The Prognostic Significance of QRS Duration in Patients with ST-Segment Eleva- tion Myocardial Infarction Receiving Thrombolytic Therapy

Prolongation of the QRS duration has been shown to be associated with adverse outcomes post-myocardial infarction (MI). The relation to thrombolytic therapy was not widely studied before. The study included 30 patients with ST-segment elevation myocardial infarction who were given thrombolytic therapy. Results: ST segment deviation score (STD score) ranged from 5 to 23 with a mean of 14. ECG one hour after thrombolysis showed: Number of patients with successful thrombolytic therapy was sixteen (53.3%). ECG one day after thrombolysis showed: ST segment deviation score ranged from 0 to 10. QRS minimum duration ranged from 84 to 117 msec with a mean of 100. QRS maximum duration ranged from 85 to 118 msec with a mean of 102 msec. ECG measurements were repeated after thrombolytic therapy by one hour, 1 day, 2 days and on discharge. The 30 patients included in this study were divided into three groups according to the QRS maximum duration. The relation between QRS max before thrombolysis and the incidence of successful thrombolysis: Number of patients with successful thrombolytic therapy was not different in relation to QRS duration. QRS duration was compared with complications. Comparison between the success of the thrombolysis and the change of the QRS max before thrombolysis and before discharge showed that the shortening of the QRS duration in patients with successful thrombolysis was significant. Conclusion: improvement of QRS duration is a marker of successful thrombolysis. The incidence of complications (arrhythmias, heart failure, shock, pulmonary edema, mortality) increases with the increase of the QRS duration.


Introduction
Impaired reperfusion after acute myocardial infarction (MI), known as the no-reflow phenomenon, is associated with greater left ventricular dysfunction and increased risk of death [1]. So, differentiation of a subgroup of acute MI patients who did get successful fibrinolytic therapy by means of a non-invasive diagnostic tool is of practical importance.
The post fibrinolysis electrocardiogram (ECG) has shown promise as a non-invasive reperfusion marker, electrocardiographic assessment of reperfusion is mostly based solely on changes of the ST segment. In contrast, a poor prognostic value of QRS prolongation in acute STEMI settings has been shown in previous studies [2]. There are few reports evaluating the relationship of QRS duration with myocardial reperfusion [3].

Aim of the Work
The aim of this study is to evaluate the importance of the QRS duration and its relations to the mechanical performance of the heart as well as its prognostic significance in patients presented to Critical Care Department with STsegment elevation MI who received thrombolytic therapy.

Patients and Methods
Patients: This  • Presence of a cerebral vascular malformation or a primary or metastatic intracranial malignancy.
• Symptoms or signs suggestive of an aortic dissection.
• A bleeding diathesis or active bleeding, with the exception of menses; thrombolytic therapy may increase the risk of moderate bleeding, which is offset by the benefits of thrombolysis.
• Significant closed-head or facial trauma within the preceding three months.
Relative contraindications: History of chronic, severe, poorly controlled hypertension or uncontrolled hypertension at presentation (blood pressure < 180 mmHg systolic and/ or < 110 mmHg diastolic; severe hypertension at presentation can be an absolute contraindication in patients at low risk.
• History of ischemic stroke less than three months previously.
• Any known intracranial disease that is not an absolute contraindication.
• Major surgery within the preceding three weeks.
• Current warfarin therapy -the risk of bleeding increases with increased INR.
• For streptokinase or anistreplase -a prior exposure (more than five days previously) or allergic reaction to these drugs.

Monitoring
Patients had been monitored and followed up till discharge regarding: a. Vital signs, chest and heart examination.

Echocardiographic measurements
In all subjects, two-dimensional, M-mode pulsed and Parasternal long-and short -axis, apical four, and two chamber views were obtained echocardiographic examinations were performed. Internal left ventricular (LV) end-diastolic and end -systolic diameters and interventricular septal and posterior wall thickness at end-diastole, and left atrial dimension were measured from parasternal long axis window in M-mode echocardiography. The ejection fraction of the left ventricle was obtained using modified Simpson's method.

Hospital course and complications:
In-hospital complications have been documented, including cardiac arrhythmia, congestive heart failure, cardiogenic shock, cardiac arrest, and death.
The study was approved by the local ethics committee of the institution, and all patients gave written informed consent. The data was collected in spreading sheets then they had been analyzed statistically in a diagrammatic way.
The success of the thrombolysis was based upon the following: • More than 50 percent ST-segment resolution.
• Resolution of the chest pain taking into consideration the use of analgesics.
• Presence of reperfusion arrhythmias particularly accelerated idioventricular escape rhythm. with a mean of [7].  (Table 1) ECG was done for all patients on presentation and before thrombolysis and showed:

Demographic Data
• Heart rate ranged from 60 to 130 beat per minute, mean 88.77 ± 17.6.
ST segment deviation score (the sum of ST segment deviation in all 12 leads).
• (STD score) was calculated for all patients and it ranged from 5 to 23 with a mean of 14.83 ± 4.24 • QRS complex parameters were measured for all cases. QRS minimum duration ranged from 84 to 117 msec with a mean of 101 + 11. QRS maximum duration ranged from 85 to 118 msec with a mean of 102 + 11 msec.
• QTc was measured ranged from 0.400 to 0.440 sec with a mean of 0.420 ± 0.01 sec.
ECG findings one hour after thrombolysis (table 1): ECG was done for all patients one hour after thrombolysis and showed: • Number of patients with successful thrombolytic therapy was sixteen (53.3%).
• Heart rate ranged from 60 to 110 beat per minute with a mean of 80 bpm.
ST segment deviation score (STD score) ranged from 1 to 19 with a mean of 7.
• QRS minimum duration ranged from 84 to 117 msec with a mean of 101 and QRS maximum duration ranged from 85 to 118 msec with a mean of 102 msec.
ECG findings one day after thrombolytic (table 1): ECG was done for all patients one day after thrombolysis and showed: • Heart rate ranged from 60 to 110 beat per minute with a mean of 79 beat per minute.
• ST segment deviation score (STD score) ranged from 0 to 10 with a mean of 1.83 • QRS minimum duration ranged from 84 to 117 msec with a mean of 100+11 QRS maximum duration ranged from 85 to 118 msec with a mean of 102 msec.
QTc was measured ranged from 400 to 440 msec with a mean of 420 msec.
ECG findings two days after thrombolytic (table 1): ECG was done for all patients two days after thrombolysis and showed: • Heart rate ranged from 60 to 120 beat per minute with a mean of 78.
• ST segment deviation score (STD score) ranged from 0 to 6 with a mean of 1.23 • QRS minimum duration ranged from 84 to 117 msec with a mean of 100 QRS maximum duration ranged from 85 to 118 msec with a mean of 101 • QTc was measured ranged from 40 to 44 msec with a mean of 42.0 1 1.0 msec.
ECG findings before discharge (table 1): ECG was done for all patients before discharge and showed: • Heart rate ranged from 60 to 120 beat per minute with a mean of 77.
• ST segment deviation score (STD score) ranged from 0 to 2 with a mean of 0.67 • QRS minimum duration ranged from 84 to 117 msec with a mean of 100.
QRS maximum duration ranged from 85 to 118 msec with a mean of 101 QTc was measured ranged from 40 to 44 msec with a mean of 42 msec.
-EDD :( end diastolic diameter) ranged from 4 to 6.9 cm with a mean of 5.7 + 0.7 cm.
-Left atrium diameter ranged from 34 to 42 mm with a mean of 37.
Relation between QRS max before thrombolysis and gender: • There was statistically insignificant difference between the three groups as regards the gender of patients (p = 1.000).
Relation between QRS max before thrombolysis and risk factors: Comparison between the three groups before the thrombolytic therapy as regards the risk factors revealed that :there was statistically insignificant difference between the three groups as regards the history of smoking (p=0.2l2).
There was statistically insignificant difference between the three groups as regards the history of dyslipidemia (p=O.249).
There was statistically significant difference between the three groups as regards the history of diabetes mellitus, more patients with DM were found in group C (p=0.049).
• There was statistically insignificant difference between the three groups as regards the history of previous Ml (p=0.202).
There was statistically insignificant difference between the three groups as regards the history of hypertension (p=0.085).
Relation between the site of infarction and QRS max and QRS min before thrombolytic therapy: and two (50%) in lateral leads (I, aVL).
Comparison between the site of the infarction and the QRS max and the QRS min before thrombolysis revealed that: There was statistically insignificant relation between the site of the infarction and leads that shows maximum duration of the QRS complex in ECG before thrombolysis (p=0.372).
• And also there was statistically insignificant relation between the site of the infarction and leads that shows minimum duration of the QRS complex in ECG before tl1r0mb0lysis (p=0.795).
So leads that show the QRS min or QRS max had no relation to the site of infarction.
Relation between QRS max before thrombolysis and the incidence of successful thrombolysis: Number of patients with successful thrombolytic therapy in (group A) was three (18.8%), in (group B) was ten (62.5%), while in (group C) was three (18.8%). There was statistically insignificant difference between the three groups as regards the number of patient with successful thrombolytic therapy (p = 0.603).
Relation between the success of the thrombolysis and the change of the QRS max before thrombolysis and before discharge. (Table 3) The duration of the QRS max before thrombolytic therapy in patients with failed thrombolysis ranged from 88.0 to 118.0 msec with a mean of 106 + 10 msec and before discharge ranged from 88.0 to 118.0 msec with a mean 105+l0 msec.
The duration of the QRS max before thrombolytic therapy in patients with successful thrombolysis ranged from 85.0 to 118.0 msec with a mean of 106.14 ± 10.52 msec and before discharge ranged from 85.0 to 116.0 msec with a mean 98.75 ± 11 msec.
• There was statistically significant difference between the QRS max before thrombolysis and before discharge in patients with successful thrombolysis (p=0.041). The shortening of the QRS duration in patients with successful thrombolysis is statistically significant.
• There was statistically insignificant difference between the QRS max before thrombolysis and before discharge in patients with failed thrombolysis (p=0.174).
Relation between the three groups as regard the ECG parameters before thrombolytic therapy:  Relation of QRS max before discharge and Echo before discharge: Table 4 Ejection fraction in (group A) ranged from 50 to 60% with a Relations between QRS max before thrombolysis and complications: ( No patient had died in (group A) and (group B) while two patients (25%) died in (group C).
• There was statistically significant difference between the three groups as regards the incidence of arrhythmias (p=0.001).
Heart failure was more with wider QRS (p<0.001).
• There was statistically significant difference between the three groups as regards the incidence of shock (p=0.093).
• There was statistically significant difference between the three groups as regards the incidence of developing pulmonary edema (p=0.003). • There was statistically insignificant difference between the three groups as regards the incidence of mortality (p=0.084).
And with doing a comparison test (student t test) to show the difference between the means of the QRS max in patients with and patients without complications we found that: There is a statistically significant difference between the mean of the QRS max in patients with and patients without complications with p value (<0.00l), as the incidence of complications (arrhythmias, heart failure, shock, pulmonary edema and mortality) increases with the increase in the QRS max (table   5).
There is a statistically significant difference between the mean of the QRS max in patients with and patients without complications with p value (<0.001), as the incidence of complications (arrhythmias, heart failure, shock, pulmonary edema and mortality) increases with the increase in the QRS max

Discussion
Effect of thrombolytic therapy on the QRS max: Comparing the ECG before discharge with the ECG on admission in our study, there was a significant change of the QRS duration (shortening) in patients with successful thrombolysis while there was no significant difference between the QRS duration before thrombolytic therapy and before discharge in patients with failed thrombolytic therapy.
Orhan et al, [13] in a study to show the effect of successful reperfusion on QRS duration conducted on ninety-two consecutive patients with acute ST-segment elevation myocardial infarction who underwent successful primary angioplasty. They found improvement in QRS in reperfusion group, and they suggested the use of QRS changes for assessment of cellular reperfusion [13].
Tsukahara et al, [2]  Lakshmi Narayan Y, et al [16]. found that a prolonged QRS duration at baseline was associated with larger ventricular volumes and reduced systolic function [15][16].
Another study was done by Schinkel et al, [17]

Conclusion
• In patients with STEMI, the QRS duration is a useful indicator of left ventricular systolic function and dimensions and it is easily measured.
• QRS duration is a good predictor of outcome in patients with STEMI.
• Shortening of a prolonged QRS complex is a useful parameter for identifying successful thrombolysis in patients with acute STEMI. To our knowledge, this is one of the few studies that showed improvement of QRS duration with successful thrombolysis.