Indicators of healthcare quality in isolated coronary artery bypass graft surgery performed at a tertiary cardiology center

Mesquita, Evandro Tinoco; Ribeiro, Ary; Araújo, Mônica Peres de; Campos, Luiz Antonio de Almeida; Fernandes, Marco Aurélio; Colafranceschi, Alexandre Siciliano; Silveira, Celso Garcia da; Nunes, Edson; Rocha, Antônio Sérgio Cordeiro da

doi:10.1590/S0066-782X2008000500008

Abstracts

BACKGROUND: Quality indicators (QI) for cardiac surgery are important instruments for measuring healthcare quality in hospital centers and allow comparison with high-quality healthcare centers. OBJECTIVE: To evaluate QIs in isolated myocardial revascularization procedures (CABG) performed at a tertiary cardiology center. METHODS: One hundred and forty-four consecutive patients who had undergone isolated CABG were evaluated between October 2005 and March 2007. One hundred and eight patients were men (75%), the mean age was 65±11, and the EuroSCORE was 4±3. The following QIs were measured: time elapsed between the surgery date-setting appointment and the actual day of the CABG (TDC); surgery cancellation rate (SCR) due to problems in hospital infrastructure; length of hospital stay (LOS); operative mortality (OM) and rate of readmission (RHR) for infection in the surgical wound. RESULTS: The TDC (n=98) was 4±3 days (median: 4 days) and the SCR was zero. The OM recorded of 4.9% (95% confidence interval [CI] = 2.2 - 9.87%) was lower than the expected OM of 5.1% (95% CI = 1.4% to 14.37%), but with no statistical significance (p=0.65). The area under the ROC curve of the EuroSCORE for the OM was 0.702 (95% CI = 0.485 - 0.919). LOS was 11±9 days. The area under the ROC curve of the EuroSCORE for the LOS was 0.764 (95% CI = 0.675 - 0.852). The RHR recorded was 2.1%. CONCLUSION: The measurement of the QIs showed that, in a medical center with a low annual volume of CABG, the results were compatible with the risk profile of the population involved.

Perioperative care; quality of health care; quality indicators, health care; myocardial revascularization

FUNDAMENTO: Indicadores de qualidade (IQ) em cirurgia cardíaca são importantes instrumentos de avaliação da assistência médica em centros hospitalares. OBJETIVO: Avaliar os IQ da cirurgia de revascularização miocárdica (CRVM) isolada em centro terciário cardiológico. MÉTODOS: Foram avaliados 144 pacientes consecutivos submetidos a CRVM isolada entre outubro de 2005 e março de 2007: 108 pacientes eram do sexo masculino (75%), com média de idade de 65±11 anos e EuroSCORE de 4±3. Os IQ avaliados foram: intervalo de tempo entre a marcação e a realização da cirurgia (TMC); taxa de cancelamento (TxC) decorrentes de problemas ligados à infra-estrutura hospitalar; tempo de permanência hospitalar (TPH); mortalidade operatória (MO) e taxa de reinternação hospitalar por infecção em ferida cirúrgica (TxRH). RESULTADOS: O TMC (n=98) foi de 4±3 dias (mediana de 4 dias) e a TxC foi zero. A MO observada de 4,9% (Intervalo de Confiança [IC] 95% = 2,2 - 9,87%) foi menor do que a MO esperada de 5,1% (IC 95% = 1,4% a 14,37%), mas sem significância estatística (p=0,65). A área sob a curva ROC do EuroSCORE para MO observada foi de 0,702 (IC 95% = 0,485 - 0,919). O TPH foi de 11±9 dias. A área sob a curva ROC do EuroSCORE para TPH foi de 0,764 (IC 95% = 0,675 - 0,852). A TxRH observada foi de 2,1%. CONCLUSÃO: A avaliação dos IQ demonstrou que, em um centro com baixo número anual de CRVM, os resultados alcançados foram compatíveis com o perfil de risco da população envolvida.

Assistência perioperatória; qualidade da assistência a saúde; indicadores de qualidade em assistência a saúde; revascularização miocárdica

ORIGINAL ARTICLE

Hospital Pró-Cardíaco, Núcleo Técnico de Qualidade Assistencial, Rio de Janeiro, RJ - Brazil

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SUMMARY

BACKGROUND: Quality indicators (QI) for cardiac surgery are important instruments for measuring healthcare quality in hospital centers and allow comparison with high-quality healthcare centers.

OBJECTIVE: To evaluate QIs in isolated myocardial revascularization procedures (CABG) performed at a tertiary cardiology center.

METHODS: One hundred and forty-four consecutive patients who had undergone isolated CABG were evaluated between October 2005 and March 2007. One hundred and eight patients were men (75%), the mean age was 65±11, and the EuroSCORE was 4±3. The following QIs were measured: time elapsed between the surgery date-setting appointment and the actual day of the CABG (TDC); surgery cancellation rate (SCR) due to problems in hospital infrastructure; length of hospital stay (LOS); operative mortality (OM) and rate of readmission (RHR) for infection in the surgical wound.

RESULTS: The TDC (n=98) was 4±3 days (median: 4 days) and the SCR was zero. The OM recorded of 4.9% (95% confidence interval [CI] = 2.2 9.87%) was lower than the expected OM of 5.1% (95% CI = 1.4% to 14.37%), but with no statistical significance (p=0.65). The area under the ROC curve of the EuroSCORE for the OM was 0.702 (95% CI = 0.485 0.919). LOS was 11±9 days. The area under the ROC curve of the EuroSCORE for the LOS was 0.764 (95% CI = 0.675 0.852). The RHR recorded was 2.1%.

CONCLUSION: The measurement of the QIs showed that, in a medical center with a low annual volume of CABG, the results were compatible with the risk profile of the population involved.

Key words: Perioperative care; quality of health care; quality indicators, health care; myocardial revascularization.

Introduction

Within a context of increasing cost control for high-complexity procedures, it is important to systematically measure quality indicators for cardiac surgery. There are two types of healthcare quality measurements: those that measure performance, also known as indicators of results or outcomes, and those that measure the processes related to healthcare^1-6. Mortality rates after myocardial revascularization surgery (CABG), which measure surgeon performance, hospitals or both are examples of outcome indicators. Process indicators, on the other hand, frequently known as quality indicators (QIs), report rates of utilization of screening tests for diseases, use of medications on hospital admission and discharge, length of hospital stay, etc^3,4.

As populations of patients undergoing cardiac surgery may differ significantly among institutions and geographical areas, the comparison of absolute numbers, such as mortality rates for instance, is inappropriate for a cost-benefit analysis and comparison of outcomes among institutions^7-9. However, the risk-adjusted mortality rate is an important indicator of performance of surgical services (hospitals and surgeons) ^1,3,4,10-12.

In the United States, the Society of Thoracic Surgeons (STS) database is one of the most comprehensive and consistent systems for measuring and reporting results of cardiac surgery^13,14. This system collects data from all myocardial revascularization surgeries (CABG), valvar surgeries and cardiac transplants performed in that country.

In Brazil, medical literature is still lacking as to publications about quality indicators. Most reports address operative mortality in public hospitals involving patients of SUS - Sistema Único de Saúde (the Unified National Health System)^15,16.

Starting in October 2005, in order to comply with the requirements of the hospital accreditation process set by the Organização Nacional de Acreditação - ONA (National Accreditation Organization) and with the project of best clinical practices of the Associação Nacional de Hospitais Privados - ANAHP (National Association of Private Hospitals), Hospital Pró-Cardíaco began to systematically monitor the QIs of the care provided to its clients.

The aim of this study was to measure the quality indicators during the performance of isolated myocardial revascularization surgery at the Hospital Pró-Cardíaco.

Methods

From October 2005 and March 2007, 144 consecutive patients submitted to CABG were selected to be included in the study. One hundred and eight were men (75%), aged 65±11 years (median: 65 years). Fifty-one per cent of the patients were > 65 years of age (Table).

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CABG was performed by conventional techniques, and extracorporeal circulation (EC) was used in 90% of the cases. In those cases where EC was employed, mean aortic clamping time was 96±47 minutes (median: 88.5 minutes). Urgency or emergency surgeries were performed on 36 patients (25%).

The quality indicators analyzed were the following: time interval elapsed between the surgery date-setting appointment and the actual date of the procedure (TDC); surgery cancellation rate (SCR) due to problems in hospital infrastructure; length of hospital stay (LOS); operative mortality (OM) and rate of readmission (RHR) for infection in the surgical wound (saphenectomy, sternotomy, etc.).

Specifically for time calculation reasons between the date-setting appointment and the surgery itself, emergency or urgency surgeries were left out.

The operative mortality considered was the death rate recorded during the same hospital admission or within 30 days after surgery.

For outcome comparison purposes, the operative mortality was adjusted as per the standard EuroSCORE, so that the recorded operative mortality was compared to the expected operative mortality for each patient. The expected operative mortality was obtained using the logistic regression analysis applied to the standard EuroSCORE relative to operative mortality. Still according to the standard EuroSCORE, patients were grouped during the pre-operative phase as: low, medium and high operative risk. Length of hospital stay was also analyzed using the adjustment relative to standard EuroSCORE.

Continuous data are presented by their means, medians and standard deviations, whereas categorical data are presented by their respective proportions. To compare the continuous variables, we used either Student's t test or the single factor analysis of variance, and to compare categorical variables, Fisher's exact test or the chi-square test was used. For the variance analysis, the Dunnet test was used to allow comparison among the groups. To establish the correlation among continuous data, Pearson's Linear correlation was used. The area under the ROC (receiver operating characteristic) curve was calculated as a rate of how well the EuroSCORE could discriminate patients who survived from those who died or patients who remained in the hospital longer than 12 days from those who stayed less than 12 days. P values (two-tailed) equal to or lower than 0.05 were considered statistically significant.

Results

The time elapsed between the date-setting appointment and the surgery itself (n=98) was 4±3 days (median: four days). The rate of cancellation was zero. The EuroSCORE for the population studied was 4±3 (median: three). Low-risk EuroSCORE was observed in 38.7%, medium-risk in 38% and high-risk in 23.4% of the patients. The OM recorded of 4.9% (95% confidence interval [CI] = 2.2 9.87%) was lower than the expected OM of 5.1% (95% CI = 1.4% to 14.37%), but with no statistical significance (p=0.65). No difference in operative mortality was observed among patients considered as high (9.4%), medium (5.8%) or low (1.9%) risk as per the EuroSCORE (p=0.10). The operative mortality observed in low-risk patients as per the EuroSCORE was similar to the expected value (1.9% - 95% CI = 0.01 to 11.69% and 2.0% - 95% CI =1.9 to 2.58%, respectively). Among high-risk patients, the operative mortality observed was lower than expected (9.4% - 95% CI = 2.46 to 25.0% and 12.0% - 95% CI = 8.7 to 14.66%, respectively). The expected operative mortality for medium-risk patients was lower than the observed value (4.1%; 95% CI = 3.90 to 4.4% and 5.8%, 95% CI = 1.41 to 16.54%, respectively; p<0.0001). The area under the ROC curve of the EuroSCORE for operative mortality was 0.702 (95% CI = 0.485 0.919) (Figure 1).

The length of hospital stay was 11±9 days (median: eight days). A statistically significant correlation was observed between the length of hospital stay and the EuroSCORE (r=0.39, p<0.0001). Patients with a low EuroSCORE spent a significantly shorter time in hospital (8±4 days) than those with a medium (12±10 days; p=0.036) and high (15±10 days; p<0.0001) EuroSCORE. No significant difference was observed in the length of hospital stay of patients with medium-risk in comparison with those with high-risk EuroSCORE (p=0.147). The area under the ROC curve of the EuroSCORE for the length of hospital stay was 0.764 (95% CI = 0.675 0.852) (Figure 2). The rate of hospital readmission due to surgical wound infection was 2.1%.

Discussion

The findings of this study showed that the operative mortality rate recorded for isolated CABG, contrary to the link between outcomes and the number of surgeries performed by services and surgeons^1,10,17, is similar to the expected value (4.9%; 95% CI =2.2 to 9.87% vs 5.1%; 95% CI = 1.4% to 14.37%), with an area under the ROC curve of 0.702 (Figure 1). These data are in accordance with those recorded by Moraes et al¹⁶, who, by analyzing the use of the EuroSCORE in a population of 759 patients submitted to CABG, found 69.9% of agreement between the observed operative mortality rate and the expected operative mortality rate.

In Brazil, according to DATASUS data, an inverse relationship was shown between the volume of cardiac surgeries performed and operative mortality¹⁵. The results of our study do not confirm the existence of this inverse relationship, but they are consistent with North-American publications that report that the correlation between the number of surgeries and mortality is weak^10,17-19.

According to SUS data, operative mortality from CABG in Brazil is 7.0%, a rate which is higher than that reported in the database from the Society of Thoracic Surgeons in the USA and the records of cardiac surgeries performed in the United Kingdom¹⁹ and the rate observed in this study. However, as the authors emphasize, North-American and British databases refer to voluntary records of institutions that perform cardiac surgeries, whereas those from DATASUS are administrative data of institutions that perform surgeries in Brazil. Unfortunately, since the DATASUS data available are administrative, it is not possible to adjust operative mortality according to the severity of the patients' conditions.

According to some authors, the length of hospital stay for a CABG surgery should not exceed 12 days^20,21. In this study, the median total hospital stay was eight days. In accordance with findings by Toumpoulis et al²¹, a direct relationship was found between the EuroSCORE and the total length of hospital stay. Thus, patients with a low EuroSCORE remained a significantly shorter time in hospital than medium- and high-risk patients. Among medium- and high-risk patients, no significant difference was found. The area under the ROC curve of the EuroSCORE for total hospital stay was 0.744 (Figure 2). Therefore, EuroSCORE, similarly to what happened with operative mortality, helped to identify patients who were more likely to have longer hospital stays for myocardial revascularization surgery.

The rate of hospital readmission due to surgical wound infection in this study was 2.1%. This rate is lower than that reported in the database from the National Society of Thoracic Surgeons (STS) in the USA²².

One of our difficulties in evaluating the outcomes was in obtaining references for all indicators measured. There are no available data in medical literature about time elapsed between the date-setting appointment and the actual elective myocardial revascularization surgery. For this reason, the goal in our institution is to keep this time interval shorter than five days. The time between the date-setting appointment and the surgery in our study was four days (median). Likewise, at our institution the target for the cancellation rate due to problems in hospital infrastructure or processes linked to the procedure is zero (0%), and this was the rate observed throughout the 14 months of evaluation.

The quality of healthcare must, on principle, be safe, efficacious, patient-centered, timely, effective, and follow strict scientific methodology. Within this spirit, by evaluating healthcare quality indicators in CABG, the Hospital Pró-Cardíaco showed that, despite being a center with a low annual volume of CABG procedures performed, it reached results compatible with the risk profile of the population involved.

The control of quality indicators allows a broad evaluation of the institution by identifying strengths and weaknesses and, therefore, contributing to the improvement of quality of the care provided to patients.

Conclusion

QI assessment showed that, in a medical center with a low annual volume of myocardial revascularization surgeries performed, the results were compatible with the risk profile of the population involved.

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 graduation program.

References

1. Luft HS, Bunker JP, Enthoven AC. Should operations be regionalized? the empirical relation between volume and mortality. N Engl J Med. 1979; 301: 1364-9.
2. Brook RH. Health care reform is on the way: do we want to compete on quality?. Ann Intern Med. 1994; 120: 84-6.
3. Halm EA, Lee C, Chassin MR. Is volume related to outcome in health care? A systematic review and methodologic critique of the literature. Ann Intern Med. 2002; 137: 511-20.
4. Shahian DM. Improving cardiac surgery quality volume, outcome, process? JAMA. 2004; 291: 246-8.
5. Shahian DM, Grover FL, Anderson RP, Edwards FH. Quality measurements in adult cardiac surgery: introduction. Ann Thorac Surg. 2007; 83: S1-S2.
6. Shahian DM, Edwards FH, Ferraris VA, Haan CK, Rich JB, Normand SLT, et al. Quality measurements in adult cardiac surgery: part 1 conceptual framework measure selection. Ann Thorac Surg. 2007; 83: S3-S12.
7. Kolh P. Importance of risk stratification models in cardiac surgery. Eur Heart J. 2006; 27: 768-9.
8. Parsonnet V, Dean D, Bernstein AD. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease. Circulation. 1989; 79: I3-I12.
9. Higgins TL. Quantification rise and assessing outcome in cardiac surgery. J Cardiothorac Vasc Anesth. 1998; 12: 330-40.
10. Rathore SS, Epstein AJ, Volpp KGM, Krumholz HM. Hospital coronary artery bypass graft surgery volume and patient mortality, 1998 2000. Ann Surg. 2004; 239: 110-7.
11. Halpin LS, Barnett SD, Beachy J. Cardiac surgery outcomes. Outcomes Manag. 2003; 7: 144-7.
12. Nilsson J, Algotsson L, Hoglund P, Lührs C, Brandt J. Comparison of 19 pre-operative risk stratification models in open-heart surgery. Eur Heart J. 2006; 27: 867-74.
13. Edwards FH. Evolution of the Society of Thoracic Surgeons National Cardiac Surgery Database. J Invasive Cardiol. 1998; 10: 485-8.
14. Edwards FH, Clark RE, Schwarts M. Practical considerations in the management of large multi-institutional databases. AnnThorac Surg. 1994; 58: 1841-4.
15. Ribeiro ALP, Gagliardi SPL, Nogueira JLS, Silveira LM, Colosimo EA, Nascimento CAL. Mortality related to cardiac surgery in Brazil, 2000-2003. J Thorac Cardiovasc Surg. 2006; 131: 907-9.
16. Moraes F, Duarte C, Cardoso E, Tenório E, Pereira V, Lampreia D, et al. Avaliação do EuroSCORE como preditor de mortalidade em cirurgia de revascularização miocárdica no Instituto do Coração de Pernambuco (Brasil). J Cardiovasc Surg. 2006; 21: 29-34.
17. Peterson ED, Coombs LP, DeLong ER, Haan CK, Ferguson TB. Procedure volume as a marker of quality for CABG surgery. JAMA. 2004;291:195-201.
18. Torchiana DF, Meyer GS. Use of administrative data for clinical quality measurement. J Thorac Cardiovasc Surg. 2005: 129: 1223-5.
19. David TE. Should cardiac surgery be performed in low-volume hospitals? J Thorac Cardiovasc Surg. 2006; 131: 773-4.
20. Kurki TS, Häkkinen U, Lauharanta J, Rämo J, Leijala M. Evaluation of the relationship between preoperative risk scores, postoperative and total length of stays and hospital costs in coronary bypass surgery. Eur J Cardiothorac Surg. 2001; 20: 1183-7.
21. Toumpoulis IK, Anagnostopoulos CE, DeRose JJ, Swistel DG. Does EuroSCORE predict length of stay and specific postoperative complications after coronary artery bypass grafting. Int J Cardiol. 2005; 105: 19-25.
22. Fowler VG, O´Brien SM, Muhbaier LH, Corey GR, Ferguson B, Peterson ED. Clinical predictors of major infections after cardiac surgery. Circulation. 2005; 112 (Suppl I): I-358 I-365.