Intra-atrial reentrant tachycardia

Introduction to atrial reentry tachycardia Intra-atrial reentrant tachycardia (IART) is also known as pre-systolic atrial tachycardia and paroxysmal atrial tachycardia. It is a rare paroxysmal supraventricular tachycardia. basic knowledge The proportion of the disease: 0.001% - 0.002% (can directly lead to pre-excitation syndrome by this disease) Susceptible people: no special people Mode of infection: non-infectious Complications: syncope, shock, heart failure

Atrial reentry tachycardia

(1) Causes of the disease

Most of the causes are pathological. About 50% of patients with recurrent tachycardia have organic heart disease. The cause may be ischemia, inflammation, fibrosis, amyloidosis, or atrial dilatation (such as left and right atrial pressure). Unbalanced, or one side of the blood, etc., so that atrial conduction fibers can not be correspondingly elongated, acute myocardial infarction complicated by reentry tachycardia is very rare, reported by Beijing Fuwai Hospital, the incidence rate of 6.9%, the literature The report is 2% to 7%. IART is not caused by myocardial infarction, but it should be considered that myocardial infarction can increase the original abnormal electrical activity. If the heart rate is >160 beats/min, the duration is longer, the hemodynamics can be made. Significant changes, increased mortality in the acute phase, IART can be combined with 2:1, 3:1 atrioventricular block, etc., more common in digitalis poisoning, about 30% of patients found no organic heart disease.

(two) pathogenesis

The heterogeneity of conduction velocity and refractory period in the atrium provides the necessary conditions for the generation of reentry tachycardia in the room. The return loop is confined to the atrium, and the impulse is transmitted from the intraventricular reentry loop. The atrial depolarization pathway The change of P wave is different from that of sinus and changeable. The order of ventricular depolarization has not changed. The depolarization of the atrioventricular node-Xi-Pu system is normal. Therefore, the QRS wave morphology and time limit are normal, and the reentry ventricular tachycardia is normal. Velocity is a kind of pre-systolic tachycardia caused by excitement in the room. It is often expressed as sudden and sudden, so it is also called paroxysmal atrial tachycardia. It can be called spontaneous atrial tachycardia. Contraction induction, especially in the atrial premature contraction, is more easily induced in the atrial muscle vulnerable period, and can be repeatedly induced and terminated by atrial pacing.

Through the results of intracardiac electrophysiological examination and radiofrequency ablation of IART, it is found that the origin of the activation of IART in the atrium is more complicated, for example, originating from the right atrium, the site can be above the His bundle, the superior vena cava, the right atrial appendage, and the lower cavity. Venous, coronary sinus ostium, terminal sputum; originated from the left atrial side, the site can be in the pulmonary vein, left atrial appendage, ablation target can be in the right atrial front wall, middle side wall, back side wall, next to the His bundle, the middle Interval, etc.

Atrial reentry tachycardia prevention

1. During chronic treatment, drug therapy may control recurrence by directly acting on the reentry loop, or by inhibiting triggering factors, such as spontaneous premature contraction. The indications for chronic drug treatment include frequent episodes, affecting normal life or severe symptoms. Patients who are unwilling or unable to receive catheter radiofrequency ablation may be treated with medication for occasional, episodes of short-lived, or mild symptoms, or medication when needed for a tachycardia episode.

2. The inhibitory effect of drugs on reentry can be offset by sympathetic excitation. In physical activity and anxiety, the effects of drugs almost disappear, so avoid mental stress or excessive fatigue in daily life and work, and make life rules Regular living, mental optimism, and emotional stability can reduce the recurrence of the disease.

3. Avoid spicy food, stimulate food, quit smoking, coffee, food should be light.

Complications of atrial reentry tachycardia Complications, syncope, heart failure

If the original underlying heart disease or seizure time is too long, it can often affect hemodynamics, syncope, shock, and heart failure.

Atrial reentry tachycardia symptoms common symptoms tachycardia conduction block palpitations chest tightness indoor conduction block

More common in patients with organic heart disease, IART attacks have palpitations, chest tightness and other symptoms, the heart rate can be 100 ~ 150 times / min, but also up to 160 ~ 200 times / min, the attack is sudden, sudden The characteristics of the end, individual can be a chronic continuous process, tachycardia interval is not fixed, can be separated by a few seconds, hours, days, weeks or even years.

Examination of atrial reentry tachycardia

1. ECG features:

(1) Typical ECG features:

13 or more continuous and frequent P' waves (pre-atrial contraction) appear before the QRS wave, RP'/P'-R>1, and the P' wave is rare after the QRS wave, P' The wave morphology is different from the sinus P wave, and the P'-R interval is directly affected by the frequency of tachycardia.

2 frequency 100 ~ 150 times / min, individual can be greater than 160 times / min, P'-P' interval rules, mostly paroxysmal, that is, sudden sudden stop.

The 3QRS morphology is normal, the time limit is 0.10s, and the RR interval is equal.

4 can be induced or terminated by timely atrial premature contraction.

The first ectopic P' wave at the onset of attack occurred prematurely: the interval between the two groups was equal (PP' interval) at each episode.

6 methods of stimulating the vagus nerve: such as carotid sinus compression (CSM) can not terminate tachycardia, but can induce IART.

7 can be combined with atrioventricular block, so that the ventricular rate is slower than the atrial rate, but the tachycardia does not end.

(2) A detailed description of a typical electrocardiogram:

1 The P' wave shape at the tachycardia is generally consistent with the P' wave of the atrial premature contraction seen during the seizure interval. The ectopic pacemaker is often located in the upper part of the atrium, and the excitatory depolarization is performed from top to bottom. In the II, III, aVF lead P' wave erect, but the P' wave shape can also be inconsistent, can change with the change of the site of the reentry in the room, the order of atrial depolarization can also vary from person to person, if ectopic The beat point originates from different parts of the atrium, and the P' wave shape is also different. For example, the IART originating from the left atrium, the P' wave of the aVL lead is negative or isoelectric; the IART originating from the superior vena cava, the aVL lead is also It is negative, but its I lead P' wave is positive; Koch triangle IART, aVL, I lead P' wave are positive, II, III, aVF lead P' wave are negative (individual II guide In addition, the shape and electric axis of the P' wave also depend on the position of the reentry ring. For example, the right atrial IART displays the horizontal axis from right to left (P'V1 negative, P'V5 Positive); left atrial IART shows transverse electrical axis from left to right (P'V1 forward, P'V5 negative); frontal axis from top to bottom (P'II, P'III, P'aVF positive), The hint originates from the upper part of the atrium; the frontal axis from the bottom up (P'II, P'III, P'aVF negative direction) suggests a origin in the lower atrium.

The atrial rate of 2IART can also be 160 to 200 times/min.

3IART is mostly paroxysmal, but also has a chronic continuous process, but it is rare. The interval between tachycardia episodes is uncertain. It can be separated by a few seconds, hours, days, weeks or even years.

4 ventricular tachycardia, the sinus node was also depolarized and temporarily lost their pacing function, so after the termination of tachycardia often there is an interval until the sinus node pacing function is restored, this paragraph The interval is called the overspeed suppression time. The longer the time, the more obvious the inhibition of the sinus node or the dysfunction of the sinus node itself.

5 The atrial premature contraction induced by IART did not prolong the P'-R interval, and the P' wave was fixed before the QRS wave, but it may be slightly different due to heart rate changes, RP'>1/2R-R.

6 Because IART is only confined to the atrium, the prolongation of P'-R interval and the occurrence of atrioventricular block do not affect the persistence of IART.

7 Atrial rate can be accompanied by atrioventricular block, often accompanied by atrioventricular block in IART, which is caused by rapid heart rate, atrioventricular conduction tissue is still in a functional refractory period, when the atrium When the rate is >200 times/min, it often shows 2:1 atrioventricular block, which is a physiological protection mechanism, so that the ventricular rate is not too fast, such as atrial rate <200 times / min concurrent with second room The conduction block suggests a lesion in the atrioventricular node, and the atrial rate is usually less than 200 beats/min, and is usually 1:1 normal conduction.

The QRS wave morphology of 8IART is similar to the QRS wave morphology of sinus rhythm. When the QRS wave of sinus rhythm shows myocardial infarction pattern, bundle branch block, etc., the QRS wave of IART also changes.

9IART may be accompanied by indoor differential conduction, because the P' wave is transmitted to the bundle branch, one side bundle branch has resumed the conduction function, and the other side bundle branch has not left the refractory period, then the atrial tachycardia may occur. Indoor differential conduction with right bundle branch block is the most common, and indoor differential conduction with left bundle branch block is rare.

10IART may be associated with secondary ST-T changes, ventricular tachycardia due to shortened ventricular diastolic phase, reduced coronary perfusion, causing transient myocardial ischemia, resulting in ST segment depression, T wave inversion, if the original coronary artery disease It is more prone to occur. This ST-T change indicates insufficient blood supply to the coronary arteries. Sometimes, even after tachycardia is terminated, ST-T changes can last for hours or days. This is called "post-tachycardia syndrome". It is as important as the exercise test.

11 sick sinus syndrome can often be combined with IART, which is called slow-fast syndrome.

Carotid compression has different effects on IART, 25% can be terminated. They are all right atrium reentry. Heart rate often slows down before tachycardia is terminated. Carotid sinus compression can also cause delay and block, but these are related to heartbeat. It does not matter if the overspeed is terminated.

If the ECG at the beginning and end of the IART episode is not recorded, it is difficult to distinguish it from autonomous atrial tachycardia.

2. Characteristics of electrophysiological examination: electrophysiological diagnostic criteria for reentry tachycardia in the room:

(1) Atrial premature contraction stimulation is induced by atrial conduction delay in the atrial relative refractory period.

(2) The conduction order of A(P') waves is different from that of sinus beats.

(3) The length of A to H interval is related to the frequency of IART. The interval of AH is short, and the speed of reentry is fast, but the relative period is relatively increasing and prolonged with frequency acceleration.

(4) With atrioventricular block or Hip-Pu block and bundle branch block, it does not affect the onset and duration of IART.

(5) The application of atrial endometrial mapping and atrial pacing can determine the location of the reentry loop, the direction and sequence of activation.

(6) Stimulation of the vagus nerve can induce IART, but does not terminate the episode. There are reports that the seizure can also be terminated for individual patients.

Diagnosis and diagnosis of atrial reentry tachycardia

diagnosis

1. Timely atrial premature contraction can induce and terminate the seizure.

2. The frequency is usually 100-150 times/min, and the part can be >160 times/min.

3. P' wave appears in front of the QRS wave, bursting and bursting.

4. Methods of stimulating the vagus nerve (such as carotid sinus compression, most can not terminate tachycardia).

5. Can be combined with atrioventricular block to make the ventricular rate slower than the atrial rate, but the tachycardia does not end.

Differential diagnosis

1. Identification of atrioventricular nodal reentry tachycardia: retrograde P-wave of slow-fast atrioventricular nodal reentry tachycardia after QRS, R--P interval <PR-interval, RP-interval Period <70ms. There are also some P-waves buried in or in front of the QRS. In the fast and slow atrioventricular nodal reentry tachycardia, the P-wave is after the QRS, before the next QRS, and during the PR interval <RP interval. If the beginning and ending of atrial tachycardia can be recorded, it will be beneficial to the identification of the two.

2. Identification of pre-transmission reentry tachycardia: under normal circumstances, the refractory period of the atrioventricular node is about 300ms, and the individual can be <240ms. Therefore, when the reentry tachycardia is at home, the atrioventricular node is the most resistant. The atrial rate is about 200 beats/min, so when the ventricular rate is >200 beats/min, there should be a suspected bypass. When >240 beats/min, the probability is greater, so the ventricular rate is >200 times/ Min, after the P wave is after the QRS wave, when the I lead P_ wave is inverted, it should be considered as the atrioventricular reentry tachycardia.

3. The characteristics of atrial flutter with atrial flutter are:

1 atrial rate of 220 ~ 350 times / min;

2 The origin of agitation is common in the atrial tail, and the order of activation is often transmitted from the tail to the head;

3 equipotentials disappear;

4 stimulation of the vagus nerve is not effective for atrial flutter;

5 more common in the elderly;

More than 6 have organic heart disease;

7 ventricular rate is relatively slow.

4. Identification with autonomous atrial tachycardia: If the ECG at the beginning and end of the IART episode is not recorded, it is difficult to distinguish it from autonomous atrial tachycardia (AAT). The two main identification points It is the pre-atrial contraction that can induce and terminate IART and has no effect on AAT. It can be recorded for a long time with dynamic electrocardiogram. If the start and end of contracted paroxysmal atrial tachycardia before expiration can be recorded, it can be determined as IART.

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