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Ann Thorac Surg 1998;66:1670-1673
© 1998 The Society of Thoracic Surgeons

Cardiac operations in the elderly: who is at risk?

^a Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa Civic Hospital, Ottawa, Ontario, Canada

Accepted for publication May 23, 1998.

Address reprint requests to Dr Masters, University of Ottawa Heart Institute, 1053 Carling Ave, Ottawa, ON, Canada K1Y-4E9
e-mail: (rmasters{at}heartinst.on.ca)

	Abstract

Top Abstract Introduction Patients and methods Results Comment Appendix 1 References

 
Background. With the growing number of elderly patients presenting for cardiac operations we analyzed their early survival data to determine whether any preoperative variables might be indicative of increased risk.

Methods. From 1990 to 1995, 436 consecutive patients who were 75 years old or older had either coronary artery bypass, valve replacement(s), or a combination of these. A total of 34 preoperative variables were assessed for their effect on hospital survival by using univariate and multivariable analysis.

Results. There were 266 men and 170 women, with 292 patients being 75 to 80 years old and 144 patients being older than 80 years. Coronary artery bypass was performed in 242 patients, valve replacement was performed in 93 patients, and a combination of these in 101 patients. The operation was considered elective in 202 patients, urgent in 209, and emergent in 25 patients of whom 21 were in cardiogenic shock. Overall there were 61 hospital deaths (13.9%). The most common cause of death, low cardiac output syndrome, occurred in 34 patients of whom 26 suffered a perioperative myocardial infarction. Stroke was the cause of death in eight and multiple organ failure accounted for nine deaths. In the univariate analysis, variables that influenced survival included heart failure (p = 0.004), pulmonary edema (p = 0.004), cardiomegaly (p = 0.02), elevated serum creatinine (p = 0.009), surgical priority (p = 0.002), and cardiogenic shock (p = 0.002). In the multivariable analysis there were three independent determinants of hospital survival: cardiomegaly (odds ratio, 1.8:1) serum creatinine level higher than 150 µmol/L (odds ratio, 5.5:1) and emergency procedure (odds ratio, 2.5:1).

Conclusions. Although cardiac operations can be performed safely in many elderly patients, we identified several factors that might help both in case selection and in perioperative decisions.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Appendix 1 References

 
As the average age of the general population increases, a growing number of elderly patients are presenting for cardiac operations. In Canada the proportion of the population that was 70 to 80 years of age increased from 3.7% in 1961 to 5.2% in 1991. In the United States, approximately 1.8% of patients undergoing coronary artery bypass before 1988 were older than 80 years; this amount has doubled since then. Although hospital mortality rates have decreased with improved standards of care, patients older than 70 years are still at increased risk. We analyzed our surgical results with elderly patients at the University of Ottawa Heart Institute to determine which preoperative variables might be indicative of an increased risk of hospital death in these patients. This information might influence both case selection and the perioperative care.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Appendix 1 References

 
We reviewed retrospectively the charts of 436 consecutive patients who were 75 years old or older at the time of cardiac operation at the University of Ottawa Heart Institute between July 1990 and October 1995 inclusive. Included were patients who had coronary artery bypass grafting (CABG), single or multiple valve replacement(s), or any combination of these procedures. A total of 34 preoperative variables was defined (Appendix 1). For patients in whom the variable was not recorded in the chart it was presumed not to be present. Patients having first-time operations as well as those having reoperative procedures were included. Heart failure was defined by the New York Heart Association functional classification, and angina was graded using the Canadian Cardiovascular Society criteria. The priority for operation was defined as elective, urgent, or emergent. Elective patients were waiting at home and were admitted for the operation. Urgent and emergent patients were unstable and could not be discharged to await the operation. Patients whose status was urgent required an operation on the same admission, whereas patients whose status was emergent required an operation as soon as possible.

The operative procedure included median sternotomy and cardiopulmonary bypass in all cases. Myocardial protection consisted of moderate hypothermia, topical cooling with saline solution, and cold crystalloid cardioplegia administered in an antegrade fashion.

Hospital death was defined as death in the hospital at any time during the postoperative stay. Univariate analyses were performed using the ² statistic to test the hypothesis that each variable was associated with hospital death. Logistic regression analysis was used define the variables that were independent determinants of hospital death. A p value of less than 0.05 was considered statistically significant.

	Results

Top Abstract Introduction Patients and methods Results Comment Appendix 1 References

 
The mean age of the patients was 78.1 years (range, 75 to 91 years) with 266 men and 144 women. For 90% of patients (395) this was their first operation, and 56% (242) of patients had isolated CABG. In 234 patients (54%) their condition was considered either urgent (48%) or emergent (6%). Of the 25 patients requiring emergency operation, 21 (84%) were in cardiogenic shock.

Hospital death occurred in 61 patients (13.9%), and autopsy was performed in 33 of them (54%). The most common cause of death was low cardiac output syndrome in 56% (34 of 61) of which acute myocardial infarction was present in 76% (26 of 34). Other causes of death were multiple organ failure in 9 patients, stroke in 8, hemorrhage in 5, arrhythmia in 3, respiratory failure in 1, and aortic dissection in 1. Of the 8 patients who had a stroke, 3 were noted to have an atherosclerotic aorta intraoperatively. Of the 3 patients with bleeding, 1 had a ruptured pulmonary artery from a Swan-Ganz catheter, 1 had atrioventricular disruption after mitral valve replacement, and 1 had dehiscence of a patch after repair of an acute ventricular septal defect.

Variables that were not statistically significant by univariate analysis included age group, gender, history of hypertension, neurovascular history, previous myocardial infarction, previous cardiac operation, angina class, history of heart failure, unstable angina, pulmonary edema on physical examination, left ventricular function, left ventricular end-diastolic pressure, extent of the coronary disease, presence of left main involvement, and the operative procedure (Table 1).

By multivariate analysis there were three independent determinants of hospital death in these patients, namely, cardiomegaly on chest x-radiation (odds ratio, 1.81; confidence limits 1.05, 3.12), serum creatinine level of 150 µmol/L or higher (odds ratio, 5.51; confidence limits 2.17, 14.28), and emergency operation (odds ratio, 2.50; confidence limits 1.37, 4.54).

	Comment

Top Abstract Introduction Patients and methods Results Comment Appendix 1 References

 
At the University of Ottawa Heart Institute the number of elderly patients presenting for heart operations has increased. In 1990, patients 70 years of age or older comprised 18.9% of our surgical caseload, whereas in 1995 the patients in this age group comprised 28.6% of our cases (p < 0.001). Similarly in an analysis of Medicare data, Peterson and associates [1] found that the use of coronary artery bypass in elderly patients in the United States increased by 67% between 1987 and 1990.

We identified several variables that, by univariate and multivariate analyses, were indicative of an increased risk for older patients undergoing heart operations. Evidence of poor ventricular function (heart failure by history or physical examination or roentgenogram evidence of either cardiomegaly or pulmonary edema), acute cardiac decompensation (emergency operation or cardiogenic shock), or an objective marker of end-organ dysfunction (elevated serum creatinine level) identified patients at increased risk, by univariate analysis. By multivariate analysis, one variable from each of these three groups (cardiomegaly, emergency operation, and elevated creatinine level) was identified as an independent determinant of hospital death.

Numerous previous studies have analyzed the early results of cardiac operations in the elderly. Illustrating the constraints of the current research in this area of cardiac surgery, most of these studies are small with few containing more than 150 patients for statistical analysis. Similiarly, the number of patient variables that were assessed is often small and the statistical methods used are not consistent. In many cases multivariable analysis was not done.

Evidence of poor ventricular function has been identified in several studies to be predictive of increased risk of early death. In a multivariate analysis of 14 variables in 597 patients who were older than 70 years, Montague and colleagues [2] found that a left ventricular ejection fraction of less than 0.40 was associated with increased early mortality. In that study there was an approximate tenfold increase in mortality rate with left ventricular dysfunction. Several studies have found that poor functional class, as a measure of severe ventricular dysfunction, was a determinant of increased early death. The largest of these, a study of 24,461 patients who were 80 years old or older, found that in the presence of congestive heart failure the odds ratio for early death was 1.77 to 1 [1]. This finding was confirmed by smaller studies showing that patients with New York Heart Association class IV had an increased risk of early death [3–5]. In a univariate analysis of the surgical results in 121 elderly patients, Cane and associates [6] found that an elevated left ventricular end-diastolic pressure was a determinant of both early and late death. Of particular importance in patients with poor ventricular function is myocardial protection. Although the first half of the 10-year study by Cane and associates [6] was performed with crystalloid cardioplegia and the second half used blood cardiolegia, the year of operation was not a determinant of survival. In the present study, cold crystalloid cardiolegia delivered antegrade was routinely used in all cases. Whether alternative techniques of cardioplegia should be used in elderly patients with ventricular dysfunction remains an important but unanswered question. With earlier referral for operation, those patients might have had preserved ventricular function.

The urgency of the surgical procedure has been demonstrated consistently to be a risk factor for early death in elderly patients [2, 3, 7]. Montague and associates [2] found that the hospital mortality rate was 2.2% for elective or urgent surgical procedures but increased to 23.1% for emergency operation. In a multivariable analysis of 121 patients who were 70 years old or older, Edwards and associates [3] found the operative mortality rate to be 2.9% for elective procedures, 8.6% for urgent operations, and 22.2% for emergency operations. In a study of 100 elderly patients Edmunds and colleagues [7] also identified emergency operations as a risk factor for early death. Despite the possibility of selection bias, our results clearly demonstrate an increased risk for elderly patients undergoing operation on an emergency basis. Earlier surgical referral might obviate the need for emergency operation in many cases; however, only approximately 6% of cases in the present study were emergent. As in patients with left ventricular dysfunction, the efficacy of alternative techniques of myocardial protection in these patients needs to be evaluated in patients requiring emergency operation.

Preoperative renal dysfunction has been identified previously as a risk factor for cardiac operations in the elderly. In a review by Peterson and associates [1] a history of chronic renal disease was an independent determinant of hospital survival with an odds ratio of 2.42 to 1. In a multivariable analysis of 300 elderly patients, Williams and colleagues [8] identified a preoperative serum creatinine level of greater than 2.0 mg/dL as an independent determinant of hospital survival. Finally, two smaller studies [6, 9] of 60 and 121 elderly patients identified serum creatinine level of greater than 120 µmol/L and history of chronic renal disease, respectively, to be associated with an increased early death using univariate analysis. Renal dysfunction was a powerful determinant of increased risk of hospital death in the present study, with an odds ratio of 5.5 to 1. More than just a marker of intrinsic renal disease however, renal dysfunction is indicative of generalized end-organ dysfunction and as such is an objective marker of patients at risk.

Only by detailed analysis of surgical results can we begin to understand the risks and benefits of a given procedure. Although prospective, randomized studies are always preferable, they are unlikely in many areas of research. In the present study we identified three variables that highlight the elderly patient at risk for cardiac operation. Efforts must also be made to reduce the risks in these patients and to determine the long-term impact of cardiac operations in the elderly.

	Appendix 1

Top Abstract Introduction Patients and methods Results Comment Appendix 1 References

 
Demographic information collected included name, age, gender, height (cm), weight (kg), and body surface area.

Status on admission (history): angina (stable or unstable), angina class (Canadian Cardiovascular Society classification), acute myocardial infarction (less than 30 days before admission or 30 days or more before admission), heart failure (New York Heart Association classification), acute pulmonary edema, syncope, presyncope, or dizziness.

Historical information collected: diabetes (insulin or noninsulin dependent), chronic lung disease or asthma, hypertension (treated with medication), neurovascular disease (including transient ischemic attack, stroke, or carotid endarterectomy), peripheral vascular disease (including claudication or previous surgery), and previous cardiac operation (including valve repair, valve replacement, coronary artery bypass grafting, or a combination).

Physical examination collected information on: pulmonary edema, heart failure, and bruits (carotid or femoral).

Investigations done: electrocardiogram (myocardial infarction, left ventricular hypertrophy), chest x-radiograph (cardiomegaly, pulmonary edema), blood tests (hematocrit, creatinine), angiography (left ventricular end-diastolic pressure, coronary arteries with more than 50% stenosis, or left main involvement more than 50%), and echocardiogram (aortic valve area, mitral valve area, left ventricular function).

Type of operation: urgency status (elective [admitted specifically for operation], urgent [in hospital and operation during same admission], or emergent [in hospital and operation as soon as possible]), cardiogenic shock, procedure (coronary artery bypass grafting [number, site, conduit], valve replacement [site, size, brand], or combination [specify]).

Outcome data collected: hospital survival and cause of death (autopsy or clinical diagnosis).

	References

Top Abstract Introduction Patients and methods Results Comment Appendix 1 References

 

1. Peterson E.D., Cowper P.A., Jollis J.G., et al. Outcomes of coronary artery bypass graft surgery in 24461 patients aged 80 years or older. Circulation 1995;92(Suppl 2):85-91.[Abstract/Free Full Text]
2. Montague N.T., Kouchoukos N.T., Wilson T.A.S., et al. Morbidity and mortality of coronary bypass grafting in patients 70 years of age and older. Ann Thorac Surg 1985;39:552-557.[Abstract]
3. Edwards F.H., Taylor A.J., Thompson L., et al. Current status of coronary artery operation in septuagenarians. Ann Thorac Surg 1991;52:265-269.[Abstract]
4. Ennabli K., Pelletier L.C. Morbidity and mortality of coronary artery surgery after the age of 70 years. Ann Thorac Surg 1986;42:197-200.[Abstract]
5. Pifarre R. Open heart operations in the elderly: changing risk parameters. Ann Thorac Surg 1993;56:S71-S73.
6. Cane M.E., Chen C., Bailey B.M., et al. CABG in octogenarians: early and late events and actuarial survival in comparison with a matched population. Ann Thorac Surg 1995;60:1033-1037.[Abstract/Free Full Text]
7. Edmunds L.H., Stephenson L.W., Edie R.N., Radcliffe M.B. Open heart surgery in octogenarians. N Engl J Med 1988;319:131-136.[Abstract]
8. Williams D.B., Carillo R.G., Traad E.A., et al. Determinants of operative mortality in octogenarians undergoing coronary bypass. Ann Thorac Surg 1995;50:1038-1043.
9. Deleuze P.H., Lorsance D.Y., Besnainov F., et al. Severe aortic stenosis in octogenarians: is operation an acceptable alternative?. Ann Thorac Surg 1990;50:226-229.[Abstract]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Gyaandeo S. Maharajh Roy G. Masters Wilbert J. Keon Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Maharajh, G. S. Articles by Keon, W. J. Search for Related Content PubMed PubMed Citation Articles by Maharajh, G. S. Articles by Keon, W. J.