What is Compartment Syndrome?

Pre-excitation alone is asymptomatic. Concurrent supraventricular tachycardia is similar to general supraventricular tachycardia. In patients with atrial flutter or atrial fibrillation, the ventricular rate is about 200 beats / min. In addition to palpitations and other discomforts, shock, heart failure and even sudden death may occur. When the ventricular rate is extremely fast, such as 300 beats / min, auscultatory heart sounds can only be half of the ventricular rate on the ECG, suggesting that half of ventricular agitation cannot produce effective mechanical contraction.

Preexcitation syndrome

Pre-excitation is an abnormal phenomenon of atrioventricular conduction. Impulse is transmitted through the additional channel, which excites part or all of the ventricle early, causing some ventricular muscles to excite in advance. Those with pre-excitation are called pre-excitation syndrome or WPW (Wolf-Parkinson-White) syndrome, often with supraventricular paroxysmal tachycardia. Pre-excitation is a rare type of arrhythmia, and diagnosis is mainly based on electrocardiograms.

Preexcitation Syndrome

Causes of Preexcitation Syndrome

Congenital atrioventricular additional channels (referred to as bypass) exist outside the normal atrioventricular conduction system. Most patients have no organic heart disease. It is also found in certain congenital and acquired heart diseases, such as tricuspid valve downward movement and obstructive cardiomyopathy. Electrophysiological research proves that the bypass has a fast conduction speed, and the atrial impulses pass down the bypass quickly, reaching the ventricular end of the bypass in advance, and excite the adjacent myocardium, which causes the ventricles to excite in advance and change the normal excitation sequence of the ventricular muscle. The QRS complex on the electrocardiogram is deformed with a pre-shock ( wave) at the beginning. The rest of the atrial impulse can pass down the normal path, and merge with the ventricular excitement caused by the bypass to form a ventricular fusion wave. The shape of the ventricular fusion wave is determined by the refractory period of normal and bypass. The normal pathway should not have a long period, or most impulses are conducted along the bypass, the QRS deformity is obvious; the long bypass should not, the ventricular fusion wave is close to normal.

There are two conduction pathways in the atrioventricular compartment of patients with preexcitation syndrome, which are prone to reentry and reentrant tachycardia. During tachycardia, most of them pass through the bypass and pass down the normal channel, so the QRS complex of tachycardia is normal. Occasionally, impulses pass through the bypass and pass back through the normal channel, causing QRS when tachycardia occurs. The wave group is pre-excited. Pre-excitation patients may also have atrial fibrillation or atrial flutter attacks, which are mostly caused by impulsive retrograde transmission and reaching the atrium during the vulnerable period of the atrium. In atrial flutter and atrial fibrillation, the impulse conducts in the tissue at the junction, prompting most or all of the impulses to pass to the ventricle. Atrial flutter or atrial fibrillation with extremely fast ventricular rate and QRS complex may sometimes develop into ventricular fibrillation. The one-way block of bypass (mostly the down-pass block) can make the ECG without preexcitation, but it has recurrent episodes of supraventricular tachycardia; electrophysiological studies can confirm that the bypass is involved in the return of tachycardia. The second degree conduction block of the bypass can cause intermittent appearance of pre-excitation on the ECG. The following types of bypasses are known, and multiple bypasses can be used for the same patient: atrioventricular bypass (Kent bundle). Mostly located on the left and right sides of the atrioventricular sulcus or the septum, connecting the atrial muscles and ventricular muscles; atrial node pathway (James pathway). It is the channel between the atrium and the lower part of the atrioventricular node or the atrioventricular bundle, which may be formed by the fibers of the posterior internode bundle; the nodule and the bundle chamber connection (Mahaim fiber). It is the pathway connecting the distal end of the atrioventricular node or the proximal end of the atrioventricular bundle or bundle branch to the ventricle. Atrioventricular by-pass is the most common of the three.

Clinical diagnosis of preexcitation syndrome

Pre-excitation syndrome without pre-excitation is asymptomatic

Concurrent supraventricular tachycardia is similar to general supraventricular tachycardia

Performance of different bypasses from anatomy, electrocardiogram, and Sis bundle . In patients with atrial flutter or atrial fibrillation, the ventricular rate is about 200 beats / min. In addition to palpitations and other discomforts, shock, heart failure and even sudden death may occur. When the ventricular rate is extremely fast, such as 300 beats / min, auscultatory heart sounds can only be half of the ventricular rate on the ECG, suggesting that half of ventricular agitation cannot produce effective mechanical contraction.

ECG vector diagram diagnosis of preexcitation syndrome

In addition to the features of the electrocardiogram, the electrocardiogram vector diagram can be used as a diagnostic basis, which is characterized by the slow start of the QRS ring on each face running in a straight line, which lasts for 0.08 seconds, and then suddenly turns and continues to run at normal speed. The QRS ring run time can exceed 0.12 seconds. Heath beam electrocardiogram and body surface or epicardial mapping help identify various types of pre-excitation and localization of the bypass, and play an important role in determining whether the bypass is involved in the tachycardia reentry loop. The pre-excitation pattern on the ECG should be distinguished from bundle branch block, ventricular hypertrophy or myocardial infarction. Shortening of the PR interval and the presence of pre-excitation waves can be confirmed as pre-excitation. When the accelerated ventricular spontaneous rhythm and sinus rhythm are interfering with atrioventricular separation (especially when the ventricular rate is similar to the sinus heart rate), short-term PR intervals may be shortened, and the QRS complex may be broadly deformed. Sexual pre-excitation; but long records can often show that the PR interval is not fixed and the atrioventricular separation is not difficult to distinguish from pre-excitation. When pre-excitation is accompanied by supraventricular tachycardia, the QRS complex is often not widened, but after the onset of interruption, there are characteristic ECG changes other than occult pre-excitation. When pre-excitation is accompanied by atrial fibrillation or atrial flutter, the QRS complex is often Widening should be distinguished from ventricular tachycardia.

Pre-excitation syndrome test

ECG performance

The characteristics of the electrocardiogram caused by pre-excitation of each bypass are as follows.

(1) The atrioventricular path The PR interval (essentially the P- interval) is shortened to less than 0.12 seconds, mostly 0.10 seconds; The QRS time limit is extended to more than 0.11 seconds; The beginning of the QRS complex is blunt, and the rest Formation of a frustration, the so-called pre-excitation secondary ST-T wave changes.

Preexcitation syndrome

The ECG changes mentioned above can be divided into A and B types. Both the pre-excitation wave and QRS complex of type A are upward in lead V1 (Figure 3), while the main wave of pre-excitation wave and QRS complex of lead B of type V1 are both downward; the former indicates the left ventricle or right ventricle. Posterior bottom myocardial preexcitation, which in turn suggests anterior ventricular myocardial premuscle. Although this classification method is limited by the pre-excitation caused by the variable QRS complexes of the bypass in different parts, it helps to distinguish the ventricular end of the bypass from left or right, anterior or posterior, and is still used today.

Type A pre-excitation syndrome shows V1 pre-excitation and QRS complex main wave upward

(2) The PR interval of the atrial node and Fangxi side road is less than 0.12 seconds, most of which are 0.10 seconds; the QRS complex is normal and there is no pre-shock. This ECG manifestation is also known as short PR, normal QRS syndrome, or L, G, L (Lown-Ganong-Levine) syndrome.

LGL syndrome

(3) The PR interval between the nodal chamber and the beam chamber is normal, the QRS complex is widened, and there are pre-shocks.

Pre-excitation tachycardia onset of pre-excitation syndrome, the pre-excitation manifestation mostly disappeared, and the electrocardiogram showed a QRS complex with supraventricular tachycardia (Figure 5). It is not uncommon for QRS to maintain pre-excitation characteristics during concurrent atrial flutter or atrial fibrillation (Figure 6). The ECG manifests a wide atrial flutter or atrial fibrillation with a QRS complex; the ventricular rate mostly exceeds 200 beats / min, or even 300 / min. Atrial flutter can present 1: 1 atrioventricular conduction and may identify atrial flutter waves. The ventricular rhythm is irregular during atrial fibrillation, and individual QRS complexes can be seen to be normal after a long interval (probably the bypass refractory period is prolonged, after the hidden conduction in the atrioventricular node disappears, all or most of the impulses pass through the atrioventricular node Cause) and may identify atrial fibrillation. When the ventricular rate is extremely fast, it can also be accompanied by frequency-dependent changes in intraventricular conduction.

Pre-excitation syndrome with supraventricular tachycardia. Left: Sinus rhythm pre-excitation performance. Right: Supraventricular tachycardia onset. QRS complex morphology is normal.

Pre-excitation comprehensive film with atrial fibrillation Left: Atrial fibrillation onset, ventricular rate 167-300 beats / min, average 210 beats / min, significantly irregular Right: sinus rhythm, with typical pre-excitation performance.

Pre-excitation Syndrome Treatment

Preexcitation syndrome Pre-excitation itself does not require special treatment. When concomitant supraventricular tachycardia, the treatment is the same as general supraventricular tachycardia. For patients with atrial fibrillation or atrial flutter, such as those with fast ventricular rate and circulatory disturbance, synchronous DC cardioversion should be adopted as soon as possible. Lidocaine, procainamide, propafenone, and amiodarone slow the conduction of the bypass, which can slow the ventricular rate or return the atrial fibrillation and atrial flutter to sinus rhythm. Digitalis accelerated bypass conduction, and verapamil and propranolol slowed intraventricular nodal conduction, which may significantly increase the ventricular rate and even develop ventricular fibrillation, so it should not be used. If supraventricular tachycardia or atrial fibrillation and atrial flutter are frequent, the above-mentioned antiarrhythmic drugs should be applied orally to prevent seizures for a long time. Those who cannot control the drug, determine that the bypass refractory period is short or that the bypass refractory period is shortened during rapid atrial pacing, or that the ventricular rate reaches about 200 beats / min during the onset of atrial fibrillation. , Laser or cryoablation, or surgery to cut off the bypass to prevent indications for seizures.

If the QRS wave is normal, the P-R interval is regular, and the heart rate is about 200 beats / min. It should be considered as repetitive tachycardia. The treatment is the same as that of general supraventricular tachycardia. , ATP, or digitalis, if the QRS complex is abnormal and the R-R interval is significantly irregular, it should be suspected and pre-excited with atrial fibrillation, you should choose cardiac rhythm, procainamide, or quinidine and experience An combined use, while isopadine, digitalis and ATP, because the latter three can shorten the bypass refractory period and accelerate bypass conduction, and even ventricular fibrillation occurs.

For patients with frequent episodes of supraventricular tachycardia and obvious symptoms, electrophysiological examination should be performed to identify the side-channel site and then use electrical ablation, radiofrequency ablation, or surgical treatment.

Pre-excitation Syndrome Care

Theoretical analysis of pre-excitation syndrome

Preexcitation syndrome The so-called "pre-excitation syndrome" has a kind of rapid arrhythmia, that is, the heart beats particularly fast at the time of onset, with a frequency of about 180 to 200 beats per minute. It is more common in young adults, suddenly onset, and disappears suddenly. Each episode is as short as a few minutes and as long as several hours and days. In addition to feeling that the heartbeat cannot slow down, the patient also has chest tightness, chest pain, dizziness, and even syncope. As long as the diagnosis is clear, it is easier to control, but it is extremely difficult to cure the root, and often has a history of recurrent attacks. "Spontaneous supraventricular tachycardia", "preexcitation syndrome" is diagnosed when there is no seizure. The so-called "pre-excitation syndrome" is a diagnostic term on the electrocardiogram. From the above, it is known that myocardial contraction is controlled by the sinoatrial node electrical signal. It is also known that the transmission path between signals is normally unique and is called AV node. Patients with pre-excitation syndrome have one or more pathways in addition to the atrioventricular node between the atria and the ventricle. This is called an additional conduction beam. When the pacing signal of the sinoatrial node passes through the atrioventricular node to excite the ventricle, The other extra channel passed back. The returned electrical signal did not disappear. When the atrium and ventricle contracted, this signal was transferred to the atrium through the atrioventricular node to make the ventricle contract again and repeat the cycle, just like a donkey grinds tofu, and when there is no soy in the mill, the master does not Tell it to stop, it keeps turning around the mill.

Pre-excitation syndrome prevention strategy

Preexcitation syndrome The basis of this tachycardia is an extra pathway. This pathway is natural and exists when the embryo is present. A normal heart has a fibrous ring in the middle to divide the heart into two parts. The upper part is called the atrium and the lower part is called the ventricle. The fibrous ring is non-conductive, and there is only one channel in the middle that connects the atrium and ventricle, and conducts electrical signals. The pre-excitation patient has a fissure left by the atrioventricular fibrous ring hypoplasia during the embryo, which is embedded with a normal atrial or ventricle. Ventricular muscle fibers, which conduct electricity. Therefore, the principle of treating this disease is to block or block the conduction of additional pathways with drugs, inhibit tachycardia, and restore sinus rhythm. In fact, it is not difficult to block the conduction of signals from additional pathways. The problem is that Since this pathway exists objectively, it is extremely easy to relapse once the drug is discontinued. Therefore, many cardiovascular physicians advocate preventing medication before onset, but after all, the drug has side effects on the body, and long-term medication is obviously not good for the body. The catheter is inserted from the surface of the human body into the tube to the additional conduction beam of the heart, and then cauterized with high-frequency current to block the conduction beam and achieve the goal of radical cure. The conduction beam can also be cut directly by surgery for radical cure. But one thing needs to be said, isn't all tachycardia a pre-excitation syndrome? There are many reasons for tachycardia. There are many types. Pre-excitation syndrome is just one of them. Moreover, the principle of medication for different types of tachycardia is completely different, and some are even the opposite. Therefore, distinguishing the type of tachycardia is a prerequisite for safe and effective treatment.

If you do nt use ECG, it is very difficult. Because of the different types, the consequences will be very different. Some jumps are not dangerous for a few days, while others are about to die in a few minutes. You must fight against the clock every second, so when tachycardia occurs Need to do an electrocardiogram immediately. On the electrocardiogram, the doctor can determine what tachycardia is, which part of the heart is tachycardia, and how dangerous it is, so as to achieve effective symptomatic treatment and symptomatic treatment. ^[1]