Augmentation of left ventricular apical endocardial rotation with inotropic stimulation contributes to increased left ventricular torsion and radial strain in normal subjects: quantitative assessment utilizing a novel automated tissue tracking technique.
BACKGROUND
The difference in the left ventricular (LV) torsion of the endo- and epicardium (Endo, Epi) with inotropic stimulation and its relation to radial strain (RS) remain unclear.


RESULTS
LV basal and apical short-axis images were recorded in 13 normal subjects at rest and during dobutamine infusion (5, 10 microg x kg (-1) x min(-1)). A total of 8 points (anterior, lateral, posterior and septum in both Endo and Epi) were manually placed by 2-dimensional tissue tracking technique and the movement of these points during a cardiac cycle was tracked, after which the rotation angles and RS were calculated. LV torsion was defined as the net difference between the basal and apical rotations. In the LV apex, Endo-rotation increased (7.8+/-2.7 to 14.1+/-4.6 degrees, p<0.01), whereas Epi-rotation was unchanged, with dobutamine. The apical Endo-rotation was significantly greater than the Epi-rotation, although no difference was seen between the Endo and Epi in the LV base throughout the study. During dobutamine infusion, the LV Endo-torsion increased (9.5+/-2.8 to 19.3+/-4.8 degrees, p<0.01) and these values were greater than those for Epi. The apical RS increased with the dobutamine dose (39.0+/-9.3 to 61.9+/-15.5%, p<0.01), whereas basal RS initially increased at 5 microg x kg(-1) x min(-1), but thereafter showed no further increase at 10 microg x kg(-1) x min(-1) of dobutamine.


CONCLUSIONS
Augmentation of LV rotation with inotropism was clearly observed in the apical Endo, thus causing increased LV endo-torsion and apical RS.
Akagawa
Eizo
E
Division of Cardiology, Department of Medicine and Clinical Science, Yamaguchi University Graduate School of Medicine, Ube, Japan.
Murata
Kazuya
K
Tanaka
Nobuaki
N
Yamada
Hirotsugu
H
Miura
Toshiro
T
Kunichika
Hideki
H
Wada
Yasuaki
Y
Hadano
Yasuyuki
Y
Tanaka
Takeo
T
Nose
Yoshio
Y
Yasumoto
Kyonori
K
Kono
Masateru
M
Matsuzaki
Masunori
M
D000328:Adult; D000465:Algorithms; D001331:Automation; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004280:Dobutamine / Q000494:pharmacology*; D004452:Echocardiography; D004699:Endocardium / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009200:Myocardial Contraction / Q000502:physiology*; D012016:Reference Values; D012399:Rotation; D013314:Stress, Mechanical; D014102:Torsion Abnormality; D016277:Ventricular Function, Left / Q000187:drug effects*
D002316:Cardiotonic Agents; D004280:Dobutamine