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Ann Thorac Surg 1996;62:16-22
© 1996 The Society of Thoracic Surgeons
Department of Cardiothoracic Surgery, Hahnemann University Hospital, Philadelphia, Pennsylvania
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Abstract |
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 TopFootnotes Abstract IntroductionPatients and MethodsResultsCommentReferences |
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Methods. Over an 8-year period, 474 consecutive patients 80 years of age and greater had coronary artery bypass grafting. The left internal thoracic artery was used in 188 patients (39.7%) (group 1) and saphenous vein grafts only (group 2), in 286 (60.3%). The mean age was 82.6 years (range, 80 to 95 years). There were 312 men (65.8%) and 162 women (34.2%).
Results. Use of the internal thoracic artery as a graft has risen steadily each year, as has the number of patients who are octogenarians. The hospital mortality rate was 7.8%. Patients in group 1 had a mortality rate of 9.0% and patients in group 2, a mortality rate of 7.0%. The mortality rate among survivors at 1 year was 6.7%. Long-term survival was significantly greater in group 1.
Conclusions. On the basis of this study, we conclude that the internal thoracic artery is the bypass graft of choice, especially in regard to long-term mortality, and should not be denied to this high-risk group.
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Introduction |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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The number of cardiac operations in elderly patients has been rising steadily over the past two decades. A number of studies have shown this group of patients to be at higher risk because of the presence of concomitant diseases [1, 2]. The term elderly has been used to describe an increasingly older population. Projections by the Census Bureau [3] estimate a steady increase in the proportion of Americans exceeding the age of 80 years. The internal thoracic artery (ITA) has been shown to be of increased benefit in younger patients undergoing coronary artery bypass grafting (CABG) [4–6]. The assumption has been that ITA grafting in the elderly population is associated with increased morbidity and mortality. The reasons for this are longer time of operation, increased invasiveness of tissue, wide exposure of the pleural space, and greater pulmonary dysfunction. The present study was undertaken to elucidate more fully the degree to which use of the ITA in the elderly affects morbidity and mortality. Two cohorts of patients were studied to demonstrate the effects of ITA grafting on morbidity and mortality compared with saphenous vein grafts (SVGs) alone.
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Patients and Methods |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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. Patients who received an ITA conduit (n = 188, 39.7%), were classified as group 1, and patients who received only SVGs (n = 286, 60.3%), were classified as group 2.
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. The preoperative group profiles were compared and found to be similar. There was a 1.5:1 ratio (312:162) of men to women, and there were slightly more men in the ITA group than in the SVG group (67.6% versus 64.7%). The mean age was comparable between the two groups (81.9 years versus 82.9 years). The risk factors present preoperatively included the following: myocardial infarction (MI), acute (<1 week) and remote (>1 week); congestive heart failure; hypertension; diabetes mellitus; renal dysfunction; peripheral vascular disease; and cerebrovascular disease. No significant differences between the two groups could be demonstrated.
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A total of 16 patients, 6 in group 1 and 10 in group 2, underwent emergency operation. There were 21 patients (11.2%) in group 1 and 18 patients (6.3%) in group 2 who were having redo operations.
All patients were operated on using standard cardiopulmonary bypass techniques. Ascending aortic cannulation, single two-stage or bicaval cannulation, and hypothermia to 25° to 28°C were routinely used. Myocardial protection was generally afforded by antegrade cold blood cardioplegia. Distal bypass grafts were constructed under a single cross-clamp time. All proximal bypass grafts were performed with a single side-biting clamp on the ascending aorta.
Data Collection
All historical and perioperative data were obtained by retrospective review. Hospital charts, catheterization reports, and operative reports were used. Follow-up information was obtained from most patients by telephone interview and for the rest, from records of the personal physicians. Follow-up was complete for 92% of the known survivors.
Statistical Analysis
Data are presented as frequency distributions and simple percentages. Significance was assumed when the p value was less than 0.05. Categoric variables were compared using 
2 analysis. Continuous variables (eg, age) were compared using an unpaired Student's t test, with Bonferroni's correction where applicable. Life-table calculations and cumulative survival were estimated by the Kaplan-Meier method and plotted along with the conditional probability standard error. Comparison of the two study groups was achieved by calculating the Z statistics and referring to tables of the normal distribution.
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Results |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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). The percentage of patients receiving ITA grafts has also increased during this period. During the first year of the study, the frequency of ITA use was less than 5%, but it has increased dramatically to 48% for the last 2 years (Fig 3).
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. The overall LOS during the period of the study was 12.9 days. It ranged from a high of 15.1 days in 1989 to a low of 9.9 days in 1994. Group 1 had an average LOS of 11.4 days and group 2, 13.9 days (p < 0.05).
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Mortality
Hospital mortality was defined as death during the period of hospitalization or within 30 days after operation. There were 37 deaths in 474 patients, for an overall hospital mortality rate of 7.8%. Group 1 had a hospital mortality rate of 9.0% (17/188) compared with 7.0% (20/286) for group 2 (p = 0.056). In both groups, the most common causes of death were myocardial failure (n = 18 patients) and cerebrovascular accidents (CVA) (n = 8 patients) (Table 2). The other causes of death were sepsis (n = 4), renal failure (n = 4), respiratory failure (n = 2), and pulmonary embolism (n = 1).
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). Myocardial infarction was documented on the basis of diagnostic electrocardiographic changes and measured elevation of myocardial enzyme levels. Respiratory failure was defined as ventilatory dependence lasting longer than 48 hours from the time of operation. Acute postoperative renal failure was classified as the requirement of temporary peritoneal dialysis or hemodialysis. Cerebrovascular accident was classified as a fixed neurologic deficit at the time of discharge. Postoperative bleeding was noted as critical only if the patient was returned to the operating room. The most common complication was respiratory failure, followed by CVA and then perioperative MI. The other three complications were less common.
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. Confidence intervals for survival in each group are also included. At 2 years of follow-up and beyond, the risk of dying diminished significantly in the ITA cohort by a factor of 0.5. Survival at 5 years and beyond remained at 80% in group 1 but diminished to 60% in group 2.
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Comment |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Over the 8 years of this study, the incidence of ITA use has increased tenfold, from 4.7% to 48%. This is due to a number of factors. First, confidence in the applicability of this conduit grew with greater experience and improved skills of the surgeons. Second, the number of octogenarians seen for CABG continues to grow, with a greater number of these patients having less than ideal saphenous veins for CABG. This may correlate with advanced age, as saphenous veins were anecdotally noted to be more friable and of poorer quality in the very elderly. The search for alternative conduits to SVGs led us to reexamine use of the ITA in these high-risk patients.
A number of studies have shown that CABG in elderly patients is associated with increased morbidity and mortality compared with younger cohorts [12, 13, 14]. We found this to be true in our older subgroup as well. The hospital mortality rate for the total cohort of 474 patients was 7.8%. During the same period, the mortality rate was only 3.5% in 8,155 patients less than 80 years old undergoing CABG. This finding is similar to findings in other reports on octogenarians having CABG [15–17].
The underlying differences are multifactorial in origin. Elderly patients have a greater incidence of concomitant disease processes. Also, the elderly are referred for operation at a later stage of the disease than younger patients and with more severe symptomatology. In fact, more than 90% of our patients were in New York Heart Association class III or IV preoperatively, a finding consistent with other studies [16, 17]. In addition, an inherent bias may be present among referring physicians because of the often reported increased mortality with advanced age. Early in the evaluation of this cohort population, it was also more likely for octogenarians only in the best physical shape to be referred for operation. As greater numbers of elderly patients were seen with angina, referrals for operation increased. The Society of Thoracic Surgeons database [18] reports an increase in the mean age of CABG patients in each of the last three decades. The average age has increased from 58.5 years to 64 years in just the 10-year period 1980 to 1990. The average age of the patient undergoing CABG at our institution during the time period of this study has increased to 72.3 years.
Importantly, a retrospective examination of the preoperative characteristics of the two groups reveals very little difference between them. An overview of the preoperative risk factors shows that elderly patients do indeed have a plethora of concomitant diseases. However, this should not be a deterrent to their referral for operation. It is tempting to speculate that most of these disease processes have not progressed to end-organ damage; otherwise the patients would not have made it to the ninth decade. Referral of the elderly patient for CABG was a decision that was not lightly made. The incidence of emergency operations in patients less than 80 years old in our institution is 11%. Comparatively, the low incidence of emergency operations in these two groups of patients, 3.2% and 3.5%, respectively, reflects an intense effort to maximally optimize the preoperative state of the patient. A substantial number of patients, 42 (22.3%) in group 1 and 68 (23.8%) in group 2, were seen with symptoms of congestive heart failure. The presence of mild to moderate congestive heart failure preoperatively has been shown not to be a strong predictor of poor outcome [14, 16].
The fact remains that hospital (operative) mortality remains the gold standard by which surgical procedures are deemed successful. Hospital mortality was slightly higher in the ITA group than the SVG group, 9.0% versus 7.0%, but did not reach significance (p > 0.1). We did not note any decrease in mortality rate by year of study; the rate ranged from 6% to 12%. Myocardial failure was the most common cause of death. The Coronary Artery Surgery Study [19] and others have shown convincingly that compromised LV function is a strong independent predictor of operative mortality. Approximately 15% of our patients had severely impaired LV function, and another 45% had moderate impairment of LV function by preoperative ventriculography. Preoperatively, more than 25% of patients in each group had a proven acute MI, and two thirds of the patients had a history of one or more previous MIs. Postoperatively, it was recognized that 4.1% and 4.5% of patients in groups 1 and 2, respectively, had sustained a perioperative MI. The frequency of perioperative MI is comparable to rates reported elsewhere for CABG and is also similar to rates in younger patients [14, 19]. We believe the lower rate of perioperative MI is due to improved techniques for cardiopulmonary bypass, better myocardial preservation techniques, and safer anesthesia management.
Cerebrovascular accident, the second most common cause of hospital mortality, occurred in greater frequency than in younger patients. Five patients in group 1 and 3 patients in group 2 died secondary to a CVA. In all, 10 patients (5.8%) in group 1 and 20 patients (7.5%) in group 2 sustained a CVA. The incidence of CVA has clearly been shown to increase with advancing age after CABG [17, 20]. The incidence of CVA in patients younger than 80 years during this same period was less than 2%. Preoperatively, 40 patients (21.3%) in group 1 and 54 (18.9%) in group 2 were noted to have cerebrovascular disease, defined as one or more neurologic events. This is much higher than in the general group of patients undergoing CABG before the ninth decade of life. Preoperative assessment of carotid artery disease by Doppler should be routinely performed in this elderly group of patients. It is now our policy for elderly patients found to have critical carotid disease to undergo carotid endarterectomy before CABG.
Sepsis was the cause of death in 2 patients in each group. In contrast, sternal infection was rare, less than 2% in both groups, although mortality was very high when it did occur. Williams and colleagues [16] showed sternal wound infection has a positive predictive value for hospital mortality and wrote that they "use the left internal mammary artery only in selected cases where the quality of sternal tissue is good." In our experience, most octogenarians appear to have weak sternums and rather friable tissue but are endowed with good mammary arteries.
Four patients died secondary to renal failure, 1 in the ITA group and 3 in the SVG group. Twelve patients experienced acute renal failure requiring hemodialysis postoperatively. Hence, the mortality rate was 33% in patients requiring hemodialysis postoperatively. The incidence of preoperative renal dysfunction in groups 1 and 2 was 18.1% and 19.9%, respectively. No patient who required long-term hemodialysis preoperatively underwent operation. Several groups [21–23] have shown renal dysfunction to be an important factor in postoperative morbidity and mortality. Our protocol for patients with preoperative renal dysfunction dictates minimal contrast medium use for angiography, hydration, forced diuresis, and renal-dose dopamine hydrochloride.
Only 1 patient in each group died secondary to respiratory failure. Both patients had development of pneumonia, compromising marginal lung function.
The second important criterion by which a surgical procedure is considered successful and is recommended as treatment is acceptable morbidity. No discernible difference in complications was noted between the two groups. One of the greatest concerns noted with ITA use in the past has been respiratory compromise. This is thought to occur secondary to pleural dissection, which may cause increased chest wall pain, postoperative pleural effusion, and a resultant underlying atelectasis. Considerable morbidity was noted secondary to respiratory difficulties. Although ventilatory dependence was slightly greater in the ITA group, 18 patients (10.5%) compared with 25 (9.4%) in the SVG group, no significant difference existed. One might think that opening the pleural space and chest wall dissection would increase postoperative respiratory difficulty, but this was found not to be the case. A separate study in younger patients having CABG at this institution shows no significant delay in extubation in patients having an ITA as a graft (personal communication).
Historical concerns over adequacy of ITA flow seem to be unfounded. Certainly the absence of any increase in perioperative MIs in group 1 is reassuring. In no patient in the SVG group was a mammary artery taken and not used because of poor flows. It has been shown that takedown of single ITA grafts has not been associated with a greater incidence of sternal infections [24, 25]. Our elderly cohort confirms this finding as evidenced by a very low incidence of infection in groups 1 (1.8%) and 2 (1.1%). No patient in either group received bilateral ITA grafts. Tremendous improvement in the patients' symptoms was also noted. Preoperatively, 92.0% of patients in group 1 and 93.4% of patients in group 2 were classified in NYHA class III or IV. Postoperatively a complete reversal was noted, with 90.1% of patients in group 1 and 93.2% of patients in group 2 classified in NYHA class I and II (Table 4).
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The third standard of success for surgeons, and perhaps the one of greatest importance, remains the long-term benefit of such an operation. The actuarial survival rates were calculated for the two groups with follow-up as long as 7 years for those operated on early in the study (Fig 5
). Significance between the two groups is reached at a point beyond the 2-year follow-up. The ITA group continues to show a greater actuarial survival throughout the remaining follow-up period. Survival for the ITA cohort beyond 5 years remains approximately 80%, but the number of patients in this group (n = 11) is too small to derive conclusive clinical significance. Survival for the SVG group mirrors that of other groups reporting on octogenarians. Survival data from the Cleveland Clinic [5] indicated that improvement in survival is conferred by ITA grafting as early as 4 to 5 years postoperatively. The fact that we could note a difference as early as 3 years points to differing conduit characteristics in the very elderly. It is conceivable that the saphenous vein is a poorer conduit in very elderly patients and therefore does not confer protection from early graft closure. Late survival benefit with use of the ITA in the elderly has not been shown by other studies [2, 22, 24]. The incidence of ITA use was fairly low in previous studies, and it remains to be seen whether with increasing use, long-term survival improves. It is inherently obvious that long-term studies in this group of patients (ie, >10 years) is difficult because of natural attrition rates.
It is apparent from this study and others that the incidence of CABG procedures in octogenarians is rising. Substantial quality of life may be restored by surgical intervention, as shown by the improvement in NYHA class in both the ITA group and the SVG group. We conclude from the data presented here that an ITA graft to the left anterior descending coronary artery can be used without fear of greater morbidity or mortality in patients 80 years of age and older. The ITA graft has no increased morbidity than and comparable hospital mortality as the SVG. With others, we tended to assume that use of the ITA graft would cause increased respiratory failure, increased bleeding, more sternal infections, and a longer operation. On the contrary, we found no substantial difference in morbidity with use of the ITA compared with use of the SVG alone. In addition, we observed, with some surprise, that LOS was significantly lower in patients having ITA grafts. The hospital mortalities were similar, and the long-term follow-up showed decreased mortality in patients with the ITA graft. Most notably, the difference in survival is apparent within 2 years of follow-up, much earlier than that observed in younger patients. The ITA was found to be a good-quality vessel in octogenarians, and we are not aware of a single instance of inadequate flow or perioperative MI secondary to decreased flow. We believe that there are many advantages to using the ITA graft and few disadvantages in elderly patients. We therefore have made it our policy to use the ITA graft as much as possible in octogenarians.
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Footnotes |
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Address reprint requests to Dr Morris, Hahnemann University Hospital, Broad and Vine Sts, MS 111, Philadelphia, PA 19102.
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TopFootnotesAbstractIntroductionPatients and MethodsResultsCommentReferences |
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