Table of Contents

Drugs for Cardiovascular System

The cardiovascular system maintains tissue perfusion through a balance between cardiac output, vascular resistance, blood volume, and heart rhythm. Most cardiovascular diseases arise when one or more of these determinants becomes dysregulated.

Pharmacologic therapy therefore targets:

  • Vascular tone
  • Myocardial contractility
  • Blood volume
  • Cardiac conduction
  • Thrombus formation

Understanding where a drug acts within this physiologic framework makes cardiovascular pharmacology logical rather than memorization-based.

I. Antihypertensive Drugs

Reducing Pressure, Protecting Organs

Hypertension is a chronic elevation in arterial pressure that gradually damages blood vessels and target organs such as the brain, heart, and kidneys. Long-term management reduces stroke, myocardial infarction, and renal failure risk.

1. ACE Inhibitors

Examples: Enalapril, Lisinopril, Ramipril

These drugs inhibit the conversion of angiotensin I to angiotensin II. Since angiotensin II is a potent vasoconstrictor and stimulates aldosterone secretion, its inhibition leads to vasodilation and reduced sodium retention.

ACE inhibitors are particularly beneficial in diabetic nephropathy and heart failure because they reduce ventricular remodeling and protect renal function. A persistent dry cough may occur due to bradykinin accumulation.

2. Angiotensin Receptor Blockers (ARBs)

Examples: Losartan, Valsartan, Telmisartan

ARBs block angiotensin II receptors directly. Their clinical effects resemble ACE inhibitors but without causing cough, making them useful alternatives.

3. Beta-Adrenergic Blockers

Examples: Metoprolol, Atenolol, Propranolol, Carvedilol

By blocking β1 receptors in the heart, these drugs reduce heart rate and myocardial contractility, thereby lowering cardiac output and blood pressure.

They are especially useful in hypertensive patients with ischemic heart disease or arrhythmias.

4. Calcium Channel Blockers

Examples: Amlodipine, Nifedipine, Verapamil, Diltiazem

These agents inhibit calcium entry into vascular smooth muscle and cardiac cells. Dihydropyridines (e.g., amlodipine) primarily cause vasodilation, while non-dihydropyridines (verapamil, diltiazem) also reduce heart rate.

5. Diuretics

Examples: Hydrochlorothiazide, Furosemide, Spironolactone

Diuretics promote sodium and water excretion, reducing plasma volume and lowering blood pressure. Thiazides are first-line in uncomplicated hypertension, while loop diuretics are used when fluid overload is present.

II. Antianginal Drugs

Restoring Oxygen Balance

https://my.clevelandclinic.org/-/scassets/images/org/health/articles/16898-coronary-artery-disease
Angina occurs when myocardial oxygen demand exceeds supply, usually due to coronary artery narrowing.

1. Nitrates

Examples: Nitroglycerin, Isosorbide dinitrate

Nitrates release nitric oxide, causing venous dilation. This reduces preload and ventricular wall stress, thereby lowering oxygen demand. Sublingual nitroglycerin provides rapid relief in acute attacks.

2. Beta-Blockers

Examples: Metoprolol, Atenolol

By slowing heart rate and decreasing contractility, these drugs reduce myocardial oxygen consumption. They are effective in chronic stable angina.

3. Calcium Channel Blockers

Examples: Amlodipine, Verapamil

These drugs reduce afterload and improve coronary blood flow. They are particularly useful in variant (Prinzmetal) angina.

III. Drugs Used in Heart Failure

Modifying Disease Progression

 
https://www.researchgate.net/publication/312026317/figure/fig2/AS%3A962699856977990%401606536940929/Schematic-representation-of-the-cardiac-remodeling-process-that-occurs-during-the.gifHeart failure develops when the heart cannot pump sufficient blood to meet metabolic demands. Neurohormonal activation initially compensates but eventually worsens myocardial stress.

1. ACE Inhibitors / ARBs

Examples: Enalapril, Lisinopril, Losartan

These reduce afterload and inhibit remodeling, improving long-term survival.

2. Beta-Blockers

Examples: Carvedilol, Metoprolol succinate

These reduce sympathetic overactivation and improve ventricular function over time.

3. Diuretics

Examples: Furosemide, Spironolactone

They relieve congestion and edema. Spironolactone also reduces mortality in severe heart failure by blocking aldosterone.

4. Cardiac Glycosides

Example: Digoxin

Digoxin increases myocardial contractility by inhibiting the Na⁺/K⁺ ATPase pump, raising intracellular calcium. It is especially useful in heart failure with atrial fibrillation.

IV. Antiarrhythmic Drugs

Stabilizing Electrical Activity

Arrhythmias result from abnormal impulse formation or conduction.

Class I – Sodium Channel Blockers

Examples: Lidocaine, Procainamide

These slow phase 0 depolarization.

Class II – Beta-Blockers

Examples: Metoprolol, Propranolol

Reduce sympathetic stimulation of the heart.

Class III – Potassium Channel Blockers

Examples: Amiodarone, Sotalol

Prolong repolarization and refractory period.

Class IV – Calcium Channel Blockers

Examples: Verapamil, Diltiazem

Slow conduction through AV node.

V. Antithrombotic Drugs

Preventing Clot Formation

Thrombosis can obstruct coronary or cerebral arteries, leading to myocardial infarction or stroke.

Antiplatelet Drugs

Examples: Aspirin, Clopidogrel

Aspirin inhibits COX-1 and prevents thromboxane A₂ formation, reducing platelet aggregation.

Anticoagulants

Examples: Heparin, Warfarin, Apixaban

Heparin enhances antithrombin activity, while warfarin inhibits vitamin K-dependent clotting factors. Direct oral anticoagulants like apixaban inhibit factor Xa.

Integrative Perspective

Cardiovascular drugs are not isolated therapeutic tools. Each class modifies fundamental physiologic variables such as preload, afterload, contractility, conduction, or coagulation. Recognizing these relationships allows a deeper conceptual understanding and supports rational prescribing in clinical practice.