short P-R syndrome
Introduction
Introduction to short PR syndrome Lown, Ganong, and Levine reported in 1952 a normal QRS graphical electrocardiogram with a short PR interval (<0.12 s) and no delta waves, which may be associated with paroxysmal supraventricular tachycardia or atrial flutter. Atrial fibrillation is associated with a rapid ventricular rate, so it is called short PR syndrome, also known as James bundle pre-excitation syndrome or LGL syndrome. basic knowledge The proportion of sickness: 0.01% Susceptible people: no special people Mode of infection: non-infectious Complications: hypotension, sudden death
Cause
Short PR syndrome
(1) Causes of the disease
Most patients with short PR syndrome have no structural heart disease, and a small number of patients are seen in sinoatrial node disease, mitral valve disease, mitral valve prolapse and cardiomyopathy.
(two) pathogenesis
The anatomical basis of the short PR syndrome is the presence of the James bypass (also known as the atrioventricular node bypass), which is part of the fiber between the posterior internodes, bypassing the top of the atrioventricular node and ending at the lower part of the atrioventricular node or atrioventricular bundle Therefore, the PR interval is shortened and does not directly enter the ventricle, so there is no delta wave, the QRS wave time is normal, and the basic conditions for the reentry are provided, so the atrioventricular nodal reentry tachycardia or rapid atrial fibrillation or atrial flutter can be concurrently performed. However, in recent years, there have been differences in the starting and ending points of the James bundle, even if it really exists.
Prevention
Short PR syndrome prevention
The cause of the attack should be avoided. Causes include exercise, excessive fatigue, emotional agitation, pregnancy, alcohol or excessive smoking. At the same time, it should be noted that this disease can not be engaged in special occupations, such as driving, diving, etc., before the radical cure, so as to avoid accidents when sudden onset.
Complication
Short PR syndrome complications Complications, hypotension, sudden death
Because short PR syndrome is easy to merge with paroxysmal supraventricular tachycardia, and the frequency is faster, it can cause hemodynamic changes, hypotension, atrial tachyarrhythmia (atrial flutter, atrial fibrillation), ventricle Complications such as tremor or sudden death.
Symptom
Symptoms of short PR syndrome Common symptoms Dizziness, palpitations, chest tightness, arrhythmia, tachycardia, shortness of breath, syncope
Patients with short PR syndrome without arrhythmia may have no clinical symptoms, and patients with short PR syndrome with arrhythmia may have corresponding clinical symptoms due to the type of arrhythmia and the clinical background of cardiovascular disease. And hemodynamic changes, such as palpitations, chest tightness, shortness of breath, dizziness, syncope and other symptoms, short PR syndrome with paroxysmal supraventricular tachycardia (AVNRT, etc.), the incidence of WPW syndrome combined with the room The upper tachycardia should be low, only 50% or less, the frequency is very fast, more than 200 times / min, rhythm rules, some patients may have atrial flutter or atrial fibrillation.
Examine
Short PR syndrome check
Electrocardiogram examination
(1) Typical ECG characteristics of short PR syndrome.
The 1P-R interval was <0.12 s (Fig. 1).
The 2QRS wave is normal and there is no delta wave.
The 3P-J interval is shortened.
4 There is no secondary ST-T change.
(2) A detailed description of the typical ECG characteristics of short PR syndrome:
1 short PR syndrome is mainly the shortening of the conduction time in the atrioventricular node, so the PR interval is <0.12s, but most of them are 0.08~0.11s, sometimes the P wave is widened, and even enters the QRS wave, and the PR interval disappears.
2P-R interval <0.12s, not unique to short PR syndrome, should pay attention to identification:
A. Ectopic atrial rhythm, such as the impulse at the end of the sinus near the coronary sinus, the PR interval can be less than 0.12 s, and the coronary sinus pacing atrium can also appear.
B. Isometric room separation, the atrial and ventricular activation is separated and the PR interval is shortened.
C. The PR interval can be prolonged when accompanied by atrial disease.
D. If the atrial contraction occurs, the PR interval will not be prolonged.
E. Short PR syndrome does not show secondary ST-T changes, and if ST-T changes, it is not associated with short PR syndrome.
F. Short PR syndrome, such as combined bundle branch block, QRS wave can be wide.
G. Sometimes the electrocardiographic features of short PR syndrome can disappear and be occult. At this time, the diagnosis is difficult. It is pointed out that some unexplained atrial fibrillation is caused by intermittent short PR syndrome.
(3) Special types of electrocardiogram in short PR syndrome:
1 occult short PR syndrome: Some people think that about 50% of patients with short PR syndrome are usually in a state of concealment, and only in some cases, such as stimulation of atrial premature contraction, atropine test, etc. (Fig. 2, 3,4), the mechanism may be: A.James bundle has a 4-phase block, so the atrial arousal that occurs early may be transmitted to the ventricle in advance, and the relative delayed sinus excitability cannot pass through the James bundle. Downcast, but only through the normal way; B.James bundle has a forward block somewhere, but the atrial rhythm is below the block level, so its excitement can be passed down the James bundle, and located Sinus agitation above the block level is blocked by the James bundle, and atropine is not parallel to the vagus nerve of the atrioventricular and bypass. It has a greater impact on the bypass than on the atrioventricular node. The effective refractory period was once shorter than the effective refractory period of the atrioventricular node. The sinus sensation was preferentially passed through the bypass, and the recessive short PR syndrome was dominant. As the atropine effect disappeared, the two recovered. Their inherent effective refractory period, short PR syndrome will be Sex and become occult.
2 Frequency-dependent short PR syndrome: its characteristics are similar to frequency-dependent WPW syndrome.
3James bundle Nevin phenomenon: similar to the Kent beam period in the Kent bundle.
4 short PR syndrome with arrhythmia: short PR syndrome itself can be associated with arrhythmia, Liang Shoupeng reported 106 cases of short PR syndrome (38%) with arrhythmia, supraventricular tachycardia accounted for 22.5%, pre-atrial contraction accounted for 20%, atrial fibrillation accounted for 20%, pre-contracted area contraction accounted for 7.5%, junctional tachycardia with descending second degree block 2.5%, ventricular premature contraction 12.5%, Pre-atrial contraction + ventricular premature contraction 7.5%, ventricular tachycardia 7.5%, more women than men, 18 of 40 cases have structural heart disease, 55 cases of short PR reported by Beijing Fuwai Hospital Among the syndromes, 13 patients had accelerated atrioventricular node conduction, accounting for 24%, 9 of them were associated with occult and refractory atrioventricular reentry tachycardia, 5 were with atrioventricular nodal pathway, and 1 was atrioventricular Reentrant tachycardia, 3 cases of atrial flutter / atrial fibrillation, 9 cases of atrioventricular node accelerated conduction and cis-type atrioventricular reentry tachycardia, the average circumference of tachycardia was (283 ± 15) ms.
2. Electrophysiological examination features
(1) Features of His bundle electrogram: short PR syndrome, that is, the characteristic of interventricular septal, should be the shortening of the atrioventricular conduction time, more than 90% is caused by the accelerated conduction velocity in the atrioventricular node, called the accelerated room Ventricular conduction, its atrial conduction and He-Pu system conduction are normal, and the AH interval is often less than 60ms.
(2) atrial growth pacing examination: simply using the His bundle beam diagram can not clearly reveal the characteristics of short PR syndrome, can be further confirmed by means of atrial pacing, and certain drug reactions, short PR syndrome After atrial atrial pacing, there are the following characteristics: the effective refractory period of the 1 compartment transition zone is shortened; 2 the compartmental junction conduction velocity is fast, when the atrial pacing frequency increases, that is, when the pacing cycle is shortened, The following three different types of reactions are presented:
1 Type 1: The atrial pacing cycle is shortened, but the LRA-H is not prolonged, or only slightly extended. This suggests that there is a very important short circuit in the atrioventricular junction, that is, the atrial-His beam short circuit. This type of patient may be the easiest. Rapid atrial fibrillation, atrial flutter, etc., have been reported to cause atrial fibrillation when the atrial pacing is 170 times/min.
2 Type 2: As the pacing frequency increases, LRA-H gradually prolongs, but the extension is not very large, often <100ms, when the atrial pacing frequency reaches 200/min, it can still maintain 1:1 room. Ventricular conduction, which suggests a pathway to accelerate conduction in the atrioventricular node, but does not necessarily have an anatomical bypass.
3 The third type: mixed type, that is, when the atrial growth rate is adjusted, when the period starts to shorten, the LRA-H does not change, or is slightly extended; but when the pacing period is shortened to a certain extent, the LRA-H can be suddenly extended. The phenomenon of jumping is formed. This may be due to the fact that there are two different effective refractory conduction channels in the atrioventricular junction area. Some people think that this is the most common type, and it is also a type that is prone to reentry tachycardia.
3. Pre-stimulation of atrial procedure This is very similar to the stimulation response of atrial growth pacing. The most common is that the interatrial interval (A1-A2) is shortened with the atrial pre-stimulation, and the AH interval is slightly extended. Patients with atrioventricular nodal double-path response have more stimuli than atrial pacing, especially when the basic stimulation circumference (S1-S1 and A1-A1) is short, because the basal circumference is short, the refractory period of the atrioventricular node is long. It is easy to reveal the electrophysiological phenomenon of the double pathway of the atrioventricular node. When A1-A2 is gradually shortened, A2-H2 is gradually extended to form a gentle curve, sometimes there is a jumping phenomenon, suggesting that there is a curve of the double path in the atrioventricular node.
Stimulation before the atrial procedure, especially when the base circumference is short, during the stimulation process, the AH, HV interval is short and does not change, suggesting the presence of atrial-His bundle bypass, because the bypass is common myocardium, the basis The short circumference is short and the refractory period is short. Therefore, the pre-existing stimulation does not prolong the conduction time. If the cardiac cycle of the basic heart rhythm is short, the atrial stimulation can lead to a significant extension of A2-H2, indicating that the short circuit is in the atrioventricular node ( Accelerate the fibers or adhere to the atrioventricular node).
4. Drug reaction propranolol can slow the conduction of atrioventricular node, but has no effect on bypass and atrial muscle. After intravenous propranolol, AH is prolonged, suggesting that the short circuit is in the tissue in the atrioventricular node or A short circuit attached to the atrioventricular node.
5. Determination of the effective refractory period of the atrioventricular node compared with the short PR interval (PR<0.12s) with the history of supraventricular tachycardia, the effective refractory period of the atrioventricular node is more effective than the normal PR interval. The period should be slightly shorter, but the difference is not significant, and the accelerated refractory period of the atrioventricular node in patients with accelerated atrioventricular node conduction and the history of supraventricular tachycardia is better than the normal interventricular tachycardia in the PR interval. The history is short.
6. Ventricular conduction short PR syndrome room conduction, that is, the measurement of room retrograde time, showing patients with accelerated conduction of atrioventricular node, their room conduction is good, with or without double path, with or without accompanying room In the case of supraventricular tachycardia, there was no significant difference in the room reversal time. Most patients with atrial-His bundle bypass did not have room conduction, and a few patients with ventricular conduction also had conduction function than the previa. difference.
Clinically, it is often found that some patients have an ECG PR interval of 0.12 s, and the history of paroxysmal supraventricular tachycardia is not very positive. It cannot be diagnosed as LGI syndrome. Electrophysiological examination should be performed at this time.
Diagnosis
Diagnosis and identification of short PR syndrome
The electrophysiological basis for the diagnosis of short PR syndrome mainly includes:
1. The AH interval of the His bundle beam diagram is <60ms, and the HV interval is normal.
2. The increment of PR (or AH) interval during atrial pacing is <100ms.
3. When the atrial pacing frequency is 200 beats/min, it can still be maintained at 1:1.
4. EC interval PR interval 0.12s.
