166 articles
Coronary arterial fistula
Coronary arterial fistula, or coronary artery fistula (CAVF/CAF), is an abnormal coronary-to-chamber or coronary-to-vessel connection bypassing the capillary bed; mostly congenital, causing coronary steal, heart failure, endocarditis, treated by follow-up, surgery, or transcatheter closure.
Coronary artery anomaly
Coronary artery anomaly: congenital abnormality of coronary origin, course, termination, or morphology (AAOCA, ALCAPA, fistula, myocardial bridge). Prevalence about 1–2%; interarterial/intramural courses risk sudden cardiac death in young athletes.
Coronary circulation
Coronary circulation: the arteries, capillaries, and veins supplying the myocardium, about 5% of cardiac output, with diastolic-dominant flow, high oxygen extraction, autoregulation, collateral vessels, and microvascular dysfunction assessment.
Coronary ostial stenosis or atresia
Coronary ostial stenosis or atresia (COSA), congenital coronary arterial orifice stenosis or atresia: rare congenital partial or total occlusion of a coronary ostium with proximal hypoplasia, left-sided predominance, ischemia risk, surgical repair.
Coronary sinus
Coronary sinus: the 3-5 cm venous channel in the posterior left atrioventricular groove draining most cardiac venous blood to the right atrium; remnant of the left sinus horn, guarded by the Thebesian valve, key route for pacing leads and ablation.
Coronary sinus atresia
Coronary sinus atresia, or coronary sinus ostial atresia (CSOA), is a rare congenital heart defect in which the coronary sinus ends blindly at the right atrium, draining instead via a persistent left superior vena cava; benign alone but critical in cardiac surgery and CRT lead placement.
Cox maze procedure
Cox maze procedure (Cox-maze IV), a cardiac surgery devised by James L. Cox in 1987 that creates scar lesions in both atria to block atrial fibrillation signals; success 80-90%, gold standard surgical ablation.
Crisscross heart
Crisscross heart (CCH), also called superoinferior ventricles or twisted atrioventricular connections, is a rare congenital malformation with crossed ventricular inflow streams from twisting of the heart about its long axis, prevalence about 1/125,000 live births.
Diad
Diad (cardiac dyad): junction between a cardiomyocyte T-tubule and junctional sarcoplasmic reticulum, about 15 nm cleft, where L-type Ca2+ channels trigger RyR2 calcium-induced calcium release; cardiac counterpart of the skeletal muscle triad.
Diastole
Diastole: the relaxation and filling phase of the cardiac cycle, opposite systole. Covers its four phases, diastolic blood pressure, diastolic dysfunction grading, and the 2025 ASE echocardiography guidelines.
Diving reflex
Diving reflex (mammalian diving response, diving bradycardia): apnea, bradycardia, and peripheral vasoconstriction triggered by facial water immersion, found in all vertebrates studied; human heart rate falls with a 10.4 s time constant, down to 6 beats/min in extremes.
Dofetilide
Dofetilide, sold as Tikosyn, is a Class III antiarrhythmic drug that blocks a cardiac potassium current to convert atrial fibrillation and must be started in hospital under monitoring.
Double aortic arch
Double aortic arch: a congenital heart defect with two aortic arches forming a vascular ring around the trachea and esophagus, causing breathing and swallowing symptoms; treated surgically with excellent outcomes.
Double outlet left ventricle
Double outlet left ventricle (DOLV) is a rare congenital heart defect in which the aorta and pulmonary artery both originate from the morphologic left ventricle, usually with a ventricular septal defect.
Double outlet right ventricle
Double outlet right ventricle (DORV), also called double-outlet right ventricle, is a congenital heart defect where both the aorta and pulmonary artery arise from the right ventricle, usually with a VSD; treated by biventricular repair, single-ventricle palliation, or palliation.
Dronedarone
Dronedarone (Multaq) is a non-iodinated amiodarone analog antiarrhythmic approved in 2009 to reduce AF hospitalization; contraindicated in decompensated heart failure and permanent AF, where it doubles mortality risk.
Drug-induced and toxic bradycardia
Drug-induced and toxic bradycardia is a slow heart rate caused by drugs such as beta-blockers and digoxin, or by conditions like hypothyroidism and hypothermia, and is often reversible.
Ductus venosus
Ductus venosus: fetal vessel connecting the umbilical vein to the inferior vena cava, shunting oxygenated placental blood past the liver; closes after birth to form the ligamentum venosum; key Doppler marker in fetal growth restriction.
Dysphagia lusoria
Dysphagia lusoria (Bayford syndrome) is difficulty swallowing from esophageal compression by an aberrant right subclavian artery, a congenital aortic arch anomaly in 0.5-2.5% of people, mostly asymptomatic.
Ebstein's anomaly
Ebstein malformation of the tricuspid valve (Ebstein anomaly), a rare congenital heart defect with apically displaced tricuspid leaflets and atrialized right ventricle; described by Wilhelm Ebstein in 1866, treated by cone repair.
Ectopia cordis
Ectopia cordis, or ectopic heart, is a rare congenital defect in which the heart lies partly or wholly outside the thorax through an anterior chest wall defect; prevalence 5.5–7.9 per million births, often with pentalogy of Cantrell, survival about 10%.
Electrophysiology study
Electrophysiology study (EP study, invasive cardiac electrophysiology): catheter-based heart test recording electrical activity to locate arrhythmias, test drugs, map before ablation, and assess sudden cardiac death risk; 1-4 hours, mortality about 0.2%.
Endocardium
Endocardium: the endothelial innermost lining of the heart, continuous with vessel intima, with a subendocardium holding Purkinje fibers; embryonically from cardiac crescent mesoderm, it forms valves, septa, and conduction tissue.
Fick principle
The Fick principle states that an organ's blood flow equals its uptake of a substance divided by the difference in concentration between inflow and outflow blood.
Foramen ovale (heart)
Foramen ovale (heart): fetal opening between the right and left atria, also called the oval foramen, shunting blood past the lungs; normally closes at birth, persisting as a patent foramen ovale in about 25% of adults.
Fossa ovalis (heart)
Fossa ovalis: oval depression on the lower interatrial septum of the right atrium, the closed remnant of the fetal foramen ovale; floor is septum primum, rim (limbus) is septum secundum; fusion fails in about 25% of people, leaving a patent foramen ovale.
Frank–Starling law
Frank–Starling law (Starling's law of the heart): intrinsic cardiac mechanism whereby greater ventricular filling (preload) stretches myocardial fibers and increases stroke volume; named for Otto Frank (1895 frog heart) and Ernest Starling (1915 law of the heart).
Heart rate
Heart rate, or pulse, is the number of heartbeats per minute; normal at rest is 60–100 bpm. Set by the sinoatrial node pacemaker and tuned by autonomic, hormonal, and mechanical inputs; measured manually or by wearables and chest straps.
Heart rate across the lifespan
Heart rate across the lifespan describes how heart rate changes with age: about 150 beats per minute in infancy, near 70 in adulthood, with maximum rate declining steadily.
Heart rate monitor
Heart rate monitor: device measuring beats per minute, via chest-strap ECG electrodes or wrist-worn optical PPG in smartwatches and fitness trackers. Chest straps are the validation criterion; wrist accuracy falls as exercise intensity rises.