Left Ventricular Twist
Left ventricular (LV) twist describes the instantaneous circumferential motion of the apex with respect to the base of the heart and has an important role in LV function. LV twist originates from the dynamic interaction between oppositely wound subepicardial and subendocardial myocardial fibres. The direction of LV twist is governed by the subepicardial fibres, mainly owing to their longer arm of movement. Recently, speckle tracking echocardiography has been introduced as a new method for angle-independent quantification of LV twist. The aim of the thesis was to investigate the acquisition of LF twist by speckle tracking echocardiography and the physiology and clinical application of LV twist. A more caudal transducer position, as compared to the standard transducer position, was associated with increased measured LV twist. Therefore, in each patient the most caudal available transducer position should be used. Assessment of LV twist by speckle tracking echocardiography appeared to be feasible in approximately two thirds of subjects and had a good intraobserver, interobserver and temporal reproducibility, allowing to study changes over time in LV twist in an individual patient. Several physiological aspects of LV twist were studied. Differences in the extent and timing of de-rotation at the LV apical level as compared to the basal level may facilitate blood flow all the way to the apex. Furthermore, LV twist was significantly influenced by LV configuration. Taken the important function of LV twist into account, this finding highlights the vital influence of cardiac shape on LV systolic function. LV twist increased with aging, resulting from both increased LV apical rotation and decreased rotational deformation delay, defined as the difference of time to peak basal and apical rotation. This may explain the preservation of LV ejection fraction in the elderly. In addition, relative peak diastolic untwisting velocity and untwisting rate were impaired with increasing age, resulting in delayed LV untwisting. Finally, the clinical application of LV twist was investigated. LV solid body rotation may be an objective, quantitative, and reproducible criterion with a good predictive value for the diagnosis of noncompaction cardiomyopathy. LV twist, and in particular changes within one patient, may also provide an easy assessable marker of subendocardial ischemia, for example in aortic stenosis patients, since subendocardial ischemia with loss of contraction of the counteracting subendocardial fibres will lead to increased LV twist. Apart from this, assessment of LV twist in cardiac disease may give important insight into cardiac pathophysiology.
|Keywords||aortic stenosis, cardiac pathophysiology, cardiac physiology, cardiomyopathy, diastolic function, echocardiography, left ventricular function, left ventricular twist, left ventricular untwisting, speckle tracking, systolic function|
|Promotor||M.L. Simoons (Maarten)|
|Publisher||Erasmus University Rotterdam|
|Sponsor||Netherlands Heart Foundation|
van Dalen, B.M.. (2009, September 23). Left Ventricular Twist. Erasmus University Rotterdam. Retrieved from http://hdl.handle.net/1765/22636