Impact of coronary artery bypass grafting in elderly patients

1. PhD Faculty of Medicine of University of Sao Paulo, Faculty Anhanguera of Rio Grande, Associação de Caridade da Santa Casa do Rio Grande, Rio Grande do Sul, Brazil. 2. PhD Faculty of Medicine of University of Campinas, Faculty Anhanguera of Campinas, São Paulo, Brazil. 3. PhD – Federal University of Sao Paulo, Faculty Anhanguera of Santo Andre I, São Paulo, Brazil. 4. PhD Faculty Anhanguera of Santo Andre III, University of Mogi das Cruzes, São Paulo, Brazil. 5. Student of Physicaltherapist of Faculty Anhanguera of Rio Grande, Rio Grande do Sul, Brazil. 6. PhD in Cardiology (Faculty of Medicine of University of Sao Paulo), Faculty of Medicine of Federal University of Rio Grande, Rio Grande do Sul, Brazil. 7. Cardiovascular surgeon of Associação de Caridade da Santa Casa do Rio Grande, Rio Grande do Sul, Brazil. Work carried out at Hospital de Cardiologia Doutor Pedro Bertoni da Associação de Caridade da Santa Casa do Rio Grande, Rio Grande, RS, Brasil.


INTRODUCTION
The growth of the elderly population, in absolute and relative numbers, is a worldwide phenomenon and is occurring at an unprecedented level.Currently, one in ten people aged 60 or older.In year 2050, it is estimated that the ratio will be one to five in the world, and one to three in developed countries.In Brazil, life expectancy has increased more than ten years (62.57years to 73.17 years) and it is estimated that in 2050, the Brazilian population over 15% of people have 70 years or older [1].
Advanced age is a risk factor for development of coronary artery disease (CAD), diabetes mellitus, hypertension, dyslipidemia, smoking, obesity and family history of CAD.Elderly population has greater prevalence of CAD, and more inclinable to major coronary procedures as coronary artery bypass surgery (CABG).Additionally, cardiovascular disease is the major factor contributing to death, especially in elderly [2][3][4].
CABG is a safe procedure performed around the world with low rates of mortality and morbidity in the general population.The number of octogenarians undergoing CABG increased from 0.13%, in 1986, to 3.5%, in 2001, at the Heart Institute of the Clinical Hospital of the Faculty of Medicine, University of São Paulo, the last 16 years (1986-2001) [5].Thus, recent studies demonstrate the concern of evaluating the outcomes of CABG in elderly patients and comparison with younger individuals to verify the risks to which the elderly are more vulnerable because they are considered high risk patients for this surgery [6,7].
Another important fact is that in the last decade, there have been many changes in surgical techniques, such as the advent of minimally invasive surgery, off-pump CABG, and new devices.Thus, the indication of CABG for elderly patients is increasing because it provides better survival and quality of life [8][9][10][11][12].
The aim of this study was to analyze the outcomes of CABG in patients aged 65 years or older compared with younger patients (<65 years) at a regional reference hospital in Southern Brazil.

METHODS
The project was approved by the Research Ethics Committee of the Hospital Associação de Caridade Santa Casa Rio Grande (RS, Brazil) under protocol number 001/2011.This is a prospective study in which all patients who consecutively underwent CABG alone between 1st December 2010 to 31 th July 2012 were analyzed at the Cardiology Hospital Doutor Pedro Bertoni of the Associação de Caridade Santa Casa Rio Grande (RS / Brazil).Patients undergoing CABG or associated with other cardiac surgery were excluded from the study.We included patients who needed surgery elective and urgent or emergency according to the criteria of the American Heart Association and the American College of Cardiology.Patients were divided into two groups, the group of elderly (GE) consisted of patients aged greater than 65 years and the adult group (GA) with patients under the age of 65.Data were collected daily directly from medical records and interviews with patients since its admission to discharge through a pre-structured form.All patients were elucidated on the research and signed an informed consent form.
The variables collected from the medical records and through interviews with patients were: sex, age, weight, height, race, comorbidities, prior CABG, prior coronary angiography, angioplasty surgery, sedentary lifestyle, smoking, alcohol consumption, number of grafts, time CPB, aortic clamping time, time of submission to mechanical ventilation (MV), length of stay in the Intensive Care Unit (ICU) and in the ward, postoperative complications and progression to hospital discharge or death.
The data were analyzed with the Statistical Package for Social Science (SPSS, version 13.0, Inc., Chicago, IL, USA).Continuous variables were expressed as means and standard deviations (SD), while categorical variables by proportions.Normality was checked using the Kolmogorov-Smirnov test.In the statistical analysis we used the Student t test to compare the means, and the chi-square or Fisher exact test to compare proportions.To determine which factors independently influence the development outcomes of the study was analyzed using multivariate logistic regression "stepwise forward".To verify the correlation between risk factors preoperative, intraoperative variables, postoperative variables and mortality was used the Spearman test.In all analyzes were considered significant when P <0.05.

RESULTS
During the study period, 253 consecutive patients submitted isolated on-pump CABG was assigned either Elderly Group (GE, n=103, 41%) or Adult Group (GA, n=150, 59%).The clinical and demographic characteristics of the patients are summarized in Table 1, which demonstrates a higher prevalence of males in both groups: GE = 61% and GA = 70%; no difference regarding gender, history of CAD in the family, hypertension, alcohol consumption, sedentary lifestyle, acute myocardial infarction (AMI), coronary angiography (CAT), previous angina pectoris, previous peripheral vascular disease (PVD), previous CABG, chronic renal failure (CRF) and failure chronic heart failure (CHF) and dyslipidemia.However, patients in the GA had a higher prevalence of diabetes mellitus (DM) (39.6% vs. 27%, P=0.043) and smoking (32.2% vs. 19.8%,P=0.042), whereas the GE patients had a higher prevalence of stroke prior (17% vs. 6.7%,P=0.013).
Table 2 shows the results of the surgery.There was no significant difference in mortality between the groups (P=0.165),but the rate of hospital morbidity was significantly higher in GE (30% vs. 14%, P=0.004).Complications were divided into five categories: (1) pulmonary complications: respiratory infection, (2) cardiac complications: arrhythmia, cardiac arrest, reinfarction, precordial pain and atrial fibrillation, (3) gastrointestinal complications: abdominal distension, (4) neurological complications: stroke, and (5) other complications: increased postoperative bleeding, mediastinitis, septic shock and sternal instability.There was no significant difference between the categories of complications comparing the groups.
Intraoperative data, MV and length of stay for both groups are shown in Table 3.There was no significant difference between groups in the time length of stay on MV <24 hours (P=0.096),MV between 24 and 48 hours (P=0.071) and MV> 48 hours (P=1.000);time of CPB (P=0.334) and aortic clamping (P=0.214),number of grafts (P=0.412),length of stay in ICU (P=0.140) and total time in hospital (P=0.144).However, the GE patients had more days hospitalized than patients in GA (P=0.036).
In Table 4, we analyzed the in-ICU and total in-hospitalization time in two groups.In-ICU ≥ 5 days was greater in GE group (P = 0.010), but there is no difference in total in-hospital time between groups (P = 0.141).
After univariate analysis, the risk factors associated with hospital mortality were chronic renal failure, dyslipidemia, lin-ICU time ≥ 5 days, in-ICU time, in-ward time, MV for more than 24 hours, CPB time, cardiac and respiratory complications.However, the age ≥ 65 years was not a risk factor (Table 5).

DISCUSSION
This study in patients undergoing CABG alone suggests that patients aged ≥ 65 years are subject to greater risk of postoperative complications than patients under 65, but there was no difference between the mortality rate between the groups.
Regarding to mortality rate, a study examining predictors of hospital mortality in patients undergoing CABG in acute myocardial analyzed that advanced age is a risk factor related to mortality [13].Rocha et al. [14] also reported on a study conducted at the National Institute of Cardiology of Rio de Janeiro that the variables: age ≥ 70 years, need for reoperation for revision of homeostasis, sepsis and respiratory complications postoperatively were associated with hospital mortality.As well, in another study in Santa Catarina/Brazil, the authors found the same relationship [15].In our study, we found that age ≥ 65 years was not a predictor of mortality, similar to other reported by Ng et al. [16] in a retrospective study with 1594 patients undergoing CABG alone, where no significant difference in hospital mortality between patients aged ≥ 70 years (5.4%) compared to those with less than 70 years (3.8%).Even after 30 days of surgery, the mortality of patients aged ≥ 70 years was 3.8% compared with 3.3% of patients aged <70 years (P<0.740).
The morbidity rate in hospital was higher in the GE compared to the GA.This data is in according to other study, which were also investigated the outcomes of CABG in elderly patients [14,17,18].Pivatto et al. [19] observed that the morbidity rate was 34.4% in octogenarian patients undergoing CABG alone.We observed a morbidity rate of 30% in GE that was significantly higher compared to patients in the GA (14%).These data support the hypothesis that elderly patients have more postoperative complications.
In a retrospective study, Machado et al. [5] reported 10% mortality rate in octogenarian patients undergoing CABG, and observed the occurrence of cardiac arrhythmias (especially atrial fibrillation), cerebrovascular, and respiratory complications in the postoperative period.In our study, the cardiac complications were also major postoperative complications (12.6%).However, it was followed by respiratory complications (4.9%), and a lower incidence of neurological complications (1.9%).
Anderson et al. [20] observed predictors of mortality in patients undergoing cardiac surgery comparing septuagenarians and octogenarians, there was no significant difference in mortality rate between the groups.As observed in our study, preoperative variables did not increase the risk to death, but researchers have shown that cardiopulmonary bypass time > 75 minutes has 3.2 times (CI: 1.3 -7.9) greater chance of to death than patients with cardiopulmonary bypass time < 75 minutes, and postoperative variables such as prolonged mechanical ventilation above 12 hours, length of stay in ICU, reoperation, inotropic support more than 48 hours, and the need for blood products are associated with increased mortality.In this study, we found that postoperative variables such as length of stay in hospital, and cardiac and respiratory postoperative complications are associated with higher mortality, suggesting that patients who had postoperative complications remained more time hospitalized, increasing the risk of mortality hospital.
Recently, in a retrospective study [14] with 655 patients undergoing CABG, the authors observed that length of stay in ICU ≥ 3 days had positive correlation with death, but this study did not examine this relationship by age, and yes, total population sample.Our results show that length of stay ≥ 5 days had positive correlation with death in GE, emphasizing the importance of studies that evaluate the outcomes of CABG in elderly patients.
Analyzing the most recent data in the literature, there is disagreement about what age, in elderly patients, the morbimortality appears to be significantly higher compared to adult patients.We found studies that described their groups of elderly with age ≥ 65 years-old [12], ≥ 70 yearsold [13][14][15][16][17], ≥ 75 years-old [6,21], ≥ 80 years-old [22] and ≥ 85 years-old [23].Therefore we will suggest that more studies to be made in order to can to conclude in which age the risks factors of this surgery appear enlarged, whether preoperative, intraoperative or postoperative outcomes.

CONCLUSION
This study suggests that patients with 65 years old or more undergoing isolated on-pump coronary artery bypass surgery have a higher risk of postoperative complications in comparison with younger patients.The highest prevalence was heart complications, followed by respiratory complications; and lower prevalence of gastrointestinal and neurological complications.

Table 1 .
Clinical and demographic preoperative characteristics.

Table 4 .
Results of the length of stay in the ICU and total time in-hospital.
GA= adult group; GE= elderly group; ICU= intensive care unit

Table 3 .
Intraoperative data, mechanical ventilation and length of stay.

Table 6 .
Predictive factors of hospital mortality by logistic regression analysis.