a) List the ECG criteria that are helpful in distinguishing ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrant conduction. For each listed criterion, indicate which diagnosis it makes more likely. (30% marks)
b) List the specific management strategies that may be used to treat torsades de pointes. (30% marks)
a)
• Capture beats: VT
• Fusion beats: VT
• Concordance in chest leads (or absence of RS complex): VT
• Typical RBBB or LBBB morphology: SVT
• R to S interval >100ms: VT
(Note: there are some more specific criteria from diagnostic algorithms – if correct these should receive credit.)
b)
• Correction of electrolyte abnormalities or hypothermia
• Magnesium
• Isoprenaline
• Phenytoin
• Sodium Bicarbonate
• Lignocaine
• Electrical cardioversion
• Atrial overdrive pacing
• Cessation of provoking drugs
Some of the criteria are somewhat duplicated because the features are listed according to the society guideline being quoted. It makes sense that most of the guideline-makers would agree on such obvious things as "wide QRS" and "regular", etc.
| Criterion | Findings associated with SVT | Findings associated with VT |
| ACC/AHA Guidelines (2003) | ||
| QRS duration | <120 msec | > 120 msec |
| Rhythm | Irregular | Regular |
| A-V relationship | Atrial rate faster than ventricular rate | Ventricular rate faster than atrial rate |
| Axis | Normal, right or left axis | Bizarre axis (+90 to -90) |
| QRS morphology in the precordial leads | Typical RBBB or LBBB | Concordance; no R/S pattern; onset of R to nadir is longer than 100 msec. In RBBB pattern: - qR, Rs or Rr patter in V1 In LBBB pattern: - R in V1 longer than 30msec - R to nadir of S in V1 longer than 60 msec - qR or qS in V6 |
| Brugada algorithm (1991) | ||
| RS complex in precordial leads | Present | Absent |
| R-S interval in one precordial lead | <100 msec | >100 msec |
| A-V relationship | Associated | Dissociated |
| QRS morphology criteria for VT | Not met | Met |
| Brugada QRS morphology criteria for LBBB pattern | ||
| Initial R period | <100 msec | >100 msec |
| S-wave in V1 or V2 |
Normal downwards leg | Slurred or notched downwards leg |
| Q to nadir QS in V1 or V2 | <100 msec | >100 msec |
| Q or QS in V6 | Absent | Present |
| Brugada QRS morphology criteria for RBBB pattern | ||
| R or qR in V1 | Normal | Monophasic |
| R to R' size | R shorter than R' | R taller than R' |
| R in V6 | No Rs | Rs present in V6 |
| Vereckei algorithm (2007) | ||
| A-V relationship | Associated | Dissociated |
| R in aVR | Absent | Present |
| QRS morphology | Like a RBBB or LBBB | Unlike RBBB or LBBB |
| Vi/Vt | Vi (initial QRS upstroke y-axis distance during the first 40 msec) is greater than Vt (terminal QRS downstroke y-axis distance during the last 40 msec of the QRS) | Vi is smaller than Vt |
Management of torsades is somewhat less complex. Thomas and Behr (2015) have published a good article which describes the management strategies for torsades:
Members, Committee, et al. "ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias—executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients with Supraventricular Arrhythmias) developed in collaboration with NASPE-Heart Rhythm Society." Journal of the American College of Cardiology 42.8 (2003): 1493-1531.
Brugada, Pedro, et al. "A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex." Circulation 83.5 (1991): 1649-1659.
Vereckei, András, et al. "Application of a new algorithm in the differential diagnosis of wide QRS complex tachycardia." European heart journal 28.5 (2007): 589-600.
Thomas, Simon HL, and Elijah R. Behr. "Pharmacological treatment of acquired QT prolongation and torsades de pointes." British journal of clinical pharmacology 81.3 (2016): 420-427.