Preload dependency of left ventricular torsion: the impact of normal saline infusion.
BACKGROUND
left ventricular (LV) rotation results from contraction of obliquely oriented myocardial fibers. The net difference between systolic apical counterclockwise rotation and basal clockwise rotation is left ventricular torsion (LVT). Although LVT is altered in various cardiac diseases, determinants of LVT are incompletely understood.


RESULTS
LV end-diastolic volume, LV apical and basal rotation, peak systolic LVT, and peak early diastolic untwisting rate were measured by speckle-tracking echocardiography in healthy subjects (n=8) before and after infusion of a weight-based normal saline bolus (2.1±0.3 L). Saline infusion led to a significant increase in end-diastolic LV internal diameter (45.9±3.7 versus 47.6±4.2 mm; P=0.002) and LV end-diastolic volume (90.0±21.6 versus 98.3±19.6 mL; P=0.01). Stroke volume (51.3±10.9 versus 63.0±15.5 mL; P=0.003) and cardiac output (3.4±0.8 versus 4.4±1.5 L/min; P=0.007) increased, whereas there was no change in heart rate and blood pressure. There was a significant increase in the magnitude of peak systolic apical rotation (7.5±2.4° versus 10.5±2.8°; P<0.001) but no change in basal rotation (-4.1±2.3° versus -4.8±3.1°; P=0.44). Accordingly, peak systolic LVT increased by 33% after saline infusion (11.2±1.3° versus 14.9±1.7°; P<0.001). This saline-induced increase in LVT was associated with a marked increase in peak early diastolic untwisting rate (72.3±21.4 versus 136.8±30.0 degrees/s; P<0.001).


CONCLUSIONS
peak systolic LVT and peak early diastolic untwisting rate are preload-dependent. Changes in LV preload should be considered when interpreting results of future LVT studies.
Weiner
Rory B
RB
Division of Cardiology, Massachusetts General Hospital, Boston, Mass., USA.
Weyman
Arthur E
AE
Khan
Abigail May
AM
Reingold
Jason S
JS
Chen-Tournoux
Annabel A
AA
Scherrer-Crosbie
Marielle
M
Picard
Michael H
MH
Wang
Thomas J
TJ
Baggish
Aaron L
AL
D000328:Adult; D000704:Analysis of Variance; D002306:Cardiac Volume / Q000187:drug effects; D018618:Echocardiography, Doppler, Color / Q000379:methods; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007262:Infusions, Intravenous; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D015588:Observer Variation; D012016:Reference Values; D012965:Sodium Chloride / Q000494:pharmacology*; D014102:Torsion Abnormality / Q000000981:diagnostic imaging* / Q000628:therapy*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000187:drug effects*
D012965:Sodium Chloride
J Gen Physiol. 2003 Feb;121(2):97-110
12566538
J Appl Physiol (1985). 2009 Feb;106(2):362-9
18988768
Circ Res. 1969 Mar;24(3):339-47
5766515
J Am Soc Echocardiogr. 2008 Aug;21(8):887-94
18325731
Heart. 2010 Jan;96(1):49-55
19858137
Circulation. 1991 Apr;83(4):1315-26
2013149
Circulation. 2006 May 30;113(21):2534-41
16717154
J Am Coll Cardiol. 2005 Jun 21;45(12):2034-41
15963406
J Am Soc Echocardiogr. 2008 Mar;21(3):268-74
17628423
Am J Physiol. 1999 Sep;277(3):H1053-60
10484428
IEEE Trans Biomed Eng. 1985 Oct;32(10):764-9
4054921
Sci Am. 1986 Jun;254(6):84-91
3704622
J Am Soc Echocardiogr. 2006 Oct;19(10):1280-5
17000368
Am J Physiol. 1982 Sep;243(3):H379-90
7114270
Am J Cardiol. 1970 Sep;26(3):221-30
5505446
Circulation. 1994 Jan;89(1):142-50
8281641
J Am Soc Echocardiogr. 2005 Dec;18(12):1440-63
16376782
Basic Res Cardiol. 2006 Nov;101(6):465-70
16783487
J Am Soc Echocardiogr. 2009 Feb;22(2):107-33
19187853
Circulation. 2006 May 30;113(21):2524-33
16717149
Am J Physiol Heart Circ Physiol. 2008 Jan;294(1):H505-13
18032523
Circulation. 1992 Dec;86(6):1919-28
1451263
Am J Physiol. 1993 Oct;265(4 Pt 2):H1444-9
8238432
Circulation. 1995 Jul 1;92(1):130-41
7788907
J Appl Physiol (1985). 2000 Apr;88(4):1228-38
10749812
Circulation. 2001 Oct 2;104(14):1639-45
11581142
Circulation. 1997 Jul 1;96(1):232-7
9236439
Circulation. 1999 Jul 27;100(4):361-8
10421595