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Table of Contents
ORIGINAL ARTICLE
Year : 2018  |  Volume : 7  |  Issue : 3  |  Page : 116-122

Predictors of second revascularization in patients with history of coronary artery bypass graft


1 Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran
2 Tehran Heart Center, Tehran University of Medical Sciences; Department of Community Medicine, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3 Department of Community Medicine, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
4 Tehran Heart Center, Tehran University of Medical Sciences, Tehran; Imam Ali Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran

Date of Web Publication10-Sep-2018

Correspondence Address:
Dr. Marjan Haddadi
Imam Ali Hospital, Kermanshah University of Medical Sciences, Shahid Beheshti Blvd, Kermanshah 6715847145
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/rcm.rcm_10_18

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  Abstract 


Objective: The number of individuals with a history of coronary artery bypass graft surgery (CABG) who may require a second revascularization intervention is growing. We aimed to identify the predictors of revascularization in patients with a history of CABG who were referred for conventional coronary angiography due to acute coronary syndrome (ACS) or stable angina. Methods: Data of 536 patients (74% males) who had a previous history for CABG and were referred for coronary angiography due to ACS or stable angina were included in the study. Demographic, clinical, diagnostic, and angiographic characteristics of the patients were retrieved from our institutional databank and patient's records. Based on the final recommendation, the patients were divided into two groups for either medical treatment or revascularization and compared for the study variables as well as identifying the predictive factors for the second revascularization. Results: From a total of 536 patients, 194 (36.1%) patients were advised to continue medical therapy, and the rest were referred for revascularization (repeat CABG or percutaneous coronary intervention). Elapsed time after CABG for <1 year or >10 years (P = 0.016), use of diuretics (P = 0.002), and presenting in an inpatient setting (P = 0.009) were significant predictors for the feasibility of second revascularization treatment, using multiple regression analysis. Conclusion: Elapsed time after CABG and some other clinical factors can predict the feasibility of the second revascularization in patients with a history of CABG and new onset of cardiac symptoms.

Keywords: Coronary artery bypass graft, predictor, restenosis, revascularization


How to cite this article:
Davoodi G, Shafiee A, Jalali A, Haddadi M. Predictors of second revascularization in patients with history of coronary artery bypass graft. Res Cardiovasc Med 2018;7:116-22

How to cite this URL:
Davoodi G, Shafiee A, Jalali A, Haddadi M. Predictors of second revascularization in patients with history of coronary artery bypass graft. Res Cardiovasc Med [serial online] 2018 [cited 2018 Nov 18];7:116-22. Available from: http://www.rcvmonline.com/text.asp?2018/7/3/116/240984




  Introduction Top


Atherosclerotic coronary artery disease (CAD) is a growing phenomenon in the world, and coronary artery bypass graft surgery (CABG) is a standard treatment in prolonging survival and relieving angina of patients with CAD.[1] CABG provides acceptable results in the short-term and mid-term management of CAD patients.[2] Due to the increase in the life expectancy, the number of individuals with a history of CABG who may require a second revascularization intervention is growing.[3] This is apart from early occlusion that happens in around 7%-15% of the patients before discharge from hospital following CABG surgery.[4] Atherosclerosis is the main reason for restenosis after 1 year, and dyslipidemia is known as a risk factor for restenosis. In a cohort of CABG patients in Iceland, the rate of secondary revascularization was 6.2%,[5] but this incidence may vary based on the regional, institutional, and individual characteristics.

The second revascularization is accompanied by a greater morbidity and mortality in patients who have previously undergone CABG.[6] Although catheter-based interventions are used for revascularization in patients with previous CABG, this treatment is still challenging as most of these patients are elderly people with comorbid conditions.[1],[7],[8] Furthermore, the risk of recurrent events following percutaneous coronary intervention (PCI) in patients with prior CABG is higher than non-CABG patients.[9] Moreover, several other conditions can accelerate restenosis, such as opium abuse [10] and left ventricular dysfunction.[11] Therefore, providing long-term patency of grafted vessels and identification of predictive factors for this patency is an important issue in clinical practice.

In the present study, we aimed to identify predictors of the feasibility of the second revascularization in patients with a history of CABG who referred to our center for conventional coronary angiography due to acute coronary syndrome (ACS) or stable angina.


  Methods Top


In this retrospective study, patients who had a previous history for CABG and referred again for coronary angiography due to ACS or stable angina between 2010 and 2013 were included. The inclusion criteria were performing CABG alone for the 2nd time within the study period. The exclusion criteria were incomplete data files. All patients gave a written consent at the time of admission to allow the use of their clinical data for medical research. The protocol of this study was confirmed by the board of Research and Ethical Committee of our Center (THCR-162, March 2012).

Demographic, clinical, and angiographic characteristics of the patients were retrieved from the databank of Tehran Heart Center and patient's records and were then prepared for analysis.[12] Furthermore, data of the exercise tolerance test (ETT) or myocardial perfusion imaging (MPI) before performing coronary artery angiography were recorded, in case it was done. Results of the coronary angiography were checked by reviewing the patients' film from the archive of our center by a cardiologist who was blinded to this study, and the reports were used for this study. Based on the results of coronary angiography, occlusion or stenosis was observed in native arteries, saphenous vein grafts (SVG), left internal mammary artery (LIMA), right internal mammary artery (RIMA), or radial artery anastomoses.

According to the coronary angiography, patients were advised to either continue medical therapy or undergo the second revascularization. The recommendation was made based on the physician's decision regarding the clinical profile of every individual patient. The second revascularization could be CABG or PCI, and the decision for revascularization was made by the treating physician and consulting surgeon. The patients were divided into two groups based on the final recommendation and compared for the study variables as well as identifying the predictive factors for the second revascularization.

Statistical analysis

The data are expressed as frequency and percentage for categorical variables. Chi-squared or Fisher's exact test was applied to compare categorical variables between groups of the final recommendation. Continuous variables are described as mean with standard deviation and median with interquartile range boundaries when the data were skewed and not normally distributed. The normality or the skewness of the data was evaluated using histograms and box plots as well as mentioned descriptive statistics. Comparison of continuous variables between final recommendation groups was made using Student's t or Mann–Whitney U-test. The multiple logistic regression with the backward elimination method (with probabilities of removal and entry equal to 0.1 and 0.05, respectively) was used to find the multiple predictors of the final recommendation. Variables with a P < 0.15 in the univariate analyses were a candidate to enter the multivariable model. The effect of the covariates on the final recommendation as the outcome was reported through odds ratio with 95% confidence interval (CI). Calibration of the model was tested using the Hosmer-Lemeshow goodness of fit test. The discrimination power of the model was measured using the c-statistic which is equivalent to the area under the receiver operating characteristic (ROC) curve. Data analyses were performed using the SPSS statistical software version 20 (SPSS Inc., Chicago, IL, USA).


  Results Top


Data of a total of 536 patients (age = 55.9 ± 9.1 years; 74% males) were reviewed in this study after excluding 19 patients with incomplete data. Seventy-six (14.2%) patients were evaluated by ETT and 96 (17.9%) patients by MPI. ETT was positive in 55 (76%) patients (age = 54.5 ± 8.4 years) and MPI was positive in 91 (96%) patients (age = 55.6 ± 9.0 years). Coronary angiography revealed that SVGs were occluded in 311 (59.8%) patients (age = 55.4 ± 9.6 years) and were stenotic in 104 (20%) patients (age = 56.1 ± 8.6 years). In patients with LIMA anastomoses (n = 514) (age = 57.3 ± 8.9 years), 78 (15.1%) patients had total occlusion and 14 (2.7%) had stenosis. In patients with radial anastomosis (n = 32) (age = 56.3 ± 9.0 years), total occlusion was observed in 10 (31.2%) patients and stenosis in 2 (6.2%) patients. All of the patients with RIMA anastomosis (n = 5) had patent anastomosis. In total, 163 patients had lesion in their SVG and 92 patients had lesion in their arterial anastomosis [Table 1].
Table 1: Comparing the results of the noninvasive tests, coronary angiography, and echocardiography between the study groups

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Based on the anatomy of the coronary arteries observed in the coronary angiography and considering the medical condition of the patients, 194 (36.1%) patients were advised to continue medical therapy, and the rest were advised for the second revascularization (repeat CABG or PCI). Serum creatinine level and the frequency of diuretic use were significantly higher in patients who were advised to have medical treatment (P = 0.008 and P = 0.006, respectively). The number of patients referred in an outpatient setting was significantly higher in those who were advised to continue their medical treatment (P = 0.039). On the other hand, Time elapsed after the previous CABG was longer in patients who were advised for revascularization (P = 0.004). Comparison of the baseline study variables between the two groups is summarized in [Table 2].
Table 2: Comparison of the baseline characteristics between the study groups

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Patients were categorized into groups with 5-year intervals according to the time passed from the previous CABG. It was noticed that revascularization treatment was significantly more recommended in patients who had undergone CABG either <1 year or >10 years before [Figure 1].
Figure 1: Categorization of the patients based on the time passed from previous coronary artery bypass graft and the recommended treatment

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[Table 1] compares the results of the noninvasive test, coronary angiography, and echocardiography between the study groups. Although positive ETT or MPI result did not have any significant association with the current recommended treatment, no patient with a negative MPI was advised to do revascularization. There was also no significant difference between the groups regarding the results of the previous and current coronary angiography findings. Use of arterial grafts did not have any association with the final recommendation. In the echocardiographic evaluation, moderate mitral regurgitation was significantly more observed in the candidates for revascularization (P = 0.046). However, there was no significant difference between the groups regarding ejection fraction and tricuspid regurgitation.

The results of the regression analysis for determining the predictors of the recommended treatments showed that the elapsed time after CABG of <1 year or >10 years, use of diuretics and presenting in an inpatient setting are significant predictors for revascularization treatment [Table 3]. The area under the ROC curve for this predictive model was 64.1% (95% CI: 59.2%–69%; P < 0.001).
Table 3: Predictors of recommendation for coronary revascularization

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  Discussion Top


In this study, we found that in patients who had CABG <1 year or >10 years, use diuretics and present in an inpatient setting, the physician is more likely to recommend revascularization treatment. Recognition of the predictive factors for recommending the second revascularization in patients who undergo coronary angiography after CABG is of clinical importance. This can assist the clinicians to decide more accurately about the recommendation for revascularization or continuing medical therapy.

The occurrence of ACS and the need for reintervention is rather infrequent within the first decade following primary CABG.[13] However, the occurrence of new-onset ACS does not necessarily demand repeat revascularization, and many patients are preferred to receive medical treatment. Besides, the cost-benefit balance should also be evaluated before any decision for deciding between medical treatment and reintervention.[14] Survival of the patient, his/her life expectancy, and clinical reserve can also influence this decision as well as the patient's demographic and clinical features.

Investigation of the natural history of coronary artery stenosis following CABG has shown that the most moderately stenosed coronary arteries progress to severe stenosis or occlusion through time and this progression is more rapid in grafted arteries than nongrafted arteries.[15] On the other hand, internal thoracic grafts have been shown to have excellent patency in comparison with SVG.[15]

One of the main reasons for repeat revascularization and ACS in patients with previous CABG is early vein graft thrombosis, particularly in the 1st year following CABG.[16] Early failure commonly results from surgical problems, incomplete revascularization, or graft failure. On the other hand, late failure is a consequence of saphenous-vein graft attrition, the progression of atherosclerosis, and thereby occurrence of new stenoses in native vessels, or both.[17],[18] Graft patency after 10 years from CABG is higher in arterial grafts as compared with the vein grafts.[2] Various factors affect the vein graft patency, including older age, the location of the lesion, number of the diseased vessels, characteristics of the native target vessel, condition of the anastomosis, mean blood flow, and time since implantation.[16],[19],[20] In the present study, a majority of the patients (69.5%) had stenosis or occlusion, predominantly in their venous grafts and then the arterial anastomoses (19.4%). This shows that the new onset of ACS in patients with a history of CABG results from stenosis or occlusion of the venous graft or anastomoses, rather than the atherosclerosis of the native coronary arteries.

No randomized trials have evaluated the benefits of an invasive versus conservative strategy in patients with previous CABG so far. Nonetheless, a low threshold for angiography with a preferable intervention in native circulation, and medical treatment similar to that used in the overall population is recommended in the current guidelines.[21] Although we did not find any study on the predictors of recommendation for revascularization versus medical therapy, the most frequent predictors of the revascularization method based on other studies, arranged in the order of importance included: number of diseased grafts, number of occluded grafts, prior infarct, chronic obstructive pulmonary disease, hyperlipidemia, patent LIMA to left anterior descending artery, ejection fraction, years from previous CABG, native artery occlusion, age, unstable angina, and number diseased vessels.[22] In another study, age >70 years, ejection fraction <35%, diabetes mellitus, and recent MI were predictors for reoperation.[23]

On the other hand, the success rate of any treatment should be considered in patients with previous CABG. Results of a Japanese study showed that the success rate of secondary revascularization for chronic total occlusion using PCI in patients who had a history of CABG was significantly lower than the peers without previous CABG.[24],[25] Meanwhile, previous CABG was not an independent predictor of mortality in thrombolysis in myocardial Infarction Global Registry of Acute Coronary Events, despite its poor outcome.[26] However in another study, patients with prior CABG who underwent revascularization had a worse outcome in the long term.[9] Based on our findings, we can conclude that patients who had CABG between 1 and 10 years before the present admission, used diuretics and were referred to our center in an outpatient setting had a higher probability to receive medical treatment. Use of diuretic may be a sign that the patient had heart failure and therefore, the second revascularization was not proposed for the patient; even though the mean of ejection fraction was not different between the two groups. On the other hand, being in an outpatient setting could imply the fact that the patient was in a better health condition and/or was less symptomatic. Findings of this study can help the cardiologist to take more caution in their recommendation to ACS patients with prior history of CABG who have the abovementioned risk factors for repeat revascularization therapy.

Study limitation

The first limitation of this study is its retrospective design. Second, this was a single-center study, and thereby our findings should be interpreted cautiously in general practice. Moreover, some of our patients underwent CABG at other hospitals, so we are not able to collect the data from their previous surgical records.


  Conclusion Top


We concluded that the new onset of ischemia in patients with a history of CABG mostly result from the stenosis or occlusion of the vascular grafts and anastomoses. Time of CABG <1 year or >10 years, use of diuretics and presenting in an inpatient setting were significant predictors for recommending the second revascularization either by PCI or repeat CABG in our study population. Prospective studies in the future can better evaluate the predictive factors for repeat revascularization in patients with a history of CABG.

Acknowledgement

The present study was the doctorate thesis of Dr. Marjan Haddadi for the degree of Cardiology subspecialty and was supported by Tehran Heart Center and Tehran University of Medical Sciences.

Financial support and sponsorship

This study was funded by Tehran Heart Center.

Conflicts of interest

There are no conflicts of interest.



 
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