Antidysrhythmic Drugs and Drugs for Angina Pectoris

Vocabulary practice flashcards covering Vaughan Williams antidysrhythmic classes, common cardiac dysrhythmias, and pharmacological treatments for angina pectoris.

Dysrhythmia

An abnormality in the rhythm of the heartbeat (also known as arrhythmia) arising from disturbances in electrical impulse formation or impulse conduction.

Prodysrhythmic Effect

The characteristic adverse property whereby virtually all drugs that treat dysrhythmias can worsen existing dysrhythmias or generate new ones.

Atrial Fibrillation

A common supraventricular dysrhythmia characterized by chaotic, disorganized atrial activity, lack of distinct P waves, an irregular ventricular response, and risk of thromboembolism.

Atrial Flutter

A supraventricular tachydysrhythmia arising above the ventricles characterized on ECG by rapid, regular atrial waves that exhibit a classic sawtooth pattern.

Supraventricular Tachycardia (SVT)

A fast heart rhythm originating above the ventricles that can occur as paroxysmal or sustained episodes, driving the ventricles at an excessive rate.

Torsades de Pointes

A polymorphic ventricular tachycardia characterized by QRS complexes whose polarity and amplitude twist around the isoelectric baseline like a party streamer, typically precipitated by drugs that prolong the QT interval.

Sustained Ventricular Tachycardia

A life-threatening ventricular dysrhythmia originating below the AV node that persists at a rapid rate, significantly impairing cardiac output and requiring acute termination.

Premature Ventricular Complex (PVC)

An ectopic ventricular impulse occurring earlier than the next expected beat, recognized on ECG as a wide, bizarre QRS complex not preceded by a P wave.

Ventricular Fibrillation

A lethal, uncoordinated quivering of the ventricles with no organized electrical complexes, resulting in immediate loss of cardiac output and cardiac arrest.

Vaughan Williams Classification

The standard classification system for antidysrhythmic drugs categorizing agents into Class I (sodium channel blockers), Class II (beta blockers), Class III (potassium channel blockers), and Class IV (calcium channel blockers).

Quinidine

A Class IA sodium channel blocker that slows conduction, delays repolarization, widens the QRS complex, and prolongs the QT interval; used for supraventricular and ventricular dysrhythmias and interacts significantly with digoxin.

Lidocaine [Xylocaine]

A Class IB sodium channel blocker used exclusively for ventricular dysrhythmias that accelerates repolarization and reduces automaticity in the ventricles and His-Purkinje system without major ECG changes.

Phenytoin

An antiseizure agent categorized as a Class IB antidysrhythmic used specifically to manage digoxin-induced dysrhythmias; requires regular monitoring of serum levels, liver function, and renal function.

Propranolol [Inderal]

A nonselective Class II beta-adrenergic blocker that decreases SA node automaticity, slows AV conduction velocity, and reduces myocardial contractility; adverse effects include AV block, sinus arrest, hypotension, and bronchospasm.

Amiodarone [Cordarone, Pacerone]

A Class III potassium channel blocker approved for life-threatening ventricular dysrhythmias that features an exceptionally long half-life ($\text{weeks to months}$), widens the QRS complex, and prolongs PR and QT intervals.

Sotalol [Betapace]

An antidysrhythmic agent combining Class II (beta-adrenergic blockade) and Class III (potassium channel blockade) properties that delays repolarization and requires hospital admission for loading therapy due to dysrhythmia risks.

Dofetilide [Tikosyn]

An oral Class III potassium channel blocker used for atrial dysrhythmias that carries a high risk of inducing torsades de pointes, mandating a $3\text{-day}$ inpatient hospital stay during therapy initiation.

Class IV Antidysrhythmics

Calcium channel blockers, primarily verapamil and diltiazem, that decrease SA nodal automaticity, delay AV conduction, and slow ventricular rates in atrial fibrillation or flutter.

Adenosine [Adenocard]

An ultra-short-acting antidysrhythmic agent ($\text{half-life} < 10\,\text{s}$) administered as a rapid IV bolus to terminate paroxysmal SVT by decreasing SA automaticity and abruptly slowing AV conduction, typically producing transient asystole.

Digoxin [Lanoxin]

A cardiac inotrope that treats supraventricular dysrhythmias by decreasing AV conduction and SA node automaticity; toxicity is significantly exacerbated by hypokalemia ($\text{K}^+ < 4\,\text{mEq/L}$).

Angina Pectoris

Substernal chest pain, pressure, or discomfort often radiating to the left arm and shoulder, occurring when myocardial oxygen demand exceeds oxygen supply.

Chronic Stable Angina

Exertional chest pain caused by coronary artery disease (CAD) that is reliably triggered by physical exertion, large meals, cold exposure, or emotional stress, and relieved by rest or nitroglycerin.

Prinzmetal's Angina (Variant Angina)

Chest discomfort caused by coronary artery vasospasm rather than exertion, occurring unpredictably at rest, at night, or in early morning; treated with calcium channel blockers and organic nitrates.

Unstable Angina

A medical emergency characterized by angina at rest, new-onset exertional angina, or intensification of existing pain, caused by severe CAD complicated by acute plaque rupture and thrombosis.

Nitroglycerin

An organic nitrate that directly relaxes vascular smooth muscle, predominantly dilating veins to reduce cardiac preload and dilating coronary arteries to relieve vasospasm and improve myocardial oxygen supply.

Nitrate Tolerance

A rapid attenuation of antianginal and hemodynamic efficacy resulting from continuous exposure to nitrates, prevented by providing a daily drug-free interval of at least $8\,\text{hours}$.

PDE-5 Inhibitor and Nitrate Contraindication

The strictly prohibited concurrent administration of nitrates with PDE-5 inhibitors (e.g., sildenafil, tadalafil) because excessive cGMP-mediated vasodilation can cause fatal hypotension.

Ranolazine

A newer antianginal drug indicated for chronic stable angina that can be combined with beta blockers, nitrates, or calcium channel blockers to reduce anginal episodes.