Cardiovascular Drugs Our Patients Take
Course Number: 581
Course Contents
Drugs that Regulate Cardiac Rhythm
The heart is both a mechanical and an electrical organ. The electrical component controls the rhythm of the heart. Under the influence of the autonomic nervous system, the sinoatrial (SA) node initiates action potentials, i.e., paces the heart at normal resting rates between 60 and 100 beats per minute.1 Other pacemaker cell are found in the atrioventricular (AV) node, and the ventricular conducting system. Abnormal impulse generation and/or impulse conduction lead to cardiac arrhythmias.6,7
The most common cause of cardiac arrhythmias is chronic coronary artery disease; less commonly, arrhythmias may be related to cardiomyopathies, valvular and congenital heart disease, primary electrophysiological disorders, and genetically determined ion-channel abnormalities.1,7 Drugs in the top 300 that regulate cardiac rhythm (Table 4) include: (1) Na+ channel blockers, (2) β1-adrenoceptor antagonists, (3) K+ channel blockers, (4) Ca2+ channel blockers, and (5) cardiac glycosides.6,7,10
Table 4. Drugs that Affect Cardiac Rhythm and Cardiac Contractility2,6-8,10
Drugs | Mechanisms of Action | Common Indications |
---|---|---|
Class IC antiarrhythmics
| Block voltage-gated Na+ channels in ventricular myocytes | Sustained ventricular tachycardia Paroxysmal supraventricular tachycardia Paroxysmal atrial fibrillation |
Class II antiarrhythmics
| Block β1-adrenoceptors in SA and AV nodal cells | Supraventricular and ventricular arrhythmias precipitated by sympathetic stimulation |
Class III antiarrhythmics
| Block K+ channels and prolong repolarization | Recurrent and unstable ventricular arrhythmias Maintain normal sinus rhythm in patients with symptomatic atrial flutter or atrial fibrillation |
Class IV antiarrhythmics
| Block Ca2+ channels
| Paroxysmal supraventricular tachycardias |
Cardiac glycosides
| Inhibit Na+/K+-ATPase leading to increased Ca2+ concentration in myocytes
Prolong refractory period at AV node
| Systolic heart failure Supraventricular arrhythmias
|