RDCS Pediatric cheat sheet

Wavelength (mm) = 1.54 ÷ transducer frequency (MHz); higher frequency improves axial resolution but reduces penetration, so pediatric imaging commonly uses 5–12 MHz.

Axial resolution (mm) = spatial pulse length ÷ 2 = (0.77 × cycles per pulse) ÷ frequency (MHz); fewer cycles and higher frequency give finer axial resolution.

Speed of sound is 1540 m/s in soft tissue, about 1570 m/s in blood, and about 4080 m/s in bone; all range assignment assumes 1540 m/s.

Doppler equation: Δf = (2 × f0 × v × cos θ) ÷ c; at an angle of 20° or less the cosine is ≥0.94 and velocity error is under 6%.

Nyquist limit = PRF ÷ 2; aliasing is corrected by raising the scale or PRF, shifting the baseline, lowering transducer frequency, or switching to continuous wave Doppler.

Mechanical index = peak negative pressure (MPa) ÷ square root of frequency (MHz); FDA limits are MI ≤ 1.9 and TI ≤ 6 for cardiac imaging, with ophthalmic limits MI ≤ 0.23 and TI ≤ 1.0.

Thermal index reflects heating and rises with acoustic power, long spectral Doppler dwell times, and color Doppler; exposure time is kept at the minimum consistent with a diagnostic study (ALARA).

Frame rate = PRF ÷ lines per frame; frame rate falls as depth, sector width, line density, or color box size increases, reducing temporal resolution.

Tissue harmonics transmit at f0 and receive at 2f0, sharpening endocardial borders and reducing side-lobe artifact; variance color maps display turbulence rather than mean velocity.

Fetal circulation uses three shunts: ductus venosus, foramen ovale, and ductus arteriosus; the foramen ovale directs oxygenated umbilical venous blood from right to left atrium.

The ductus arteriosus constricts functionally within 24–48 hours of birth and closes anatomically by 2–3 weeks; prostaglandin E1 keeps it patent in ductal-dependent lesions.

The tricuspid valve inserts 2–8 mm more apically than the mitral valve in children; greater apical displacement (≥8 mm/m²) suggests Ebstein anomaly.

Right ventricle landmarks: anterior position, moderator band, three leaflets, septal papillary attachments; left ventricle: posterior position, smooth septum, two leaflets.

Cardiac output = heart rate × stroke volume; stroke volume = outflow tract cross-sectional area × velocity-time integral; cardiac index = cardiac output ÷ body surface area.

Pulmonary vascular resistance falls rapidly after birth and approaches adult levels by 6–8 weeks, which sets the timing of symptoms from a left-to-right shunt.

Normal pediatric left ventricular ejection fraction is about 55–75% and fractional shortening about 28–44%; both are age- and load-dependent.

Coronary arteries arise from the facing aortic sinuses: left main (LAD and circumflex) from the left sinus, right coronary from the right sinus; ALCAPA is anomalous origin of the left coronary artery from the pulmonary artery.

In early neonatal life immature relaxation makes the mitral E wave smaller than the A wave; E/A exceeds 1 by early infancy in most children.

Ventricular septal defect is the most common congenital heart lesion; perimembranous defects predominate, and restrictive defects give high-velocity jets with normal ventricular pressures.

Qp/Qs = (RVOT area × RVOT VTI) ÷ (LVOT area × LVOT VTI); a ratio above 1.5 indicates a significant shunt, and above 2.0 usually prompts closure.

Secundum atrial septal defect is the most common ASD; sinus venosus defects accompany anomalous pulmonary veins, and primum defects accompany a cleft mitral valve.

Tetralogy of Fallot = VSD + overriding aorta + right ventricular outflow obstruction + right ventricular hypertrophy; the degree of outflow obstruction determines cyanosis.

D-transposition of the great arteries produces parallel great vessels; prostaglandin E1 and balloon atrial septostomy maintain mixing until the arterial switch operation.

Hypoplastic left heart syndrome is palliated in stages: Norwood stage I with a systemic-to-pulmonary shunt, bidirectional Glenn, then Fontan; later stages rely on passive pulmonary blood flow.

Coarctation shows discrete narrowing distal to the left subclavian artery with holodiastolic runoff and a sawtooth continuous Doppler signal; a bicuspid aortic valve coexists in most patients.

Ebstein anomaly = apical displacement of tricuspid leaflets, atrialized right ventricle, and tricuspid regurgitation; Wolff-Parkinson-White syndrome occurs in 10–30%.

Patent ductus arteriosus shows continuous flow with peak velocity at the pulmonary end; indomethacin or ibuprofen closes it, while a ductal-dependent lesion requires prostaglandin E1.

Kawasaki disease: coronary internal diameter Z-score ≥2.5 is abnormal and ≥10 is a giant aneurysm; IVIG plus aspirin within 10 days reduces aneurysm formation.

Acute rheumatic fever most often causes mitral regurgitation; Jones criteria require streptococcal evidence plus two major, or one major and two minor, manifestations.

Cardiac tamponade: pericardial effusion with right atrial systolic and right ventricular diastolic collapse, a plethoric inferior vena cava, and >25% respiratory variation in mitral inflow.

Myocarditis from Coxsackie B, parvovirus, or adenovirus shows global hypokinesis, reduced ejection fraction, and elevated troponin; function may recover over weeks to months.

Right ventricular systolic pressure = 4 × (tricuspid regurgitation velocity)² + right atrial pressure; a TR velocity above 2.8 m/s suggests elevated pulmonary pressure.

Cardiac rhabdomyoma is the most common pediatric cardiac tumor and is associated with tuberous sclerosis; fibroma, myxoma, and teratoma are less common.

Infective endocarditis vegetations favor valve surfaces and prosthetic material; the modified Duke criteria combine blood culture and echocardiographic findings.

MIS-C after SARS-CoV-2 infection can produce coronary dilation, depressed ventricular function, and pericardial effusion, mimicking Kawasaki disease.

Ejection fraction = (end-diastolic volume − end-systolic volume) ÷ end-diastolic volume; Simpson's biplane method of disks is the preferred two-dimensional technique.

Fractional shortening = (LVIDd − LVIDs) ÷ LVIDd; normal pediatric values are about 28–44%, and the measurement assumes uniform regional function.

Tei (myocardial performance) index = (isovolumic contraction time + isovolumic relaxation time) ÷ ejection time; normal is roughly 0.35–0.45.

Global longitudinal strain by speckle tracking normally averages about −18% to −22% and detects subclinical dysfunction before ejection fraction falls.

Hypertrophic cardiomyopathy: asymmetric septal hypertrophy, systolic anterior motion of the mitral valve, late-peaking dagger-shaped LVOT Doppler, and dynamic obstruction.

Restrictive cardiomyopathy: biatrial enlargement with normal or near-normal ejection fraction, E/A > 2, short deceleration time, and small ventricular volumes.

Dilated cardiomyopathy: increased left ventricular dimensions with reduced ejection fraction and eccentric hypertrophy; spontaneous echo contrast or apical thrombus may appear.

Left ventricular noncompaction is diagnosed when the noncompacted-to-compacted layer ratio exceeds 2.3 at end-systole, with deep intertrabecular recesses perfused from the cavity.

Diastolic assessment combines mitral E/A ratio, tissue Doppler e′, E/e′ ratio, and left atrial volume index; normal values are age-dependent in children.

Image in a cephalad-to-caudal sequence: subcostal, apical, parasternal, then suprasternal; the subcostal window gives the best images in infants because the liver is an acoustic window.

The suprasternal notch view shows the aortic arch and its branches in a candy-cane orientation and is used to evaluate coarctation and patent ductus arteriosus.

Pediatric measurements are indexed to body surface area as Z-scores; a Z-score above +2 or below −2 defines dilation or hypoplasia for that structure.

Routine antibiotic prophylaxis is not required for echocardiography; it is reserved for specific high-risk prosthetic material or prior endocarditis during dental procedures.

Norwood stage I creates a neoaorta from the pulmonary root and a systemic-to-pulmonary shunt; assess shunt patency by continuous flow and peak velocity.

Bidirectional Glenn anastomoses the superior vena cava to the pulmonary artery; assess the anastomotic gradient, SVC flow pattern, and any venovenous collaterals.

Fontan circulation connects the inferior vena cava to the pulmonary artery; assess conduit or lateral tunnel obstruction, fenestration flow, baffle leaks, and ventricular function.

After the arterial switch with the Lecompte maneuver, monitor coronary reimplantation patency, neo-aortic root dilation, and supravalvar pulmonary stenosis.

Mustard and Senning baffles redirect systemic venous blood to the mitral valve; look for baffle obstruction, baffle leaks, and systemic ventricular dysfunction.