Cardiovascular diseases are the main cause of mortality worldwide1, and ischemic heart disease accounts for about 7,500,000 deaths per year.1 In Brazil, ischemic heart disease causes 107,916 deaths per year.2

Hospital stays and diagnostic and therapeutic procedures related with coronary artery disease (CAD) have a meaningful economic impact on paying sources, as wells as treatment-related complications. Complications of surgical myocardial revascularization (CABG) impose additional expenses on the procedure; however, different types of complications determine a varying increase in hospital expenses with CABG. This study aims at determining the economic impact of CABG postoperative complications during stay in a hospital of the Brazilian Unified Health System (SUS).

This is a single-center observational retrospective study.

We selected 240 patients undergoing CABG at the National Institute of Cardiology (INC) in the period from 01 January to 31 December, 2013.

We included patients aged over 30 years, of both genders, with coronary artery disease confirmed by coronary angiography and indication for surgical myocardial revascularization after evaluation by the medical staff, composed of a clinical cardiologist, a hemodynamicist and a cardiac surgeon. We excluded patients who had undergone surgical myocardial revascularization combined with other surgical procedures, such as valve surgeries and vascular surgeries.

Hospitalization costs related to medications, laboratory tests, complementary imaging tests, materials, healthcare professionals and other indirect costs, collected from patients' medical records, were counted in accordance with the data provided by the cost centers. Indirect costs data were obtained from the Transparency Portal of the Brazilian Federal Government. Service agreements and expenses with security, food, information technology, contracting of general services, engineering companies, and maintenance of medical equipment were counted. The consolidated results allowed for the apportionment of the indirect costs per patient day. The costs with healthcare professionals were calculated according with the number of clinical doctors, surgeons, anesthetists, nurses, nursing technicians, physiotherapists, nutritionists and speech therapists who worked in the care of each patient. Subsequently, data related to the wages and workload of each professional were obtained from the Transparency Portal of the Brazilian Federal Government and, with this information, it was possible to estimate the value per hour worked by each professional involved in the healthcare of each patient, in each hospital sector where this patient remained hospitalized. We used the micro-costing method, in which the interventions performed on the patients are individually counted, finally leading to the total hospitalization costs. The values used as basis of cost estimation were obtained from the Table of Procedures and Medications of SUS Managing System (SIGTAP).

A total of 240 patients, 169 males and 71 females, who had undergone isolated myocardial revascularization at the National Institute of Cardiology, in 2013, were observed as shown in Table 1.

Mean age was 61.7 years, 60.9 for men and 63.4 for women (p = 0.054). Twenty-four patients were over 75 years of age (10.0%).

The mean time of hospital stay was 32.3 days with standard deviation of 22.7 days. The patients waited, on average, 14.2 days for the surgery, with standard deviation of 8.4. The average recovery period after surgery was 18.4 days, with standard deviation of 20.9 days.

In total, 97 patients incurred complications of some type during hospitalization, corresponding to 40.4% of patients. Complications were grouped into categories related to infectious complications, cardiovascular complications, arrhythmia, bleeding and others, which could not be classified in the other groups, as shown in Table 2.

Direct costs were analyzed by the micro-costing approach and organized into groups relating to medications, laboratory and complementary imaging tests, material and professional costs.

Table 3 shows the average costs per intervention category during hospitalization, and the next sections will demonstrate the costs per category.

The mean expenditure of hospitalization was R$ 22,647.24, with a median of R$ 14,772.98 and standard deviation of R$ 28,105.66.

In patients with any complication, corresponding to 97 individuals (40.4%), the mean expenditure was R$ 35,400.28, with standard deviation of R$ 40,509.47, and in those without complications, corresponding to 143 individuals (59.6%), the average expenditure was R$ 13,996.57, with standard deviation of R$ 5,800.61 (p < 0.001).

However, the complications and their associated costs may vary according to each category.

The 17 patients who evolved to bleeding, had a mean hospital expenditure of R$ 37,196.45 (SD = R$ 25,855.71), whereas the 223 patients without bleeding showed an expenditure of R$ 21,538.10 (SD = R$ 28,014.13) (p < 0.021).

The 27 patients with arrhythmia had an average expenditure of R$ 31,760.52 (SD = R$ 22.416,23), whereas the 213 patients without arrhythmia showed an average expenditure of R$ 21,492.03 (SD = R$ 28,583.01) (p < 0.074).

The 37 patients who developed cardiovascular complications showed an expenditure of R$ 45,899.94 (SD = R$ 56,287.27), and the patients without cardiovascular complications showed an average expenditure of R$ 18,409.06 (SD = R$ 15,902.53) (p < 0.005).

The patients with infectious complications, corresponding to 37 individuals, showed a mean expenditure of hospitalization of R$ 53,949.79 (SD = R$ 56,814.94), whereas the patients without infectious complications showed an expenditure of R$ 16,941.84 (SD = R$ 12,130.63) (p < 0.001).

The additional expenditures for complications, as well as the additional mean length of stay are demonstrated in Table 4.

The occurrence of multiple complications during hospital stay are associated with increased hospitalization costs, as shown in Table 5.

With regard to the intra-hospital mortality, 27 deaths (11.3%) were observed. The mean age of the patients who died was 68.2 years, whereas those who survived had a mean age of 60.9 years (p = 0.001). Mortality in patients who presented with at least one complication was 27.8%.

The patients who died had an average hospitalization cost of R$ 40,497.63, with standard deviation of R$ 44,819.92, whereas those who survived had a mean cost of R$ 20,384.51, with standard deviation of R$ 24,463.07 (p = 0.036).

Table 6 shows the comparisons between the patients who died and those who survived.

An understanding of the hospital costs due to CABG-related complications is important because this is a procedure of high complexity and cost, and it is performed in a large number of patients during the treatment of ischemic cardiac disease, allowing for a rational and evidence-based use of healthcare resources.

In this study, the average cost of hospitalization was higher than that found in other studies carried out in Brazil. A prospective study performed with 103 coronary patients submitted to isolated elective CABG, observed that the average cost of hospitalization was R$ 6,990.30.3

The occurrence of complications is associated with increased hospitalization costs, but this increase depends on the type of complication observed. The most frequent were infectious and cardiovascular complications, followed by arrhythmia and bleeding.

The patients who presented cardiovascular complications, infectious complications and bleeding in the CABG postoperative period had a higher average hospitalization cost than the patients without these complications, because they consumed more material and human resources. In addition, they demanded a longer length of hospital stay.

Twenty-seven patients were diagnosed with arrhythmia-related complications during the postoperative period. The occurrence of atrial fibrillation (AF) was 12.2%, corresponding to 20 patients, a lower percentage compared to the percentage observed in another study, in which 33.6% of the patients presented atrial fibrillation.4 This result is in accordance with a study that observed that atrial fibrillation occurred in 15.2% of the patients analysed5 and another study that observed that atrial fibrillation occurred in 17.2% of patients, being the most frequent complication.6 Another study demonstrated that patients who evolved with atrial fibrillation during the CABG postoperative period had a higher average hospitalization cost compared to the patients without arrhythmia,7 which cannot be confirmed by this study.

Patients who evolved with infectious complications had a higher cost compared to the patients who evolved without nosocomial infections. HILLIS LD et al.,8 demonstrated that nosocomial infections during CABG hospitalization are frequent events, occurring in 10 to 20% of cardiac surgery patients, with superficial wound infection occurring in 2% to 6% of patients after cardiac surgery and deep sternal wound infection in 0.45% to 5% of cases. A study conducted in the state of Rio Grande do Sul with 717 patients observed an incidence of infections in the postoperative period of CABG of 19.1%, a higher percentage compared to the percentage found in this study (15.4%).9 Surgical wound infections after CABG extend the length of hospital stay and increase hospitalization costs. The increase in hospitalization costs was attributed to more frequent use of antimicrobial agents in patients who had nosocomial infection.10

Patients with cardiovascular complications also had increased hospitalization cost. A study carried out identified that cardiovascular complications, such as stroke and postoperative shock following CABG increased hospitalization costs, because greater material and human resources were necessary due to extended length of hospital stay.11

Patients who had bleeding during the CABG postoperative period had a higher average hospitalization cost compared to patients without bleeding. Other studies also report the impact of this complication on the increase of hospital costs.11^,12

The mortality rate observed in this study is similar to the one found in other Brazilian studies,13 which showed a mortality rate of 13%. Another study carried out in Brazil,14 in the city of Rio de Janeiro, showed that in-hospital CABG mortality in four hospitals ranged from 7.0% to 14.3%, with a joint mortality rate of 10.9%.

The patients who died had a higher cost compared to the survivors. This result is in accordance with another study5 performed with 14,780 patients submitted to isolated CABG, which demonstrated that the patients who died had higher hospital costs, with an average cost of US$ 49,242, currently corresponding to R$ 178,748.46.

Among the limitations of this study, we can highlight that it is an observational and retrospective study. Consequently, we depended greatly on the accuracy of the information contained in the medical files to carry out this research. The undertaking of the study in a single reference center may generate questions about the validity of its findings in other hospitals of the SUS where the procedure is performed. Few patients underwent off-pump CABG, which limits the application of this study's results to this type of surgery. Another limitation of this study is related with the non-inclusion of patients who were readmitted precociously due to late surgical complications, since the discharge from hospital can happen before the occurrence of any clinical manifestation.

We conclude that the occurrence of complications during CABG hospitalization significantly increases the expenditures with the procedure, but the magnitude of this increase will depend on the type of complication developed, with the highest costs being related to cardiovascular complications, infectious complications and bleeding.