![]() ![]() Although adenosine blocks AV nodal conduction and therefore is mainly used to terminate AVNRT and AVRT, it may also terminate some forms of focal atrial tachycardia that are based on triggered activity. When vagal manoeuvres fail to restore sinus rhythm, intravenous adenosine can be administered as second-line therapy. 1 Therefore, this method is currently recommended as a first-line over other vagal manoeuvres to achieve sinus rhythm in the acute phase. In 2015, it was shown that the modified Valsalva manoeuvre, combining Valsalva with a postural modification (leg elevation and supine positioning at the end), was more efficient in terminating episodes of supraventricular tachycardia than the standard Valsalva manoeuvre (43% vs. In patients with AVNRT and AVRT, carotid sinus massage and Valsalva manoeuvres are often used successfully to terminate the tachycardia by slowing conduction over the atrioventricular (AV) node, which is a critical part of the circuit. When confronted with patients with haemodynamically stable narrow QRS tachycardia, vagal manoeuvres can be used as a first-line attempt to achieve reconversion to sinus rhythm. In atrial flutter, flutter waves with a typical sawtooth pattern can be regarded as the main hallmark of common clockwise isthmus-dependent atrial flutter. In focal atrial tachycardia, the p-waves are not retrograde and typically present not after, but just before the QRS-complex, with a PR-interval depending on antegrade conduction properties. In orthodromic AVRT, the retrograde p-waves are typically identified later (80–120 ms) after the end of the QRS-complex as the atria are only activated retrogradely over the accessory pathway after the ventricular myocardium has been depolarized. Other tachycardias that should be considered in the differential diagnosis are orthodromic atrioventricular reentrant tachycardia (AVRT) over an accessory pathway, focal atrial tachycardia, and atrial flutter. The presence of a retrograde p-wave in or at the end of the QRS-complex is the hallmark of typical slow/fast AVNRT. The ECG on presentation showed a regular narrow QRS tachycardia with a ventricular rate of 192 b.p.m. The presence of a retrograde p-wave in or at the end of the QRS-complex is the hallmark of typical slow/fast atrioventricular nodal reentrant tachycardia. On close inspection of the electrocardiogram, a retrograde p-wave can be identified at the end of the QRS-complex, as a pseudo-S wave in lead I, and as notching at the end of the QRS in the inferior leads, aVR and V1 (marked with blue arrows). Regular narrow QRS tachycardia at a rate of 192 b.p.m. ![]()
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