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[In Process Citation]
1IV. interna klinika Lekarskej fakulty Univerzity Komenskeho v Bratislave, Slovakia.
Insights
Supraventricular arrhythmias and conduction disturbances during acute myocardial infarction (AMI) signal higher mortality risk, often due to underlying heart failure and ventricular arrhythmias, not the arrhythmias themselves.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Background:
- Supraventricular arrhythmias (SVA) and atrioventricular (AV) and intraventricular (IV) conduction disturbances are common in acute myocardial infarction (AMI).
- These arrhythmias can stem from atrial ischemia, hemodynamic factors, ventricular dysfunction, atrial dilatation, increased intraatrial pressure, and autonomic nervous system imbalances.
- AV conduction disturbances are more prevalent in inferior AMI, often linked to parasympathetic activation and ischemia/necrosis of the AV node or junction.
Purpose of the Study:
- To investigate the occurrence and clinical significance of supraventricular arrhythmias and conduction disturbances in acute myocardial infarction.
- To differentiate the prognostic implications of these arrhythmias based on their type and timing during AMI.
- To identify their role as markers for high-risk patients requiring intensive management.
Main Methods:
- Review of clinical data and electrocardiographic findings in patients with acute myocardial infarction.
- Analysis of the association between different types of arrhythmias/conduction disturbances and clinical outcomes, including mortality.
- Stratification of risk based on the presence and characteristics of SVA and AV/IV conduction abnormalities.
Main Results:
- SVA are associated with inferior, posterior, and lateral AMI, right ventricular infarction, and pericarditis.
- High-degree AV block in inferior AMI generally has a better prognosis and is often reversible compared to anterior AMI.
- New bundle branch blocks (BBB), particularly right bundle branch block, can predict complete AV block and are markers of multivessel disease.
- Frequent SVA and serious AV/IV conduction disturbances are associated with worse clinical course and increased mortality, primarily due to heart failure and ventricular arrhythmias.
Conclusions:
- SVA and conduction disturbances in AMI serve as crucial markers for identifying high-risk patients.
- While not independent predictors of mortality, their presence necessitates aggressive management of underlying coronary artery disease and heart failure.
- Early identification and intensive treatment are vital for improving outcomes in patients with AMI complicated by these arrhythmias.
Abstract:
In addition to ventricular arrhythmias, various forms of supraventricular arrhythmias (SVA) and atrioventricular (AV) and intraventricular (IV) conduction disturbances occur also in acute myocardial infarction (AMI). In the setting of AMI, SVA may be caused by relevant atrial ischemia or infarction. SVA complicate the course especially that of inferior, posterior and lateral AMI, SVA occur frequently also in the right ventricular myocardial infarction and in pericarditis. SVA appearing in the late phase of AMI are caused particularly by hemodynamic factors especially those of both left and right ventricular dysfunctions. Atrial dilatation and the increase of intraatrial pressure are also important factors in the genesis of SVA. The autonomous nervous system, electrolyte disturbances, acidosis and global hypoxia may operate as modulating factors in the development of SVA. AV conduction disturbances are significantly more frequent in patients with inferior than with anterior AMI. In inferior AMI, they are frequently caused by reflex parasympathetic activation. In the genesis of AV conduction disturbances, a significant role may be played also by the following mechanisms: Ischemia or necrosis of AV node or AV junction and the negative dromotropic effect of adenosine and potassium which are released to a great extent during myocardial ischemia and reperfusion. A high-degree AV block complicating the course of inferior AMI has a significantly better prognosis than that occurring in the setting of anterior AMI. In inferior AMI, AV block is frequently reversible, whereas in anterior AMI, it is persistent and irreversible. Early AV conduction disturbances, appearing within 24 hours of AMI have a better prognosis than those occurring in the late phase of AMI. Bundle branch blocks (BBB) complicating the course of AMI are caused by occlusion of bundle-related coronary artery or by serious ischemia in its bed. BBB is frequently a marker of a multivessel disease. New BBB appearing in AMI especially the right bundle branch block is considered as an predictor for the development of a complete AV block. Frequent and repetitive SVA as well as serious AV and IV conduction disturbances are frequently associated with a significantly worse clinically course of AMI and with increased mortality, with that of especially hospital mortality. However, this is usually not caused by SVA or AV and IV conduction disturbances per se. The major cause of death in these patients are heart failure cardiogenic shock and malignant ventricular arrthythmias due to larger AMI, significant reduction of left ventricular function and advanced coronary heart disease. Complex SVA as well as serious AV and IV conduction disturbances are usually considered as markers, but not as independent predictors for both increased hospital mortality and in some cases also for that of posthospital mortality. Their occurrence in AMI may help to identify the patients at great risk who require a very intensive treatment including aggressive management of extensive coronary heart disease. (Ref. 62.).