Newer echocardiographic techniques for aortic-valve imaging: Clinical aids today, clinical practice tomorrow

Table 1 Prevalence[8,9], prognosis[10] and percentage of patients undergoing surgery[8] for severe aortic stenosis and preserved ejection fraction

	High gradient (mean > 40 mmHg)	Low gradient (mean < 40 mmHg)
Normal flow (SV > 35 mL/m2)
Prevalence	30%-62.7%	15.3%-38%
Prognosis (2 yr survival rates)	44% ± 6%	83% ± 6% (best prognosis)
% Undergoing surgery	80% (highest rates of surgery)	53%
Low flow (SV < 35 mL/m2)
Prevalence	8%-13.2%	8.8%-24%
Prognosis (2 yr survival rates)	30% ± 12%	27% ± 13%-worst prognosis
% Undergoing surgery	68%	36%-lowest rates of surgery

Table 2 Definitions of basic strain parameters

Parameter	Definition
Strain	Change in myocardial fiber length relative to its resting phase
Global longitudinal strain	Percentage change in LV fiber length in the longitudinal axis
Global circumferential strain	Percentage change in LV circumference in the short axis view
Global radial strain	Percentage change in LV wall thickness in the short axis view
Strain rate	Rate at which change in myocardial fiber length relative to its resting phase occurs
Twist/Torsion/Rotation	Myofiber geometry in the LV myocardium changes from a right-handed helix in the subendocardium to a left-handed helix in the subepicardium, and this results in twisting during systole with the apex rotating counterclockwise and the base in a clockwise direction

LV: Left ventricle.