30-year-old male with no significant past medical history who presents with palpitations, what's the diagnosis? (scroll down for answer)

Answer:  Wolff Parkinson White in atrial fibrillation 

Ask yourself, what are the possible rhythms this could be?

• Atrial fibrillation with aberrancy (most common) 
• Atrial flutter with aberrancy 
• Polymorphic ventricular tachycardia
• Wolff Parkinson White in atrial fibrillation 

Treatment considerations:

If the rhythm is a-fib or a-flutter with aberrancy then the next step is to slow down the AV node, BUT what if the rhythm is WPW? Blocking the AV node can send more impulses down the accessory pathway which has no regulatory mechanism to block impulses from going to the ventricles, a step up for ventricular fibrillation. These cases should be treated with cardioversion 

Tips for differentiating a-fib with aberrancy and a-fib with underlying WPW:

• The patient will tell you they have WPW
• Pattern recognition (highly variable ECG with wide and narrow complexes in WPW)
• Rate (the faster the rate the more concerning for WPW, usually rates >200)

ECG findings in WPW:

• PR interval <120 ms
• QRS prolongation >110 ms
• Delta wave
• ST segment and T wave discordance

Additional resources: 

• https://www.emrap.org/episode/c3/cases
• https://lifeinthefastlane.com/ecg-library/pre-excitation-syndromes