Torsion dynamics in the evolution from acute to chronic mitral regurgitation.
OBJECTIVE
Left ventricular (LV) torsion reduces transmural fiber strain gradients during systole, and torsional recoil in early diastole is thought to assist LV filling. To test the hypothesis that deterioration of torsional dynamics accompanied LV dysfunction during the evolution of mitral regurgitation (MR), torsion was measured during the progression from acute to chronic MR in a canine model.


METHODS
Seven dogs underwent cardiopulmonary bypass for LV marker placement and creation of MR by disrupting the posterior leaflet. After 7-10 days, three-dimensional marker coordinates were measured with biplane videofluoroscopy to study LV geometry, size and function, plus maximal torsional deformation, time of maximal torsion relative to end-ejection, and early diastolic torsional recoil during the first 5% of filling. After three months, the animals were re-studied.


RESULTS
Progression from acute to chronic MR was associated with a significant decrease in maximum LV dP/dt (1,574+/-213 to 1,300+/-252 mmHg/s, p <0.01) and an increase in LVEDP from 11+/-5 to 15+/-5 mmHg (p <0.01). After three months of MR, maximum torsional deformation decreased from 6.3+/-1.9 to 4.7+/-2.0 degrees (p = 0.04), as did early diastolic recoil (-3.8+/-1.0 to -1.5+/-1.7 degrees, p = 0.03).


CONCLUSIONS
Progression from acute to chronic MR is accompanied by decreased and delayed systolic LV torsional deformation and a decline in early diastolic recoil, which may contribute to LV dysfunction by increasing transmural strain gradients during systole and impairing diastolic filling. As torsional deformation and recoil can be measured non-invasively with MRI in humans, such measurements might prove useful in patients with progressive MR as an adjunct to determine the timing of surgical repair.
Tibayan
Frederick A
FA
Department of Cardiovascular and Thoracic Surgery, Stanford University School of Medicine, California 94305-5247, USA.
Yun
Kwok L
KL
Fann
J I
JI
Lai
David T M
DT
Timek
Tomasz A
TA
Daughters
George T
GT
Ingels
Neil B
NB
Miller
D Craig
DC
D000208:Acute Disease; D000818:Animals; D002908:Chronic Disease; D004195:Disease Models, Animal; D004285:Dogs; D006439:Hemodynamics; D008944:Mitral Valve Insufficiency / Q000503:physiopathology*; D014102:Torsion Abnormality; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*