Wolff–Parkinson–White and pre-excitation — structured written assessment

SAQ 1 (10 marks)

Practice scenario. A 26-year-old man presents to the emergency department with palpitations. The ECG shows an irregular, rapid, wide QRS tachycardia with varying QRS morphology; a previous ECG showed ventricular pre-excitation.^[1] His blood pressure is 118/76 mm Hg and he is alert. His heart is structurally normal, he has no ischaemic heart disease, and his last QTc interval was normal.^[1]

1. What three ECG features does ESC 2019 give for pre-excited AF, and what causes the changing QRS morphology? (2)^[1]
2. Explain why AV-nodal blocking drugs are dangerous here, citing ESC 2019 and ACC/AHA/HRS 2015 text. (2)^[1][2]
3. List the ESC 2019 rows for a haemodynamically stable patient with pre-excited AF, with class and level. (4)^[1]
4. Once he is in sinus rhythm, what definitive treatment does ACC/AHA 2023 recommend, with COR and LOE? (2)^[5]

Model answers — SAQ 1

1. Irregularity, a varying QRS morphology and a rapid ventricular rate (1 mark).^[1] The changing morphology results from varying degrees of fusion between activation over the AP and the AV node, which also varies the width of the delta wave (1 mark).^[1]
2. ESC 2019: conduction can occur preferentially via the AP "due to its shorter RP compared with the AVN", so any AV node-modulating agents should be avoided, as they may contribute to a risk of ventricular fibrillation (1 mark).^[1] ACC/AHA/HRS 2015: digoxin increases the ventricular rate by shortening AP refractoriness, whereas amiodarone, beta blockers, diltiazem and verapamil may increase it through drug-induced hypotension with increased catecholamines; these drugs may also enhance AP conduction by slowing or blocking AV-nodal conduction, preventing competitive concealed retrograde conduction into the AP (1 mark).^[2]
3. Ibutilide or procainamide (i.v.) should be considered: Class IIa, Level B (1 mark).^[1] Flecainide or propafenone (i.v.) may be considered: Class IIb, Level B (1 mark).^[1] Synchronized DC cardioversion is recommended if drug therapy fails to convert or control the tachycardia: Class I, Level B (1 mark).^[1] Amiodarone (i.v.) is not recommended: Class III, Level B (1 mark).^[1]
4. Catheter ablation of accessory pathways is recommended for patients with preexcited AF (1 mark).^[5] COR 1, LOE B-NR (1 mark).^[5]

SAQ 2 (10 marks)

Practice scenario. A 19-year-old competitive footballer has ventricular pre-excitation on a pre-participation ECG.^[8] He has never had palpitations, syncope or a documented arrhythmia. Echocardiography is normal.^[8]

1. Using ESC 2019, distinguish a WPW pattern from WPW syndrome, and state which applies to him. (2)^[1]
2. Give the strongest ESC 2019 row that applies to risk stratification in his case, with class and level. (2)^[1]
3. List the four high-risk features at electrophysiology study given in the ESC 2019 Figure 22 legend. (2)^[1]
4. Give two limitations of non-invasive markers described by ESC 2019. (2)^[1]
5. His EPS shows a low-risk pathway. Give the ESC 2019 rows on follow-up and on ablation that then apply, with class and level. (2)^[1]

Model answers — SAQ 2

1. ESC 2019 describes the typical WPW pattern in the resting ECG during sinus rhythm as a short PR interval (≤120 ms), a delta wave and a wide QRS complex (>120 ms), and says various degrees of pre-excitation are possible depending on the location of the AP and on AVN conduction properties; WPW syndrome is an overt (manifest) AP in combination with usually recurrent tachyarrhythmias (1 mark).^[1] He has no tachyarrhythmia, so he does not meet the ESC 2019 definition of WPW syndrome; ESC 2019 calls this an asymptomatic WPW pattern (1 mark).^[1]
2. Performance of an EPS, with the use of isoprenaline, is recommended to risk stratify individuals with asymptomatic pre-excitation who participate in competitive athletics (1 mark).^[1] Class I, Level B (1 mark).^[1]
3. Shortest pre-excited RR interval during AF ≤250 ms; accessory pathway effective refractory period ≤250 ms (1 mark).^[1] Multiple accessory pathways; inducible atrioventricular re-entrant tachycardia (1 mark).^[1]
4. Intermittent pre-excitation is an imperfect marker of a low-risk AP: studies including symptomatic and asymptomatic patients have indicated that more than one-fifth of patients with it have AP ERPs <250 ms (1 mark).^[1] Catecholamine sensitivity is a major limiting factor of all tests, including exercise testing (1 mark).^[1]
5. Clinical follow-up should be considered in a patient with asymptomatic pre-excitation and a low-risk AP at invasive risk stratification: Class IIa, Level C (1 mark).^[1] Catheter ablation may be considered (Class IIb, Level C) in a patient with asymptomatic pre-excitation and a low-risk AP at invasive or non-invasive risk stratification, and in low-risk asymptomatic pre-excitation in appropriately experienced centres according to patient preferences; either row earns the mark (1 mark).^[1]