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Capillary malformations
Capillary malformations (port-wine stains, nevus flammeus) are congenital low-flow malformations of dilated capillaries and postcapillary venules, appearing as pink to purple birthmarks, sometimes with Sturge-Weber or Klippel-Trenaunay syndrome, treated mainly with pulsed dye laser.
Capillary Permeability
Capillary permeability (microvascular or vascular permeability) is the selective exchange of substances across capillary endothelium via transcellular and paracellular routes, governed by the glycocalyx and the revised Starling principle, and raised in inflammation and capillary leak syndrome.
Capillary refill
Capillary refill (CRT) is the bedside test timing skin color return after blanching pressure, used to assess peripheral perfusion and shock; normal under 2 seconds conventionally, varies with age, sex, and temperature, and guides sepsis resuscitation.
Capillary-lymphatic malformation
Capillary-lymphatic malformation (CLM) is a combined slow-flow vascular malformation mixing capillary and lymphatic vessels, classified by ISSVA among combined malformations, occurring isolated or in syndromes such as Klippel-Trenaunay and CLOVES.
Capillary-lymphatic-venous malformation
Capillary-lymphatic-venous malformation (CLVM) is a slow-flow combined vascular malformation of capillaries, lymphatics, and veins in the ISSVA classification; with hypertrophy it is Klippel-Trenaunay syndrome, linked to PIK3CA overgrowth spectra.
Capillary-venous malformation
Capillary-venous malformation (CVM, ORPHA:717611) is a slow-flow combined vascular malformation of capillary plus venous components in one lesion, distinct from CM+VM syndromes like Klippel-Trenaunay.
Carboxyhemoglobin
Carboxyhemoglobin (COHb) is hemoglobin bound to carbon monoxide, which binds about 240 times more strongly than oxygen. Normal under 3% in nonsmokers, under 10% in smokers; measured by CO-oximetry, not standard pulse oximetry.
Carcinoma in situ of the conjunctiva
Carcinoma in situ of the conjunctiva (conjunctival squamous cell carcinoma in situ, CIN III/CIS, ICD-11 2E6A.0) is a preinvasive, full-thickness conjunctival epithelial dysplasia with intact basement membrane, treated by excision with cryotherapy or topical chemotherapy.
Cardiac allograft vasculopathy
Cardiac allograft vasculopathy (CAV), also called transplant coronary artery disease, is accelerated diffuse coronary disease of the transplanted heart; it affects about 8% of recipients at 1 year and 47% at 10 years and is a leading cause of late graft failure.
Cardiac arrest
Cardiac arrest: abrupt loss of heart function from an electrical malfunction, distinct from a heart attack; about 350,000 U.S. out-of-hospital cases yearly, roughly 10.5% survival, treated with CPR and defibrillation.
Cardiac Arrhythmia Suppression Trial
Cardiac Arrhythmia Suppression Trial (CAST): NHLBI placebo-controlled trial of encainide, flecainide, and moricizine for post-MI ventricular ectopy; drugs suppressed PVCs but increased mortality, halting the trial in 1989 and 1991.
Cardiac catheterization
Cardiac catheterization (heart cath) is an invasive procedure threading a catheter from the arm, groin, or neck to the heart to measure pressures, image coronary arteries, and deliver treatments like angioplasty; over 1 million are done yearly in the US, and its pioneers won the 1956 Nobel Prize.
Cardiac conduction
Cardiac conduction is the heart's electrical conduction system: sinoatrial and atrioventricular nodes, His bundle, bundle branches, and Purkinje fibers, which initiate and coordinate roughly 3 billion heartbeats over a lifetime.
Cardiac conduction system
Cardiac conduction system: the sinoatrial node, atrioventricular node, bundle of His, bundle branches, and Purkinje fibers that initiate and spread the heartbeat; discovered in reverse order (Purkinje 1839 to sinus node 1907) and now targeted by conduction system pacing.
Cardiac contractility modulation
Cardiac contractility modulation (CCM), Optimizer Smart device, is a heart failure device therapy delivering non-excitatory high-voltage impulses during the cardiac refractory period to improve contractility in symptomatic HFrEF patients with narrow QRS ineligible for CRT.
Cardiac cycle
Cardiac cycle: the sequence of atrial and ventricular contraction and relaxation from one heartbeat to the next, divided by valve events into systole and diastole, with phases, pressures, volumes, ECG timing, heart sounds, and the Wiggers diagram.
Cardiac excitation-contraction coupling
Cardiac excitation-contraction coupling (EC coupling) links cardiomyocyte depolarization to contraction via calcium-induced calcium release: L-type Ca²⁺ entry triggers RyR2 SR release at dyads, then SERCA2a and NCX remove Ca²⁺ for relaxation.
Cardiac imaging and diagnostics
Cardiac imaging and diagnostics is the set of tests that produce pictures or functional measurements of the heart, including echocardiography, cardiac MRI, nuclear perfusion imaging, and coronary CT angiography.
Cardiac marker
Cardiac marker (cardiac biomarker): blood substance released when the heart is damaged, measured by immunoassay. Cardiac troponin I/T is the preferred marker for myocardial infarction; high-sensitivity troponin assays enable 1–2 hour rule-out, replacing AST, LDH, CK, and CK-MB.
Cardiac muscle
Cardiac muscle (heart muscle, myocardium): striated, involuntary, autorhythmic muscle of the heart walls; branched mononuclear cardiomyocytes joined by intercalated discs, contracting via calcium-induced calcium release through RyR2, SERCA, and NCX.
Cardiac output
Cardiac output (CO) is the blood volume the heart pumps per minute, CO = heart rate × stroke volume. Measured by Fick principle, thermodilution via pulmonary artery catheter, and Doppler, pulse contour, and bioimpedance monitors judged against a ±30% percentage error criterion.
Cardiac pacemaker
Cardiac pacemaker: the sinoatrial node, the heart's natural pacemaker in the right atrium firing at 60–100 bpm, and implanted artificial pacemakers treating bradycardia, including leadless versus transvenous devices.
Cardiac PET
Cardiac PET: positron emission tomography of the heart using tracers such as rubidium-82, nitrogen-13 ammonia, and 15O-water for myocardial perfusion imaging, blood flow quantification, viability, and inflammation, preferred over SPECT for diagnostic accuracy.
Cardiac physiology
Cardiac physiology is the study of how the heart generates and regulates blood flow, spanning electrical and calcium signals, cardiac muscle mechanics, and measurement of cardiac output.
Cardiac plexus
Cardiac plexus: autonomic nerve network at the heart's base where sympathetic cardiac nerves and vagal branches converge into superficial and deep portions, first described by Falloppia in 1561, distributing innervation to atria, ventricles, and intrinsic cardiac ganglia.
Cardiac skeleton
The cardiac skeleton, or fibrous skeleton of the heart, is a framework of dense connective tissue between the atria and ventricles that anchors the four cardiac valves.
Cardiac stress test
A cardiac stress test measures how the heart performs under increased workload, usually treadmill exercise with ECG monitoring, to detect coronary artery disease; drugs replace exercise when patients cannot walk sufficiently.
Cardiac work, energetics and reserve
Cardiac work, energetics and reserve: how the heart converts oxygen into pumping work, measured via pressure-volume loops, PVA, Emax, efficiency, and coronary flow reserve.
Cardiomyopathy
Cardiomyopathy, heart muscle disease, includes dilated, hypertrophic, restrictive, arrhythmogenic, takotsubo, and peripartum types; causes heart failure and arrhythmias; diagnosed mainly by echocardiography.
Cardioplegia
Cardioplegia: drug-induced, reversible cardiac arrest during cardiac surgery using high-potassium solutions (St. Thomas, blood 4:1, del Nido, HTK), delivered ante- or retrograde for myocardial protection.