General principles of rhythm disorder treatment
Pharmacological treatment of arrhythmias does not boil down to simply prescribing pills, but follows a strict hierarchy of therapeutic goals.
First of all, the physician must focus on etiotropic therapy — the treatment of the underlying disease that led to the rhythm disorder. In parallel with this, all provoking factors must be eliminated. Only at the third stage is the prescription of specific anti-arrhythmic drugs justified. If the conservative approach proves ineffective, surgical intervention on the cardiac conduction system is resorted to in certain cases.
Classification of anti-arrhythmic drugs
Anti-arrhythmics are divided into four main classes. This classification is based on the mechanism of their effect on the conduction and action potential parameters of cardiomyocytes.
Class I: Sodium channel blockers
These drugs slow down impulse conduction, which leads to the disruption of the pathological re-entry circuit loop (the so-called re-entry mechanism). They also have a variable effect on the duration of the action potential.
- For supraventricular disorders: quinidine, procainamide, disopyramide, ajmaline. They are predominantly used for atrial fibrillation and frequent extrasystole.
- For ventricular disorders: lidocaine, moracizine (ethmozine). These are the drugs of choice for ventricular tachycardias. The specific feature of lidocaine lies in its high efficacy in patients with myocardial infarction.
Class II: $\beta$-blockers
A typical representative of this group is propranolol. Drugs of this class demonstrate the greatest efficacy in the treatment of atrial (supraventricular) arrhythmias.
Class III: Action potential prolongers
Agents of this group increase the duration of the action potential and the effective refractory period. The main representative is amiodarone. This is a universal drug that is effective in all types of arrhythmias, although in practice the focus is often specifically on atrial disorders.
Class IV: Slow calcium channel blockers
Include verapamil and diltiazem. Like Class III drugs, they are very widely effective, but are mostly used for atrial pathologies.
Non-pharmacological treatment methods
In situations where pharmacotherapy is insufficient or emergency intervention is required, device-based methods are used.
- Management of acute attacks (emergency therapy). Electrical cardioversion or defibrillation is used to eliminate atrial and ventricular fibrillation, as well as paroxysmal tachycardia.
- Treatment of bradyarrhythmias and conduction disorders. With a significant slowing of the rhythm and complete AV block, permanent pacemaker (PM) implantation is indicated. Modern PMs are complex programmable systems capable of pacing two heart chambers and adapting the rhythm rate to physical exertion. Their service life is 7–10 years, and they are widely used in developed countries.
- Prevention of sudden death. Patients from high-risk groups for arrhythmic death receive an implantable cardioverter-defibrillator. The main feature and limiting factor of this method is its high cost.
Resumo: perguntas e respostas sobre o tema
What specific side effects are characteristic of long-term amiodarone administration?
The following side effects are indicated for amiodarone, the risk of which increases with long-term use: pneumonitis, pulmonary fibrosis, keratopathy, and photosensitization. In addition, long-term amiodarone use is listed as a drug-induced cause of hypothyroidism.
What is the classification of anti-arrhythmic drugs that divides them into 4 classes called?
The classification of anti-arrhythmic drugs that divides them into four classes according to their mechanism of action is called the Vaughan Williams classification. In sources, it is indicated as the Vaughan Williams classification, 1970, with additions, as well as the E. Vaughan Williams classification modified by D. Harrison. It is based on clinical use and mechanisms of drug action.
For Class I drugs: "Quinidine and company" work on the atria, while "Lidocaine and ethmozine" rescue the ventricles (especially in infarction).
Questões de aulas e exames
What is the mechanism of action of Class I drugs?
They block sodium channels, slowing down conduction. This disrupts the pathological impulse circulation circuit (re-entry).
Which anti-arrhythmic is considered the most universal?
Amiodarone (a Class III drug). It is effective in all types of rhythm disorders.
In what cases is pacemaker implantation required?
Pacemakers are implanted for bradyarrhythmias, pronounced slowing of the heart rhythm, and complete atrioventricular block.
O que mais estudar sobre o tema
- The mechanism of excitation wave circulation (re-entry)
- Pharmacodynamics of lidocaine in myocardial infarction
- Differences between electrical cardioversion and defibrillation
- Principles of operation of dual-chamber pacemakers
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