Myocardial revascularization surgery (MRS): results from National Health System (SUS)

Abstracts

FUNDAMENTO: A cirurgia de revascularização do miocárdio (CRM) é a cirurgia cardíaca mais frequentemente praticada no país, sendo a maior parte realizada pelo Sistema Único de Saúde (SUS). OBJETIVO: Avaliar os resultados da CRM, não associada a outros procedimentos. MÉTODOS: Analisaram-se as informações do banco de dados SIH/DATASUS, disponibilizado on-line. Esse banco de dados contém informações relativas a: sexo, idade, permanência hospitalar, valor da autorização de internação hospitalar (AIH), número de cirurgias realizadas por hospital e mortalidade hospitalar. Avaliaram-se apenas as CRM realizadas sem procedimentos associados. RESULTADOS: Entre 2005 e 2007 foram realizadas 63.529 cirurgias em 191 hospitais. Foram excluídos 16 hospitais de muito baixo volume cirúrgico, restando 63.272 cirurgias para análise final. A mortalidade hospitalar total foi de 6,22%, sendo maior nos hospitais de pequeno volume do que nos de grande volume (> 300 cirurgias no período), 7,29% versus 5,77% (p<0,001). A média de permanência hospitalar foi de 12 dias, não havendo diferença entre os de pequeno (12,08±5,52) e de grande volume (12,15±7,70). O gênero masculino teve menor mortalidade do que o feminino, 5,20% versus 8,25% (p<0,001), assim como os mais jovens quando comparados com os idosos (> 65 anos), 4,21% versus 9,36% (p<0,001). Encontrou-se uma pequena variação no valor da AIH entre a região Sul, R$ 7.214,63 e Nordeste, R$ 6.572,03 (p<0,01). A distribuição regional de cirurgias foi desigual, Sul e Sudeste concentram 77% delas. CONCLUSÃO: A CRM realizada pelo SUS tem mortalidade maior nos hospitais de baixo volume, nas mulheres e nos idosos. Futuros estudos prospectivos se fazem necessários.

Revascularização miocárdica; avaliação de risco; qualidade da assistência á saúde; administração em saúde

FUNDAMENTO: La cirugía de revascularización de miocardio (CRM) es la cirugía cardiaca más frecuentemente practicada en el país, con la mayor parte realizada por el Sistema Único de Salud (SUS). OBJETIVO: Evaluar los resultados de la CRM no asociada a otros procedimientos. MÉTODOS: Se analizaron las informaciones del banco de datos SIH/DATASUS, disponible online. Este banco de datos contiene informaciones relativas a: sexo, edad, permanencia hospitalaria, valor de la autorización de internación hospitalaria (AIH), número de cirugías realizadas por hospital y mortalidad hospitalaria. Se evaluaron solamente las CRM realizadas sin procedimientos asociados. RESULTADOS: Entre 2005 y 2007 se llevaron a cabo 63.529 cirugías en 191 hospitales. Se excluyeron 16 hospitales de muy bajo volumen quirúrgico, restando 63.272 cirugías para análisis final. La mortalidad hospitalaria total fue del 6,22%, con mayor índice en los hospitales de pequeño volumen que en los de gran volumen (≥300 cirugías en el período), el 7,29% versus el 5,77% (p<0,001). El promedio de permanencia hospitalaria fue de 12 días, sin diferencia entre los de pequeño (12,08±5,52) y de gran volumen (12,15±7,70). El género masculino tuvo menor mortalidad que el femenino, el 5,20% versus el 8,25% (p<0,001), así como los más jóvenes cuando comparados con los adultos mayores (≥ 65 años), el 4,21% versus el 9,36% (p<0,001). Se encontró una pequeña variación en el valor de la AIH entre la región Sur, R$ 7.214,63 y Nordeste, R$ 6.572,03 (p<0,01). La distribución regional de cirugías fue desigual, Sur y Sudeste concentran el 77% de ellas. CONCLUSIÓN: La CRM realizada por el SUS tiene mortalidad mayor en los hospitales de bajo volumen, en las mujeres y en los adultos mayores. Futuros estudios prospectivos se hacen necesarios.

Revascularización miocárdica; evaluación de riesgo; calidad de la asistencia a la salud; administración en salud

REVIEW ARTICLE

Myocardial revascularization surgery (MRS). Results from National Health System (SUS)

Leopoldo S. Piegas; Olímpio J Nogueira V Bittar; Nagib Haddad

Instituto Dante Pazzanese de Cardiologia, São Paulo, SP - Brazil

Mailing address

ABSTRACT

BACKGROUND: Myocardial revascularization surgery (MRS) is the most common surgery in this country, with most being performed through the National Health System(SUS).

OBJECTIVES: To assess MRS results when not associated to other procedures.

METHODS: The information from the Hospital Information System (SIH/DATASUS) made available online was submitted to analysis. The data include information on gender, age, hospital stay period, hospital admission authorization (AIH) costs, number of surgeries at each hospital, and in-hospital mortality rate. Only MRS with no associated procedures were analyzed.

RESULTS: A total of 63,529 surgeries were performed in the period between 2005 and 2007 at 191 hospitals. Sixteen hospitals reporting very low surgery volume were excluded. The remaining total number of surgeries came down to 63,272 for the final analysis. In-hospital mortality rate was 6.22%, with small surgery volume hospitals reporting higher rate than high volume hospitals (>300 surgeries in the time period under study), 7.29% versus 5.77% (p<0.001). Average hospital stay time length was 12 days, with no difference having been reported between low (12.08±5.52) and high volume (12.15±7.70) hospitals. Males reported lower mortality rate than females - 5.20% versus 8.25% (p<0.001), similarly to younger individuals when compared to the elderly (> 65 years of age), 4.21% versus 9.36% (p<0.001). A slight variation was observed in AIH values between the Southern Region (R$ 7.214,63 - approximately US$ 3,600.00) and the Northeastern Region (R$ 6.572,03 – approximately US$ 3,280.00) (p<0.01). Regional distribution of surgeries was not comparable in all regions in the country, with Southern and Southeastern Regions having reported 77% of them.

CONCLUSION: MRS performed by SUS has reported high mortality rate in low volume hospitals, among women, and among the elderly. Future prospective studies are deemed to be necessary.

Key words: Myocardial revascularization / mortality; risk assessment; quality of health care; health administration.

Introduction

Despite the advances brought by clinical therapeutics and PCI, myocardial revascularization surgery is still quite widely used to treat coronary failure patients.

SUS is one of the largest health care systems in the world, having reported 11,315,333 hospital admissions in 2007 for the total Brazilian population (189,335,187) – a 6% admission rate. It should be pointed out that 21.07% of that population has some kind of private health insurance coverage1.

Myocardial revascularization surgery (MRS) is the most frequent from all heart surgeries performed by SUS both at public hospitals and at private or philanthropic ones, involving over one hundred surgery teams.

It has been estimated that SUS is responsible for 80% of all MRS in this country. Those surgeries are qualified for reimbursement to the hospitals rendering that service. Data are submitted to auditing. AIH, in-hospital stays, and mortality rate - among others - are made available for public consultation on SUS Data Base (DATASUS). Up to this point in time, the same data in reference to surgeries performed by the Supplementary Medicine System or the Private System are not available for consultation².

The purpose of this paper was to assess MRS results in order to measure the quality standard of services provided by SUS through system available variables, as follows: Gender, age, geographic location, number of surgeries performed, in-hospital time period and hospital expenses.

Methods

Analysis data on MRS were obtained from SUS Hospital Information System (SIH) - SIH/DATASET3. That Data Base is operated by the Ministry of Health, is submitted to auditing, and collects information on hospital admittance for every patient at hospital admission. It is also the tool used to control payment of the amounts due to hospitals rendering services.

Data analysis was based on information from the period between 2005 and 2007, since that not only was the most recent information available but also showed the indications and surgery techniques currently in use.

MRS was investigated in cases where it was performed as an isolated procedure. Cases using associated surgical procedures (prostheses and valvuloplasty, aneurysm correction, and carotid endarterectomy) were excluded. Therefore, in the classification of SUS procedures the following codes were selected: 48010073 (MRS with extracorporeal circulation); 48010081 (MRS with extracorporeal circulation and double grafting or more); 48010090 (MRS without extracorporeal circulation), 48010103 (MRS without extracorporeal circulation with double grafting or more). That means to say: only isolated procedures used for myocardial revascularization with or without extracorporeal circulation.

In order to verify the differences between high and low production volume hospitals, they were divided into two groups. The very low production hospitals were excluded. A very low production hospital meant not more than one surgery per month in the three-year period. A high volume hospital was defined as that with records of 100 or more isolated MRS per year. Following such grouping, the low volume hospitals had records between 37 and 299 MRS, whereas high volume, 300 or more surgeries. Sixteen hospitals were excluded. They had records of 36 or minus surgeries in the three-year period (257 surgeries, 0.40% of the total number).

The number of MRS with associated procedures – not included in the present analysis – was 6,256, which represents 8.96% of the total number of MRS.

Results were also analyzed taking gender and age into account, as well as reimbursement amounts for hospital expenses (AIH based), and patients' hospital stay.

Statistical Analysis

Qualitative variables are presented percentage wise. Comparisons were performed using χ2 (chi-square). Means, standard deviation, minimal and maximal values were calculated for quantitative variables. Comparisons of two means were done using Student t test or Mann-Whitney's non-parametric test whenever necessary.

For the simultaneous comparison of a number of means, one criterion-variance analysis was used. Scheffé's test was used for multiple comparisons. Whenever indicated, Kruskal-Wallis's non-parametric test was used for those comparisons. Significance level was defined to be p< 0.05.

Results

In the period between 2005 and 2007, 63,529 isolated MRS were performed by SUS (2005: 20,337; 2006: 21,848; 2007: 21,344 patients) at 191 hospitals in Brazil. After all the exclusions, 63,272 isolated MRS performed at 175 hospitals remained for analysis. Global in-hospital mortality rate was 6.22%. In the three-year period, 55 (30%) hospitals performed over 300 isolated MRS, with a total of 44,539 (70%) surgeries.

Table 1 shows in-hospital mortality rate according to volume – low or high volume – of surgeries performed in that period. Higher mortality rate was observed at low volume hospitals, which are bigger in number. They accounted for 30% of the surgeries – 7.29% versus 5.77% (p<0.001) respectively. At high volume hospitals in-hospital mortality ranged from 1.91 to 19.13% (Figure 1); at low volume hospitals (120 hospitals with 18,733 surgeries) it ranged from 0.00 to 35.71 (mean = 7.29%).

Table 2 shows in-hospital mortality rate in different Brazilian regions. Differences are statistically significant (p<0.001), with the highest death rate having been observed in the Central Western Region, and the lowest in the Northeastern Region.

Table 3 shows mortality rate per gender and age of patients who have been submitted to the surgery. Males have reported lower mortality rate than females – 5.20% versus 8.25% (p<0.001). Likewise, younger patients (0-64 years old) when compared to the elderly (=>65 years of age) – 4.21% versus 9.36% (p<0.001).

Table 4 shows mean time period for hospital stay in number of days and AIH average cost in Brazilian currency respectively to each physiographic region. The differences between time length at hospital have not been found to be statistically significant (p>0.05). The differences between AIH mean values were statistically significant when Southern and Northeastern regions were compared - R$ 7.214,63 versus R$ 6.572,03 (p<0.01) respectively.

Table 5 shows the comparison between mean in-hospital time length (number of days) and AIH mean values following surgery volume at hospitals. It should be pointed out that such difference is not significant for any of the variables.

However, Table 6 also shows the comparison between public and private hospitals with high volume of isolated MRS in regard to in-hospital time length and AIH mean values. Significant difference could be observed between in-hospital time length – 16.54 versus 11.40 days (p<0.01). Such difference could not be observed between AIH values - R$ 6.990,16 versus R$ 6.864,74 (p>0.05), respectively.

Table 7 shows number of surgeries/population ratio in the five country regions. Thirty-four isolated MRS were performed in Brazil for every 100,000 individuals. A large difference could be observed in the number of procedures performed in each of the regions, having been the Southern region the most favored - 60/100,000 – and the Northern region the most unfavored - 9/100,000 – ratios respectively.

Discussion

Surgery data are compulsorily stored in the national system, audited, and operated by SUS Hospital Information System – SIH/DATASUS. For the purpose of treatment standardization, only isolated MRS were analyzed. Such choice was the standard group procedure.

A total of 79.03%1 in the Brazilian population has coverage for medical assistance by SUS. Most high complexity procedures are performed under that system. As an administrative system used for billing, the data base lacks clinical data such as risk factors, co-morbidities, surgery indications, physical examinations, and hospital complications, among others. On the other hand, the large number of surgeries performed and the basic data on in-hospital patients that is made available, such as gender, age, in-hospital mortality rate, and number of surgeries per hospital make up a reliable data base for results per hospital, per region, per total or any other grouping to be assessed. The high number of surgeries under analysis is expected to set forth uniform guidelines for the possible deviations that may be found in less wide-reaching studies.

In 2007 – the last year in the 3-year analysis – a slight reduction in the number of surgeries could be observed, most likely as a result of the growing number or percutaneous coronary interventions (PCI).

Mortality rate was found to be 6.22% for a total of 63,272 patients in the present study. Although higher as compared to other countries, it is similar to what was reported by Ribeiro and cols. for the period between 2003-2004, and based on data from the same data base (SIH/DATASUS)4. The authors reported a 7% mortality rate for a total of 65,716 patients who had been submitted to coronary surgery (their research also included coronary surgeries with associated procedures). Mesquita et al5 conducted assessed a small series of 114 consecutive patients submitted to isolated MRS at a Rio de Janeiro hospital. Surgery mortality rate was reported to be 4.9%5. The Journal Adult Cardiac Surgery in New York State 2003 – 2005 reports a 2.14% in-hospital mortality rate within 30 days for a total of 40,429 patients submitted to isolated coronary surgery and who were operated on and discharged from hospital in the time period between 2003 and 20056. In that study, mortality rate per hospital ranged from 0.76 to 4.01%. In 1995, mortality rates reported for a total of 11,731 patients who had been submitted to isolated coronary surgery in six different countries in the voluntary project European System for Cardiac Risk Evaluation (EuroSCORE) were: Germany – 2.4%; United Kingdom – 3.7%; Spain – 6.8%; Finland – 1.5%, France – 3.2%, Italy – 2.4%. Average – 3.4%7. A retrospective study with 3,670 patients consecutively submitted to isolated MRS at a hospital in New York State reported a 2.7%8 in-hospital mortality rate. Despite the limitations for the comparison between the different series submitted to the same surgery, a lower mortality rate could be observed both in Europe and in the United States when compared to Brazil.

Although low volume surgery hospitals may present good results, the ratio lower surgery volume / higher mortality rate is typically found9. For MRS in particular, any volume lower than 100 surgeries per year is usually associated to higher mortality rate10. The same study shows that even higher volume hospitals report differences that will deserve further future investigation. One of the possible explanations is associated to the different teams working at the same hospital.

Similar studies have reported higher mortality rate among females and the elderly11,12. Females presenting a coronary atherosclerosis condition typically present less clear impairment of vessel wall injuries (usually lower caliber), and consequently a more severe form of the condition. While studying 2,034 patients - 69% of them males and 31% of them females – Amato and cols. observed a 4.9% mortality rate among males and 6.3% among females13.

In-hospital stay did not vary in the different regions. However, it was shown to be longer at high surgery volume public hospitals when compared to private hospitals. That could mirror better administration and/or higher funding and autonomy at private hospitals.

AIH showed to have slight regional variation. It was lower in the Northeastern region if compared to the Southern region. AIH is usually used to calculate hospital stay costs, but it is hardly informative for funding studies since it mirrors the payment for a non-elastic package in terms of constitution rather than the proper allocation of funding for the calculation of the real cost of procedures. AIH does not actually mirror the real cost of procedure, but rather the reimbursement of amounts previously defined by services rendered. In a recent study, Haddad et al14 have shown that compensation by SUS is lower than the real cost of surgery, even at public hospitals where it is partially subsidized by some government organ. Hardly any study is available on the cost of procedures.

High disparity can be observed in the number of surgery / population ratio in the different regions. A clear relationship can be seen between social and economic development. The Southern and the Southeastern regions report the highest number of surgeries per individuals when compared to the Northern and Northeastern regions. The Southern and Southeastern regions account for 77% of the surgeries. Such disparity is associated to a higher number os hospital beds and specialized hospitals in those regions. Mortality rate was similar, although a slight difference could be observed to favor the Northeastern region when compared to the Central Western region.

Some European countries as well - such as The United Kingdom, Spain, Finland, and France – do present differences in the number of myocardial revascularization surgeries per 100,000 individuals – 44.4, 16.2, 92.1 and 40.815 respectively.

Quite a number of variables unquestionably interfere in the outcome of a successful] MRS, among them whether the surgery is an urgency/emergency, whether it is associated to risk factors such as obesity, associated morbidities, number of impaired arteries, reduced ventricular function, post-operative complications, the number of surgeries performed by the team, other situations when risk is increased, thus unveiling the complexity of studies such as the present one.

Limitations

The major limitation faced by the present study was the fact that it did not count on clinical data on patients submitted to the surgery. Not only age and gender are key contributors for surgery results, but the conditions under which the surgery was performed as well as patient's status. The lack of such information hinders mortality rate adjustment according to patient's severity.

Another factor is that different surgery teams work at the same hospital. Not always do those teams reach the same results, which may interfere in the outcome.

Conclusions

The present study analyzed isolated myocardial revascularization surgeries performed by SUS in the period between 2005 and 2007. The study showed higher in-hospital mortality at lower surgery volume hospitals, among women, and among the elderly. Mortality rate was higher than that observed in some countries, although similar to other countries. The comparison faced difficulties from the lack of clinical variables and risk adjustments in the data base used for consultation. Future prospective studies must take those factors into account.

Potential Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Sources of Funding

There were no external funding sources for this study.

Study Association

This study is not associated with any post-graduation program.

References

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Publication Dates

• Publication in this collection
  20 Jan 2010
• Date of issue
  Nov 2009

History

• Reviewed
  30 Oct 2008
• Received
  01 Oct 2008
• Accepted
  16 Dec 2008