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Randomized Studies Of CAB

Randomized Studies of CAB

1. Comparisons of bypass surgery with medical therapy

Trial CooperativePatientsRandomized
VA cooperative trial (VA)6861972-74
European cooperative surgical study (ECSS)7681973-76
Coronary artery surgery study (CASS)7801974-79

2. Severity of angina

A. Objective evidence of ischemia
B. Instability of angina (crossover 20% 6 months, 50% 5 years)
C. Myocardial infarction
D. Severity of stenosis (L. main, 3 vessel, proximal LAD)
E. Left ventricular dysfunction
F. Age

3. Summary

A. Patients with single, double or triple vessel disease, good ventricular function (>50%) and no exercise induced ischemia have a good prognosis.
B. Improved survival is seen in patients with triple vessel disease, left main disease and reduced ejection fraction (>35%, <50%) following surgery.
C. Improved surgical survival is seen in patients with any two of the following clinical risk factors: h/o hypertension, h/o myocardial infarction, resting ST- T abnormalities.

4. Comparison of bypass surgery with angioplasty

A. The randomized interventional treatment of angina (RITA) - March 1993, Lancet (longest follow-up)
B. The German Angioplasty Bypass Surgery Investigation (GABI) 1994 - New England Journal
C. The Coronary Artery Bypass Revascularization Investigation (CABRI) August 1993
D. Argentine Randomized trial of Percutaneous Transluminal Coronary Angioplasty v/s coronary artery bypass surgery (ERACI) October 1993, JACC.

5. Rita Trial

Inclusion CriteriaSymptomatic or asymptomatic SVD or MVDsuitable for equivalent revascularization
Baseline CharacteristicsClass 3-4 angina 59%; hx MI 43%3VD 12% > 3Rx 38%
Patients (n)501510
Early outcomeIn-hospitalIn-hospital
Late outcome2-2.5 years2-2.5 years
Event-free survival89%62%

6. Gabi Trial

Inclusion CriteriaSymptomatic MVDsuitable for complete revascularization
Baseline CharacteristicsClass 4 angina, 19%; hx MI 50%mean LVEF 56%
Patients (n)177182
Early outcomeIn-hospitalIn-hospital
Late outcome1 year1 year
Event-free survival94%58%

7. Gabri Trial

Inclusion CriteriaSymptomatic or asymptomatic MVDLVEF > 35%
Baseline CharacteristicsClass 3-4 angina 66%; hx MI 42%3VD 40% > 3Rx 26%, mean LVEF 63%
Patients (n)513541
Early outcome30 days30 days
Late outcome1 year1 year
Event-free survival85%60%

8. Eraci Trial

Inclusion CriteriaSymptomatic MVDsuitable for revascularization
Baseline CharacteristicsClass 3-4 anginaLVEF > 35%
Patients (n)6463
Early outcomeIn-hospitalIn-hospital
Late outcome1 year1 year
Event-free survival83.5%63.7%

9. Survival (older 3v disease, + 2v disease, - 1v disease)

A. Symptom free survival
B. Incidence of myocardial infarction
C. Freedom from crossover to CABG after angioplasty (5 yrs - 25%)
D. Event free survival

10. For low risk patients with two vessel disease, angioplasty may provide modest survival benefits relative to medical therapy.

A. In single vessel disease, the primary treatment choice is between medicine and PTCA
B. Survival benefits of surgical revascularization are magnified on the absolute scale by factors that increase overall medical risk, especially left ventricular dysfunction and advanced age. These factors tend to increase procedural risks but offer proportionately greater long-term benefits than can be expected with medical treatment

11. Summary

A. The more extensive the coronary artery disease, the larger the benefit derived from surgical revascularization
B. In the most severe forms of coronary artery disease (Left main, triple vessel) bypass surgery provides the best long term survival results
C. In patients with two vessel disease, the higher the risk the more likely that patient will have improved survival with bypass surgery (eg. impaired left ventricular function, older age, co-existing vascular disease)


Surgical Indications for Coronary Revascularization

1. Objectives of CABG

A. relieve ischemia
B. prolong survival
C. prevent MI..
D. preserve LV function
E. improve exercise tolerance

2. Assessing CABG Candidates

A. degree of symptoms
B. associated medical problems
C. evidence of reversible ischemia
D. Documentation of abnormal coronaries
E. LV function

3. Angina

A. Chronic Stable Angina defined as stable pain pattern for 4-6 weeks
B. Canadian Cardiovascular Society Classification
1) Class I. Angina: occurs with strenuous activity
2) Class II. Angina: pain with rapid walk or climbing multiple stairs
3) Class III Angina: pain with walking < 2 blocks on level ground @ a normal pace or climbing one flight of stairs
4) Class IV. : pain with minimal activity or @ rest if it last < 15 min.
5) Unstable Angina: pain @ rest that last more than 15 min.

4. Studies

A. General
1) three major studies of medical vs. surgical treatment
2) use of early CABG techniques
3) no LIMA
4) no wide spread use of cardioplegia
5) no postop antiplatelet therapy
B. VA Study (1970)
1) 686 patients
2) criteria
a) > 50% lesion in one or more vessel
b) graftable vessels
c) acceptable LV function
3) results:
a) 36 month survival was 87% in the medical group and 88% in the surgical arm
(1) patients with a left main lesions were the only group to show a survival advantage with surgery
b) 7 year survival 70% with medical and 77% with surgical
c) beyond 7 years any survival advantage with surgery begins to disappear except in patients with three vessel disease and decreased LV function
C. European Cooperative Surgical Study (ECSS)
1) 768 men, < 65 yrs old, > 3 month hx of angina, @ least 2 vessel disease, and LV function > 50%
2) results:
a) survival @ 16 months was 93.5% in the surgical group and 84.1% in the medical group
b) survival advantage was greatest in patients with three vessel disease, left main disease , or two vessel disease with a proximal LAD lesion
3) Conclusion:
a) symptomatic stable angina with left main , three vessel, or two vessel disease including a proximal LAD lesion benefit from surgery
D. Coronary Artery Surgery Study (CASS)
1) 2099 patients, 780 truly randomized the other chose their therapy
2) set out to answer the question which was the best therapy for patients with minimal symptoms - most patients had class I and II angina
3) results:
a) survival @ 5 yrs was equal in medical and surgical groups
b) medical group had a 5%/ yr. conversion to surgery
c) increased survival @ 7 yrs for patients with decreased EF and three vessel disease
4) Conclusion:
a) mild angina with an EF between 35 - 50%, and three vessel disease had increased survival @ seven years
b) incidence of MI was the same in both groups

5. Indications for CABG

1) failure of medical therapy
2) unstable angina
3) Left main disease
4) symptomatic three vessel disease
5) post infarction angina
6) acute MI with shock
7) failed PTCA
8) reoperation for recurrent symptoms
9) congenital anomalies
10) Kawasaki's disease
A. Failure of medical therapy
1) CASS:
a) patients with three vessel disease and class III - IV angina had increased survival and decreased MI @ 5 years regardless of LV function
b) patients with one or two vessels with decreased LV function
B. Unstable Angina
1) surgery provides increased relief of symptoms, but no survival benefit compared to medical therapy
C. Left main
1) survival increased for 60% - 90% @ 4 yrs with surgery
D. 3 Vessel disease and decreased LV function
1) VA and CASS studies support
E. Post-infarction Angina
1) 5-10% incidence of MI with surgery
F. Acute MI with Shock
1) mortality > 80% in all comers
2) 30% mortality with surgery
G. Failed PTCA
1) incidence 3-4%
2) 5% mortality
3) 30-40% incidence of MI
H. Reop with recurrent symptoms
1) factors associated with decreased reop survival
a) failure to use the LIMA
b) decreased age
c) incomplete revascularization
d) smoking
2) Survival
Survival5 Years10 Years
first surgery90%75%