Pharmacotherapy of Heart Failure

Pharmacotherapy of Heart Failure

1. Definition & overview

• Heart failure (HF) is a clinical syndrome (not a single disease) — the heart cannot pump blood at a rate commensurate with the metabolic requirements of the tissues, or can do so only at elevated filling pressure (G&G 14e Ch.33, pp.647–8; KDT 8e Ch.38, p.561).
  • DiPiro's contemporary definition adds a biomarker/objective anchor: symptoms/signs from abnormalities in cardiac structure and/or function, substantiated by raised natriuretic-peptide concentrations or objective evidence of pulmonary/systemic congestion of cardiogenic origin (DiPiro 12e Ch.36, p.199).
  • It is the final common pathway of multiple cardiac diseases — ischaemic heart disease (commonest), chronic hypertension, valvular disease, dilated/hypertrophic cardiomyopathies, viral myocarditis (CMV, parvovirus, HIV), and cardiotoxins (alcohol, cocaine, amphetamines, doxorubicin, trastuzumab [anti–Her-2/Erb-B2], immune-checkpoint inhibitors) (G&G 14e Ch.33, p.647).
• Two haemodynamic syndromes within HF (G&G 14e Ch.33, p.647; KDT 8e Ch.38, p.561):
  • Forward (low-output) failure → fatigue, dizziness, muscle weakness, exertional dyspnoea.
  • Backward (congestive) failure → raised upstream filling pressure → peripheral/pulmonary oedema, hepatic congestion, ascites.
• Coronary artery disease is the single commonest cause of HFrEF (up to ~75% of cases); MI causes loss of viable myocardium, triggering compensatory remodelling of surviving muscle (DiPiro 12e Ch.36, p.201).
• HF is among the few cardiovascular conditions rising in prevalence — better treatment of MI/HTN lets more patients survive to develop HF; ageing population; "westernised" lifestyle (G&G 14e Ch.33, p.647; Katzung 16e Ch.13, p.219).
• Prognosis is grim: conventional ~50% 5-year mortality (Katzung); DiPiro cites ~42% overall 5-year survival, with ~40% of deaths sudden (ventricular arrhythmia) (Katzung 16e Ch.13, p.219; DiPiro 12e Ch.36, p.200).
• Median survival after first HF hospitalisation is worse than most cancers, though it improved over 30 years — tracking a 2–3-fold rise in prescription of ACEIs/ARBs, β blockers and MRAs (i.e. drug therapy drives survival) (G&G 14e Ch.33, p.647).
• "High-output" failure is a rare distinct entity (hyperthyroidism, beriberi, anaemia, arteriovenous shunts) — responds poorly to standard HF drugs; treat the underlying cause (Katzung 16e Ch.13, p.222).