Chapter 25: Heart Failure Drugs – Mechanisms & Treatments

HF occurs due to various cardiac disorders, including myocardial deficiencies or external factors that overload the heart, necessitating a systematic approach to treatment. Modern Canadian guidelines prioritize pharmacotherapy that aims to delay or reverse adverse ventricular remodeling, focusing initially on angiotensin-converting enzyme (ACE) inhibitors (e.g., lisinopril) or angiotensin II receptor blockers (ARBs, e.g., valsartan), and specific beta blockers (e.g., metoprolol or carvedilol). The therapeutic standard for heart failure with reduced ejection fraction (HFrEF) now also includes mineralocorticoid receptor antagonists and sodium glucose transport 2 (SGLT2) inhibitors. The drugs are discussed based on their influence on myocardial mechanics, specifically their inotropic (force of contraction), chronotropic (heart rate), and dromotropic (electrical conduction) effects. Cardiac glycosides, such as digoxin, which was once the standard therapy, are now reserved for use as adjuncts in symptomatic patients, providing a positive inotropic effect but carrying a risk of toxicity due which requires close monitoring of serum electrolyte levels (e.g., potassium and magnesium) and observation for adverse effects like visual changes. For the short-term treatment of acute heart failure in critical care settings, phosphodiesterase inhibitors (PDIs), or inodilators like milrinone, are used to increase contractility and cause vasodilation, though they require careful monitoring for ventricular dysrhythmias. Specialized medications such as the SA node modulator ivabradine and the combination product hydralazine/isosorbide dinitrate are also reviewed. Comprehensive nursing care, which is vital for patient safety and adherence, involves thorough assessment of cardiac parameters, including measuring the apical pulse rate for one full minute before administering drugs like digoxin, continuous monitoring for drug interactions, and strict adherence to safe dosage calculation practices, particularly concerning decimal point placement.