Ventricular tachycardia — structured viva

Stem

Practice scenario. A 66-year-old man with a previous myocardial infarction has a regular wide QRS tachycardia at 145 b.p.m. He is alert, blood pressure 110/70 mmHg.

Branch A — Is this VT?

Examiner: He looks well. Could this be SVT with aberrancy?

Strong answer: It could, but the default diagnosis of a wide QRS tachycardia is VT until proven otherwise, because misdiagnosis and drugs usually used for SVT can harm a patient in VT. Reported proportions are 80% VT, 15% SVT with BBB aberration and 5% antegrade accessory pathway conduction. I would look for AV dissociation or capture/fusion beats, which are key diagnostic features of VT; P waves are usually more prominent in the inferior leads and with a Lewis lead. Negative chest lead concordance is almost diagnostic of VT, with a specificity above 90%, but is present in only 20% of VTs.^[2]

Examiner: Which algorithm would you use?

Strong answer: The Brugada stepwise approach reported a sensitivity of 0.987 and specificity of 0.965 in 554 tachycardias.^[16] The Vereckei lead aVR algorithm diagnoses VT if there is an initial R wave, an initial r or q above 40 ms, or a notch on the initial downstroke of a predominantly negative QRS; otherwise vi/vt of 1 or less suggests VT.^[17] The 2019 ESC SVT guideline cautions that ECG methods have accuracies of about 75%, similar to calling every wide QRS tachycardia VT, because only 25–30% are SVTs.^[2]

Branch B — Acute termination

Examiner: It is sustained monomorphic VT. What now?

Strong answer: Even tolerated SMVT should be terminated promptly, because rapid haemodynamic deterioration may occur. ESC 2022 recommends DC cardioversion as first-line treatment for tolerated SMVT provided that the anaesthetic/sedation risk is low (Class I, level C). For haemodynamically tolerated SMVT with known or suspected SHD, intravenous procainamide should be considered (Class IIa, level B). ESC Table 8 gives procainamide as a 100 mg bolus, can be repeated after 5 min if no effect, to a maximum of 500–750 mg (maximum 50 mg/min), then 2–6 mg/min.^[1]

Examiner: Why procainamide rather than amiodarone?

Strong answer: In PROCAMIO, major cardiac adverse events within 40 min occurred in 9% with procainamide versus 41% with amiodarone, and termination within 40 min in 67% versus 38%.^[4] ESC rates intravenous amiodarone lower: it may be considered for tolerated SMVT in the absence of an established diagnosis (Class IIb, level B). Intravenous procainamide should not be used in severe heart failure, acute MI or end-stage renal disease, and procainamide is not available in many European countries.^[1]

Examiner: What if his blood pressure falls to 75/40 mmHg?

Strong answer: Immediate synchronised DC cardioversion, which is first-line for haemodynamically not-tolerated SMVT (Class I, level B); if synchronisation is not possible, an unsynchronised shock.^[1]

Branch C — Torsades de pointes

Examiner: A different patient on sotalol has twisting polymorphic VT with a long QT. Management?

Strong answer: This is TdP, a subtype of polymorphic VT in the context of QT prolongation, with continually changing QRS complexes that appear to spiral around the baseline of the ECG lead in a sinusoidal pattern. In Recommendation Table 9, listed under management of electrical storm, ESC 2022 recommends intravenous magnesium with potassium supplementation in TdP (Class I, level C); magnesium works even without hypomagnesaemia. The offending drug is withdrawn and QT-prolonging drugs such as sotalol avoided. If TdP recurs despite correction of precipitating conditions and magnesium in acquired LQT syndrome, isoproterenol or transvenous pacing to increase heart rate is recommended (Class I, level C, in the same group).^[1] ANZCOR gives a 5 mmol bolus of magnesium intravenously over 10 min, which may be repeated once, then an infusion of 20 mmol over four hours.^[3]

Branch D — Storm, ICD and ablation

Examiner: A third patient, with ischaemic cardiomyopathy and an ICD, returns with recurrent shocks for monomorphic VT despite chronic amiodarone therapy. What does the ESC say?

Strong answer: If VA has occurred 3 or more times within 24 h (separated by at least 5 min), each requiring termination by an intervention, this is electrical storm. For storm in SHD, the Class I measures in Recommendation Table 9 include mild to moderate sedation to alleviate psychological distress and reduce sympathetic tone, beta-blockers (non-selective preferred) with intravenous amiodarone unless contraindicated, and catheter ablation for storm due to SMVT refractory to AADs. In CAD with recurrent, symptomatic SMVT, or ICD shocks for SMVT, despite chronic amiodarone therapy, ablation is recommended in preference to escalating AADs (Class I, level B).^[1] VANISH supports this: death, VT storm or appropriate ICD shock occurred in 59.1% with ablation versus 68.5% with escalated antiarrhythmic drug therapy (HR 0.72).^[10]

Examiner: Would earlier ablation have helped?

Strong answer: The evidence is mixed. In BERLIN VT, death or unplanned hospitalisation for symptomatic VA or worsening heart failure was not lower with preventive ablation before the ICD than with deferred ablation after 3 ICD shocks (32.9% vs 27.7%; HR 1.09, 95% CI 0.62–1.92; P=0.77). The trial stopped early for futility.^[12] PARTITA, in ischaemic or non-ischaemic dilated cardiomyopathy, found fewer deaths or heart failure hospitalisations with immediate ablation (within 2 months) after the first appropriate shock than with standard therapy (4% vs 42%; HR 0.11).^[13] ESC 2022 says ablation just before or immediately after ICD implantation may be considered in CAD to decrease subsequent VT burden and shocks (Class IIb, level B).^[1]

Branch E — Australia and New Zealand

Examiner: How does ANZCOR handle the stable patient?

Strong answer: For a regular broad-complex tachycardia without adverse features, ANZCOR advises amiodarone 300 mg intravenously over 20–60 min, then an infusion of 900 mg over 24 h. Monitor, seek expert help, and be prepared to cardiovert if adverse signs develop or the arrhythmia persists for several hours. Adverse features that suggest a need for immediate treatment are systolic BP under 90 mmHg, heart rate over 150/min, chest pain, heart failure, or drowsiness or confusion.^[3]

Examiner's notes

• Pass: states VT as the default diagnosis and names at least three ECG criteria from Table 9 of the 2019 ESC SVT guideline.^[2]
• Pass: gives ESC classes for cardioversion, procainamide and amiodarone without mixing them up.^[1]
• Fail: gives intravenous verapamil to a broad QRS tachycardia of unknown mechanism (ESC Class III, level B).^[1]