European Journal of Cardiovascular Medicine

Acute myocardial infarction (AMI) is defined by irreversible myocardial cell necrosis resulting from prolonged ischemia and is frequently associated with a wide spectrum of complications, among which cardiac arrhythmias are the most common and clinically significant. It has been estimated that nearly 90% of patients with AMI develop some form of arrhythmia during the course of the illness, with approximately one-quarter occurring within the first 24 hours of infarction. The risk is particularly high during the first hour, often referred to as the “golden hour,” when fatal ventricular arrhythmias are most likely to occur [1,2].

Cardiac arrhythmias in AMI may be classified into atrial tachyarrhythmias, ventricular tachyarrhythmias, and bradyarrhythmias. Among supraventricular arrhythmias, atrial fibrillation (AF) and atrial flutter are the most frequently encountered, affecting 6–21% of patients with myocardial infarction. New-onset AF has been reported in approximately 4–5% of patients with ST-elevation myocardial infarction (STEMI) and is associated with adverse short- and long-term outcomes, including heart failure, thromboembolism, and increased mortality [3–5]. According to American Heart Association data, the 30-day mortality following myocardial infarction ranges between 7.8% and 11.4%, with arrhythmias contributing significantly to this burden [6].

Despite major advances in early revascularization strategies such as thrombolytic therapy and primary percutaneous coronary intervention (PCI), the management of arrhythmias during the acute phase of myocardial infarction remains challenging. Several mechanisms have been proposed for arrhythmogenesis in AMI, including ischemia-induced alterations in myocardial electrophysiology, re-entry circuits caused by heterogeneous conduction, electrolyte disturbances, and autonomic imbalance [7–11]. Reperfusion itself may paradoxically precipitate arrhythmias due to sudden metabolic shifts and washout of accumulated ions and metabolites from ischemic myocardium, commonly referred to as reperfusion arrhythmias [12,13].

Arrhythmias occurring early after infarction can result in hemodynamic instability, reduced cardiac output, and sudden cardiac death. Ventricular fibrillation carries a mortality rate approaching 80% if not promptly treated [14]. Early recognition and management through pharmacological therapy, electrical cardioversion, or pacing are therefore critical.

Given the clinical importance of reperfusion arrhythmias, especially following thrombolytic therapy, this study aims to evaluate their prevalence after intravenous streptokinase administration and assess their prognostic significance in patients with acute myocardial infarction using continuous electrocardiographic monitoring.

This study was conducted as a prospective observational study with the objective of evaluating the incidence, types, and clinical outcomes of arrhythmias occurring in patients with acute ST-elevation myocardial infarction (STEMI) following thrombolytic therapy. The study was carried out in the Intensive Coronary Care Unit (ICCU) of Sir T. Hospital, Bhavnagar, a tertiary care teaching hospital catering to patients from urban and rural regions of South-Eastern Gujarat. The total duration of the study was 12 months, which included 6 months of patient enrollment and data collection, followed by analysis and interpretation. The study was approved by the Institutional Review Board of Government Medical College and Sir T. Hospital, Bhavnagar, Gujarat. The study was conducted in accordance with the principles of ICH–Good Clinical Practice (GCP) guidelines. Informed consent was obtained from all participants. The study population comprised patients admitted to the ICCU with a confirmed diagnosis of acute STEMI who underwent thrombolytic therapy during their hospital stay. A total of 160 patients were included in the study using a convenience sampling technique. All eligible patients meeting the inclusion criteria were enrolled consecutively during the study period. Inclusion Criteria Patients were included in the study if they met the following criteria: • Diagnosis of acute STEMI based on clinical presentation and electrocardiographic findings • Admission to the ICCU of Sir T. Hospital, Bhavnagar • Receipt of thrombolytic therapy during hospitalization Exclusion Criteria Patients were excluded if they had: 1. Previous history of ischemic heart disease 2. Known thyroid disorders 3. History of cardiac surgery 4. Chronic kidney disease 5. Ongoing treatment for cardiac arrhythmias 6. Documented electrolyte imbalance (hyponatremia, hypernatremia, hypokalemia, or hyperkalemia) Diagnostic Criteria and Monitoring Acute STEMI was diagnosed based on standard 12-lead ECG criteria, including ST-segment elevation >2 mm in men or >1.5 mm in women in leads V2–V3, ST-segment elevation ≥1 mm in other contiguous leads, or the presence of new or presumed new left bundle branch block (LBBB). These findings were supported by typical ischemic chest pain lasting more than 20 minutes. All patients underwent baseline ECG prior to thrombolysis and repeat ECG monitoring following thrombolytic therapy. Continuous cardiac monitoring was performed during ICCU stay, and additional ECGs were recorded whenever patients developed symptoms suggestive of arrhythmia. Serum electrolytes, including sodium and potassium, were routinely monitored. The primary outcome measures included: • Occurrence of arrhythmias following thrombolytic therapy • Type of arrhythmia detected • Clinical outcome (discharge or in-hospital mortality) Confounding Variables Potential confounders such as age, gender, diabetes mellitus, and hypertension were recorded and considered during analysis. Statistical Analysis Data were entered into Microsoft Excel for analysis. Categorical variables were expressed as frequencies and percentages, while continuous variables were summarized as mean ± standard deviation. Descriptive statistical methods were used, and results were presented using tables, bar diagrams, and pie charts where appropriate.

A total of 160 patients were enrolled during the study period according to inclusion and exclusion criteria. Their demographic and clinical profiles were mentioned below.

Table 1. demographic and clinical parameters of study participants

Table 1 presents the demographic and clinical profile of the 160 study participants. Most patients were aged 46–60 years (52.5%), followed by those older than 60 years (31.88%), indicating a predominance of middle-aged and elderly individuals. Males constituted most cases (65%). Hypertension was the most common co-morbidity (31.25%), followed by diabetes mellitus (23.75%) and combined diabetes with hypertension (21.88%). Anterior wall myocardial infarction was the most frequent infarct type (41.87%), followed by inferior wall myocardial infarction (25.63%), reflecting a higher burden of anterior wall involvement in the study population.

Table 2. Incidence and type of arrythmia after thrombolytic therapy

Table 2 shows that arrhythmias occurred in 63.13% of patients following thrombolytic therapy, while 36.87% did not develop any arrhythmia. Among the types of arrhythmias observed, ventricular premature complexes (VPCs) were the most common (22.77%), followed by sinus tachycardia (19.80%) and idioventricular rhythm (IVR) (14.85%). Complete heart block was noted in 9.90% of patients, whereas other arrhythmias such as atrial fibrillation, sinus bradycardia, and ventricular fibrillation were less frequent. Bleeding events were observed in 6.25% of cases. The majority of patients were discharged (91.88%), while the overall mortality rate was 8.12%.

Table 3. Distribution of arrhythmias according to the location of the infarction.

Arrhythmias were most frequently observed in anterior wall infarction (AW), accounting for the majority of cases (57/101), followed by inferior wall infarction (IW) (31/101) (Table 3). Ventricular premature complexes, sinus tachycardia, sinus bradycardia, and idioventricular rhythm were predominantly associated with AW infarctions. Complete heart block was more commonly seen in inferior wall–related infarctions, particularly IW and IW with right ventricular involvement. Arrhythmias were infrequently observed in posterior and lateral wall infarctions. Overall, anterior and inferior wall infarctions showed a higher propensity for post-thrombolytic arrhythmic events.

Table 4. Frequency distribution of different type of arrhythmia with respect to risk factors

Table 4 depicts the frequency distribution of various arrhythmias across different age groups. The majority of arrhythmic events were observed in patients aged 46–60 years (56 cases), followed by those older than 60 years (35 cases). Ventricular premature complexes, sinus tachycardia, idioventricular rhythm, and complete heart block were predominantly seen in the 46–60 years age group, with a continued high frequency in patients above 60 years. Arrhythmias were uncommon in younger patients, particularly in the 18–30 years age group. Overall, the findings indicate an increasing burden of post-thrombolytic arrhythmias with advancing age.

Table 5. Corelation of arrythmia distribution with gender

Table 5 demonstrates the correlation between arrhythmia distribution and gender. Arrhythmias were more frequently observed in male patients, accounting for 70 cases (69.31%), compared to 31 cases (30.69%) in females. Most arrhythmia types, including sinus tachycardia, sinus bradycardia, idioventricular rhythm, ventricular fibrillation, and ventricular premature complexes, were more common among males. Certain arrhythmias such as non-sustained ventricular tachycardia, supraventricular tachycardia, and atrial fibrillation were observed exclusively in males, whereas complete heart block showed an equal distribution between males and females. Overall, the findings indicate a male predominance in post-thrombolytic arrhythmic events.

Table 6. Corelation of arrythmia distribution with comorbid risk factors

Table 6 illustrates the correlation between arrhythmia distribution and associated co-morbid risk factors, namely diabetes mellitus (DM), hypertension (HT), and their combination. Arrhythmias were more frequently observed in patients with hypertension (32 cases) and in those with combined DM and HT (28 cases) compared to patients without these conditions. Ventricular premature complexes and idioventricular rhythm were commonly noted among patients with combined DM and HT. Atrial fibrillation and complete heart block showed a higher association with hypertension, while idioventricular rhythm and ventricular premature complexes were also prevalent in patients with diabetes mellitus. Overall, the findings suggest that the presence of co-morbid conditions, particularly hypertension alone or in combination with diabetes mellitus, is associated with a higher burden of post-thrombolytic arrhythmias.

Table 7. Arrythmia outcome

Table 7 summarizes the outcomes of patients with different types of arrhythmias following thrombolytic therapy. Among the 101 patients who developed arrhythmias, an overall mortality rate of 12.87% was observed. The highest mortality was noted in patients with ventricular premature complexes (6 deaths) and ventricular fibrillation (2 deaths), indicating poorer outcomes with malignant ventricular arrhythmias. Mortality was also observed in patients with atrial fibrillation, idioventricular rhythm, sinus tachycardia, sinus bradycardia, and complete heart block, though at lower frequencies. No deaths were reported in patients with non-sustained ventricular tachycardia, supraventricular tachycardia, or first- and second-degree heart block. Overall, ventricular arrhythmias were associated with higher mortality compared to supraventricular and conduction-related arrhythmias.

In the present study, myocardial infarction (MI) predominantly affected middle-aged and elderly patients, with the highest proportion in the 46–60-year age group (52.5%), followed by those aged >60 years (31.88%). This age distribution is comparable to earlier studies, which consistently reported a higher burden of MI among older populations [15-22]. The mean age of 54.54 ± 11.09 years in the present study aligns closely with observations by Kurmi et al. [18], Agarwal et al. [21], and Singh et al. [17], reinforcing the association between advancing age and MI risk.

A male predominance (65%) was observed, which is consistent with most published literature [15,17-23]. This pattern may be attributed to gender-related differences in cardiovascular risk factors, lifestyle exposure, and health-seeking behavior. Studies reporting a relatively balanced gender distribution still demonstrated a slight male excess, supporting the findings of the present study [16,21,23].

Hypertension (31.25%) and diabetes mellitus (23.75%) were the most common co-morbidities, with 21.88% of patients having both conditions. Although the prevalence of these co-morbidities was lower than that reported in several studies [105,106,108,111], the findings underscore their established role as important risk factors for MI [104,112,113].

Anterior wall myocardial infarction (AWMI) was the most frequent infarct type (41.87%), followed by inferior wall MI (25.63%), a pattern that mirrors observations in multiple studies [16-18,20]. Variations in the frequency of combined infarct types across studies may reflect differences in study populations and diagnostic practices.

Arrhythmias were observed in a substantial proportion of patients, with ventricular premature complexes (22.77%), sinus tachycardia (19.80%), and idioventricular rhythm (14.85%) being the most common. This distribution is broadly comparable to previous reports, although the relative frequencies varied across studies [15,17,20-22]. Ventricular arrhythmias, particularly VPCs and ventricular fibrillation, were associated with higher mortality, consistent with earlier findings emphasizing their adverse prognostic significance [15,21,24-27].

The overall mortality rate in the present study (8.12%) falls within the range reported by other studies [15-18,20-22], suggesting relatively favorable outcomes with timely thrombolytic therapy and monitoring. Higher mortality in patients with anterior wall involvement further supports existing evidence that larger infarct size and conduction system involvement contribute to poorer prognosis [22,28].

Overall, the present study demonstrates patterns of age, gender distribution, co-morbidities, infarct location, arrhythmia profile, and mortality that are largely consistent with published literature, reinforcing the need for early risk stratification and vigilant monitoring of high-risk MI patients.

The present study highlights that myocardial infarction predominantly affects middle-aged and elderly males, with hypertension and diabetes mellitus being the most common associated comorbidities. Anterior wall myocardial infarction was the most frequent infarct type and was associated with a higher risk of adverse outcomes. Arrhythmias were commonly observed following thrombolytic therapy, with ventricular premature complexes, idioventricular rhythm, and sinus tachycardia being the most prevalent. Ventricular arrhythmias contributed significantly to mortality, particularly in patients with anterior and anteroinferior infarctions. These findings emphasize the importance of early identification and vigilant monitoring of arrhythmias, along with optimal management of cardiovascular risk factors, to improve clinical outcomes and reduce mortality in patients with acute myocardial infarction.

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