Symptoms and common clinical manifestations of cardiac preexcitation syndrome

Cardiac preexcitation syndrome is an abnormal phenomenon of atrioventricular conduction and is also an uncommon disease among arrhythmias. The most important basis for diagnosis is the electrocardiogram, and the symptoms can be well diagnosed through the electrocardiogram. The most common symptom is a rapid heart rate.

(I) Atrioventricular pathway

①The PR interval (essentially the P-δ interval) is shortened to less than 0.12 seconds, mostly 0.10 seconds.

②The QRS time limit is extended to more than 0.11 seconds.

③The beginning of the QRS wave group is blunt and forms a pause with the rest of the wave group, which is called pre-excitation.

④Secondary ST-T wave changes.

The above-mentioned ECG changes can be divided into two types, A and B. The pre-excitation wave and QRS wave group of type A are both upward in lead V1, while the main wave of the pre-excitation wave and QRS wave group of lead B in lead V1 are both downward; the former indicates pre-excitation of the left or right ventricular posterior bottom myocardium, while the latter indicates pre-excitation of the right ventricular anterior wall myocardium. Although this classification method is limited by the variable QRS wave groups caused by bypass pathways in different parts, it helps to distinguish whether the ventricular end of the bypass pathway is left or right, front or back, and is therefore still used today.

(ii) atrial knot,

The PR interval of the atrioventricular bypass is less than 0.12 seconds, mostly within 0.10 seconds; the QRS wave group is normal, with no preexcitation wave. This ECG manifestation is also called short PR, normal QRS syndrome or L,G,L (Lown-Gannong-Levine) syndrome.

(III) Room

The PR interval of the bundle-ventricular connection is normal, the QRS wave group is widened, and there is a pre-excitation wave.

When supraventricular tachycardia with preexcitation syndrome occurs, the preexcitation symptoms mostly disappear, and the electrocardiogram shows supraventricular tachycardia with normal QRS wave group morphology. When it is complicated by atrial flutter or atrial fibrillation, it is not uncommon for the QRS to maintain preexcitation characteristics, and the electrocardiogram shows atrial flutter or atrial fibrillation with malformed and wide QRS wave group; the ventricular rate mostly exceeds 200 times/min, and can even reach 300 times/min. During atrial flutter, there may be 1:1 atrioventricular conduction, and atrial flutter waves may be identified. During atrial fibrillation, the ventricular rhythm is irregular, and after a long interval, individual QRS wave groups can be seen to have normal morphology (which may be due to prolonged refractory period of the bypass pathway, and after the disappearance of latent conduction in the atrioventricular node, all or most of the impulses are conducted through the atrioventricular node), and atrial fibrillation waves may be identified. When the ventricular rate is extremely fast, it may also be accompanied by rate-dependent intraventricular conduction changes.

In addition to the above-mentioned ECG features, the vectorcardiogram can be used as a basis for diagnosis. Its characteristic is that the initial part of the QRS loop on each plane runs slowly in a straight line, which can last up to 0.08 seconds, and then suddenly turns and continues to run at normal speed. The QRS loop running time can exceed 0.12 seconds. The His bundle electrogram and surface or epicardial mapping (mapping) are helpful to identify various impulses and locate the bypass pathway, and play an important role in confirming whether the bypass pathway is involved in the tachycardia reentry loop.