Human health and medicine

Heart rate response to exercise and training

Heart rate response to exercise and training describes how heart rate rises during exercise, how endurance training lowers resting heart rate, and how quickly heart rate recovers afterward.

Heart rate variability

Heart rate variability (HRV), also called heart period variability, measures beat-to-beat R-R interval variation on the ECG as a non-invasive marker of autonomic nervous system function, analyzed in time and frequency domains (SDNN, RMSSD, LF, HF bands) and applied in cardiology, mental health, and sepsis prediction.

Heart Rhythm

Heart Rhythm: Elsevier monthly journal (ISSN 1547-5271) launched May 2004, official journal of the Heart Rhythm Society and Cardiac Electrophysiology Society, covering cardiac arrhythmias and electrophysiology.

Heart Rhythm Society

Heart Rhythm Society (HRS), formerly NASPE (North American Society of Pacing and Electrophysiology), founded 1979 in Boston; professional society for cardiac pacing and electrophysiology, renamed 2004, 9,700+ members in 93 countries, based in Washington, DC.

HEART score

The HEART score is a bedside risk tool for emergency department chest pain patients, scoring History, ECG, Age, Risk factors, and Troponin to predict major cardiac events within 6 weeks.

Heart sounds

Heart sounds are transient noises from valve closure heard during auscultation. The first two sounds, S1 and S2, are normal, while S3 and S4 are usually abnormal.

Heart transplantation

Heart transplantation: surgical replacement of a failing heart with a donor heart. First done by Barnard in 1967; 1-year survival now near 90%; main risks are rejection, vasculopathy, and immunosuppression side effects.

Heart valve

Heart valve: the four cardiac valves (mitral, tricuspid, aortic, pulmonary), passive pressure-driven leaflet/cusp mechanics, valve disease epidemiology, repair versus replacement, TAVI, and 2024-2025 trial changes.

Heart valve dysplasia

Heart valve dysplasia is a congenital malformation in which one or more heart valves is thickened and malformed, causing regurgitation or stenosis. Includes X-linked FLNA-related cardiac valvular dysplasia and canine tricuspid valve dysplasia.

Oct 20, 2026

Heart Valve Prosthesis Implantation

Heart valve prosthesis implantation replaces diseased native valves with mechanical or bioprosthetic devices, surgically since 1952 and by transcatheter methods (TAVI/TAVR) since the early 2000s, with anticoagulation and durability trade-offs.

Heart–liver transplantation

Heart–liver transplantation is a surgical procedure that replaces both the heart and liver with organs from a single donor, used for combined heart and liver failure and first performed in 1984.

Heart–lung transplantation

Heart–lung transplantation is an operation replacing a patient's heart and both lungs en bloc with donor organs, first done successfully at Stanford in 1981 and now rare, under 50 cases a year worldwide.

Heartburn

Heartburn (pyrosis, acid indigestion): burning chest pain from stomach acid refluxing into the esophagus via a weak lower esophageal sphincter. Over 60 million Americans affected monthly; frequent episodes suggest GERD; treated with antacids, H2 blockers, PPIs.

Heat exhaustion

Heat exhaustion is a heat-related illness from excessive water and salt loss through sweating, causing headache, nausea, dizziness, and heavy sweating; treated with cooling and fluids, it can progress to heat stroke if untreated.

Heat fatigue, transient

Heat fatigue, transient (ICD-11 NF01.3) is a mild acute heat effect: impaired performance of skilled sensorimotor, mental, or vigilance tasks in the heat, greatest in unacclimatized workers, prevented by acclimatization and training.

Heat stroke

Heat stroke is a life-threatening emergency with core temperature above 40 °C (104 °F) and CNS dysfunction, in classic (passive heat exposure) and exertional (exercise) forms; treatment is rapid cold-water immersion, with about 5% case fatality.

Heat syncope

Heat syncope (熱失神) is fainting or dizziness from prolonged standing or sudden standing in heat, caused by reduced cerebral blood flow; a mild, self-limiting heat illness treated with rest, cooling, and oral fluids.

Heather Bresch

Heather Bresch, CEO of Mylan and daughter of Sen. Joe Manchin, led the company through the EpiPen 500% price-increase controversy and a 2007 West Virginia University MBA scandal.

Heavy chain disease

Heavy chain disease (Franklin's disease, gamma-HCD) is a rare B-cell disorder producing truncated immunoglobulin heavy chains without light chains; alpha, gamma, and mu types exist, alpha being most common and antibiotic-responsive early.

Heavy ion radiotherapy

Heavy ion radiotherapy, also known as carbon ion radiotherapy, is a radiation therapy technique using accelerated carbon ions to treat tumors, with sharp dose localization and elevated biological effectiveness.

Heavy menstrual bleeding

Heavy menstrual bleeding (HMB, formerly menorrhagia) is excessive menstrual blood loss interfering with quality of life, affecting 20-50% of reproductive-age women. Causes include fibroids, bleeding disorders; LNG-IUS is the best first-line treatment.

Hebbian theory

Hebbian theory, also called Hebbian learning or Hebb's rule, is the principle from Donald Hebb's 1949 book The Organization of Behavior that synapses strengthen when neurons repeatedly fire together.

Hebei Medical University

Hebei Medical University is a provincial public medical university in Shijiazhuang, Hebei, China, tracing its origin to an 1894 school founded by Li Hongzhang, the first government-run Western medicine school in modern China.

Heberbiovac HB

Heberbiovac HB: Cuban recombinant hepatitis B vaccine by CIGB, HBsAg in Pichia pastoris, licensed 1990, WHO prequalified 2001, used in over 30 countries.

HEC88473

HEC88473 (APL-18881) is Sunshine Lake Pharma's investigational long-acting GLP-1/FGF21 dual-receptor agonist Fc fusion protein injection for type 2 diabetes, obesity, and MASH; first such dual agonist in clinical stage, licensed to Apollo Therapeutics.

Heiner syndrome

Heiner syndrome, or cow's milk-induced pulmonary hypersensitivity, is a rare non-IgE milk allergy of infants causing pulmonary hemosiderosis, anemia, and failure to thrive, resolving on a milk-free diet.

Heinz body

Heinz bodies (Heinz-Ehrlich bodies): clumps of denatured, precipitated hemoglobin inside red blood cells, seen with supravital stains; caused by oxidant drugs, toxins, G6PD deficiency, unstable hemoglobins, and thalassemia, and producing bite cells and hemolytic anemia.

Helen B. Taussig

Helen Brooke Taussig (1898-1986), American physician at Johns Hopkins, founder of pediatric cardiology, co-developer of the Blalock-Taussig blue baby operation (1944), Lasker Award and Medal of Freedom recipient, first woman president of the American Heart Association.

Helen Burstin

Helen Burstin is an American physician and health services researcher who serves as Chief Executive Officer of the Council of Medical Specialty Societies and is a member of the National Academy of Medicine.