Clinical Profile, Predictors of Mortality, and Treatment of Patients after Myocardial Infarction, in an Academic Medical Center Hospital

Original Article

Clinical Profile, Predictors of Mortality, and Treatment of Patients after Myocardial Infarction, in an Academic Medical Center Hospital

Leonardo A. M. Zornoff, Sérgio A. R. Paiva, Vanessa M. Assalin, Patrícia M. S. Pola, Luís E. Becker, Marina P. Okoshi, Luiz S. Matsubara, Roberto M. T. Inoue, Joel Spadaro

Botucatu, SP - Brazil

OBJECTIVE: To evaluate clinical profiles, predictors of 30-day mortality, and the adherence to international recommendations for the treatment of myocardial infarction in an academic medical center hospital.

METHODS: We retrospectively studied 172 patients with acute myocardial infarction, admitted in the intensive care unit from January 1992 to December 1997.

RESULTS: Most patients were male (68%), white (97%), and over 60 years old (59%). The main risk factor for coronary atherosclerotic disease was systemic blood hypertension (63%). Among all the variables studied, reperfusion therapy, smoking, hypertension, cardiogenic shock, and age were the predictors of 30-day mortality. Most commonly used medications were: acetylsalicylic acid (71%), nitrates (61%), diuretics (51%), angiotensin-converting enzyme inhibitors (46%), thrombolytic therapy (39%), and beta-blockers (35%).

CONCLUSION: The absence of reperfusion therapy, smoking status, hypertension, cardiogenic shock, and advanced age are predictors of 30-day mortality in patients with acute myocardial infarction. In addition, some medications that are undoubtedly beneficial have been under-used after acute myocardial infarction.

Key words: myocardial infarction, mortality, treatment

Acute myocardial infarction is responsible for a great number of hospital stays all over the world and for a great number of deaths ^1,2. Several variables have been used to predict the evolvement and to guide the treatment of patients with acute myocardial infarction. Those that stand out are age, sex, hypertension or hypotension, diabetes, size and location of the infarction, hypotension, ventricular dysfunction, left ventricle dimensions, and the level of neurohormonal activation ^3-5.

In recent years, new therapeutical interventions were introduced based on the evidences of major clinical trials that reduced morbidity and enhanced survival after acute myocardial infarction. Among these strategies, are the use of reperfusion therapy, antiplatelet agents, angiotensin-converting enzyme inhibitors, and beta- blockers ^6-9 .

However, reports from the literature suggest that a great number of patients with acute myocardial infarction may not be receiving the recommended treatment ^10-12. This phenomenon may be due to the characteristics of the hospitals in which the patient with the myocardial infarction is admitted, as well as patient's peculiarities ^13,14.

This study aimed at evaluating the clinical profile of patients with a diagnosis of acute myocardial infarction, seen at an academic medical center hospital in the countryside area of the State of São Paulo. Additionally, we have assessed the adherence to current recommendations for the treatment of acute myocardial infarction, and identified the variable predictors of 30-day mortality after admittance.

Methods

We retrospectively assessed the charts of patients admitted to the intensive care unit of the Hospital das Clínicas da Faculdade de Medicina de Botucatu, UNESP, from January 1992 to December 1997. In this period, 211 patients were admitted with acute myocardial infarction, confirmed by combinations of precordial pain and/or electrocardiographic alterations and a serum increase of in cardiac enzymes. After reviewing the charts, we selected 172 patients who had the necessary information required for the study protocol.

Regarding clinical profiles, data were obtained from the history and physical examinations at admission. Study variables were: age, sex, race, heart rate, systemic blood pressure, electrocardiographic location of the infarction (anterior, inferior, other), and cardiac enzymes.

With respect to risk factors, family history was investigated, as well as smoking status, and also the occurrence of hypertension, diabetes, and dyslipidemia. These variables were classified as traditional risk factors. Positive family history included those who had first-degree relatives or 2 previous generations. Smokers were defined as those patients who smoked daily regardless of the number of cigarettes smoked. Diabetes patients were classified as those who, in previous examinations and during admittance, had a fasting blood glucose concentration compatible with the diagnosis. Hypertension was considered in those who had this diagnosis prior to the acute myocardial infarction. Dyslipidemia was determined by the presence of increased serum levels of low density lipoproteins and/or decreased serum levels of high density lipoproteins. The risk factor obesity was not included due to this variable not being indicated in the chart.

Concerning the complications experienced by the patients during their stay in the intensive care unit, the diagnoses that were found in the charts were accepted. If certain information, such as report of cardiogenic shock or congestive heart failure, was missing, it was considered as nonexistent.

The 10 most frequently prescribed classes of medication during admittance in the intensive care unit were evaluated concerning the percentage of use, considering only those drugs used for at least 48 hours.

Regarding the statistical analysis, patients were divided into 2 groups, survivors and nonsurvivors. To study continuous variables, we used the student's t test and Mann-Whitney test, whereas, to study dichotomous variables, we used the chi-square test. Variables that could predict the patients' evolvement during the one-month follow-up period were identified using a multivariable analysis (multiple logistic regression study). P<0.05 was considered statistically significant.

Results

Duration of precordial pain, from the onset of symptoms up to the moment of the first assessment in the emergency room, was 10.6±15 hours. The characteristics of the patients when diagnosis of acute myocardial infarction was obtained are shown in table I. The analysis of the charts allowed determination of the race of 159 patients, the blood pressure (diastolic, systolic, and mean) of 171 patients, and the heart rate of 161 patients. The other variables could be recovered in 172 patients. In the 30-day period after admittance to the intensive care unit, the statistical analysis of those variables demonstrated that the mortality rate was higher in older patients (69.7+9.6 years) than in younger ones (58.8+11.1 years) (P<0.001). Likewise, surviving patients had heart rates statistically lower on admission than those who died later. The other variables, sex, race, blood pressure, creatine kinase (CK), MB isoenzymes (CKMB), and location of the infarction were not statistically different between the two groups. During the 30-day observation period, 39 (22%) patients died.

Variables that are usually used as indicators of a poor prognosis after myocardial infarction are listed in table II. Some data were statistically different between the surviving and deceased patients. Of the deceased patients, 43.6% (17 out of 39) had cardiac arrhythmias, but only 22.6% (30 out of 133) of the surviving patients had sustained arrhythmias (P=0.02). Cardiogenic shock was seen in 43.6% (17 out of 39) of the deceased patients and in 2.3% (3 out of 133) of the surviving patients (P=0.001).

Table III

Among all the variables studied (clinical features, risk factors, complications, and treatment), the use of thrombolytic therapy and smoking resulted in higher survival rates in the 30-day period. On the other hand, systemic blood hypertension, cardiogenic shock, and advanced age resulted in increased mortality in the study period (fig. 1).

Discussion

The main findings of our study, in which we analyzed clinical profiles, predictors of 30-day mortality, and the treatment of patients with acute myocardial infarction in an academic medical center hospital, were 1) 30-day mortality was 22%; 2) patients with acute myocardial infarction have the same clinical profile in small cities as patients in the great urban areas; 3) thrombolytic therapy, smoking status, hypertension, cardiogenic shock, and age were the predictors of 30-day mortality; 4) drugs recommended as standard treatment of for acute myocardial infarction, such as thrombolytic therapy, acetylsalicylic acid, and beta-blockers, are underused; 5) drugs used for the treatment of congestive heart failure after acute myocardial infarction, such as diuretics, nitrates, angiotensin-converting enzyme inhibitors, and inotropic drugs, are prevalent.

The clinical profile of the patients in this study was similar to those of other studies ^14,15. The duration of precordial pain is an important fact and has clinical implications. In our study, the mean time of pain was greater than 10 hours from the onset of the symptoms to the first assessment in the emergency room. This is probably because our hospital is a referral center in the countryside area of São Paulo State and receives patients from several regions of São Paulo and from other states. Therefore, this reflects characteristics both from our service and from the patients we see. An immediate result of this phenomenon was the relatively low percentage of patients who underwent reperfusion therapy (39%), which is similar to results reported in other studies ^13,16. In an analysis of 2,409 patients, in which 30% fulfilled the criteria for reperfusion therapy, only 72% of them received this treatment ¹⁶. These studies suggest that although this treatment is undoubtedly beneficial ¹⁷, many factors exist turning it of difficult access for acute myocardial infarction patients. This fact results in lower adherence to the treatment compared to international recommendations for the administration of reperfusion therapy after acute myocardial infarction ¹⁸.

We considered the following traditional risk factors as risk factors for atherosclerotic coronary disease: hypertension, smoking, dyslipidemia (increased serum levels of low density lipoproteins, decreased serum levels of high density lipoproteins), male gender, and diabetes mellitus. However, in recent years, other risk factors have been identified, for example lack of exercise, obesity, fibrinogen alterations, and other serum lipids alterations, and genetic factors ¹⁹. The participation of these factors in atherosclerosis has been increasingly valued: only 6.3% of our patients did not have at least one traditional risk for atherosclerotic disease.

Our study confirmed that, the absence of reperfusion therapy, presence of hypertension, cardiogenic shock, and advanced age are independent factors associated with greater mortality, in 30 days, in patients with acute myocardial infarction. A paradoxical association was verified between history of smoking and lower mortality after infarction. Although smoking is a recognized risk factor for atherosclerotic disease, regarding acute myocardial infarction, infarction smoking patients are, on average, 10 years younger than nonsmoking patients, therefore, having fewer risk factors such as ventricular dysfunction ²⁰. This fact could explain the occurrence of lower mortality in smokers compared to nonsmokers in our study, because many variables was not included in our multivariable analysis.

Our study showed that beta-blocking agents are still underused, despite the evidences of its beneficial use after myocardial infarction, even in the presence of ventricular dysfunction ^9,21,22. These data are in accordance with that of previous studies ^11,13,14, suggesting the presence of some resistance by the physicians with this class of drugs.

Regarding angiotensin-converting enzyme inhibitors, although clinical studies confirm unquestionable benefits when administered in patients with ventricular dysfunction ^23,24, favorable evidences exists of its use in all patients after acute myocardial infarction ^25,26. In our analysis, 46% of the patients received this drug during their hospital stay in the intensive care unit.

On the other hand, medications usually prescribed to treat congestive heart failure after acute myocardial infarction (nitrates, angiotensin-converting enzyme inhibitors, diuretics, and inotropic drugs) were used in a large number of our patients. This fact may be a consequence of the characteristics of our intensive care unit. Due to the small number of rooms, patients whose risk stratification indicates a high probability of complications, after acute myocardial infarction, are admitted to the intensive care unit. Thus, our patients had more severe clinical conditions than usual, requiring some particularities concerning the treatment. This would also explain the high mortality (22%) rate observed in our study in the 30-day period after acute myocardial infarction.

Some factors should be considered when interpreting our results. First, our study includes only patients enrolled between 1992 and 1997. In this period, many of the important clinical trials and international recommendations on the treatment of acute myocardial infarction had not been published. Another important point is the fact that we studied only the treatment performed during the stay in the intensive care unit, and we did not study the treatment performed during the period in the hospital or the ambulatory treatment.

In conclusion, our study confirmed that the absence of reperfusion therapy, presence of smoking, hypertension, cardiogenic shock, and advanced age are predictors for 30-day mortality in patients with acute myocardial infarction. Additionally, our results showed that some medications, which have been proved to be beneficial, are still underused after myocardial infarction, confirming a distortion between randomized studies and international recommendations and clinical practice, including an academic medical center hospital. The reasons for this phenomenon are still unknown, but our results highlight the need of discussing and of disclosing the issue to obtain greater adherence to the internationally recommended conduct.

Faculdade de Medicina de Botucatu - UNESP

Mailing address: Leonardo A. M. Zornoff - Depto. de Clínica Médica - Faculdade

de Medicina de Botucatu - Rua Rubião Júnior S/N - 18618-000 - Botucatu, SP

E-mail: [e-mail]

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Publication Dates

• Publication in this collection
  31 Jan 2007
• Date of issue
  Apr 2002