community medicine, University of Alberta, and Dr. Donald 0. Anderson, at that time professor, department of health care and epidemiology, University of British Columbia, and currently professor and director, division of health services, University of British Columbia. We gratefully acknowledge their support during the production of the "Report on Basic Canadian Data"; the conclusions reported in this paper, however, are those of the authors. This project was supported by national health grant 608-21-6 from Health and Welfare Canada.

References 1. World Health Organization/International Collaborative Study of Medical Care Utilization, manual 1, Organization and Development; manual 2, QuestIonnaires; manual 3, Health Services Systems and Demography; manual 4, Training and Supervisors' Manual; manual 5, Interviewers' Manual; manual 6, Coders' Manual; manual 7, Analysis Manual; manual 8, Tape Layout Manual; manual 9, Data Processing Manual, Baltimore, Coordinating Committee, 1970 2. RABIN DL (ed): International comparisons of medical care. Preliminary report of the World Health Organization/International Collaborative Study of Medical Care Utilization. Milbank Mem Fund Q 50 (3): part 2, 1972

4.

5.

6.

7.

3. MATrHEWS VL, Fa..mmt I, CRAWFORD 3: A

Response-Record Discrepancy Study, WHO/ ICS-MCU, Saskatchewan study area reports,

series 2, no 2, Saskatoon, Dept of social and preventive medicine, U of Saskatchewan, 1972 FEATHER J: A Study of Interviewer Variance, WHO/ICS-MCU, Saskatchewan study area reports, series 2, no 3, Saskatoon, Dept of social and preventive medicine, U of Saskatchewan, 1973 KOHN R, WHITE KL (eds): Health Care: An International Study. Main Report of the World Health Organization/International Collaborative Study of Medical Care Utilization, London, Oxford U Pr, 1975 JoslE GH (ed): World Health Organizationi International Collaborative Study of Medical Care Utilization. Report on Basic Canadian Data, Saskatoon, Dept of social and preventive medicine, U of Saskatchewan, 1973 BENNETr L: Smoking and Morbidity in a Saskatchewan Sample, WHO/ICS-MCU, Saskatchewan study area reports, series 1, no 1, Saskatoon, Dept of social and preventiv medicine, U of Saskatchewan, 1973

Five years' experience with aortocoronary bypass grafting WILBERT J. KEON, MD; PIERRE B.DARD, MD; YASAR AKYUREKLI, MD; MAURICE BRAIs, MD; FRANK BERKMAN, MD; KIM W. TAN, MD; BRIAN C. MORTON, MD

During a 5-year period (Apr. 14, 1970 to Apr. 14, 1975) 930 patients underwent aortocoronary bypass grafting; the procedure was done as an emergency in 141. Of the entire group 3.30/0 died at operation, 1.60/0 died in hospital and 5.80/o died later; of the patients undergoing emergency grafting 12.1O/o died at operation and 5.7/o died later. From a detailed analysis of the first 600 patients It was found that both operative and late mortality were clearly related to two factors: severe left ventricular dysfunction at the time of operation and inadequate surgical treatment because of insertion of insufficient numbers of grafts or because of poor blood flow through the grafts. Sur une periode de 5 ans (du 14 avril 1970 au 14 avril 1975) 930 patients subirent un pontage aortocoronarien; l'lntervention fut faite en urgence chez 141 d'entre eux. Du groupe 3.30/o moururent au cours de l'operation, 1.6/o moururent & l'h8pltal et 5.80/o moururent plus tard; des patients recevant Ia greffe en urgence l2.l*/o moururent au cours de l'op.ration et S.70/o moururent plus tard. Une analyse d6taill6e des 600 premiers patients r6vele que Ia mortalit. op6ratoire et Ia mortalit6 retard6e 6taient nettement reli.es a deux facteurs: une grave Insuffisance ventriculaire gauche au moment de l'op6ration et un traitement chirurgical From the University of Ottawa cardiac unit, Ottawa Civic Hospital Reprint requests to: Dr. WJ. Keon, University of Ottawa cardiac unit, Ottawa Civic Hospital, 1053 Carling Ave., Ottawa, ON K1Y 4E9

inad6quat do a I'insertion d'un nombre insuffisant de greffons, ou a cause d'un mauvais debit sanguin dans les greffons.

The technique of aortocoronary bypass grafting with a section of saphenous vein was developed by Favaloro in 19671 and was first used extensively by Johnson and colleagues.2 It is now the most common operation for ischemic heart disease and is performed more often than all other cardiac surgical procedures combined.3 Mortality rates differ widely - from as low as 0.8% for elective procedures4 to 12% .. We present the results of our experience with aortocoronary bypass grafting during the 5-year period Apr. 14, 1970 to Apr. 14, 1975. We will discuss in detail points that have received attention in recent cardiac surgery publications, such as the improvement in results due to increased experience, the efficacy of performing the operation in patients with triple vessel disease, the high mortality associated with poor left ventricular contractility and the circumstances under which we perform emergency grafting.

Patients and procedures In the first 5 years (April 1970 to April 1975) that aortocoronary bypass grafting was performed in our unit 930 patients underwent the operation; in 789 it was an elective procedure and in 141 an emergency procedure. The mortality data are presented in Table I. A detailed study was carried out on the first 600 patients, who underwent operations between April 1970 and March 1974; the mortality data are presented in Table II. One previous myocardial infarction had been documented in 278 patients, two infarctions in 74 and three in 12. Fifty-four of the patients were women. The mean age was 48 years (range, 25 to 74 years). Half of the 600 patients underwent other procedures at the same time as aortocoronary bypass grafting (Table III). Mammary artery implantation was a common associated procedure in the first 2 years; the operative mortality for this combination of procedures was lower than that for aortocoronary bypass grafting alone because the combination was not done as an emergency operation. For the combination of ventricular aneurysmectomy and aorto-

Table I-Mortality data for 930 patients who underwent aortocoronary bypass grafting between April 1970 and April 1975 Status of grafting procedure Elective

n 789

Operative 14 (1.8)

Emergency

141

17(12.1)

930Total

31 (3.3)

n = no. of patients. 312 CMA JOURNAL/FEBRUARY 21, 1976/VOL 114

No. (and %) of deaths Hospital Late 15(1.9) 46 (5.8) 0 15 (1.6)

Total 75 (9.5)

8 (5.7)

25(11.7)

54 (5.8)

100 (10.8)

bypass grafting the late mor¬ tality was much higher than that for grafting alone because patients under¬ going the combination of procedures had poor ventricular function. Both operative and late mortality were high for the combination of valve replace¬ ment and bypass grafting; similarly, at Cleveland Clinic an 8% operative mor¬ tality was found for this combination of procedures.6 We have also done some complicated combinations of pro¬ cedures that have resulted in high oper¬ ative and late mortality (Table III). coronary

The increase in the number of grafts inserted per patient has not increased operative mortality but has, in fact, decreased it. Of all 930 patients only 1 (0.6%) of the 171 who received four, five or six grafts died at operation, whereas 30 (4.0%) of the 759 who received fewer than four died at oper¬ ation. The late results are even more striking: 97 of all 100 patients who died had received fewer than four grafts. Our conclusion differs from that of Bennett and colleagues,7 who found that operative mortality was higher in their patients who received multiple

inadequate proximal

or

distal anasto¬

mosis, or some mechanical obstruction in the graft. In general, vein grafts that show good increases in flow in response to papaverine injection can be assumed to be of good technical quality, whereas grafts with little or no response are

poor, usually because the distal anas¬ tomosis was performed badly. We agree with Johnson,8 who wrote "There is a distinct correlation between mortality and incomplete revascularization". We now insert as many grafts as possible and achieve very good im¬ provement in myocardial blood flow in most patients. In our most recent 100 patients an average of 3.4 grafts were inserted per patient and the average myocardial blood flow was 175 ml/ min. We believe it is mandatory to insert several grafts to achieve maximal improvement in myocardial blood flow and to minimize the complications of occlusion of a single graft.

grafts. We studied blood flow through the In the early procedures we were con¬ graft before and after injection of papaservative about the number of grafts verine into the graft. Flow tended to inserted. Of 383 patients with triple increase greatly after injection of papavessel disease 52 had only one vessel verine into the graft in the right coro¬ grafted, 111 had two vessels grafted nary, left anterior descending and cirand 220 had all three vessels grafted; cumflex systems, but in the smaller we now believe that 163 of these pa¬ vessels the changes in flow were small tients did not have adequate surgery. (Table IV). We believe it is important Of the 167 patients with double vessel to assess the response of a graft to Benefits of experience disease 52 had only one vessel grafted. papaverine injection because this shows We learned, as did others,7,9-12 that The other 50 of the first 600 patients whether the run-off to the vessel is re¬ had single vessel disease. Now we rare¬ stricted by the peripheral vascular bed an increase in the experience of the ly do not graft all the diseased vessels. of the system, a rigid grafted vessel, surgical team brought about a decrease in mortality and an improvement in the technical aspects of the operation. A Table II.Mortality data for 600 patients who underwent aortocoronary bypass comparison of patients 1 to 100 with grafting between April 1970 and March 1974 patients 501 to 600 for several factors showed this clearly (Table V). In the later group there were fewer operative deaths, more grafts inserted per patient on the average and a much larger aver¬ age increase in myocardial blood flow. The average blood flow through a graft was less when several grafts had been inserted into a given vessel system. n no. of patients. However, the blood flow requirements of a given area of myocardium fre¬ quently cannot be met by a single graft Table lll.Mortality data in relation to operative procedure or combination of into a vessel such as a diseased left procedures in the 600 patients anterior descending branch. Because of Grafted vessels: number and blood flow

=

Operative procedure Aortocoronary bypass grafting & mammary artery implantation & ventricular aneurysmectomy & valve replacement or valvotomy & mammary artery implantation & ventricular aneurysmectomy

n

300 215 42 19

No. (and %) of deaths Late Total Operative 13 (4.3) 18 (6.0) 31 (10.3) 4 (1.9) 11 (5.1) 15 (7.0) 2 (4.8) 8 (19.0) 10 (23.8) 2 (10.5) 5 (26.3) 7 (36.8)

18 6

Other*

0 3

(50.0)

1 2

(5.6) (33.3)

1 5

(5-6) (83.3)

no. of patients ?Aortocoronary bypass grafting (ABG), valve procedure & aneurysmectomy (1); ABG & coronary thrombectomy (1); ABG, pulmonary valvotomy, aortic valve replacement & infundibulectomy (1); ABG & repair of ventricular septal defect (2); and ABG, mammary artery implantation & aneurysmectomy (1).

n

=

Right coronary artery Left anterior descending branch Circumflex branch Marginal branch Diagonal branch

334 366 219 8 19

85.7 76.9 60.8 58.1 41.4

78 100 48 5 19

127.2 94.9 99.9 50.6 66.0

Table V.Comparison of an earlier and a later group of patients Patients 1 Patients 501 Factor Deaths

Operative Late

No. of grafts Total

Average

tolOO

to 600

5 16

133 1.3

Blood flow through graft, average (ml/min) 106.7 Per patient 90.5 Per graft

Bypass time, average (min) 90.3 Per patient 66.8 Per graft Anoxic time, average (min) 36.2 Per patient Per graft 27.6

301 3 152.4 49.5 66.1 21.7

36.1 11.8

CMA JOURNAL/FEBRUARY 21, 1976/VOL 114 313

this and the risk of graft occlusion, two grafts that will permit a large flow (more than 50 ml/min) should be in¬ serted into a major vessel system if possible. Cardiopulmonary bypass time per graft and per patient in the later group was shortened greatly. The anoxic time per patient remained the same but the anoxic time per graft was shortened greatly in the later group, so we can now insert several grafts without undue anoxia of the myocardium. The symptomatic improvement in the earlier patients was encouraging (Table VI). Only one patient remained in class IV (angina at rest) and two in class III (angina with moderate exertion). Sixteen were in class II (angina with heavy exertion) 3 months after opera¬ tion and the remainder were then in class I (asymptomatic). Results were slightly better in the later group, but postoperatively 4 patients had class III angina and 11, class II angina.

Angiographic follow-up Angiographic follow-up

patent after 1 year. It appears that pa¬ patients who underwent elective

tients who have complete angiographic follow-up have a better late prognosis: the overall late mortality for all patients in our series with normal ventricular function was about 4%, whereas in this group who had complete angiographic follow-up none died, although six re¬

quired reoperation. The rate for intraoperative myocar¬ dial infarction, determined from elec¬ trocardiographic and enzyme data, was 6.6% in the group from the National Defence Medical Centre, whereas in the entire series the rate was 5% from electrocardiographic data alone and 12% from electrocardiographic and en¬ zyme data. We have begun a prospec¬ tive study of intraoperative myocardial infarction, with rigid criteria for inter¬ pretation of electrocardiographic and enzyme data, to elucidate this discrepancy. We have not yet performed a detailed analysis of pre- and postopera¬ tive ventricular function in the patients from the National Defence Medical Centre.

Triple vessel disease Patients with triple vessel disease were studied at a mean follow-up time of 27 months. According to the study by Oberman and colleagues13 the mor¬ tality of patients with triple vessel dis¬ is about 1 % per month when they Table VI.Symptomatic classification* of ease are treated only medically. The mortal¬ the two groups of patients ity of such patients in our series with good (normal, class I or class II) ventri¬ cular function was 3.5%, whereas 27% would have died if they had been treated only medically; therefore 23.5% had their life prolonged. Most of the late deaths in these patients could be attributed to poor left ventricular func¬ tion or to little increase in myocardial blood flow as the result of a poor oper¬ ation. Although surgeons at Cleveland Clinic14 have found triple vessel disease to be a major risk factor, our results are no in this group of patients *Class I, asymptomatic; class II, angina with heavy than in worse the others, and we believe that exertion; class lll, angina with moderate exertion; the class IV, angina at rest. poor prognosis of patients receiving only medical treatment warrants sur¬ gical intervention. Table VII.Mortality data for the was carried in 183 patients from the National Defence Medical Centre in Ottawa by Dr. G.M. FitzGibbon. Of 511 grafts inserted 90.5% were patent 3 to 6 weeks after operation and 84% were

out

509 patients who underwent elective aortocoronary bypass grafting between April 1970 and March 1974, by

ventricular function

Preoperative

No. (and

Left ventricular function We

%) of deaths

analysed

the

mortality

data for

Emergency grafting Our early experience with emergency aortocoronary bypass grafting has been described.18"20 We continue to advocate emergency grafting for patients with cardiogenic shock, acute unstable myo¬ cardial infarction and preinfarction an¬ gina; our results in these circumstances between December 1970 and April 1975 are presented in Table VIII. Al¬ though one group21 has reported a 100% operative mortality for emer¬ gency grafting in patients with acute un¬ stable myocardial infarction, none of our patients died at operation. Eight patients underwent emergency grafting because of serious disease and difficul¬ ties during angiography. Our general objectives in emergency grafting are to prevent the loss of myo¬ cardial tissue due to ischemia, to minimize the size of

a

pre-existing

Table VIII.Mortality data for the 141 patients who underwent emergency Total Operative Late aortocoronary bypass grafting between December 1970 and April 1975 190 1 (0.5) 4 (2.1) 5 (2.6) 88 1 (1.1) 0 1 (LD 136 2 (1.5) 9 (6.6) 11 (8.1) 50 4 (8.0) 10 (20.0) 14 (28.0) IV 45 4 (8.9) 15 (33.3) 19 (42.2) n no. of patients. ?Class 1,25% hypokinesia;class 11,50% hypokine¬ sia; class lll, 75% hypokinesia; class IV, 100% hypo¬ kinesia. n no. of patients. 314 CMA JOURNAL/FEBRUARY 21, 1976/VOL 114

functional class Normal I

n

=

=

aorto¬

coronary bypass grafting up to March 1974 by preoperative ventricular func¬ tion, classifying function by degree of hypokinesia according to the ejection fraction and left ventricular angiogram; the results are presented in Table VII. Some believe that preoperative con¬ gestive heart failure is the most im¬ portant predictor of a poor surgical result in aortocoronary bypass graft¬ ing,4,6 but in our recent study we found that 66% of patients with congestive heart failure were helped by myocardial revascularization.15 We believe, as do others,5'8'9,12'16'17 that poor preoperative ventricular function is the most impor¬ tant predictor of death for patients un¬ dergoing this procedure; both operative and late mortality were high in patients with class IV ventricular function in the present series. Although some advocate that no patient with poor left ventricu¬ lar function should undergo bypass grafting,16 we believe that each patient should be evaluated separately, for our experience demonstrates that some pa¬ tients with class IV ventricular function can benefit from bypass grafting and resection of scar tissue. However, the patients who benefit most from such an operation are those with normal, class I or class II left ventricular func¬ tion; for them the operative mortality is less than 2%.

myocardial infarction, to alleviate the complications of acute infarction and to restore function of the cardiac pump so that effective circulation can be sustained. For patients in cardiogenic shock (blood pressure, K 80 mm Hg; venous pressure, . 15 mm Hg; signs of peripheral vascular insufficiency; clouded sensorium; urine output, K 20 ml/h; left ventricular end-diastolic pressure at catheterization, . 30 mm Hg; and cardiac index, K 2 1/rn2) we graft only major vessels with serious (>75%) obstruction and do so without cardiac arrest. For patients with acute unstable myocardial infarction (infarction occurring during catheterization, extending infarction, infarction with uncontrollable arrhythmia or infarction with low cardiac output) we graft all vessels with serious lesions; we use aortic crossclamping for occasional short periods if myocardial function is good. For patients with preinfarction angina (acute coronary insufficiency, unstable angina and crescendo angina) we use the elective technique of aortic crossclamping and cardiac arrest. Conclusions Left ventricular contractility is the most important predictor of death associated with aortocoronary bypass grafting. Inadequate surgical procedure, as

indicated by little increase in coronary blood flow, is the other identifiable cause of death. Controlled studies to assess the effect of aortocoronary bypass on survival must establish rigid criteria to assess these two factors. Insertion of several grafts decreases mortality. Patients with triple vessel disease who have good ventricular function have a much better prognosis when treated surgically. We continue to advocate emergency grafting for patients with cardiogenic shock, acute unstable myocardial infarction and preinfarction angina. We thank Mrs. Elizabeth Masson for her help in preparing the manuscript. This study was supported by the Ontario Heart Foundation. References 1. FAVALORO RG: Saphenous vein autograft replacement of severe segmental coronary artery occlusion. Operative technique. Ann Thorac Surg 5: 334, 1968 2. JOHNSON .D, FLEMMA RD, LEPLEY D ja, et al: Extended treatment of severe coronary artery disease: a total surgical approach. Ann Surg 170: 460, 1969 3. DUNKMAN WB, PERLOFF JK, KASTOR JA, et al: Medical perspectives in coronary artery surgery - a caveat. Ann Intern Med 81: 817, 1974 4. CANNOM DS, MILLER DC, SHUMWAY NE, et

al: The long-term follow-up of patients undergoing saphenous vein bypass surgery. Circulaion 49: 77, 1974 5. NAJMI M, U5HIMAYAK, BLANCO G, et al: Results of aorto-coronary artery saphenous vein bypass surgery for ischemic heart disease. Am I Cardiol 29: 180, 1972 6. Loop FD, FAvALORO RG, SHIXEY EK, et al:

Surgery for combined valvular and coronary heart disease. JAMA 220: 372, 1972 Myocardial revascularization: operative mortality in the Cleveland Clinic experience. Cleve Clin Q 41: 51, 1974 8. JOHNSON WD: Surgical techniques of myocardial revascularization: an overview. Bull NYAcad Med 48: 46, 1972 9. The University of Toronto Interhospital Cardiovascular Surgery Group: The first 1000 coronary artery repair operations in Toronto. Can Med Assoc J 111: 525, 1974 10. HuTcHisoN JE, GREEN GE, MEKHJIAN NA, et al: Coronary bypass grafting in 376 consecutive patients, with three operative deaths. J Tlzorac Cardiovasc Surg 67: 7, 1974 7. BENNEi-r D, LooP RD, SHELDON WS, et al:

11. ANDERSON

RP,

RAHIMTOOLA

SH,

BONCHEK

LI, et al: The prognosis of patients with coronary artery disease after coronary bypass operations. Circulation 50: 274 1974 12. HALL RJ, DAwsoN JT, COOLEY DA, et al: Coronary artery bypass. Circulation 47

(suppl 3): 146, 1973 13. OBERMAN A, JONES WB, Ruay CP, et al: Natural history of coronary artery disease. Bull NY Acad Med 48: 1109, 1972 14. Loot FD, BERRETiTONI JN, PICHARD A, et al: Selection of the candidate for myocardial revascularization. J Thorac Cardiovasc Surg

69: 40, 1975 15. B.DARD P, KEON WJ, TAYLOR G, et al: Surgery for coronary artery disease and congestive heart failure. Can J Surg 18: 237, 1975 16. REA WJ, EcItER RR, MuLLsNs CR, et al: Importance of ventricular function in predicting operative mortality in aorto-coronary bypass

grafts. Circulation 43 (suppl 2): 215, 1971 17. KONG Y, BARTEL AG, BEHAR VS, et al: Aorto-coronary bypass graft: pre-operative correlates of mortality. Ibid p 101

18. KEON WJ, ABBAs SZ, SHANKAR KR, et al:

Emergency aorto-coronary venous bypass graft in cardiogenic shock. Can Med Assoc J

105: 1293, 1971 Experience with emergency aorto-coronary bypass grafts in the presence of acute myocardial infarction. Circulation 48 (suppi 3):

19. KEON WJ, B.DARD P, SHANKAR KR, et al:

151, 1973

20. KEON WJ, B.o4stD P, SHANKAR KR, et al:

Experience with emergency aortocoronary bypass grafts. Can J Surg 16: 268, 1973 21. HILL DJ, KERTIS WJ, KELLY JJ, et al: Emergency aorto-coronary bypass for impending or extending myocardial infarction. Circula-

tion 43 (suppl 1): 105, 1971

Preschool detection of asymptomatic bacteriuria: a public health program G.S. ARBUS, MD, FRCP[C1; R.C. WILLIAMS, B SC HONS, MD, DPH

A total of 9501o of parents registering their children for kindergarten agreed to screening for urinary tract Infection (UTI) in their children. Urine specimens from 1591 children (8701o), obtained at the school or at home, were tested. Only minor problems were encountered when parents prepared the specimens at home and mailed them to the laboratory for reading; the proportion of false-positive results was higher in these samples. If screening for UTI becomes established, it appears worth while to conduct this at the time of registration for kindergarten, either in From the department of pediatrics, The Hospital for Sick Children and the University of Toronto, and the Niagara Regional Health Unit, Niagara Falls, Ont. Reprint requests to: Dr. G.S. Arbus, Rm. 5109, The Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8

the school by lay persons or in the home by parents.

par des noninities, ou A Ia maison par les parents.

Ouatre-vingt-quinze pourcent (950/o) des parents inscrivant leurs enfants a un jardin d'enfants accepterent de faire subir un test de depistage des infections des voies urinaires a leurs enfants. Des echantillons d'urine provenant de 1591 enfants (870/o), obtenus a l'ecole ou a Ia maison, ont ete examines. On n'a rencontr6 que des problemes b6nins lorsque les echantillons furent pr6par6s a Ia maison par les parents et adress6s au laboratoire pour examen; c'est parmi ces echantillons que l'on releva Ia plus forte proportion de r6sultats faux.positifs. Si le depistage des infections des voies urinaires devient coutumier, ii apparait valable d'effectuer celui-ci au moment de l'inscription au jardin d'enfants, a l'6cole m6me

Generally, screening programs for the early detection of treatable diseases have been considered worth while,1 but recently the value of screening for asymptomatic bacteriuria in children has been questioned.2 Support for such a program will depend, initially, on research into the history of urinary tract infection (UTI) and, finally, on a cost/benefit analysis of these findings.2 We explored the possibility of combining a screening program to detect asymptomatic bacteriuria in children with other such programs at the time of registration for kindergarten, parental participation in the home being part of the procedure. We also compared two methods for detecting UTI; results of this comparison are not included here.

CMA JOURNAL/FEBRUARY 21, 1976/VOL 114 315