idiopathic ventricular tachycardia
Introduction
Introduction to idiopathic ventricular tachycardia Idiopathic ventricular tachycardia (IVT) was first reported by Gallavard in 1922. It occurs in patients who are not based on organic heart disease and is examined as a group of monomorphic ventricular tachycardia with no apparent cardiac structural and functional abnormalities. basic knowledge Sickness ratio: 0.0001% Susceptible people: no specific population Mode of infection: non-infectious Complications: dizziness, syncope
Cause
Idiopathic ventricular tachycardia
(1) Causes of the disease
The exact cause is unclear. Recently, there have been reports of suspected genetic mutations leading to sodium channel disorders. It has been reported that 8% to 30% of patients with idiopathic ventricular tachycardia have focal myocardial lesions and subclinical myocarditis. However, the lesions were small and very light, and no progress was observed during follow-up. There were also reports of myocardial biopsy. The autopsy of the myocardium was normal. It was considered that even if the patient had mild cardiac function and structural abnormalities, it is difficult to confirm that there was a difference between the two. A clear causal relationship, individual patients have sudden death, and some individuals have developed into cardiomyopathy during the follow-up. This disease can be familial.
(two) pathogenesis
Left bundle branch block type idiopathic ventricular tachycardia
The vast majority originated from the right ventricular outflow tract, and a few originated from the right ventricular inflow tract, apical part, right ventricular septum, etc. It has been confirmed to be triggered by activity, and can be terminated by adenosine, also known as catecholamine. Sensitive ventricular tachycardia, adenosine-sensitive ventricular tachycardia, exercise-induced ventricular tachycardia, electrophysiological characteristics are less induced by ventricular electrical stimulation, only 20% to 30% of patients can Induced, most of which were induced by intravenous infusion of isoproterenol, ventricular tachycardia induced by programmed ventricular stimulation did not evolve into ventricular fibrillation, and non-sustained ventricular tachycardia was 15% to 25 during electrical stimulation. % of patients can induce persistent ventricular tachycardia, and ventricular late potential is mostly negative.
Right bundle branch block type idiopathic ventricular tachycardia
Its mechanism is mainly caused by micro-reentry agonism. Its reentry ring is composed of Purkinje fiber and local myocardium, which is easily blocked by verapamil. A few patients are triggered by delayed depolarization. Due to activity, it is characterized by endless seizures, and can be terminated by adenosine, beta blockers, and some patients sensitive to verapamil can also be terminated by adenosine, suggesting that it may be adenosine Guided trigger activity, clinically less patients with ventricular premature contraction or non-sustained ventricular tachycardia, electrophysiological characteristics of ventricular program electrical stimulation about 75% of patients can be induced; pre-procedural stimulation + different The induction rate of propofol infusion is up to 90%, and the induced persistent ventricular tachycardia does not evolve into ventricular fibrillation. Exercise can induce persistent ventricular tachycardia with an induction rate of 20% to 50%. Compared with left bundle branch block type idiopathic ventricular tachycardia, it is not easy to distinguish between two types of idiopathic ventricular tachycardia from exercise test, and it is not certain what kind of mechanism is involved, intravenous bolus Verapamil treatment works best, but oral verapamil Rice can not prevent the recurrence of this type of ventricular tachycardia.
Prevention
Idiopathic ventricular tachycardia prevention
At present, there is no effective prevention method for idiopathic ventricular tachycardia, and attention should be paid in daily life:
1. Set your mind and avoid mental stress; keep indoors quiet and avoid noise and bad stimuli.
2. Comfort the patient with language to establish the patient's determination and confidence in overcoming the disease.
3. Appropriate diet, keep the stool smooth; live in festivals, beware of exogenous evils, and prohibit alcohol and tobacco.
Complication
Idiopathic ventricular tachycardia complications Complications, dizziness, syncope
When ventricular tachycardia lasts for too long, complications such as dizziness, syncope, and blood pressure drop may occur. Concurrent heart enlargement, heart failure, cardiogenic shock, etc. Cardiogenic shock (cardiovascular medicine) refers to a syndrome in which cardiac output is significantly reduced and severe acute peripheral circulatory failure is caused by extreme cardiac function loss. The cause is most common in acute myocardial infarction, severe myocarditis, cardiomyopathy, pericardial tamponade, severe arrhythmia or chronic heart failure.
Symptom
Idiopathic ventricular tachycardia symptoms common symptoms hemodynamic disorder palpitations blood pressure drop chest tightness tachycardia nausea dizziness dizziness
Most patients with non-sustained ventricular tachycardia are asymptomatic, with a short duration of attack, the longest is 30s, sometimes have palpitations at the time of onset, recurrent episodes, more common in young or middle-aged people, no clinical organic heart disease Most of them have ventricular tachycardia during stress or exercise.
Patients with persistent ventricular tachycardia are also more common in young people, most of whom are 20 to 40 years old (11 to 56 years old), with an average age of 36.9 years, ranging from 4.1 to 5.5 years. No clinical findings have been found. There is a clear basis for organic heart disease. It is asymptomatic when not attacking. When the tachycardia occurs, it lasts for a long time. It often has palpitations, chest tightness, dizziness, nausea, etc. When the ventricular rate is too fast or lasts for a long time. In the elderly, syncope or decreased blood pressure may occur, and the effects on hemodynamics and cardiac function are usually mild, but hemodynamic disorders may occur in individual patients. The frequency of ventricular tachycardia is annual. 4 to 48 episodes, duration of attack is 0.5 to 30 hours, but there is also a longer duration, the frequency of persistent ventricular tachycardia is 115 to 250 beats / min, and the number of women with left bundle branch block is more than that of men. See, and the right bundle branch block type is almost always seen in men.
Examine
Idiopathic ventricular tachycardia
Mainly based on ECG examination.
1. Typical ECG characteristics of idiopathic ventricular tachycardia
(1) LBBB type idiopathic ventricular tachycardia: This type accounts for 70% of idiopathic ventricular tachycardia and is divided into the following two types.
ECG characteristics of 1LBBB non-sustained idiopathic ventricular tachycardia:
A. Repeated episodes of short-form monomorphic ventricular tachycardia: 3 or more consecutive ventricular premature contractions in each episode, most of which persist within 30 s and terminate spontaneously, generally 3 to 20 consecutive Premature ventricular contraction, it is non-sustained ventricular tachycardia.
B. The QRS wave shape of ventricular tachycardia is LBBB type: the first QRS pattern of ventricular tachycardia is the same as the QRS pattern after it, the QRS wave time limit is >0.12s, but the degree of widening is small, to 0.13 ~0.14s is the most common, mostly within 0.16s.
C. Most of the frontal ECG axes are right-biased, and some are normal.
D. Most patients have a ventricular rate of 110-160 beats/min at onset. There is often no awake phenomenon. Most of the ventricular rate is regular and uniform. A few can be irregular. Sometimes the circumference of the ventricular tachycardia is before the termination. It has gradually shortened.
E. Seizures are related to heart rate: when sinus rhythm is fast, it is easy to attack, exercise can be induced, and the stimulation induction rate is low before the procedure. Intravenous infusion of isoproterenol can induce or facilitate pre-procedural stimulation.
F. Approximate judgment of right ventricular origin: II, III, aVF lead, such as R wave, originated from right ventricular outflow tract or free wall, II, III, aVF lead with S wave as the main origin of right Ventricular inflow or apex.
G. Intermittent seizures are often sinus rhythm: there are often single or paired ventricular premature contractions, and the ventricular premature contraction is exactly the same as the QRS wave morphology of ventricular tachycardia.
H. Signal average ECG is normal.
2LBBB type persistent idiopathic ventricular tachycardia:
A. The number of ventricular tachycardia episodes is not frequent: 5 to 40 episodes per year, but each episode lasts for a long time, from 30s to several hours, mostly 0.5 to 24 hours.
B. The QRS wave is LBBB in the onset of ventricular tachycardia: the degree of QRS wave broadening is small, ranging from 0.12 to 0.16 s (Fig. 2). Only the aVL lead has a QS pattern except for the aVR lead.
C. Most of the frontal ECG shafts are about 90° right, or called drooping electric axes, and will not be left.
D. The ventricular rate is 130-250 times/min, with an average of 180 beats/min, and the rhythm is not regular.
E. Pre-procedural stimulation Some patients may terminate or induce LBBB-type persistent idiopathic ventricular tachycardia, sometimes still under intravenous infusion of isoproterenol, which is more successful.
F. Judging the origin of the right ventricle: the same non-sustainability characteristics.
G. Intermittent ECG during the onset of seizure: visible homotypic ventricular premature contraction.
H. Signal average ECG is normal.
The relationship between the two types of LBBB idiopathic ventricular tachycardia: most of them only show one type, a small number of patients can be recurrent non-sustained and then evolved into persistence: others show first For persistent ventricular tachycardia, then spontaneously stop the episode, and it is non-sustainable between the two episodes. Then, after a period of time, the ventricular tachycardia no longer occurs, and the heart rhythm becomes sinus.
(2) RBBB type persistent idiopathic ventricular tachycardia: this type accounts for 30% of idiopathic ventricular tachycardia, which is much lower than the incidence of LBBB type, most of which are persistent, individual It is non-sustainable and its ECG features are as follows:
The duration of a 1-ventricular tachycardia episode is long: both in 30s to hours or hours.
2 Spontaneous or induced atrial, ventricular stimulation RBBB type idiopathic ventricular tachycardia is persistent monomorphic ventricular tachycardia, QRS waves are RBBB type (Figure 3), QRS>0.12s.
The frequency of 3-ventricular tachycardia is faster: 120-250 times/min, with an average of 180 beats/min.
4 seizures in the intermittent phase of the same type of ventricular premature contraction.
8QRS wave frontal ECG axis 85% left deviation: about 15% is extremely right deviation, the origin is mostly located at the left posterior branch of the left ventricular septum, a few are located at the left anterior branch, and the origin is from the left ventricular free wall, The right axis of the electric axis is relatively rare, and some originate from the left ventricular outflow tract.
The 6aVL lead presents an R or RS pattern.
2. Special types of idiopathic ventricular tachycardia
(1) Branch ventricular tachycardia: more common in adolescents, general examination did not find the basis of organic heart disease, repeated episodes of ventricular tachycardia, but the impact on hemodynamics is small, does not deteriorate into ventricular There is no special serious symptom in the tremor, and it is often misdiagnosed as supraventricular tachycardia. Because of the obvious effect of verapamil treatment, it is believed that its mechanism is mostly triggered activity, related to post-depolarization, electrophysiological research in recent years. Support for the return mechanism, ECG features:
When a ventricular tachycardia occurs: the time limit of the QRS wave is often 0.12 s, rarely reaching or exceeding 0.14 s.
2QRS wave is a right bundle branch block with left anterior branch or left posterior branch block: the origin is mostly located in the lower left ventricular septum, and a few patients with QRS waves are left bundle branch block with electric axis left or In the right-biased pattern, the origin is mostly located in the right ventricular outflow tract or the right bundle branch.
3 ventricular rate rarely exceeds 180 times / min: after termination of ventricular tachycardia, the electrocardiogram returns to normal, some patients with ECG can appear ST segment decline and T wave inversion, which is caused by the electrical tension adjustment mechanism.
(2) catecholamine sensitive VT: the onset of this type of ventricular tachycardia is associated with sympathetic excitation, increased adrenaline secretion, and exercise and stress can induce ventricular tachycardia. Onset, 50% to 70% of patients can induce ventricular tachycardia through exercise test. Intravenous infusion of isoproterenol-induced ventricular tachycardia is the most reliable diagnostic method. Pre-procedural stimulation can not be induced or terminated. attack.
(3) idiopathic ventricular tachycardia with electrical tension adjustment T wave changes: ECG characteristics: when idiopathic ventricular tachycardia, branch ventricular tachycardia after the recovery of sinus rhythm, ECG and Before the onset of tachycardia, the T wave of the same lead is inverted (ie, the T wave is inverted in II, III, avF, V3 to V6, and the amplitude can be as deep as 0.1 to 1.0 mV), which is called electric tension adjustment T. Wave changes (can also be accompanied by ST segment down), this system has undergone a transient change, more than a few days or more than 10 days to recover, the mechanism is still unclear, some people think that ventricular tachycardia when myocardial involvement, myocardial fiber pull Long, even if the ventricular tachycardia is stopped, the myocardial repolarization is not normal, which can cause the T wave to change.
(4) idiopathic ventricular tachycardia with efferent block: in a few cases, when ventricular tachycardia occurs, there is a blockade around the ventricular ectopic pacemaker, mostly second degree, showing 2 : 1, 3: 2 out of block, resulting in different RR intervals.
(5) idiopathic ventricular tachycardia with ventricular conduction block.
Diagnosis
Diagnosis and diagnosis of idiopathic ventricular tachycardia
diagnosis
1. There is a history of recurrent tachycardia.
2. Clinically asymptomatic, palpitations, chest tightness, dizziness, etc., but no syncope.
3. After comprehensive examination, there is no basis for organic heart disease.
4. The electrocardiogram shows that the QRS waveform of the monomorphic ventricular tachycardia is LBBB type non-sustained ventricular tachycardia, the right axis of the electric axis (+90°) is normal or left-biased; the LBBB type is persistent. In the case of ventricular tachycardia, the right axis of the tachycardia, individual left deviation, RBBB type persistent idiopathic ventricular tachycardia, the left axis of the electric axis, with right deviation is rare.
5. Verapamil or propafenone intravenously mostly terminates ventricular tachycardia.
Differential diagnosis
1. Identification of idiopathic ventricular tachycardia and pathological paroxysmal ventricular tachycardia: although the electrocardiographic findings of both are the same as monomorphic ventricular tachycardia, the ECG features are similar, but the cause The clinical significance is quite different. The identification of the two is not difficult. The differential diagnosis of arrhythmia must be combined with clinical comprehensive analysis. The characteristics of pathological paroxysmal ventricular tachycardia are: more than 190% of patients have structural heart disease. 70%80% occur in patients with coronary heart disease; 2 electrocardiogram often has ischemic ST-segment depression, T wave abnormality or myocardial infarction pattern; 3 pre-procedural stimulation can induce persistent ventricular tachycardia, induced The mortality rate is high; 4 the prognosis is severe, and idiopathic ventricular tachycardia mostly occurs in normal people, and the majority of patients have a good prognosis.
2. LBBB type idiopathic ventricular tachycardia and pathological paroxysmal ventricular tachycardia after myocardial infarction and arrhythmogenic right ventricular dysplasia ventricular tachycardia on electrocardiogram
(1) LBBB type idiopathic ventricular tachycardia QRS frontal ECG axis is mostly right deviation, a few are normal or left deviation; and myocardial infarction pathological paroxysmal ventricular tachycardia electrocardiogram Left-sided: arrhythmogenic right ventricular dysplasia ventricular tachycardia is mostly left-biased, a few are normal.
(2) LBBB type idiopathic ventricular tachycardia aVL lead is QS type, and pathological paroxysmal ventricular tachycardia aVL lead after myocardial infarction is R type; right ventricular dysplasia aVL lead is R Or S type.
(3) LBBB type idiopathic ventricular tachycardia limb lead R wave amplitude sum 40mV accounted for 70.9%, no QR type (but occasionally exception), and pathological paroxysmal ventricular tachycardia limb The lead R wave amplitude 40mV only accounted for 5%, and 75% of patients with QR pattern, right ventricular dysplasia 40mV only accounted for 20%.
3. Identification of paroxysmal supraventricular tachycardia with indoor differential conduction
Because the onset of idiopathic persistent ventricular tachycardia is paroxysmal and lasts for a long time, it is often misdiagnosed as paroxysmal supraventricular tachycardia in young patients. The identification at this time is mainly based on the presence or absence of atrioventricular tachycardia. Separation, if accompanied by idiopathic ventricular tachycardia, can be used to make an esophageal lead ECG to fully show the atrioventricular septum.
