Mortali. TheChangin. of Mvocardi Revas arization: Coronarv Me& Bypass and Angioplasty

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1 TheChangin S Mortali J of Mvocardi Revas arization: Coronarv J Me& Bypass and Angioplasty Keith S. Naunheim, M.D., Andrew C. Fiore, M.D., J. Jeffrey Wadley, B.A., Kirk R. Kanter, M.D., Lawrence R. McBride, M.D., D. Glenn Pennington, M.D., Hendrick B. Barner, M.D., Ubeydullah Deligonul, M.D., Morton J. Kern, M.D., Michel Vandormael, M.D., Vallee L. Willman, M.D., and George C. Kaiser, M.D. ABSTRACT The risk factors and outcome for the first 150 consecutive patients undergoing coronary artery bypass grafting (CABG) in 1985 (CABG '85) were compared with those of the first 150 patients undergoing CABG in 1975 (CABG '75) and those of the first 150 patients to have percutaneous transluminal coronary angioplasty (PTCA) in 1985 (PTCA '85). The CABG '85 patients had a significantly higher (p < 0.05) incidence of known operative risk factors including advanced age, female sex, severity of angina, history of recent infarction, triple-vessel disease, left ventricular dysfunction, and emergency operation than the CABG '75 cohort. The clinical profile of the PTCA '85 patients closely resembled the low-risk profile found in the CABG '75 patients. Overall mortality following CABG more than doubled during the decade studied (3% versus 7%, p = 0.07). This study suggests that the increased mortality associated with CABG in 1985 is due in part to the inclusion of more high-risk patients in the surgical population. In addition, the application of PTCA removes lowrisk patients from the surgical candidate pool and adds more patients requiring emergency operations, thereby further contributing to the overall decline in the clinical status of patients referred for operation. Throughout the 1970s and early 1980s, coronary artery bypass grafting (CABG) was widely recognized as effective therapy for coronary artery disease. It also could be undertaken with low operative morbidity and mortality. Recently, many statements from both government and lay community sources have suggested that the risk of CABG has increased, perhaps to unacceptable levels [l, 21. Two factors which have been implicated are the deteriorating clinical status of the patient coming to CABG and the substitution of percutaneous transluminal coronary angioplasty (PTCA) in place of CABG in low-risk From the Departments of Surgery and Cardiology, St. Louis University Medical Center, St. Louis, MO. Presented at the Twenty-third Annual Meeting of The Soaety of Thoracic Surgeons, Toronto, Ont, Canada, Sept 21-23, Address reprint requests to Dr. Naunheim, Department of Surgery, St. Louis University Medical Center, 1325 S. Grand Blvd, St. Louis, MO patients. We have previously demonstrated that the clinical status of patients undergoing CABG currently is worse than that previously noted [3]. We undertook the present study to evaluate the effects of PTCA on this phenomenon. Material and Methods The medical records of three patient groups from St. Louis University Medical Center were retrospectively analyzed. The first group (CABG '75) consisted of the first 150 consecutive patients who underwent surgical revascularization beginning on January 1,1975. The second group (CABG '85) comprised the first 150 consecutive patients to undergo CABG in The first 100 patients of each group have been reported on previously [3]. A larger number of patients has been subsequently reviewed with the hope of improving statistical validity. The last group (PTCA '85) included the first 150 patients undergoing PTCA beginning on January 1, Age and sex were noted for each patient. Cardiac history data recorded included angina severity (assessed according to the Canadian Cardiovascular Society classification), history of recent (30 days or less) or remote (more than 30 days) myocardial infarction, history of documented arrhythmia, history of congestive heart failure requiring digoxin and furosemide treatment, and history of prior bypass procedures. Associated vascular disorders noted included essential hypertension, cerebrovascular disease (history of carotid endarterectomy, stroke, or transient ischemic attack), peripheral vascular disease (presence of claudication, rest pain, or aneurysmal disease), and renovascular disease (creatinine level, 2.0 mg/dl or more). The presence of diabetes mellitus (requiring insulin or oral medication) and of documented chronic obstructive pulmonary disease was also recorded. Catheterization findings noted included the number of diseased vessels (70% obstruction or more of vessel diameter in any plane), presence of left main coronary occlusive disease (50% obstruction or more), and left ventricular (LV) functional assessment using the LV score as defined by the Coronary Artery Surgery Study (CASS) [4]. Other preprocedural variables noted included the use of intravenously administered nitroglycerin or the presence of cardiogenic shock (defined by systolic blood pressure less than 80 mm Hg and/or car- 666 Ann Thorac Surg , Dec Copyright by The Society of Thoracic Surgeons

2 667 Naunheim et al: Changing Mortality of Revascularization Table 1. Clinical Variables" CABG '75 CABG '75 vs CABG '85 CABG '85 vs PTCA '85 PTCA '85 vs Variable (N = 150) CABG '85 (N = 150) PTCA '85 (N = 150) CABG '75 Age (yrib <o.oool 61.4 f 9.4 < <o Female sex 20 (13) < (23) 29 (19) Diabetes 9 (6) < (21) 12 (8) COPD 2 (1) 13 (9) < (3) Htn 59 (39) 66 (44) 65 (43) PVD 9 (6) 16 (11) 15 (10) CVD 3 (2) 9 (6) 5 (3) RI 4 (3) 4 (3) 1 (1) "Numbers in parentheses are percentages. bdata are shown as the mean f the standard deviation. CABG = coronary artery bypass grafting; PTCA = percutaneous transluminal coronary angioplasty; = not significant; COPD = chronic obstructive pulmonary disease; Htn = hypertension; PVD = peripheral vascular disease; CVD = cerebrovascular disease; RI = renal insufficiency. diac index less than 2.0 L/min/m2 requiring use of an intraaortic balloon or intravenous administration of dopamine hydrochloride or dobutamine hydrochloride for hemodynamic support). Procedures were classified as elective, urgent, or emergency operations. Emergency procedures were defined as those performed for acute evolving myocardial infarction with or without cardiogenic shock and for failed PTCA with ongoing ischemia irrespective of hemodynamic stability. Urgent procedures were those performed on patients with angina refractory to intravenously administered nitroglycerin (with or without intraaortic balloon counterpulsation), patients with both crescendo angina and left main coronary artery disease, and patients undergoing PTCA within 48 hours after thrombolytic therapy for myocardial infarction under the Thrombolysis in Myocardial Infarction (TIMI) protocol [5]. All other procedures were considered elective. The number of distal anastomoses performed during CABG and the number of lesions dilated during PTCA were recorded. In addition, the number of patients undergoing complete revascularization was noted. Revascularization was considered complete with the restitution of flow (by balloon dilation or graft) to all vessels whose lumens were found to be 70% or more obstructed on angiography. Postprocedural mortality and morbidity were defined as death or complications occurring within 30 days after revascularization. Five patients were included in both the CABG '85 and PTCA '85 groups (patients in whom PTCA failed and who underwent immediate revascularization). Among these 5 patients, morbidity was not assigned solely to one group or the other, but was reported as occurring in each group. Mortality statistics were not affected because none of these patients died. A perioperative myocardial infarction was defined as (1) a new Q wave on the ECG made after the procedure; (2) a rise of more than 10 international units in the myocardial-specific isoenzyme of creatine-kinase; or (3) a rise in the lactate dehydrogenase (LDH) isoenzyme with a reversal of the LDHI:LDH2 isoenzyme ratio. A myocardial infarction was not registered as a postprocedural complication in those patients having revascularization for an evolving myocardial infarction unless a Q wave appeared in an area away from the original infarction. Similarly, low-output syndrome (defined as postprocedural requirements for an intraaortic balloon for hernodynamic stability) was declared a postprocedural complication only when it occurred in a patient who was in stable condition before the procedure without an intraaortic balloon in place. Other complications noted included respiratory insufficiency (postprocedural assisted ventilation for longer than 48 hours), peripheral vascular complication (thrombosis, embolism, or bleeding requiring operative intervention), focal neurological deficit, and acute renal insufficiency requiring dialysis. Statistical analysis was undertaken for nonparametric comparison using a chi-square test or Fisher's exact test for small sample size. Parametric differences were analyzed using a Student's t test. A p value of less than 0.05 was considered significant. Results CABG '75 versus CABG '85 The findings are similar but not identical to those already reported [3]. Over the ten-year interval, the mean age of the patients undergoing CABG rose by more than 9 years (p < ) and the proportion of patients who were female also increased significantly (p < 0.05) (Table 1). Th re were significant increases in the number of patients with chronic lung disease (p < 0.01) and diabetes mellitus (p < 0.001). In the 1985 cohort, the severity of angina had risen significantly and more patients had a history of arrhythmia (p < 0.05), or prior CABG procedure (p < 0.001), or had had an acute infarction within 30 days (p < ) (Table 2). The difference in incidence of female sex, angina severity, and arrhythmias was not observed in our previous study [3]. The variables examined at catheterization showed similar deterioration over the decade (Table 3). Although

3 ~~~ 668 The Annals of Thoracic Surgery Vol46 No 6 December 1988 Table 2. Cardiac History Variables" CABG '75 CABG '75 vs CABG '85 CABG '85 vs PTCA '85 PTCA '85 vs Variable (N = 150) CABG '85 (N = 150) PTCA '85 (N = 150) CABG '75 Angina severityb 3.0 & 1.0 < f 1.2 < & 1.5 Recent MI 4 (3) < (23) 46 (31) < Remote MI 62 (41) 61 (41) 34 (23) Arrhythmia 8 (5) < (14) < (6) CHF history 18 (12) 28 (19) < (5) Prior CABG 0 < (7) < 'Numbers in parentheses are percentages. bdata are shown as the mean f the standard deviation, and are based on the Canadian Cardiovascular Soaety classification. CABG = coronary artery bypass grafting; PTCA = percutaneous transluminal coronary angioplasty; = not significant; MI = myocardial infarction; CHF = congestive heart failure. Table 3. Catheterization Variables" Variable CABG '75 CABG '75 vs CABG '85 CABG '85 vs PTCA '85 FTCA '85 vs (N = 150) CABG '85 (N = 150) PTCA '85 (N = 150) CABG '75 No. of diseased vesselsb 2.2 f 0.8 < f 0.6 < f 0.7 < One 32 (21) < (7) < (50) < Two 59 (39) 46 (31) 61 (41) Three 59 (39) < (62) < (9) <O.OOol LM stenosis 25 (17) 28 (19) < (1) < LV scoreb < < f 3.0 Normal (LV score = 5) 67 (45) 42 (29) 57 (38) Mild dysfunction (6-10) 62 (42) 60 (41) 64 (43) Moderate dysfunction (11-15) 17 (11) 29 (20) 25 (17) Severe dysfunction (>15) 2 (1) 14 (10) 3 (2) "Numbers in parentheses are percentages. bdata are shown as the mean f the standard deviation. CABG = coronary artery bypass grafting; PTCA = percutaneous transluminal coronary angioplasty; = not sigruficant; LM = left main; LV = left ventricular. there was no increase in the number of patients with left main coronary artery disease, there was a significant worsening in the severity of coronary artery disease as measured by the mean number of diseased vessels (p < ) and by a markedly increased incidence of triplevessel disease (p < 0.001). LV function had also deteriorated as measured both by the mean LV score (p < ) and by the sevenfold increase in patients with severe ventricular dysfunction undergoing CABG (p < 0.01). These are similar to those reported previously [31. Significant changes appeared in operative variables as well (Table 4). The percentage of patients undergoing elective revascularization decreased because of a threefold increase in urgent operations (p < 0.01) and a fourteenfold rise in the number of emergency CABG procedures (p < 0.001). These changes are of greater magnitude than those noted previously [3]. The rise in emergency procedures primarily reflects the utilization of surgical intervention in 1985 for patients with acute ischemia, most of whom also were in cardiogenic shock. The proportion of patients undergoing complete revascularization rose significantly during this period (p < ) because of a significant increase in the mean number of anastomoses performed during CABG (p < ). The mortality for elective surgical revascularization (2%) was unchanged over the decade, and there were no significant differences in mortality between urgent and emergency operations (Table 5). However, the overall operative mortality more than doubled (3% versus 7%, p = 0.07) over the decade; this finding primarily reflects a change in case mix, that is, an increased proportion of high-risk urgent or emergency procedures. Table 6 lists postoperative complications. Significant increases occurred in the incidence of prolonged respirator support (p < 0.01) and permanent neurological deficit (p < 0.05). The rate of perioperative infarction decreased significantly if the combination of ECG and isoenzyme changes is taken together (p < 0.05). If ECG and isoenzyme changes are considered separately, the decline was not significant.

4 669 Naunheim et al: Changing Mortality of Revascularization Table 4. Operative Variables" Variable CABG '75 CABG '75 vs CABG '85 CABG '85 vs PTCA '85 PTCA '85 vs (N = 150) CABG '85 (N = 150) PTCA '85 (N = 150) CABG '75 Type of operation Elective Urgent Emergency Cardiogenic shock Evolving MI Failed PTCA No. of revascularizationsb Complete revascularization 145 (97) 4 (3) 1(1) 0 1 (1) (53) <0.001 <0.001 < < <0.001 < < <0.001 'Numbers in parentheses are percentages. bdata are shown as the mean? the standard deviation. CABG = coronary artery bypass grafting; FTCA = percutaneous transluminal coronary angioplasty; = not significant; MI = myocardial infarction. Table 5. Procedural Mortalitpb Procedure CABG '75 CABG '85 PTCA '85 Elective 3/145 (2) 3/122 (2) 4/127 (3) Urgent 114 (25) 3/14 (21) 5/22 (23) Emergency 111 (100) 5/14 (36) 111 (100) Overall (3) 11/150 (7) 10/150 (7) 'Numbers in parentheses are percentages. mere were no statistically significant differences between groups. CABG = coronary artery bypass grafting; PTCA = percutaneous transluminal coronary angioplasty. CABG '85 versus PTCA '85 The mean age of patients who underwent CABG in 1985 was 5 years greater than that of patients undergoing PTCA in the same year (p < ) (see Table 1). The general medical status was also worse in the CABG '85 patients as evidenced by a greater than twofold difference in the incidence of chronic obstructive lung disease (p < 0.05), diabetes mellitus (p < 0.01), and arrhythmias (p < 0.05), and a threefold difference in the incidence of congestive heart failure (p < 0.001) (see Tables 1, 2). CABG '85 patients had more severe angina (p < 0.001), which correlates with more severe coronary artery disease found at catheterization (see Table 3). There was a greater incidence of left main disease (p < ) and triple-vessel disease (p < ) in the surgical cohort. LV function as measured by mean LV score was significantly worse (p < 0.001) in the CABG '85 group and the proportion of patients with severe LV dysfunction was four times higher (p < 0.01). Operative variables were also notably different when these cohorts were compared (see Table 4). The CABG '85 patients underwent emergency procedures fourteen times as often as the PTCA '85 patients, mostly because of a greater number of patients seen with ischemic cardiogenic shock as the indication for intervention (p < 0.01). Fifty-four percent of the PTCA '85 patients had complete revascularization compared with 79% of the CABG '85 patients (p < ). This finding is corroborated by a comparison of the number of obstructive coronary lesions alleviated by the respective procedures. Table 6. Procedural Morbiditya CABG '75 CABG '75 vs CABG '85 CABG '85 vs PTCA '85 PTCA '85 vs Complication (N = 150) CABG '85 (N = 150) PTCA '85 (N = 150) CABG '75 MI New Q wave on ECG Isoenzyme elevation Low output Respiratory insufficiency Stroke Peripheral vascular Renal failure <0.05 <0.05 <0.05 <0.05 "Numbers in parentheses are percentages. CABG = coronary artery bypass grafting; PTCA = percutaneous transluminal coronary angioplasty; MI = myocardial infarction; = not significant.

5 670 The Annals of Thoracic Surgery Vol46 No 6 December 1988 The CABG '85 patients underwent a mean of distal anastomoses per patient compared with 2.0 f 1.3 coronary lesion dilations per patient in the PTCA '85 cohort. The overall mortality for both PTCA and CABG in 1985 was 7% (see Table 5). Elective procedural mortality within these two groups was virtually identical (PTCA, 3%, and CABG, 2%; p = not significant []). Procedural mortality was higher in patients undergoing urgent (PTCA, 23%, and CABG, 21%; p = ) and emergency (PTCA, loo%, and CABG, 36%; p = ) revascularization. The major significant difference in morbidity was the higher incidence of stroke in the CABG '85 cohort (p < 0.05). There were no significant differences between these two groups with regard to low-output syndrome, respiratory insufficiency, acute renal failure, or peripheral vascular complications. The incidence of postprocedural infarction was not significantly different between the two groups if judged only by the appearance of new Q waves on the ECG. However, there was a significant rise if either isoenzyme increases alone (p < 0.01) or the combination of isoenzymes and ECG changes (p < 0.05) is considered. PTCA '85 versus CABG '75 The mean age of patients who underwent PTCA in 1985 was 4 years higher than the mean age of patients undergoing CABG in 1975 (p < ) (see Table 1). The PTCA '85 group was revascularized more frequently after a recent infarction (p < ) and had a history of remote infarction less often (p < 0.01) than the CABG '75 group (see Table 2). Otherwise, there were no differences with regard to cardiac history or the incidence of concomitant medical diseases. Review of the catheterization variables demonstrated significantly more severe coronary artery disease in the CABG '75 group as measured by the mean number of diseased vessels (p < ) and the incidence of triple-vessel disease (p < ) (see Table 3). There was no difference in LV function as measured by mean LV score, and both these revascularization groups had a similar low incidence of patients with severe LV dysfunction. More patients in the PTCA group were classified as urgent revascularization, primarily because of the 15 TIM1 patients undergoing PTCA within 48 hours after infarction regardless of symptoms, as specified by the protocol [4] (see Table 4). The rates of complete revascularization were nearly identical (54% versus 53%) in the two groups. Neither mortality nor morbidity was significantly different when these groups were compared (see Tables 5, 6). Comment Over the past twenty years, multiple studies have been undertaken to analyze the operative risks of CABG. CASS included a prospective registry that cataloged the clinical, angiographic, and operative variables of more than 6,000 patients undergoing CABG between 1975 and The multi-institutional nature of that study as well as the large patient population assured a balanced distribution of patients from which valid conclusions could be drawn and applied to the population at large. Multivariate discriminant analysis of accumulated data demonstrated that several clinical variables had a significant (p < 0.01) deleterious effect on operative mortality. These variables were advanced age, left main coronary artery disease, female sex, and signs of congestive heart failure including abnormal LV score, elevated LV end-diastolic pressure, and the presence of rales [6]. When only patients more than 60 years of age were considered, unstable angina also became a significant predictor. An earlier univariate analysis [7] of the same patient cohort established emergency operation as a highly significant (p < 0.001) indicator of operative mortality; it led to a sixfold increase in mortality compared with elective revascularization. This was confirmed in the most recent multivariate analysis [8]. The risk of CABG has been demonstrated to be not only a multifactorial entity but also a dynamic process that has changed over time. Throughout the 1970s and early 1980s, the practice of cardiac surgery has continued to evolve. Improved surgical technique coupled with advances in instrumentation, techniques of myocardial preservation, anesthesia management, and perioperative care resulted in a continual decline in CABG mortality. Although it had been suggested that the decline may have been due to more stringent patient selection criteria [9], this has been refuted by several reports of retrospectively analyzed patients. Kouchoukos and colleagues [lo] compared CABG patients from the early 1970s to those of the mid-1970s. Their study demonstrated a decrease in mortality from 2.7 to 1.2% (p < 0.01) despite a shift toward more severe coronary artery disease and worsened concomitant medical problems in the patient population. Miller and associates [ll] reviewed two similar groups of patients undergoing CABG, one operated on between 1971 and 1975 and the other, from 1977 to The latter group was older, contained more women, and had more patients with congestive heart failure. In addition, several catheterization variables had significantly worsened over time; these included mean number of vessels diseased and LV function as measured by LV wall motion score, LV end-diastolic pressure, and ejection fraction. Despite this overall deterioration in preoperative status over the time interval, the operative mortality decreased significantly from 2.4 to 1.5%. Multivariate discriminant analysis was undertaken in both cohorts to determine independent predictors of mortality. Whereas emergency operation, left main coronary artery disease, congestive heart failure, hypertension, and mitral regurgitation were independent determinants of mortality in the early 1970s, only emergency operation and congestive heart failure persisted as risk factors in the latter period. Similar changes over time were noted by Cosgrove and associates [12]. They reviewed the records of more

6 671 Naunheim et a1 Changing Mortality of Revascularization than 24,000 patients undergoing isolated CABG between 1970 and Over this interval they noted a gradual worsening of the patient profile as evidenced by a higher mean age, a greater proportion of female patients, and an increased incidence of diabetes, unstable angina, prior myocardial infarction, three-vessel coronary artery disease, left main coronary artery disease, and LV dysfunction. Despite worsening risk factors, the operative mortality decreased over these twelve years from 1.2 to 0.8%. Multivariate analysis of risk factors revealed that, as in the report of Miller and co-workers [ll], emergency operation and congestive heart failure persisted as significant predictors of mortality. Further analysis demonstrated that two other variables were incremental risk factors throughout the interval-female sex and advanced age; these factors were not significant in the study of Miller and associates [ll]. Left main coronary artery disease lost its statistical significance but two new independent predictors arose-incomplete revascularization and abnormal ECG. Our previous report and the current review of a larger sample indicate that the decline in overall clinical status noted through the 1970s and into the early 1980s has continued [3]. Compared with the CABG '75 group, the CABG '85 cohort demonstrated a significant worsening in the clinical profile as judged by independent predictors of survival including increased age, female sex, severity of coronary artery disease, poor LV function, unstable angina, and incidence of emergency operation. The reasons for these changes appear to be twofold. First, CABG has been shown not only to be an increasingly safe procedure, but also to result in significantly increased long-term survival in a variety of high-risk patient subsets including those with severe angina [13], LV dysfunction [14], left main coronary artery disease [15], and advanced age [16]. As these beneficial survival effects were realized, increasing numbers of patients within these high-risk groups were referred for surgical intervention. Second, a large number of patients who would have been treated surgically in the past decade are now referred for PTCA instead of CABG. Although initially utilized only for single-vessel disease, the indications for balloon angioplasty have now been extended in many centers to include multivessel disease. It has been estimated that up to 20% of the CABG population could be alternatively treated by PTCA [17]. This hypothesis has become reality at our institution. In our experience, PTCA patients are younger and have less coronary artery disease, better LV function, and fewer concomitant medical diseases than their surgical counterparts. The PTCA '85 group closely resembled the CABG '75 group and, as such, would constitute a very low-risk surgical population. The removal of these low-risk patients from the pool of surgical candidates leads to a relative increase in the proportion of high-risk patients undergoing CABG. Conversely, PTCA has also provided an entirely new source of high-risk patients, that is, those with acute evolving infarction. Approximately 5% of patients undergoing PTCA will require emergency surgical intervention for acute ischemia. Although some reports suggested these patients had a low operative risk similar to that for patients having elective CABG [18, 191, the mortality has been reported to be as high as 12% [20, 211. As patients with complex multivessel disease undergo PTCA, the operative mortality of emergency or "salvage'' CABG following failed PTCA may increase further. Despite increased clinical risk, the CABG '85 cohort operated on electively had the same mortality as the patients having elective procedures a decade earlier (see Table 5). We agree with Miller [ll] and Cosgrove [12] and their associates that this is the result of improved surgical technique as well as better preoperative and postoperative management. In contrast, the overall mortality has more than doubled (3% versus 7%) during this period. This increment in operative mortality occurred as a result of an increase in the proportion of patients undergoing high-risk urgent or emergency CABG procedures. The need for emergency CABG has always been associated with a marked increase in operative risk. In the CASS study [7], emergency operation resulted in a sixfold increase in mortality and was one of the most powerful predictors of surgical risk. The multivariate analysis of Miller and associates [ll] demonstrated that emergency operation was the single most powerful predictor of operative death (p < ) through the 1970s and during that time resulted in a mortality twelve times higher than elective revascularization (12% versus 1%). Similar results were.obtained by Cosgrove and coworkers [12] who noted a ninefold increase in mortality. Comparison of institutional mortality rates for "emergency'' revascularization is difficult and fraught with inaccuracy. The definition of emergency or urgent operation changes from institution to institution and will change over time within a given medical center. Our "urgent" population represents a patient cohort that has often been described as an "emergency" subgroup in the past, that is, patients with angina refractory to intravenous administration of nitroglycerin or use of the intraaortic balloon (maximal medical management) and patients with crescendo or rest angina as well as left main coronary artery disease. These patients represent an increasingly greater proportion of the surgical candidates. Over the study interval, there was a threefold increase in the number of patients operated on urgently. This occurred despite a wealth of medications (calciumchannel blockers, long-acting nitrates, intravenous nitroglycerin) and technology (intraaortic balloon, pulmonary artery pressure monitoring) that were unavailable or infrequently utilized in Compared with the CABG '75 group, the CABG '85 patients had a higher incidence of severe coronary artery disease, which placed more myocardium at risk. Despite this, the operative mortality for the urgent operation group (21%) did not change significantly over the period. The mortality,

7 672 The Annals of Thoracic Surgery Vol46 No 6 December 1988 although high, is similar to that reported by others. These patients were at high risk and in quite unstable condition. Five had had a myocardial infarction within 30 days, and 8 of the 14 patients requiring urgent operation had left main coronary artery disease and rest angina or pain refractory to intravenously administered nitroglycerin. This latter subgroup of patients (emergency left main coronary artery disease) had been shown to have an operative mortality of 23% by the CASS group [6]. More recently, Teoh and colleagues [22] reported an operative mortality of 22% in patients with left main coronary disease who underwent emergency revascularization. Our definition of emergency operation is a stringent one; it is based on clinical criteria that indicate an acute need for emergency revascularization-failed PTCA with ongoing infarction or ischemia and/or cardiogenic shock secondary to an evolving myocardial infarction. These are salvage operations performed on patients with ongoing ischemia who more often than not also have profound LV dysfunction. Emergency surgical intervention occurred fourteen times more frequently in 1985 than in 1975, and carried an operative mortality of 36% (5/14). None of the 5 patients with an evolving infarction or failed PTCA who were in hemodynamically stable condition died. All 5 deaths occurred among the 9 patients who were in cardiogenic shock preoperatively. This 56% mortality following emergency CABG for cardiogenic shock is comparable to that in previous reports [ When considered jointly, the urgent and emergency subgroups accounted for 19% of our CABG 85 population and 73% of all deaths in this group. This is in sharp contradistinction to the CASS [6], Stanford [ll], and Cleveland Clinic [12] experiences in which patients having emergency operation accounted for less than 3% of patients overall and for less than 25% of all deaths. If urgent or emergency operations continue to account for an increasing proportion of the patient population undergoing CABG, it is possible that the overall operative mortality will rise further, thereby reflecting the greater operative risk incurred by these patients during CABG. The treatment of coronary artery disease has evolved greatly within the last two decades and remains one of the most dynamic fields in medicine today. An increasingly large proportion of patients with occlusive coronary disease is being referred for PTCA. In general, these are low-risk patients, almost identical to those constituting the learning curve for cardiovascular surgeons in the early 1970s. The subset of patients referred for CABG has gradually evolved into a population with a high incidence of advanced age, severe coronary artery disease, LV dysfunction, and multiple concomitant medical problems. Urgent and emergency procedures continue to increase in frequency and threaten to become the rule rather than the exception. If the clinical status of the surgical cohort continues to deteriorate and emergency operations continue to increase in frequency, it is possible that the overall operative mortality will rise further, thereby reflecting the greater operative risk incurred by these patients during CABG. The resulting raw mortality data must not be taken at face value, but rather should be appropriately analyzed in light of known prognostic factors present within the surgical population. If this is not done, public misconceptions may arise regarding the risk of CABG. Misinterpretation of the mortality data might lead to inappropriate regulatory actions that would result not in safer operation, but in the wrongful exclusion of high-risk patients from the pool of surgical candidates to maintain an acceptable postoperative mortality. 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8 673 Naunheim et a1 Changing Mortality of Revascularization 15. Chaitman BR, Fisher LD, Bourassa MG, et al: Effect of coronary bypass surgery on survival patterns in subsets of patients with left main coronary artery disease (CASS). Am J Cardiol48:765, Gersh BJ, Kronmal RA, Schaff HV, et al: Comparison of coronary artery bypass surgery and medical therapy in patients 65 years of age or older (CASS). N Engl J Med 313:217, Hall D, Gruentzig A: Percutaneous coronary transluminal angioplasty: current procedure and future direction. AJR 142:13, Murphy DA, Craver JM, Jones EL, et al: Surgical revascularization following unsuccessful percutaneous transluminal coronary angioplasty. J Thorac Cardiovasc Surg 84342, Pelletier LC, Pardini A, Renkin J, et al: Myocardial revascularization after failure of percutaneous transluminal coronary angioplasty. J Thorac Cardiovasc Surg 90:265, Parsonnet V, Gielchinsky I, Hochberg MS, et al: Emergency surgery after failed angioplasty (abstract). J Am Coll Cardiol 9:123, Killen DA, Hamaker WR, Reed WA: Coronary artery bypass following percutaneous transluminal coronary angioplasty. Ann Thorac Surg 40:133, Teoh KH, Christakis GT, Weisel RD, et al: Increased risk of urgent revascularization. J Thorac Cardiovasc Surg 93:291, Bardet J, Rigano M, Kahn J, et al: Treatment of postmyocardial infarction angina by intra-aortic balloon pumping and emergency revascularization. J Thorac Cardiovasc Surg 74299, Bolooki H: Indications for use of intra-aortic balloon pump: cardiogenic shock. In Clinical Applications of Intra-Aortic Balloon Pump. Mt. Kisco, NY, Futura, 1977, p DeWood AM, Notske RN, Hensley GR, et al: Intraaortic balloon counterpulsation with or without reperfusion for myocardial infarction shock. Circulation 61:1105, 1980 Discussion DR. NICHOLAS T. KOUCHOUKOS (St. Louis, MO): This excellent presentation documents the important changes in the clinical characteristics of a group of patients undergoing coronary bypass grafting in a recent time interval as compared to those of a group operated on a decade earlier. These changes were associated with a substantial increase in the 30-day mortality. This increase was primarily related to an increase in the percentage of patients undergoing urgent or emergent operation where the mortality remained high, approximately 30%, for these groups in the recent time interval. This subgroup comprised 4% of the patients in 1975 and 18% of the patients in Are the changes in patient characteristics and the resulting increase in mortality unique to the population of patients at the St. Louis University Medical Center? I think not. I have compiled similar data for all patients undergoing isolated coronary artery bypass grafting procedures in two time intervals and in two separate institutions with which I have been affiliated. During this 10-year interval, the mean age of operation increased 10 years, the percentage of patients 70 years or older increased over fivefold, from 5 to 28%, and the percentage of females and the number of patients with diabetes more than doubled. Urgent or emergent operation was performed in less than 1% of the patients in the early time interval, but in 19% of the patients in 1985 and This percentage is identical with that reported by Dr. Naunheim. One percent of the patients in the early time interval had an operation within 30 days of a myocardial infarction. In the current interval this subgroup comprised 25% of the patients having isolated bypass grafting. The percentage of patients with reoperation increased from 1 to 9%. Using univariate and multivariate statistical techniques, a number of studies have shown that all of these variables, with the exception of diabetes, are associated with significantly higher operative mortality rates. Because of the small percentage of patients, less than 1%, who had urgent or emergent surgery (a most important predictor of hospital mortality) in the earlier time interval, the overall mortality rate for that period was unaffected. Although we observed an increase in the mortality for elective surgery from 1.2% in the interval to 2.4% in the interval, the mortality for urgent or emergent procedures was unchanged, approximately 7%. However, as 19% of the patients in the recent time interval underwent urgent or emergent operation, this 7% mortality had a more profound effect on the overall mortality. The data presented by Dr. Naunheim and supported by our own findings will assume increasing importance as we are forced to respond to the reports of federal regulatory agencies that continue to use raw hospital mortality rates, with some adjustments for case mix, but with none up to the present time for severity of illness as the principal indicator of quality of care. Another important finding in Dr. Naunheim s study was the substantial mortality for percutaneous transluminal coronary angioplasty (PTCA) in 1985 among a group of patients who had clinical characteristics similar to the 1975 cohort of patients who underwent coronary bypass grafting. The mortality was 7%, identical to that observed among the 1975 cohort of patients who underwent bypass grafting. This is a much higher mortality rate for PTCA than has been reported from other centers. I have two questions for Dr. Naunheim. How many patients underwent operation and angioplasty in 1975 and 1985? Do the characteristics of the first 150 patients in each of the years evaluated accurately reflect the characteristics of the entire group of patients for that year? Because of the small sample size, it is possible that the mortality observed for the patients undergoing urgent and emergent surgery or angioplasty may not reflect the true incidence for the entire year. DR. LAWRENCE L. MICHAELIS (Chicago, IL): My comments are going to be more philosophical than scientific. Your subject is timely and important to all practicing cardiac surgeons in a day when we seem to be under constant attack from the government, the press, and even some of our own colleagues. I am convinced that the mortality of bypass surgery is indeed increasing nationwide and that it is not due to deteriorating surgical technique or failure to adhere to good principles of myocardial protection. It is only due to patient selection, and in fact, this patient selection is, in many instances, now out of our hands. Cardiologists are more and more aggressive with their indications for angioplasty, and they are less apt to include us in decision making. Similarly, large urban medical centers such as Dr. Naunheim s are seeing more indigent and older patients, as well as those transferred from community hospitals that are unwilling to take on high-risk patients. Today, some of our colleagues are faced with the dilemma of threats to close large and successful programs because their mortality rates are perceived to be excessive by a bureaucracy using outdated statistics that have no relation to patient popula-

9 674 The Annals of Thoracic Surgery Vol46 No 6 December 1988 tion in a particular institution. Should we refuse to operate on desperately ill patients to conform to ignorant and unrealistic expectations of the government or the media? Like Dr. Naunheim and colleagues experience, at Northwestern University the mortality for all patients undergoing bypass surgery has doubled in the last 7 years. During this same time the mean age of our patients, just as Dr. Kouchoukos has mentioned, has increased by a little over 10 years. In fact, though, during this same time the mortality for elective bypass surgery has decreased to the same figure, somewhere between 1 and 2%. I believe now that there is a great danger in quoting low mortality for bypass surgery to the press, to the public, or, God forbid, in a competitive or marketing effort. A layman cannot understand the differences between elective coronary revascularization and the broad spectrum of urgent and high-risk patients being presented to many cardiac surgeons in The public is rightfully confused when newspapers publish higher mortality rates, gathered from Medicare data, that are depicted by naive reporters as scandalous incompetence by our specialty. We must somehow keep our patients informed of the changes going on in coronary revascularization, and, at the same time, keep them unburdened by unfounded expectations. I am personally convinced that a real danger comes from some members of our own specialty who glibly minimize the risk of coronary revascularization in an effort to attract more patients to them or to aggrandize themselves. I applaud the courage of Dr. Naunheim in presenting these honest and realistic data. The excellent reputation of your fine hospital and of your associates adds further credence to your message. I have only one question. In reviewing your manuscript, I noted there was also an increase in untoward neurological events. Did that also correlate with the urgent and emergent patient? Thank you for letting me discuss your fine paper. DR. BERNARD s. GOLDMAN (Toronto, Ont, Canada): I rise to echo and reemphasize some of the points that have already been made in this excellent presentation. I thought it would be of interest to give you some data from Toronto General Hospital, where the health-care resources for cardiac surgery are somewhat more limited, with three adult open-heart units for an over three million local population. Therefore, waiting lists tend to get long and patients undergoing elective procedures tend to be put to the end of the list. The advent of percutaneous transluminal coronary angioplasty (PTCA) at our hospital did not decrease the number of coronary bypass procedures; in fact, the increased number of investigations has increased the number of patients referred for bypass. Of course, as has been stated, it has changed the patient mix, and along with this has been the change in the age of the population. As this is not exactly the Sun Belt, I am sure the increase in patient age is worse in the South and southwestern U.S. The rise in population between 1983 and the year 2000 is anticipated to be 37 to 138% for patients between 65 and 85 years old; by the year 2000 in Canada, an anticipated 17% of the population will be over 65. So this increased age is what we will be seeing in terms of our patient selection. We were interested, therefore, to examine our results with this increasing patient age and found that the presentation of patients over 70 was markedly different from that for patients under 70. There were more females (29% versus 18%). Fewer patients had stable angina. The number of patients who presented in the coronary care unit on intravenous nitroglycerin or with postinfarction ischemia was almost double (32% versus 19%). There was also a higher number of patients over 70 who had left main coronary artery stenosis (19% versus 10%). And, as stated by Dr. Kouchoukos, there were a greater number of patients over 70 undergoing urgent surgery (33% versus 17%). This is reflected in our results which show a lesser degree of revascularization, a higher degree of perioperative infarction, a higher mortality (6.2% versus 2.9%), a higher rate of neurological events (4.4% versus 1.3%), more patients on inotropes, and more patients requiring intraaortic balloon pumping preoperatively or postoperatively (19% versus 11%). My question, therefore, since this has had an impact on us in terms of the intensive care unit and bed stay and has disrupted our elective operative procedure schedule on occasion, is: Are you changing your criteria for patient selection based on this worsening case mix? DR. NAUNHEIM: I would like to thank the discussants for their comments. They have echoed the views of myself and my colleagues at St. Louis University regarding the dangers of public quotations of low mortality. We believe it not only affects neighboring cardiothoraac programs but the practice of cardiothoracic surgery as a whole, and has many more ramifications than perhaps have been recognized in the past. Dr. Kouchoukos asked how many patients undergoing percutaneous transluminal coronary angioplasty (PTCA) came to operation in PTCA was performed on just over 400 patients and 24 of them came to operation, yielding a 6% rate of emergency revascularization. The preoperative risk factors of the 150 angioplasty patients examined in this study did not differ from those in the 400 PTCA patients at large. We did not specifically compare those PTCA patients whp were taken for emergency surgery to the PTCA group at large. Dr. Michaelis, we did not find that the occurrence of neurological events correlated with either urgent or emergency surgery. One of the patients who did have a stroke was an 81- year-old man whose left anterior descending artery occluded during PTCA, and he was rushed to the operating room. He suffered a massive stroke, and was declared brain dead two weeks later. All other strokes occurred in elective cases. Last, Dr. Goldman asked if we had changed our patient selection by altering our criteria for operative intervention. I honestly think that, when the Health Care Finance Administration study was released in 1985, our selection criteria for coronary bypass procedures became more stringent, whether consciously or unconsciously. We have not looked at this specifically; however, I do believe there are people we now turn down for surgery whom we might not have turned down in These are severely ill patients, usually of advanced age, who are in cardiogenic shock or have multiple comorbid factors. We operated on these patients in the past, feeling that operative intervention, though it only yielded a small chance of survival, was indeed their only chance of survival. Those patients are now looked upon with a fairly jaded eye, and I think that our mortality has decreased to 5% in the last two years as a result.