室上性心动过速英文.pptxVIP

Supraventricular Tachycardias David Melvin, MD 10/1/2003;■ Pathophysiology ■ Diagnosis ■ Treatment ■ Acute ■ Chronic ■ Excluding Atrial Fibrillation and Flutter;Epidemiology ■ Common problem presenting ED5s ■ Prevalence 2.25/1000 ■ Orejarena, J AM Coll Card. 1998;31:150-7 ■ Mean age of onset 57 years ■ Ranging from infancy to 90 years old ■ In this study, younger patients (mean of 37) were more likely to present to the ED and less likely to have structural heart disease(69%);■ Two basic mechanisms leading to all Tachyarrhythmias ■ Impaired impulse initiation ■ problems of abnormal automaticity ■ Abnormal impulse conduction ■ Re-entrant impulses;Location of disorder ■ SVT is any arrhythmia arising from AV node or above ■ Impulses can be transmitted from several loci ■ Sinus Node ■ Atrium ■ AV Node ■ Point of origin has implications for treatment;■ There are two basic forms of SVTs arising from the AV node ■ Atrioventricular Node Reciprocating Tachycardia(AVNRT) ■ Atrioventricular Reciprocating T achycardia(AVRT) ■ Both are dependent on the AV node for maintenance of the Reentry circuit;Reentry Circuits;AVNRT ■ Accounts for more than half of the cases of PSVTs ■ Fast and slow conducting fibers from the atrium to the AV node make up reentry circuit ■ Fast fibers have a long refractory period ■ Slow fibers have a shorter refractory period;AVNRT(cont) ■ Cycle is started by a PAC ■ Fast fibers are still refractory from previous impulse ■ Impulse conducted down Slow fibers and retrogradely up fast fibers ■ This slow-fast mechanism accounts for 90% of AVNRTs;AVNRT(cont.);AVRT;AVRT(cont.);AVRT(cont-) ■ Reentry is precipitated by a PAC or PVC ■ Dependent on AV node for continued reentry;■ Both AVNRT and AVRT arise due to reentrant mechanism ■ Both are dependent on the AV node for their maintenance ■ Drugs that work on the AV node should break the circuit;Atrial Tachycardias ■ Unifocal atrial tachycardia ■ Single P wave morphology ■ May be due to either abnormal automaticity o