Ambulance brings a 35 years old woman to the emergency medical services room and the diagnostic tests confirm supraventricular tachycardia as the reason for palpitations. Vagal maneuvers fails to provide adequate response. The best therapy that can be advocated is
Correct Answer: Adenosine
Description: Answer: d) Adenosine (HARRISON 19TH ED, P-1623)PAROXYSMAL SUPRA VENTRICULAR TACHYCARDIAAV NODAL RE-ENTRANT TACHYCARDIAMost common form of PSVTRegular tachycardia with a rate of 120-240/minIt tends to occur in the absence of structural heart diseaseEpisodes may last from a few seconds to many hoursThe patient is usually aware of a rapid, very forceful, regular heart beat and may experience chest discomfort, lightheadedness or breathlessness.Polyuria, mainly due to the release of atrial natriuretic peptide, is sometimes a feature.ECGTachycardia with normal QRS complexeP wave usually differs in contour from sinus beats and is often buried in the QRS complex ManagementTreatment is not always necessary.An episode may be terminated by carotid sinus massage (increase AV block) or by the Valsalva manoeuvre.Adenosine (3-12 mg rapidly IV in incremental doses until tachycardia stops) or verapamil (5 mg IV over 1 min) will restore sinus rhythm in most cases.In patients with recurrent SVT, catheter ablation is the most effective therapyWOLFF PARKINSON WHITE SYNDROMENormally AV node is the only pathway between atria and ventricles with some conduction delayAccessory bundle between atria and ventricles without conduction delay constitutes WPWA depolarization enters the ventricles early and causes pre-excitationWPW syndrome and AV nodal reentry tachycardia are examples of SVTSymptoms: palpitations, light-headedness, or syncopeECG findingsShort PR interval ( < 120 ms or < 0.12 s)Slurred upstroke of QRS complexes (delta wave)Wide QRS complexesTOC (recurrent symptomatic episodes, incessant SVT, HR > 200)- catheter ablationTreatment in pre-excited atrial fibrillation (life threatening) - DC cardioversionCarotid sinus massage or i.v. adenosine can terminate tachycardiaProphylaxis (amiodarone or propranolol) indicated in symptomatic patients onlyAV nodal reentrant tachycardia: frog sign can be elicited during arrhythmiasResponse to I.V AdenosineSupraventricular tachycardiaTerminationAtrial fibrillation, atrial flutterTransient AV blockVentricular fibrillationNo response
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