Do all patients with an accessory pathway have a delta wave WPW pattern on their baseline electrocardiogram

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No. Many accessory pathways conduct only in a retrograde fashion (from ventricle to atrium) or have very slow antegrade (atrial to ventricular) conduction.

These patients may or may not have narrow-complex SVT (AVRT). In contrast, some patients have a delta wave on the baseline ECG with no clinical symptoms. In many cases these asymptomatic patients do not need pharmacologic treatment or invasive electrophysiologic testing.

26. A 25-year-old patient presenting with palpitations is noted to have a wide-complex, irregular tachycardia at a rate of 260. The upstroke of the QRS is slurred. The blood pressure is normal, and the patient appears well. What is the most likely diagnosis? What treatments are indicated? What treatments are potentially harmful?

This is probably a case of atrial fibrillation with WPW syndrome (Figure 30-2). The wide QRS is a result of conduction down the accessory pathway from the atrium to the ventricular myocardium. In an unstable patient electrical cardioversion is warranted. In a stable patient amiodarone or procainamide would be reasonable. In these patients avoid using digoxin, calcium blockers, adenosine, and p-blockers. Heart rate may actually increase, and ventricular fibrillation has been reported from AV nodal blocking agents. Elective radiofrequency ablation of the pathway is indicated. This is a percutaneous catheter-based approach that is performed by a cardiac electrophysiologist.

Afib Conduction

Figure 30-2. Irregularly Irregular wide complex tachycardia In a young patient with Wolff-Parkinson-White syndrome and atrial fibrillation. The QRS complex is wide because the ventricles are activated via an accessory pathway rather than the atrioventricular (AV) node. Drugs that primarily block the AV node such as digoxin, diltiazem, verapamil, p-blockers, and adenosine are contraindicated in this situation because they may precipitate ventricular fibrillation.

Figure 30-2. Irregularly Irregular wide complex tachycardia In a young patient with Wolff-Parkinson-White syndrome and atrial fibrillation. The QRS complex is wide because the ventricles are activated via an accessory pathway rather than the atrioventricular (AV) node. Drugs that primarily block the AV node such as digoxin, diltiazem, verapamil, p-blockers, and adenosine are contraindicated in this situation because they may precipitate ventricular fibrillation.

27. Why is it important to save electrocardiogram tracings that document an arrhythmia?

A cardiologist or cardiac electrophysiologist will be able to give much more meaningful advice if the arrhythmia can be properly diagnosed. The initiation and termination of the event may help to determine the specific type of arrhythmia. General descriptions of the arrhythmia such as bradycardia, or wide complex tachycardia may not be enough to enable specific treatment.

Artifact cannot be diagnosed unless the actual tracing is available for analysis. Finally, third-party payers (such as insurance companies) may be reluctant to reimburse for devices such as pacemakers and defibrillators unless there is proof of an arrhythmia.

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