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A premature ventricular contraction (PVC) is a common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node. PVCs may cause no symptoms or may be perceived as a "skipped beat" or felt as palpitations in the chest. PVCs do not usually pose any danger. [1]
Ectopic beat is a disturbance of the cardiac rhythm frequently related to the electrical conduction system of the heart, in which beats arise from fibers or group of fibers outside the region in the heart muscle ordinarily responsible for impulse formation (i.e., the sinoatrial node).
The medications that most commonly cause first-degree heart block are those that increase the refractory time of the AV node, thereby slowing AV conduction. These include calcium channel blockers, beta-blockers, cardiac glycosides, and anything that increases cholinergic activity such as cholinesterase inhibitors. [2]
Atrioventricular block (AV block) is a type of heart block that occurs when the electrical signal traveling from the atria, or the upper chambers of the heart, to ventricles, or the lower chambers of the heart, is impaired.
This is called a "compensatory" pause. The pause after the PVC leads to a longer recovery time, which is associated with a higher likelihood of myocardium being in different stages of repolarization. This then allows for re-entrant circuits and sets up the ventricle for another PVC after the next sinus beat. [ 2 ]
The second Cardiac Arrhythmia Suppression Trial (CAST II) modified the enrollment criteria to include patients at higher risk for serious arrhythmia. [4] This included 1) patients enrolled within 4 to 90 days of a previous MI, 2) a left ventricular ejection fraction lower than 40%, 3) prior to enrollment, suppression of PVCs had occurred with the drugs (vs. placebo) using a double-blinded ...
Idioventricular means “relating to or affecting the cardiac ventricle alone” and refers to any ectopic ventricular arrhythmia. [1] Accelerated idioventricular arrhythmias are distinguished from ventricular rhythms with rates less than 40 ( ventricular escape ) and those faster than 120 ( ventricular tachycardia ). [ 2 ]
The 1-ellipse is the circle, and the 2-ellipse is the classic ellipse. Both are algebraic curves of degree 2. For any number n of foci, the n-ellipse is a closed, convex curve. [2]: (p. 90) The curve is smooth unless it goes through a focus. [5]: p.7