Daily Archive 10.02.2019

The strategy of “frequency control” in the treatment of atrial fibrillation

A number of drugs slow down AV conduction (the so-called negative dromotropic effect) and thereby reduce heart rate with persistent AF.

1. Calcium channel blockers in atrial fibrillation Intravenous verapamil quickly and effectively suppresses AV conduction, and thus within a few minutes helps to reduce the frequency of ventricular contractions against the background of persistent AF. At the same time, however, it is unlikely that the sinus rhythm will be restored. In fact, there is good reason to believe that verapamil may contribute to the persistence of arrhythmias. Ingestion of verapamil (120-240 mg / day) usually also allows for effective control of the frequency of ventricular contractions in the background of AF both at rest and during exercise. Diltiazem (but not dihydropyridine calcium channel blockers nifedipine and amlodipine) has a verapamil-like effect. Inside the drug is prescribed in a long-acting dosage form at a dose of 200-300 mg / day. Patients with heart failure are advised to avoid prescribing these drugs or use them with caution.

2. Beta-blockers in atrial fibrillation BAB have an effect similar to that of calcium channel blockers.

3. Digoxin in atrial fibrillation The administration of digoxin orally is widely used to control the frequency of ventricular contractions in the background of atrial fibrillation (AF). Its advantages are the long duration of action and the presence of a positive inotropic effect. However, digoxin often does not allow for adequate control of heart rate at rest and rarely provides rhythm control during physical activity, despite adequate plasma concentration. Side effects are often observed. Old age, renal or electrolyte disorders, the appointment of other drugs can contribute to the development of digitalis intoxication in patients taking the drug in an adequate therapeutic dose. Intravenous administration of digoxin is usually ineffective in rapidly reducing the frequency of ventricular contractions during atrial fibrillation (AF). As indicated below, digoxin does not allow to stop or prevent AF. Due to the many restrictions on the use of the drug and the possibility of reducing the frequency of ventricular contractions with AF, using calcium channel blockers or BAB, digoxin may no longer be used for this purpose.

4. Assessment of the adequacy of rhythm frequency control It is important to remember that although monitoring the frequency of ventricular contractions may seem satisfactory at rest, it is often possible to inadequately increase the heart rate during exercise. To ensure that adequate heart rate control is achieved against the background of FP, outpatient ECG monitoring should ideally be used. Standard, although arbitrarily chosen values, indicating effective control of heart rate, are 60-80 beats / min at rest and 90-115 beats / min during moderate exercise. A “soft frequency control” strategy, aimed at maintaining the ventricular rate at less than 110 beats / min at rest, has recently been compared with the standard “strict frequency control” strategy. It was shown that the first of the mentioned strategies is not inferior to the latter. Although asymptomatic patients “mild frequency control” may be considered acceptable, in patients with severe symptoms (such as shortness of breath and palpitations), as well as in individuals with significantly reduced ventricular pumping function, it is important to achieve good control over the frequency of their contractions.

5. High and low frequency of ventricular contractions during atrial fibrillation Some patients with atrial fibrillation (AF) have both very high and low frequency of ventricular contractions during daytime (with AF, a low frequency during sleep is considered normal). In some cases, to suppress high frequencies with the help of drugs that block AV-conduction, the ventricular ECM may be required. In some patients with atrial fibrillation (AF), probably due to impaired AV conduction, there is no adequate increase in heart rate in response to exercise (chronotropic insufficiency). To improve tolerance to a physical load will allow EX- with function of frequency adaptation.

6. Heart failure in atrial fibrillation. Particular attention should be given to patients with heart failure and atrial fibrillation (AF). Persistently high frequency of ventricular contractions may worsen the course of heart failure or be its true cause. As mentioned above, in some patients, due to a violation of AV conduction (both spontaneous and medically caused by drugs, such as BAB), chronotropic insufficiency can be observed. Therefore, it is important to ensure that the patient’s tolerance to physical exertion is not limited by the inability of the heart to adequately increase heart rate during its implementation.