Atrial contraction

Introduction to atrial premature contraction Atrial premature beats (APB), also known as atrial premature beats (APB), also known as atrial premature beats, early atrial contraction, atrial premature contraction, originated from any part of the atrial sinus outside the atrium. Normal adults underwent 24-hour ECG testing, and approximately 60% had atrial premature contractions. Atrial premature contractions can occur in a variety of patients with structural heart disease and are often a precursor to rapid atrial arrhythmias. basic knowledge The proportion of the disease: the incidence rate of the elderly over 50 years old is about 0.01%-0.05% Susceptible people: no special people Mode of infection: non-infectious Complications: atrial fibrillation

Pre-atrial contraction etiology

(1) Causes of the disease

Organic heart disease (35%):

Any organic heart disease can occur, more common in coronary heart disease, rheumatic heart disease, pulmonary heart disease (especially multi-source atrial premature contraction), myocarditis, cardiomyopathy, hypertensive heart disease, heart failure, acute Myocardial infarction, mitral valve prolapse, etc.

Drug factors (18%):

The application of digitalis, quinidine, procainamide, adrenaline, isoproterenol, tincture and various anesthetics can cause premature atrial contraction, in the case of acid-base balance disorders, electrolyte imbalance, such as Hypokalemia, hypocalcemia, hypomagnesemia, acid-base poisoning, etc. may also occur before atrial contraction.

Other factors (12%):

There is no obvious incentive for premature atrial contraction, but with mental stress, emotional agitation, sudden increase in blood pressure, fatigue, excessive drinking, smoking, drinking tea, drinking coffee, full meal, constipation, bloating, indigestion, insomnia A sudden change in body position and other factors, the premature atrial contraction caused by this cause is more likely to appear before or at rest, after the exercise or heart rate increase or decrease, or due to direct mechanical stimulation of the heart ( Such as cardiac surgery or cardiac catheterization, etc. caused by atrial premature contraction.

1. Endocrine diseases: hyperthyroidism, adrenal diseases, etc.

2. Normal healthy heart: Atrial premature contraction can occur in normal people of all age groups, children are rare, middle-aged and elderly people are more common, may be caused by autonomic dysfunction, sympathetic or vagus nerve hyperthyroidism can cause Contraction before the period.

(two) pathogenesis

The mechanism of atrial premature contraction is the most common arrhythmia of atrial tissue, followed by reentry excitability, and the least common cause of depolarization after triggering.

1. Abnormal increase in atrial tissue: Many parts of the atrium other than the sinus node, especially the room bundle, can produce atrial ectopic agitation. Under normal circumstances, the sinus node is the highest rhythm point of the heart, and the sinus node is centrifuged. The room is very close, so the agitation of each sinus node can depolarize the atrial self-regulatory cells, and at the same time inhibit the self-discipline of atrial autonomic cells. When the local atrial tissue is ischemic, damaged, repolarization inconsistent and intraventricular pressure When the height is increased, a local current may be generated due to a potential difference between adjacent tissues of the atrium, so that the atrial cells are partially depolarized, thereby reaching a threshold potential and causing atrial premature contraction.

2. Atrial reentry agonism: There are anterior, middle and posterior internodes in the atrium, which can form a reentry pathway. In addition, there are many anatomical and functional reentry pathways. When a sinus rhythm is excited, the atrium is as long as it meets 3 conditions for reentry:

1 There must be an anatomical or functional loop, the loop including the excited cis-transfer and the excited retrograde branch;

One of the two loops has a one-way conduction block, that is, a forward conduction block, and a reverse conduction block;

3 Appropriate conduction slowdown, that is, when the reversal of the loop reversal reaches the cis branch, it is necessary to make the shun branch again excited, so it can not be transmitted too fast, then you can re-excite the atrium through the atrial reentry, and generate a pre-atrial period. Shrink and pass down to the ventricle.

3. Triggering agitation: In the animal experiment, a slow depolarization wave appears after a spontaneously excited action potential. When this wave reaches the threshold, another action potential can be triggered, called the post potential, which occurs after this depolarization. The action potential is called triggering agitation. When the post-potential reaches the threshold, it triggers a triggering agitation (ie, pre-systolic contraction), or it can be repeated multiple times to form a tachycardia.

Recently, it has been found that part of the atrial premature contraction originates from the muscle sleeve tissue (refers to the myocardial tissue wound around the pulmonary vein or the vena cava wall).

Atrial premature contraction prevention

The appearance of atrial premature contraction must first be determined whether it is physiological or pathological.

Such as pathological conditions, especially organic disease, such as hyperthyroidism, atrial premature contraction caused by hypoxia caused by lung disease, digitalis poisoning, electrolyte imbalance, etc., should actively treat the primary disease, the device For patients with quality heart disease, the treatment should be directed at heart disease itself, such as coronary heart disease should improve coronary blood supply, rheumatism anti-rheumatic treatment, heart failure treatment, etc., when the heart condition is improved or cured, the atrial premature contraction often Can be reduced or disappeared.

Atrial contraction complications Complications, atrial fibrillation

Frequent and persistent atrial premature contractions, especially when the multi-source or paired atrial premature contraction index is <0.5, can often cause atrial fibrillation or atrial tachycardia.

Atrial premature contraction symptoms common symptoms palpitations, chest distress, dizziness

Mainly manifested as palpitations, heart "stop" feeling, when the number of pre-contraction times is too much, consciously "heartbeat is very chaotic", may have chest tightness, pre-cardiac discomfort, dizziness, fatigue, intermittent pulse, etc., also have asymptomatic, It may be that the contraction lasts for a long time, and the patient has adapted. In addition, the symptoms of pre-contraction are closely related to the mental state of the patient. Many of the symptoms of many patients are due to incorrect understanding and fear of pre-contraction, anxiety. Caused by emotions.

Examination of premature contraction

Mainly by ECG diagnosis, ECG performance can have the following performance:

1. Characteristics of typical atrial premature contraction ECG

(1) Shaped P' wave appearing in advance: The P' wave shape is different from the sinus P wave. The P' wave is usually not retrograde, but if it originates from the lower part of the atrium, its P' wave may be retrograde.

(2) The P'-R interval is greater than 0.12 s.

(3) The morphology of the QRS complex, the time limit is the same as the basic sinus rhythm.

(4) There is an incomplete compensation interval.

2. Description of typical ECG characteristics of pre-atrial contraction

(1) P' wave: The P' wave of premature contraction appears in advance, which can overlap with the T wave of the previous sinus beat, and the T wave can make the T wave blunt, the notch or the amplitude increase, and decrease And various deformations, if earlier, the P' wave can overlap on the ST segment, or the R wave falls to the S wave region, while the ST segment, the T wave, the R wave drop branch to the S wave region are all Atrial fibrillation period, easy to cause atrial fibrillation, P' wave can be high-pointed, flat, bidirectional or inverted, P' wave shape can be two or more in the same lead, called multi-source room Contraction before sexual sex.

(2) P'-R interval: the P'-R interval of atrial contraction is greater than 0.12 s, and its length depends on the degree of premature contraction and the conduction function of the atrioventricular junction. In the late atrial contraction, the P' wave occurs at the peak of the T wave to the end of the T wave. Because the atrioventricular junction area and the ventricle are in the relative refractory period, the P'-R interval is prone to prolonged, often exceeding 0.20 s, and often there is indoor differential conduction, atrial premature contraction occurs in early diastolic, P' wave occurs at the end of T wave to the end of u wave, in addition, occasionally P'-R interval extension and (or Indoor differential conduction, usually in the case of normal atrioventricular conduction function, early diastolic, mid-diastolic atrial premature contraction, P'-R interval is 0.12 ~ 0.20s, pre-systolic atrial contraction That is, the premature atrial contraction occurs between the J point and the T wave peak. Since the atrioventricular junction area is in an absolute refractory period, it cannot be transmitted, but the minority atrial premature contraction falls in the first supernormal period, ie, the ST segment. In the middle of the section and accidentally underground, it is called super-period conduction; if it does not fall in the middle of the ST segment, it is located in the middle of the contraction The other parts of the time are also transmitted in the supernormal period, that is, the void phenomenon. If the premature contraction occurs earlier, because the atrioventricular junction area is in the absolute refractory period, the P' wave is not blocked due to the block. QRS wave, which is a pre-atrial contraction that has not been transmitted (or blocked).

(3) QRS-T wave: It is usually normal. In the following cases, a QRS wave with a large deformity may appear after atrial contraction:

1 with indoor differential conduction;

2 accompanied by pre-excitation syndrome;

3 accompanied by bundle branch block.

(4) Intermittent compensation: usually for incomplete compensation, there are three types of performance:

1 In a few cases, there is a complete compensatory interval, which is due to the late atrial contraction, and the P' wave falls in the first 20% of the sinus cycle. At this time, the sinus node impulse has begun to be released, and the two are connected in the sinus. Interference occurred, but the next sinus impulse was still issued on time, so a complete compensatory interval was formed;

2 atrial premature contraction was inserted, that is, an atrial premature contraction was inserted between the two sinus beats, without compensatory interval (PP'+P'-P=PP);

3 premature contraction occurs prematurely, P' wave falls in the 15% to 17% of the beginning of the sinus cycle, can be introduced into the sinus node to cause sinus echo, which appears on the electrocardiogram as atrial premature contraction There is an sinus P wave that appears in advance.

9 types of compensation intermittent comparison and measurement:

X: 1 basic cardiac circumference (BCL).

Y: Inter-law interval (pairing interval).

Z': Compensatory interval.

P1, P2, P3...: is the basic heart beat.

Z: Intermittent compensation for delay (ie R3-R4, slightly longer than BCL).

1 Non-compensated interval: that is, the insertion (meta) pre-contraction, the pre-expansion contraction interval (Y) + compensatory interval (Z) = BCL, which reflects that the basic rhythm point does not occur rhythm reforming The premature contraction encounters a basic heart rhythm during conduction and an interfering conduction interruption or reentry occurs.

Two equal-cycle compensatory pauses: The compensatory interval is between 1 and 3, ie >BCL, <2BCL, which is more common in the pre-invasive contraction with basic cardiac rhythm-induced conduction delay.

3 cycles of compensatory interval: ie (Z) = BCL, the sinus pre-contraction is such.

4 Incomplete compensatory interval: Compensatory interval (Z)>BCL, but Y+Z<2BCL, which is a sign that the rhythm is delayed due to rhythm reforming under the influence of pre-systolic contraction (or S2). SACT (sinus conduction time) is the use of this principle.

5 complete compensatory interval: (Y) + (Z) = 2 BCL, it is the performance of the basic heart rhythm is not affected by pre-contraction, the original intention is that the time of this compensation interval is fully compensated (or compensated) has been shortened The inter-law period.

6 super complete compensatory interval: Y + Z > 2BCL, mainly due to pre-contraction (or S2) directly inhibited the pace of the basic heart rhythm.

7 super-complete compensatory interval: compensatory intermittent (Z) 2 BCL, which is the basic function of the basic rhythm pacemaker, so the pacing function is inhibited by the effect of overspeed inhibition, such as sick sinus node synthesis Sign.

8 Delayed compensatory interval: The compensatory interval after pre-systolic contraction is the same as 4, which is the incomplete compensatory interval, but the second cardiac cycle after the pre-systolic contraction (R3-R4 interval = Z') is prolonged. More than one sinus circumference (Y), so Y + Z + Z 3 BCL, secondary arrest is also in this category.

Class 9 compensatory interval: seen in atrial fibrillation with ventricular premature contraction, irregular ventricular rhythm, but different degrees of compensatory interval can still be seen after pre-contraction.

It should be noted that the measurement of P1-P3 is performed when the basic heart rhythm is sinus or atrial, and the R1-R3 interval is determined if the basic heart rhythm is the junctional or ventricular.

(5) Inter-rational interval: The inter-trial contraction of the atrial premature contraction is issued by the same ectopic excitatory, and should be fixed in the same patient.

(6) Conduction: The excitement from pre-atrial contraction can be transmitted upward (ie, reverse) or downward (ie, forward).

1 Forward conduction: There are 3 kinds of performances:

A. Pre-atrial contraction is normal through the junctional zone: the P'-R interval is normal.

B. Early atrial premature contraction, because part of the tissue in the junction area is still in refractory period, the conduction time is prolonged, and the P'-R interval is greater than 0.20s.

C. Earlier premature atrial contraction: Since the junction area tissue is in complete refractory period, the atrial premature contraction cannot be transmitted downwards. Only the advanced P' wave is seen on the electrocardiogram, and there is no ORS-T wave thereafter. For the premature contraction of the prenatal period.

2 Reverse conduction: There are 4 types of performance:

A. Atrial premature systolic reversal in advance sinus atrial sinus node: sinus node from this new starting point to issue sinus rhythm, manifested as incomplete compensatory interval.

B. Atrial premature contraction is issued at the end of diastole: almost coincides with sinus agitation, and the interference between the two in the sinus junction does not affect the sinus rhythm change, which is a complete compensatory interval.

C. Atrial premature contraction and sinus sensation excitement in the atrium: Since both have excited a part of the atrium, atrial fusion waves are formed.

D. The earlier premature atrial contraction is reversed to the sinus node: but it is in the refractory period, so it does not affect the production and conduction of the next normal sinus rhythm. This atrial premature contraction is just two Between sinus beats, this is called insertional (metamorphic) atrial contraction.

3 occult conduction: atrial contraction before delivery, although the ventricle is not depolarized, but there is occult conduction in the atrioventricular junction, which can prolong the PR interval of the next sinus beat.

3. Special types of pre-trial contraction

(1) multi-source atrial premature contraction: pleomorphic atrial pre-contraction refers to two or more ectopic pacemakers in the atria, and the electrocardiogram shows a pre-atrial contraction. The period of the P' wave is not exactly the same. The polymorphic atrial premature contraction refers to the equal interval between the atrial premature contractions, and the P' wave shape is diversified.

(2) pre-atrial contraction is a joint law: pre-atrial contraction can form a two-law, that is, a sinus beat with a pre-atrial contraction, three consecutive groups, can also form a three-law, 2 One sinus beat with one atrial contraction; or one sinus beat with two atrial premature contractions, three consecutive groups; can also form four-law, five-law.

(3) pre-atrial contraction and continuous firing: two or more atrial premature contractions occur continuously, such as the occurrence of three or more consecutive atrial premature contractions called atrial tachycardia.

(4) Metabolic atrial premature contraction: between two sinus P waves in one sinus cardiac cycle, one atrial premature contraction, no compensatory interval, due to atrial contraction The ectopic agitation is easy to disturb the self-discipline of the sinus node, so the insertional atrial premature contraction is rare, and there must be some protective mechanism that prevents the sinus node from being interfered by ectopic activation. Insertive atrial contraction.

(5) pre-atrial contraction is not transmitted: RP interval is 0.100.20s, the atrial premature contraction can not be transmitted, but the longer RP interval can not be atrial premature contraction. In the case of the lower case, the atrial premature contraction is not seen in the mid-systolic phase. It is the atrial premature contraction that occurs before the T wave crest. The non-inferiority caused by this period is a physiological phenomenon, but if it is diastolic Early or diastolic atrial premature contraction does not pass down, it is a pathological phenomenon, known as blocked atrial premature contraction, or atrial premature contraction with blockade, because this The atrioventricular junction area is in the reaction period. If it cannot be transmitted, it indicates that pathological blockage has occurred. This situation can be manifested in two ways:

1 On the same electrocardiogram, the sinus P wave and the early or late diastolic atrial premature contraction can not be transmitted in whole or in part, which is called dominant second or third degree atrioventricular block;

2 On the same electrocardiogram, only the P' wave of the atrial contraction is leaky, which is called recessive second or third degree atrioventricular block.

(6) Atrial premature contraction with indoor differential conduction: its ECG features:

1 P' wave appearing in advance, sometimes the P' wave overlaps with the T wave of the previous heart beat, resulting in T wave deformation;

Most of the 2QRS clusters have a right bundle branch block pattern (about 80%). The QRS is widened or not widened, and it can also be left bundle branch block type, left anterior branch block type or left posterior branch block type. The latter two QRS waves are not widened, and the same patient can present multiple types of indoor differential conduction:

3 There is an incomplete compensation compensation interval.

The reason for premature atrial contraction with differential conduction in the room is that the atrial premature contraction occurs earlier, and the physiological refractory period of the part of the conduction system in the ventricle is encountered in the forward conduction, which can only be slower or Other parts that have left the refractory period are transmitted to the ventricle, resulting in inconsistencies in the conduction pathways, causing changes in the ventricular depolarization and repolarization sequences. The QRS wave is broadly deformed and can be bundled or branched in various degrees and in various forms. Block the graph.

The conditions for indoor differential conduction are:

1 premature contraction occurs earlier, so it is also called phase-variant indoor differential conduction;

2 heart rate is faster;

3 The excitability that occurs after a long interval has a longer refractory period, and the subsequent early agitation (such as atrial premature contraction) is prone to differential conduction, which is called the Ashman phenomenon.

(7) There are mainly the following types of occult atrial premature contractions:

1 concealed atrial bigeminy: on continuous electrocardiogram, when the number of sinus beats between dominant atrial premature contractions was observed, the total amount was 1, 3, 5, 7,9,11... and other odd numbers, in accordance with the law of the formula 2n-1 (n is any positive integer), can be diagnosed as occult atrial premature contraction.

2 even number variant of concealed atrial bigeminy: on continuous electrocardiogram, when two adjacent non-inserted dominant atrial premature contractions are seen The number of sinus beats is always an even number 2, 4, 6, 8, 10... in accordance with the law of formula 2n, this phenomenon of evolution from the typical occult binary law (odd number) to even number, called even-variant occult housing Sexual contraction before the contraction.

3 concealed atrial trigeminy: On the continuous electrocardiogram, when the two dominant atrial premature contractions are seen, the number of sinus beats alternates between odd and even numbers, ie 2 , 5,8,11,14... According to the law of formula 3n-l, it can be diagnosed as occult atrial contraction.

4 concealed atrial quadrigeminy: on the continuous electrocardiogram, when the number of sinus beats between the two dominant atrial premature contractions is odd, it is 3,7 , 11, 15, 19, 23 ... in accordance with the law of the formula 4n-1, can be diagnosed as occult atrial premature contraction quadruple.

(8) Pre-excitation atrial premature contraction: When the atrial ectopic agitation suddenly passes through the Kent bundle to transmit the ventricular tachycardia, a pre-excitation pattern can be generated, so it is called pre-excited atrial premature contraction.

(9) Characteristics of atrial premature contraction occurring in bundle branch block: the atrial premature contraction occurs in the bundle branch block, and the QRS wave is also widened, deformed, but the QRS wave transmitted under the dominant heart rhythm Morphology, time limit is completely consistent, and there is an atrial P' wave in front of it. If the basic heart rhythm is bundle branch block and then atrial premature contraction with indoor differential conduction, the QRS wave is more wide and deformed, but if the room Pre-sexual contraction with indoor differential conduction, when the two sides of the depolarization vector cancel each other, the QRS wave can be wide, the degree of deformity is reduced, the pre-systolic contraction waveform is mildly normalized, and the pre-expansion atrial premature contraction is more likely to occur. .

(10) Atrial premature contraction induces atrial tachycardia, atrial flutter, atrial fibrillation: premature atrial contraction occurs prematurely in the atrial fibrillation period (near S wave), which can induce a variety of rapid Atrial arrhythmia, atrial premature contraction of the interval between 0.20 ~ 0.30s, easy to induce atrial tachycardia, atrial flutter, atrial fibrillation, in addition to atrial premature contraction occult conduction can stimulate the atrioventricular Handover zone tachycardia.

(11) Atrial premature contraction-induced ventricular tachycardia, induced torsades de pointes ventricular tachycardia: is very rare, may be due to the ventricular myocardium due to atrial premature contraction caused by the extremely uneven, It will aggravate the existing ventricular myoelectric activity in an unstable state, repolarization heterogeneity, etc., which is conducive to the formation of reentry agonism, more common in patients with coronary heart disease and other organic heart disease, it should be alert to these patients when only the room Ventricular tachycardia may also be induced when premature contractions occur.

(12) Atrial premature systolic atrial echo pulsation: Atrial premature systolic atrial echo pulsation is transmitted to the ventricle for early atrial agitation, producing a normal QRS complex, and then exciting another pathway from the junction area. Uploading the atrium, generating a retrograde P wave, the route of retrograde transmission may have two compartments in the atrioventricular node and the bypass. In general, when the atrial echo is atrial echo, the PR interval is extended by more than 0.23s. If it is less than this, the possibility of bypass reentry should be considered.

(13) Atrial premature contraction reveals an increase in right bundle branch block: The rate block is a 3-phase block that occurs when the heart rate increases, and the refractory period of the block is abnormally prolonged. For example, be careful. When the rate was 79 beats/min, QRS showed right bundle branch block. When the compensatory interval of pre-atrial contraction extended the RR interval to the equivalent of 62 beats/min, the right bundle branch block disappeared. The compensatory interval caused by anterior contraction is easily misdiagnosed as a persistent right bundle branch block.

(14) Atrial premature contraction can cause differential conduction in the room: one or several sinus P waves can be morphologically changed after atrial contraction, which is different from atrial P' wave or sinus P Wave, caused by differential conduction in the room.

(15) Variant "fast-slow syndrome" caused by contraction before atrial contraction.

(16) Muscle sleeve atrial premature contraction: a single or continuous number of electrical stimuli originating from the muscle sleeve tissue to the atria cause a single or paired premature activation of the atrium. The main features of the electrocardiogram are:

1 The inter-law interval is short, mostly in the range of 200 to 400 ms, so it is also called P-on-T atrial premature contraction. Due to the short inter-term interval, it is prone to P'-R interval prolongation, indoor differential conduction. And P' waves cannot be transmitted;

2 frequent attacks, a large number, electrocardiogram or 24h dynamic electrocardiogram on the frequent short-term intertemporal atrial contraction, can be two or three, the total number of pre-atrial contractions can reach thousands to tens of thousands every 24 hours One

3 easy to coexist with other muscle sleeve arrhythmia, such as atrial premature contraction with short-term atrial tachycardia and short-term atrial fibrillation.

Diagnosis of atrial premature contraction

diagnosis

It is usually difficult to determine the diagnosis based on the patient's clinical manifestations, physical signs and ECG characteristics.

Differential diagnosis

1. The pre-atrial contraction and the atrioventricular junction area pre-contraction are identified. The P' wave is erect, the latter's P' wave is retrograde, and the atrial pre-contraction P' wave in the lower atrium can be retrograde. However, the P'-R interval is 0.12 s, and the P'-R interval is <0.12 s before contraction.

2. Identification of non-transfer atrial premature contraction and 2:1 atrioventricular block. When the P' wave of the pre-atrial contraction does not overlap with the ST or T wave of the previous heartbeat It is easily misdiagnosed as 2:1 atrioventricular block, but the P' wave shape of atrial premature contraction is different from that of sinus P wave; 2:1 block can be aggravated after exercise, and atrial contraction can disappear before If there is a prolongation of the PR interval on the current and current ECG, it is suggested to be a 2:1 atrioventricular block.

3. The differentiation of atrial premature contraction with indoor differential conduction and ventricular premature contraction can be identified according to the difference of QRS waves between the two.

(1) Those who exhibit three-phase waveforms (rsR', rsR', rsr') in the V1 lead: mostly indoor differential conduction (70%); 30% indoor differential conduction and 92% ventricular pre-existence The contraction is a single phase wave (R wave) or a biphasic wave (qR, RS or QR wave).

(2) The starting vector (initial vector) of the V1 lead QRS wave: 44% of indoor differential conduction is the same as normal, while only 4% of ventricular premature contraction is the same as normal, and several indoor differences in the same lead Conducted QRS wave start vector, some are consistent with normal, some are inconsistent, and this kind of initial vector change is also one of the characteristics of indoor differential conduction.

(3) In the case of differential conduction in the room, the degree of conduction of the ventricular depolarization is different, so the shape of the QRS wave also changes, that is, several malformed QRS waves can be presented on the same lead, and the room The QRS wave morphology of pre-sex contraction was consistent (polymorphism, except for multi-source ventricular premature contractions).

(4) The length of the cardiac cycle before the inter-trial period: the length of the heartbeat refractory period is proportional to the length of the previous cardiac cycle. When the cardiac cycle is long, the refractory period of the subsequent heartbeat will be long. It is prone to indoor differential conduction, that is, the longer the cardiac cycle before the inter-term interval, the more obvious the difference in indoor conduction, but some ventricular premature contractions are also due to the two-law rule after a long cardiac cycle. occur.

(5) The shorter the interval between the two departments, the more obvious the degree of differential conduction in the room, and the interval between the pre-ventricular contractions is fixed; while the indoor differential conduction is mostly not fixed, and a few can be fixed.

(6) The pre-atrial contraction with indoor differential conduction P'-R interval is prolonged or not prolonged, and the prolongation of P'-R interval often reduces the premature degree of QRS-T wave. When the time is prolonged, the degree of differential conduction tends to be alleviated. In addition, the atrial premature contraction with indoor differential conduction (in the right bundle) can prolong the PR interval in which the incomplete three-block block is prolonged.

4. Pre-atrial contraction and sinus pre-systolic differentiation The sinus pre-contraction morphology is the same as the sinus rhythm P wave, while the atrial pre-contraction P' wave is slightly different from the sinus rhythm P wave. If the atrial premature contraction originates near the sinus node, the two are not easily distinguished.

5. The atrial premature contraction dichotomy and the second degree I sinus block showed a 3:2 conduction differential. Both of them showed a long and short P-QRS-T wave group, so the identification was difficult, but two The P-wave morphology is significantly different, and it supports the diagnosis of atrial premature contraction. If the P-wave morphology is not significantly different, then the second-degree I type is 3:2 sinus block, and the sinus node can confirm the diagnosis. .

6. The difference between atrial premature contraction and sinus arrest may result in a long PP interval shorter than 2 sinus beats. At this time, the T wave overlapping the previous heart beat should be carefully searched. The P' wave can cause the T wave to be misfolded, and the T wave, which is different from other basic heart rhythms, is usually not difficult to identify.

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