nlmpubs.nlm.nih.gov/2014.05.nlmpubs.nlm.nih.gov.tar/nlmpubs.nlm.nih.gov/alerts/diabetic.txt

Text File | 1995-09-20 | 10KB | 176 lines

Clinical Alert: Bypass Over Angioplasty for Patients With Diabetes.
National Heart, Lung, and Blood Institute (NHLBI)
September 21, 1995

Abstract:
The National Heart, Lung, and Blood Institute (NHLBI), part of
the National Institutes of Health, today announced that, as a first
revascularization procedure, coronary artery bypass graft (CABG)
surgery has been shown to have a markedly lower 5-year death rate
than angioplasty for persons with diabetes mellitus (Type I or II)
who are on oral hypoglycemic agents or insulin.

The finding came from the NHLBI-funded Bypass Angioplasty
Revascularization Investigation (BARI).  The multicenter,
international, randomized trial studied patients who needed a first
revascularization because of severe ischemia with obstructions in
two or more major coronary arteries.  Over 5 years, patients with
diabetes mellitus who were on drug therapy had a significantly lower
(p=0.002) mortality rate with CABG, compared with percutaneous
transluminal coronary angioplasty (PTCA).  The 5-year CABG mortality
rate was 19 percent, compared with 35 percent for PTCA.  By
contrast, in patients without diabetes and in those with diabetes
but not on drug treatment, the 5-year mortality rates for CABG and
PTCA were both about 9 percent.

The higher death rate for PTCA was not due to complications of
the procedure itself.  Those with diabetes are known to have an
excessive cardiovascular risk and a higher mortality rate was
expected for them, regardless of revascularization procedure.
However, the excess mortality with PTCA had not been anticipated.

BARI's results indicate that CABG should be the preferred
treatment for patients with diabetes on drug or insulin therapy who
have multivessel coronary artery disease and need a first coronary
revascularization.  These results have a significant impact on the
clinical care of these patients.

Coronary revascularization plays an important role in the
treatment of clinically severe coronary artery disease.  The two
most commonly used methods of revascularization are CABG and PTCA.
PTCA is a catheter-based nonsurgical approach that directly targets
coronary obstructions by dilation of the vessel at the point of
obstruction. The process is accompanied by local vascular injury and
subsequent healing.  The extent of injury and the healing process
may be different in diabetic and nondiabetic patients.  Not all
lesions can be dilated, due largely to technical reasons.  CABG is a
major operation, requiring opening of the chest.  It provides a new
channel, with a lumen frequently larger than the native, diseased
lumen.  There is no instrumentation of the local lesion and,
therefore, no related vascular injury.  While both treatments
alleviate the effects of coronary artery disease, they do not
correct or alter the natural course of the disease.

Before PTCA, CABG was the traditional revascularization
strategy. But PTCA, first performed in the United States in 1977,
has grown rapidly in use.  In 1993, about 362,000 PTCAs were done in
the United States, compared with about 309,000 CABG surgeries.

However, PTCA use has expanded not just in number but also in
the type of patient treated.  Initially, PTCA was done on patients
with one obstructed vessel.  But, with increased physician expertise
and an improved technology, PTCA use has rapidly expanded to include
patients with more complex, multivessel coronary obstructions, once
treated exclusively with CABG.  This has led to uncertainties about
the longterm effectiveness and safety of PTCA compared with CABG and
prompted the NHLBI to fund a rigorous evaluation of the two methods.

That rigorous investigation--the BARI study--tests whether the
use of PTCA as an initial treatment compromised the clinical outcome
for patients with multivessel coronary artery disease who needed
revascularization and could be treated by either PTCA or CABG.  BARI
did not test outcomes for repeat procedures.  It also studied only
PTCAs performed with the standard balloon technique.

The trial is the largest randomized study of its type, with
enough patients to be able to address key endpoints, both overall
and in predetermined patient subgroups.  The subgroups were based on
patients' anginal status, number of diseased vessels, and left
ventricular function.  Also studied are various demographic factors
such as gender, age, race, and the presence of diabetes.

The primary endpoint is mortality after 5 years of followup.
Other important endpoints include the occurrence of a myocardial
infarction, need of repeat revascularization procedures, angina,
functional status, quality of life, and utilization of health-care
resources.  (Both quality of life and utilization of health-care
resources are studied in detail in a separately funded ancillary
study.)

Patients were eligible for the trial if they had coronary
artery disease with a 50 percent or more luminal obstruction (as
measured by calipers) in at least two of the coronary vessels
supplying two or three major coronary territories.  They also had to
have clinically severe ischemia but not a prior revascularization.
Patients were ineligible for the trial if they had, for example,
insufficient angina or ischemia, required emergency
revascularization, left main stenosis of 50 percent or greater, a
noncardiac illness expected to result in limited survival, primary
coronary spasm, or a poor quality angiogram. Baseline angiograms
were reviewed and classified by the Central Radiographic Laboratory
(Dr. Edwin L. Alderman, director) at the Stanford University Medical
Center in Palo Alto, CA.

Between August 1988 and August 1991, 18 clinical centers
randomized 1,829 patients, ages 17 to 80 and including 353 on drug
treatment for diabetes.  Half of the patients were randomly assigned
to PTCA and the other half to CABG.  At baseline, the mean age of
the randomized patients was 61 years.  Thirty-nine percent of the
randomized patients were age 65 or older, 27 percent were women, 25
percent were classified as having diabetes (of these, 76 percent
were being treated with oral hypoglycemic agents or insulin), 60
percent had two-vessel disease and 40 percent had three-vessel
disease, and 98 percent had angina (of these, 64 percent had
unstable angina and 17 percent had class 3-4 angina).  At the time
of this alert, 66 percent of patients had completed followup.
Patients will be followed for a minimum of 7 years.  The trial is
expected to finish followup on all patients by November 1998.

Followup includes annual functional status assessments and an
electrocardiogram (ECG), and a biennial exercise stress test.  As
required by the protocol, risk factor modification was initiated for
all patients after their enrollment.  This includes help with
smoking cessation, exercise, and diet.  Patients also were treated
as needed for hypertension, elevated blood cholesterol, and
diabetes.  Risk factors and medical problems were managed by each
patient's primary care physician.

The trial has been closely monitored by both the study chairman
(Dr.  Robert Frye, Mayo Clinic Foundation), the Clinical
Coordinating Center (Dr. Katherine Detre, University of Pittsburgh),
and the independent Data and Safety Monitoring Board (chaired by Dr.
J. David Bristow, Oregon Health Sciences University).  The Data and
Safety Monitoring Board is composed of PTCA experts, cardiovascular
surgeons, clinical cardiologists, and experts in biostatistics and
ethics.  The Board regularly reviews the monitoring reports.  ECG
analyses are being done by the Central ECG Laboratory (Dr. Bernard
R. Chaitman, director) at the St.  Louis University Medical Center.
An independent Mortality and Morbidity Classification Committee
(chaired by Dr. Ronald Prineas, University of Miami) categorizes
fatal events in the trial.

On September 13, 1995, the Data and Safety Monitoring Board
held an urgent session to review the 5-year mortality data.  The
Board concluded that the unfavorable mortality results for the
patients on drug treatment for diabetes and first treated with PTCA
were unlikely to be due to chance.  The Board recommended to the
National Institutes of Health that physicians and other health care
professionals and the public be promptly informed of the results.

In summary:  BARI's findings should not be applied to all
persons with diabetes.  They apply only to those on oral
hypoglycemic agents or insulin for diabetes and who have multivessel
coronary artery disease and are undergoing an initial
revascularization procedure.  The data offer the following
guidelines for such patients: They will probably fare better with
CABG than PTCA as an initial treatment.  For patients who have
already had a PTCA and are asymptomatic--experiencing no ischemia,
angina, or other symptom--they should take no special action but
continue their regular care.  Alternatively, if they have already
had a PTCA and had their ischemia return (e.g., reappearance of
angina), they should consult their physicians to assess their
current health status and review optimal strategies for further
care.  Close physician monitoring is particularly important for
patients with diabetes who have coronary artery disease, since they
may not experience symptoms during periods of ischemia.

Finally, all patients who have evidence of coronary artery
disease, with or without a prior PTCA or CABG, should receive an
aggressive approach to medical management of known risk factors for
coronary artery disease, including smoking cessation for smokers,
appropriate control of elevated blood pressure or serum cholesterol,
and optimal control of diabetes.

The full text of this alert has been mailed to all libraries
that are members of the National Network of Libraries of Medicine.