wpw Pathophysiology:

olff-Parkinson-White (WPW) syndrome (WPW syndrome)

(Date :2007-10-24)

Pathophysiology:

Between the atrium and the ventricle due to abnormal embryonic development, resulting in a ride in the atrial and ventricular septal bridge, the bridge between the self-contained articles of atrial and ventricular nerve conduction nerve conduction through the AV node, and under normal circumstances, different routes. Abnormal accessory pathway., And normal nerve conduction delay generated by the AV node in the route, and thus in the heart of patients with premature intensification (preexcitation). Although there are many of the accessory pathway. Preexcitation, but the most common and well-known is the bundle of Kent, we can see in the WPW syndrome. Through of Kent bundle of nerve conduction is anterograde, retrograde, or both of the club.

Frequency:

About 0.15-0.2% of the WPW syndrome.

Mortality / Morbidity:

Due to dysrhythmias or wrong treatment of the WPW syndrome caused mortality of about 0-4%.

Age:

The WPW syndrome heart rate too fast may occur at any age, but increased with age, the accessory pathway nerve conduction velocity slows down, so will show the reduction in the cases of preexcitation on ECG. On ECG understand that demonstrated the WPW syndrome patients, with those age increased opportunity will follow the increase in produce PSVT, such as 20-39 years old is 10%, more than 60 is 36%.

ECG:

The typical ECG manifestations of the WPW syndrome is shortened PR interval of delta wave widened the QRS complex, Through the accessory pathway electrical pulse earlier than passed down through the typical the AV node, electrical impulses reach the ventricle, resulting in a so-called preexcitation.

. As mentioned earlier, ventricular electrical pulse through the accessory pathway. Activated first, the waves exist in a normal electrical pulse conduction, and created a little earlier than low ventricular depolarization can spread to form a so-called delta wave and makes the QRS interval widened, the PR interval is shorter. accessory pathway exist most easily be identified by ECG performance.

. The WPW syndrome. There are two types, namely, the type A or type B Is in accordance of delta wave / the QRS complex, in the shape of the precordial leads distinction. type A delta a wave in all the precordial leads are upright positive in lead V1 R than S; and a wave of type B delta is negative, so the V1 and V2 lead there will be negative delta wave the QRS complex,

type A, the accessory pathway. of electrical impulses by the LA posterior wall of the LV posterior wall, then the V1-V6 delta wave / the QRS complex, are upright positive.

type B, the accessory pathway. the electrical pulse by the RA, or the side into the RV, V2 - V6 delta wave / the QRS complex, are upright positive, but the V1 is negative.

. Occasionally, some cases of the WPW syndrome. Via the accessory pathway. The AV node, electrical impulses reach the ventricle in ECG is normal, no preexcitation. ECG graphics performance is based on the relative velocity of the two electrical pulses of different. This accessory pathway. In ECG, generally is not found, but when the accessory pathway electrical pulse downstream faster than the reaction period of the AV node, the ECG will be found that the accessory pathway. Called latent accessory pathway. . latent accessory pathway. electrical pulses to the anterograde and retrograde conduction.

. There is the only retrograde conduction (retrograde) accessory pathway. Called concealed accessory pathway. This pathway only occurs circus movement tachycardias (CMT) will have a road. Therefore, in the normal ECG, the accessory pathway. Forward conduction (anterograde) will and latent accessory pathway., Do not see any exception.

The WPW syndrome. Cause of arrhythmia:

Although there will be a variety of cardiac arrhythmias in patients with the WPW syndrome. CMT and atrial fibrillation are the two most common. CMT better than the more common.

An early onset of atrial pulsation happens to produce the accessory pathway. In the inactivation of a coincidence, thus causing typical of CMT, when the electrical pulse, extends only to pass down the AV node, but along the accessory pathway retrograde back, namely, anterograde conduction (orthodromic conduction) CMT.

Anterograde conduction (orthodromic conduction) circus movement tachycardias (CMT), a narrow-shaped QRS interval rhythm. Because of electrical impulses through the AV node down conduction, so its shape and rate subject to the control of the AV node. orthodromic type of WPW dysrhythmia, because of rules rhythm with narrow QRS complex tachycardia with PSVT difficult to make a differential diagnosis.

Another is called retrograde conduction (Antidromic) CMTs. There will be a wide QRS, and faster, because most accessory pathways have a relatively short reaction period; They called antidromic, is due to the electrical pulse forward conduction to the ventricle via the accessory pathway. caused preexcitation. By the normal path of conduction through the AV node back to the heart. Belong to the circus, movement, this kind of dysrhythmias regularity. Orthodromic CMTs antidromic CMTs 10-15 times.

Will produce antidromic CMTs accessory pathways conduction of electrical impulses, is reached by the atrium ventricle, the resting ECG QRS can also be found of delta a wave. antidromic CMTs because of the wide QRS, faster and regular speed, and therefore required for the differential diagnosis of ventricular tachycardia, that is, when to see any regular wide-complex tachycardia, it must first rule out the possibility of ventricular tachycardia before think it might be other arrhythmias.

The WPW with atrial fibrillation, 11-38% of the incidence of ventricular fibrillation due to easy to become the most vulnerable to fatal arrhythmias WPW in

Longer normal due to the AV node refractory period allows ventricle pumping not too fast; accessory pathway. Often very short electrical pulses of the forward reaction period, making it easy to produce the corresponding ventricle pumping speed. The WPW with atrial fibrillation, from time to time a lot of electrical impulses transmitted from the accessory pathway. Ventricles, the ECG will be bizarre, wide-complex, irregular of tachycardia, Heart rate 250 bpm.

TREATMENT

In the emergency treatment of:

* Treatment of wpw with atrial fibrillation

With the principle of treatment of atrial fibrillation, the WPW is elongated accessory pathway reaction of this reaction period than the AV node also promote slow down the forward conduction of electrical impulses in the accessory pathway. Ventricle pumping speed followed by a slow down, and a non-atrial fibrillation in the WPW's, which is not the reaction of the AV node slows down.

If the WPW with atrial fibrillation given the AV node response to increasing drug, such as calcium channel blockers, beta-blockers, of digoxin, may cause increased through the accessory pathway conduction velocity, thereby increasing the speed of the ventricular rate, it would be a terrible news, as they may lead to ventricular fibrillation.

If the WPW with atrial fibrillation in the unstable state, hypotensive hypoperfusion, should consider using the synchronized cardioversion.

If the WPW with atrial fibrillation in the stable distribution state, should attempt to use of procainamide (iv) of procainamide (iv) will hinder the accessory pathway., But may also increase the conduction through the AV node. Of procainamide (iv) can be controlled via the accessory pathway. Atrial fibrillation, but may also produce dangerous atrial fibrillation, need plus other drugs, such as the b-blocker, or cardioversion treatment. Can not be processed or handled properly, the WPW with atrial fibrillation, may require cardioversion.

* Treatment of wpw with CMTs

. When the CMTs, the WPW syndrome. With rules and narrow and complex tachycardias, there are many treatments commonly used treatment is cardioversion and of adenosine. If the use of adenosine, need to prepare cardioversion, and other aid kits in case of adenosine-induced AV nodal blockade occurs dangerous.

In a situation of stable, regular, and the narrow the QRS complex tachycardia, did not know whether the WPW syndrome, of adenosine (iv) is the first line treatment. However, in heart transplant patients, patients with severe obstructive lung disease, and wide the QRS complex patients, you can not use. Known to be caused by the WPW syndrome. Use of adenosine (iv), should be equipped with cardioversion / for defibrillation equipment to prepare for contingencies.

Conclusion: QRS complex of the WPW syndrome is whether the law, or irregular, you can distinguish between the CMTs or atrial fibrillation.

If the QRS complex, is regular and narrow, in the case of cardioversion / for defibrillation, this arrhythmia can use of adenosine (iv).

If the QRS complex, is not the law, this arrhythmia like the WPW with atrial fibrillation, the use of adenosine (iv) increase the heart rate, leaving the more serious symptoms, it should be used Cardioversion or procainamide can control heart rate.

When the out-patient drug treatment:

. The WPW syndrome. To make what kind of treatment is to see if it will be what more, if the ECG only shows preexcitation, but never had tachycardia, usually do not have to make the EP (associated with underlying cardiac electrophysiologic studies) or treatment .

. However, if really insisted on treatment wpw syndrome. With preexcitation, just in case, there are three options, that is, drug therapy, electrical (ie, RF) ablation and surgical ablation. Ablation is the first line of treatment for symptoms of the WPW syndrome., It has been replaced by surgical treatment, and the majority of drug treatment. However, drug treatment is useful for some people, such as those of the patients refused ablation, or after a secondary ablation still failed to use the medication should be considered when using the membrane.-Active antiarrhythmic drug (class IC or III) of combined the AV nodal blocker, rather than using an AV nodal blocker, so as not to cause increased heart rate, atrial fibrillation or flutter.

. Order to prevent the WPW syndrome. Often cause episodic tachycardia, and a dangerous increase in heart rate directive with in order to avoid the use of drugs lead to, select and use the two drugs is an ideal way, such as procainamide and verapamil (class IA and IV), quinidine, and of propranolol (class IA and II). Newer drugs, such as Class IC amiodarone, sotalol, is very good and safe drug, but is generally not used for structural abnormalities of the heart patients, and the best combination and the AV nodal blocker.