Adrenergic-dependent torsades de pointes

Introduction to adrenergic-dependent torsade ventricular tachycardia Adrenergic dependent torsadesades ventricular tachycardia (ADTdpVT) is a multi-ion channel abnormality caused by genetic defects of multiple gene mutations, resulting in prolonged QT interval, recurrent TDP, recurrent syncope and Sudden clinical syndrome. basic knowledge The proportion of illness: 0.003% Susceptible people: no special people Mode of infection: non-infectious Complications: syncope, A-S syndrome, sudden death

Adrenergic-dependent causes of torsades de pointes ventricular tachycardia

(1) Causes of the disease

In the past, ADTdp was divided into the following three types:

1. Jervell-Lange-Nielson syndrome (JLNS): characterized by congenital deafness, prolonged QT interval, abnormal T wave, and torsades de pointes ventricular tachycardia (TDP) under stress and stress Ventricular fibrillation, even syncope, sudden death, is an autosomal recessive hereditary disease.

2. Romano-Ward syndrome (RWS): autosomal dominant hereditary disease, without deafness, the same as JLNS, Ganstorp syndrome is a subtype of RWS, manifested as no congenital deafness, with serum potassium reduction .

3. Scattered hairstyle: no family history, normal hearing, the rest with JLNS.

(two) pathogenesis

In recent years, it has been recognized that gene mutation is the basic cause of its genetic basis. ADTdp is genetically heterogeneous. It is known that at least six LQTS (LQT1~LQT6) mutation sites are autosomal dominant, five of which are already On the chromosome, four related mutation genes have been established, JLNS belongs to LQT1, and the related mutation gene is KVLQT1. When the parental parents of JLNS patients both contain KVLQT1 and the abnormal gene is homozygous from parental inheritance, KVLQT1 makes cardiac ion channel. Abnormal function, that is, abnormal regulation of potassium channel, which makes the myocardial repolarization significantly delayed, and the QT interval is prolonged. It is autosomal dominant inheritance, and its gene carriers only have TDP when conditions such as low potassium, KVLQT1 is also encoded. Congenital hearing abnormalities and deafness occur in hearing elements, while deafness is autosomal recessive. Because the conditions for forming JLNS are so special, JLNS is rare. Other types of LQT constitute RWS, so RWS is caused by multiple genetic defects. Due to autosomal dominant inheritance, the known related genes are LQT2, LQT3 (HERG), LQT4 (SCN5A), LQT5, LQT6 (KCNE4).

Defective genes mediate cell membrane ion channel regulation dysfunction: SCN5A encodes a sodium channel to increase Na inward current, and its ion mediated may be related to Cl-anomaly. KVLQT1, KCNE1 and HERG encode potassium channels, which reduce K outward current, so Which one or more gene mutations can cause a decrease in K outflow, and/or an increase in Na influx, that is, an increase in inward current, resulting in prolonged time course of action phase 2 and phase 3 and increased membrane potential, resulting in repolarization delay and Incomplete, the ECG showed prolonged QT interval, abnormal TU wave, and triggered arrhythmia caused by post-depolarization (especially early post-depolarization EAD) due to this electrical abnormality, which was manifested as TDP or ventricular fibrillation. The formation and maintenance of EAD and TDP are also related to myocardial M cells. The maintenance of arrhythmia is related to the mechanism of reentry.

JLNS is more emotional, nervous, exercise and fatigue, resulting in increased heart rate when TDP occurs, manifested as paroxysmal syncope or even sudden death, which is associated with increased sympathetic tone, increased catecholamines promote calcium channel opening, Ca2 influx increased, because Promote the increase of inward current, increase the imbalance of ion flux inside and outside the cell membrane, and more prone to post-depolarization, especially EAD and triggered arrhythmia. Some ADTdp usually do not show QT interval prolongation, only when sympathetic tone is increased, introversion The increase in current is more pronounced. Therefore, JLNS and RWS and their associated TDP are called adrenergic-dependent TDP, but a small number of patients with ADTdp are in sleep or quiet state (for HERG and SCN5A gene defect types). ), which is intermittently dependent; at the same time, adrenergic nerve excitation can also promote the onset of TDP in patients with secondary LQTS caused by drugs, indicating that there is a slight crossover between the two types in the mechanism of occurrence.

Adrenergic-dependent torsades de pointes ventricular tachycardia prevention

Prolonged ventricular repolarization related drugs (such as isoproterenol and other catecholamines and atropine) should be disabled, because the QT interval can be prolonged, T, U waves increase, and TDP occurs. Patients should avoid severe Even without intense physical activity, stimulating sound, light and emotional excitement, the patient family should be censused in order to detect "hidden" patients early, and patients with prolonged QT interval without syncope should be given preventive treatment. Beta blockers.

In addition to avoiding or actively treating the factors that cause the prolongation of QT interval, it is necessary to timely understand the drug use and changes in the condition of the drug, and find out the situation in a timely manner, which can effectively prevent its occurrence.

Adrenergic-dependent complications of torsades de pointes ventricular tachycardia Complications syncope A-S syndrome sudden death

Serious complications such as syncope, convulsions, A-S syndrome and sudden cardiac death can occur.

Adrenergic-dependent torsades ventricular tachycardia symptoms Common symptoms Sympathetic nerve tension is adrenergic-dependent urinary incontinence syncope vertigo convulsions sleepiness sudden loss of consciousness

ADTdp is rare. About 3,000 children and adolescents die each year in the United States. About 2/3 of the gene carriers have syncope. The sudden death rate is about 15%. The age of onset is from days to 50 years after birth. The age of first onset of TDP The stage is mostly in infants and children, mainly manifested by paroxysmal syncope and sudden death. The syncope occurs almost in the case of high sympathetic tone or sudden changes in tension (the adrenaline-dependent characteristics of the attack), such as strenuous exercise, fatigue , defecation, nervousness, pain, fear, anxiety, nightmares, sound and light stimulation, etc., the heart rate gradually accelerates and ventricular premature contraction, which induces TDP, sometimes can be converted into ventricular fibrillation and sudden death, the symptoms are not lost, Only black Mongolian, dizziness, blurred vision, anxiety, embarrassment, shouting, etc., severe cases of syncope, loss of consciousness, convulsions, urinary incontinence, sudden death, easy to be misdiagnosed as epilepsy, often burnout or lethargy within 24 hours after the attack, The number of TDP or syncope episodes is as many as one day, from a few years to a single or a lifetime of only one or two episodes. With age, the QT interval is gradually shortened, and the number of episodes is reduced accordingly. , JLNS associated with congenital deafness and bone deformities, family members were seen prolong the QT interval, unexplained syncope or sudden death, clinically dependent TDP will be divided into the following adrenergic type 3:

1. Typical:

The disease is initially in infants and children, but it can also be delayed to 30 years or adulthood. The main feature is paroxysmal syncope, which is caused by TDP, often caused by sudden movement, fear, pain, shock or emotional arousal. It can be dependent on epilepsy.

2. Untypical:

The incidence of this type is higher than that of the typical type. In the exercise and mental stress, the U wave increases and TDP appears. The clinical manifestations are lighter. The TDP is often caused by exercise test or IA antiarrhythmic drug treatment due to ventricular premature contraction. Excitation tests such as exercise tests and instillation of isoproterenol can be induced.

3. Intermediate type:

Some patients with LQTS develop TDP when adrenaline is excited, and TDP also occurs when there is a long heartbeat. The former is treated with beta blockers, the latter can be used to terminate TDP with isoproterenol, and the other part has obvious U. Waves, TDP did not have long pauses, and there was no significant relationship with physical exertion or emotional agitation.

Adrenergic-dependent examination of torsades de pointes ventricular tachycardia

1. ECG examination features

(1) Characteristics of intermittent electrocardiogram in the adrenergic-dependent TDP episode:

1Q-T interval extension and T, U wave anomaly:

A. QT interval prolongation: the traditional diagnostic criteria are QT interval and QTc 0.44s. The international common diagnostic criteria proposed in 1993 are male 0.45s, female 0.46s, for prolonged, the patient's QT interval is usually extended. It is a long-term existence, but its degree often changes, sometimes it does not prolong, it can be gradually shortened with the increase of age, exercise can prolong the QT interval, and the length of QT interval is related to the type of mutant gene, LQTS1, LQTS2 The QT interval was mostly normal, and the QT interval of LQTS3 and LQTS4 was prolonged. In the few seconds to several minutes before the onset of TDP, the QT interval (QTc interval) was significantly prolonged, the TU wave was abnormal, and the performance was beaten. Different, changing day by day, and even transient changes, the QT interval is mostly >0.44s in the onset of TDP, and a small number of patients >0.60s.

BT, U wave morphology anomaly: T wave width is wide, U wave amplitude is increased, T wave morphology of LQTS subtypes of different types of mutant genes may be different, which can be expressed as widening, sharpening and lowering, etc. (T-wave forward and negative alternately appear), often appear before the onset of adrenergic-dependent TDT, and intermittent-dependent TDP does not have this feature, can be identified, it is also an important and objective identification of high-risk patients Index, U wave can also be significantly increased (>0.15mV is a significant U wave), can also be U wave alternating, especially in the presence of QT (U) electric alternation more diagnostic value, TU amplitude, QT electricity alternate, can be fluctuating Sexual changes are closely related to the patient's degree of disease development, strenuous exercise and emotional agitation. Complex TU morphological changes are often precursors to severe arrhythmias.

2 during the interval of seizures or when the QT interval is normal: when the method of increasing the sympathetic tone is increased, such as exercise test, cold pressurization test or Valsalva action, or intravenous infusion of isoproterenol to increase heart rate, It can prolong the original QT interval extension, delay the normal QT interval, increase the T wave, widen the U wave amplitude, and induce TDP. Kadise (1990) proposed that the QT is normal at rest. The abnormal extension of exercise is the concept of "potential LQTS", which indicates that the changes in T and U waves can be predicted by the family exercise test of LQTS patients.

3 ventricular premature contraction or R-on-T ventricular premature contraction during the interval of seizure: the basal rhythm is mostly sinus rhythm.

4Q-T interval dispersion is large: the difference between the longest and shortest QT intervals in conventional lead is QT interval dispersion, reflecting the dispersion of ventricular repolarization (QTd), normal people are 89ms, LQTS patients are 155ms.

(2) Electrocardiographic characteristics of adrenergic-dependent TDP episodes: the frequency of onset is 150-180 beats/min, and TDP can be induced by R-on-T type (R-on-U type) ventricular premature contraction. When the ventricular repolarization time is extremely prolonged QT/RR1, the uniform and normal heartbeat can also fall into the repolarization period of the abnormal ventricular delay to induce ADP. This type of ADP does not have the characteristics of a long period and a short period. It is one of the main basis for identification with intermittent dependent ADP.

Diagnosis and identification of adrenergic-dependent torsades degenerative ventricular tachycardia

diagnosis

In 1993, Schwarts proposed the LQTS diagnostic criteria for scoring, which is the current international diagnostic standard.

Differential diagnosis

Distortion of torsade ventricular tachycardia and other polymorphic ventricular tachycardia is difficult, mainly based on the prolongation of QT interval, U wave, often no serious organic heart disease, have a special cause, often recurrent and Can be terminated by itself.

In addition, it must be differentiated from general ventricular tachycardia or ventricular fibrillation. The general ventricular tachycardia is characterized by a series of wide QRS waves with almost fixed shape. The ST segment and T wave can be identified, and the occurrence often does not stop by itself. The general ventricular tachycardia can also be used by the RonT chamber. Early induction, but the interval between early ventricular compartments is short, and QRS waves and ST segments and T waves cannot be recognized during ventricular fibrillation, and the seizure persists and dies.

The disease should be differentiated from paroxysmal syncope and sudden death, such as intermittently dependent TDP, pre-excitation syndrome with extreme atrial fibrillation, idiopathic ventricular fibrillation, Brugada syndrome, sick sinus syndrome, and epilepsy. Phase identification should exclude the extension of secondary QT interval.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.