Tachycardia

Tachycardia - an increase in the heart rate of more than 100 per minute. The negative effect of tachycardia on the myocardium is explained by the fact that coronary blood flow is carried out mainly during diastole. At an excessively high heart rate, the duration of diastole is critically reduced, which leads to a decrease in coronary blood flow and myocardial ischemia. The frequency of rhythm, in which such violations are possible, with a narrow complex tachycardia is more than 200 in 1 minute and with a large-scale tachycardia more than 150 in 1 minute. This explains why the wide-complex tachycardia is worse.

If an electrocardiogram or ECG monitoring registers a tachycardia, but there is no ripple over the arteries, then this condition is regarded as a cardiac arrest, and not as a periarest arrythmia. Treatment of such patients is carried out according to the universal algorithm of resuscitation. An exception to this rule is the case when there is a tachycardia with narrow QRST complexes with a very high heart rate (over 250 per minute). There are two types of periarest tachycardia:

• tachycardia with narrow QRS complexes;
• tachycardia with wide QRS complexes.

Usually, tachycardia with narrow QRS complexes causes less disruption of the cardiovascular system than tachycardia with wide QRS complexes.

If pulsation is determined on the arteries, then the presence or absence of the following unfavorable prognostic signs should be assessed:

• Blood pressure below 90 mm Hg. P.
• Heart rate more than 150 per minute;
• chest pain;
• heart failure;
• impaired consciousness.

In parallel with the initial examination, the patient should:

• to adjust the supply of oxygen;
• ensure reliable intravenous access;
• To register an electrocardiogram in 12 leads.

Compared with electrical cardioversion, antiarrhythmics act more slowly and converting tachycardia into a sinus rhythm when used less efficiently. Therefore, drug therapy is used in patients with a stable condition without adverse symptoms, and electrical cardioversion is more preferable in patients with unstable state and with adverse symptoms.

If the patient has a hemodynamic instability in the periarest period with progressive deterioration of the condition (presence of threatening signs, systolic blood pressure less than 90 mm Hg, frequency of ventricular contractions more than 150 per minute, heart failure or other signs of shock) due to severe tachycardia it is necessary to carry out a synchronized cardioversion in an emergency. If it is ineffective, you should inject 300 mg of cordarone (within 10-20 minutes) and repeat the cardioversion attempt. Further supportive infusion of 900 mg of Cordarone is shown for 24 hours.

Scheme of conducting electropulse therapy:

• oxygen therapy;
• premedication (fentanyl 0.05 mg or promedol 10 mg iv);
• sedation (diazepam 5 mg IV and 2 mg every 1 -2 minutes before falling asleep);
• heart rate control;
• synchronization of the electrical discharge with the tooth R on the ECG;
• cardioversion with the recommended dose (with tachycardia with wide QRS complexes or with atrial fibrillation, the initial discharge is 200 J monophasic or 120-150 J biphasic, with atrial flutter and tachycardia with regular narrow QRS complexes, the initial discharge is 100 J monophasic or 70-120 J biphasic);
• if there is no effect, an antiarrhythmic drug should be given, indicated for this arrhythmia;
• if there is no effect, repeat cardioversion by increasing the energy of the discharge;
• If there is no effect, repeat the EIT with a maximum power discharge.

For the emergency recovery of the sinus rhythm of EIT, the following initial discharge energies are recommended:

• ventricular fibrillation and polymorphic ventricular tachycardia - 200 J;
• monomorphic ventricular tachycardia - 50-100 J;
• Atrial fibrillation is 200 J;
• Atrial flutter and paroxysmal supraventricular tachycardia - 50-100 J.

If tachyarrhythmia is not accompanied by severe hemodynamic disorders, then, first of all, it is necessary to determine whether there is a broadening of the QRS complex (normally the width of the QRS complex is less than 0.12 seconds).

Forms

Tachycardia with a wide QRS complex

The general principle of treatment of tachycardia with a wide complex of QRS in the periarest period is that this kind of tachycardia, first of all, should be considered as a ventricular one. There is a possibility that such an electrocardiographic picture may be due to supraventricular tachycardia with aberrant conduction (i.e., the bundle of the bundle that developed on the background of blockade), but it is better to treat the supraventricular tachycardia as ventricular than vice versa. Especially in a patient who has just undergone a stop of blood circulation. Nevertheless, it is recommended that certain rules for the interpretation of this type of electrocardiographic change should be followed in order to determine the most likely type of cardiac disturbance and to choose the most rational treatment tactics.

First of all, it is necessary to determine whether the rhythm of a tachycardia with wide QRS complexes is regular or not observed in the patient. Usually the regularity of the ventricular rhythm is determined by the intervals RR. If the teeth R follow one another at the same intervals, then we can definitely say that the rhythm is regular. If the intervals differ from each other, we should conclude that the rhythm is irregular. When tachyarrhythmias with an extended QRS complex sometimes have difficulties with the allocation of individual teeth, so the rhythm can be judged by the regularity of intervals between QRS complexes.

Tachycardia with a wide QRS and regular rhythm

In the absence of arterial hypotension, chest pain, heart failure and impaired consciousness, the patient should be given intravenous 300 mg of cordarone in a 5% glucose solution (for 10-20 minutes) followed by maintenance infusion (900 mg of cordarone for 24 hours).

Careful observation of the patient's condition is necessary, consultation of the cardiologist is necessary, one must be prepared to conduct electrical cardioversion with worsening of the patient's condition or a prolonged attack of tachycardia (if the attack lasts several hours).

If there is convincing evidence that a wide QRS complex is due to blockade of the bundle of the bundle and there is supraventricular tachycardia, then the algorithm for treating tachycardia with narrow QRS should be followed. In the case of uncertainty or any doubt, a similar tachycardia should be treated as a ventricular one.

It should always be remembered that for the acute phase of myocardial infarction and in patients with an established diagnosis of ischemic heart disease, it is most likely the development of ventricular tachycardia.

It is mandatory to take into account the underlying disease that caused heart rate failure. In all patients, correction of hypoxia, hypercapnia, acid-base and water-electrolyte balance disorders is important. It is possible to stop tachycardia with a wide QRS and regular rhythm with esophageal competing frequent stimulation.

Tachycardia with a wide QRS and irregular rhythm

Tachycardia with a wide QRS and irregular rhythm may be due to:

• atrial fibrillation (atrial fibrillation) with concomitant blockage of one of the legs of the bundle;
• atrial fibrillation with premature ventricular excitation (Wolff-Parkinson-White syndrome);
• polymorphic ventricular tachycardia (the probability of its development without severe disturbances of systemic hemodynamics is extremely small).

All patients should be consulted by a cardiologist and a specialist in the field of functional therapy. After the diagnosis is clarified, the treatment of atrial fibrillation with concomitant blockade of the legs of the bundle is performed according to the algorithm of treatment of atrial fibrillation. Patients with atrial fibrillation and Wolff-Parkinson-White syndrome should not use zlenozin, digoxin, verapamil or diltiazem. These drugs cause the block of the atrioventricular node and can aggravate the existing disorders. Optimum treatment of such patients is electrical cardioversion.

Treatment of polymorphic ventricular tachycardia should begin with the cessation of the administration of all drugs that extend the QT interval. It is necessary to correct the existing electrolyte imbalance (especially hypokalemia). The introduction of magnesium sulfate in a dose of 2 g (intravenously for 10 minutes) was shown. With the development of complications, immediate synchronized electrical cardioversion is shown. If the patient does not have pulsation on the arteries, then an electric defibrillation should be urgently carried out and a universal algorithm of resuscitation should be adopted.

Tachycardia with a narrow complex of QRS

Variants of tachycardia with a narrow complex of QRS and regular rhythm:

• sinus tachycardia;
• atrial tachycardia;
• atrioventricular tachycardia;
• Atrial flutter with regular atrioventricular conduction (usually 2: 1).

The most frequent causes of tachycardia with a narrow complex of QRS and irregular rhythm are atrial fibrillation or atrial flutter with various atrioventricular conduction.

Tachycardia with narrow QRS and regular rhythm

Sinus tachycardia is the increase in the number of heartbeats that are born in the sinus node. Its cause may be an increase in sympathetic or suppression of parasympathetic influences on the sinus node. It can occur as a normal reaction during physical exertion, as a compensatory reaction for myocardial damage, hypoxic conditions, with hormonal changes (thyrotoxicosis), pain, fever, blood loss, etc.

An electrocardiogram with sinus tachycardia is characterized by a shortening of the RR, PQ, QT interval, enlarged and slightly pointed wave of the RS wave. Sinus tachycardia can occur as paroxysms, but it differs from the paroxysmal tachycardia by gradual (rather than sudden) normalization of the rhythm. Treatment should be directed to the cause that caused this condition (pain relief, lowering of temperature, replenishment of the volume of circulating blood, etc.).

Supraclavicular paroxysmal tachycardia

In clinical practice, often observed supraventricular paroxysmal tachycardia (this group combines atrial and atrioventricular paroxysmal tachycardia).

The heart rate at them is from 140 to 260 per minute. Nadzheludochkovaya tachycardia is less dangerous in terms of ventricular fibrillation compared with ventricular. The form of the ventricular complexes on the electrocardiogram with supraventricular rhythm disturbances differs little from that at normal rhythm. The tooth P, as a rule, is difficult to distinguish. If the ectopic focus is located in the upper parts of the atria, then on the electrocardiogram positive positive deformed teeth P; if the ectopic focus is located in the inferior part of the atria, negative P teeth in II, III and aVF leads are observed. In the case of the origin of paroxysms from the atrioventricular junction, the P teeth on the electrocardiogram are negative, can merge with or remain unchanged with the QRS complex.

Paroxysmal supraventricular tachyarrhythmias, as well as ventricular ones, are subject to relief, especially if they entail disturbances in ventral hemodynamics.

Atrial flutter

When atrial flutter, pulses of the foci of flutter (270-350 per minute) "interrupt" the frequency of generation of sinus pulses (60-100 per minute). Therefore, the sign of trembling is the absence of sinus rhythm (absence of P teeth).

On the electrocardiogram "waves of fluttering" are registered - uniform. Sawtooth (similar to the saw teeth), with a gradual ascent and a sharp drop in low-amplitude (not more than 0.2 mV) teeth. They are best defined in the lead aVF. The frequency of these "waves of flutter" is 9 limits of 250-370 per minute, and the atrioventricular connection is not able to pass to the ventricles all impulses, therefore some part of them is skipped. If atrial flutter occurs at a frequency of 350 per minute, and passes to the ventricles only one in five of the impulses, then a functional atrioventricular blockade of 5: 1 is indicated (ventricular excitation frequency will be 70 per minute, the RR interval is the same).

Since the fluttering impulses get to the ventricles in the usual way (through the conducting system of the ventricles), the form of the QRS ventricular complex is not changed and is not broadened (does not exceed 0.12 s).

Most often observed frequency "waves of flutter", equal to 300 per minute, and a functional blockade of 2: 1. This gives a tachycardia with a frequency of ventricular contractions of 150 per minute. A more frequent rhythm of contractions (170 or more) is not characteristic for atrial flutter with a 2: 1 blockade.

In a number of cases, the functional atrioventricular blockade changes rapidly, becoming then 5: 1, then 4: 1, then 3: 1, etc. In this situation, the waves of atrial flutter will overcome the atrioventricular junction arrhythmically and the interval between the QRS ventricular complexes will be different. This option is called an irregular form of atrial flutter. The combination of atrial flutter with the bundle blockade of the bundle of the Hisnus leads to the appearance of an electrocardiographic pattern that is difficult to differentiate from the ventricular tachycardia.

[1], [2], [3], [4], [5], [6], [7], [8]

Treatment Tachycardia

Treatment of tachycardia with narrow QRS and regular rhythm

If the patient has unstable hemodynamics and progressive deterioration of the condition, then an immediate synchronized electrical cardioversion is shown. While preparations are being made for this procedure, adenosine can be administered intravenously bolus (adenosine is an antiarrhythmic drug that is highly effective in paroxysmal supra-laryngeal tachycardias, and is available as an injection containing 6 mg in 2 ml bottles). Do not delay the conduct of cardioversion, gels after the administration of the drug there is no immediate effect (sinus rhythm is not restored).

If the patient's condition is stable, then therapeutic measures should start reflex action on the vagus nerve (tensing the patient and height of deep inspiration, carotid sinus massage, pressing on the eyeball apples). If tachycardia persists and the diagnosis of atrial flutter is excluded, intravenous bolus administration of 6 mg adenosine is indicated. It is advisable to perform the registration of the electrocardiogram about the time of the drug administration and monitor the changes thereon. If the rhythm of contraction of the ventricles became less frequent for a short time, but then again became more frequent, one should think of atrial flutter or other atrial tachycardia. If the administration did not give an effect at all, then bolus 12 mg adenosine (then once again enter 12 mg if there is no effect). According to the 2010 AHA recommendations, adenosine can now be used for the initial evaluation and treatment of stable-undifferentiated monomorphic tachycardia with regular wide complexes in the presence of a regular heart rhythm. It is important to note that adenosine should not be used for tachycardia with irregular wide complexes, since it can cause ventricular fibrillation.

Successful relief of tachycardia with vagal or adenosine is indicative of its atrial or atrioventricular origin (usually cupping occurs in a matter of seconds). If there are contraindications to adenosine administration or atrial flutter is detected, you should enter:

• verapamil intravenously bolus 2.5-5 mg (for 2 minutes), or
• diltiazem intravenously bolus 15-20 mg (for 2 minutes).

Treatment of tachycardia with narrow QRS and irregular rhythm

Tachycardia with narrow QRS and irregular rhythm is most likely to be due to atrial fibrillation or their flutter with varying degrees of atrioventricular conduction. To identify the rhythm, you need to register an electrocardiogram in 12 leads.

If the patient has unstable hemodynamics and progressive deterioration of the condition, then an immediate synchronized - electrical cardioversion is shown. If the patient's condition is stable, then there are the following options for the therapy:

• medicamentous effect for regulation of heart rate;
• conducting medical (chemical) cardioversion;
• restoration of rhythm electrical cardioversion;
• prevention of complications (anticoagulation therapy, etc.).

The tactics of treatment depend on the duration of atrial fibrillation, as the longer it lasts, the greater the chances of a blood clot in the right atrial cavity. Do not conduct a chemical or electrical cardioversion if atrial fibrillation exists for more than 48 hours, until anticoagulant therapy is performed or the absence of a clot in the right atrial cavity (using trans-esophageal echocardiography) is not proved.

Beta-blockers, cardiac glycosides (digoxin), calcium antagonists (diltiazem), or combinations of these drugs are commonly used to achieve and maintain an acceptable ventricular contraction rate (up to 70-90 bpm)

• Verapamil 5-10 mg (0.075-0.15 mg / kg) intravenously for 2 minutes.
• Diltiazem 20 mg (0.25 mg / kg) intravenously for 2 minutes (continuous infusion - 5-15 mg / h).
• Metoprolol 5.0 mg intravenously for 2-5 minutes (you can enter up to 3 doses of 5.0 mg with an interval of 5 minutes).
• Propranolol 5-10 mg (up to 0.15 mg / kg) intravenously for 5 minutes.
• Esmolol 0.5 mg / kg intravenously for 1 minute (continuous infusion - 0.05-0.2 mg / kg / min).
• Digoxin 0.25-0.5 mg intravenously, then for fast saturation it is possible to administer 0.25 mg intravenously every 4 hours to a total dose of not more than 1.5 mg.
• Cordarone 300 mg intravenously for 10 minutes, then intravenous infusion at a rate of 1 mg / min for 6 hours, then continued infusion at a rate of 0.5 mg / min.
• Calcium antagonists (verapamil, diltiazem) and beta-blockers serve as first-line drugs for an emergency reduction in heart rate. Steady slowing of the frequency of ventricular rhythm with the introduction of digoxin is achieved in 2-4 hours.

With a decrease in contractility of the left ventricle, the reduction in the heart rate is recommended to be performed with cardiac glycosides or cordarone. If the duration of paroxysm of atrial fibrillation is less than 48 hours, cordarone 300 mg (for 10-20 minutes) can be used to stop it, followed by maintenance infusion (900 mg of cordarone for 24 hours).