Bidirectional ventricular tachycardia
Introduction
Introduction to bidirectional ventricular tachycardia Bidirectional ventricular tachycardia (BVT) is a rare and severe monomorphic ventricular tachycardia in which the QRS waves of the two opposite morphologically large deformities appear alternately in the same lead. basic knowledge The proportion of illness: 0.02% Susceptible people: no special people Mode of infection: non-infectious Complications: sudden death, A-S syndrome, tachycardia cardiomyopathy
Cause
Bidirectional ventricular tachycardia
(1) Causes of the disease
Often occurring in digitalis poisoning, especially in severe myocardial lesions and more severe myocardial ischemia, hypoxia and heart enlargement, in addition, also seen in aconitine poisoning, amantadine poisoning, hypokalemia periodic paralysis Patients, occasionally no clear heart disease.
(two) pathogenesis
1. Dual-source ventricular agitation
Excited originated from two ectopic pacemakers in the left ventricle and right ventricle, alternating impulses to form a bi- ventricular tachycardia. The origin of the rhythm point can be judged according to the V1 lead QRS wave shape. For the following 3 types:
(1) Endocardial Pu's fiber tip type: The electrocardiogram shows that the main wave direction of the QRS wave is sometimes upward, sometimes downward, and the morphology of the two QRS waves in the opposite direction is completely different. Electrophysiological examination proves that it is due to electrical stimulation. The two ventricular depolarization vectors caused by the outgoing and incoming directions formed by the micro-return cycle.
(2) Right bundle branch block type: QRS wave with sinus rhythm in electrocardiogram shows RBBB type and ventricular heart rhythm QRS wave alternates with LBBB type. If there is ventricular fusion wave, QRS normalizes. On the beam electrogram, it can be seen that the RBBB type QRS wavefront has a fixed HV interval, while the LBBB type QRS wavefront has no H wave.
(3) High beam branch block type: Two stimuli originate from two bundle branches, one in the left anterior branch and one in the left posterior branch. This bidirectional ventricular tachycardia is equivalent to the alternating Cohen high beam branch rhythm The His's beam electrogram can assist in the identification, the sinus rhythm HV interval is 50ms, the left anterior branch H'-V interval is 30ms; the left posterior branch H'-V interval is 0ms.
2. Single-source supraventricular sexual excitement
For an supraventricular ectopic pacemaker, most of the activation of the atrioventricular junction area alternately follows the left and right bundle branches, resulting in left and right bundle branch block patterns. Some people think that digitalis poisoning often has a right bundle. Branch block, on the basis of which the tachycardia originating from the atrioventricular junction alternately descends along the left anterior branch and the left posterior branch, thus producing a QRS wave alternation change; it can also be a compartmental tachycardia combined with alternation Sexual indoor differential conduction, this category does not belong to the true two-way ventricular tachycardia, the 12-lead ECG should be carefully analyzed and identified.
3. Mixed excitement
One ectopic pacemaker is located in the ventricle, and the other ectopic pacemaker is located at the junction of the chamber, and the impulse is alternately distributed. The QRS wave pattern, the time limit is different, and the RR interval is not equal.
Prevention
Bidirectional ventricular tachycardia prevention
1. Active treatment of primary disease is a fundamental measure to prevent bidirectional ventricular tachycardia.
2. Bidirectional ventricular tachycardia is more common in digitalis poisoning. Therefore, it is necessary to master the indications when using digitalis drugs. The blood drug concentration and clinical symptoms should be closely monitored during the treatment process.
Complication
Bidirectional ventricular tachycardia complications Complications sudden death A-S syndrome tachycardia cardiomyopathy
Common complications of ventricular tachycardia are sudden cardiac death, A-S syndrome, tachycardia cardiomyopathy, and heart failure.
Sudden cardiac death
Arrhythmia sudden cardiac death accounts for 80% to 90% of ventricular tachyarrhythmia. Large-scale clinical retrospective studies have shown that more than 10% of patients with sudden cardiac death outside the hospital are characterized by ventricular tachycardia. % to 85% of patients present with ventricular fibrillation during emergency treatment, and sudden cardiac death is the most serious complication of ventricular tachycardia.
2. A-Syndrome
Also known as acute cardiogenic cerebral hypoxia syndrome, refers to a transient cerebral ischemia, acute and transient loss of consciousness caused by cerebral hypoxia, accompanied by convulsions, pale complexion, cyanosis syndrome, in clinical Among electroacupuncture patients with syncope, rapid ventricular arrhythmia accounted for 20% of the cause of syncope.
3. Tachycardia cardiomyopathy
Long-term tachycardia can lead to changes in the histology and pathology of the heart similar to dilated cardiomyopathy. The clinical manifestations of heart enlargement and decreased cardiac function are called tachycardia. Some scholars speculate that chronic tachycardia Rapid episodes of more than 10% to 15% of the total time per day may develop into tachycardia, ventricular tachycardia, including short-term ventricular tachycardia, recurrent episodes of continuous ventricular tachycardia Rapid, torsade-induced ventricular tachycardia, concurrent rhythm ventricular tachycardia and bidirectional ventricular tachycardia can cause tachycardia.
4. Heart failure
Ventricular tachycardia, including persistent or non-sustained ventricular tachycardia, can lead to congestive heart failure.
Symptom
Bidirectional ventricular tachycardia symptoms Common symptoms tachycardia syncope, flustered, chest tightness, chest pain, black ventricular edema
Most ventricular tachycardia is paroxysmal. In the onset of ventricular tachycardia, patients may have palpitation, chest tightness, chest pain, darkness, syncope, and more serious organic heart disease. After the onset of rapid attack, the contraction of myocardial contraction is weakened, the contraction time of ventricle and atrium is not synchronized, and the filling and discharge of ventricle are significantly reduced. Patients can rapidly develop into serious consequences such as heart failure, pulmonary edema or shock, and some may even develop. Sudden cardiac death for ventricular fibrillation.
Examine
Bidirectional ventricular tachycardia
ECG features
(1) Heart rate is 140-200 beats/min, and there are reports of 120-150 beats/min, most rhythm is neat, a few rhythms are irregular, RR interval rules of the same form QRS wave in the same lead, RR of different form QRS waves The intervals may be unequal, alternating in length and length.
(2) Mostly non-sustained (short-term episodes): It can also be persistent. The duration of the episode is only a few seconds to a few minutes. It can be terminated by itself and can be repeated.
(3) QRS wide and wide deformity: the individual is normal, the QRS time limit is 0.14~0.16s, and there is also a QRS wave wide deformity of bidirectional ventricular tachycardia caused by digitalis poisoning, which is equal to or less than or slightly greater than 0.12s. Not too obvious.
(4) There are two types of depolarization vectors: the electrocardiogram shows that the direction of the main wave of the QRS group changes alternately, that is, once upwards and once downwards; or in some leads, the QRS main wave is once wider, once more Narrow; or presenting the QRS wave main wave to be higher once, lower at one time; or in one group (several ventricular premature contraction), the QRS main wave is upward, and a group of QRS main waves alternately appear downward, also called alternating Sexual dual bidirectional ventricular tachycardia.
(5) The standard limb leads are alternately rotated right and left: ie, +120° to +130° and -60° to -80° alternately appear.
(6) Two-way ventricular premature contraction similar to bidirectional ventricular tachycardia may occur in the intermittent period of ventricular tachycardia.
(7) The V1 lead is in the QS type or the R type.
(8) The basic rhythm can present a variety of heart rhythms: for example, sinus rhythm, paroxysmal atrial tachycardia, atrial fibrillation, etc.
Diagnosis
Diagnosis and diagnosis of bidirectional ventricular tachycardia
diagnosis
Physical examination: heart rate is more than 140 ~ 200 times / min, most of the heart rhythm, a small number of arrhythmia, the first heart sound of the apex of the heart.
1. There are two kinds of ventricular depolarization vectors on the electrocardiogram, and the direction of the main wave of the QRS wave changes alternately.
2. More common in severe organic heart disease or digitalis and other drug poisoning.
Differential diagnosis
Bidirectional ventricular tachycardia should be distinguished from simple QRS waves: both have similar causes, most of which are accompanied by organic heart disease; but the latter ECG shows QRS wave amplitude alternating high and low, QRS The wave time limit is normal, which is completely different from the two-way alternating QRS wave, and is easier to identify.
