Once terminated, the resting ECG may show signs of pre-excitation: a delta wave with a widened QRS complex and a short PR interval. An ECG performed during the tachyarrhythmia may show retrograde P waves following the QRS complex. 10 In AVRT with a narrow QRS complex, a circuit forms from the anterograde conduction through the AV node and retrograde conduction through the accessory pathway. In patients with AVRT, the tachycardia involves both the AV node and an extranodal accessory pathway (bypass tract) that connects the myocardium of the atrium to the ventricle. Typical: acute success rate 97% recurrence rate 10% Atypical: acute success rate 73%–100% recurrence rate 7%–53%Įlectrocardiographic clues to the diagnosis of atrioventricular re-entrant tachycardia and atrioventricular nodal re-entrant tachycardia include a P wave following the QRS complex, as can be seen in lead II (solid arrow) and lead V 1 (dotted arrow), and a short RP interval. Yes if age ≥ 65 yr or CHADS 2 score ≥ 1 (CCS guideline 35) Macro–re-entrant circuit (typically in the right atrium)Ītrial flutter wave with 2:1 conduction block or variable conduction block Unlikely to terminate may unmask underlying rhythmĪcute success rate 80%–100% recurrence rate 4%–27% Regular or irregular (if variable AV block) Re-entry involving AV node and accessory pathwayĪcute success rate 93% recurrence rate 8%Įctopic atrial focus with enhanced automaticity 5ĪV re-entry involving 2 functional pathways in the AV nodeĪcute success rate 96%–97% recurrence rate 5% Rapid recognition of the underlying rhythm is essential to correct management in the acute setting, including identifying patients who may benefit from definitive treatment with catheter ablation. Occasionally, they may show a wide QRS complex in the case of a pre-existing conduction delay, an aberrancy due to rate-related conduction delay or a bundle branch block. Supraventricular tachycardias are usually narrow-complex tachycardias with a QRS interval of 100 ms or less on an electrocardiogram (ECG). 4 The term paroxysmal SVT denotes a subset of SVTs that present as a clinical syndrome of rapid regular tachycardia with an abrupt onset and termination. Supraventricular tachycardias represent a range of tachyarrhythmias ( Figure 1) originating from a circuit or focus involving the atria or the atrioventricular node. population and the incidence 35 per 100 000 person-years. 2 In the US, the prevalence of paroxysmal SVT in the general population is 2. 1 Atrial flutter has an overall incidence of 88 per 100 000 person-years, with an increasing incidence in older people, men and people with heart failure or chronic obstructive pulmonary disease. Although Canadian epidemiologic data are lacking, evidence from the United States suggests that they account for about 50 000 emergency department visits annually. Supraventricular tachycardias (SVTs) are common.
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