Risks of Coronary Arteriography and Bypass Surgery in Patients with Left Main Coronary Artery Stenosis

improved prebypass monitoring, expert anesthesia, and judicious afterload reduction. To achieve stability, the intra-aortic balloon pump was used preoperatively in 14 of their 74 patients. Although some may consider this usage excessive, stability was assured and the results speak for themselves. The role of the cardiothoracic anesthesiologist cannot be overemphasized. Stable induction and maintenance of anesthesia enable the surgeon to work quietly and confidently without fear of myocardial damage. Miller and his colleagues have chronicled

the evolution of optimal surgical treatment and set a standard of excellence. REFERENCES

1 Talcaro T, Hultgren HN, Lipton MJ, Detre KM, et aL The VA cooperative randomized study of surgery for coronary arterial occlusive disease. II. Subgroup with significant left main lesions. Circulation 1976; 54( suppl 3): 107-17 2 Chaibnan BR, Rogers WJ, Davis K, et al. Operative risks in left main coronary disease ( CASS), abstract Circulation 1979; 59( supp12) :59

Risks of Coronary Arteriography and Bypass Surgery in Patients with Left Main Coronary Artery Stenosis" Donald W. Miller, t-; M.D.;t Fredric M. Tobia, M.D.;; Tom D. Ivey, M.D.;§ and Simeon A. Rubenstein, M.D.II The risk of coronary arteriography is coDSiderably increased In patients who have left main coronary artery stenosis (LMCAS). Among 1,060 patients undergoinl coronary arteriography over a three-year period, 83 were found to have LMCAS and three of these patients died (3.6 percent) during or shortly after the arterlographlc procedure. Bypass surgery, however, can now be carried out at a very low risk irrespective of the degree of coronary disease present-there was no hospital mortdty in 74 patients with LMCAS undergoing bypass surgery at

our institution during this period. In addition to careful attention to detail, techniques that can minimize the risk of both of these procedures In patients with LMCAS Include Invasive bemodyaamlc monitoring and various pharmacologic manipulations to prevent myocardial ischemia. In a smaD percentage of patlen., rest angina may prove refractory to Inbospltal medical treatment, and intraaortlc baBoon pumpinI may be necessary to stabilize the conditions of these patients before proceeding with arteriography and myocard1al revascularlmtioD.

When the natural history of angiographically-defined coronary artery disease was established in the 1960s, those patients who had left main coronary artery stenosis (LMCAS) were found to have the worst prognosis. 1 Since then, coronary bypass surgery carried out with an operative mortality of 14 percent has been shown by a randomized trial to improve survival when compared with medical treatment," The risks of both coronary arteriography

and bypass surgery, however, have been reported to be considerably higher in patients with LMCAS than in patients with atherosclerotic diseases conflned to one or more of the other major coronary arteries. In this report, our experience with the angiographic diagnosis and surgical treatment of patients with LMCAS over the last three years at the University of Washington is reviewed.

·From the Divisions of Cardiology and Cardiothoracic SurUniversity Hospital, University of Washington, Seat-

E:'

t Associate

Professor and Chief, Division of Cardiothoracic Surgery, Department of Surgery. tClinical Fellow, Division of Cardiology, Department of Medicine. §Assistant Professor, Division of Cardiothoracic Surgery, De~arbnent of Surgery. IIClinical Associate Professor, Division of Cardiology, Department of Medicine. Presented in part at the VII Asian-Pacific Congress of Cardiology, Bangkok, Thailand, Nov 30, 1979. Manuscript received February 11; revision accepted May 27. Be"rint request8: Dr. Millefo:J Department af Surgefl/ RF 25, urOOer8ltr/ of WDBhington:J Seattle 98195

CHEST, 79: 4, APRIL, 1981

METHODS

Patients

The catheterization records of 1,060 patients who had coronary arteriography done by a group of ten attending cardiologists at the University Hospital, University of Washington, from January 1976 through December 1979 were reviewed. The presence of LMCAS greater than 50 percent arterial diameter narrowing was found in 83 patients (7.8 percent). Catheterization deaths are defined as any death occurring within 24 hours of catheterization or later if complications related to the procedure were responsible for the death. Seventy-four patients were referred to us (DWM and

RISKS OF CORONARY ARTERIOGRAPILY AND BYPASS. SURGERY 387

TOI) for bypass surgery at UDiversity Hospital dwing this three-year period: 45 University Hospital catheterization patients, and 29 patients studied at other institutions. Eighteen University Hospital catheterization patients did not undergo surgery, and 20 were electively operated upon elsewhere. BIIPtJ88 Surge'll

Catheterization Patients (n==83) Age, yr

Bypass grafting was done with autogenous veins following, in most cases, a slow narcotic anesthetic induction. Proximal aortic-saphenous vein anastomoses were constructed over a partially occluding aortic clamp on cardiopulmonary bypass; the aorta was then crossclamped and a cold potassium cardioplegic solution infused into the aortic root for myocardial preservation during construction of distal saphenous veincoronary artery anastomoses, as previously deseribed.s Quantitative serum CK-MB isoenzyme levels were measured at 0, 6, and 24 hours postoperatively (normal range 0 to 6 U/L ).3 Perioperative myocardial infarction was identified by the occurrence of new Q-waves greater than 0.04 second in any two leads of the standard 12-lead ECC.

REsuLTS Clinical Findings There were no significant differences between 83 catheterization patients and 74 bypass surgery patients with regard to any of the clinical findings listed in Table 1. Five catheterization (cath) patients had no chest pain: two were studied because of an abnormal exercise test; one because of the history of sudden death; and one each because of manifestations of aortic and mitral valve disease, respectively. Of the 18 patients (23 percent) with rest angina, 15 had unstable angina (angina at rest relieved by nitroglycerin), one had preinfarcation angina (medically refractory unstable angina), and two had postinfarct angina (angina occurring shortly after an acute myocardial infarction). The duration of angina averaged 4.2 years in this group; only 26 patients had anginal symptoms for less than one year. Hypotension (fall in systolic blood pressure < 20 mm Hg) during exercise testing occurred in 22 of the 48 patients so studied (46 percent). Five bypass surgery patients had no chest pain: LMCAS was associated with aortic stenosis and mitral regurgitation in one patient each; two had sudden death; and one patient had no symptoms but had hypotension during exercise testing. Of the 15 patients (20 percent) with rest angina, 11 had unstable angina, two had preinfarction angina, and two had postinfarct angina.

CoronaryArteriography The femoral approach" was used in 74 percent of the patients in this laboratory and brachial approach in 16 percent. Left ventriculography was not done in 23 patients (28 percent) after they were found to

388 MILLER ET At

Table l--eUnieal Findi... in Paliem. ..,i,1a LMCAS·

Men History of angina pectoris No chest pain Effort angina only Rest and effort angina

Bypass Surgery Patients (n-74)

60.0 (36-79) 56.1 (36-74)

%

%

80

74

6 71 23

7 73 20

History of myocardial infarction Pathologic Q-waves on ECG Recent MY «3 weeks)

43 4

38 3

History of sudden death

10

9

Treated with propranolol 70 82 Average daily dose, mg (range) 185 (30-400) 172 (30-400) Arteriographic findings Percent LMCAS: 50-69 70-89 90-99 100 Isolated LMCAS Associated RCA disease Complete occlusion Ejection fraction

>50% 35-50% <35%

%

%

30

24

45 28 3

38 28 4

4

5

77 47

76 41

%

%

(33 of 48) 69 (32 of 43) 74 (8 of 48) 17 (8 of 43) 18 (7 of 48) 14 (3 of 43) 7

*All values are percent unless otherwise indicated. have severe LMCAS, in order to minimize the risk of the catheterization procedure. Initial left coronary view showed shallow RAO in 59 percent and shallow LAO in 41 percent. Number of coronary injections ranged from 3 to 16 (mean 6.6). There were three (3.6 percent) catheterization deaths. One death occurred six hours after catheterization in a 46-year-old man who had occlusion of the LMCA and inoperable disease. This patient sustained a myocardial infarction prior to catheterization and had had an intraaortic balloon pump ( IABP) inserted for cardiogenic shock. A second death occurred in a previously active 73-year-old man with unstable angina. During selective cannulation of the LMCA, the patient sustained a cardiac arrest and could not be resuscitated. Postmortem perfusion-fixed coronary radiography disclosed a 95 percent LMCAS. A third patient, a 46-year-old man with preinfarction angina, developed sudden, profound, low cardiac output and bradycardia abruptly after the fourth injection of the right coronary artery, with angiographic findings of 90 percent LMCAS and 95 percent RCA stenosis. He died 12 hours later, remaining in irreversible cardiogenic shock, despite

CHEST, 79: 4, APRIL, 1981

maximum resuscitative measures which included ventilatory support, vasoactive drugs and emergency bypass grafting and balloon pump insertion. Another patient, a 44-year-old man with postinfarct angina, became asystolic following injection of contrast material into the left coronary artery (the 12th injection of the study) with arteriographic findings of isolated 90 percent LMCAS. Electromechanical activity could not be restored and continuous external cardiac massage was necessary to sustain life until the patient could be placed on cardiopulmonary bypass, approximately 45 minutes after initiation of resuscitative efforts in the catheterization laboratory. This patient survived neurologically intact and is back at work one year later. He required prolonged postoperative IABP support and hemodialysis; serum creatine phosphokinase level rose to 48,000 IU/L and CK-MB rose to 315 U/L after surgical resuscitation, but the ECG was unchanged compared to the tracing taken immediately before catheterization. No instances of stroke, ECG-documented myocardial infarction, or vascular complications occurred in the 80 patients who survived cardiac catheterization in this study. Among the other 977 patients undergoing coronary arteriography during this three-year period who did not have LMCAS, there was one death (0.1 percent), in a 47-year-old man with idiopathic hypertrophic subaortic stenosis and single vessel coronary disease. Bypass Surgery

No deaths occurred in the 74 patients who survived angiographic diagnosis and underwent coronary bypass surgery for LMCAS (Table 2). Nine patients underwent surgery within 24 hours of catheterization; 35 were operated upon one to seven days later; and 30 patients, more than one week later. In addition to bypass grafting (average 2.7 grafts/patient), ventricular aneurysmectomy was performed in two patients, aortic valve replacement in two, aortic valve commissurotomy in one, and mitral valve replacement in one patient. The IABP was employed preoperatively in 14 patients (before catheterization in three, before anesthetic induction in 11, and after cardiopulmonary bypass in one). Balloon pump insertion was attempted unsuccessfully preoperatively in three patients; one of these patients, a 68-year-old man with preinfarction angina, required IABP support after bypass, placed through the ascending aorta. This was the only instance in this series where IABP was required after cardiopulmonary bypass. Two patients sustained a perioperative myocardial infarction by ECG criteria without clinical sequelae, but serum CK-MB isoen-

CHEST, 79: 4, APRIL, 1981

Table 2-Morbiffi.,. and Moraali.y .4faer Bypa.. Sur.ery in 74 Paden.. ",i.h LMCAS

o

Hospital mortality Complications Perioperative myocardial infarction Reoperation for mediastinal bleeding Postpericardiotomy syndrome Tension pneumothorax Hyperbilirubinemia Sternal dehiscence Leg wound infection Hepatitis Pulmonary embolism Pulmonary insufficiency Cholecystitis

2 (2.7 percent) 6 (8.0 percent) 3 (4.0 percent) 2 2 2 2 1

1 1 1

zyme levels rose to some degree in all patients postoperatively (mean peak CK-MB 26.0 U/ L, range 12 to lOB). Of the three patients who had peak CK-MB levels >50 U/L postoperatively, none required inotropic drugs or had Q-wave ECG changes, and technetium pyrophosphate scans done two to four days postoperatively were normal. Fourteen patients had ventricular premature beats postoperatively requiring treatment, and one patient had an episode of ventricular fibrillation without sequelae. Ten patients (13.5 percent) received inotropic drugs for hypotension, and 38 (51 percent) received intravenous nitroprusside to maintain the mean arterial pressure 'below 110 mm Hg. The spectrum of postoperative complications which occurred in the bypass surgery patients is listed in Table 2. In addition to those listed in this table, one patient sustained an aortic dissection during surgery which was repaired uneventfully. DISCUSSION

Risk ofCoronary Bypass Surgery for LMCAS

Prior to 1975, an operative mortality of 10 percent to 16 percent was generally reported for this procedure in patients with LMCAS.2,S In the Veterans Administration cooperative randomized study of bypass surgery in patients with LMCAS, the operative mortality was 14 percent," Talano and colleagues" reported an 11 percent operative mortality in 145 patients with LMCAS in 1975;5 Zeft et al6 a 10.6 percent operative mortality in 56 patients in 1974; and Cohen and Oorlin,? a 12.5 percent mortality in 45 patients in 1974. More recently, operative mortality of less than 2 percent is being reported in bypass surgery for LMCAS.8-11 McConahay and associates" had two deaths in 146 patients (1.4 percent); Loop et al 10 had one operative death in their last 80 patients. In this operative series of 74 patients, and in the recently reported experience of Anderson and as-

RISKS OF CORONARY ARTERIOGRAPHY AND BYPASS SURGERY 389

soeiates" with 40 patients, no deaths occurred with bypass surgery for LMCAS. The risk of bypass surgery is now comparable to the risk of coronary arteriography in patients who have LMCAS. Risk of Coronary Arteriography Before 1975, the overall catheterization mortality was 2.9 percent in eight studies of patients with LMCAS12 (ten deaths in 345 patients), ranging from no deaths in a report of 56 patients to five deaths in 32 patients (16 percent) in another report," In recent years, catheterization mortality of less than 1 percent is being more widely reported in patients with LMCAS.13-15 Davis et al 13 reported five catheterization deaths in 657 patients with LMCAS (0.76 percent) from 13 institutions participating in the Coronary Artery Surgery Study, and Farinha et al 14 had three deaths in 297 patients (1 percent). No catheterization deaths occurred in 176 patients with LMCAS at one institution" or in 130 patients at another institution.15 Most coronary arteriography deaths occur in patients who have LMCAS. Twenty-six of 14,050 patients (0.19 percent) died following coronary arteriography in the combined experience of 16 cath labs in the State of Washington during a recent threeyear period." Most of these deaths were in patients with LMCAS (20 of 26). Similarly, Bourassa and Noble'? reported a mortality rate of 0.23 percent (12 deaths) in 5,250 patients undergoing coronary arteriography; 11 of these 12 people had LMCAS. Another cooperative study reported eight deaths occurring within 24 hours after catheterization in 7,533 patients (0.11 percent), four of which were in patients with LMCAS.18 In the experience reported here, three of four catheterization deaths in 1,060 patients were in patients who had LMCAS.

Clinical Findings While a substantial number of patients with LMCAS have an unstable angina pattern marked by varying degrees of severity of angina at rest, the incidence of unstable angina does not vary substantially between these patients and those whose coronary disease does not involve this artery," Approximately 40 percent to 50 percent of patients found to have LMCAS at angiography have had a previous myocardial infarction, a finding which is equally prevalent in patients with obstructive lesions involving one or more of the other three major coronary arteries," Marked impairment of exercise performance, as measured by the duration of symptomlimited exercise, severity, and duration of ST segment depression, and the heart rate and blood

•

MILLER ET AL

pressure response to exercise, is highly predictive of severe coronary disease, but is not specific for LMCAS.8 Indeed, LMCAS is a manifestation of severe generalized coronary disease, and there are no precise clinical features that invariably suggest the diagnosis of this lesion among other types of severe two-vessel and three-vessel disease. Isolated LMCAS occurred in only 4 percent of our patients undergoing catheterization, a frequency typical of other reports as well. In most reports the incidence of LMCAS ranges between 4 percent and 9 percent in patients with clinical manifestations of coronary artery disease who undergo coronary arteriography. 7,8, 12,14,15

Techniques for Minimizing the Risk Arteriography

at

Coronary

Patients with LMCAS should be brought to the catheterization laboratory in a stable condition. If medical management is ineffective, IABP support should be used to control symptoms of angina at rest. With the advent of the Swan-Ganz catheter (for monitoring pulmonary artery [PA] and pulmonary capillary wedge [pCW] pressures and thermodilution cardiac output) and IABP support (to reduce myocardial oxygen consumption and improve myocardial blood How), it is now possible to stabilize most patients who have angina at rest." We had one catheterization death which might have been prevented had IABP been employed to gain control of anginal symptoms before catheterization, in a patient who had medically refractory (preinfarction) rest angina. In an occasional patient, however, IABP insertion may not be possible due to advanced peripheral vascular disease, as was the case in one of our patients with unstable angina who died at catheterization. The hazards of abruptly stopping propranolol have been well documented." It is advisable to continue therapy with this beta-blocking agent through cardiac catheterization and up to the time of bypass surgery, and in some cases, even increase the dose preoperatively. Prophylactic pacemakers are rarely required in patients who have angina pectoris but may be advisable in the minority who have bifasicular block, or possibly complete left bundle branch block. Many angiographers also empirically administer heparin to all patients at the time of cardiac catheterization. Conti and associatesf in a comprehensive review of LMCAS, point out the importance of using high-quality angiographic equipment with state-ofthe-art video display and video playback capabilities in order to immediately recognize the presence of

CHEST,- 79: 4, -APRIL, 1981

LM·CAS. We, with others," have found that large film studies are unnecessary and have the disadvantage of precluding fluoroscopic visualization during the coronary injection. It would appear, from the multicenter report of Davis and colleagues," that both the brachial and femoral artery approach for coronary arteriography are equally safe when used by experienced angiographers. Opinion is divided among angiographers as to whether a shallow right anterior oblique ( RAO ) or left anterior oblique (LAO) best images the LMCA.7,S,20 A shallow RAO view is often used to identify intially stenotic lesions in the LMCA, but a shallow LAO view may, at times, best image ostial lesions of the LMCA. Catheter tip pressures should be monitored during cannulation of both left and right coronary ostia, and if the pressure becomes damped or "ventricularized"-diastolic pressures approximating the ventricular diastolic pressure-the catheter tip should be promptly removed and a "cusp" injection done. 7,15 In patients who have evidence of recurring myocardial ischemia at rest, as manifested by angina and ST changes on the V:5 lead of the ECG, nitroglycerin should be administered and the coronaries not injected until these signs of ischemia have abated.15 In one patient in our series, the arteriographic study was terminated after the onset of severe pain and prolonged ST segment depression following a left coronary injection. The IABP support was then instituted, and the study was completed without incident. In patients with this potentially lethal lesion, alterations in heart rate and blood pressure, chest pain, and ST segment depression should all resolve before proceeding further with arteriographic studies. Hemodynamic management of unstable patients during catheterization can be facilitated by monitoring PA pressures to detect and promptly treat incipient left ventricular power failure. In a patient found to have LMCAS, the number of coronary injections should be limited to two or at most, three injections of the left coronary artery, as is now our current practice. 7,IS,20 Two of our patients sustained cardiovascular collapse after multiple coronary injections: one patient died after the fourth RCA injection (total of seven injections), and one patient after the twelfth coronary injection. While a number of the patients in this series survived multiple (up to 16) coronary injections, it is clear that an occasional patient with LMCAS will deteriorate after multiple injections, and only the minimum number necessary for diagnosis and surgical treatment should be attempted in these highrisk patients. Mter catheterization, patients with LMCAS should be monitored in a coronary care unit during the first 24 hours. CHEST, 79: 4, APRIL, 1981

Techniques for MinimiZing the gery

Risk of Bypass Sur-

Two important factors which may account for the improvement in surgical results now obtained in patients with LMCAS are careful hemodynamic monitoring during anesthetic induction and improved techniques of myocardial preservation. By monitoring systemic blood pressure, PA pressure (and PCW pressure), and the V5 ECG lead, the cardiac anesthesiologist is now able to prevent myocardial oxygen demands from exceeding oxygen supply during anesthetic induction in these patients. 21 Patients with LMCAS can be safely induced for anesthesia by avoiding serious fluctuations in blood pressure, heart rate, and ventricular function through appropriate pharmacologic manipulations. Treatment interventions include intravenous nitroprusside or nitroglycerin to prevent increased afterload, volume administration to optimize preload, intravenous propranolol to control heart rate, neosynephrine for hypotension, and dopamine, when required, to improve myocardial contractility. A slow narcotic anesthetic induction for patients with severe coronary disease is preferred by a number of cardiac anesthesiologists.21 The IABP has been advocated to reduce the risk of anesthetic induction in patients with LMCAS.22,23 We used it preoperatively in 19 percent of patients operated upon in this series. In other reported series of bypass surgery for LMCAS, however, very good results have been reported when preoperative IABP is not used. 11 When anesthesia is expertly induced, it would appear than IABP is not necessary in patients who are brought to the operating room in a stable condition, without ongoing myocardial ischemia. In our current practice, we no longer employ IABP preoperatively except in patients with preinfarction angina and in postinfarct angina when resting myocardial ischemia cannot be reversed by medical treatment. Since the use of IABP carries some risk, it should not be used prophylactically when anesthetic induction is expertly performed by an experienced cardiac anesthesiologist. In 1975, only 5 percent of cardiac surgeons across the country used cold (potassium) cardioplegia for myocardial preservation during bypass surgery.P' In the last five years, this technique of myocardial protection has been widely heralded. 24,2s Combined with the precise execution of bypass graft anestomoses and complete revascularization, it is generally agreed that the myocardial protection afforded by this technique has helped to reduce the risk of

RISKS OF CORONARY AmRIOGRAPHY AND BYPASS SURGERY 381

bypass surgery in general. 26 We prefer to perform proximal anastomoses first on cardiopulmonary bypass, so that the heart is immediately revasularized following the period of ischemic (cardioplegic) arrest required for performance of the distal anastomoses. The successful performance of coronary arteriography and bypass surgery in patients with LMCAS requires careful attention to detail, with appropriate hemodynamic monitoring and pharmacologic manipulations to prevent myocardial ischemia. So practiced, the risk of angiographic diagnosis, and myocardial revascularization of patients with LMCAS is now very low. ACKNOWLEDGMENT: We gratefully acknowledge the assistance of Paula M. Nichols, R.N., in data collection.

1 Bruschke AVG, Proudfit WL, Sones FM Jr. Progress study of 590 consecutive nonsurgical cases of coronary disease followed 5-9 years; I. Arteriographic correlations, and Il, Ventriculographic considerations. Circulation 1973; 47:1147-63 2 Takaro T, Hultgren HN, Lipton MJ, et a1. The VA cooperative randomized study of surgery for coronary arterial occlusive disease: II. Subgroup with significant left main lesions. Circulation 1976; 54 (suppl 3): 10717 3 Miller DW Jr. The practice of coronary artery bypass surgery. New York: Plenum Medical Book Co, 1977 4 Judkins MP. Selective coronary arteriography: a percutaneous transfemoral technic. Radiology 1967; 89:81520 5 Talano SV, Scanlon PJ, Meadows WR, et ale Influence of surgery on survival in 145 patients with left main coronary disease. Circulation 1975; 52 (suppl 1): 105-09 6 Zeft HJ, Manley JC, Huston JH, et ale Left main coronary artery stenosis: results of coronary bypass surgery. Circulation 1974; 49:68-76 7 Cohen MV, Corlin R. Main left coronary artery disease: clinical experience from 1964-1974. Circulation 1975; 52:275-85 8 Conti CR, Selby JH, Christie LG, et a1. Left main coronary stenosis; clinical spectrum, pathophysiology, and management. Prog Cardiovasc Dis 1979; 22:73-106 9 McConahay DR, Killen DA, McCallister BD, et ale Coronary artery bypass surgery in patients with left main coronary artery disease. Am J Cardiol 1976; 35: 153-57

392 MILLER n AL

10 Loop FD, Lytle BW, Cosgrove DM, et ale Atherosclerosis of the left main coronary artery: 5 year results of surgical treatment. Am J Cardio11979; 44:195-201 11 Anderson RP, Wei-i L, Balfour RI, et ale Surgical management of left main coronary artery stenosis and ischemic left ventricular dysfunction. J Thorac Cardiovasc Surg 1979; 77:369-76 12 Mehta J, Hamby RI, Hoffman I, et ale Medical-surgical aspects of left main coronary artery disease. J Thorac Cardiovasc Surg 1976; 71:137-41 13 Davis K, Kennedy]W, Kemp HG Jr, et aI. Complications of coronary arteriography from the collaborative study of coronary artery surgery ( CASS). Circulation 1979; 59:1105-11 14 Farinha JB, Kaplan MA, Harris CN, et ale Disease of the left main coronary artery: surgical treatment and longterm followup in 267 patients. Am J Cardiol 1978; 42: 12428 15 Iskandrian AS, Segal BL, Mundth ED. Appraisal of treatment for left main coronary disease. Am J Cardiol 1977; 40:291-93 16 Hansing CE. The risk and cost of coronary arteriography: II. The risk of coronary angiography in Washington state. JAMA 1979; 242:735-38 17 Bourassa MG, Noble J. Complication rate of coronary arteriography-a review of 5,250 cases studied by a percutaneous femoral technique. Circulation 1976; 53: 10614 18 Gold HK, Leinbach RC, Sanders CA, et al. Intraaortic balloon pumping for control of recurrent myocardial ischemia. Circulation 1973; 47:1197-1203. 19 Alderman EL, Coltant J, Wettock GE, et al, Coronary artery syndromes after sudden propranolol withdrawal. Ann Intern Med 1975; 82:431-35 20 Page HL, Campbell WB. Percutaneous transfemoral coronary arteriography: prevention of morbid complications. Chest 1975; 67:221-25 21 Kaplan JA (Ed). Cardiac anesthesia. New York: Grune and Stratton, 1979 22 Rajai HR, Hartman CW, Innes BJ, et ale Prophylactic use of intra-aortic balloon pump in aortocoronary bypass for patients with left main coronary artery disease. Ann Surg 1978; 187:118-21 23 Cooper GN, Singh AK, Christian FC, et ale Preoperative intra-aortic balloon support in surgery for left main coronary stenosis. Ann Surg 1977; 185:242-45 24 Miller DW Jr, Hessel EA II, Winterscheid LC, et al, Current practice of coronary artery bypass surgery: results of a national survey. J Thorac Cardiovasc Surg 1977; 73:75-79 25 Kirklin ]W, Conti VB, Blackstone EH. Prevention of myocardial damage during cardiac operations. N Engl J Med 1979; 301: 135-41

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