiovascular outcome in patients with peripheral vascular diseases. Indian J Vasc Endovasc Surg [serial online] 2022 [cited 2023 Jan 14];9:385-90. Available from: https://www.indjvascsurg.org/text.asp?2022/9/5/385/367722   Introduction 

Vascular surgery patients undergoing noncardiac procedures have high risk for major cardiac events and leading cause of death. Approximately 40 million surgical procedures performed annually in Europe have postoperative myocardial infarction (MI) rate of 1% (400,000) and a cardiovascular mortality rate of 0.3% (133,000).[1] The noncardiac surgeries have the incidence of 6.2% for cardiac events.[2] Hertzer et al. published reports of 1000 patients in 1984 in a landmark study. These patients underwent noncardiac vascular surgery. It was observed that 61% of the patients had at least one coronary artery with a stenosis of 50% or more.[3] US studies have shown similar data, with 1 million of the 27 million patients undergoing surgery in the US per year having cardiac complications.[4]

The high prevalence of coronary artery disease (CAD) in vascular surgical patients is a major risk factor for perioperative cardiac events. There are guidelines which emphasize the need for an accurate clinical assessment, identifying the clinical markers of increased perioperative cardiovascular risk, suggesting the use of cardiac risk indices.[5] Additional examinations or procedures, such as exercise or pharmacological stress tests, ambulatory electrocardiographic control, and coronary angioplasty, have failed to show a substantial effect in reducing perioperative cardiac morbidity, and therefore, cardiac risk indices have been recommended only for select patients.[5],[6] Ninety percent vascular surgery patients do not benefit by these tests, and therefore, critical assessment of cardiac risk index is essential.[7] There are no Indian studies for preoperative cardiac risk scores for patients who undergo vascular interventions. Therefore, a study was done at a tertiary hospital with an aim to risk stratify patients and to compare Detsky and Revised cardiac risk index (RCRI) cardiac risk index to predict cardiac events.

  Materials and Methods 

This is an observational, prospective, longitudinal, controlled study, which assessed 103 patients at a single center from February 2013 to June 2015. Patient data on demographics, lifestyle, comorbidity, and other variables were obtained as shown in [Table 1], [Table 2], [Table 3], [Table 4].[8] Comorbidities studied included CAD, congestive heart failure, hypertension, peripheral vascular disease (revascularization/amputation for peripheral vascular disease and rest pain in lower extremity), sepsis, neurological event, or disease. Patient distribution who were at higher risk for peri-operative cardiac events was also studied, as shown in [Table 5]. All patients underwent cardiology evaluation and their distribution is shown in [Table 6]. The study variables also included type of surgery, incidence and type of complications, risk stratification according to the Detsky's cardiac risk index[9] and RCRI as shown in [Table 7] and [Table 8]. Preoperative cardiac risk scoring was done for each patient based on Detsky's modified cardiac risk index and RCRI. In RCRI, one point each was assigned to the six variables and the patient was classified into Class I, II, III, and IV with perioperative risk of 0.4%, 0.9%, 6.6%, and 11%, respectively. In Detsky's risk index, patient based on scores was classified into Class I, II, and III with the perioperative of low, intermediate, and high risk. The scorings were calculated and compared for sensitivity, specificity, and predictive values. The primary study endpoints were the major adverse cardiac event (acute coronary syndrome, nonfatal MI, or cardiac death). The secondary endpoints were congestive heart failure, ventricular fibrillation, supraventricular arrhythmias; ventricular arrhythmias; arterial hypotension, or hypertension. The categorical variables were expressed according to their frequencies (number and percentage) and analyzed using the Chi-square test. To determine the accuracy of stratification for Detsky's index, the area under the receiver operating characteristic (ROC) curves was also calculated.

Table 5: Distribution of patients at higher risk for peri-operative cardiac events

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Statistical analysis

The categorical variables were expressed according to their frequencies (number and percentage) and analyzed using the Chi-square test. When the expected values were <5, the Fisher's exact test was used. The statistical significance value of P < 0.05 was adopted.

To determine and compare the accuracy of different systems of stratification for each index, the areas under the ROC curves were calculated. The ROC curves were plotted on a graph with the values of sensitivity in the ordinate axis, and the proportion of false positives (1-specificity) in the abscissa axis. With regard to the interpretation of the ROC curve, the greater the area under the curve, more accurate the cardiac risk index was considered. The areas were compared using a nonparametric method according to the technique by Hanley and McNeil 49 (expected sensitivity between 60% and 75%). In our study, the area under the ROC curve for Detsky's risk index was 0.76 with 95% confidence interval and in RCRI was 0.72 with 95% confidence interval.

  Results 

The age of the study population ranged from 32 to 81 years consisting of 90 men and 13 women, as shown in [Table 1] and [Table 2]. There were 56 patients with critical limb ischemia and 16 had aneurysmal disease, both thoracic and abdominal. Five patients had carotid artery disease. Patients with occlusive disease had disabling claudication or rest pain, as shown in [Table 4]. The left ventricular ejection fraction (LVEF) ranged from 25% to 60%. Eighty-four patients had LVEFs of >50%, and 14 had LVEFs of 50% or less with postoperative cardiac complications in six patients (42.8%). Sixty-seven had healthy myocardial wall motion, and 14 showed wall motion abnormalities out of which five had perioperative cardiac complications (35.7%). Seventeen out of 18 postoperative cardiac complications occurred in patients above 40 years and the mean risk of cardiac complication or cardiac death was 7.6%. Acute MI occurred in 0.02% while cardiac death in 7.7% as shown in [Figure 1]. Eighty patients were smokers who had peripheral arterial disease (77.6% of the study population). There were three females in the study group, of which 1 was a chronic smoker.

Figure 1: Percentage distribution of patients developing cardiac events. (1) Grey 82% (nil complications); (2) pink 1% (pulmonary edema); (3) light blue 1% (myocardial infarction) (4) light green 2% (hypotension); (5) sky blue 1% (hypertension); (6) yellow 8% (cardiac arrest); (7) dark grey 1% (angina); (8) orange 3% (acute coronary events); (9) blue1% (accelerated hypertension)

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All three female patients were suffering from ischemic heart disease. High altitude-induced thrombosis was present in six patients (5% of study population).

The patients were classified according to Detsky's cardiac risk index into Class I (n = 88, low risk), Class II (n = 12, moderate risk), and Class III (n = 3, high risk), as shown in [Figure 2] and [Figure 3]. The patients were classified according to RCRI into Class I (n = 39), Class II (n = 29), Class III (n = 22), and Class IV (n = 13), as shown in [Figure 3]. Twenty-one patients underwent aortic, 47 patients underwent peripheral arterial surgeries, and 32 patients underwent endovascular procedures, as shown in [Table 7]. Twenty-six patients had to undergo emergency surgery as a limb/life-saving procedure. There were six mortalities in the emergency group (23% mortality in the emergency group), whereas 77 patients underwent elective procedures with three mortalities in the group (3.8% mortality in the elective group). Ten patients had surgical complication postoperatively, but nil mortality occurred due to these complications. Eighty-two percent of patients did not have any complications.

However, there was 9.7% mortality. The various major/minor cardiac events and their distributions are shown in [Figure 1]. Cardiac death averaged 1.94% in Detsky's class in high-risk group, 3.8% in intermediate-risk group, and 3.8% in low-risk group, as shown in [Table 9].

Cardiac death in RCRI was 1.94% in Class I and II, 0.97% in Class III and 4.85% in Class IV as shown in [Table 10].

Table 10: Postoperative cardiac events in Class revised cardiac risk index

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Sensitivity, specificity, and positive and negative predictive values (NPV) were calculated according to Fletcher et al.[10] The overall sensitivity, specificity, positive predictive value (PPV), NPV of the Detsky's risk index and RCRI in the prediction of cardiac events were 31.4%, 94.1%, 73.3%, 72.7% and 73.3%, 72.7%, 31.4%, 94.1%, respectively, as shown in [Table 11]. In our study, the area under ROC for Detsky class was 0.76 versus 0.75 and superior to C statistic. However, the area under ROC for RCRI class was 0.72 versus 0.75 and inferior to C statistic, as shown in [Table 12].

Table 11: Overall sensitivity, specificity, positive predictive and negative predictive values

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  Discussion 

The complexity of the surgical procedure may be, in and of itself, the most important predictive factor for postoperative morbidity in many patients.[11] Cardiac risk may be stratified according to the type of surgical procedure to be performed. The length and type of surgery have a significant influence on the risk of perioperative cardiac complications.[12],[13] By definition, cardiac death or nonfatal MI average is greater than 5% in high risk surgical procedures, between 1% and 5% in intermediate risk procedures, and <1% in low risk procedures.[14] In our study, cardiac death or nonfatal MI averaged 5.8% in RCRI and 2.9% in Detsky's class in high risk group, 2.9% in RCRI and 3.8% in Detsky's class in intermediate risk, and 1.9% in RCRI and 3.8% in Detsky's class in low risk procedures as mentioned in [Table 9] and [Table 10].

The sensitivity of the risk index in the prediction of cardiac events was 73.3% in RCRI class, while in Detsky's class it was 31.4%. The specificity was 72.7% in RCRI class, and 94.1% in Detsky's class, the PPV in RCRI class was 31.4%, and the NPV was 94.1%. The PPV in Detsky's class was 73.3% and NPV was 72.7%. In high risk patients, Detsky risk index had higher specificity and PPVs (100%) when compared with RCRI.

Although many previous risk stratification tools exist, they have several limitations. RCRI, the most widely used risk index, was derived and validated on a relatively small cohort of 4315 patients in contrast to more than 400, 000 patients in the original study.[15]

Despite its relative ease of use, the RCRI lacks in its discriminative/predictive ability. It has been widely suggested that the discriminative ability of a risk index should be >0.8 for a prediction model to be considered clinically relevant.[16],[17]

The ROC area under the curve for RCRI, which represents discriminative ability, was 0.76 in the original study by Lee et al.[15] and 0.75 in a review by Ford et al.[18] which makes its discriminative ability only moderate. The C statistic for RCRI was lower in our study (0.72 versus 0.75). Therefore, based on ROC curve too, Detsky had higher predictive value than RCRI.

One important inference from the study was that 77.6% of patients were smoker in the study group which emphasize direct relation of peripheral vascular disease with smoking. There was 23% mortality in emergency group as compared to 3.8% in elective group. Emergency group posed significant risk in terms of mortality because of lesser optimization of patients in view of major life-and limb-saving surgeries. These data suggest the importance of relevant cardiac risk assessment and optimization of patients before taken up for interventions. The present study had some limitations. Although all patients were subjected to baseline echocardiography to risk stratify by cardiologist, patients with preoperative high risk were not routinely evaluated with further coronary angiography or stress myocardial perfusion imaging (MPI). Three patients were high-risk group, and none underwent stress MPI or coronary angiography. This dichotomy existed because few of the patients were taken up for emergency surgeries without further cardiac evaluation.

  Conclusion 

The study concluded that perioperative cardiac morbidity and mortality is an important factor in patients undergoing noncardiac vascular surgery. Therefore, cardiac risk assessment provides a framework for determining a patient's surgical risk and prognosis. The assessment of risk factors is essential for surgery, since in this context, it is possible to plan the procedure, in terms of both the decision to perform surgery and the possibility of taking other measures to minimize the risk of cardiac complications. In high-risk patients, if the surgery is not an emergency, there is an opportunity to consider the proper evaluation before the procedure or performing a lower risk intervention. Any interventional procedure should be undertaken with appropriate perioperative surveillance. Our study concludes with recommendation that Detsky's risk index and American College of Cardiology/American Heart Association guidelines for preoperative cardiac risk assessment should be included in the institutional protocol for peripheral vascular surgery.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 

  References 
1.Poldermans D, Hoeks SE, Feringa HH. Pre-operative risk assessment and risk reduction before surgery. J Am Coll Cardiol 2008;51:1913-24.  
    2.Mangano DT, Goldman L. Preoperative assessment of patients with known or suspected coronary disease. N Engl J Med 1995;333:1750-6.  
    3.Hertzer NR, Beven EG, Young JR, O'Hara PJ, Ruschhaupt WF 3rd, Graor RA, et al. Coronary artery disease in peripheral vascular patients. A classification of 1000 coronary angiograms and results of surgical management. Ann Surg 1984;199:223-33.  
    4.Devereaux PJ, Ghali WA, Gibson NE, Skjodt NM, Ford DC, Quan H, et al. Physician estimates of perioperative cardiac risk in patients undergoing noncardiac surgery. Arch Intern Med 1999;159:713-7.  
    5.Guidelines for assessing and managing the perioperative risk from coronary artery disease associated with major noncardiac surgery. American College of Physicians. Ann Intern Med 1997;127:309-12.  
    6.Eagle KA, Brundage BH, Chaitman BR, Ewy GA, Fleisher LA, Hertzer NR, et al. Guidelines for perioperative cardiovascular evaluation for noncardiac surgery. Report of the American college of cardiology/American heart association task force on practice guidelines. Committee on perioperative cardiovascular evaluation for noncardiac surgery. Circulation 1996;93:1278-317.  
    7.Gilbert K, Larocque BJ, Patrick LT. Prospective evaluation of cardiac risk indices for patients undergoing noncardiac surgery. Ann Intern Med 2000;133:356-9.  
    8.Heinisch RH, Barbieri CF, Nunes Filho JR, Oliveira GL, Heinisch LM. Prospective assessment of different indices of cardiac risk for patients undergoing noncardiac surgeries. Arq Bras Cardiol 2002;79:327-38.  
    9.Detsky AS, Abrams HB, Forbath N, Scott JG, Hilliard JR. Cardiac assessment for patients undergoing noncardiac surgery. A multifactorial clinical risk index. Arch Intern Med 1986;146:2131-4.  
    10.Fletcher RH, Fletcher SW, Wagner EH. Treatment. In: Fletcher RH, Fletcher SW, Wagner EH, editors. Clinical Epidemiology – Scientific Bases of Medical Conduct. 2nd ed. Porto Alegre: Medical Arts; 1989. p. 187.  
    11.Ackland GL, Harris S, Ziabari Y, Grocott M, Mythen M, SOuRCe Investigators. Revised cardiac risk index and postoperative morbidity after elective orthopaedic surgery: A prospective cohort study. Br J Anaesth 2010;105:744-52.  
    12.Freeman WK, Gibbons RJ. Perioperative cardiovascular assessment of patients undergoing noncardiac surgery. Mayo Clin Proc 2009;84:79-90.  
    13.Troncoso C. Evaluación preoperatoria: Preoperative evaluation. Rev Méd Clín Condes 2011;22:340-9.  
    14.Ochoa Montes LA, González Lugo M, Tamayo Vicente ND, Romero del Sol JM, Correa Azahares DP, Miguélez Nodarse R, et al. La lesión aterosclerótica en la muerte súbita cardíaca. Rev Habanera Cienc Méd 2010;9:303-12.  
    15.Lee TH, Marcantonio ER, Mangione CM, Thomas EJ, Polanczyk CA, Cook EF, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation 1999;100:1043-9.  
    16.Ohman EM, Granger CB, Harrington RA, Lee KL. Risk stratification and therapeutic decision making in acute coronary syndromes. JAMA 2000;284:876-8.  
    17.Harrell FE Jr., Califf RM, Pryor DB, Lee KL, Rosati RA. Evaluating the yield of medical tests. JAMA 1982;247:2543-6.  
    18.Ford MK, Beattie WS, Wijeysundera DN. Systematic review: Prediction of perioperative cardiac complications and mortality by the revised cardiac risk index. Ann Intern Med 2010;152:26-35.  
    
  [Figure 1], [Figure 2], [Figure 3]
 
 
  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11], [Table 12]