Wide & Regular tachycardia dDx

• Remember there are only 3 main causes of narrow & regular tachycardias, aberrant conduction will cause these rhythms to have a wide complex QRS

• Remember there are only 3 main causes of narrow & irregular tachycardias, aberrant conduction will cause these rhythms to have a wide complex QRS

  • • Looks closely for P waves in all leads (especially V1 & II) to differentiate between the different potential rhythms

• Anything that causes aberrant conduction will turn your narrow complex DDx into your wide complex DDx. Main causes of aberrancy include:

  • • • Bundle branch blocks, pacemakers, LVH

      • Electrolyte, metabolic causes (Hyperkalemia, acidosis, etc.)

      • Toxicologic causes, medications (e.g. TCA's)

      • Accessory pathways

      • Ventricular rhythms

• Wide & regular complex tachycardias should be considered to be VT until proven otherwise

  • • • Use the VTACH mnemonic below to remember potential VT mimics that may change your management

      • Do not rely on the VT vs. SVT criteria

Ventricular Tachycardia (VT)

• Rate usually > 120-130 bpm, and not too wide (QRS < 200 ms)

• Should be regular in rhythm

Sinus tachycardia with TCA/Na⁺ channel blocker toxicity

• Look carefully for P-QRS complexes, often really wide (QRS > 200 ms)

• May have Brugada patterns in aVR and V₁

SVT with aberrant conduction

• No clear P-waves, consider VT!

• The ECG can not reliably distinguish between VT and SVT with aberrant conduction

  • The ECG is reliable at ruling in VT

  • The ECG is unreliable at ruling out VT (i.e. at ruling in SVT with AC)

Sinus Tachycardia with aberrant conduction (e.g. BBB, WPW)

• Look carefully for P-QRS complexes in all leads

Hyperkalemia

• Look carefully for P-QRS complexes, often really wide (QRS > 200 ms)

• May have Brugada patterns in aVR and V₁

Massive STEMI

• Look carefully for P-QRS complexes, confirm that QRS is wide in all leads

• Rightward axis weighs against STEMI

DDx for RRWCT (QRS > 200 ms, or > 1 big box)

• Toxicological and metabolic disturbances like hyperkalemia and Na⁺ channel blocker toxicities can cause RRWCT’s that mimic Ventricular Tachycardia

• Lidocaine, amiodarone, and procainamide all have Na⁺ channel blocking properties and can worsen toxicities

• Consider empiric treatment with calcium and bicarb before antiarrhythmics which can kill these patients!