Cardiac pressure estimation

My DDU point form notes on cardiac pressure estimation…

The rest of my DDU notes are here.

summary mainly from Bonita Anderson’s “A Sonographer’s Guide to the Assessment of Heart Disease”

Issues in pressure gradient estimation

nonparallel alignment

eg. 20° → cos 20° = 0.94 → 0.94² = 0.88 ∴ 12% underestimation

simplified Bernoulli equation ignores

flow acceleration (underestimates pressures)

issue in prosthetic valves

viscous friction (underestimates pressures)

relevant if CSA < 0.1 cm² or eccentric wall jets

↑ proximal velocities (V1) (overestimates pressures)

relevant if V1 ≥ 1.2 m/s

eg. aortic stenosis with high output state, significant AR, subvalvular obstruction

wrong Doppler signal

eg. TR instead of MR

arrhythmias

beat to beat variation
average over 2-3 beats (3-5 in AF, whole respiratory cycle for TR)

not same as invasive

can’t estimate peak to peak

in mild-moderate AS, Doppler-derived will be > peak to peak

rapid pressure recovery

causes big discrepancy between pullback gradient and Doppler

Issues in intracardiac pressure estimation

nonparallel alignment and simplified Bernoulli equation issues above under and overestimation

non-simultaneous measurements

eg. RV and LV systole not same time → affects measurements with VSD

BP measurement errors

AS, LVOTO, and sphygmomanometer error

estimation of low pressures by subtraction

eg. LAP = LVSP – 4VMR²

RAP estimation

summarised from Sonographer’s Guide, Bonita, p99

summary

subcostal

IVC size in subcostal, collapse with sniff

PWD of hepatic veins

A4C

tricuspid E/E’

restrictive filling

IVC size and collapsibility

in intermediate range (8) can

↓ to 3 if no secondary indices

↑ to high if <35% collapse and secondary indices

stay at 8 if unsure

not valid in ventilated

if IVC ≤ 12mm → RAP < 10 mmHg

young athletes commonly have dilated IVC but normal RAP
→ reassess in left lateral position

secondary indices

hepatic venous Doppler → SFF

PWD (3-5 mm sample volume) in medial hepatic vein

end expiratory apnoea or average 5-7 beats

trace VTIS wave and VTID wave

systolic filling fraction = SFF = VTIS wave / (VTIS wave + VTID wave) x 100

SFF < 55% → RAP > 8mmHg

can also use velocities instead of VTI above

not valid in AF, severe TR

restrictive filling
tricuspid E/E’ > 6

at lateral annulus

→ RAP ≥ 10 mmHg with high sensitivity, specificity

not accurate in ventilated, not valid in AF

RVEDP

same as RAP in absence of tricuspid stenosis – uncommon
if suspicious put CWD through tricuspid inflow and trace inflow VTI to get mean pressure gradient

Pulmonary artery pressures

all require good alignment

PASP

PAEDP

mPAP

PVR

multiple empiric methods
do not use as substitute for invasive PVR when this value is important to guide therapy

other features suggestive of pulmonary hypertension

pulmonary valve

M-mode in PSAX: mid-systolic notching, absent a wave
RVAcT < 100 ms, mid-systolic notching of RV outflow tract flow
↑ PR velocity

RV

dilation, hypertrophy ± moderator band, systolic function
RVPO
↑ TR velocity at time of pulmonary valve opening

RA

dilation of RA, coronary sinus

AV

M-mode: mid systolic notching of AV

commonly also have mitral valve prolapse, pericardial effusions

Left atrial pressures – see diastolic dysfunction notes
Left ventricular diastolic pressure – see diastolic dysfunction notes

Cover image: “Combinpedal” by James Heilman, MD – Own work.