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19 декабря 2001 00:00   |   John D. Puskas, MD, Carolyn E. Wright, MS, Russell S. Ronson, MD, W.

Clinical Outcomes and Angiographic Patency in 125 Consecutive

 
ABSTRACT
 
Background: This study compared clinical outcomes, length of stay,
and hospital costs in patients having off-pump coronary bypass
(OPCAB) versus conventional bypass surgery (CABG).
Methods: From November 1996 through April 9, 1999, OPCAB was 
 
performed for 125 consecutive patients and compared with a 
 
contemporaneous, matched control group of 625 CABG patients.
Patients were matched according to age, gender, incidence of renal
failure, diabetes, pulmonary disease, stroke (CVA), hypertension,
peripheral vascular disease, and previous myocardial infarction.
Follow-up in the OPCAB patients was 100% and averaged 15 months.
Results: An average of 2.0 grafts per patient were performed in the 
 
OPCAB group (range 1−5). Ninety-four OPCAB patients (75.2%) had a 
 
total of 179 grafts assessed angiographically prior to hospital
discharge. All but 4/179 grafts (2.2%) were patent , including 94 of 
 
94 IMA grafts (100%) . There were no in-hospital deaths in the OPCAB
group compared to a mortality rate of 1.4% in the CABG group. OPCAB
reduced postoperative hospital stay from 5.5 days in the traditional
CABG group to 3.3 days (p=.002), with a decrease in hospital cost of 
 
24% (p=.01). In addition, there was a significant reduction in the 
 
rate of transfusion in the OPCAB group (29.6%) compared to the CABG 
 
group (56.5%, p=.0001). Two OPCAB patients required postoperative
intervention to improve graft patency during the follow-up period.
No internal mammary grafts required revision. There was one 
 
perioperative CVA and one myocardial infarction in the OPCAB group.
Conclusions: OPCAB surgery reduces hospital cost, postoperative
length of stay , and transfusion rate compared to CABG. OPCAB is 
 
safe, cost effective, and associated with excellent graft patency
and clinical outcomes.
 
INTRODUCTION
 
 
In an attempt to avoid the deleterious effects of cardiopulmonary
bypass (CPB), off-pump coronary bypass surgery has recently been 
 
rediscovered and refined. Coronary artery bypass graft surgery was 
 
first performed without the use of extracorporeal circulation in the 
 
late 1960s [Kirklin 1983]. This technique was largely abandoned
after the use of CPB and cardioplegic arrest became routine [Buffolo
1996].
Blood contact with artificial surfaces on the CPB circuit produces
 
well-documented diffuse inflammatory response which affects multiple
organ systems. Specific deleterious effects of the inflammatory
response have been documented in the heart, lungs, central nervous
system, kidneys, and gastrointestinal tract. Virtually all 
 
detrimental effects of this diffuse inflammatory response increase
with increased duration of CPB [Edmunds 1997]. Also associated with 
 
increased CPB time are increased hospital costs and length of stay 
 
[Puskas 1998].
Multiple previous authors have reported series of off-pump CABG 
 
[Benetti 1995, Buffolo 1996, Calafiore 1996, Calafiore 1998,
Bergsland 1998, Hart 1999]. While these authors have reported
excellent mortality rates, concern has been raised of a decrement in 
 
graft patency rates [Subramanian 1997]. We previously described the 
 
early evolution of the off-pump coronary bypass operation at our 
 
institution, and reported outcomes in 51 off-pump patients to 
 
determine the safety and efficacy of off-pump coronary surgery
[Puskas 1998]. The present study reports clinical outcomes and 
 
angiographic patency in 125 consecutive off-pump patients and 
 
compares these results to a computer-matched control group having
CABG on cardiopulmonary bypass.
 
MATERIALS AND METHODS
 
 
The off-pump group included 125 patients who presented from November
1996 through April 9, 1999 and underwent OPCAB by a single surgeon
at Crawford Long Hospital of Emory University. The comparison group
was a computer-matched control group derived from the Emory
University Cardiac Surgical Database. For each off-pump patient, the 
 
computer generated five control patients matched for age, gender,
and pre-existing disease, having primary coronary bypass surgery by 
 
the authors at the same institution during the same time period.
Pre-existing disease variables included history of hypertension,
diabetes, renal insufficiency (creatinine greater than 2.0 mg/dl),
previous stroke, chronic obstructive pulmonary disease, peripheral
vascular disease, and previous myocardial infarction.
During the first few months of the study period, the procedure was 
 
accomplished via minithoracotomy (MIDCAB; N = 9 patients) as 
 
previously described [Puskas 1998]. The surgical technique then 
 
evolved from a minithoracotomy to a median sternotomy incision. This 
 
was prompted by concern about precision and safety with the limited
exposure afforded by minithoracotomy and by the very limited number
of patients referred for surgical management of single-vessel
disease at our institution. The remaining 116 patients underwent the 
 
off-pump operation through a median sternotomy incision. The 
 
internal mammary artery (IMA , right or left) was harvested under
direct vision. Heparin administration has also evolved and now 
 
consists of a full pump dose of 400 units/kg administered prior to 
 
division of the internal mammary artery. This is partially reversed
with a half dose of protamine (typically 1mg/kg) after completion of 
 
the last anastomosis. One of several commercially available
mechanical stabilizing devices was used for stabilization of the 
 
coronary target(s) on the beating heart (United States Surgical,
Norwalk CT; Cardiothoracic Systems, Cupertino CA; Medtronic Octopus
II, Minneapolis MN; Genzyme, Boston MA). The target coronary
arteries were occluded proximally with a silastic vessel loop, and 
 
retrograde bleeding was controlled with a sterile, humidified carbon
dioxide blower. Distal anastomoses were constructed with 7−0 or 8−0 
 
monofilament suture. Proximal anastomoses were sewn to the aorta
under a partial occlusion clamp with 5−0 or 6−0 suture.
Intraoperative epiaortic ultrasound was performed to rule out 
 
significant atherosclerosis of the ascending aorta prior to 
 
application of the clamp. Evidence of significant atherosclerosis
(Grade III or higher) prompted alternative construction of proximal
anastomoses on the LIMA pedicle.
Data reflecting intraoperative and postoperative variables were 
 
collected for comparisons. These data included the number of distal
grafts, use of the internal mammary artery as a conduit,
intra-aortic balloon pump, inotropic support for more than 48 hours
postoperatively, intubation for greater than 48 hours following
surgery, postoperative myocardial infarction, stroke, sternal wound
infection, leg wound infection, renal failure, re-exploration for 
 
bleeding, transfusion requirements, atrial and ventricular
arrhythmias, postoperative length of stay, and hospital costs
associated with the operation.
In the early experience, any patient with a postoperative complaint
remotely suggestive of angina underwent angiography. Later, all 
 
OPCAB patients were requested to consent to postoperative
angiography under our institutional quality assurance protocol.
Patients with preoperative renal insufficiency or severe
calcification/atherosclerosis of the ascending aorta were excluded
from postoperative angiography. In several other cases, patients or 
 
referring cardiologists refused postoperative catheterization. A 
 
total of 94 of the off-pump patients (75.2%) had coronary
angiography to document graft patency prior to hospital discharge.
None of the control patients had postoperative angiography.
Measures of central tendency, inferential, and multivariate
statistics were used for the data analysis. The frequency, mean, and 
 
standard deviation were calculated for the independent and dependent
variables. The Student's t-test was used for two-group comparisons
with continuous variables. Chi-Square was used for comparisons with 
 
categorical variables. Comparisons between the two groups were made 
 
by using logistic regression for the dichotomous dependent
variables. Multiple regression was used as a means to identify
independent predictors of length of stay and hospital charges. An 
 
alpha level of .05 was used to determine significance [Bailar 1992].
 
 
RESULTS
 
 
All off-pump patients (thoracotomy and sternotomy approaches) were 
 
grouped together and compared with control patients having CABG on 
 
CPB. The off-pump group consisted of 125 patients, and the control
group included 625 patients for a total sample of 750 patients. The 
 
two groups were compared on the basis of age, gender, and all seven
comorbidities listed above to ensure that the two groups were 
 
appropriately matched [see Table 1]. The mean age was 61.0 years
(31% female and 69% male) for the off-pump group and 61.4 years for 
 
the control group (27.5% female and 72.5% male; p=.4). The groups
differed only in preoperative chronic obstructive pulmonary disease
(COPD) (25.6% OPCAB vs 20% traditional CABG; p = .04).
Table 2 compares clinical outcomes between the two groups. No 
 
patient in the off-pump group had to be converted to CPB during the 
 
procedure. The mean number of distal anastomoses was significantly
higher in the control group (3.6 grafts per patient) when compared
with the OPCAB group (2.0 grafts per patient; p = .001).
There were no hospital deaths in the OPCAB group (0%) while there
were nine in the control group (0.64%). These results did not reach
statistical significance. Postoperative complications are presented
in Table 3. There was only one myocardial infarction in the OPCAB
patients (0.8%) as compared with an incidence of 0.5% in those
recieving traditional CABG (NS). A completed stroke occurred in 0.8%
of the off-pump group versus 1.8% of patients with traditional CABG 
 
with CPB. There was also a significant reduction in postoperative
inotropic support and intra-aortic balloon pump use in the off-pump
group. Interestingly, there was no difference in the incidence of 
 
atrial fibrillation between groups, despite the absence of atrial
sutures, cannulation, and extracorporeal circulation in the off-pump
group. Both groups received a similar postoperative regimen of 
 
tapering beta-blockade for prophylaxis against atrial fibrillation.
A striking difference was found between groups in the incidence of 
 
postoperative transfusion requirements [see Table 4]. While more 
 
than half of the patients in the control group required transfusion
of some blood product(s) during their hospitalization, less than 
 
one-third of the off-pump group received any blood products (p <
.0001).
Ninety-four of the off-pump patients (75.2%) had repeat coronary
angiography prior to discharge: 175/179 grafts (97.7%) were widely
patent, 3/179 were totally occluded (1.6%; all vein grafts to 
 
diagonal targets), and 1/179 anastomoses was narrowed > 50% (0.5%;
one vein graft to a posterior descending artery). All 94 internal
mammary graft anastomoses were widely patent [100%; see Table 5 
 
:574:]. One patient had asymptomatic occlusion of a vein graft to a 
 
diagonal target, with a widely patent LIMA-left anterior descending
coronary artery (LAD) graft. One patient with undiagnosed protein C 
 
and S deficiencies had uneventful three-vessel OPCAB complicated by 
 
acute thrombosis of two vein grafts to diagonal coronary targets and 
 
suffered a perioperative anterior myocardial infarction (MI). An 
 
IABP was placed and she had urgent reoperation on CPB, with 
 
replacement of her vein grafts. Subsequent repeat postoperative
catheterization documented patency of her original LIMA and both 
 
reoperative vein grafts. She was discharged home on aspirin and 
 
warfarin under the care of a hematologist. One patient had 
 
asymptomatic stenosis of a vein graft to a small posterior
descending coronary artery. All other graft anastomoses were widely
patent on postoperative catheterization.
Dramatic differences in total postoperative length of stay and 
 
hospital costs were found between groups [see Table 6]. Length of 
 
stay was reduced by 40%, while hospital costs fell by 24% for the 
 
off-pump group. CPB was found to be an independent predictor of 
 
increased hospital cost and increased postoperative length of stay.
The multiple regression model for length of stay had a multiple R of 
 
0.49, R squared of 0.24, F = 17.73, p=.00001. Significant variables
which contributed to the model of length of stay were CPB, atrial
arrhythmia, prolonged intubation, inotropic support > 48 hours,
sternal wound infection, and transfusion requirement. Additional
variables analyzed which were not independently significant included
re-exploration for bleeding, postoperative renal failure,
postoperative stroke, and postoperative MI. When mortality was 
 
included in the length of stay model, death was a significant
independent predictor [see Table 7].
The following variables contributed to a significant model
predicting hospital cost: CPB, postoperative renal failure,
transfusion, prolonged intubation and inotropic support,
intra-aortic balloon pump, pre-existing COPD, and the presence of 
 
any complication. Variables entered into the regression equation
that were not independently significant included the number of 
 
grafts, postoperative stroke, and postoperative MI. The multiple R 
 
was 0.62, R squared was 0.38, F = 19.9, p=.00001 for the cost model
[see Table 8].
Follow-up was 100% complete for the 125 OPCAB patients. (The 
 
conventional CABG patients matched from the database served as 
 
controls for comparisons of perioperative events. There was no 
 
follow-up of these control patients after hospital discharge.) All 
 
OPCAB patients were telephoned and questioned regarding any 
 
recurrent angina, myocardial infarction, cardiac reintervention,
hospital readmission, wound complications, infections, etc.
Follow-up ranged from one month to 29 months, with a mean of 15 
 
months.
Two patients developed recurrent angina in the OPCAB group.
 
67−year-old smoker with oxygen-dependent COPD and bilateral carotid
occlusions had an uneventful three-vessel OPCAB and was readmitted
to hospital with chest pain 12 months postoperatively. Cardiac
catheterization revealed a LIMA string sign and occlusion of the 
 
saphenous vein graft to the right coronary artery. The diagonal vein 
 
graft was widely patent, and the patient was managed medically.
Another patient very early in our experience had an OPCAB single
vessel vein graft to an intramyocardial ramus intermedius target.
Early angiography demonstrated that the graft was patent, but had 
 
been misplaced to a small branch of the intended vessel. This graft
closed six weeks after discharge, and PTCA was performed to the 
 
ramus intermedius, with resolution of angina symptoms.
There was one death after hospital discharge in the OPCAB group.
This 81−year-old woman with COPD (oxygen-dependent, FEV1 = 0.48 L),
a porcelain aorta, moderate mitral regurgitation, and a 90% ostial
left main lesion had a single vessel OPCAB with LIMA-LAD. She was 
 
discharged on postoperative day six and expired at home less than 30 
 
days after hospital discharge. All other OPCAB patients are alive
and well without angina at mean follow-up 15 months.
 
DISCUSSION
 
 
Pioneered by Benetti and Buffolo in South America almost twenty
years ago, CABG without CPB has been recently rediscovered and 
 
continues to be refined. Off-pump CABG via sternotomy can now be 
 
performed for lesions in virtually any coronary artery with 
 
presently available instrumentation and a high degree of patient
safety and surgeon comfort. Clinical and angiographic results
described above support this statement. No patient in the off-pump
group had to be converted to CPB during the procedure. Surgical
management of lesions in the left circumflex territory formerly
required cardiopulmonary bypass at this institution and limited the 
 
proportion of coronary cases which could be performed off-pump to 
 
less than 20%. We have considered complete revascularization to be 
 
the «gold standard» for coronary bypass surgery irrespective of the 
 
surgeon's choice of incision or use of cardiopulmonary bypass, and 
 
still hold this belief. Incremental improvements in surgical
technique, including the routine use of wide bilateral transverse
diaphragmatic pericardiotomies, multiple deep pericardial traction
sutures and rotation of the heart into the right pleural space have 
 
recently allowed visualization of obtuse marginal coronary targets
in a high proportion of patients. This has led to a recent sharp
increase in the number of grafts per patient in the OPCAB group [see
Figure 1]. The very recent commercial introduction of improved
mechanical stabilizer devices has also contributed significantly to 
 
a fundamental shift towards OPCAB [see Figure 2]. Presently, over 
 
80% of all CABG cases may be safely done off-pump by an experienced
OPCAB surgeon, including those requiring grafts to the obtuse
marginal branches of the left circumflex artery .
The preoperative differences between the OPCAB and CABG groups [see
Table 1] reflect the evolving bimodal pattern of patients referred
specifically for OPCAB. The first is a small group of young, healthy
patients who have failed PTCA for single or double vessel disease
and the second, a growing number of older, sicker patients with 
 
relative or absolute contraindications to cardiopulmonary bypass.
This latter group has multiple severe comorbidities, often including
pre-dialysis renal failure, oxygen-dependent COPD, and morbid
peripheral vascular disease including unilateral or bilateral
carotid occlusion. These patients often have been refused CABG in 
 
the past. Thus, the incidence of severe COPD in the OPCAB group was 
 
so high compared to patients undergoing conventional CABG that the 
 
Emory University Cardiac Surgical Database could not match
completely for this variable, given the other constraints imposed in 
 
the matching program. This resulted in the observed preoperative
difference between groups with respect to incidence of COPD.
The emphasis of minimally invasive cardiac surgery is on less 
 
invasive techniques which may decrease cost, length of hospital
stay, and the overall morbidity associated with cardiac surgery. As 
 
older, sicker patients are referred for coronary bypass surgery, an 
 
increasing proportion of patients may have relative
contraindications to CPB. The present study demonstrated that CPB is 
 
a statistically significant independent predictor of hospital cost 
 
and length of stay.
The early angiographic patency rates presented here equal or exceed
all published series for coronary bypass on CPB, and are encouraging
relative to many earlier series of MIDCAB and OPCAB results [Mack
1998]. All 94 internal mammary anastomoses and all but 4 of 179 
 
total grafts studied prior to hospital discharge were widely patent.
This is clear evidence that careful technique and use of advanced
mechanical stabilizer devices permit reproducible, precise
construction of coronary bypass anastomoses on the beating heart.
All routine conduits (LIMA, RIMA, radial artery, saphenous vein)
were used in this series to bypass all named coronary targets,
including the obtuse marginal branches of the left circumflex
coronary artery. Clinical outcomes during a mean 15 months of 
 
follow-up strongly suggest that these excellent early outcomes in 
 
the OPCAB group are maintained over time. Nonetheless, the 
 
conclusions from this series are weakened by its short period of 
 
follow-up and its retrospective and non-randomized nature, despite
the use of a computer-generated contemporaneous control group
matched for multiple indices of perioperative risk. Only a large,
prospective, randomized, longitudinal comparison of graft patency
and clinical outcomes after coronary bypass surgery performed with 
 
and without the use of cardiopulmonary bypass can ultimately
validate the safety, efficacy, and superiority of the off-pump
approach.
 
AUTHOR/ARTICLE INFORMATION
 
 
Presented at the Annual Meeting of the International Society for 
 
Minimally Invasive Cardiac Surgery, Palais d&eacute;s Congres, Paris,
France , May 21−22, 1999.
Reprint requests to: John D. Puskas, MD, MSc, Assistant Professor of 
 
Surgery, Emory University, Carlyle Fraser Heart Center, Crawford
Long Hospital, 550 Peachtree Street, NE, Suite 7700, Atlanta, GA 
 
30365; Phone: 404−686−2513; Fax: 404−686−4959; e-mail address:
jpuskas@emory.edu
Submitted on: Peer reviewed and accepted at the International
Society for Minimally Invasive Cardiac Surgery's 2nd Annual Meeting
and Scientific Sessions, Paris, France, May 21−22 1999.
 
REFERENCES
 
 
1. Bailar JC, Mosteller F. Medical uses of statistics (2nd edition).
Boston: NEJM Books, 1992.
2. Benetti FJ, Ballester C, Sani G, Doonstra P, Grandjean J. Video
assisted coronary bypass surgery. J Card Surg 10:620−5, 1995.
MEDLINE
3. Bergsland J, Schmid S, Yanulevich J, Hasnain S, Lajos TZ, Salerno
TA. Coronary artery bypass grafting (CABG) without cardiopulmonary
bypass (CPB): a strategy for improving results in surgical
revascularization. Heart Surgery Forum #1998−1593; 1(2):107−110,
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4. Buffolo E, de Andrade JCS, Branco JNR, Teles CA, Aguiar LF, Gomes
WJ. Coronary artery bypass grafting without cardiopulmonary bypass.
Ann Thorac Surg 61:63−6, 1996. MEDLINE
5. Calafiore AM, Angelini GD, Bergsland J, Salerno TA. Minimally
invasive coronary artery bypass grafting. Ann Thorac Surg 62:1545−8,
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6. Calafiore AM, Di Giammardo G, Teodori G, Mazzei V, Vitolla G.
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McGraw-Hill, 255−94, 1997.
8. Gott JP, Cooper WA, Schmidt FE, et al. Modifying risk for 
 
extracorporeal circulation: trial of four anti-inflammatory
strategies. Ann Thorac Surg 66:747−54, 1998. MEDLINE
9. Hart JC, Spooner T, Edgerton J, Milsteen SA. Off-pump multivessel
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effective. Ann of Thorac Surg 66:1068−72, 1998. MEDLINE
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coronary artery bypass grafting: two-year clinical experience
clinical experience. Ann Thorac Surg 64:1648−55, 1997. MEDLINE

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