Pediatric torsades de pointes ventricular tachycardia
Introduction
Introduction to pediatric torsade ventricular tachycardia Torsades tachycardia (TDP) is a special type of polymorphic rapid ventricular arrhythmia. It is clinically divided into two cases: one is torsades de pointes and QT The interval is prolonged, and a small number of torsades ventricular tachycardia can be atypical; the second is the torsades de pointes and the QT interval is prolonged. Because of its large differences in pathogenesis and treatment, most scholars refer to the former as "threshold torsade ventricular tachycardia", or "QT interval prolongation and polymorphic ventricular tachycardia", the latter is called "polymorphic room" Speed", patients with torsades de pointes ventricular tachycardia with repeated syncope, convulsions as the main clinical manifestations. basic knowledge The proportion of the disease: the incidence rate is about 0.002% - 0.007%, mostly in children with myocarditis or cardiomyopathy Susceptible people: children Mode of infection: non-infectious Complications: syncope, shock, heart failure, sudden death
Cause
Pediatric torsade ventricular tachycardia
(1) Causes of the disease
The torsade-type ventricular tachycardia is divided into congenital and acquired.
Mostly adrenaline-dependent, LQTS three genes are long-term intermittent, mostly family history, autosomal dominant, can also be idiopathic, by emotional stress, stress, exercise or beta receptor Induced by stimulants, more common in children and adolescents, also seen in neonates, Hofbeck found 9 cases of fetal bradycardia, a long QT interval syndrome after birth, complicated by torsades de pointes, syncope.
This type is more common, mostly long intermittent dependence, including low blood potassium, low blood calcium, low blood magnesium and other electrolyte disorders, antiarrhythmic drugs and digitalis poisoning, bradycardia, central nervous system diseases, organic Heart disease, etc.
(two) pathogenesis
Idiopathic long QT syndrome (LQTS) is a genetic factor. Recent molecular genetic studies have confirmed that LQTS is involved in gene mutations encoding cardiomyocyte ion channel proteins. To date, at least three disease-causing genes have been identified, namely the third Mutations of SCN5A, HERG and KVLQT1 genes on chromosomes 7 and 11, in addition, there may be two other disease genes, SCN5A encodes a sodium channel protein that synthesizes the myocardium, and the mutation of the gene enhances the function of the encoded channel protein, making sodium The channel inactivation gate is unstable, and the repeated channel opening in the action potential time limit is formed. The sodium ion inflow causes the action potential time to be prolonged (QT is prolonged), and a rapid arrhythmia occurs. The synthesis of the potassium channel protein of the HERG line is made after the mutation. The HERG reduces the function of the encoded potassium channel protein, ie, the channel block, delays the repolarization, prolongs the action potential, and induces reentry or triggering activity. The physiological function of the protein encoded by KVLQT1 is not yet clear, and the amino acid sequence predicted by anti-complementary DNA is suggested. , the protein is a member of the new potassium channel family, although the molecular biological basis of the SCN5A and HERG mutations are different, but they are The cellular and functional consequences are the same, that is, the myocardial repolarization is delayed, and the cell electrical stability is reduced. At present, the above molecular breakthrough of LQTS has been applied to clinical research, and meaningful results have been obtained, and the abnormalities of myocardial repolarization in LQTS have been obtained. Prolonged, leading to the formation of post-potential, can trigger ventricular tachycardia. In addition, after animal experiments and clinical observations, patients often suffer from ventricular arrhythmia caused by emotional load or physical load, resulting in sudden death, using beta blockers or left side. Cardiac sympathectomy has a certain effect, and sympathetic imbalance has been considered as one of the pathogenesis of this disease for many years.
Prevention
Pediatric torsade ventricular tachycardia prevention
Prevention and treatment of electrolyte imbalance and acid-base imbalance, active treatment of primary disease, such as a variety of gastrointestinal disorders, uremia, nervous system factors and drug poisoning caused by arrhythmia. Life should be regular and avoid fatigue. If you induce syncope after exercise, you should restrict exercise. Avoid using drugs that prolong the QT interval, including non-cardiovascular drugs. Ban IA, IC and Class III antiarrhythmic drugs, try IB drugs. Intravenous potassium supplementation, magnesium supplementation (caused by electrolyte imbalance).
The family members of the patients should be examined by ECG. Congenital patients under the age of 40 are considered to have beta-adrenergic blockers for intermittent use.
Complication
Pediatric torsion ventricular tachycardia complications Complications, syncope, heart failure, sudden death
Often accompanied by syncope, shock, heart failure, and even sudden death.
Symptom
Pediatric torsade ventricular tachycardia symptoms Common symptoms Powerless tachycardia syncope convulsions palpebral heart enlargement arrhythmia deafness cardiac arrest ventricular fibrillation
Torsades ventricular tachycardia can occur in children at various stages. The most common symptoms are repeated syncope and/or convulsions, often induced during exercise, stress, and emotional stress. Infants and young children are induced by crying and frightening. Infrequent, some frequent episodes for several days, the Guangdong Medical College Affiliated Hospital has diagnosed a case, every 5 to 20 minutes of episodes, repeated 2 days, some seizures sparse, months or even a few episodes, duration of seizures From a few seconds to a few minutes, the episodes of the children with intermittent seizures, normal mental symptoms, but the symptoms are frequent, but the author may be apathetic, and suddenly appear pale or blemishes on the attack, followed by limb twitching or weakness, heart rate 200 ~ 300 times / min, the heart rhythm is absolutely not complete, the heart sounds are not strong, can not even hear clearly, the intermittent auscultation is often sinus bradycardia, heart sounds weak or normal, some children suddenly die, in general, X-ray of the heart, two-dimensional ultrasound and ventricular angiography can be normal, repeated authors can appear heart enlargement and cardiac insufficiency, its clinical features are sudden syncope, convulsions, and even cardiac arrest, most of It occurs when the thread excitement (angered, frightened), or movement, were recurrent.
Examine
Examination of pediatric torsade ventricular tachycardia
Should be routinely used for myocardial zymogram, erythrocyte sedimentation rate, anti-"O", blood electrolysis value, pH value and immune function examination, routine electrocardiogram, chest X-ray, echocardiography, LQTS ECG features:
1. Bradycardia, often sinus bradycardia, 5% can have II degree above atrioventricular block, and there is a borderline escape rhythm.
2. The QT interval is extended according to the Bazett formula QTc>0.44s.
3. The T wave is wide and deformed and has an alternating phenomenon.
4. Visible monocular or polymorphic premature contractions.
5. Torsion-type ventricular tachycardia occurs during syncope, which can develop into ventricular flutter or tremor.
Diagnosis
Diagnosis and diagnosis of pediatric torsade ventricular tachycardia
diagnosis
In 1985, Schwartz proposed the diagnostic criteria for LQTS and divided its symptoms into two broad categories:
1. Main symptoms: 3 items: QTc>0.44s, stress induced syncope and LQTS patients in the family.
2. Minor symptoms: 4 items: Congenital deafness, T wave alternation, pediatric heart rate slowdown and ventricular repolarization abnormality, patients with 2 main symptoms or 1 main symptom and 2 secondary symptoms can diagnose LQTS.
3. Scoring method: After trial, QTS diagnostic standard scoring method, see Table 1, score <1, low probability of LQTS; 2~3 points, LQTS moderate possibility; 4, LQTS height possible.
Differential diagnosis
In the differential diagnosis should be distinguished from epilepsy, the latter EEG abnormalities, no ECG abnormalities.
1. Epilepsy: The torsade-type ventricular tachycardia can be sudden and sudden, and the clinical manifestations are repeated syncope and/or convulsions. Therefore, it is mainly distinguished from epilepsy. The former often has syncope, cyanosis, and convulsions. Those who have convulsions and convulsions first, and then have convulsions, and conventional ECG and ECG monitoring to capture the onset of ECG is a key means to identify this diagnosis. For the authors who are less frequent, the cardiac event recorder can be used to record transient ECG changes to help confirm the diagnosis. .
2. Sinus bradycardia and A-S syndrome: patients with congenital long QT syndrome and torsades de pointes ventricular tachycardia, intermittent sinus bradycardia, easily misdiagnosed as sinus bradycardia with A -Syndrome syndrome and limited treatment, if you pay attention to carefully read the electrocardiogram, find QT changes, timely ECG monitoring during the attack, can be diagnosed, Guangdong Medical College Affiliated Hospital has treated 1 case of such cases, repeated frequent episodes of syncope, local The hospital diagnosed as bradycardia and A-S syndrome, treatment with atropine has been ineffective, and ECG monitoring found a typical torsade-type ventricular tachycardia at the onset of the attack, after treatment to terminate the attack after treatment.
