1.
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What baseline clinical
characteristics relate to short- and long-term survival after the diagnosis of coronary
artery disease?
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| Cardiac markers of short-term mortality in patients with coronary artery
disease include left ventricular dysfunction, extensiveness of coronary artery disease,
congestive heart failure, and acuteness of presentation. Other marker s of short-term
mortality include advanced age, prior cardiac surgical procedure, and non-cardiac vascular
disease and co-morbidity, especially renal or pulmonary dysfunction. Baseline
characteristics that influence long-term survival, regardless of the therapy chosen,
include left ventricular ejection fraction, age, co-morbidity, non-cardiac vascular
disease, congestive heart failure, and myocardial infarction within 24 hours of
presentation. |
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2.
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What is the interaction of
these baseline characteristics with treatment received and which characteristic best
identifies the most efficacious treatment for an individual patient?
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An optimal strategy of assigning patients to the most appropriate
therapy would tend to equalize the power of prognostic variables in the total population
of patients, thereby negating treatment-related differences observed for individual
variables. If treatment selection could be perfect, the relative power of each prognostic
variable would converge on that defined only by its biologic importance. Most
characteristics which identify a high risk of medical treatment in patients with coronary
disease also identify patients with increased risk of either angioplasty or bypass
surgery.
Coronary anatomy is the single exception to this generalization. Therefore, this
baseline characteristic is most useful for identifying the most effective treatment for an
individual patient. More diffuse or severe coronary atherosclerosis is associated with
increased mortality in medically-treated patients, in contrast to only minimal increase in
mortality risk in surgically-treated patients. Patients treated with angioplasty tend to
fall between surgically- and medically-treated patients in short- and long-term outcome
defined by anatomic extensiveness of disease. All other prognostic markers tend to elevate
the relative risk equally in all treatment groups. Therefore, any absolute benefit
conferred by either interventional treatment as a function of coronary anatomy tends to be
amplified by the other markers of increased risk. |
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3.
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What characteristics of
coronary anatomy best define prognosis, and what is the interrelationship of treatment
received and outcome as a function of extensiveness of coronary artery disease?
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| The descriptors of coronary anatomy shown to be related to prognosis
and useful for treatment selection include the number of 75% and 95% stenosis and the
presence and location of a left anterior descending coronary artery (LAD). Patients with a
60% or greater stenosis of the left main coronary artery have survival benefit from
surgery in comparison to medical treatment or angioplasty, and these patients should
receive this treatment unless contraindications are present. Except for patients with a
95% stenosis of the proximal LAD, patients with single-vessel disease treated medically
have sufficiently good prognosis that the addition of PTCA or CABG does not substantially
alter their survival. Interventional therapy in these patients is commonly used for
treatment of angina or pain because of acute coronary occlusion. Because long-term
survival is as good or better than with CABG, patients with lesions approachable by
angioplasty should receive this treatment if prevention is to be done. |
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4.
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What are the early
outcomes of percutaneous transluminal coronary angioplasty (PTCA) and coronary artery
bypass grafting (CABG) in patients with two- and three-vessel coronary artery disease?
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Nine randomized trails have addressed the relative benefit of PTCA and
CABG in patient population of 5,200 patients, including those with two- or three- vessel
disease. Individual and combined trial results showed no treatment-related difference in
survival, but results of these trials are useful in individualizing the treatment for
specific patients with two- or three- vessel coronary artery disease. The largest of these
trials was the NIH-sponsored Bypass Angioplasty Revascularization Investigation (BARI),
conducted at 18 North American centers with randomization of 1828 patients with two- or
three-vessel CAD to receive PTCA or CABG between 1988 and 1991. The table that follows
demonstrates that the in-hospital outcome of the two interventional treatments were
similar.
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In-Hospital Procedure
Outcomes |
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CABG |
PTCA |
| Death |
1.3% |
1.2% |
| Q-wave MI |
4.6% |
2.1% |
| Stroke |
0.8% |
0.2% |
| Emergency CABG |
0.1% |
6.3% |
| Emergency PTCA |
0.0% |
2.2% |
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5.
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What is the difference in
the five-year survival of patients in the BARI trial treated with CABG or PTCA?
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| Five year survival in the BARI trial for 1829 randomized patients was 89.3% for CABG and 86.3% for PTCA (p=.17). However, patients subseted by those with
diabetes treated with either oral agents or insulin showed a 15% survival advantage of
CABG over PTCA at five years in contrast to no survival difference between assessments for
those patients without diabetes. Similar trends are apparent in the smaller CABRI trial
and suggest that CABG should be considered the first line of treatment in this patient
group. These results raise a question of whether PTCA might also be less effective than
CABG in single-vessel patients who are diabetic. Further investigation is needed to define
the mechanisms underlying the better observed outcome in diabetic patients treated with
CABG in comparison to angioplasty. |
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6.
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Compare the time course of
ischemic endpoints and the need for further medical care in BARI patients receiving PTCA
or CABG?
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| The BARI trial compared secondary endpoints related to ischemia, such
as angina, anti-angina medication, ischemia on treadmill, repeat hospitalizations, and
repeat revascularization procedures in the two randomized reports. Each o f these ischemia
markers showed more abnormalities in patients treated with angioplasty. Both therapies
were quite effective in relieving angina and decreasing ischemia on treadmill testing.
However, small but significant differences in these parameters suggested CABG provided
more definitive relief of myocardial ischemia than PTCA. Need for secondary procedures was
most marked in the PTCA group, which required one or more secondary procedures in 70% of
the PTCA population at five years in comparison to 10% of the CABG population. However,
with the use of one or more additional PTCAs, only 30% of the PTCA population required
CABG within five years. Therefore, for patients with an overriding goal to avoid CABG, the
choice of PTCA will be 70% effective in achieving the goal with one or more PTCAs but
without an additional penalty of greater risk of myocardial infarction. However, for
patients who have as a primary goal the definitive relief of symptoms with little chance
of requiring further intervention, CABG would be the preferred treatment. |
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7.
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Describe differences in
cost of care and quality of life in similar patients treated with CABG or PTCA?
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| Extensive comparisons of markers of self-rated health quality of life
assessments, physical function scores, and the time of returning to work or other
productive life activities differed little between the PTCA and CABG patients in the BARI
trial. Both interventional therapies were effective in improving quality of life.
Comparative cost of the two treatments showed angioplasty to be less expensive initially,
but as recurrent procedures were required in t he PTCA group, the cost of PTCA approached
the cost of CABG by the end of five years of follow-up. At this time, CABG remained $2,000
more expensive than PTCA. However, patients with diabetes, three-vessel disease, and
advanced age (markers suggesting more favorable outcomes with coronary surgery), also had
a lower cost for a CABG strategy than for PTCA. PTCA was less expensive than CABG in
non-diabetic, two-vessel disease and in younger patients. These results suggest that the
most efficacious treatment also tended to be the most cost-effective treatment over the
five-year study period. |
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