Infrarenal Abdominal AorticAneurysm - NCBI

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Dec 8, 1980 - Whittemore AD, Clowes AW, Hechtman HB, Mannick JA. Aortic aneurysm repair: reduced operative mortality asso- ciated with maintenance of ...

Infrarenal Abdominal Aortic Aneurysm Factors Influencing SurvivalAfter Operation Performed over a 25-Year Period E. STANLEY CRAWFORD, M.D., SALWA A. SALEH, M.D., JULIUS W. BABB 111, M.D., DONALD H. GLAESER, D.Sc., PATRICK S. VACCARO, M.D., ABRAHAM SILVERS, PH.D.

This report is concerned with the factors influencing survival in 920 consecutive patients submitted to operation for infrarenal abdominal aortic aneurysm during the past 25 years. Rupture had occurred in 60 patients (6.5%) and survival was 77%, which did not vary during the period of study. Of the 860 patients (93.5%) treated for nonrupture, 819 (95%) survived operation. The mortality rate in this group varied from 18%, in the earlier period, to 1.43%, in recent years. Risk factors including heart disease, hypertension, and advanced age accounted for 95% of the deaths that occurred within 30 days however, the mortality rate in patients with these problems decreased from 19.2% to 1.9% during the period of study although the average number of patients treated each year with these risk factors increased tenfold. Improvements in operative techniques and experience were responsible for decreasing mortality up to about 1971. Subsequent decrease in mortality was due more to improvements in anesthesia, monitoring, and other supportive measures during operation and the early recovery period. Complete survival information was obtained in 816 (99.6%) patients, 191 of whom had been treated for periods over 15 years, permitting establishment of life tables subject to analysis. Factors influencing long-term survival were associated disease and age at time of operation. Survival in percentage in patients without associated heart disease or hypertension for 5, 10, and 15 years was 84, 49, and 21; with heart disease, it was 54, 34, and 17. The median age of patients in the series was 65.5 years and survival at above intervals according to quartile was '60: 71, 53, and 24; 60 < age ' 71: 66, 38, and 18; >71: 43, 13, and 11.

INFRARENAL ABDOMINAL AORTIC aneurysms long

have been known to be serious lesions that ultimately lead to death by rupture, in most cases. The studies of Estes and Wright and their associates showed that death occurred at unpredictable times or without warning in about half the patients within a year of diagnoPresented at the Annual Meeting of the Southern Surgical Association, December 8-10, 1980, The Breakers, Palm Beach, Florida. Supported in part by the Joseph W. Moore Cardiovascular Research Fund and the Pauline Sterne Wolf Memorial Home Fund. Reprint requests: E. Stanley Crawford, M.D., 1200 Moursund Avenue, Houston, Texas 77030. Submitted for publication: January 7, 1981.

From the Departments of Surgery, Anesthesiology, and Medicine, Baylor College of Medicine and The Methodist Hospital, Houston, Texas

sis, in 91% within 5 years, and in all patients within eight years.5'12 These findings have since been verified by others.6'8 With the successful application of graft replacement in a patient with abdominal aortic aneurysm, by DuBost and associates, in 1951, a method of treatment became available for this disease.4 The effectiveness of this form of therapy has been verified by numerous reports in subsequent years, and these have shown steady decline in operative mortality rate from iftcreasing experience, refinements in technique, and improvements in general supportive measures.3'7'9-11 In fact, the operative mortality rate has been reported to have been reduced to less than 1%, and the ten-year survival rate increased from none with medical treatment to 30% with graft replacement, despite the advanced age of some patients.3'10'11 This report is concerned with a study of the senior author's experience during the last 25 of the 29 years during which time this method of treatment was available and is directed toward the factors which have reduced the 30day mortality rate from 18%, in earlier years, to 1.43%, during the past two years. Moreover, the interval between operation and follow-up in 191 patients was over 15 years, permitting establishment of a life table which was subject to multivariate analysis. Method of Study All patients treated by graft replacement between August 1, 1955, and October 1, 1980, were studied retrospectively. An entry form listing pertinent data (138 items) was constructed and completed from vari-

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was nearly two years. Division of the latter five-year period into three- and two-year periods was due both to a difference in clinical material occurring in these intervals and to changes in supportive therapy instituted at the end of the first three years. Statistical analysis of these data were performed when applicable for all periods of equal length. A test for linear trends in proportions as developed by Armitage was applied to the data that were organized into contingency tables.

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regarding the first 30 days of from personal hospital and office records. Follow-up information was obtained during the period January 1, 1980, to November 1, 1980, from personal records, questionaires, and telephone calls with family doctors, patients, and relatives, and from death certificates provided by the Bureaus of Vital Statistics of the states in which the patients died in the follow-up period in 816 patients who initially survived operation. The data was transcribed from the recording form into a database management system implemented in Standard MUMPS (ANSI XlI. 1- 1977).1 This system runs on a Digital Equipment Corporation PDP-1 1/60 with 500MBytes of disk storage. Individual data items were checked for validity immediately upon entry. Checks included numeric ranges, code selections, etc. Consistency checking was performed on groups of data items which were known to be mutually dependent (e.g., progression of dates of birth, operation, discharge, follow-up or death, etc). A data analysis package integrated with the data management system permitted a variety of standard descriptive statistics to be calculated and summary data to be displayed in both tabular and graphic form. Preliminary results were used in conjunction with the clinical intuition of the senior author to generate testable hypotheses. Kaplan-Meier survival curves were obtained for various subsets of patients to determine the effect of several variables on survival. A log rank test was used to determine significant differences between the curves. The nature of the clinical material, method, and results of treatment were analyzed according to six periods of treatment, five years each except the last two. The duration of the first of these, or the fifth period, was three years and the last

ous sources. Information treatment was obtained

Clinical Material Graft replacement was performed in 920 patients during the time of this study, which extended slightly over 25 years. Operation in 60 patients (6.5%) was for rupture. The survival rate in this group was 77%, and did not vary appreciably with the period of treatment. Most of the deaths occurred in patients admitted to the hospital in profound shock, and many of them required extreme forms of resuscitation including external cardiac massage, tracheal intubation, and aortic cross clamping through incisions made without anesthesia. The aneurysm in the remaining 860 patients (93.5%) had not ruptured prior to operation. The latter cases form the basis of this study, since the objectives were to determine the influences of therapy on operative mortality, prevention of rupture, and long-term survival in patients with unruptured aneurysms, and not of results in treatment of terminal disease as was present in the former patients. There were 123 women (14%) and 737 men (86%) in the series of patients with unruptured infrarenal abdominal aortic aneurysms (Fig. 1). The mean ages were not significantly different between the two sexes. The median age in the entire group was 65.5 years (range: 15-89 years), with most being in the sixth and seventh decades of life (Fig. 2). Of these 860 patients, 390 had no symptoms relating to the aneurysm, 141 had intermittent claudication, 198 had abdominal, flank, or back pain, and 131 patients had both pain and tenderness in the region of aneurysm (Fig. 3). Associated disease was common, with the most frequent being arteriosclerotic heart disease, hypertension, and other arteriosclerotic lesions, such as distant aneurysm and arterial occlusions, which were present in 723 patients (84%). The most serious associated disease was arteriosclerotic heart disease, which was present in 492 (57%) patients, because it accounted for nearly 50% of the operative deaths (Fig. 4). Other important risk factors were hypertension and advanced age. Two of these three factors, i.e., heart disease and old age, occurred in 648 (75%) patients, and 95% of the operative deaths occurred in this group (Fig. 5). A most important characteristic of the entire patient population was

Vol. 193

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ABDOMINAL AORTIC ANEURYSM

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AGE IN YEARS that the average number of patients treated each year with these risk factors increased tenfold during the period of study. Although accounting for only 5% of the operative mortality rate, other associated conditions presenting problems of treatment by increasing the risk of operative complications were diabetes, chronic pulmonary insufficiency, chronic renal insufficiency, blood dyscrasia, peptic ulcer, hiatus hernia, gallstones, diverticulitis, and rarely, intestinal cancer. The technical difficulties of therapy increased with each period of treatment both because of increase in incidence of these associated conditions and because of an increasing number of patients who underwent operation who

had had previous attempts at removal but in whom operation had been abandoned due to location, size, and extent of the aneurysm, presence of troublesome adhesions or adherence of aneurysm to adjacent structures, entry into bowel, presence of associated large bowel lesions, and horseshoe or pancake kidneys. In fact, 10% of the patients treated during the last two-year period were of the latter type. Treatment Treatment of nonruptured infrarenal abdominal aortic aneurysm in this series was by graft replacement.

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CRAWFORD AND OTHERS

Ann. Surg. * June 1981

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