166 articles
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 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.
Hepatopulmonary syndrome
Hepatopulmonary syndrome (HPS): hypoxemia from intrapulmonary vascular dilatations in liver disease or portal hypertension; diagnosed by A-a gradient and contrast echocardiography; cured only by liver transplantation.
Hereditary atrial fibrillation
Hereditary atrial fibrillation, also called familial or early-onset AF, is atrial fibrillation driven by inherited variants, from monogenic KCNQ1, SCN5A, TTN, and LMNA mutations to polygenic risk, with 2023 guideline Class IIb genetic testing for onset before age 45.
Interventricular septum
Interventricular septum (septum interventriculare): the muscular and membranous wall separating the heart's left and right ventricles; carries the bundle of His, supplied mainly by the LAD, and the site of ventricular septal defects.
Isolated pulmonary artery sling
Isolated pulmonary artery sling (isolated anomalous left pulmonary artery, ORPHA 658574): the left pulmonary artery arises from the right and compresses the trachea, without associated cardiac or airway anomalies; treated by reimplantation.
Isolated right ventricular hypoplasia
Isolated right ventricular hypoplasia (IRVH, ORPHA:439, OMIM 277200) is a rare cyanotic congenital heart defect with an underdeveloped right ventricle, normally formed tricuspid and pulmonary valves, and usually a PFO or atrial septal defect causing right-to-left shunt.
James L. Cox
James L. Cox (born 1942) is an American cardiothoracic surgeon, creator of the Cox maze procedure, the first surgical cure for atrial fibrillation, first performed in 1987 at Barnes Hospital, St. Louis; 2020 Jacobson Innovation Award recipient.
Jervell and Lange-Nielsen syndrome
Jervell and Lange-Nielsen syndrome (JLNS), also called surdo-cardiac syndrome, is an autosomal recessive long QT syndrome with congenital deafness, caused by KCNQ1 or KCNE1 mutations, first described in Norway in 1957.
Junctional rhythm
Junctional rhythm: an arrhythmia arising from the AV node or His bundle instead of the SA node, classified by rate (bradycardia 100 bpm), with absent or retrograde P waves and narrow QRS on ECG.
L-type calcium channel
L-type calcium channels (Cav1.1–Cav1.4) are high-voltage-activated, dihydropyridine-sensitive voltage-gated calcium channels in muscle, heart, and neurons; Cav1.2 drives cardiac excitation-contraction coupling, and their blockers treat hypertension and angina.
Laevocardia
Laevocardia (levocardia): cardiac position term for a heart lying in the left hemithorax, counterpart of dextrocardia and mesocardia; used in Van Praagh-style classification of congenital heart disease; distinct from the cockle genus Laevicardium.
Left anterior fascicular block
Left anterior fascicular block (LAFB, left anterior hemiblock) is a conduction delay in the anterior fascicle of the left bundle branch, causing marked left axis deviation on ECG; common in the elderly and a marker of cardiac risk.
Levo-Transposition of the great arteries
Levo-transposition of the great arteries (L-TGA, ccTGA) is a rare congenital heart defect with double discordance leaving the right ventricle systemic; over 80% have associated lesions, and heart block, tricuspid regurgitation, and ventricular failure dominate management.
Ligamentum arteriosum
The ligamentum arteriosum, also called the Ligament of Botallo, is the fibrous remnant of the fetal ductus arteriosus, running from the pulmonary trunk to the aortic arch.
Lown–Ganong–Levine syndrome
Lown–Ganong–Levine (LGL) syndrome, or short PR–normal QRS syndrome, a proposed pre-excitation syndrome described in 1952 with PR under 120 ms, normal QRS, no delta wave, and paroxysmal SVT; now considered an outdated diagnosis.
Maximum heart rate
Maximum heart rate is the highest heart rate a person can reach during maximal exertion, which declines with age and is predicted by formulas like 220 minus age.
Mediastinum
Mediastinum: central thoracic compartment between the pleural sacs, holding the heart, trachea, esophagus, and thymus; divided traditionally into four compartments and, by the ITMIG CT-based standard, into prevascular, visceral, and paravertebral compartments.
Minimaze procedure
The minimaze procedures, also written mini maze, are minimally invasive cardiac operations intended to cure atrial fibrillation, created through small chest incisions without sternotomy or bypass.
Mitral valve
Mitral valve (left atrioventricular valve): the two-leaflet heart valve between left atrium and left ventricle; disorders include prolapse, regurgitation, and stenosis; treated by repair, replacement, or TEER.
Multifocal atrial tachycardia
Multifocal atrial tachycardia (MAT), also called chaotic atrial tachycardia, is an irregular arrhythmia with at least three P-wave morphologies at rates over 100 bpm, seen mostly in elderly COPD patients and treated first by correcting underlying causes.
Myocyte of sinoatrial node
Sinoatrial node myocyte (pacemaker cell, P cell): specialized small cardiac muscle cell of the heart's SAN that spontaneously generates impulses via membrane and calcium clocks, setting heart rate at 60–100 bpm.
Nanoparticle crossing of the placental barrier
Nanoparticle crossing of the placental barrier is the translocation of particles 1–100 nm from maternal circulation into placental tissue or the fetus, with size the key determinant.
Neonatal hypotension
Neonatal hypotension is abnormally low blood pressure in newborns, mainly preterm infants, affecting about 50% of VLBW babies in the NICU; no standard definition exists, and dopamine, dobutamine, and hydrocortisone are main treatments.
Noncardiac influences on heart rate
Noncardiac influences on heart rate are systemic and environmental factors, including body temperature, sleep, posture, altitude, emotion, and caffeine, that change heart rate without any fault in the heart itself.
Palpitations
Palpitations: awareness of an abnormal, rapid, or irregular heartbeat, felt as fluttering or pounding in the chest or neck. A symptom, not a diagnosis; causes include arrhythmias, anxiety, thyroid disease, and drugs; evaluated with 12-lead ECG and ambulatory monitoring.
Paroxysmal supraventricular tachycardia
Paroxysmal supraventricular tachycardia (PSVT) is a regular, rapid heart rhythm of abrupt onset and termination, mostly AVNRT or AVRT; treated acutely with vagal maneuvers and adenosine, and cured by catheter ablation in 94-98% of cases.
Paroxysmal tachycardia
Paroxysmal tachycardia: abnormally rapid heartbeats with sudden onset and cessation (ICD-11 MC81.3, ICD-10 I47). Covers PSVT, mainly AVNRT; treated with vagal maneuvers, adenosine, and newly approved intranasal etripamil.
Patent ductus arteriosus
Patent ductus arteriosus (PDA), persistent ductus arteriosus: a congenital heart defect in which the fetal vessel joining aorta and pulmonary artery stays open after birth. Common in preterm infants; treated with indomethacin, ibuprofen, acetaminophen, or catheter/surgical closure; first surgically repaired by Robert Gross in 1938.