Clinical relevancy of the myocardial velocity gradient: limitations of a binary response

Doppler tissue echocardiographic myocardial velocity gradient (MVG) overcomes translational or tethered motion effects. Diagnostic applications rely on MVG numeric value, an instantaneous value calculated at peak endocardial velocity. Our aim was to test the clinical relevancy of MVG for patients with dilated cardiomyopathy (CM) at rest. Efficiency of MVG, as a marker of the underlying mechanism, ischemic or nonischemic, was compared with that of mean velocities averaged over a cycle.

Peak and mean velocities were measured and MVG calculated during ejection, and early and late diastole, in the endocardium and epicardium on color M-mode Doppler tissue echocardiographic parasternal recordings of the posterior wall, simultaneously imaged with the septum. The population consisted of 34 patients with similar clinical presentation (left ventricular ejection fraction < 40%, left ventricular end-diastolic diameter > 6 cm, and proven ischemic [14] or nonischemic [20] dilated CM) and 16 control subjects.

Doppler tissue echocardiography data significantly differed between control subjects and all patients with CM. Between patients, the only significant differences were found at the posterior wall for mean velocities at the epicardium in systole (9 +/- 4 mm/s for ischemic vs 14 +/- 5 mm/s for nonischemic, P =.002), and at both layers in early diastole (endocardium, 14 +/- 9 vs 29 +/- 12 mm/s, P =.0004; epicardium, 12 +/- 4 vs 22 +/- 11 mm/s, P =.002; ischemic vs nonischemic CM, respectively).

Specific features of CM were characterized by myocardial velocity changes studied layer by layer throughout a phase. The binary response of transient peak MVG could not reach this goal.