Ectopic tachycardia

Introduction Ectopic tachycardia is a rapid and basic regular ectopic rhythm of short or continuous episodes. Its seizures and terminations are mostly sudden, and in the past it was called paroxysmaltachycardia. The heart rate at the time of onset is generally 160 to 220 beats/min, but it is also as slow as 130 beats/min or as fast as 300 beats/min. Each episode can last less than 1 second or last for a few seconds, minutes, hours, or even days, automatically or after treatment. Some may have recurrent episodes, and the interval between the episodes varies.

Cause

Supraventricular tachycardia is more common in patients with no structural heart disease, such as more common atrioventricular nodal reentry tachycardia and atrio-ventricular reciprocating tachycardia (atrio-ventricular reciprocatingtachycardia); also seen in organic Heart disease, such as valvular disease, high heart disease, coronary heart disease, pulmonary heart disease, cardiomyopathy, etc. caused by abnormal atrial load and/or atrial tachycardia caused by lesions; also seen in hyperthyroidism and drug toxicity, accompanied by Paroxysmalatrialtachycardiawith block with atrioventricular block is one of the typical arrhythmias with digitalis toxicity and hypokalemia.

The majority of ventricular tachycardia are seen in patients with extensive and severe myocardial disease, especially myocardial lesions, such as coronary heart disease with acute myocardial infarction or post-infarction cardiac insufficiency or ventricular aneurysm, dilated cardiomyopathy, Right ventricular myocardial dysplasia, severe myocarditis, etc.; a small number of patients with no known structural heart disease, such as primary QT interval prolongation syndrome, mitral valve prolapse. Digitalis toxicity, sympathomimetic overdose, and antiarrhythmic drugs leading to secondary QT prolongation, tricyclic antidepressants, expectorants, and chloroquine, as well as hypokalemia or hypomagnesemia can also be caused. A small number of patients have no evidence of organic heart disease and the cause is unknown.

In addition, hypothermic anesthesia, cardiopulmonary surgery, or mechanical stimulation of the cardiac catheter can also cause various ectopic tachycardias.

The tachycardia originating from the upper part of the branch of the Hessian bundle is collectively referred to as supraventricular tachycardia. The electrocardiogram QRS wave is mostly not widened at the time of onset; and the tachycardia originating from the lower part of the branch of the Hessian bundle is called ventricular tachycardia. Overspeed, the electrocardiogram QRS wave is mostly deformed and widened at the time of onset. However, clinical electrophysiological studies have confirmed that a few QRS-widened tachycardias are supraventricular, while few patients with ventricular tachycardia do not broaden QRS, so the differential diagnosis of supraventricular and ventricular tachycardia is sometimes difficult to determine. Therefore, it is also known as wide QRS tachycardia and narrow QRS tachycardia. Supraventricular tachycardia is much more common than ventricular.

The results of a large number of studies on ectopic tachycardia in the past 20 years have deepened the understanding of its mechanism and electrocardiogram performance, and promoted the classification, diagnosis and treatment update.

an examination

Related inspection

Dynamic electrocardiogram (Holter monitoring) Ultrasound examination of the thyroid gland and parathyroid glands

ECG features:

(1) The supraventricular tachycardia is equivalent to a series of atrial or premature beats of three or more consecutive times. The frequency is mostly 160-220 times/min, with an average of 200 beats/min, and the rhythm rules. Most QRS complexes do not widen the deformity, maintain sinus rhythm morphology, ST segment depression and T wave inversion are common. A small number of QRS time prolonged, more common in the right bundle branch block, and even left bundle branch block. If the QRS morphology is consistent with the sinus rhythm, it still meets the diagnosis of supraventricular tachycardia; the inconsistent QRS with sinus rhythm suggests frequency-dependent intraventricular conduction changes. P wave may not be recognized when tachycardia occurs; when P wave is seen, its frequency increases, the morphology is different from that of sinus rhythm; when combined with II degree atrioventricular block, the ventricular rate may not increase, and the ventricular rhythm may be irregular; When combined with partial or complete retrograde block, the ventricular rate can be significantly higher than the atrial rate.

(2) Ventricular tachycardia is equivalent to three or more consecutive ventricular premature beats, QRS complex is widened (more than 0.12 s), ventricular rate is mostly 150-200 beats/min, rhythm can be slightly irregular, occasionally The RR spacing differs by 0.33s. Sinus rhythm can continue to exist independently, forming compartmental separation; sinus P wave is sometimes difficult to identify on the surface ECG lead, but the esophageal lead or right atrium ECG can often show sinus P wave, the frequency is more than the ventricle The rate is slow. The P-wave couple may be transmitted down to form an early QRS complex (ventricular occlusion) with the same or slightly different morphology as the sinus rhythm (combined frequency-dependent indoor differential conduction changes). Sometimes the sinus P wave partially captures the ventricle, and together with the ventricular ectopic beat, forms a ventricular fusion wave, which is between the sinus rhythm and the QRS complex of ventricular tachycardia.

After the QRS complex, there is occasional retrograde P wave, which is the ventricular ectopic pacing point after the ventricle is reversed to the atria and controls the performance of the whole heart activity.

Suspension of tachycardia for 30 s or more, also known as continuous ventricular tachycardia. A tachycardia that automatically terminates in less than 30 seconds, also known as non-sustained ventricular tachycardia. In the case of tachycardia, the QRS complex is consistent or variable, and can be called single-shaped and polymorphic ventricular tachycardia, respectively. Torsades ventricular tachycardia (also known as ventricular fibrillation ventricular tachycardia) is a special type of non-sustained polymorphic ventricular tachycardia. The tachycardia intermittent recurrent episodes, the frequency is 200-250 times/min or more, and the QRS complex changes obviously. The main wave direction is upward and sometimes downward. The onset of T-wave or U-wave from the previous heartbeat can also develop into a faster, longer-lasting ventricular tachycardia, or even evolve into ventricular fibrillation. Common in primary or secondary QT prolongation syndrome, the latter occurs in hypokalemia, hypomagnesemia and antiarrhythmic drugs (such as quinidine, amiodarone, propiamine, etc.), chloroquine When it is used, such as expectorant, diclofenac and tricyclic antidepressant, it also occurs in severe bradycardia.

In the case of bidirectional ventricular tachycardia, the main wave direction of the QRS complex of the same lead in the electrocardiogram is alternated upward and downward. Most occur in digitalis poisoning or hypokalemia, occasionally seen in people without structural heart disease.

Differential diagnosis

Differential diagnosis:

(1) Sinus tachycardia: Sinus tachycardia with a heart rate between 140 and 160 beats/min is more difficult to distinguish from supraventricular tachycardia. Sudden onset of seizure history, fixed heart rate and absolute rule of heart rhythm, excitement of the vagus nerve can stop the episode, the possibility of supraventricular tachycardia is large. Most of the sinus tachycardia gradually increased or gradually slowed down, and the heart rate often changed. The excited vagus nerve could not stop the attack.

When atrial tachycardia with 2:1 atrioventricular block, the ventricular rate is more than 100 times / min, half of the P wave in the ECG can be buried in the QRS complex, and is often misdiagnosed as sinus tachycardia. Differential diagnosis should pay attention to find the frequency of P wave and its relationship with QRS complex in the ECG show P-wave clear lead.

(B) atrial flutter: most of the atrial flutter with 2:1 atrioventricular conduction, ventricular rate of 140 ~ 160 times / min. Atrial activity appears as a regular zigzag flutter on the ECG and can be misdiagnosed as supraventricular tachycardia. Excited vagus nerve can halve or slow the ventricular rate, and the ECG shows a clear zigzag atrial flutter wave that helps to confirm the diagnosis. The atrial rate of a few atrial tachycardia can be as fast as 300 times / min, close to the atrial flutter, accompanied by 2:1 atrioventricular conduction, it is more difficult to identify with atrial flutter.

(3) Non-paroxysmal tachycardia.

(D) the differential diagnosis of supraventricular and ventricular tachycardia is generally based on ECG QRS complex malformation, with or without sinus P wave or atrioventricular separation, ventricular capture or ventricular fusion pulsation, combined with heart rhythm Whether it is absolute rules, whether the vagus nerve can make the attack stop, and the degree of blood flow disorder at the time of attack is not difficult to identify. QRS complex broadened supraventricular tachycardia (superior tachycardia with differential intraventricular conduction or bundle branch block or pre-excitation), QRS complex normal ventricular tachycardia (originating from Ventricular septum or ventricular ventricular tachycardia at the proximal end of the bundle can make the differential diagnosis difficult, often requiring the diagnosis of the Greek electrocardiogram. The tachycardia was initiated by ventricular premature beats. The QRS time limit was extended by more than 0.14 seconds. The frontal surface QRS was axially axial, with compartmental separation, ventricular capture and ventricular fusion, and the QRS wave pattern of the lead in the anterior region was similar. The prompt is ventricular tachycardia. Hessian beam electrogram HV abnormality (H is not seen, H and V are separated or H is before V and HV interval is significantly shorter than normal), and ventricular late potential is positive, can be diagnosed as ventricular tachycardia.

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