**1. Introduction**

[72] Koyama, J, Ray-sequin, P. A, & Falk, R. H. Longitudinal myocardial function as‐ sessed bytissue velocity, strain, and strain rate tissue Doppler echocardiography in patients with AL (primary) cardiac amyloidosis. Circulation. (2003). , 107, 2446-2452.

[73] Phelan, D, Collier, P, Thavendiranathan, P, Popovic, Z. B, Hanna, M, Plana, J. C, Mar‐ wick, T. H, & Thomas, J. D. Relative apical sparing of longitudinal strain using twodimensional speckle-tracking echocardiography is both sensitive and specific for the

[74] Olson, L. J, Baldus, W. P, & Tajik, A. J. Echocardiographic features of idiopathic he‐

[75] Anderson, L. J, Holden, S, Davis, B, et al. Cardiovascular T2\* magnetic resonance for the early diagnosis of myocardial iron overload. Eur Heart J (2001). , 22, 2171-9. [76] Cardinale, D, Colombo, A, Lamantia, G, Colombo, N, Civelli, M, Giacomi, G. D, Ru‐ bino, M, Veglia, F, Fiorentini, C, & Cipolla, C. M. Anthracycline-Induced Cardiomy‐ opathy Clinical Relevance and Response to Pharmacologic Therapy. J Am Coll

[77] Migrino, R. Q, Aggarwal, D, Konorev, E, Brahmbhatt, T, Bright, M, & Kalyanaraman, B. Early detection of doxorubicin cardiomyopathy using two-dimensional strain cho‐ cardiography. Ultrasound Med Biol. (2008). Feb; Epub 2007 Oct 23., 34(2), 208-14.

diagnosis of cardiac amyloidosis. Heart. (2012). , 98, 1442-1448.

mochromatosis. Am J Cardiol. (1987). Oct 1; , 60(10), 885-9.

Cardiol. (2010). , 55(3), 213-220.

28 Cardiomyopathies

Merely 50 years ago, Inge Edler and Helmut Hertz were the first to use an ultrasound trans‐ ducer, borrowed from a local shipyard where it was used for the detection of cracks in metal plates, to record the motion of cardiac structures. Ever since then, the clinical use of echocar‐ diography has steadily increased. Echocardiography is an attractive imaging modality for several reasons. It is highly available, relatively inexpensive, it does not involve ionising radiation, and images are displayed in realtime allowing prompt diagnosis. However, despite a staggering technical progress in echocardiography, regional myocardial function was, until recently, still assessed by visual analysis of wall motion, a relatively inaccurate and poorly reproducible manner.

During the last 10 years, tissue Doppler imaging has been developed to quantify regional myocardial function [1]. Initially formatted as a one-dimensional method for measurement of regional longitudinal myocardial velocity profiles, tissue Doppler imaging has been further developed to allow measurements of one-dimensional regional strain [2]. This index measures local deformation as opposed to (passive and active) motion and thereby better reflects regional myocardial function. However, tissue Doppler imaging is inextricably limited by the angle-dependency of the technique. Because of this limitation, it is not clinically feasible to measure myocardial deformation in directions not parallel to the direction of the Doppler beam, such as left ventricular rotation. Although some have tried to override this limitation by applying complex algorithms [3], measurement of left ventricular rotation by echocardiog‐ raphy has only recently become clinically feasible by the development of speckle tracking echocardiography.

© 2013 van Dalen and Geleijnse; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **1.1. Left ventricular twist**

In the 16th century, Leonardo daVinci already described the rotational motion of the left ventricle [4,5] and in 1669, Richard Lower observed that myocardial contraction could be compared with 'the wringing of a linen cloth to squeeze out the water' [6]. The mechanistic basis for this wringing motion or twist lies in the complex spiral architecture of the left ventricle as revealed by the anatomical studies of Streeter et al. [7] and Greenbaum et al. [8] The left ventricle consists of obliquely oriented muscle fibres that vary from a smaller-radius, righthanded helix at the subendocardium to a larger-radius, left-handed helix at the subepicardium. The functional consequence of this three-dimensional helical structure is a cyclic systolic twisting deformation, resulting from clockwise basal rotation and counterclockwise apical rotation (as seen from the apex). Left ventricular twist plays a pivotal role in the mechanical efficiency of the heart, making it possible that only 15% fibre shortening results in a 60% reduction in left ventricular volume [9]. Moreover, diastolic untwisting of the left ventricle plays a crucial role in diastolic suction [10]. In the last decades, left ventricular twist has mainly been studied with tagged magnetic resonance imaging (MRI). However, lack of availability, limited temporal resolution, and the time-consuming and complex data analysis have precluded its use in routine clinical practice. More recently, it became possible to study left ventricular twist with tissue Doppler techniques and two-dimensional speckle tracking echocardiography. As mentioned before, this latter technique offers the opportunity to track myocardial deformation independently of both cardiac translation and the insonation angle.

More recently, assessment of left ventricular twist by speckle tracking echocardiography has become available. The fundamental principle of deformation imaging by speckle tracking echocardiography is simple. A certain segment of myocardial tissue is shown in an ultrasound image as a pattern of gray values caused by the interference of ultrasound reflected by the tissue. Such a pattern, resulting from the spatial distribution of the gray values, is commonly referred to as a speckle pattern. If the position of the myocardial segment within the ultrasound image changes, one can presume that the position of the speckle pattern will change accord‐ ingly. Since each region of the myocardium has its own rather unique speckle pattern, the speckle pattern can serve as a fingerprint of the region of interest of the myocardium. Fur‐ thermore, given a sufficiently high frame rate, it can be assumed that particular speckle patterns are preserved between subsequent image frames [14]. Thus, tracking of the speckle pattern during the cardiac cycle allows one to follow the motion of this myocardial segment within the two-dimensional ultrasound image. Several studies have shown [15,16] that twist data derived from commercially available speckle tracking software correlated well with tagged MRI. To be able to evaluate serial studies of left ventricular twist by speckle tracking echocardiography in the same patient, the technique needs to be reproducible as well. Van Dalen et al. [17] studied the feasibility and variability of left ventricular twist measurement and found that the method is feasible in approximately two thirds of subjects and has good intraobserver, interobserver and temporal reproducibility, allowing to study changes over

Left Ventricular Twist in Cardiomyopathy http://dx.doi.org/10.5772/55281 31

In this chapter, the important physiological role of left ventricular twist and untwist will be explained. Furthermore, cardiomyopathies may show striking alterations of left ventricular twist. The pathophysiological background and potential clinical role of these changes is

According to the Hippocratic treatise "On the Heart", the heart is shaped like a pyramid, has a deep crimson colour, and is an extremely strong muscle. From the top of the heart, rivers that irrigate the "mortal habitation" flow into the body. If these rivers dry up, then the person dies [18]. Leonardo da Vinci's investigations of the heart and circulation began nearly 18 centuries later, in the 1490s. Da Vinci made a number of advances in the understanding of the heart and blood flow. For example, he showed that the heart is indeed a muscle, that it has four chambers an he linked the pulse in the wrist with left ventricular contraction. Further‐ more, as mentioned before, Da Vinci was the first to describe the rotational motion of the left ventricle [4,5]. However, it lasted until the late 1960s before left ventricular twist was described in more detail by Streeter et al. [7] following a study of post-mortem canine hearts. Using a rapid method of fixation, they were able to analyze these hearts in either systole, begin diastole or end-diastole. Fibre angle, representing the angle between the myofibres as projected onto the circumferential-longitudinal plane and the circumferential axis, was introduced for quantification of fibre orientation. This angle changed continuously from the subendocardium to the subepicardium, typically ranging from +60 degrees at the subendocardium to –60

time in left ventricular twist in an individual patient.

**2. Physiology of left ventricular twist**

discussed.

#### **1.2. Assessment of left ventricular twist**

Ever since the description of the rotational motion of the left ventricle by Leonardo da Vinci [4,5] in the 16th century, left ventricular twist has intrigued clinicians and researchers in their quest to understand the performance of the human heart. In the early 1960s, Harrison et al. [11] developed a method to measure external ventricular wall dimensions during the cardiac cycle. Silver tantalum clips were sutured into the human epicardium during cardiac surgery and these markers were viewed by calibrated cineradiographs. Ingels et al. [12] further developed this technique and studies of left ventricular twist continued throughout the 1980s. Unfortu‐ nately, progress was limited due to the invasive nature of the technique with its inherent limitations; the surgical implantation of the clips frequently led to local inflammation, hemorrhage and fibrosis, possibly affecting left ventricular twist. In addition, implantation of the clips could only be done in surgically accessible areas, which limited the left ventricular areas studied. In 1990, Buchalter et al. [13] described for the first time the non-invasive assessment of left ventricular twist with MRI. A tagging technique was employed to label specific areas of the myocardium prior to image acquisition. Tagging is achieved by selective radio-frequency excitation of narrow planes and appears as black lines on the image acquisi‐ tion. Using dedicated software, displacement of these tagging lines can be monitored, allowing quantification of left ventricular deformation. However, the limited availability, the poor temporal resolution, and the time-consuming and complex data analysis have precluded its use in routine clinical practice.

More recently, assessment of left ventricular twist by speckle tracking echocardiography has become available. The fundamental principle of deformation imaging by speckle tracking echocardiography is simple. A certain segment of myocardial tissue is shown in an ultrasound image as a pattern of gray values caused by the interference of ultrasound reflected by the tissue. Such a pattern, resulting from the spatial distribution of the gray values, is commonly referred to as a speckle pattern. If the position of the myocardial segment within the ultrasound image changes, one can presume that the position of the speckle pattern will change accord‐ ingly. Since each region of the myocardium has its own rather unique speckle pattern, the speckle pattern can serve as a fingerprint of the region of interest of the myocardium. Fur‐ thermore, given a sufficiently high frame rate, it can be assumed that particular speckle patterns are preserved between subsequent image frames [14]. Thus, tracking of the speckle pattern during the cardiac cycle allows one to follow the motion of this myocardial segment within the two-dimensional ultrasound image. Several studies have shown [15,16] that twist data derived from commercially available speckle tracking software correlated well with tagged MRI. To be able to evaluate serial studies of left ventricular twist by speckle tracking echocardiography in the same patient, the technique needs to be reproducible as well. Van Dalen et al. [17] studied the feasibility and variability of left ventricular twist measurement and found that the method is feasible in approximately two thirds of subjects and has good intraobserver, interobserver and temporal reproducibility, allowing to study changes over time in left ventricular twist in an individual patient.

In this chapter, the important physiological role of left ventricular twist and untwist will be explained. Furthermore, cardiomyopathies may show striking alterations of left ventricular twist. The pathophysiological background and potential clinical role of these changes is discussed.
