Tachycardia supraventricular

Dlgltoxin. Digitoxin is a cardiac glycoside obtained from Digitalis purpurea. Digitoxin is indicated in the treatment of atrial flutter, atrial fibrillation, and supraventricular tachycardia. Its electrophysiologic and adverse effects are similar to those described for digoxin (87). 

Adenosine is not active orally, but adrninistered as an iv bolus dmg adenosine rapidly eliminates supraventricular tachycardias within 1—2 min after dosing. The dmg slows conduction through the AV node. Adenosine is rapidly removed from the circulation by uptake into red blood ceUs and vascular endothehal ceUs. Thus the plasma half-life is less than 10 s. Adenosine is rapidly metabolized to inosine or adenosine monophosphate and becomes part of the body pool for synthesis of adenosine-triphosphate. 

Adenosine is produced by many tissues, mainly as a byproduct of ATP breakdown. It is released from neurons, glia and other cells, possibly through the operation of the membrane transport system. Its rate of production varies with the functional state of the tissue and it may play a role as an autocrine or paracrine mediator (e.g. controlling blood flow). The uptake of adenosine is blocked by dipyridamole, which has vasodilatory effects. The effects of adenosine are mediated by a group of G protein-coupled receptors (the Gi/o-coupled Ai- and A3 receptors, and the Gs-coupled A2a-/A2B receptors). Ai receptors can mediate vasoconstriction, block of cardiac atrioventricular conduction and reduction of force of contraction, bronchoconstriction, and inhibition of neurotransmitter release. A2 receptors mediate vasodilatation and are involved in the stimulation of nociceptive afferent neurons. A3 receptors mediate the release of mediators from mast cells. Methylxanthines (e.g. caffeine) function as antagonists of Ai and A2 receptors. Adenosine itself is used to terminate supraventricular tachycardia by intravenous bolus injection. 

Presently, only adenosine itself is approved for clinical use. It is used widely in the treatment of supraventricular tachycardia and in cardiac stress imaging to assess coronary artery disease [5]. Other agonists and antagonists and an allosteric modulator of the Ai receptor are in clinical trials for a variety of indications. 

PI (adenosine) receptors were explored as therapeutic targets before P2 receptors. Adenosine was identified early and is in current use to treat supraventricular tachycardia. A2a receptor antagonists are being investigated for the treatment of Parkinson s disease and patents have been lodged for the application of PI receptor subtype agonists and antagonists for myocardial ischaemia and reperfusion injury, cerebral ischaemia, stroke, intermittent claudication and renal insufficiency. 

Supraventricular tachycardia is a heart condition characterised by fast arrhythmias involving the atrioventricular (AV) node. 

Superoxide Dismutase Suprachiasmatic Nucleus Supraventricular Tachycardia SUR... 

These dm are primarily used in the treatment of hypertension (see the Summary Drug Table Adrenergic Blocking Drugs also see Chap. 39) and certain cardiac arrhythmias (abnormal rhythm of the heart), such as ventricular arrhythmias or supraventricular tachycardia They are used to prevent reinfarction in patients with a recent myocardial infarction (1—4 weeks after MI). Some of these dm have additional uses, such as the use of propranolol for migraine headaches and nadolol for angina pectoris. 

Management of Narrow Complex Stable Supraventricular Tachycardia (QRS < 0.12 s)... 

Paroxysmal (re-entry) supraventricular tachycardia (recurrent/ refractory to vagal stimulation or adenosine)... 

Management of Narrow Complex Stable Supraventricular Tachycardia... 

Compare and contrast the risk factors for and the features, mechanisms, etiologies, symptoms, and goals of therapy of (1) sinus bradycardia (2) atrioventricular (AV) nodal blockade (3) atrial fibrillation (AF) (4) paroxysmal supraventricular tachycardia (PSVT) ... 

Adenosine is the drug of choice for termination of paroxysmal supraventricular tachycardia. 

Paroxysmal supraventricular tachycardia (PSVT) is a term that refers to a number of arrhythmias that occur above the ventricles and that require atrial or AV nodal tissue for initiation and maintenance.32 The most common of these arrhythmias is... 

O Paroxysmal supraventricular tachycardia is caused by reentry that includes the AV node as a part of the reentrant circuit. Typically, electrical impulses travel forward (antegrade) down the AV node and then travel back up the AV node (retrograde) in a repetitive circuit. In some patients, the retrograde conduction pathway of the reentrant circuit may exist in extra-AV nodal tissue adjacent to the AV node. One of these pathways usually conducts impulses rapidly, while the other usually conducts impulses slowly. Most commonly, during PSVT the impulse conducts antegrade through the slow... 

FIGURE 6-10. Decision algorithm for termination of paroxysmal supraventricular tachycardia. HF, heart failure LVEF, left ventricular ejection fraction PSVT, paroxysmal supraventricular tachycardia. (Algorithm adapted with permission from Tisdale JE, Moser LR. Tachyarrhythmias. In Mueller BA, Bertch KE,... 

Most common Sedation, restlessness, diarrhea (metoclopramide), agitation, central nervous system depression Less common Extrapyramidal effects (more frequent with higher doses), hypotension, neuroleptic syndrome, supraventricular tachycardia (with intravenous administration)... 

PST Paroxysmal supraventricular tachycardia S3 Third heart sound (ventricular gallop)... 

PSVT Paroxysmal supraventricular tachycardia S4 Fourth heart sound (atrial gallop)... 

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