WEDNESDAY AFTERNOON, APRIL 20, 1977
2:00 P.M. Scientific Session Grand Ballroom
31. Preliminary Survival Data Following a
Randomized Trial of Aorto-Coronary Saphenous Vein Bypass
RAYMOND C. READ, HERBERT HULTGREN*, KATHERINE DETRE*
and TIMOTHY TAKARO, Little Rock, Arkansas; Palo Alto, California;
West Haven, Connecticut and Asheville, North Carolina
1,015 men with chronic angina pectoris for 6 months, an
abnormal resting or exercise electrocardiogram, and angiographic evidence >
75% occlusion of one or more major graftable coronary arteries and acceptable
ventricular function, (>50% had had MI) were entered by 13 hospitals into a
prospective study comparing medical versus surgical treatment. 474/507
designated for operation received surgery with a 30 day mortality of 9.3%.
During the initial "learning" period (1970-71), 16% of 162 patients died. This
mortality fell during the later 3 years (312 patients) to 5.7%. Because of the
influence of early surgical mortality on outcome, randomization was re-instituted
in 1972, therefore, surgical and medical results have been compared for the
later 3 years of the study. As reported earlier (Circ. 52:143, 1975) patients
with left main coronary artery disease did have significantly better cumulative
survival with surgery, p. value <0.05. However, the survival rate for other
sub-groups of patients (1,2,3 vessel disease with or without abnormal left
ventricular function) while differing with respect to each other has not yet (2
to 5 years later) demonstrated statistically significant improvement with
surgery.
Vein graft patency obtained in 81% of cases one year
after operation was 71%. 89% of patients had at least one graft patent.
*By invitation
32. Pressure-Flow Characteristics of the Coronary
Collateral Circulation During Cardiopulmonary Bypass: Effects of Hemodilution
LEONARD H. KLEINMAN*, JOHN W. YARBROUGH* and
ANDREW S. WECHSLER*, Durham, North Carolina,
Sponsored by: DAVID C. SABISTON, JR., Durham, North Carolina
Hemodilution is employed
frequently during cardiopulmonary bypass (CPU). Previous investigators have
shown that perfusion and oxygenation of major vascular beds supplied by normal
arteries will be maintained during hemodilution by increasing organ flow.
However, the effects of hemodilution on myocardial regions supplied by
collateral vessels have not been determined. Thus, twelve dogs were subjected
to hemodilution during normothermic CPB; Group I normal hearts supplied by
normal coronary arteries and Group II collateralized hearts (ameroid model)
consisting of a region of myocardium supplied by collateral vessels (CR) and a
region of myocardium supplied by normal coronary arteries (NR). Regional
myocardial blood flow was determined by tracer microspheres. Retrograde
coronary pressure was measured in the collateralized hearts by can-nulation of
the circumflex artery distal to the ameroid induced occlusion. Data were
collected in the empty beating state at hematocrits (hcts) of 39 ± 1.6 and 20 ±
.7 vols % with perfusion pressure maintained at 80 mm Hg and PO2 and
heart rate held constant. Most significant changes are presented below (mean ±
SEM).
|
|
Subendocardial Flow
|
cc/min/gm
|
Subepicardial Flow
|
|
|
|
40
|
hct
|
20
|
P
|
40
|
hct
|
20
|
P
|
|
NH
|
.73 ± .06
|
3.63 ± .50
|
<.01
|
.64 ± .03
|
2.91 ± .40
|
<.01
|
|
NR
|
.81 ± .16
|
2.03 ± .24
|
<.01
|
.79 ± .17
|
1.61 ± .30
|
<.01
|
|
CR
|
.48 ± .10
|
.88 ± .37
|
NS
|
.59 ± .08
|
1.24 ± .26
|
<.01
|
|
|
|
|
|
|
|
|
|
|
|
In the collateralized hearts, the subendocardial
flow difference between NR and CR which existed at 40 vols % was markedly
exaggerated at 20 vols % (p <.01), even though hemodilution did not result
in a subepicardial flow difference. With hemodilution, retrograde coronary
pressure decreased from 45 ± 5 to 29 ± 4 (p <.05), as perfusion pressure was
held constant. These data suggest that during CPB, hemodilution is associated
with an increasing perfusion defect in regions of myocardium supplied by
collateral vessels and therefore, the subendocardium does not receive the flow
increase necessary to maintain oxygen delivery at pre-hemodilution levels. This
may result in prolonged periods of impaired regional oxygen delivery in
patients with known coronary artery disease subjected to hemodilution during
corrective surgery.
*By invitation
33. Does Coronary Bypass Increase Longevity?
O. WAYNE ISOM, FRANK C. SPENCER, EPHRAIM CLASSMAN*,
JOSEPH N. CUNNINGHAM*, PHYLLIS TEIKO*,
GEORGE E. REED and ARTHUR D. BOYD, New York, New York
The principle question with coronary bypass is its
influence on longevity. To investigate this, 1,174 consecutive patients
undergoing elective coronary bypass surgery at New York University between 1968
and 1975 have been recently studied (98% follow-up). Most patients were
operated on for disabling angina refractory to medical therapy. Patients
undergoing concomitant valve replacement, ventricular aneurysmectomy, and
emergency bypass surgery were excluded from this analysis.
The overall operative mortality was 5.2%, decreasing
from 28% in 1968 to two to three percent in the last three years (1972-1975).
Multiple grafts (two to six) were used in 88% of the group. Angina was cured or
greatly improved in 92% of the surviving patients.
The five-year survival (computed by lifetable analysis
including operative deaths but excluding late non-cardiac deaths) was quite
high, 88%. Only 49 deaths from cardiac causes occurred after leaving the
hospital in the entire group of 1,174 patients. Non-fatal myocardial
infarctions were similarly uncommon, 2.6% per year (actuarial analysis).
These data show a better
survival than previous surgical reports (average late mortality of three
percent per year) and a much greater survival than medically treated patients
with double or triple disease (five-year mortality of 35% and 55%
respectively). The significance of these findings will be discussed in detail.
*By invitation
34. Results of Combined Coronary Endarterectomy
and Coronary Bypass for Diffuse Coronary Artery Disease
MARK S. HOCHBERG*, WALTER H. MERRILL*, LAWRENCE L.
MICHAELIS and CHARLES L. McINTOSH*, Bethesda, Maryland
The treatment of diffuse distal coronary artery
disease is presently unsatisfying. Coronary artery bypass grafting (CABG) is
usually not successful in these circumstances.
Mechanical endarterectomy of a distal coronary artery
combined with CABG has been performed 21 times at this institution. Follow-up
catheterization six months after operation revealed that 11 of the 15 grafts
studied were patent (73%). Eleven endarterectomies were performed to the distal
right coronary artery, two to the distal left anterior descending coronary
artery, and one each to the circumflex and diagnonal coronary arteries. The
average flow in these patent grafts at the time of operation was 92 ml/min
(range 30-200 ml/min). Intraoperatively, the four non-patent grafts had flows
of 5-30 ml/min. All of these 15 patients had concomitant CABG's without
endarterectomy to other coronary arteries. There were two perioperative
myocardial infarctions. There were no early or late deaths.
A literature survey shows that 447 CABG's constructed
to endarterectomized coronary arteries have undergone postoperative
catheterization. Three hundred fifty (78%) of these grafts were patent from
three months to two years following surgery. Histologic studies demonstrate
that a neo-intima is formed over the endarterectomized surface. Neither
thrombosis nor the recurrence of atherosclerosis seems to be the problem that
many have feared.
Every surgeon who performs coronary bypass grafts is
often unfortunately surprised to find an angiographically attractive artery
unsuitable for bypass upon exploration in the operating room. Endarterectomy of
coronary arteries alone has not proved to be of lasting value for this problem.
However, the present series, as well as the combined series from the
literature, lends encouraging support to the value of endarterectomy plus
coronary artery bypass grafting for the treatment of a diffusely diseased
distal coronary artery.
*By invitation
35. Atherosclerosis in Vein Bypass Grafts After
Three Years - Implication on Indications and Prognosis in Coronary Surgery
ROBERT J. FLEMMA,
JOSEPH BARBORIAK*, GEORGE E. BATAYIAS*.
MICHAEL KORNS*,
DONALD C. MULLEN and
DERWARD LEPLEY, JR.,
Milwaukee, Wisconsin
Approximately 100 patients who underwent coronary
vein bypass grafting have had removal of their vein grafts beyond three years
from insertion either at autopsy or reoperation. A high percentage had
atherosclerotic involvement of the vein bypass grafts as a major pathologic
finding. The implication of this atherosclerotic involvement, which is
identical to that seen in arteries, on the long term fate of coronary vein
bypass grafting is obvious. We found there was a positive correlation in these
patients between elevated serum cholesterol and triglycerides and
atherosclerosis in vein bypass grafts.
These cases are not a random sample as they were selected
by death or closure of vein grafts and atherosclerosis may occur in only a
small percentage of all patients. However, the ominous portent on the long term
fate of vein grafts demands that a vigorous effort be made to determine the
exact incidence of atherosclerosis occurring in vein bypass grafts and the
identification and categorization of risk factors that might help elucidate the
mechanism for this atherosclerosis. A model identification and follow-up
program to achieve this will be presented that will allow for accumulation of
considerable data in a short time.
*By Invitation
