Vpc Network Overview

Ventricular premature complexes (VPCs) are ectopic impulses originating from an area distal lớn the His Purkinje system. VPCs are the most common ventricular arrhythmia. Assessment và treatment of VPCs is challenging and complex, and is highly dependent on the clinical context. The prognostic significance of VPCs is variable and, again, best interpreted in the context of the underlying cardiac condition.

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The approach khổng lồ the evaluation and management of VPCs has undergone dramatic changes in the last decade. Observational studies and inferences from typical electrophysiology studies were initially focused on ventricular ectopy triggering ventricular tachycardia (VT), which, in turn, can degenerate inkhổng lồ ventricular fibrillation, as a mechanisms for sudden cardiac death. The treatment paradigm in the 1970s & 1980s was to eliminate VPCs in patients after myocardial infarction (MI). The Cardiac Arrhythmia Suppression Trial (CAST) và other arrhythmia suppression studies have sầu demonstrated that eliminating VPCs with available antiarrhythmic drugs increases the risk of death to lớn patients without providing any measurable benefit. <1>


Very few studies have sầu evaluated the pathophysiology of VPCs in human subjects. Most of the information is derived from animal studies. Three comtháng mechanisms exist for VPCs, (1) automatiđô thị, (2) reentry, & (3) triggered activity, as follows:

Automaticity: This is the development of a new site of depolarization in nonnodal ventricular tissue, which can lead to a VPC. In animal models, focal mechanisms without evidence of macro-reentry play a major role in the origin of ventricular arrhythmia associated with ischemic cardiomyopathy. Increased automatithành phố could be due khổng lồ electrolyte abnormalities or ischemic myocardium.

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Reentry circuit: Reentry typically occurs when slow-conducting tissue (eg, infarcted myocardium) is present adjacent lớn normal tissue. The slow-conducting tissue could be due lớn damaged myocardium, as in the case of a healed XiaoMI.

Triggered activity: After depolarizations triggered by a preceding impulse can lead to lớn premature activation if the threshold is reached, và this can cause a VPC. Afterdepolarization can occur either during (early) or after (late) completion of repolarization. Early afterdepolarizations commonly are responsible for bradycardia associated VPCs, but they also can be present with ischemia và electrolyte abnormalities.