Heart disease arises from disturbances in myocardial function, coronary perfusion, electrical conduction, and valvular integrity — all rooted in pathophysiologic processes. This book dissects mechanisms behind ischemic heart disease, heart failure, cardiomyopathies, arrhythmias, and valvular disorders with a physiology-first approach. Chapters connect cellular injury, remodeling, neurohormonal activation, and hemodynamic consequences to clinical signs and diagnostic tests. Biomarkers, imaging modalities (echo, CT, MRI), and electrophysiologic techniques are presented with guidance on interpretation and prognostic use. Therapeutic strategy sections translate pathophysiology into medical, device, and surgical interventions, emphasizing personalized care. Suitable for cardiology fellows, internists, and allied health professionals seeking a mechanism-based clinical text.