Supraventricular tachycardia — structured written assessment

SAQ 1 (10 marks)

Practice scenario. A 24-year-old woman presents to the emergency department with 40 minutes of sudden-onset regular palpitations. HR 186/min, BP 118/72 mmHg; she is alert, with no chest pain, breathlessness or signs of heart failure. The ECG shows a regular narrow QRS tachycardia (QRS duration 120 ms or less). No diagnosis has yet been established.^[1]

1. Define a narrow QRS tachycardia and list the regular narrow QRS tachycardias in ESC 2019 Table 6. (3)^[1]
2. Give the 2019 ESC acute management for her, with class and level, and describe the modified Valsalva manoeuvre and its trial result. (4)^[1][4]
3. Give the ESC 2019 adenosine regimen and any three cautions about its use. (3)^[1]

Model answers

• Q1. A narrow QRS tachycardia has a QRS duration of 120 ms or less. The regular narrow QRS tachycardias in ESC Table 6 are physiological sinus tachycardia, inappropriate sinus tachycardia, sinus nodal re-entrant tachycardia, focal AT, atrial flutter with fixed AV conduction, AVNRT, JET (or other non-re-entrant variants), orthodromic AVRT and idiopathic VT (especially high septal VT).^[1]
• Q2 (management). She is haemodynamically stable with a narrow QRS tachycardia and no established diagnosis. For this group, ESC 2019 recommends a 12-lead ECG during tachycardia (Class I, level C), then vagal manoeuvres, preferably in the supine position with leg elevation (Class I, level B), then adenosine 6–18 mg IV bolus if vagal manoeuvres fail (Class I, level B). IV verapamil or diltiazem (Class IIa, level B) or IV esmolol or metoprolol (Class IIa, level C) should be considered if vagal manoeuvres and adenosine fail; IV verapamil and diltiazem are contraindicated in hypotension or HFrEF, and IV beta-blockers in decompensated heart failure. Synchronised DC cardioversion is recommended when drug therapy fails to convert or control the tachycardia (Class I, level B).^[1]
• Q2 (modified Valsalva and its trial). The strain is done semi-recumbent, followed by supine repositioning and passive leg raise immediately after the strain. In REVERT (adults with SVT, excluding AF and flutter, in emergency departments in England; 40 mm Hg, 15 s strain), sinus rhythm at 1 min was achieved in 43% (93 of 214) with the modified manoeuvre vs 17% (37 of 214) with a standard semi-recumbent Valsalva manoeuvre (adjusted OR 3.7, 95% CI 2.3–5.8), with no serious adverse events.^[4]
• Q3 (regimen). Adenosine is given as a rapid IV bolus with an immediate saline flush, starting at 6 mg in adults, then 12 mg, then considering 18 mg, taking into account tolerability and side effects; large, centrally located (e.g. antecubital) veins are likely to deliver more effective drug concentrations to the heart, and repeat dosing is safe within 1 min of the last dose.^[1]
• Q3 (cautions; any three of the following). Approach cautiously in known sinus node disease. AF may follow adenosine, and adenosine may occasionally cause or accelerate pre-excited atrial arrhythmias. In AVRT, use it with caution because of potential induction of fast AF, which could induce ventricular fibrillation, so electrical cardioversion should always be available. It must be avoided if pre-excitation on the resting ECG suggests a pre-excited tachycardia, because in antidromic re-entry it may precipitate cardiac arrest if it induces AF. Care is required in asthma, where verapamil may be more appropriate if asthma is severe. Some drugs, such as dipyridamole and theophylline, may on occasion affect dose requirements. In suspected atrial flutter with 2:1 block, adenosine can produce a rebound increase in AV conduction to 1:1 and may precipitate AF, so use it only if needed for diagnosis and with resuscitation equipment available. Avoid it, like any AV nodal modulating agent, in pre-excited AF, because it may contribute to a risk of ventricular fibrillation.^[1]

SAQ 2 (10 marks)

Practice scenario. The same woman converts to sinus rhythm after adenosine. Her sinus rhythm ECG shows a PR interval of 100 ms, a slurred QRS upstroke and a QRS duration of 130 ms. She has had three similar episodes this year and is troubled by them. Her echocardiogram shows a structurally normal heart, she has no ischaemic heart disease, and an electrophysiology study confirms orthodromic AVRT over a manifest accessory pathway.^[1]

1. Name the syndrome and give its ESC 2019 definition and resting ECG features. (2)^[1]
2. Outline her long-term management under ESC 2019, with class and level. (3)^[1]
3. She later presents with an irregular wide QRS tachycardia at about 240 b.p.m. with varying QRS morphology. She is alert, BP 112/70 mmHg, with no chest pain, no signs of heart failure and no signs of shock. Give the ESC 2019 acute management and the drugs to avoid, with classes. (3)^[1]
4. In a different, asymptomatic patient with pre-excitation, list the clinical and electrophysiological features that ESC 2019 associates with an increased risk of sudden cardiac death. (2)^[1]

Model answers

• Q1. WPW syndrome: an overt (manifest) AP producing pre-excitation, with usually recurrent tachyarrhythmias. The resting ECG in sinus rhythm shows a short PR interval (120 ms or less), a slurred QRS upstroke or downstroke (delta wave) and a wide QRS (above 120 ms).^[1]
• Q2. Catheter ablation of the AP is recommended for symptomatic, recurrent AVRT (Class I, level B). If ablation is not desirable or feasible: beta-blockers or verapamil or diltiazem (in the absence of HFrEF) should be considered if there are no signs of pre-excitation on the resting ECG (Class IIa, level B), which does not apply to her; propafenone or flecainide may be considered in AVRT without ischaemic or structural heart disease (Class IIb, level B).^[1]
• Q3 (treatment). Irregularity, a varying QRS morphology and a rapid ventricular rate are the features of pre-excited AF. For haemodynamically stable patients, as she is, IV ibutilide or procainamide should be considered (Class IIa, level B) and IV flecainide or propafenone may be considered (Class IIb, level B); IV ibutilide is contraindicated with a prolonged QTc, and IV flecainide and propafenone in ischaemic or structural heart disease. Synchronised DC cardioversion is recommended if drug therapy fails to convert or control the tachycardia, and for haemodynamically unstable patients (both Class I, level B).^[1]
• Q3 (drugs to avoid). Acutely, avoid any AV nodal modulating agent (adenosine, verapamil, diltiazem, beta-blockers or digoxin), because these drugs may contribute to a risk of ventricular fibrillation, and, as she is haemodynamically stable, IV amiodarone is not recommended (Class III, level B). The ESC AVRT recommendations (chronic therapy) also list digoxin, beta-blockers, diltiazem, verapamil and amiodarone as not recommended and potentially harmful in patients with pre-excited AF (Class III, level B).^[1]
• Q4 (asymptomatic pre-excitation, ESC 2019 section 11.3.11). Younger age, inducibility of AV-reciprocating tachycardia during EPS, multiple APs, and demonstration that the AP can conduct rapidly to the ventricles, including a SPERRI of 250 ms or less at baseline or a short antegrade AP ERP (250 ms or less).^[1]