RDCS Pediatric flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Axial resolution formula

Axial resolution equals spatial pulse length divided by two; it improves with higher frequency and fewer cycles per pulse, and it is the smallest detectable separation along the beam axis.

Nyquist limit

The Nyquist limit is half the pulse repetition frequency. Doppler shifts that exceed it alias and wrap around; raising the PRF, shifting the baseline, or switching to continuous wave Doppler resolves the aliasing.

Mechanical index

The mechanical index equals peak negative pressure in megapascals divided by the square root of frequency in megahertz; it estimates cavitation risk, and the FDA limit for general cardiac imaging is 1.9.

Doppler angle correction

The Doppler shift is proportional to the cosine of the angle between the ultrasound beam and blood flow; keeping the angle at or below 20 degrees limits velocity error to under six percent.

Thermal index

The thermal index estimates heating and equals acoustic power divided by the power required to raise tissue temperature one degree Celsius; it should generally be kept below 6 during cardiac imaging.

Frame rate determinants

Frame rate equals pulse repetition frequency divided by the number of lines per frame; increasing depth, sector width, or line density reduces frame rate and worsens temporal resolution.

Ductus arteriosus closure

Functionally the ductus arteriosus constricts within 24 to 48 hours after birth and closes anatomically by 2 to 3 weeks; prostaglandin E1 infusion keeps it patent in ductal-dependent lesions.

Tricuspid mitral offset

The tricuspid valve inserts more apically than the mitral valve; a septal offset of up to about 8 mm is normal in children, while greater displacement suggests Ebstein anomaly.

Cardiac output formula

Cardiac output equals heart rate multiplied by stroke volume, and stroke volume equals the outflow tract cross-sectional area multiplied by the Doppler velocity-time integral.

Fetal circulation shunts

Three fetal shunts bypass the lungs and liver: the ductus venosus, foramen ovale, and ductus arteriosus; the foramen ovale shunts oxygenated blood from the right to the left atrium.

Pulmonary vascular resistance fall

Pulmonary vascular resistance falls rapidly after birth and approaches adult values by 6 to 8 weeks; this fall governs when a left-to-right shunt produces pulmonary overcirculation.

Qp/Qs shunt ratio

The pulmonary-to-systemic flow ratio equals right ventricular outflow area times its velocity-time integral, divided by the same product for the left ventricular outflow tract; values above 1.5 indicate a significant shunt.

Tetralogy of Fallot features

Tetralogy of Fallot consists of a large ventricular septal defect, an overriding aorta, right ventricular outflow obstruction, and right ventricular hypertrophy; the severity of obstruction determines the degree of cyanosis.

D-transposition of great arteries

In D-transposition the aorta arises from the right ventricle and the pulmonary artery from the left, so the great vessels run parallel; survival requires mixing through an atrial septal defect, ventricular septal defect, or patent ductus.

Hypoplastic left heart stages

Hypoplastic left heart palliation proceeds from the Norwood stage I with a systemic-to-pulmonary shunt, to the bidirectional Glenn, then the Fontan; later stages depend on passive pulmonary blood flow.

Coarctation Doppler findings

Coarctation appears as 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 features

Ebstein anomaly shows apical displacement of the tricuspid leaflets, an atrialized right ventricle, and tricuspid regurgitation; Wolff-Parkinson-White syndrome is present in a minority of affected patients.

Kawasaki coronary criteria

Kawasaki disease produces coronary dilation or aneurysms, defined by internal diameter Z-scores of at least 2.5; early intravenous immunoglobulin plus aspirin reduces the risk of giant aneurysms.

Tamponade echo signs

Tamponade shows a pericardial effusion with right atrial systolic and right ventricular diastolic collapse, a plethoric inferior vena cava, and respiratory variation in mitral and tricuspid inflow velocities.

Rheumatic mitral regurgitation

Acute rheumatic fever most commonly damages the mitral valve, causing regurgitation; diagnosis uses Jones criteria requiring streptococcal evidence plus major and minor clinical manifestations.

Rhabdomyoma association

Cardiac rhabdomyoma is the most common pediatric cardiac tumor, frequently multiple and ventricular, and is strongly associated with tuberous sclerosis; many lesions regress spontaneously over time.

RVSP from TR jet

Right ventricular systolic pressure is estimated as four times the square of the tricuspid regurgitation peak velocity plus right atrial pressure, using the simplified Bernoulli equation.

Simpson biplane ejection fraction

Ejection fraction by Simpson's rule uses end-diastolic and end-systolic volumes traced in apical four- and two-chamber views by summing disks; pediatric normal left ventricular ejection fraction is about 55 to 75 percent.

Fractional shortening formula

Fractional shortening equals end-diastolic dimension minus end-systolic dimension, divided by end-diastolic dimension; normal pediatric values are approximately 28 to 44 percent.

Tei myocardial performance index

The Tei index equals isovolumic contraction time plus isovolumic relaxation time divided by ejection time; normal values are roughly 0.35 to 0.45 for both ventricles.

Hypertrophic cardiomyopathy findings

Hypertrophic cardiomyopathy shows asymmetric septal thickening, systolic anterior motion of the mitral valve, and dynamic outflow obstruction with a late-peaking dagger-shaped Doppler profile.

Global longitudinal strain

Speckle-tracking global longitudinal strain averages segmental myocardial shortening; normal values are about minus 18 to minus 22 percent, and it detects dysfunction earlier than ejection fraction.

Subcostal view advantage

The subcostal window uses the liver as an acoustic window and gives the best images in infants, showing the atrial septum, systemic and pulmonary venous connections, and ventricular septum.

Suprasternal notch view

The suprasternal notch view displays the aortic arch and head and neck vessels in a candy-cane orientation and is used to detect coarctation and patent ductus arteriosus.

Bidirectional Glenn circulation

In a bidirectional Glenn, the superior vena cava is anastomosed to the pulmonary artery for passive pulmonary blood flow, while the inferior vena cava continues to drain into the systemic atrium.

Fontan baffle assessment

After a Fontan, echocardiography assesses the inferior vena cava-to-pulmonary artery conduit for obstruction, thrombus, and fenestration flow, along with ventricular systolic and diastolic performance.

Arterial switch complications

After the arterial switch operation with the Lecompte maneuver, surveillance focuses on coronary artery patency, neo-aortic root dilation, and supravalvar pulmonary stenosis at the anastomosis.