General principles of arrhythmia management
Pharmacological treatment of arrhythmias is not limited to simply prescribing pills; it follows a strict hierarchy of therapeutic goals.
First and foremost, the physician must focus on etiotropic therapy—treating the underlying disease that led to the rhythm disorder. Concurrently, all provoking factors must be eliminated. Only at the third stage is the prescription of specific antiarrhythmic drugs justified. If a conservative approach proves ineffective, surgical intervention on the cardiac conduction system is performed in select cases.
Classification of antiarrhythmic drugs
Antiarrhythmics are divided into four main classes. This classification is based on their mechanism of action on cardiac conduction and the action potential parameters of cardiomyocytes.
Class I: Sodium channel blockers
These drugs slow down impulse conduction, which breaks the pathological circuit of excitation propagation (the so-called re-entry mechanism). They also have a variable effect on the duration of the action potential.
- For supraventricular arrhythmias: quinidine, procainamide (novocainamide), disopyramide, ajmaline. They are predominantly used for atrial fibrillation and frequent extrasystoles.
- For ventricular arrhythmias: lidocaine, moracizine (ethmozine). These are the drugs of choice for ventricular tachycardias. A specific feature of lidocaine is 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 treating atrial (supraventricular) arrhythmias.
Class III: Action potential prolongers
Agents in this group increase the action potential duration 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 arrhythmias.
Class IV: Non-dihydropyridine calcium channel blockers
Include verapamil and diltiazem. Like Class III drugs, they have a wide spectrum of efficacy, but are used predominantly for atrial pathologies.
Non-pharmacological treatments
In situations where pharmacotherapy is insufficient or emergency intervention is required, device-based techniques are used.
- Termination of acute episodes (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. In cases of significant heart rate slowing and complete AV block, permanent pacemaker (PM) implantation is indicated. Modern pacemakers are complex programmable systems capable of dual-chamber pacing and rate-adaptive response to physical activity. Their lifespan is 7–10 years, and they are widely used in developed countries.
- Prevention of sudden cardiac death. Patients at high risk of arrhythmic death receive an implantable cardioverter-defibrillator (ICD). The main characteristic and limiting factor of this method is its high cost.
Briefly: answers to topical questions
What specific side effects are associated with long-term amiodarone therapy?
The following side effects are associated with amiodarone, with the risk increasing during long-term use: pneumonitis, pulmonary fibrosis, keratopathy, and photosensitivity. Additionally, long-term amiodarone use is cited as a drug-induced cause of hypothyroidism.
What is the name of the classification of antiarrhythmic drugs that divides them into 4 classes?
The classification of antiarrhythmic drugs dividing them into four classes based on their mechanism of action is called the Vaughan Williams classification. Sources refer to it as the Vaughan Williams classification (1970) with updates, as well as the E. Vaughan Williams classification modified by D. Harrison. It is based on the clinical applications and mechanisms of action of the drugs.
For Class I drugs: "Quinidine and company" work on the atria, while "Lidocaine and ethmozine" rescue the ventricles (especially in myocardial infarction).
Class and exam questions
What is the mechanism of action of Class I drugs?
They block sodium channels, slowing conduction. This breaks the pathological impulse re-entry circuit.
Which antiarrhythmic is considered the most universal?
Amiodarone (a Class III drug). It is effective in all types of rhythm disorders.
In which cases is pacemaker implantation required?
Pacemakers are implanted for bradyarrhythmias, marked slowing of the heart rate, and complete atrioventricular block.
What else to study on this topic
- The mechanism of excitation wave circulation (re-entry)
- Pharmacodynamics of lidocaine in myocardial infarction
- Differences between electrical cardioversion and defibrillation
- Principles of dual-chamber pacemaker operation
Master the entire topic in the "Propaedeutics" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Antiarrhythmic drugs" and 3,152 other pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 113 video lessons on the subject
Other topics in the "Cardiovascular system" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.