Chronic stable angina coronary artery bypass grafting versus medical therapy
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S.
Overview
In selected patients with stable angina, revascularization with CABG has shown to provide better symptomatic benefit and improved survival rates in comparison to medical therapy.[1]
Symptomatic Benefit
One of the earliest study that compared the benefit of CABG versus medical therapy in the management of stable angina was the Coronary Artery Surgery Study (CASS) (1990). This study demonstrated that more patients were angina-free after CABG as observed during one year (66% in the CABG group versus 30% in the medically treated group) and five-year follow-up (63% versus 38%). However, at ten-year follow-up these advantages were much less apparent and almost similar in both the groups (47% versus 42%) secondary to the recurrence of symptoms in the CABG group and also a large portion of medically treated patients underwent CABG at a later date, rendering them asymptomatic.[2]
Angina Severity:
Non-randomized observational study from the CASS registry involving 4,209 patients with similar angiographic findings was performed to evaluate the effect of angina severity on the clinical outcome of medical therapy. At 5-year follow-up, the survival rate was found to be significantly higher in the surgically treated group, in patients with Class III or IV angina and triple-vessel disease with either normal left ventricular function (≥ 92% in the surgically treated group versus 74% in the medically treated group; P=less than 0.0001) or reduced LV function (82% in the surgically treated group versus 52% in the medically treated group; P=less than 0.0001). Thus, the study confirmed the importance of clinical as well as anatomic factors in determining the prognosis of patients with ischemic heart disease and indicated that CABG improved the late-survival in patients with triple vessel disease and severe angina pectoris.[3]
Limitations of Long-term Symptomatic Benefit:
With the exception of left main disease, the long-term survival benefit from CABG is limited [4][5] and tends to be affected with the presence of severe LV dysfunction, increased rate of development of saphenous vein graft disease and/or atherosclerosis progression in other coronary vessels.
- In the CASS registry, 6-8% patients per year underwent repeat surgery for recurrent symptoms and the approximate five-year mortality rate with CABG was 1% per year.[2]
- Another study done in the late 1980's demonstrated that immediate post-CABG approximately 77% patients were free from all ischemic events at 5-years and reported improved survival rates in approximately 80% patients as observed at ten-year follow-up. However, 50% had recurrence of angina and only 15% remained angina-free at 15-year follow-up.[6]
Survival Benefits
No Survival Benefit Observed
Studies done in the early 1970's-1980's demonstrated no significant survival benefit observed with CABG in comparison to medical therapy alone.[7][8][9][10]
Individuals who may benefit from CABG:
- CABG has shown to offer significant survival benefits in patients with high-risk CAD. This includes patients with:
- Left main stenosis or left main equivalent disease
- Severe proximal LAD stenosis. Proximal LAD stenosis with concurrent RCA obstruction has shown to be associated with worst outcomes in comparison to a lesion present in the distal LAD [11]
- The 2004 ACC/AHA guidelines on CABG,[15] recommended CABG would benefit patients with:
- One- or two-vessel CAD without significant proximal LAD stenosis but with a large area of viable myocardium and high-risk criteria on noninvasive testing.
- Disabling angina despite maximal noninvasive therapy.
Exercise Stress Test:
- Based on the exercise tolerance and duration to ST segment depression during exercise, patients with symptomatic coronary artery disease who received medical therapy are classified into high-risk subgroup with an annual mortality of greater than 5% per year and a low-risk subgroup with an annual mortality of 1% per year.[16][17]
- According to the Duke treadmill score (DTS) for exercise testing, low-risk patients with a score of greater than or equal to (+5), had no coronary stenosis greater than 75% (60% patients) or single-vessel disease (16% patients). By comparison, high-risk patients with a score lower than (-11) reported to have triple-vessel or left main coronary disease (74% patients). However, the 5-year mortality was found to be 3%, 10%, and 35% for low-, moderate-, and high-risk DTS groups (P<0.0001).[16]
- In patients with suspected CAD, the ability of exercise-induced myocardial hypoperfusion on thallium scintigraphy may be used to determine which patients could more likely have an increased survival benefit from revascularization as opposed to medical therapy.[18] In a retrospective evaluation, 10,627 consecutive patients without prior MI or revascularization underwent exercise or adenosine perfusion scintigraphy. Of these, 671 patients underwent revascularization (2.8% mortality) and 9956 patients received medical therapy (1.3% mortality; P=0.0004) within 60 days after myocardial perfusion scintigraphy. At 2-year follow-up, medical therapy group demonstrated a significant survival advantage over patients undergoing revascularization in the setting of no or mild ischemia with an inducible ischemia of lower than 10% of total myocardium (0.9% versus 3.3%), whereas patients undergoing revascularization demonstrated an increasing survival benefit in the presence of moderate to severe ischemia with an inducible ischemia of greater than 10% of total myocardium (2.6% versus 5.4%).[19]
Limitations for Survival Benefits:
The benefits of CABG on survival and post-infarction mortality tends to be diminished with long-term follow-up even in high-risk patients,[5][4] and considered to be secondary to the progression of coronary artery disease which could be minimized with the current aggressive risk-factor modification.
References
- ↑ Smith SC, Feldman TE, Hirshfeld JW, Jacobs AK, Kern MJ, King SB et al. (2006) ACC/AHA/SCAI 2005 guideline update for percutaneous coronary intervention: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/SCAI Writing Committee to Update the 2001 Guidelines for Percutaneous Coronary Intervention). J Am Coll Cardiol 47 (1):e1-121. DOI:10.1016/j.jacc.2005.12.001 PMID: 16386656
- ↑ 2.0 2.1 Rogers WJ, Coggin CJ, Gersh BJ, Fisher LD, Myers WO, Oberman A et al. (1990) Ten-year follow-up of quality of life in patients randomized to receive medical therapy or coronary artery bypass graft surgery. The Coronary Artery Surgery Study (CASS) Circulation 82 (5):1647-58. PMID: 1977531
- ↑ Kaiser GC, Davis KB, Fisher LD, Myers WO, Foster ED, Passamani ER et al. (1985) Survival following coronary artery bypass grafting in patients with severe angina pectoris (CASS). An observational study. J Thorac Cardiovasc Surg 89 (4):513-24. PMID: 3884909
- ↑ 4.0 4.1 (1992) Eighteen-year follow-up in the Veterans Affairs Cooperative Study of Coronary Artery Bypass Surgery for stable angina. The VA Coronary Artery Bypass Surgery Cooperative Study Group. Circulation 86 (1):121-30. PMID: 1617765
- ↑ 5.0 5.1 5.2 (1984) Eleven-year survival in the Veterans Administration randomized trial of coronary bypass surgery for stable angina. The Veterans Administration Coronary Artery Bypass Surgery Cooperative Study Group. N Engl J Med 311 (21):1333-9. DOI:10.1056/NEJM198411223112102 PMID: 6333636
- ↑ Kirklin JW, Naftel CD, Blackstone EH, Pohost GM (1989) Summary of a consensus concerning death and ischemic events after coronary artery bypass grafting. Circulation 79 (6 Pt 2):I81-91. PMID: 2655982
- ↑ Murphy ML, Hultgren HN, Detre K, Thomsen J, Takaro T (1977) Treatment of chronic stable angina. A preliminary report of survival data of the randomized Veterans Administration cooperative study. N Engl J Med 297 (12):621-7. DOI:10.1056/NEJM197709222971201 PMID: 331107
- ↑ (1984) Myocardial infarction and mortality in the coronary artery surgery study (CASS) randomized trial. N Engl J Med 310 (12):750-8. DOI:10.1056/NEJM198403223101204 PMID: 6608052
- ↑ Kaiser GC (1986) CABG: lessons from the randomized trials. Ann Thorac Surg 42 (1):3-8. PMID: 2425758
- ↑ 10.0 10.1 Yusuf S, Zucker D, Peduzzi P, Fisher LD, Takaro T, Kennedy JW et al. (1994) Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists Collaboration. Lancet 344 (8922):563-70. PMID: 7914958
- ↑ Samaha JK, Connor MJ, Tribble R, Kroetz FW, Sullivan JM, Ramanathan KB et al. (1985) Natural history of left anterior descending coronary artery obstruction: significance of location of stenoses in medically treated patients. Clin Cardiol 8 (8):415-22. PMID: 4028534
- ↑ Myers WO, Schaff HV, Gersh BJ, Fisher LD, Kosinski AS, Mock MB et al. (1989) Improved survival of surgically treated patients with triple vessel coronary artery disease and severe angina pectoris. A report from the Coronary Artery Surgery Study (CASS) registry. J Thorac Cardiovasc Surg 97 (4):487-95. PMID: 2648078
- ↑ Passamani E, Davis KB, Gillespie MJ, Killip T (1985) A randomized trial of coronary artery bypass surgery. Survival of patients with a low ejection fraction. N Engl J Med 312 (26):1665-71. DOI:10.1056/NEJM198506273122603 PMID: 3873614
- ↑ Alderman EL, Bourassa MG, Cohen LS, Davis KB, Kaiser GG, Killip T et al. (1990) Ten-year follow-up of survival and myocardial infarction in the randomized Coronary Artery Surgery Study. Circulation 82 (5):1629-46. PMID: 2225367
- ↑ Eagle KA, Guyton RA, Davidoff R, Edwards FH, Ewy GA, Gardner TJ et al. (2004) ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery). Circulation 110 (9):1168-76. DOI:10.1161/01.CIR.0000138790.14877.7D PMID: 15339866
- ↑ 16.0 16.1 Shaw LJ, Peterson ED, Shaw LK, Kesler KL, DeLong ER, Harrell FE et al. (1998) Use of a prognostic treadmill score in identifying diagnostic coronary disease subgroups. Circulation 98 (16):1622-30. PMID: 9778327
- ↑ Weiner DA, Ryan TJ, McCabe CH, Chaitman BR, Sheffield LT, Ferguson JC et al. (1984) Prognostic importance of a clinical profile and exercise test in medically treated patients with coronary artery disease. J Am Coll Cardiol 3 (3):772-9. PMID: 6229569
- ↑ Ladenheim ML, Pollock BH, Rozanski A, Berman DS, Staniloff HM, Forrester JS et al. (1986) Extent and severity of myocardial hypoperfusion as predictors of prognosis in patients with suspected coronary artery disease. J Am Coll Cardiol 7 (3):464-71. PMID: 3950226
- ↑ Hachamovitch R, Hayes SW, Friedman JD, Cohen I, Berman DS (2003) Comparison of the short-term survival benefit associated with revascularization compared with medical therapy in patients with no prior coronary artery disease undergoing stress myocardial perfusion single photon emission computed tomography. Circulation 107 (23):2900-7. DOI:10.1161/01.CIR.0000072790.23090.41 PMID: 12771008