The Streptokinase Therapy Complications and its Associated Risk Factors in Patients with Acute ST Elevation Myocardial Infarction

Introduction

In 1998, adverse drug reactions (ADRs) were known as 4-6^th leading cause of mortality in the U.S with a cost for health care system (1). Furthermore, in the United Kingdom, data showed that 1 of 16 hospital admissions was associated to ADRs with the annually cost of up to £466 million. In addition, ADRs were responsible to 0.15% of in-hospital mortalities (2). Therefore, detection and prevention of ADRs play an important role in improvement of treatment outcomes.

Streptokinase, a metabolic product of beta-hemolytic streptococci, is an indirect fibrinolytic agent that interacts with plasminogen and forms an active complex with the protease activity that transforms plasminogen to plasmin (3).

The mortality benefit of streptokinase in patients with acute myocardial infarction (AMI) has been illustrated in large, placebo-controlled trials (4, 5).

In GISSI-1, the first largest thrombolytic trial evaluated streptokinase therapy versus no treatment in AMI patients, the significant mortality benefit of streptokinase has been documented as following: 8.2% versus 15.4% for patients received streptokinase within 1 hours of onset of symptoms, 9.2% versus 12% within three hours and 11.7% versus 14.1% in those treated between 3-6 h (4). In ISIS-2 trial, the similar benefits of streptokinase were also noted in over 17,000 patients presenting with symptom of acute MI within 24 h (5). Despite the mortality benefits of streptokinase in AMI patients, it includes some adverse reactions such as allergic reactions, hypotension, and bleeding.

Streptokinase is a non-human protein, and its presentation into the circulatory system can lead to severe anaphylactic responses including death (6, 7). The risk of this immune response is dependent to the level of the anti-streptokinase antibodies in circulation. This immunogenicity limits multiple treatments with streptokinase (8, 9).

Because of the critical condition of patients with AMI and complications of streptokinase therapy, this study was performed to evaluate the pattern of adverse drug reactions induced by streptokinase therapy and its associated risk factors in patients with acute ST elevation MI (STEMI).

Experimental

Study design and setting

A prospective cross-sectional study was performed in Shahid Madani Heart Center, the largest referral center for cardiovascular disorders at the north-west of Iran for a period of 14 months. The study was approved in the ethics committee of the university.

Sample size calculation

Based on data from our center, about 400 patients with acute STEMI have been receiving thrombolytic therapy each year. Assuming the 95% confidence interval and α = 0.05 the sample size will be 210 patients with a standard error of 0.025 during 14-month study period.

Inclusion and exclusion criteria

The patients’ eligibility criteria included the age of over 18 years old with a diagnosis of acute STEMI who candidate for receiving streptokinase.

Exclusion criteria included acute or chronic kidney and liver disease, pregnant women and patients not able to continue the study, and contraindications of thrombolytic therapy including recent head/facial trauma and/or ischemic stroke within last 3 months, intracranial tumor, and prior intracranial hemorrhage, suspected aortic dissection, active internal bleeding, or bleeding diathesis and severe uncontrolled hypertension.

Streptokinase injection method

The streptokinase was administered as soon as possible after the first symptoms of STEMI (under the six hours from onset of symptoms) with the usual adult dose of AMI as 1,500,000 units intravenous (IV) infusion over 60 min. In case of allergic reactions and fever, it was recommended that patients concurrently should receive corticosteroids that can be repeated during treatment. Before treatment, the patient PT and PTT were being controlled. In case of anaphylactic shock symptoms and hypotension, malaise, chills, nausea and arrhythmia, the infusion was being stopped.

Detection and classification of ADRs

All patients receiving streptokinase that had completed the informed consent form were monitored for ADRs induced by streptokinase. Detection and monitoring of ADRs were done through completing a questionnaire by reviewing the patientsꞌ medical file and documentation as well as interviewing with the patients.

The questionnaire includes the demographic information, past medical history, drug history, familial, habitual and social history, laboratory and echocardiographic information.

The Naranjo probability scale was used to causality assessment of ADRs as follows: The scores between 1-4 ranked as possible, 5-8 ranked as probable and > 9 ranked as highly probable. The score of < 0 was deemed as doubtful ADR (10). Based on the FDA classification, the severity of ADRs was categorized in four levels: 1) mild: no need to treatment, 2) moderate: need to specific treatment, 3) severe: cause to prolonged hospitalization, 4) very severe: potential life-threatening or contribute to the death.

Data analysis

Data analysis was performed using SPSS 16.0 (Chicago, SPSS Inc., 2007). The Kolmogorov-Smirnov test was utilized to determine the normally distribution of data. The correlation evaluation between ADRs and the study parameters was done using Spearman test. The linear regression (Stepwise method) and logistic regression analysis were performed to find out any relationships between the incidence and number of ADRs and the study independent risk factors. Continues data were presented as mean ± standard deviation (SD). P-values less than 0.05 were considered statistically significant.

Results

During the 14-month study period, 217 patients who received streptokinase entered the study. The majority of patients were male (n = 178, 82%). The mean age of study population was 60.5 ± 12 years old. A total of 6 deaths occurred during the study period.

In this research, 54.9% of patients experienced the anterior MI. Inferior and lateral MI were also found in 44.6% and 0.5% of the patients, respectively.

The number of ADRs experienced by patients was between 0 and 8. In average, each patient experienced 2.3 ± 1.7 ADRs. Furthermore, the incidence of ADRs between females and males were 2.6 versus 0.63 indicating the higher rate of ADR (4.2 times more) among female patients.

The most common ADRs were chest pain, hypotension, coughing, and ecchymosis with the frequency of more than fifty percent. The hemorrhagic stroke as the most serious ADR of streptokinase was documented in three patients. In Table 1. the patientsꞌ demographics and clinical data are presented. Also, the frequency of documented ADRs was presented in Table 2.

According to the Naranjo scale, the most ADRs ranked as “probable” (Table 3). Based on the FDA severity classification of ADRs, the most ADRs were categorized in mild to moderate ADR (Table 4).

The results of Spearman analysis showed that the incidence of ADRs by streptokinase was associated with the female gender (r = 0.136; p =0.046), history of allergy (r = 0.160; p =0.018), hyperlipidemia (r = 0.174; p =0.010), history of pulmonary thromboembolism (PTE) (r = 0.184; p =0.006), location of MI (r = 0.143; p =0.047), low Ejection fraction (EF) (r = -0.150; p =0.031) and history of polypharmacy (r = 0.154; p =0.023). Furthermore, the number of ADRs was linked with the age (r = 0.136; p =0.045), female gender (r = 0.152; p =0.025), incidence of ventricular fibrillation (VF) (r = 0.205; p =0.002), history of allergy (r = 0.143; p =0.036) and use of anti-coagulant agents (r = 0.163; p =0.017) (Table 5).

The linear regression analysis showed the three models of correlation between the incidence of ADRs and study risk factors including age, history of allergy, history of percutaneous coronary intervention and dyslipidemia (Table 6). In the linear regression model, a significant correlation between the number of ADRs and use of anti-coagulant agents, low hemoglobin level and age of patients was documented (Table 7).

The logistic regression analysis showed the history of allergy as the main predictor in the incidence of streptokinase ADRs (Odds ratio: 3.26, 95% CI: 1.48-457.6; p =0.026).

Discussion

This study evaluated 217 patients with acute ST-elevation MI who received streptokinase. The main finding of this research may be that the history of drug allergy was the main predictor in the incidence of ADRs induced by streptokinase. Furthermore, hypotension was one of the most occurred ADR that may be associated with the rapid injection of the drug. Moreover, in this study hemorrhagic stroke and bleeding complications was higher than the other reports. Although, no case of anaphylactic shock was documented.

In our study, the incidence of ADRs by streptokinase was reported 82% that is substantially higher than the other reports. For example, in Devi et al. retrospective cohort study and Mohebbi et al. prospective study that were conducted in coronary care unit (CCU), the highest ADRs were seen by streptokinase in about 60% (11, 12). However, this rate is similar to our recent study on reteplase with the incidence rate of 85% (13).

Several studies have described the history of allergy as one of the predisposing factors in occurring ADRs. Hurwits et al. (14) in a prospective drug surveillance study of 1160 hospitalized patients showed that there was a significant relation between incidence of ADRs during the hospitalization and history of allergy among 118 patients. In the present study, the logistic regression analysis indicated drug allergy with the odds ratio of 3.26 as a predisposing factor in occurring of ADR by streptokinase.

One of the most occurred ADR was hypotension that may linked with the rapid injection of the drug. According to the previous studies, hypotension during streptokinase injection is a vasodilatory effect that is occurred by activation of plasmin and producing bradykinin (15, 16). The rate of hypotension during streptokinase therapy was reported between 1-10% that is relatively lower than our study finding (more than 50%) which can reflect the rapid injection of streptokinase (17). In the recent review of Iranian literature, hypotension and arrhythmia were identified as the most frequent ADRs induced by streptokinase that is in agreement with our findings (18).

Hemorrhagic stroke was the most severe side effect that occurred during hospitalization after the injection of streptokinase by documenting in 3 cases (1.4%). However, the incidence of hemorrhagic stroke in these patients substantially was higher than the other reports. In a prospective and spontaneous reporting-based pharmacovigilance program in Cuba among 792 patients who received streptokinase, the hemorrhagic stroke were reported only in 3 cases (0.3%) (19). In GISI-1 and ISIS-2 trials the incidence of major bleeding such as hemorrhagic stroke was reported between 0.3-0.5% (4, 5). Moreover, in Maggioni et al. (20) study, the incidence of various forms of stroke in patients treated with streptokinase was 0.94 %. Many factors including drug related factors such as bleeding complications as well as host related factors such as older age, female gender, anterior MI, history of smoking and hypertension are the main participating factors in occurring stroke (20).

Several studies have described the role of gender in the incidence of ADRs. In the analysis of 48 cohort studies with 513,606 patients in UK, females were more likely to experience ADRs (60% more than males) (21). Also, according to the Hurwits and Seidl et al. studies female patients are more likely than men to experience ADRs (13, 22). Similarly, in our study the incidence of ADRs in females was more than males that is in agreement with the earlier reports.

Moreover, our study indicated that the number of side effects increased along with the increasing age that is consistent with the numerous previous reports. Ageing related decrease in kidney and liver function may be one of the responsible factors (23, 24). Existence of various underlying diseases and poly pharmacy are the other participating factors that put the older patients to experience more ADRs (23, 24).

The significant correlation between the incidence of ADRs and underlying diseases such as hyperlipidemia, VF, PTE was the other finding of present study that is in line with the other reports, which had indicated the background diseases as a main predictor in the incidence of ADRs (1).

Limitations and strengths

Despite the acceptable sample size of the study (n = 217), the major limitation in such studies is the partially small sample size. In fact, for precise detection and evaluation of all ADRs induced by a special drug a large sample size (more than 10,000) are needed. Second, present study included the relatively weak correlation coefficient that may be linked to this matter. Therefore, the result of this study should be interpreted with a caution. This study also included some key findings as strength points. First, it showed that the patients with history of drug allergy 3.2 times are more vulnerable to show one ADRs by streptokinase. This result could guide clinicians to use streptokinase with a caution in patients with the history of drug allergy. Second, the rate of hemorrhagic stroke in Iranian population is relatively higher than the other reports. This point along with the lower efficacy of streptokinase in the maintaining of thrombolysis in myocardial ischemia (TIMI) III flow may discourage the use of streptokinase by clinicians.

In summary, our study showed that the history of drug allergy is the main predictor in occurring ADRs by streptokinase. Furthermore, streptokinase therapy was associated with a higher rate of hemorrhagic stroke in Iranian population.