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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.51 no.4 Campinas 2001
Postoperative myocardial ischemia in patients undergoing abdominal aortic aneurysm repair. A retrospective study*
Incidência de isquemia miocárdica no pós-operatório de pacientes submetidos à cirurgia para correção de aneurisma de aorta abdominal. Estudo retrospectivo
Incidencia de isquemia miocárdica en el pós-operatorio de pacientes sometidos a cirugía para corrección de aneurisma de aorta abdominal. Estudio retrospectivo
Domingos Dias Cicarelli, TSA, M.D.I; Cristina Keiko Marumo, M.D.II; Ricardo Gonçalves Esteves, M.D.II
IIME2 do CET/SBA
BACKGROUND AND OBJECTIVES: Many
patients undergoing abdominal aortic aneurysm repair are at high risk for perioperative
myocardial ischemia. The great difficulty is to reliably evaluate the preoperative
risk of postoperative myocardial ischemia. This study aimed at observing the
incidence of postoperative myocardial ischemia in patients submitted to abdominal
aortic aneurysm repair, its correlation with Goldmans modified cardiac
risk index, with changes in the dipyridamole-thallium test and the risk factors
for such population.
METHODS: Participated in this retrospective study 65 patients submitted to abdominal aortic aneurysm repair. Risk factors, such as smoking, coronary artery disease, systemic hypertension and diabetes mellitus, were evaluated as well as the correlation among preoperative coronary artery disease, Goldmans modified cardiac index risk and postoperative myocardial ischemia. The correlation between preoperative dipyridamole-thallium test and postoperative cardiac complications was also evaluated.
RESULTS: Approximately 80% of patients were smokers, 55% were hypertensive, 8% had diabetes mellitus and 25% of patients presented with coronary artery disease. Among coronary artery disease patients, five patients had preoperative angina with an incidence of 40% of postoperative myocardial ischemia and 6.2% of myocardial infarction. In our study, 14% of Goldmans modified II and 33% of Goldmans modified III had postoperative myocardial ischemia. Sixteen patients (24%) were submitted to preoperative dipyridamole- thallium test and 10 patients (62%) presented reperfusion defects. Positive dipyridamole-thallium test predictive value was 20% for postoperative myocardial ischemia with a negative predictive value of 83% and sensitivity of 66%.
CONCLUSIONS: The incidence of cardiac complications as predicted by Goldmans modified index was not compatible with the theoretical risk of such index. Patients with preoperative angina had a high percentage (40%) of postoperative ischemia and dypiramidole-thalium test had a low ischemia-predicting value.
Key words: COMPLICATIONS: myocardial ischemia; SURGERY, Vascular
JUSTIFICATIVA E OBJETIVOS: Muitos
pacientes submetidos à cirurgia para correção de aneurisma de
aorta abdominal apresentam doença coronariana, podendo evoluir com complicações
cardíacas perioperatórias. A grande dificuldade é avaliar, no
pré-operatório, o risco de complicações cardíacas isquêmicas
que ocorrem no período pós-operatório de modo confiável.
O objetivo deste estudo foi verificar a incidência de isquemia cardíaca
pós-operatória em pacientes submetidos à correção de
aneurisma da aorta abdominal, sua correlação com o índice de
risco cardíaco de Goldman modificado, com alterações no teste
do tálio-dipiridamol e os fatores de risco nessa população.
MÉTODO: Foram analisados retrospectivamente 65 pacientes submetidos à correção de aneurisma da aorta abdominal e a incidência dos fatores de risco como tabagismo, insuficiência coronariana, hipertensão arterial sistêmica e Diabetes mellitus. Foi analisada a correlação entre a insuficiência coronariana no pré-operatório, o índice de Goldman modificado e as complicações isquêmicas pós-operatórias. Foi avaliada a correlação do teste tálio-dipiridamol pré-operatório e eventos isquêmicos no pós-operatório.
RESULTADOS: Cerca de 80% dos pacientes apresentavam antecedente de tabagismo, 55% de hipertensão arterial, 8% de Diabetes mellitus, 25% de insuficiência coronariana. Entre os pacientes com insuficiência coronariana, cinco possuíam angina pré-operatória e apresentaram uma incidência de 40% de isquemia miocárdica no pós-operatório, sendo a incidência de infarto agudo do miocárdio de 6,2%. No nosso estudo, 14% dos pacientes Goldman modificado II e 33% dos pacientes Goldman modificado III apresentaram isquemia miocárdica pós-operatória. Dezesseis pacientes (24%) foram submetidos ao tálio dipiridamol no pré-operatório, sendo que 10 (62%) apresentaram defeitos de captação cintilográfica. O valor preditivo positivo do exame foi de 20% para isquemia miocárdica pós-operatória, com valor preditivo negativo de 83% e sensibilidade de 66%.
CONCLUSÕES: A incidência de complicações cardíacas de acordo com o índice de Goldman modificado não foi compatível com o risco teórico desse índice. Os pacientes com angina no período pré-operatório apresentaram alta porcentagem (40%) de isquemia no pós-operatório, sendo que o valor do tálio-dipiridamol como teste preditivo de complicações isquêmicas foi baixo.
Unitermos: CIRURGIA, Vascular; COMPLICAÇÕES: insuficiência coronariana
JUSTIFICATIVA Y OBJETIVOS:
Muchos pacientes sometidos a cirugía para corrección de aneurisma
de aorta abdominal presentan enfermedad coronariana, pudiendo evolucionar con
complicaciones cardíacas perioperatorias. La gran dificultad es evaluar,
en el pré-operatorio, el riesgo de complicaciones cardíacas isquémicas
que ocurren en el período pós- operatorio de modo confiable. El objetivo
de este estudio fue verificar la incidencia de isquemia cardíaca pós-operatoria
en pacientes sometidos a corrección de aneurisma de la aorta abdominal,
su correlación con el índice de riesgo cardíaco de Goldman modificado,
con alteraciones en el test del tálio-dipiridamol y los factores de riesgo
en esa población.
MÉTODO: Fueron analizados retrospectivamente 65 pacientes sometidos a corrección de aneurisma de la aorta abdominal y la incidencia de los factores de riesgo como tabagismo, insuficiencia coronariana, hipertensión arterial sistémica y Diabetes mellitus. Fue analizada la correlación entre la insuficiencia coronariana en el pré-operatorio, el índice de Goldman modificado y las complicaciones isquémicas pós-operatorias. Fue evaluada la correlación del test tálio-dipiridamol pré-operatorio y eventos isquémicos en el pós-operatorio.
RESULTADOS: Cerca de 80% de los pacientes presentaban antecedente de tabagismo, 55% de hipertensión arterial, 8 % de Diabetes mellitus, 25% de insuficiencia coronariana. Entre los pacientes con insuficiencia coronariana, cinco tenian angina pré-operatoria y presentaron una incidencia de 40% de isquemia miocárdica en el pós-operatório, siendo la incidencia de infarto agudo del miocárdio de 6,2%. En nuestro estudio, 14% de los pacientes Goldman modificado II e 33% de los pacientes Goldman modificado III presentaron isquemia miocárdica pós-operatoria. Dieciséis pacientes (24%) fueron sometidos al tálio-dipiridamol en el pré-operatorio, siendo que 10 (62%) presentaban defectos de captación cintilográfica. El valor preditivo positivo del examen fue de 20% para isquemia miocárdica pós-operatoria, con valor preditivo negativo de 83% y sensibilidad de 66%.
CONCLUSIONES: La incidencia de complicaciones cardíacas de acuerdo con el índice de Goldman modificado no fue compatible con el riesgo teórico de ese índice. Los pacientes con angina en el período pré-operatorio presentaron alta porcentaje (40%) de isquemia en el pós-operatorio, siendo que el valor del tálio-dipiridamol como test preditivo de complicaciones isquémicas fue bajo.
The incidence of myocardial ischemia in patients submitted to abdominal aorta aneurysm repair is approximately 5% 1. Such incidence is decreasing during the last two decades due to coronary failure treatment evolution (myocardial revascularization, thrombolytic therapy, angioplasty). However, the search for a preoperative evaluation method with a high predictive value for perioperative myocardial ischemia is still ongoing. Cardiac risk evaluations, such as Goldmans index 2, are valid for large populations submitted to non-cardiac surgeries, but do not work for populations submitted to major vascular surgeries. Destky et al. 3 have modified such index, thus increasing its predictive value.
Several tests have been used to evaluate the presence and extension of coronary artery disease. Dypiramidole-thalium scintigraphy and stress echocardiogram with dobutamine have been recommended for patients unable to exercise especially those submitted to major vascular surgeries 4.
Dypiramidole-thalium screening test has been questioned and has a significant predictive value only for patients at moderate risk (1 or 2 risk factors) 5.
This study aimed at evaluating the incidence of myocardial ischemia in patients submitted to abdominal aorta aneurysm repair and the correlation between postoperative ischemic complications and risk factors, Goldmans modified cardiac risk index and reperfusion changes in the dypiramidole-thalium imaging.
After the institutions Research Ethics Committee approval, participated in this retrospective study patients submitted to elective abdominal aorta aneurysm repair, the postoperative period of whom was followed at the Surgical Support Unit of the Surgical Center, Hospital das Clinicas FMUSP, from January 1998 to December 1999. The following data were gathered from patients records: age, gender, weight, prescribed drugs, co-morbidities, such as systemic hypertension, diabetes mellitus, chronic obstructive pulmonary disease, previous stroke, coronary artery disease (myocardial infarction, myocardial revascularization, angioplasty, angina), ECG changes (left ventricular overload, Q waves, blockades), dypiramidole-thalium imaging changes (persistent or transient under-intake). Patients were classified according to Goldmans modified cardiac risk index. According to each patients classification, such index predicts cardiac complications risks, as shown in table I.
The presence of myocardial ischemia was evaluated and criteria for myocardial infarction diagnostic were 6:
· Electrocardiographic changes as from preoperative ECG: supra-unleveling of ST segment of at least 2 mm in 2 consecutive leads or the blockade of a branch not seen during preoperative evaluation;
· Clinical precordialgia or atypical pain of unknown etiology;
· Heart enzymes increase - CKMB corresponding to 5% of total CPK 7.
Myocardial infarction diagnosis was based on the presence of at least two criteria. Myocardial infarction deaths were confirmed by necropsy.
The association between risk factors and postoperative ischemic complications was analyzed by the chi-square test with Yates correction considering significant p < 0.05.
Positive and negative predictive values, sensitivity and specificity were evaluated for dypiramidole-thalium imaging.
Participated in this study 65 patients submitted to abdominal aorta aneurysm repair (53 infra-renal and 12 juxta-renal). Patients aged 53 to 77 years (67.9 ± 6.27), 50 were males and 15 females (77%/23%). Table II shows the incidence of risk factors in this population.
No risk factor presented a statistically significant association with postoperative ischemic complications. From the five patients with preoperative angina without previous invasive treatment (revascularization or angioplasty), two presented with ischemia (40%).
Six patients (9.23%) had postoperative ischemic events: 2 ischemias and 4 myocardial infarctions (MI) (6.15%) and three evolved to death.
Of the 65 patients, 31 were considered Goldman I and had no complications, 28 were considered Goldman II and had four ischemic complications (14%) and 6 were considered Goldman III with two ischemic complications (33%).
The relationship between preoperative ECG alterations (blockades, inactive areas and left ventricular overload) and ischemic complications was not statistically significant.
Only 16 patients were submitted to preoperative dypiradamole-thalium imaging. Of those, 11 had some type of scintigraphy uptake changes (8 with persistent and 3 with transient under-intake).
Tests positive predictive value was 20%, negative predictive value was 83% and sensitivity was 66%.
The incidence of myocardial ischemia was 9.23% in our sample. In 1995, Fleisher et al. 1 have found a 6% incidence of ischemic events in patients submitted to aorta surgeries, while Baron et al. 8, in 1994, reported an incidence of 18% in 457 patients submitted to the same surgery. This same study concluded that clinical evidence of coronary disease and more than 65 years of age were the risk factors with the highest predictive value for postoperative adverse cardiac events in this type of surgery. Our study was unable to show such risk.
According to Fleisher et al. 4, congestive heart failure (CHF) is associated to high perioperative risk. In our study, 50% of CHF patients died. This is in line with the literature, taking into consideration that all studied patients had ischemic CHF, which characterizes a higher perioperative risk. In the same study, Fleisher et al. have observed a high correlation between diabetes mellitus and perioperative cardiac morbidity. In our study, diabetes mellitus incidence was low (8%) and such relationship was not shown. Most prevalent risk factor in our sample was smoking (80%), being even higher than hypertension (55%).
Mangano et al. 9 have found 41% of postoperative myocardial ischemia in patients with coronary disease or at high risk for coronary failure submitted to elective non-cardiac surgeries. Such incidence is compatible with our findings of 40% of ischemic events in coronary disease patients without previous invasive treatment.
The real predictive value of Goldmans classification (cardiac risk) was also evaluated in our patients. We decided for Goldmans classification modified by Detsky for having a better correlation with postoperative complications. Even then, Goldmans modified theoretical risk has underestimated the actual risk of such patients. In our study, Goldman I and II patients presented two times more complications than the theoretical risk, So, we observed that the factors taken into account in Goldmans modified classification are few and do not accurately evaluate patients clinical status 10.
It is known that patients submitted to vascular surgeries are at high risk for coronary diseases. However, most are unable to exercise and pharmacological methods have been developed to simulate physiological exercise effects, such as dypiridamole-thallium imaging. Previous studies have shown a high predictive value for thallium (30-50%) with redistribution changes 11 for postoperative myocardial infarction. In 1991, Mangano et al. 12 have shown in a prospective study that there was no association between reperfusion defects and perioperative ischemia, with a positive predictive value of 27%. They suggested that postoperative adverse effects, especially myocardial infarction, were due to different causes, such as an increase in myocardial oxygen demand, thrombosis and other etiologies, not specifically tested by dypiramidole-thalium imaging. In 1994, Baron et al. 8 in a prospective study with 457 patients submitted to abdominal aorta repair confirmed that there is no association and that thaliums predictive value was 19%. Thaliums positive predictive value in our study is compatible with this result. So thalium is not routinely indicated for all patients to be submitted to major vascular surgeries.
Eagle et al. 5, in 1989, established a set of clinical variables (Q waves, ventricular ectopia history, diabetes mellitus, older age and angina) and have shown that in sub-groups with no risk factor or with multiple risk factors adverse events would be clearly predicted by clinical markers, and that scintigraphy would not bring additional information. However, a thallium test with reperfusion changes would be useful for moderate risk patients (1 or 2 risk factors). Scintigraphy with fixed defect represents morbidity for some authors 13,14. Thallium redistribution suggests that some fixed defect areas may represent severe ischemia with a high risk for myocardial necrosis during surgical stress.
In our study, all patients with preoperative thallium presented one or two risk factors. Considering reperfusion and fixed defects, dypiramidole-thallium had a positive predictive value of 20%, a negative predictive value of 83%, a sensitivity of 83% and a specificity of 38.5%.
Left ventricular hypertrophy and ST segment depression at preoperative ECG are important risk factors for myocardial infarction and cardiac death after major vascular surgeries 15. In our study, we have not found increased postoperative MI risk for preexisting ECG alterations evaluated, similar to what has been described by Sprung et al. 16.
To conclude, we have observed that the incidence of postoperative myocardial ischemia is high (40%) among cardiac patients with clinical manifestations (angina). Goldmans modified index has underestimated the risk for ischemic complications in patients submitted to abdominal aorta aneurysm repair. Among the risk factors evaluated, we have not seen correlation with postoperative cardiac events, probably due to the sample size. Positive dipyridamole-thallium predictive value for postoperative ischemic complications was low 17.
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Submitted for publication November 8, 2000 * Received
from CET/SBA da Disciplina de Anestesiologia do Hospital de Clínicas da
Faculdade de Medicina da Universidade de São Paulo
Accepted for publication Deciember 28, 2000
Submitted for publication November 8, 2000
* Received from CET/SBA da Disciplina de Anestesiologia do Hospital de Clínicas da Faculdade de Medicina da Universidade de São Paulo