Preexcitation syndrome

WOLF PARKINSON WHITE

W P W

Preexcitation syndrome (ECG)

Paroxysmal arrhythmias

The heart is a muscular pump that releases (filling) and contracts (emptying) about 100,000 times a day. Its function is to receive blood from the general circulation and the pulmonary circulation, and pump blood into the pulmonary circulation and received into the general circulation.

The heart has 4 chambers. The two upper atria receive blood, then it passes into the two lower chambers, the ventricles through the atrioventricular valves, and the same ventricles, contracting, sending blood into the pulmonary circulation and received into the general circulation.

The contractile function of the atria only serves to fill the best the ventricles, and the function of the ventricles instead serves to push the blood in the arteries to get him in all tissues. It 'is therefore clear that the atrial muscle pump must not develop large pressure to push the blood into the ventricles, while the ventricular muscle pump will need to develop very high pressures, especially to the left, to push the blood in all arteries. We will then have a relatively thin atrial muscle and ventricular muscle of a different consistency: in the final two completely different muscle pumps. For these reasons, the heart is a muscular pump only, but is, in fact, 2 muscular pumps, the atrial and ventricular.

And, as their function and activation times and different ways, these two muscular pumps must be separated. And, indeed they are, because the atria and ventricles are separated as a total body muscle and united as the heart, from a fibrous structure, the fibrous trigone (including rings fibrosis of the atrioventricular valves). There is then, and there should be no continuity muscle, even in small bundles, between the atria and ventricles.

It is not always so: in the remaining 3% of cases of small muscle bundles connecting the atrial and ventricular muscle. These bundles, although small, are able to transmit the impulse started from the sinoatrial node. The problem is that these beams lead the impulse quickly and thus have not run decrementing (slow) as the atrio-ventricular node, and thus can be dangerous, because the impulse from the sinus node atrial will be transmitted to the ventricles not passing through the AV node, but for the "shortcut" [561] activating the ventricles first impulse was to come to the normal route, and CPSI will give rise to reentry circuits that can cause paroxysmal tachycardia. In the case then that is generated in the structures supraventricular arrhythmia a high frequency, this will be rapidly transmitted to the ventricles thus being able to cause a potentially fatal arrhythmia such as ventricular fibrillation

In summary, the sino-atrial impulse reaches the ventricles via the atrioventricular node of the usual, but will join them, even before that, through these small anomalous bundles (a bundle of KENT, JAMES beam, beam MAHAIM). There will be a pre-excitation of the ventricles through these abnormal small bundles, which are like a shortcut, before normal excitation. This, causing eccanismi of "return" of the pulse, can lead to serious ventricular arrhythmias crisis, such as ventricular fibrillation.

VENTRICULAR PRE-EXCITATION

It has the pre-excitation syndrome when an atrial impulse activates all or part of the ventricle (antegrade conduction), or when a ventricular impulse activates all or part of the atrium (retrograde conduction), ahead of time that would be expected if the pulse was normally conducted through the streets of the conduction system.

This premature activation is caused by muscle bridges between the atria and ventricles, bridges composed of cardiac muscle fibers. These bridges are present outside of the specialized conduction system, and, connecting the atrium and the ventricle bypass the AV node and its normal conduction delay.

These streets are called "incidental" and are responsible for all varieties of pre-excitation syndrome.

The ECG shows a PR of less than 120 milliseconds and a QRS-shaped delta ("delta wave, Delta wave").

There is talk of pre-excitation hidden when there are ECG changes of any kind: this because the accessory pathway conducts only in the anterograde direction.

In WPW rhythm is regular, but the frequency is increased up to 150-200 beats per minute, with a characteristic of sudden onset and equally sudden cessation.

This is the Wolf Parkinson White Syndrome, characterized, in the ECG [563], a short PR and a look of unusual and aberrant QRS (delta wave), with the appearance of a letter of the greek, the delta . Not all patients with ventricular pre-excitation paroxysmal arrhythmias occur, and the WPW should characterize those patients who have both the one and other.

The accessory conduction pathways [560] [561] [562] [563] have bidirectional conduction (atrio-ventricular and ventriculo-atrial) in 60% of cases and conducting one-way (ventriculoatrial, or retrograde) in 40% of cases.

The treatment of WPW with radiofrequency catheter ablation (RF-ATC) is mainly indicated in patients with secondary to WPW accessory pathway with rapid anterograde conduction.