Wolff Parkinson White Syndrome (WPW)

Wolff Parkinson White Syndrome (WPW) is characterized by an abnormal accessory pathway in the heart leading to arrhythmias.


Pathology: Born with an accessory pathway, the bundle of Kent which connects the atria and ventricle. The electrical impulses from the SA node reach the ventricles earlier via the accessory pathway as there is no AV nodal delay in this pathway. This leads to the preexcitation of the ventricle and initiation of ventricular contraction. This ventricular contraction is prolonged when the impulse via the AV nodal pathway reaches the ventricles.


Most common location of the accessory pathway- between the left atrium and free wall of the left ventricle


ECG changes: 

  • Shortened PR interval(typically <120 ms) - because of the early initiation of ventricular depolarization.
  • Prolonged QRS duration (total duration >0.12 seconds)- because of the AV nodal impulse reaching the ventricles after the aberrant impulse.
  • Delta waves- slurred upstroke of QRS complex
  • ST-segment-T wave (repolarization) changes, generally directed opposite the major delta wave and QRS complex, reflecting altered depolarization.


The given ECG shows delta waves marked with red arrows:


The given ECG is suggestive of Wolff-Parkinson-White syndrome (WPW). Its prevalence decreases with age.


Treatment:

Catheter ablation is the treatment of choice.

Anti-arrhythmic drugs like procainamide, amiodarone, quinidine, propafenone, dofetilide are used in slowing conduction in the accessory pathway (prolong refractory period).

IV procainamide is the drug of choice in a hemodynamically stable WPW presenting with atrial fibrillation. 

DC cardioversion is done in hemodynamically unstable patients.


Rate-slowing drugs such as non-dihydropyridine calcium channel blockers (eg, verapamil, diltiazem), beta-blockers, and digoxin are contraindicated in these patients. They increase the refractoriness of the AV node with minimal or no effect on the accessory pathway. This can lead to faster ventricular rates, increasing the risk of ventricular fibrillation.




Comments

Post a Comment

Popular posts from this blog

Corneal Epithelium

Image
 Layers of the cornea: Epithelium (Stratified squamous non-keratinized epithelium)  Bowman's membrane - Acellular; does not regenerate Stroma (Thickest layer) - The stroma can scar, but cannot regenerate Dua's layer (Newly discovered, toughest layer) Descemet's membrane- Ends peripherally as Schwalbe's ring; has regenerative potential Endothelium (Most metabolically active layer)- does not regenerate  The hydration level and transparency of the cornea is maintained mainly by the endothelial cells of the cornea. If the cornea becomes overhydrated, it begins to scatter light and gradually begins to lose its transparency Endothelium possesses Na+/K+ ATPase, which keeps the corneal stroma in a relatively dehydrated state. This helps in maintaining the transparency of the cornea. Endothelial cells decrease in number with age. Other factors contributing to the transparency of the cornea are as follows:  Regular arrangement of corneal lamellae ( Maurice theory ) Peculiar...
Read more

The Electromagnetic Spectrum

The electromagnetic spectrum, from  low frequency to high frequency  consists of:  Radiowaves  < Microwaves < Infrared < Visible light< Ultraviolet < X-rays <  Gamma rays W. C. Roentgen  is the father of X-ray and the first medical X-ray by Roentgen was of his wife Anna Bertha's left hand. Physicists  Peter Mansfield  and  Paul Lauterbur  developed MRI-related imaging techniques in medicine and they were awarded the Nobel prize in 2003.
Read more