Table 2.

Summary of the assessment of embryonic and fetal hearts.

Method	Parameter	Unit	Structure (abbreviation)
2D ultrasound B-mode echoloops	Morphological assessment, position, and diameters of cardiac compartments.	mm	Right atrium (RA), left atrium (LA), right ventricle (RV), left ventrile (LV), common outflow tract (cOFT), pulmonary trunk (PT), aorta (Ao), inter ventricular septum (IVS), common atrioventricular canal (cAVC), mitral valve (MV), and tricuspid valve (TV)
			Definition	Formula
Pulsed-wave Doppler	Peak E	m/s	Early, diastolic ventricular filling
	Peak A	m/s	Active, diastolic ventricular filling
	E/A ratio
	RR interval	ms	Cycle length/evaluation of heart rate
	DFT	ms	Diastolic filling time
	IVRT	ms	Isovolumetric relaxation time
	IVCT	ms	Isovolumetric contraction time
	ET	ms	Ejection time
	MPI/Tei index		Myocardial performance index	IVRT + IVCT/ET
	Peak velocities cOFT, Ao, PT	m/s
	VTI	mm	Velocity time integral
	SV		Stroke volume	SV = TVI × (Ao or cOFT diameter/2)2 × π
	CO	mL/min	Cardiac output
M-mode	VID	mm	Ventricular inner diameter
	LVIDd	mm	End diastolic left ventricular inner diameter
	LVIDs	mm	End systolic left ventricular inner diameter
	RVIDd	mm	End diastolic right ventricular inner diameter
	RVIDs	mm	End systolic right ventricular inner diameter
	IVSd	mm	End diastolic interventricular septum diameter
	IVSs	mm	End systolic interventricular septum diameter
	FS	%	Fractional shortening	(VIDd − VIDs)/VIDd × 100%