Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
J Vet Intern Med. 2013 Jul-Aug;27(4):875-83. doi: 10.1111/jvim.12114. Epub 2013 Jun 3.
During the cardiac cycle, the ventricle undergoes a twisting motion because of the oblique orientation of the left ventricular (LV) myofibers. This can be quantified by speckle-tracking echocardiography (STE). In mitral regurgitation (MR) in humans, the short axis deformation has been suggested as being pivotal to LV function. Decreased and delayed LV twist has been described in experimental MR, but has not been studied in myxomatous mitral valve disease (MMVD).
(1) Magnitude (CSt) and rate (CSRs) of systolic circumferential deformation decrease before the onset of congestive heart failure (CHF); (2) magnitude and rate of LV twist decrease, and onset of untwist is delayed, with increasing MMVD severity.
A total of 97 privately owned small- to medium-sized dogs.
Severity of MMVD was assessed by echocardiography and presence of clinical signs of CHF. Magnitude and rate of LV twist and circumferential deformation were evaluated by STE.
Dogs with CHF receiving treatment had increased CSt, CSRs, early diastolic untwisting rate, and delayed onset of untwist compared to dogs with minimal MMVD and increased systolic twist compared to dogs with mild MMVD (all P < .01). CSt and time to onset of untwist increased with echocardiographic variables of MR severity (all P < .002). CSRs and several LV twist variables decreased with increasing systolic LV internal diameter (all P < .01).
No STE-derived variable was decreased before onset of CHF. In dogs with CHF receiving treatment, the delayed onset of relaxation might indicate LV dysfunction and the hyperdynamic CSt and LV twist reflect compensatory mechanisms.
在心动周期中，由于左心室（LV）心肌纤维的斜向排列，心室会发生扭转运动。这可以通过斑点追踪超声心动图（STE）来定量。在人类二尖瓣反流（MR）中，已经提出短轴变形对于 LV 功能至关重要。在实验性 MR 中已经描述了 LV 扭转的减少和延迟，但在黏液样二尖瓣疾病（MMVD）中尚未进行研究。
（1）在充血性心力衰竭（CHF）发作之前，收缩期圆周变形的幅度（CSt）和速率（CSRs）降低；（2）随着 MMVD 严重程度的增加，LV 扭转的幅度和速率降低，并且解旋开始延迟。
共有 97 只私人拥有的中小体型犬。
通过超声心动图评估 MMVD 的严重程度，并评估 CHF 的临床症状。通过 STE 评估 LV 扭转和圆周变形的幅度和速率。
接受治疗的 CHF 犬的 CSt、CSRs、早期舒张解旋率和解旋开始延迟增加，与 MMVD 最小和轻度 MMVD 的犬相比，LV 收缩期扭转增加（均 P <.01）。CSt 和解旋开始时间随着 MR 严重程度的超声心动图变量增加而增加（均 P <.002）。CSRs 和几个 LV 扭转变量随着收缩期 LV 内径的增加而降低（均 P <.01）。
在 CHF 发作之前，没有 STE 衍生变量减少。在接受治疗的 CHF 犬中，松弛开始延迟可能表明 LV 功能障碍，而高动力的 CSt 和 LV 扭转反映了代偿机制。
