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Left ventricular performance and graft patency after coronary artery-saphenous vein bypass surgery: Early and late follow-up
Clinical communications Left ventricular performance and graft patency after coronary artery-saphenous vein bypass surgery: Early and late follow-up Carl S. Apstein, M.D. Susan A. Kline, M.D. David C. Levin, M.D. Harold A. Baltaxe, M.D. Thomas Killip, M.D. New York, N. Y.
Coronary artery-saphenous vein bypass graft surgery is currently being advocated as a form of treatment for coronary artery disease, but the long-term effects of this operation on ventricular function have not been clearly established. 1, 2 Early postoperative improvement has been reported in selected patients with acute myocardial ischemia2 ~4 Improved function in the early postoperative period implies the preoperative presence of ischemic and depressed, but viable, myocardial tissue. Patients with impaired left ventricular performance due to chronic, stable coronary artery disease have not generally demonstrated a sustained improvement in postoperative ventricular function, 5~1~although early postoperative ventricular function improvement in this group of patients has also been reported.~3. ~4 The patency of the bypass coronary grafts and of the native coronary circulation is an important determinant of postoperative myocardial function. 1~16 Rapid progression from partial to complete occlusion in the proximal segments of grafted coronary arteries and progressive intimal fibrous proliferation of the vein grafts have been reported. 17-1s Postoperative graft patency is related to the rate of flow through the graft at the time of surgery, ~~but this measurement can only be made after surgery is performed. From the Departments of Medicine and Radiology, The New York Hospital-Cornell Medical Center, New York, N. Y. Received for publication Nov. 24, 1975. Reprint requests: Carl S. Apstein, M.D., Boston University School of Medicine, 80 E. Concord St., Boston, Mass. 02118.
May, 1977, Vol. 93, No. 5, pp. 547-555
Preoperative measurements which predicted the risk of postoperative graft occlusion and ventricular performance would be useful in evaluating patients for surgery. In order to evaluate long-term postoperative left ventricular performance and graft patency, and to develop predictive guidelines in these two areas, we have reviewed the pre- and postoperative angiographic studies in 26 patients who underwent coronary artery bypass graft surgery. Methods Patient material. The angiograms of 118 patients who underwent coronary artery-saphenous vein bypass graft surgery at the New York Hospital-Cornell Medical Center during a consecutive 24 month period were reviewed. The criteria for inclusion in this s t u d y consisted of technically adequate pre- and postoperative left ventriculograms, preoperative coronary arteriograms, and postoperative venograms of the bypass grafts. Patients were excluded if an aneurysectomy was done at the time of coronary artery surgery. Twenty-six patients (22 per cent) met these criteria, and form the basis of this report. Eighteen patients had a single postoperative study; eight patients underwent both early and late follow-up angiography. Thus a total of 34 postoperative studies were performed in 26 patients. Twenty-five patients were male; the average age was 51 years. The indication for surgery in each case was the presence of angina pectoris which was disabling enough to warrant surgery in the judgment of the
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Table I. Preoperative values: Late vs. no late follow-up study
Ejection fraction M e a n r a t e of circumferential shortening A t h e r o s c l e r o t i c score
Late study (n = 15)
No late study (n = 12)
P*
0.62 - 0.05 1.29 _ 0.11
0.58 _ 0.04 1.39 _+ 0.14
N.S. N.S.
6.5
5.7
N.S.
_+ 1.8
_+ 0.8
*Unpaired Student's t test.
patient and his physicians. All patients had a "stable" clinical level of angina; there were no cases of "crescendo" or "unstable angina," or the "intermediate coronary syndrome." Fifty-one grafts, or an average of two per patient, were implanted and subsequently studied. Angiographic studies. The angiographic studies evaluated the extent of preoperative coronary artery atherosclerosis, pre- and postoperative left ventricular function, and postoperative graft patency. Three patients also had postoperative coronary arteriography. Left ventricular catheterization was performed from the right femoral artery. Pressure measurements were recorded prior to the injection of contrast material. Preoperative coronary arteriography was performed with the Judkins technique. Selective saphenous vein graft angiograms were performed and examined for graft occlusion at the time of each postoperative study. If the grafts were patent, the flow pattern in the anastomosed coronary artery was characterized as unidirectional if contrast material flowed only antegrade into the artery, or bidirectional if there was also retrograde flow into the proximal segment of the grafted artery. Lack of bidirectional flow in the grafted artery was interpreted as indicating t h a t an occlusion in the proximal segment of the artery had occurred. In one case of unidirectional antegrade flow in the grafted artery, coronary arteriography demonstrated occlusion of the proximal arterial segment. Coronary arteriography was not performed in the other instances where the proximal arterial segment failed to fill from the injection into the graft. However, lack of retrograde flow in the proximal segment of the grafted artery during injection into the venous graft has generally correlated with occlusion in the proximal segment of the native coronary artery, 16 although the precise location of the site
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of occlusion cannot be delineated solely by graft angiography. After coronary arteriography, the patients were allowed to recover for approximately 30 minutes while the coronary films were developed and reviewed, after which time a left ventriculogram was performed and the ejection fraction was determined. In those patients where the left ventricular end-diastolic pressure (LVEDP) increased after coronary arteriography the ventriculogram was delayed until the LVEDP returned to the pre-coronary arteriogram value. The L V E D P usually returned to the control value within 30 minutes. This protocol should have minimized any influence upon our ventriculographic data of the effect of the contrast material injected during coronary artery or vein graft angiography. 21-23 The reproducibility of the ejection fraction (EF) measurement has been assessed by comparing angiograms performed 90 minutes before and 30 minutes after coronary angiography24; there was no significant difference between the two EF measurements. Thus our assessment of ventricular function via ventriculography performed 30 minutes after coronary arteriography should be free from the effects of the arteriography. The preoperative, early, and late follow-up studies were all performed with the same protocol. Analysis of ventricular function was performed by calculating the EF 2~-27 and the mean rate of circumferential shortening (~r ~ on normal sinus beats occurring at least two beats after premature beats. The EF obtained from the right anterior oblique ventriculograms were converted to biplane valuesJ ~ The EF was derived from the formula: EF = (EDV - ESV)/EDV, where EDV and ESV represent the end-diastolic and endsystolic volumes, respectively. The Vc~, in circumferences per second, was derived from the formula2~: Vc~ = (EDC - E S C ) / E D C / E T , where EDC and ESC represent the end-diastolic and endsystolic circumferences, respectively and ET represents the ejection time in seconds. The EF and CCcr were determined in duplicate and independently by two of the authors (C. S. A. and S. A. K.) for each patient; the values determined in this manner were in close agreement and the average is reported herein. T h u s observer-toobserver error 24 was minimized. The extent of coronary artery disease was
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Coronary artery surgery T a b l e II. Left ventricular function at early follow-up
EF
(cir./ sec.)
L VEDP (mm. Hg)
Heart rate (beats / min.)
L V systolic press. (ram. Hg)
1.32 • 0.11 1.43 • 0.12
20 • 2 14 • 1'
77 • 3 94 • 4*
138• 4 121 • 4*
78 • 3 93 _+ 8
132 • 7 119 • 4
AU patients (n = 19): Preoperative Postoperative
0.50 • 0.04 0.54 • 0.04
Patients with moderately abnormal preoperative L V function (EF: 0 . 3 0 - 0.60, n = 7): Preoperative Postoperative
0.38 • 0.04 0.47 • 0.06**
1.05 _ 0.15 1.22 • 0.14
20 • 3 16 • '2
*p < 0.01; **p < 0.05.
measured by an atherosclerotic score obtained by adding the values ascribed to each stenotic lesion in a major coronary artery. Scoring of lesions was done as follows: total occlusion = 4, 75 to 99 per cent stenosis - 3, 50 to 75 per cent stenosis = 2, less th an 50 per cent stenosis = 1, no lesions = 0. After surgery, all patients were advised to u n d er g o follow-up catheterization, regardless of their symptomatology. T he decision to have such a study rested with the patient and his own physicians. Early postoperative studies, prior to discharge from the hospital, were obtained in 19 patients with 38 grafts at an average postoperative interval of 14 days and ranging up to 4 months. Fifteen patients had a late follow-up study between 4 months and 1 year after surgery (mean = 9 months). T he patients who underwent a follow-up study are thus "selected" in the sense that they represent the survivors of the operation who consented to restudy. At the time these data were collected, 27 patients with adequate preoperative studies were long-term survivors ( > 4 months after operation). In order to ascertain whether the late restudy group was an unbiased sample of this late postoperative survivor population, preoperative measurements were compared for the 15 patients who were restudied at late follow-up and those 12 who were long-term survivors and thus candidates for restudy, but who did not consent. These groups are compared in Table I. In terms of preoperative left ventricular function and severity of coronary artery disease, the patients who returned for late follow-up study were a representative sample of all the patients operated upon who survived for at least 4 months. Statistical analysis of the data reported herein was performed with the paired or unpaired
American Heart Journal
Student's t test, as appropriate, for hemodynamic data. To analyze the significance of the different risks of graft occlusion, the value of p was calculated from a 2 by 2 contingency table with the Fisher exact probability test. ~' D at a are reported as the mean _+ standard error of the mean (S.E.M.). Results Extent of atherosclerosis. All patients in this series had significant coronary artery disease demonstrated by coronary angiography. The mean atherosclertic score for the 26 patients was 6.0. Ejection fraction was inversely related to the atherosclerotic index; the 16 patients with an ejection fraction less than 0.50 had an atherosclerotic score of 7.0 _+ 0.5; the 10 patients with an ejection fraction greater than 0.50 had an atherosclerotic score of 5.4 _+ 0.6 (p < 0.05, unpaired t test). Early postoperative studies. Ventricular function. Left ventricular function, as assessed by ejection fraction and mean rate of circumferential shortening, was unchanged at the time of the 14 day follow-up study in the group of 19 patients considered as a whole (Table II). However the postoperative L V E D P significantly decreased, heart rate increased, and peak left ventricular systolic pressure decreased. Since left ventricular peak systolic pressure was significantly lower, and heart rate was significantly higher at this time, the observed decline in L V E D P may not represent a primary improvement of myocardial function. T he group of 19 patients was separated on the basis of preoperative ejection fraction. The subgroup of seven patients with a moderately impaired preoperative ejection fraction {0.30 to 0.60) had an increase in ejection fraction at early
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Table III. Postoperative graft patency
No. of patients
No. of grafts
Studied
All grafts patent
One or more graft occlusions
9 10 19
9 5 14
0'* 5** 5
16 22 38
16 16 32
0 (0%) _66 (27%) 6 (16%)
11 4 15
8 0 8
3** 4"* 7
21 ..10 31
17 5 22
4 (19%,) __5(50%) 9 (29%)
16 10 26
13 3 16
3** 7** 10
29 22 51
25 14 39
4 (14%) 8 (37%) 12 (24%)
ImplantedlPatent I Occluded(%)
Early follow-up (<4 moO: Preoperative E F > 0.60 Preoperative E F < 0.60 Total
Late follow-up (>4 me.): Preoperative E F > 0.60 Preoperative E F < 0.60 Total
Combined early and late follow-up*: Preoperative E F > 0.60 Preoperative E F < 0.60 Total
*Each patient counted singly with data based on latest study. **P < 0.05 for risk of graft occlusion, Fisher exact test, two-tailed. 2~
follow-up, and a trend toward an increased ~?(:~.~ which was not statistically significant. The increase in ejection fraction at a lower enddiastolic pressure may indicate a slight improvement in ventricular function in these patients, but could also be due to the lower postoperative afterl0ad (LV systolic pressure) and higher heart rate. Two of the seven patients with an improved ejection fraction postoperatively had been digitalized between the pre- and postoperative studies. Thus, the finding of early postoperative improvement in the ejection fraction must be interpreted cautiously. The subgroup of nine patients who had a normal preoperative ejection fraction (greater than 0.60) had no significant change in ejection fraction at early follow-up. Three patients had a preoperative ejection fraction less than 0.20; there was no significant change at early followup. Graft patency. Thirty-eight grafts in 19 patients were studied at early follow-up (Table III). Sixteen per cent (6 of 38) of the grafts were occluded. Eighty-four per cent (32 of 38) of the grafts were patent and 30 of the Patent grafts had bidirectional flow of contrast material into the coronary artery distal to the site of anastomosis. In two cases the anastomosed coronary artery exhibited only antegrade flow of contrast material from the venous graft, indicating probable occlusion in the proximal segment of the grafted native coronary artery. Graft patency in the early postoperative period
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was r e l a t e d t o the preoperative ejection fraction. The risk of graft occlusion at early follow-up was zero if the preoperative EF had been greater than 0.60, but there was a 27 per cent risk of occlusion for each implanted graft when the preoperative ejection fraction was less than 0.60. All patients with a preoperative EF greater than 0.60 remained free of any graft occlusion, while 50 per cent of those patients with a preoperative EF of less than 0.60 suffered at least one graft occlusion. Late post-operative studies. Thirty-one grafts were studied in 15 patients at an average postoperative interval of nine months {Table III) and ventricular function was studied in fourteen of the fifteen patients {Fig. 1). Graftpatency. Nine of the grafts were occluded (29 per cent). Twenty-two grafts (71 per cent) were patent and 19 showed bidirectional flow in the anastomotic coronary artery. Three were patent, but filled only the distal portion of the grafted coronary artery indicating probable occlusion in the proximal segment of the grafted coronary artery. As with the early postoperative studies, graft patency at 9 months follow-up was associated with a normal preoperative ejection fraction. The risk of graft occlusion, when the early and late follow-up studies are considered together, was much higher for those patients with abnormal preoperative ventricular function (Table III). Over all, 51 grafts were restudied in 26 patients. In the 16 patients with a preoperative
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Coronary artery surgery E F greater t h a n 0.60, four of 29 grafts (14 per cent) were occluded; i n the 10 p a t i e n t s w i t h a p r e o p e r a t i v e E F less t h a n 0.60 t h e risk of g r a f t occlusion was 37 per cent (eight of 22 grafts). G r a f t occlusions occurred in seven of 10 p a t i e n t s who h a d a p r e o p e r a t i v e E F less t h a n 0.60, b u t in only t h r e e of 16 p a t i e n t s who h a d a p r e o p e r a t i v e E F greater t h a n 0.60. V e n t r i c u l a r function. T h e E F a n d Vcr were significantly reduced f r o m the p r e o p e r a t i v e values in the late p o s t o p e r a t i v e period in the group of p a t i e n t s considered as a whole (Fig. 1). For the t o t a l group of !ate follow-up studies, the E F decreased f r o m 0.62 + 0.05 to 0.54 + 0.05 (p < 0.01, paired t test) a n d the V~,F decreased from 1.29 + 0.11 t o 1.11 • 0.12 circumferences per second (p < 0.02, paired t test). T h e left v e n t r i c u l a r systolic pressure decreased from 130 • 6 m m . H g p r e o p e r a t i v e to 114 • 5 m m . H g p o s t o p e r a t i v e (p < 0.01, paired t test). T h e r e was no significant change in h e a r t r a t e (79 • 3 preoperative vs. 78 _+ 2 m m . H g postoperative). T h e significant decrease in E F and VcF at c o n s t a n t h e a r t r a t e and end-diastolic pressure b u t with reduced a f t e r l o a d (peak LV systolic pressure) indicates a r e d u c t i o n of v e n t r i c u l a r function in the late p o s t o p e r a t i v e period. W h e n the p a t i e n t s were divided into s u b g r o u p s on the basis of graft p a t e n c y a n d flow p a t t e r n in the grafted c o r o n a r y a r t e r y (Fig. 1), it was f o u n d t h a t the s u b g r o u p w i t h o u t graft occlusions a n d with bidirectional flow into the grafted a r t e r y h a d m a i n t a i n e d left v e n t r i c u l a r p e r f o r m a n c e at their n o r m a l p r e o p e r a t i v e level. T h e subgroup with occluded grafts or unidirectional a n t e g r a d e flow in t h e grafted a r t e r y showed a significant decrease in left v e n t r i c u l a r E F f r o m 0.59 _+ 0.07 to 0.49 • 0.07 (p < 0.01, paired t test) and in Vc~ f r o m 1.21 • 0.14 to 1.01 • 0.15 circumferences per second (p < 0.05, paired t test). Sequential studies in the same patients. E i g h t p a t i e n t s h a d follow-up studies during b o t h the early and late p o s t o p e r a t i v e periods (Table IV). This small group showed a t r e n d which was similar to the entire s t u d y group: no change in v e n t r i c u l a r f u n c t i o n at early follow-up w i t h a decrease in the late follow-up period. Six of t h e eight p a t i e n t s h a d occlusions of at least one vein graft or of a p r o x i m a l c o r o n a r y a r t e r y s e g m e n t a t the late p o s t o p e r a t i v e study. T h e s e six p a t i e n t s h a d a decrease f r o m a p r e o p e r a t i v e E F of 0.58 ___ 0.09 to 0.45 • 0.80 (p < 0.05, paired t
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9 Post-opOcclusionof Graft or ProximalArterySegment :~1 NpeeWPost-opOcclusions t ~ e
1.8
1.5
~-~
1.1
I ~'-~.
**
0.7
0.3
L
I
0.8
0.6
P. 0.4
0.2
0
I
I
PRE-OP
LATE FOLLOW- UP
Fig. 1. Left ventricular function preoperatively and at late follow-up. Connecting lines indicate pre- and postoperative values for each patient. The mean values _+ S.E.M. are indicated for each group. Statistical significance between the pre- and postoperative studies is indicated by * for p < 0.01, ** for p < 0.02, and *** for p < 0.05 (paired Student's t test).
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Apstein et al.
0.8
postoperative studies, seven patients had one or more occluded grafts; in contrast to the early postoperative studies, these seven cases demonstrated a significant reduction in EF (Fig. 2). Thus, the detrimental effect of graft occlusion may not become manifest immediately, but becomes apparent later in the postoperative course.
0.6
Discussion
oEarly Follow-up 9 Late Foll0w-up
0.4 _
~
0.2
I PRE-OP
I POST-OP
Fig. 2. Effect of graft occlusion on ejection fraction a t early a n d late follow-up studies. All p a t i e n t s who suffered postoperative graft occlusion are shown. T h e m e a n v a l u e s _+ S.E.M. are indicated for each group. Statistical significance is indicated by * for p < 0.05 (paired S t u d e n t ' s t test).
Table IV. Sequential studies of ventricular function in eight patients
EF Vcr
Preoperative
Early postoperative
Late postoperative
0.61 _+ 0.07 1.27 -+ 0.13
0.61 _+ 0.07 1.32 _+ 0.16
0.52 _+ 0.07* 1.11 _+ 0.18"*
*p < 0.05; **p = 0.1 --0.2 (paired Student's t test).
test), at late follow-up. There was no significant change in heart rate, LVEDP, or peak systolic pressure between the preoperative and late postoperative studies in these patients, so t h a t the decrease in EF probably represents a true decline in ventricular function. Comparison of the effect of graft occlusion at early and late follow-up. I n the early postoperative studies, five patients had one or more occluded bypass grafts; there was no significant difference between the pre- and early postoperative EF in this group of patients. In the late
552
The results of this study indicate (1) a correlation between a diminished preoperative left ventricular ejection fraction and an increased risk of postoperative graft occlusion, and (2) a failure of coronary artery-saphenous vein bypass surgery to effect a long-term improvement in postoperative left ventricular function, despite improved function in the early postoperative period in a selected subgroup. Graft patency. Our data indicate that patients with impaired preoperative ventricular function, as reflected by an ejection fraction of less than 0.60, had a significantly greater risk of postoperative graft occlusion {Table III). This observation has not been previously reported. The site of the vein graft {right coronary, left anterior descending, or circumflex} did not significantly influence the risk of graft occlusion, a finding in accord with others. 1~ The mechanism by which impaired left ventricular function led to a higher risk of graft occlusion was not studied, but it is likely t h a t patients with abnormal preoperative ejection fractions had more severe distal coronary artery disease which could have directly reduced graft flow in the anastomosed vessel. Left ventricular performance. Left ventricular ejection fraction and mean rate of circumferential shortening were not significantly changed from their preoperative values at the time of early postoperative study in the total group of patients studied. However, a small but significant improvement in the ejection fraction, and a similar trend in the mean rate of circumferential shortening, was noted in a selected subgroup of patients who had demonstrated a moderate reduction in preoperative left ventricular function {Table II). Late follow-up studies showed a significant decline in both left ventricular ejection fraction and the mean rate of circumferential shortening compared to values obtained preoperatively in the total group studied. At late followup, only a minority of patients who had remained
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Coronary artery surgery
free of occlusion and who demonstrated bidirectional flow in the grafted coronary artery were without a decrease in ventricular performance (Fig. 1). E a r l y follow-up. In the early follow-up period, the postoperative ejection fraction was not closely correlated with graft patency. Three patients who had suffered graft occlusion also had an improved ejection fraction. The six graft occlusions which occurred in the early follow-up period took place in t h a t subgroup of patients who demonstrated improved postoperative left ventricular performance; i.e., the subgroup with an abnormal preoperative ejection fraction. The five patients with one or more graft occlusions at early follow-up did not demonstrate a significant decrease in ejection fraction (Fig. 2). In addition to the direct effects of the coronary artery surgery, a number of nonsurgical factors may have affected early postoperative ventricular performance. Two of the seven patients with abnormal preoperative ventricular function had been digitalized between the pre- and postoperative studies; the postoperative hospital environment with its restriction in physical activity and regulated medical management of drugs and diet may have been a factor in the early postoperative improvement in ventricular function in the group as a whole. The "stress" of surgery has been shown to increase catecholamine excretion and may be an important determinant of ventricular function in the early postoperative period. 7, 10The higher mean heart rate in our early postoperative studies is consistent with this hypothesis. Furthermore, the increased heart rate and decreased afterload observed in the early postoperative period would tend to increase the ejection fraction, and therefore the observed increase in EF cannot be attributed entirely to a primary improvement in ventricular function. Since left ventricular end-diastolic pressure decreased in the early postoperative studies of those patients showing an improvement in ejection fraction, as it did in the group as a whole, the early improvement in ejection fraction cannot be attributed to increased preload. Rather, the early postoperative decrease in end-diastolic pressure probably resulted from the decreased left ventricular afterload and higher heart rate. Thus, nonsurgical factors may increase early postoperative ventricular function and temporarily mask any deterioration secondary to graft occlusion.
American 'Heart Journal
Mitral regurgitation did not occur de novo or increase in severity in any postoperative study; therefore, postoperative ejection fraction was not increased on this basis. L a t e follow-up. In contrast to the early followup studies, the presence and pattern of coronary flow in the vein graft and grafted artery was an important determinant of late postoperative ventricular function (Fig. 1 ). The 10 patients who suffered occlusions of one or more venous grafts, or failed to fill the proximal segment of the native grafted coronary artery, had a significant decrease in ventricular function, while the four patients who had 100 per cent graft and proximal artery segment patency maintained normal ventricular function. Proximal coronary artery occlusion could have important functional consequences if the involved proximal segment supplied a significant number of secondary arterial branches to the left ventricle. In such a case occlusion of this segment could lead to a significant loss in regional myocardial perfusion despite graft patency and good flow in the distal coronary artery segment. T M 16A decline in ventricular performance at late follow-up could not be attributed to any drugs with a negative inotropic effect taken de novo by any of the patients in the late postoperative period. The potential for myocardial revascularization to improve ventricular function would appear to be limited on theoretical grounds. It would seem apparent t h a t the mere presence of a new supply of oxygen could not convert scar tissue into functioning sarcomeres; however, depression of muscle function due to oxygen lack could theoretically be reversed if the ischemia were corrected before myocardial necrosis occurred. A significant early postoperative improvement in left ventricular contractility has been reported in the immediate postoperative period in a selected group of patients with a recent acute increase in the severity of their anginal syndrome 3, 4; these patients presumably had ischemically depressed tissue which had not yet become irreversibly damaged. In contrast, most studies of patients with stable coronary artery disease, without a recent increase in anginal symptomatology, have not shown a consistent improvement of abnormal ventricular function2 -1~ In the early postoperative period the ejection fraction has been reported to increase 13. i4 as we have reported for a selected subgroup in this
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p a p e r . H o w e v e r l o n g e r t e r m f o l l o w - u p s t u d i e s 1~ have shown no significant improvement of v e n t r i c u l a r f u n c t i o n in p a t i e n t s w i t h a l l g r a f t s patent, and deterioration of ventricular function w i t h g r a f t o c c l u s i o n , r e s u l t s w h i c h a r e in a g r e e ment with our data. T h e l o n g - t e r m effect o f b y p a s s g r a f t s u r g e r y u p o n left v e n t r i c u l a r e j e c t i o n f r a c t i o n in p a t i e n t s with chronic stable angina and left ventricular d y s f u n c t i o n is n o t e n c o u r a g i n g . A t l a t e f o l l o w - u p in o u r series, a l l f o u r p a t i e n t s w i t h a n a b n o r m a l p r e o p e r a t i v e left v e n t r i c u l a r e j e c t i o n f r a c t i o n h a d suffered graft occlusion and this group had a f u r t h e r d e c l i n e in v e n t r i c u l a r f u n c t i o n . O f t h e patients with normal preoperative left ventricular f u n c t i o n , g r a f t or p r o x i m a l c o r o n a r y a r t e r y o c c l u s i o n s occur.red i n t h e m a j o r i t y (six o f 11 p a t i e n t s ) , and ventricular function became abnormal posto p e r a t i v e l y . N o p a t i e n t in t h e 9 m o n t h f o l l o w - u p p e r i o d h a d a s i g n i f i c a n t i m p r o v e m e n t in a n abnormal preoperative ejection fraction. Thus, c o r o n a r y b y p a s s s h o u l d n o t b e p e r f o r m e d in a n a t t e m p t t o i m p r o v e v e n t r i c u l a r f u n c t i o n in t h e p a t i e n t w h o h a s a s t a b l e c h r o n i c level o f a n g i n a l symptomatology.
Summary Left ventricular performance and graft patency w e r e s t u d i e d p o s t o p e r a t i v e l y a t 2 w e e k s in 19 p a t i e n t s , a n d a t 9 m o n t h s in 15 p a t i e n t s . A t e a r l y follow-up, left ventricular ejection fraction and mean rate of circumferential shortening were u n c h a n g e d f o r t h e g r o u p as a w h o l e , b u t w e r e s l i g h t l y i m p r o v e d in p a t i e n t s w h o h a d h a d a moderately abnormal preoperative ejection fract i o n of 0.30 t o 0.60. A t l a t e f o l l o w - u p , 10 o f 14 patients had occluded at least one graft or the p r o x i m a l s e g m e n t of t h e g r a f t e d c o r o n a r y a r t e r y a n d h a d a n a s s o c i a t e d d e c r e a s e in v e n t r i c u l a r f u n c t i o n . T h e r i s k of g r a f t o c c l u s i o n w a s g r e a t e r if the preoperative ejection fraction was decreased; s e v e n of 10 p a t i e n t s w i t h a p r e o p e r a t i v e E F of less t h a n 0.60 s u f f e r e d o n e o r m o r e g r a f t o c c l u s i o n s , b u t o n l y t h r e e o f 16 p a t i e n t s w i t h a p r e o p e r a t i v e E F g r e a t e r t h a n 0.60 h a d a p o s t o p e r a t i v e g r a f t o c c l u s i o n (p < 0.05). T h e r e s u l t s s u g g e s t t h a t b y p a s s g r a f t s u r g e r y is n o t g e n e r a l l y i n d i c a t e d as a m e a s u r e t o i m p r o v e v e n t r i c u l a r f u n c t i o n in p a t i e n t s w i t h i s c h e m i c h e a r t disease.
REFERENCES 1. Manley, H., and Johnson, D.: Effects of surgery on angina (pre- and post-infarction) and myocardial function (failure), Circulation 46:1208, 1972. 554
2. Editorial: Coronary bypass surgery, Lancet 1:137, 1973. 3. Sustaita, H., Chatterjee, K., Matloff, J. M., Marty, A. T , Swan, H. J. C., and Fields, J.: Emergency bypass surgery in impending and complicated acute myocardial infarction, Arch. Surg. 105:30, 1972. 4. Chatterjee, K., Swan, H. J. C., Parmley, W. W., St~staita, H., Marcus, H., and Matloff, J.: Depression of left ventricular function due to. acute myocardial ischemia and its reversal after aortocoronary saphenous-vein bypass, N. Engl. J. Med. 286:1117, 1972. 5. Spencer, F. C., Green G. E., Tice, D. A., Wallsh, E., Mills, N. L., and Glassman, E.: Coronary artery bypass grafts for congestive heart failure: A report of experiences with 40 patients, J. Thorac. Cardiovasc. Surg. 62:529, 1971. 6. Kouchoukos, N., Doty, D. B., Buettner, L. E., and Kirklin, J. W.: Treatment of post-infarction cardiac failure by myocardial excision and revascularization, Circulation 45(Suppl. I):72, 1972. 7. Hammermeister, K. E., Kennedy, J. W., Hamilton, G. W., Steward, D. K:, Gould, K. L., Lipsomb, K., and Murray, J. A.: The effect of vein bypass grafting on resting left ventricular function, N. Engl. J. Med. 290:186, 1974. 8. Shepherd, R. L., Itscoitz, S. B., Glancy, D. L., Stinson, E. B., Reis, R. L., Olinger, G. N., Clark, C. E., and Epstein, S. E.: Deterioration of myocardial function following aorto-cor0nary bypass operation, Circulation 49:467, 1974. 9. Gott, V. L.: Outlook for patients after coronary artery revascularization, Am. J. Cardiol. 33:431, 1974. 10. Bourassa, M.: Left ventricular performance following direct myocardial revascularization (Editorial), Circulation 48:915, 1973. 11. Deal, P., Elliott, L. P., Bartley, T. D., Wheat, M. W., Jr., and Ramsey, H. W.: Quantitative left ventriculography in the immediate postoperative period after aorto-coronary bypass, J. Thorac. Cardiovasc. Surg. 66:1, 1973. 12. Arbogast, R., Solignac, A., and Bourassa, M.: Influence of aortocoronary saphenous vein bypass surgery on left ventricular volumes and ejection fraction. Comparison before and one year after surgery in 51 patients, Am. J. Med. 54:290, 1973. 13. Chatterjee, K., Swan, H. J. C., Parmley, W. W, Sustaita, H., Marcus, H. S., and Matloff, J.: Influence of direct myocardial revascularization on left ventricular asynergy and function in patients with coronary heart disease with and without previous myocardial infarction, Circulation 47:276, 1973. 14. Bolooki, H., Mallon, S., Ghahramani, A., Sommer, L., Vargas, A., Salvin, D., and Kaiser, G. A.: Objective assessment of the effects of aorto-coronary bypass operation on cardiac function, J. Thorac. Cardiovasc. Surg. 66:916, 1973. 15. Levine, J. A., Bechtel, D. J., Gorlin, R., Cohn, P. F., Herman, M. V, Cohn, L. H., and Collins, J. J., Jr.: Coronary artery anatomy before and after direct revascularization surgery: Clinical and cinearteriographic studies in 67 selected patients, AM. HEART J. 89:561, 1975. 16. Griffith, L. S. C., Achuff, S., Conti, R., Humphries, J. O., Brawley, R. K., Gott, V. L., and Ross, R. S.: Changes in intrinsic coronary circulation and segmental ventricular motion after saphenous-vein coronary bypass graft surgery, N. Engl. J. Med. 288:589, 1973. 17. Aldridge, H. E., and Trimble, A. S.: Progression of proximal coronary artery lesions to total occlusion after aorta-coronary saphenous vein bypass grafting, J. Thorac. Cardiovasc. Surg. 62:7, 1971. 18. Vlodaver, A., and Edwards, J. E.: Pathologic changes in aortic-coronary arterial saphenous vein grafts, Circulation 44:719, 1971.
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19. Kern, W. H., Dermer, G. B., and Lindesmith, G. G.: The intimal proliferation in aortic-coronary saphenous vein grafts, AM. HEART J. 84:771, 1972. 20. Walker, S. A., Friedberg, H. D., Flemma, R. J., and Johnson, W. D.: Determinants of angiographic patency of aortocoronary vein bypass grafts, Circulation 45(Suppl. I):86, 1972. 21. Friesinger, G. C., Schaffer, J., Griley, J. M., Gaertner, R. A., and Ross, R. S.: Hemodynamic consequences of the injection of radiopaque material, Circulation 31:730, 1965. 22. Rahimtoola, M. B., Duffy, J. P., and Swan, H. J. C.: Ventricular performance after angiocardiography, Circulation 35:70, 1967. 23. Cohn, P. F., Horn, H. R., Teichholz, L. E., Kreulen, T. H., Herman, M. V., and Gorlin, R.: Effects of angiographic contrast medium on left ventricular function in coronary artery disease. Comparison with static and dynamic exercise, Am. J. Cardiol. 32:31, 1973. 24. Cohn, P. F., Levine, J. A., Bergeron, G. A., and Gorlin, R.: Reproducibility of the angiographic left ventricular ejection fraction in patients with coronary artery disease, AM. HEART J. 88:713, 1974. 25. Sandler, H., and Dodge, H. T.: The use of single plane angiocardiograms for the calculation of left ventricular volume in man, AM. HEART J. 75:325, 1968.
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26. Kennedy, J. W., Treeholm e, S. E., and Kasser, I. S.: Left ventricular volume and mass from single plane cine angiocardiogram. A comparison of antero-posterior and right anterior oblique methods, AM. HEART J. 80:343, 1970. 27. Chatterjee, K., Sacoor, H., Sutton, G. C., and Miller, G. A. H.: Assessment of left ventricular function by single plane cine angiographic volume analysis, Br. Heart J. 33:565, 1971. 28. Karliner, J. S., Gault, J. H., Eckberg, D., Mullins, C. B., and Ross, J., Jr.: Mean velocity of fiber shortening: A simplified measure of left ventricular myocardial contractility, Circulation 44:323, 1971. 29. Bailey, N. T. J.: Statistical methods in biology, New York, 1959, John Wiley & Sons, Inc., pp. 61-64. 30. Rees, C., Bristow, J. D., Kremkau, E. L., Green, G. S., Herr, R. H., Griswold, H. E., and Starr, A.: Influence of aortocoronary bypass surgery on left ventricular performance, N. Engl. J. Med. 284:1116, 1971. 31. Bolooki, H., Rubinson, R. M., Michie, D. D., and Jude, J. R.: Assessment of myocardial contractility after coronary bypass grafts, J. Thorac. Cardiovasc. Surg. 62:543, 1971.
555
Coronary artery-saphenous vein bypass graft surgery is currently being advocated as a form of treatment for coronary artery disease, but the long-term effects of this operation on ventricular function have not been clearly established. 1, 2 Early postoperative improvement has been reported in selected patients with acute myocardial ischemia2 ~4 Improved function in the early postoperative period implies the preoperative presence of ischemic and depressed, but viable, myocardial tissue. Patients with impaired left ventricular performance due to chronic, stable coronary artery disease have not generally demonstrated a sustained improvement in postoperative ventricular function, 5~1~although early postoperative ventricular function improvement in this group of patients has also been reported.~3. ~4 The patency of the bypass coronary grafts and of the native coronary circulation is an important determinant of postoperative myocardial function. 1~16 Rapid progression from partial to complete occlusion in the proximal segments of grafted coronary arteries and progressive intimal fibrous proliferation of the vein grafts have been reported. 17-1s Postoperative graft patency is related to the rate of flow through the graft at the time of surgery, ~~but this measurement can only be made after surgery is performed. From the Departments of Medicine and Radiology, The New York Hospital-Cornell Medical Center, New York, N. Y. Received for publication Nov. 24, 1975. Reprint requests: Carl S. Apstein, M.D., Boston University School of Medicine, 80 E. Concord St., Boston, Mass. 02118.
May, 1977, Vol. 93, No. 5, pp. 547-555
Preoperative measurements which predicted the risk of postoperative graft occlusion and ventricular performance would be useful in evaluating patients for surgery. In order to evaluate long-term postoperative left ventricular performance and graft patency, and to develop predictive guidelines in these two areas, we have reviewed the pre- and postoperative angiographic studies in 26 patients who underwent coronary artery bypass graft surgery. Methods Patient material. The angiograms of 118 patients who underwent coronary artery-saphenous vein bypass graft surgery at the New York Hospital-Cornell Medical Center during a consecutive 24 month period were reviewed. The criteria for inclusion in this s t u d y consisted of technically adequate pre- and postoperative left ventriculograms, preoperative coronary arteriograms, and postoperative venograms of the bypass grafts. Patients were excluded if an aneurysectomy was done at the time of coronary artery surgery. Twenty-six patients (22 per cent) met these criteria, and form the basis of this report. Eighteen patients had a single postoperative study; eight patients underwent both early and late follow-up angiography. Thus a total of 34 postoperative studies were performed in 26 patients. Twenty-five patients were male; the average age was 51 years. The indication for surgery in each case was the presence of angina pectoris which was disabling enough to warrant surgery in the judgment of the
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547
A p s t e i n et al.
Table I. Preoperative values: Late vs. no late follow-up study
Ejection fraction M e a n r a t e of circumferential shortening A t h e r o s c l e r o t i c score
Late study (n = 15)
No late study (n = 12)
P*
0.62 - 0.05 1.29 _ 0.11
0.58 _ 0.04 1.39 _+ 0.14
N.S. N.S.
6.5
5.7
N.S.
_+ 1.8
_+ 0.8
*Unpaired Student's t test.
patient and his physicians. All patients had a "stable" clinical level of angina; there were no cases of "crescendo" or "unstable angina," or the "intermediate coronary syndrome." Fifty-one grafts, or an average of two per patient, were implanted and subsequently studied. Angiographic studies. The angiographic studies evaluated the extent of preoperative coronary artery atherosclerosis, pre- and postoperative left ventricular function, and postoperative graft patency. Three patients also had postoperative coronary arteriography. Left ventricular catheterization was performed from the right femoral artery. Pressure measurements were recorded prior to the injection of contrast material. Preoperative coronary arteriography was performed with the Judkins technique. Selective saphenous vein graft angiograms were performed and examined for graft occlusion at the time of each postoperative study. If the grafts were patent, the flow pattern in the anastomosed coronary artery was characterized as unidirectional if contrast material flowed only antegrade into the artery, or bidirectional if there was also retrograde flow into the proximal segment of the grafted artery. Lack of bidirectional flow in the grafted artery was interpreted as indicating t h a t an occlusion in the proximal segment of the artery had occurred. In one case of unidirectional antegrade flow in the grafted artery, coronary arteriography demonstrated occlusion of the proximal arterial segment. Coronary arteriography was not performed in the other instances where the proximal arterial segment failed to fill from the injection into the graft. However, lack of retrograde flow in the proximal segment of the grafted artery during injection into the venous graft has generally correlated with occlusion in the proximal segment of the native coronary artery, 16 although the precise location of the site
548
of occlusion cannot be delineated solely by graft angiography. After coronary arteriography, the patients were allowed to recover for approximately 30 minutes while the coronary films were developed and reviewed, after which time a left ventriculogram was performed and the ejection fraction was determined. In those patients where the left ventricular end-diastolic pressure (LVEDP) increased after coronary arteriography the ventriculogram was delayed until the LVEDP returned to the pre-coronary arteriogram value. The L V E D P usually returned to the control value within 30 minutes. This protocol should have minimized any influence upon our ventriculographic data of the effect of the contrast material injected during coronary artery or vein graft angiography. 21-23 The reproducibility of the ejection fraction (EF) measurement has been assessed by comparing angiograms performed 90 minutes before and 30 minutes after coronary angiography24; there was no significant difference between the two EF measurements. Thus our assessment of ventricular function via ventriculography performed 30 minutes after coronary arteriography should be free from the effects of the arteriography. The preoperative, early, and late follow-up studies were all performed with the same protocol. Analysis of ventricular function was performed by calculating the EF 2~-27 and the mean rate of circumferential shortening (~r ~ on normal sinus beats occurring at least two beats after premature beats. The EF obtained from the right anterior oblique ventriculograms were converted to biplane valuesJ ~ The EF was derived from the formula: EF = (EDV - ESV)/EDV, where EDV and ESV represent the end-diastolic and endsystolic volumes, respectively. The Vc~, in circumferences per second, was derived from the formula2~: Vc~ = (EDC - E S C ) / E D C / E T , where EDC and ESC represent the end-diastolic and endsystolic circumferences, respectively and ET represents the ejection time in seconds. The EF and CCcr were determined in duplicate and independently by two of the authors (C. S. A. and S. A. K.) for each patient; the values determined in this manner were in close agreement and the average is reported herein. T h u s observer-toobserver error 24 was minimized. The extent of coronary artery disease was
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Coronary artery surgery T a b l e II. Left ventricular function at early follow-up
EF
(cir./ sec.)
L VEDP (mm. Hg)
Heart rate (beats / min.)
L V systolic press. (ram. Hg)
1.32 • 0.11 1.43 • 0.12
20 • 2 14 • 1'
77 • 3 94 • 4*
138• 4 121 • 4*
78 • 3 93 _+ 8
132 • 7 119 • 4
AU patients (n = 19): Preoperative Postoperative
0.50 • 0.04 0.54 • 0.04
Patients with moderately abnormal preoperative L V function (EF: 0 . 3 0 - 0.60, n = 7): Preoperative Postoperative
0.38 • 0.04 0.47 • 0.06**
1.05 _ 0.15 1.22 • 0.14
20 • 3 16 • '2
*p < 0.01; **p < 0.05.
measured by an atherosclerotic score obtained by adding the values ascribed to each stenotic lesion in a major coronary artery. Scoring of lesions was done as follows: total occlusion = 4, 75 to 99 per cent stenosis - 3, 50 to 75 per cent stenosis = 2, less th an 50 per cent stenosis = 1, no lesions = 0. After surgery, all patients were advised to u n d er g o follow-up catheterization, regardless of their symptomatology. T he decision to have such a study rested with the patient and his own physicians. Early postoperative studies, prior to discharge from the hospital, were obtained in 19 patients with 38 grafts at an average postoperative interval of 14 days and ranging up to 4 months. Fifteen patients had a late follow-up study between 4 months and 1 year after surgery (mean = 9 months). T he patients who underwent a follow-up study are thus "selected" in the sense that they represent the survivors of the operation who consented to restudy. At the time these data were collected, 27 patients with adequate preoperative studies were long-term survivors ( > 4 months after operation). In order to ascertain whether the late restudy group was an unbiased sample of this late postoperative survivor population, preoperative measurements were compared for the 15 patients who were restudied at late follow-up and those 12 who were long-term survivors and thus candidates for restudy, but who did not consent. These groups are compared in Table I. In terms of preoperative left ventricular function and severity of coronary artery disease, the patients who returned for late follow-up study were a representative sample of all the patients operated upon who survived for at least 4 months. Statistical analysis of the data reported herein was performed with the paired or unpaired
American Heart Journal
Student's t test, as appropriate, for hemodynamic data. To analyze the significance of the different risks of graft occlusion, the value of p was calculated from a 2 by 2 contingency table with the Fisher exact probability test. ~' D at a are reported as the mean _+ standard error of the mean (S.E.M.). Results Extent of atherosclerosis. All patients in this series had significant coronary artery disease demonstrated by coronary angiography. The mean atherosclertic score for the 26 patients was 6.0. Ejection fraction was inversely related to the atherosclerotic index; the 16 patients with an ejection fraction less than 0.50 had an atherosclerotic score of 7.0 _+ 0.5; the 10 patients with an ejection fraction greater than 0.50 had an atherosclerotic score of 5.4 _+ 0.6 (p < 0.05, unpaired t test). Early postoperative studies. Ventricular function. Left ventricular function, as assessed by ejection fraction and mean rate of circumferential shortening, was unchanged at the time of the 14 day follow-up study in the group of 19 patients considered as a whole (Table II). However the postoperative L V E D P significantly decreased, heart rate increased, and peak left ventricular systolic pressure decreased. Since left ventricular peak systolic pressure was significantly lower, and heart rate was significantly higher at this time, the observed decline in L V E D P may not represent a primary improvement of myocardial function. T he group of 19 patients was separated on the basis of preoperative ejection fraction. The subgroup of seven patients with a moderately impaired preoperative ejection fraction {0.30 to 0.60) had an increase in ejection fraction at early
549
A p s t e i n e t al.
Table III. Postoperative graft patency
No. of patients
No. of grafts
Studied
All grafts patent
One or more graft occlusions
9 10 19
9 5 14
0'* 5** 5
16 22 38
16 16 32
0 (0%) _66 (27%) 6 (16%)
11 4 15
8 0 8
3** 4"* 7
21 ..10 31
17 5 22
4 (19%,) __5(50%) 9 (29%)
16 10 26
13 3 16
3** 7** 10
29 22 51
25 14 39
4 (14%) 8 (37%) 12 (24%)
ImplantedlPatent I Occluded(%)
Early follow-up (<4 moO: Preoperative E F > 0.60 Preoperative E F < 0.60 Total
Late follow-up (>4 me.): Preoperative E F > 0.60 Preoperative E F < 0.60 Total
Combined early and late follow-up*: Preoperative E F > 0.60 Preoperative E F < 0.60 Total
*Each patient counted singly with data based on latest study. **P < 0.05 for risk of graft occlusion, Fisher exact test, two-tailed. 2~
follow-up, and a trend toward an increased ~?(:~.~ which was not statistically significant. The increase in ejection fraction at a lower enddiastolic pressure may indicate a slight improvement in ventricular function in these patients, but could also be due to the lower postoperative afterl0ad (LV systolic pressure) and higher heart rate. Two of the seven patients with an improved ejection fraction postoperatively had been digitalized between the pre- and postoperative studies. Thus, the finding of early postoperative improvement in the ejection fraction must be interpreted cautiously. The subgroup of nine patients who had a normal preoperative ejection fraction (greater than 0.60) had no significant change in ejection fraction at early follow-up. Three patients had a preoperative ejection fraction less than 0.20; there was no significant change at early followup. Graft patency. Thirty-eight grafts in 19 patients were studied at early follow-up (Table III). Sixteen per cent (6 of 38) of the grafts were occluded. Eighty-four per cent (32 of 38) of the grafts were patent and 30 of the Patent grafts had bidirectional flow of contrast material into the coronary artery distal to the site of anastomosis. In two cases the anastomosed coronary artery exhibited only antegrade flow of contrast material from the venous graft, indicating probable occlusion in the proximal segment of the grafted native coronary artery. Graft patency in the early postoperative period
550
was r e l a t e d t o the preoperative ejection fraction. The risk of graft occlusion at early follow-up was zero if the preoperative EF had been greater than 0.60, but there was a 27 per cent risk of occlusion for each implanted graft when the preoperative ejection fraction was less than 0.60. All patients with a preoperative EF greater than 0.60 remained free of any graft occlusion, while 50 per cent of those patients with a preoperative EF of less than 0.60 suffered at least one graft occlusion. Late post-operative studies. Thirty-one grafts were studied in 15 patients at an average postoperative interval of nine months {Table III) and ventricular function was studied in fourteen of the fifteen patients {Fig. 1). Graftpatency. Nine of the grafts were occluded (29 per cent). Twenty-two grafts (71 per cent) were patent and 19 showed bidirectional flow in the anastomotic coronary artery. Three were patent, but filled only the distal portion of the grafted coronary artery indicating probable occlusion in the proximal segment of the grafted coronary artery. As with the early postoperative studies, graft patency at 9 months follow-up was associated with a normal preoperative ejection fraction. The risk of graft occlusion, when the early and late follow-up studies are considered together, was much higher for those patients with abnormal preoperative ventricular function (Table III). Over all, 51 grafts were restudied in 26 patients. In the 16 patients with a preoperative
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Coronary artery surgery E F greater t h a n 0.60, four of 29 grafts (14 per cent) were occluded; i n the 10 p a t i e n t s w i t h a p r e o p e r a t i v e E F less t h a n 0.60 t h e risk of g r a f t occlusion was 37 per cent (eight of 22 grafts). G r a f t occlusions occurred in seven of 10 p a t i e n t s who h a d a p r e o p e r a t i v e E F less t h a n 0.60, b u t in only t h r e e of 16 p a t i e n t s who h a d a p r e o p e r a t i v e E F greater t h a n 0.60. V e n t r i c u l a r function. T h e E F a n d Vcr were significantly reduced f r o m the p r e o p e r a t i v e values in the late p o s t o p e r a t i v e period in the group of p a t i e n t s considered as a whole (Fig. 1). For the t o t a l group of !ate follow-up studies, the E F decreased f r o m 0.62 + 0.05 to 0.54 + 0.05 (p < 0.01, paired t test) a n d the V~,F decreased from 1.29 + 0.11 t o 1.11 • 0.12 circumferences per second (p < 0.02, paired t test). T h e left v e n t r i c u l a r systolic pressure decreased from 130 • 6 m m . H g p r e o p e r a t i v e to 114 • 5 m m . H g p o s t o p e r a t i v e (p < 0.01, paired t test). T h e r e was no significant change in h e a r t r a t e (79 • 3 preoperative vs. 78 _+ 2 m m . H g postoperative). T h e significant decrease in E F and VcF at c o n s t a n t h e a r t r a t e and end-diastolic pressure b u t with reduced a f t e r l o a d (peak LV systolic pressure) indicates a r e d u c t i o n of v e n t r i c u l a r function in the late p o s t o p e r a t i v e period. W h e n the p a t i e n t s were divided into s u b g r o u p s on the basis of graft p a t e n c y a n d flow p a t t e r n in the grafted c o r o n a r y a r t e r y (Fig. 1), it was f o u n d t h a t the s u b g r o u p w i t h o u t graft occlusions a n d with bidirectional flow into the grafted a r t e r y h a d m a i n t a i n e d left v e n t r i c u l a r p e r f o r m a n c e at their n o r m a l p r e o p e r a t i v e level. T h e subgroup with occluded grafts or unidirectional a n t e g r a d e flow in t h e grafted a r t e r y showed a significant decrease in left v e n t r i c u l a r E F f r o m 0.59 _+ 0.07 to 0.49 • 0.07 (p < 0.01, paired t test) and in Vc~ f r o m 1.21 • 0.14 to 1.01 • 0.15 circumferences per second (p < 0.05, paired t test). Sequential studies in the same patients. E i g h t p a t i e n t s h a d follow-up studies during b o t h the early and late p o s t o p e r a t i v e periods (Table IV). This small group showed a t r e n d which was similar to the entire s t u d y group: no change in v e n t r i c u l a r f u n c t i o n at early follow-up w i t h a decrease in the late follow-up period. Six of t h e eight p a t i e n t s h a d occlusions of at least one vein graft or of a p r o x i m a l c o r o n a r y a r t e r y s e g m e n t a t the late p o s t o p e r a t i v e study. T h e s e six p a t i e n t s h a d a decrease f r o m a p r e o p e r a t i v e E F of 0.58 ___ 0.09 to 0.45 • 0.80 (p < 0.05, paired t
American Heart Journal
-
9 Post-opOcclusionof Graft or ProximalArterySegment :~1 NpeeWPost-opOcclusions t ~ e
1.8
1.5
~-~
1.1
I ~'-~.
**
0.7
0.3
L
I
0.8
0.6
P. 0.4
0.2
0
I
I
PRE-OP
LATE FOLLOW- UP
Fig. 1. Left ventricular function preoperatively and at late follow-up. Connecting lines indicate pre- and postoperative values for each patient. The mean values _+ S.E.M. are indicated for each group. Statistical significance between the pre- and postoperative studies is indicated by * for p < 0.01, ** for p < 0.02, and *** for p < 0.05 (paired Student's t test).
551
Apstein et al.
0.8
postoperative studies, seven patients had one or more occluded grafts; in contrast to the early postoperative studies, these seven cases demonstrated a significant reduction in EF (Fig. 2). Thus, the detrimental effect of graft occlusion may not become manifest immediately, but becomes apparent later in the postoperative course.
0.6
Discussion
oEarly Follow-up 9 Late Foll0w-up
0.4 _
~
0.2
I PRE-OP
I POST-OP
Fig. 2. Effect of graft occlusion on ejection fraction a t early a n d late follow-up studies. All p a t i e n t s who suffered postoperative graft occlusion are shown. T h e m e a n v a l u e s _+ S.E.M. are indicated for each group. Statistical significance is indicated by * for p < 0.05 (paired S t u d e n t ' s t test).
Table IV. Sequential studies of ventricular function in eight patients
EF Vcr
Preoperative
Early postoperative
Late postoperative
0.61 _+ 0.07 1.27 -+ 0.13
0.61 _+ 0.07 1.32 _+ 0.16
0.52 _+ 0.07* 1.11 _+ 0.18"*
*p < 0.05; **p = 0.1 --0.2 (paired Student's t test).
test), at late follow-up. There was no significant change in heart rate, LVEDP, or peak systolic pressure between the preoperative and late postoperative studies in these patients, so t h a t the decrease in EF probably represents a true decline in ventricular function. Comparison of the effect of graft occlusion at early and late follow-up. I n the early postoperative studies, five patients had one or more occluded bypass grafts; there was no significant difference between the pre- and early postoperative EF in this group of patients. In the late
552
The results of this study indicate (1) a correlation between a diminished preoperative left ventricular ejection fraction and an increased risk of postoperative graft occlusion, and (2) a failure of coronary artery-saphenous vein bypass surgery to effect a long-term improvement in postoperative left ventricular function, despite improved function in the early postoperative period in a selected subgroup. Graft patency. Our data indicate that patients with impaired preoperative ventricular function, as reflected by an ejection fraction of less than 0.60, had a significantly greater risk of postoperative graft occlusion {Table III). This observation has not been previously reported. The site of the vein graft {right coronary, left anterior descending, or circumflex} did not significantly influence the risk of graft occlusion, a finding in accord with others. 1~ The mechanism by which impaired left ventricular function led to a higher risk of graft occlusion was not studied, but it is likely t h a t patients with abnormal preoperative ejection fractions had more severe distal coronary artery disease which could have directly reduced graft flow in the anastomosed vessel. Left ventricular performance. Left ventricular ejection fraction and mean rate of circumferential shortening were not significantly changed from their preoperative values at the time of early postoperative study in the total group of patients studied. However, a small but significant improvement in the ejection fraction, and a similar trend in the mean rate of circumferential shortening, was noted in a selected subgroup of patients who had demonstrated a moderate reduction in preoperative left ventricular function {Table II). Late follow-up studies showed a significant decline in both left ventricular ejection fraction and the mean rate of circumferential shortening compared to values obtained preoperatively in the total group studied. At late followup, only a minority of patients who had remained
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free of occlusion and who demonstrated bidirectional flow in the grafted coronary artery were without a decrease in ventricular performance (Fig. 1). E a r l y follow-up. In the early follow-up period, the postoperative ejection fraction was not closely correlated with graft patency. Three patients who had suffered graft occlusion also had an improved ejection fraction. The six graft occlusions which occurred in the early follow-up period took place in t h a t subgroup of patients who demonstrated improved postoperative left ventricular performance; i.e., the subgroup with an abnormal preoperative ejection fraction. The five patients with one or more graft occlusions at early follow-up did not demonstrate a significant decrease in ejection fraction (Fig. 2). In addition to the direct effects of the coronary artery surgery, a number of nonsurgical factors may have affected early postoperative ventricular performance. Two of the seven patients with abnormal preoperative ventricular function had been digitalized between the pre- and postoperative studies; the postoperative hospital environment with its restriction in physical activity and regulated medical management of drugs and diet may have been a factor in the early postoperative improvement in ventricular function in the group as a whole. The "stress" of surgery has been shown to increase catecholamine excretion and may be an important determinant of ventricular function in the early postoperative period. 7, 10The higher mean heart rate in our early postoperative studies is consistent with this hypothesis. Furthermore, the increased heart rate and decreased afterload observed in the early postoperative period would tend to increase the ejection fraction, and therefore the observed increase in EF cannot be attributed entirely to a primary improvement in ventricular function. Since left ventricular end-diastolic pressure decreased in the early postoperative studies of those patients showing an improvement in ejection fraction, as it did in the group as a whole, the early improvement in ejection fraction cannot be attributed to increased preload. Rather, the early postoperative decrease in end-diastolic pressure probably resulted from the decreased left ventricular afterload and higher heart rate. Thus, nonsurgical factors may increase early postoperative ventricular function and temporarily mask any deterioration secondary to graft occlusion.
American 'Heart Journal
Mitral regurgitation did not occur de novo or increase in severity in any postoperative study; therefore, postoperative ejection fraction was not increased on this basis. L a t e follow-up. In contrast to the early followup studies, the presence and pattern of coronary flow in the vein graft and grafted artery was an important determinant of late postoperative ventricular function (Fig. 1 ). The 10 patients who suffered occlusions of one or more venous grafts, or failed to fill the proximal segment of the native grafted coronary artery, had a significant decrease in ventricular function, while the four patients who had 100 per cent graft and proximal artery segment patency maintained normal ventricular function. Proximal coronary artery occlusion could have important functional consequences if the involved proximal segment supplied a significant number of secondary arterial branches to the left ventricle. In such a case occlusion of this segment could lead to a significant loss in regional myocardial perfusion despite graft patency and good flow in the distal coronary artery segment. T M 16A decline in ventricular performance at late follow-up could not be attributed to any drugs with a negative inotropic effect taken de novo by any of the patients in the late postoperative period. The potential for myocardial revascularization to improve ventricular function would appear to be limited on theoretical grounds. It would seem apparent t h a t the mere presence of a new supply of oxygen could not convert scar tissue into functioning sarcomeres; however, depression of muscle function due to oxygen lack could theoretically be reversed if the ischemia were corrected before myocardial necrosis occurred. A significant early postoperative improvement in left ventricular contractility has been reported in the immediate postoperative period in a selected group of patients with a recent acute increase in the severity of their anginal syndrome 3, 4; these patients presumably had ischemically depressed tissue which had not yet become irreversibly damaged. In contrast, most studies of patients with stable coronary artery disease, without a recent increase in anginal symptomatology, have not shown a consistent improvement of abnormal ventricular function2 -1~ In the early postoperative period the ejection fraction has been reported to increase 13. i4 as we have reported for a selected subgroup in this
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p a p e r . H o w e v e r l o n g e r t e r m f o l l o w - u p s t u d i e s 1~ have shown no significant improvement of v e n t r i c u l a r f u n c t i o n in p a t i e n t s w i t h a l l g r a f t s patent, and deterioration of ventricular function w i t h g r a f t o c c l u s i o n , r e s u l t s w h i c h a r e in a g r e e ment with our data. T h e l o n g - t e r m effect o f b y p a s s g r a f t s u r g e r y u p o n left v e n t r i c u l a r e j e c t i o n f r a c t i o n in p a t i e n t s with chronic stable angina and left ventricular d y s f u n c t i o n is n o t e n c o u r a g i n g . A t l a t e f o l l o w - u p in o u r series, a l l f o u r p a t i e n t s w i t h a n a b n o r m a l p r e o p e r a t i v e left v e n t r i c u l a r e j e c t i o n f r a c t i o n h a d suffered graft occlusion and this group had a f u r t h e r d e c l i n e in v e n t r i c u l a r f u n c t i o n . O f t h e patients with normal preoperative left ventricular f u n c t i o n , g r a f t or p r o x i m a l c o r o n a r y a r t e r y o c c l u s i o n s occur.red i n t h e m a j o r i t y (six o f 11 p a t i e n t s ) , and ventricular function became abnormal posto p e r a t i v e l y . N o p a t i e n t in t h e 9 m o n t h f o l l o w - u p p e r i o d h a d a s i g n i f i c a n t i m p r o v e m e n t in a n abnormal preoperative ejection fraction. Thus, c o r o n a r y b y p a s s s h o u l d n o t b e p e r f o r m e d in a n a t t e m p t t o i m p r o v e v e n t r i c u l a r f u n c t i o n in t h e p a t i e n t w h o h a s a s t a b l e c h r o n i c level o f a n g i n a l symptomatology.
Summary Left ventricular performance and graft patency w e r e s t u d i e d p o s t o p e r a t i v e l y a t 2 w e e k s in 19 p a t i e n t s , a n d a t 9 m o n t h s in 15 p a t i e n t s . A t e a r l y follow-up, left ventricular ejection fraction and mean rate of circumferential shortening were u n c h a n g e d f o r t h e g r o u p as a w h o l e , b u t w e r e s l i g h t l y i m p r o v e d in p a t i e n t s w h o h a d h a d a moderately abnormal preoperative ejection fract i o n of 0.30 t o 0.60. A t l a t e f o l l o w - u p , 10 o f 14 patients had occluded at least one graft or the p r o x i m a l s e g m e n t of t h e g r a f t e d c o r o n a r y a r t e r y a n d h a d a n a s s o c i a t e d d e c r e a s e in v e n t r i c u l a r f u n c t i o n . T h e r i s k of g r a f t o c c l u s i o n w a s g r e a t e r if the preoperative ejection fraction was decreased; s e v e n of 10 p a t i e n t s w i t h a p r e o p e r a t i v e E F of less t h a n 0.60 s u f f e r e d o n e o r m o r e g r a f t o c c l u s i o n s , b u t o n l y t h r e e o f 16 p a t i e n t s w i t h a p r e o p e r a t i v e E F g r e a t e r t h a n 0.60 h a d a p o s t o p e r a t i v e g r a f t o c c l u s i o n (p < 0.05). T h e r e s u l t s s u g g e s t t h a t b y p a s s g r a f t s u r g e r y is n o t g e n e r a l l y i n d i c a t e d as a m e a s u r e t o i m p r o v e v e n t r i c u l a r f u n c t i o n in p a t i e n t s w i t h i s c h e m i c h e a r t disease.
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American Heart Journal
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