Hemodynamics is the study of blood flow and pressure in the cardiovascular system. It describes how the heart pumps blood through arteries, capillaries, and veins. It is a core physiology concept used in cardiology, critical care, anesthesia, and cardiothoracic surgery. It is commonly applied at the bedside, on echocardiography, and during cardiac catheterization.

Cardiac Index is a hemodynamic measure of blood flow from the heart adjusted for body size. It is calculated as cardiac output divided by body surface area (BSA). It is used in cardiovascular physiology, critical care, and perioperative medicine to describe global circulatory performance. It is most commonly discussed in shock, heart failure, and invasive or noninvasive hemodynamic monitoring.

Endocardial Cushion Defect is a congenital heart defect involving abnormal formation of the atrioventricular (AV) septum and AV valves. It is an anatomic and developmental cardiac condition rather than a diagnostic test or a treatment. It is most commonly discussed in pediatric cardiology, congenital heart disease clinics, and cardiothoracic surgery planning. It is closely related to atrioventricular septal defect (AVSD), including defects of the atrial and/or ventricular septum and AV valve structure.

Pericardial Effusion is an abnormal accumulation of fluid in the pericardial space around the heart. It is an anatomic and pathologic concept that can reflect many underlying diseases. It is commonly identified on transthoracic echocardiography (TTE) and may be supported by computed tomography (CT) or cardiac magnetic resonance (CMR). Its clinical importance ranges from incidental imaging findings to life-threatening cardiac tamponade.

Cardiac Tamponade is a life-threatening form of obstructive shock caused by pressure on the heart from fluid, blood, or air within the pericardial sac. It is a hemodynamic syndrome rather than a single disease, defined by impaired cardiac filling and reduced cardiac output. It sits at the intersection of cardiac anatomy (pericardium) and acute cardiovascular pathology (shock). It is commonly discussed in emergency medicine, cardiology, intensive care, and perioperative cardiothoracic care.

Right Ventricular Hypertrophy is an increase in the muscular thickness (mass) of the right ventricle (RV). It is a structural cardiac finding that reflects chronic pressure overload, volume overload, or both. It is discussed in cardiovascular anatomy and physiology, and in diseases such as pulmonary hypertension and congenital heart disease. It is most commonly recognized through electrocardiography (ECG) patterns and confirmed with cardiac imaging, especially echocardiography.

Left Ventricular Hypertrophy is an increase in the thickness and/or mass of the left ventricle’s myocardium. It is a structural finding in cardiovascular anatomy and cardiac pathophysiology, not a single disease diagnosis. It is commonly discussed when interpreting an electrocardiogram (ECG) and when reviewing echocardiography or cardiac magnetic resonance imaging (cardiac MRI). It often reflects long-standing hemodynamic stress such as hypertension or valvular heart disease.

Cardiomyopathy is a group of diseases of the heart muscle (myocardium) that change cardiac structure and function. It is a clinical diagnosis used in cardiology, emergency care, internal medicine, and critical care. It commonly presents through symptoms of heart failure, arrhythmia, or unexpected cardiac dysfunction on imaging. It is discussed in the context of anatomy, physiology, pathology, diagnosis, and long-term management.

Cardiomegaly means an enlarged heart. It is a descriptive clinical finding used in cardiology and internal medicine. It most commonly appears in imaging reports (especially chest radiography) and is confirmed or characterized with echocardiography. It can reflect normal adaptation, a structural heart disease, or an imaging limitation.

S4 is the fourth heart sound, an extra low-frequency sound heard in late diastole. It reflects atrial contraction against a stiff or noncompliant ventricle. It is a bedside clinical finding in cardiovascular examination (auscultation). It is most commonly discussed in the assessment of hypertension, cardiomyopathy, and diastolic dysfunction.