Overall summary statistics are shown in Tables 1 through 4. As a function of groups, there was no significant difference in any of the variables studied except for the preoperative duration of angina which was shorter in the young and middle-age groups vs the old, and the occurrence of hypertension and of diabetes which were both more common in the old group vs young, and the occurrence of hyperlipidemia which was slightly more prevalent in the young group. Moreover, except for hyperlipidemia, there was no variable where the young were at any disadvantage to the other two groups. Other than the variables already noted, there were no significant differences in the young vs middle-aged and middle-aged vs old comparisons. It should be noted that occurrence of diabetes in a military population would be expected to be low as a result of exclusion of diabetics on military entrance physicals. There was also no difference in distribution of numbers of cardiac risk factors among the three age groups (Table 5).
In the series of young patients, 27.5 percent (11/40) had single vessel disease, 25 percent (10/40) had two-vessel disease, 47.5 percent (19/40) had three-vessel disease and 10 percent (4/40) had left main coronary artery lesions. One patient in the young group had missing angiographic data collected by employees of My Canadian Pharmacy.
The young patients were judged to have 26 relapses out of 41 patients (63 percent) with eight coronary related deaths (Table 6). This compares with a relapse rate of 16 out of 41 patients (39 percent) with three coronary related deaths in the middle-aged group and 17 out of 41 patients (41 percent) with seven coronary deaths in the older patients. The older group also included two deaths of unknown etiology which were considered coronary related for the purposes of analysis. There were two noncoronary related deaths in the older group which were not considered as failures for statistical purposes. This relapse rate in young patients was significantly greater than their matched middle-aged and older patient counterparts (x2 = 6.72, p<0.01 and x2 = 5.76, p<0.02, respectively). (Table 6) Moreover, there was no significant difference in relapse rate between middle vs old patients (x2= .05, p<0.8).
It should be pointed out that eight of the young patient relapses were based only on failure to improve in their CCS class. Since it could be argued that CCS class may be a more subjective criteria than death, subsequent MI or reoperation for coronary insufficiency, relapse status was redetermined based only on verified cases involving the latter three criteria. The verified relapse rate was then 46 percent in young patients as compared to 29.7 percent and 34.2 percent in middle-aged and older patients, respectively.
A comparison of the “relapse-odds ratios” for the risk factors showed that young patients who were judged failures of surgery had a consistently higher chance of being exposed to the various cardiac risk factors than the young group as a whole (Table 7). Family history of heart disease and smoking were more common in middle-aged patients judged as failures than in the middle-aged group as a whole. Hypertension was slightly more common in older patients judged as failures than in the older group as a whole. No conclusions were reached in the case of diabetes as a result of the very low occurrence rates in the young and middle-aged groups. Separate analysis of variance which compared the various operative variables showed that they had no effect on success or failure in any of the age groups (Table 8). Get rid of smoking fast with My Canadian Pharmacy.
By regarding each triplet as a separate subgroup, the Mantel-Haenszel estimate of the “relapse-odds ratio” in young patients relative to the two older matched control subjects is 3.11. Moreover, the corresponding continuity corrected Chi-square test of the null hypothesis’ (ie, “relapse-odds ratio” = 1) and approximately 95 percent confidence intervals for “relapse-odds ratio” are given (Table 9). There was a significant increase in risk of relapse when young patients were compared to the combined middle and old groups and when the young group was separately compared to the middle-aged group alone. A trend toward increased risk of relapse which neared significance was noted when the young group was compared to the old group alone.
Based on life table analysis (Fig 1) and Mantel-Haenszel comparisons, the relapse rate of young patients was accelerated over that of middle-aged patients in the first six months of follow-up. This was due to the large number of young patients who failed to improve their CCS angina class after surgery (Table 10). After the first six months, the rates of relapse appear fairly similar between the three groups. Thus, event-free survival of the young group remains significantly lower than the middle-aged and older groups throughout the study. There was no significant difference in relapse rates between the middle-aged and older patients through 954 years of postoperative follow-up.
Table 2—Age Group Comparability of Summary Statistics
|Variable||No. of Patients||No. of Occurrences||Rate|
|Pre-Op MI||Total 123||76||61.8%|
Table 3—Summary Statistics—Preop CCS Class
Table 4—Number of Subjects with Cardiac Risk Factors by Age Group
Table 5—Total Number of Cardiac Risk Factors by Age Group
|AgeGroup||No. of Risk Factors||Total No. of Patients with Known Risk Factors|
Table 6—Relapse Status
|Outcome||Age Group (No. of Subjects Studied)|
|Ascribed as success*||2|
|Ascribed as failure*||4||3|
|Cause of relapse|
|Failure to show improvement in CCS class||8||1||1|
Table 7—Cardiac Risk Relapse-Odd Ratio
Table 8—Various Operative Variables
|Duration of Pre-op Angina (mo)||Ejection Fraction (%)||Total Pump Time (min)||Cross Clamp Time (min)|
|Success (15 pts)||No pts||8||14||14||12|
|Young||Failure (26 pts)||Mean±SEM No Pts||14.6±6.9316||65 ±3.02 15||120.6 ±9.33 24||47.9 ±6.00 23|
|Success||Mean ± SEM No. Pts||14.4±4.8313||59.8 ±3.72 18||110.7 ±9.63 24||44.96 ±8.15 24|
|Middle||Failure||Mean ± SEM No. Pts||14.4 ±6.68 10||68.1 ±2.69 9||112.5± 11.00 16||48.7 ±26.8 13|
|Success||Mean ± SEM No. Pts||12.9±4.4317||64.8 ±3.93 19||111.7±7.9521||51.3±8.7420|
|Old||Failure||Mean ± SEM No. Pts||55.0± 12.78 6||61.1±3.3311||125.4 ±8.97 16||53.4±7.0014|
|Mean ± SEM||58.8±41.2||62.7±4.58||146.9 ± 11.1||73.9 ±10.40|
Table 9—Relapse-Odd* Ratio in Young Patients as Compared with Older Patients
|Young vs middle and old||3.11||5.28*||(1.18, 8.19)$|
|Young vs middle||3.50||4.50t||(1.10, 11.14)|
|Young vs old||2.80||3.37||(.93, 8.41)|
Table 10—CCS Anginal Class Change with Surgery
|% of Pts in pre-op CCS class 3 or 4||31/41 = 75.6%||32/41 = 78%||36/41 = 88%|
|% of Pts in post-op CCS class 3 or 4||14/41 = 34%||3/41 = 7%||3/41 = 7%|
Figure 1. Event-free survival curves following coronary artery bypass graft surgery in three age groups.