The Effect of Cardiovascular Risk Factors and Coronary Atherosclerosis Severity on Long Term Graft Patency Rate in Patients Who Underwent Coronary Artery Bypass Graft Surgery

Kadriye Memiç Sancar1, Yelda Tayyareci2, Nuran Yazıcıoğlu3, Bingül Dilekci Şahin4, Ömer Yıldız5, Selen Yurdakul3, Cavlan Çiftçi3

1Department of Cardiology, Istanbul Mehmet Akif Ersoy Thoracic and Cardiovascular Surgery Training and Research Hospital, Istanbul, Turkey
2Department of Cardiology, Liv Hospital, Istanbul, Turkey
3Department of Cardiology, Florence Nightingale Hospital, Istanbul, Turkey
4Department of Cardiology, Kastamonu Training and Research Hospital, Istanbul, Turkey
5Department of Cardiology, Koc University Hospital, Istanbul, Turkey

Keywords: Coronary artery disease; heart disease risk factors; coronary artery bypass grafting.

Abstract

Introduction: The postoperative success of coronary artery bypass grafting depends on graft patency rate. The atherosclerotic process goes on in native arteries and bypass grafts of patients who underwent coronary artery bypass graft surgery. In this study, we aimed to investigate the effect of preoperative cardiovascular risk factors and the extensity of atherosclerosis detected by coronary angiography on long-term graft survival after the operation.

Patients and Methods: We included 974 patients (738 males, 236 females, mean age 57.9 ± 9.0 years) who underwent isolated coronary artery bypass graft surgery between the years 1990-2010 and coronary angiography due to various reasons during their follow-ups. The cardiovascular risk factors of the patients were detected and the extensity of coronary artery disease in the pre-operative coronary angiographies was determined by calculating Gensini Score Index. The effect of these results on graft patency was analyzed.

Results: As a result of coronary angiography, overall graft patency rates were found to be 52.6%, 64.6%, and 38.4% in the 1st, 5th and 10th years, respectively. Arterial grafts showed better patency rates than venous grafts in both short-term (1st year) and long-term (5th and 10th years). Independent cardiovascular risk factors were age (beta: 0.006, p= 0.001), smoking (beta: 0.101, p= 0.003), and family history (beta: 0.063, p= 0.03) for all occluded grafts. Diabetes mellitus (beta: 0.03, p= 0.02) and Gensini Score Index (beta: 0.01, p= 0.03) were associated with occluded left internal mammary artery graft. Age (beta: 0.05, p= 0.002), smoking (beta: 0.073, p= 0.002), and Gensini Score Index (beta: 0.001, p= 0.002) were associated with occluded saphenous vein graft. Smoking (beta: 0.047, p= 0.001), family history (beta: 0.033, p= 0.013), and Gensini Score Index (beta: 0.001, p= 0.001) were associated with occluded right internal mammary artery graft.

Conclusion: According to short and long-term results of a large group of patients, graft atherosclerosis was associated with cardiovascular risk factors, the extensity of coronary atherosclerosis, type and duration of graft. Today, primary and secondary cardiovascular risk factors should be improved to achieve higher longterm graft patency rates.

Introduction

Coronary artery disease (CAD) is the most significant cause of mortality and morbidity in the world(1). Atherosclerosis is the most critical and common reason for CAD(2). Many risk factors are known to cause CAD. By controlling these risk factors in CAD, nonfatal coronary cases can drop, and cardiovascular deaths can also be reduced by half(1). So, risk factors should be identified, and action should be taken against preventable risk factors.

Coronary artery bypass graft (CABG) surgery is a safe and effective treatment method and it has been used to treat multivessel disease for many years(3). The atherosclerotic process goes on in native arteries and by-pass grafts after CABG surgery, and the postoperative success depends on graft patency rate(4). In studies, many cardiovascular risk factors and biochemical parameters were reported to be critical initiating events of coronary atherosclerosis; however, the results of the impact of these risk factors on atherosclerosis progression after CABG and percutaneous coronary intervention (PCI) were contradictory(5).

In our study, we aimed to retrospectively investigate the effect of preoperative CV risk factors and the atherosclerosis severity detected by coronary angiography on long-term postoperative graft survival.

Materials and Methods

Hospital health records and computer-stored patient medical records from 1990 to 2010 were retrospectively reviewed for the study. Our study includes a total of 974 patients who underwent coronary angiography due to various reasons in our hospital after CABG surgery. Preoperative cardiovascular risk factors, demographic data, echocardiographic and biochemical parameters of the study population were recorded. The severity of CAD was determined based on the stenosis obtained in preoperative coronary angiography by calculating the Gensini score index (GSI)(6). The year and reason of the postoperative coronary angiography and the rates for graft occlusion/stenosis were recorded.

Patients with moderate and severe valvular heart disease, cardiomyopathy, hepatic insufficiency, and malignancy and who underwent valvular surgery were excluded from the study.

Gensini Scoring System

Gensini score index (GSI) was calculated multiplying the Gensini severity coefficient determined for stenosis ratio (stenosis rates were 0-25%, 25-50%, 50-75% 75-90%, 90-99%, and complete occlusion, and the Gensini scores were 1, 2, 4, 8, 16, and 32, respectively) by the coefficient determined according to the functional importance of myocardial region supplied by the stenosed artery(6). Accordingly, left main coronary artery (LMCA), proximal left anterior descending artery (LAD), proximal circumflex artery (Cx), and LAD medium segment were multiplied by 5, 2.5, 2.5, and 1.5, respectively, and right coronary artery (RCA), distal LAD, posterior descending artery (PDA), optus marginal (OM) artery were multiplied by 1, and the others were multiplied by 0.5. The number of grafts and the bypass graft information were obtained from medical records of the surgery.

Ethical Statement

The design of the study, prepared in accordance with the principles stated in the Helsinki Declaration, was approved by the local Clinical Research Ethics Committee.

Statistical Analysis

Mean + standard deviation was used for normally distributed continuous variables, and median (max-min) values were used for non-normally distributed continuous variables. Pearson correlation coefficient was used to calculate the relationship between continuous variables, and Spearman’s correlation was used for non-continuous variables. The correlation coefficient (r) was calculated for the correlation analysis. The degrees of correlation coefficients were determined as follows: a low degree was between |0 and 0.25|, a moderate degree was between |0.25 and 0.50|, a strong degree was between |0.50 and 0.75|, and a very strong degree was between |0.75 and 1|. Linear regression analysis was used for multivariate analysis. p< 0.05 was statistically significant. SPSS 15.0 “Statistical Package for Social Sciences” software was used for all calculations.

Results

Preoperative demographic and clinical variables of 974 patients are shown in Table 1. These patients first underwent isolated CABG surgery and then at least one year after the operation, they underwent angiography during their followups. Of all the patients, 24.2% were female, and the mean age was 57.9 ± 9.0 years. Preoperative coronary angiographies showed that 20% had single-vessel disease, 35% had twovessel disease, 45% had multiple vessel disease, and the mean GSI of the patients was 66.7 ± 33.3.

Table 1. Baseline demographic and clinical variables of the study population

The information regarding the grafts used in surgeries of the study population was obtained from operation records. The rates of left internal mammary artery-left anterior descending (LIMA-LAD), saphenous vein graft-obtuse marginal artery (SVG-OM), and saphenous vein graft-right coronary artery (SVG-RCA) grafts used in the operations were 80.1%, 41.4%, and 29.4%, respectively.

The mean number of years that the patients had angiography was 5.2 ± 2.89 years with a minimum of 1 year and a maximum of 10 years. The coronary angiography was performed due to stable angina pectoris in 458 patients (47%), unstable angina pectoris in 82 patients (8.4%), non-ST myocardial infarction (MI) in 16 patients (1.6%), ST-elevation MI in 4 patients (0.4%), and atypical chest pain, dyspnea, heart deficiency, positive cardiac stress test, ventricular arrhythmia, and ischemia in thallium in 414 patients (42.5%).

As a result of the coronary angiography, graft patency was calculated in terms of years. The LIMA graft patency rates were 90.1%, 94.6%, and 95.3% in the 1st, 5th, and 10th years, respectively. The SVG patency rates were 73.6%, 83.5%, and 61.5% in the 1st, 5th, and 10th years, respectively. The right internal mammary artery (RIMA) graft patency rates were 92.9%, 93.6%, and 93.8% in the 1st, 5th, and 10th years, respectively.

Multivariate linear regression analysis revealed that age (beta: 0.006, p= 0.001), smoking (beta: 0.101, p= 0.003), prior MI (beta: 0.097, p= 0.02), prior PCI (beta: 0.078, p= 0.02), and family history (beta: 0.063, p= 0.03) were independent risk factors for all the occluded grafts (Table 2). Diabetes mellitus (DM) (beta: 0.03, p= 0.02), prior MI (beta: 0.038, p= 0.04), and GSI (beta: 0.01, p= 0.03) were independent risk factors for occluded LIMA graft (Table 3). Age (beta: 0.05, p= 0.002), smoking (beta: 0.073, p= 0.002), prior PCI (beta: 0.080, p= 0.02), ejection fraction (EF) (beta: 0.101, p= 0.004), and GSI (beta: 0.001, p= 0.002) were independent risk factors for occluded SVG (Table 4). Smoking (beta: 0.047, p= 0.001), family history (beta: 0.033, p= 0.013), peripheral artery disease (PAD) (beta: 0.059, p= 0.002), and GSI (beta: 0.001, p= 0.001) were independent risk factors for occluded RIMA graft (Table 5).

Table 2. Regression analysis giving information about independent predictors of all graft occlusions

Table 3. Regression analysis giving information about independent predictors of LIMA graft occlusion

Table 4. Regression analysis giving information about independent predictors of SVG occlusion

Table 5. Regression analysis giving information about independent predictors of RIMA graft occlusion

Discussion

Preoperative demographic and clinical variables of 974 patients are shown in Table 1. These patients first underwent isolated CABG surgery and then at least one year after the operation, they underwent angiography during their followups. Of all the patients, 24.2% were female, and the mean age was 57.9 ± 9.0 years. Preoperative coronary angiographies showed that 20% had single-vessel disease, 35% had twovessel disease, 45% had multiple vessel disease, and the mean GSI of the patients was 66.7 ± 33.3.

Table 1. Baseline demographic and clinical variables of the study population

The information regarding the grafts used in surgeries of the study population was obtained from operation records. The rates of left internal mammary artery-left anterior descending (LIMA-LAD), saphenous vein graft-obtuse marginal artery (SVG-OM), and saphenous vein graft-right coronary artery (SVG-RCA) grafts used in the operations were 80.1%, 41.4%, and 29.4%, respectively.

The mean number of years that the patients had angiography was 5.2 ± 2.89 years with a minimum of 1 year and a maximum of 10 years. The coronary angiography was performed due to stable angina pectoris in 458 patients (47%), unstable angina pectoris in 82 patients (8.4%), non-ST myocardial infarction (MI) in 16 patients (1.6%), ST-elevation MI in 4 patients (0.4%), and atypical chest pain, dyspnea, heart deficiency, positive cardiac stress test, ventricular arrhythmia, and ischemia in thallium in 414 patients (42.5%).

As a result of the coronary angiography, graft patency was calculated in terms of years. The LIMA graft patency rates were 90.1%, 94.6%, and 95.3% in the 1st, 5th, and 10th years, respectively. The SVG patency rates were 73.6%, 83.5%, and 61.5% in the 1st, 5th, and 10th years, respectively. The right internal mammary artery (RIMA) graft patency rates were 92.9%, 93.6%, and 93.8% in the 1st, 5th, and 10th years, respectively.

Multivariate linear regression analysis revealed that age (beta: 0.006, p= 0.001), smoking (beta: 0.101, p= 0.003), prior MI (beta: 0.097, p= 0.02), prior PCI (beta: 0.078, p= 0.02), and family history (beta: 0.063, p= 0.03) were independent risk factors for all the occluded grafts (Table 2). Diabetes mellitus (DM) (beta: 0.03, p= 0.02), prior MI (beta: 0.038, p= 0.04), and GSI (beta: 0.01, p= 0.03) were independent risk factors for occluded LIMA graft (Table 3). Age (beta: 0.05, p= 0.002), smoking (beta: 0.073, p= 0.002), prior PCI (beta: 0.080, p= 0.02), ejection fraction (EF) (beta: 0.101, p= 0.004), and GSI (beta: 0.001, p= 0.002) were independent risk factors for occluded SVG (Table 4). Smoking (beta: 0.047, p= 0.001), family history (beta: 0.033, p= 0.013), peripheral artery disease (PAD) (beta: 0.059, p= 0.002), and GSI (beta: 0.001, p= 0.001) were independent risk factors for occluded RIMA graft (Table 5).

Table 2. Regression analysis giving information about independent predictors of all graft occlusions

Table 3. Regression analysis giving information about independent predictors of LIMA graft occlusion

Table 4. Regression analysis giving information about independent predictors of SVG occlusion

Table 5. Regression analysis giving information about independent predictors of RIMA graft occlusion

Conclusion

In conclusion, CAD risk factors alone have a limited effect on grafts. This might be due to the multifactorial development and progression of atherosclerosis. However, the struggle against risk factors should be handled individually as coronary atherosclerosis progression is known to continue in both native coronary arteries and bypass grafts.

Ethics Committee Approval

This study was approved by the Scientific Research and Evaluation Committee of Istanbul Bilim University Faculty of Medicine (Decision No: 24.12.2010/1).

Peer Review

Externally peer-reviewed.

Author Contributions

Concept/Design - KS; Analysis/Interpretation - YT; Data Collection - KS, BD; Writing - KS; Critical Revision - ÇÇ, NY; Statistical Analysis - YT, SY; Overall Responsibility - KS; Final Approval - All of authors.

Conflict of Interest

The authors have no conflicts of interest to declare.

Financial Disclosure

The authors declared that this study has received no financial support.

References

  1. Yusuf S, Hawken S, Ounpuu S, Dans T, Avezum A, Lanas F, et al. INTERHEART Study Investigators. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries: case-control study. Lancet 2004;364:937-52. [Crossref]
  2. Moise A, Lesperance J, Theroux P. Clinical and angiographic predictors of new total coronary occlusion in coronary artery disease. Analysis of 313 on-operated patients. Am J Cardiol 1984;54:1176-81. [Crossref]
  3. Morrow DA, Gersh BJ, Braunwald E. Chronic coronary artery disease. Braunwald‘s Heart Disease: A Textbook of Cardiovascular Medicine. 7th ed. Philadelphia: Elsevier Saunders, 2005:1281-354. [Crossref]
  4. Kaya E, Mansuroglu D, Göksedef D, Ömeroğlu SN, Toker ME, Kırali K, et al. Long-term angiographic results of coronary artery bypass surgery with the use of arterial graft combinations. Türk Göğüs Kalp Damar Cer Derg 2005;13:309-13. [Crossref]
  5. Gottlieb SO. Asymptomatic or silent myocardial ischemia in angina pectoris: pathophysiology and clinical implications. Cardiol Clin 1991;9:49-61. [Crossref]
  6. Gensini GG, Kisko M. Coronary Arteriogaphy. New York: Futura Publishing Co, 1975. [Crossref]
  7. Domanski MJ, Borkowf CB, Campeau L, Knatterud GL, White C, Hoogwerf B, et al. Prognostic factors for atherosclerosis progression in saphenous vein grafts: the postcoronary artery bypass graft (post-CABG) trial. J Am Coll Cardiol 2000;36:1877-83. [Crossref]
  8. Motwani JG, Topol JG. Aortocoronary saphenous vein graft disease: pathogenesis, predisposition and prevention. Circulation 1998;97:916-31. [Crossref]
  9. Van Brussel BL, Voors AA, Ernst JM, Knaepen PJ, Plokker HW. Venous coronary artery bypass surgery: a more than 20-year follow-up study. Eur Heart J 2003;24:927-36. [Crossref]
  10. Goldman S, Zadina K, Moritz T, Ovitt T, Sethi G, Copeland JG, et al. Long-term patency of saphenous vein and left internal mammary artery grafts after coronary artery bypass surgery: results from a Department of Veterans Affairs Cooperative Study. J Am Coll Cardiol 2004;44:2149-56. [Crossref]
  11. Ulus T, Yıldırır A, Sade LE, Balta Ş, Özin B, Sezgin A, et al. Serum gammaglutamyltransferase activity: a new marker for coronary artery bypass graft disease. Türk Kardiyol Dern Arşivi 2011;39:205-13. [Crossref]
  12. Daida H, Yokoi H, Miyano H, Mokuno H, Satoh H, Kottke TE, et al. Relation of saphenous vein graft obstruction to serum cholesterol levels. J Am Coll Cardiol 1995;25:193-7. [Crossref]
  13. Raichlen JS, Healy B, Ascuff SC, Pearson TA. Importance of risk factors in the angiographic progression of coronary artery disease. Am J Cardiol 1986;57:66-70. [Crossref]
  14. Neitzel GF, Barboriak JJ, Pintar K, Qureshi I. Atherosclerosis in aorotcoronary bypass grafts. Morphologic study and risk factor analysis 6 to 12 years after surgery. Arteriosclerosis 1986;6:594-600. [Crossref]
  15. Tatoulis J, Buxton BF, Fuller JA. Patencies of 2127 arterial to coronary conduits over 15 years. Ann Thorac Surg 2004;77:93-101. [Crossref]
  16. Zacharias A, Schwann TA, Riordan CJ, Durham SJ, Shah AS, Habib RH. Late results of conventional versus all-arterial revascularization based on internal thoracic and radial artery grafting. Ann Thorac Surg 2009;87:19-26. [Crossref]
  17. Loop FD. Internal thoracic artery grafts: biologically beter coronary arteries. N Engl J Med 1996;334:263-5. [Crossref]
  18. Amoroso G, Tio RA, Mariani MA, Van Boven AJ, Jessurun GA, Monnink SH, et al. Functional integrity and aging of the left internal thoracic artery after coronary artery bypass surgery. J Thorac Cardiovasc Surg 2000;120:313-8. [Crossref]
  19. Gonzales SJM, Castano RM. Coronary artery surgery in diabetic patients. Rev Esp Cardiol 2002;55:1311-22. [Crossref]
  20. Wendler O, Hennen B, Markwirth T, Nikoloudakis N, Graeter T, Schäfers HJ. Complete arterial revascularization in the diabetic patient-early postoperative results. Thorac Cardiovasc Surg 2001;49:5-9. [Crossref]
  21. Fiore AC, Naunheim KS, Dean P, Kaiser GC, Pennington G, Willman VL, et al. Results of internal thoracic artery graftingover 15 years: single versus double grafts. Ann Thorac Surg 1990;49:202-9. [Crossref]
  22. Tatoulis J, Royse AG, Buxton BF, Fuller JA, Skillington PD, Goldblatt JC, et al. The radial artery in coronary surgery: a 5-year experience-clinical and angiographic results. Ann Thorac Surg 2002;73:143-8. [Crossref]
  23. Shah PJ, Gordon I, Fuller J, Seevanayagam S, Rosalion A, Tatoulis J, et al. Factors affecting saphenous vein graft patency: clinical and angiographic study in 1402 symptomatic patients operated on between 1977 and 1999. J Thorac Cardiovasc Surg 2003;126:1972-7. [Crossref]
  24. Hess CN, Lopes RD, Gibson CM, Hager R, Wojdyla DM, Englum BR, et al. Saphenous vein graft failure after coronary artery bypass surgery: insights from PREVENT IV. Circulation 2014;130:1445-51. [Crossref]
  25. Barner HB, Standeven JW, Reese J. Twelve-year experience with internal mammary artery for coronary bypass. J Thorac Cardiovasc Surg 1985;90:668-75. [Crossref]
  26. Mehta RH, Honeycutt E, Shaw LK, Sketch MH Jr. Clinical characteristics associated with poor long-term survival among patients with diabetes mellitus undergoing saphenous vein graft interventions. Am Heart J 2008;156:728-35. [Crossref]
  27. Domanski MJ, Borkowf CB, Campeau L, Knatterud GL, White C, Hoogwerf B, et al. Prognostic factors for atherosclerosis progression in saphenous vein grafts the postcoronary artery bypass graft (post-CABG) trial. J Am Coll Cardiol 2000;36:1877-83. [Crossref]
  28. Campos E, Cinderella J, Farhi E. Long-term angiographic follow-up of normal and minimally diseased saphenous vein grafts. J Am Coll Cardiol 1993;21:1175-80. [Crossref]

Figure and Tables

Table 1. Baseline demographic and clinical variables of the study population
Table 2. Regression analysis giving information about independent predictors of all graft occlusions
Table 3. Regression analysis giving information about independent predictors of LIMA graft occlusion
Table 4. Regression analysis giving information about independent predictors of SVG occlusion
Table 5. Regression analysis giving information about independent predictors of RIMA graft occlusion