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Arrhythmogenic mechanisms in left ventricular hypertrophy
1Department of Cardiology, Medical Centre for Postgraduate Education, Warsaw, Poland.
Insights
Left ventricular hypertrophy (LVH) increases mortality via ventricular arrhythmias. Electrophysiological changes like prolonged action potentials and impaired calcium handling in LVH promote dangerous heart rhythms.
Area of Science:
- Cardiology
- Electrophysiology
- Molecular Cardiology
Background:
- Left ventricular hypertrophy (LVH) is linked to high mortality and sudden cardiac death.
- Ventricular arrhythmias are a primary cause of mortality in LVH patients.
- The pro-arrhythmic electrophysiological phenotype of hypertrophied myocardium underlies this risk.
Purpose of the Study:
- To elucidate the electrophysiological mechanisms driving ventricular arrhythmias in LVH.
- To explore the role of altered action potential duration, calcium handling, and conduction properties.
- To investigate the contribution of extrinsic factors to arrhythmogenesis in LVH.
Main Methods:
- Review of electrophysiological abnormalities in LVH.
- Analysis of action potential duration and refractoriness.
- Examination of intracellular calcium handling mechanisms (ryanodine receptors, Ca2+-ATPase).
- Assessment of ventricular conduction properties and I(f) current expression.
- Consideration of extrinsic factors like myocardial ischemia and neuroendocrine influences.
Main Results:
- Prolongation of action potential duration and refractoriness, leading to triggered activity and re-entry.
- Impaired intracellular calcium handling due to altered ryanodine receptor and Ca2+-ATPase function.
- Slowed and fractionated ventricular conduction, promoting micro-reentry.
- Increased automaticity potentially linked to I(f) current expression.
- Association of LVH with extrinsic factors like ischemia exacerbates pro-arrhythmic potential.
Conclusions:
- LVH creates a pro-arrhythmic substrate through multiple electrophysiological alterations.
- Impaired calcium homeostasis and conduction abnormalities are key mechanisms.
- Extrinsic factors, particularly myocardial ischemia, significantly contribute to arrhythmias in LVH.
- Further research is needed to fully understand these interactions and guide antiarrhythmic therapy.
Abstract:
An important mechanism contributing to the high mortality and sudden death in patients with left ventricular hypertrophy (LVH) is ventricular arrhythmia. Part of the risk is associated with the pro-arrhythmic electrophysiological phenotype of the hypertrophied myocardium. The most consistently observed abnormality is prolongation of the action potential duration and refractoriness, which sets the stage for arrhythmias based on early or delayed afterdepolarizations and triggered activity. In addition, non-uniform prolongation of the action potential in LVH may be pro-arrhythmic by leading to increased dispersion of repolarization or refractoriness and favouring re-entry. The occurrence of delayed after depolarization-induced triggered activity and other ventricular arrhythmias are also related to the impaired ability to handle intracellular calcium due to changes in the density of ryanodine receptors and the Ca2+-ATPase of the sarcoplasmic reticulum. Slowing and fractionation of ventricular conduction, creating the conditions for micro-reentry and arrhythmogenesis, are characteristic of severe LVH, as is the expression of the I(f) current (which may be a source of increased automaticity). The pro-arrhythmic potential of LVH is also related to the presence of coexisting 'extrinsic' factors. The most important and pro-arrhythmic association of LVH is that with myocardial ischaemia. Other conditions include neuroendocrine factors, ventricular wall stress or electrolyte disturbances. The electrophysiological mechanisms of the interactions between these 'extrinsic' factors and LVH have not been fully elucidated. Further research into these mechanisms is required and may have important implications for our understanding of the mechanisms of cardiac arrhythmias in LVH and the appropriate use of antiarrhythmic drug therapy.