Purpose:
Demonstrate the first use of a novel technology for quantifying suture forces on annuloplasty rings to better understand the mechanisms of ring dehiscence.
Description:
Force transducers were developed, attached to a size 24 Physio™ ring, and implanted in the mitral annulus of an ovine animal. Ring suture forces were measured after implantation and for cardiac cycles reaching peak left ventricular pressures (LVP) of 100, 125, and 150 mmHg.
Evaluation:
After implanting the undersized ring to the flaccid annulus, the mean suture force was 2.0±0.6 N. During cyclic contraction, anterior ring suture forces were greater than posterior ring suture forces at peak LVPs of 100 mmHg (4.9±2.0 N vs. 2.1±1.1 N), 125 mmHg (5.4±2.3 N vs. 2.3±1.2 N), and 150 mmHg (5.7±2.4 N vs. 2.4±1.1 N). The largest force was 7.4 N at 150 mmHg.
Conclusions:
Preliminary results demonstrate trends in annuloplasty suture forces and their variation with location and LVP. Future studies will significantly contribute to clinical knowledge by elucidating the mechanisms of ring dehiscence while improving annuloplasty ring design and surgical repair techniques.
Background
Mitral valve (MV) repair using annuloplasty rings is the preferred method of treatment for MV regurgitation, but the impact of annuloplasty ring placement on LV intraventricular flow has not been studied.
Methods
Annuloplasty rings of varing sizes were placed in 5 healthy sheep (intercommissural ring size = 24, 26, 28, 30, and 32 mm) and 3D phase-contrast MRI (“4D flow MRI”) was performed prior to and one week after ring placement. Normal diastolic flow consisted of diastolic intraventricular vortices that naturally unwound during systole.
Results
Post-surgical intraventricular flow was highly disturbed in all sheep and the disturbance was greatest for undersized rings. Ring size was highly correlated with the diastolic inflow angle (Pearson’s r = −0.62, P < 0.1, CI (95%) = [−0.92 0.14]). There was a mean angle increase of mean diastolic inflow angle increase = 12.3° (< 30 mm, P < 0.01, CI (95%) = [4.8°, 19.6°]) for rings < 30 mm. There was an inverse relationship between peak velocity and annuloplasty ring area (Pearson’s r = −0.80, P < 0.05, CI (95%) = [−0.96 −0.2]. Transmitral pressure gradients increased significantly from baseline 0.73 +/− 0.18 mmHg to post-annuloplasty 2.31 +/− 1.04 mmHg (P < 0.05).
Conclusions
MV annuloplasty ring placement disturbs normal LV intraventricular flow patterns and the degree of disturbance is closed associated with annuloplasty ring size.
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