Longitudinal myocardial strain and strain rate can be estimated by TDI technique and can provide useful information on local myocardial motion or deformation relative to the adjacent myocardium [9]. One of the first studies on strain in HCM was by Yang et al. [10], who reported the assessment of regional myocardial function in 31 adults with HCM diagnosed echocardiographically. Longitudinal strain was evaluated at the basal, mid, and apical segments of septal and lateral walls. It was significantly reduced in the septal segments of patients with HCM compared with control patients. More importantly, within the septum, midseptum longitudinal strain was significantly diminished compared with basal and apical segments. Kato et al. [11] demonstrated a major role of strain rate in differentiating nonobstructive HCM from hypertensive LV hypertrophy. The authors compared an HCM population and hypertensive patients and showed that at multivariate analysis, systolic strain rate and interventricular septum (IVS)/posterior wall thickness ratio were the most powerful predictors for the diagnosis of HCM. However, TDI-derived strain imaging also has technical limitations due to its angle dependence and frequent artifacts.

Speckle-tracking echocardiography, relatively a new imaging technique that allows objective and quantitative evaluation of global and regional myocardial deformation independently from the angle of insonation and from cardiac translational movements [12], has been employed in HCM in various settings. Serri et al. [13] applied 2D strain echocardiography to a subset of patients with familial nonobstructive HCM. Despite apparently normal systolic function (with the use of standard criteria), all components of strain (longitudinal, transverse, circumferential, radial) were significantly reduced in HCM in comparison with a healthy control population. Carasso et al. [14] showed that patients compared with controls had higher circumferential strain and lower longitudinal strain. In addition, mid-LV rotation was clockwise (opposite to normal). LV outflow-tract (OT) obstruction and clinical status were related to more circumferentially directed strain and reduced apical biplanar strain.

The ability of predicting the presence of myocardial fibrosis in HCM patients using echocardiography could have important implications, especially when predicting adverse outcomes, such as sudden death (SD). Funabashi et al. [15] used speckle-tracking echocardiography and cardiac magnetic resonance (CMR) to study 29 HCM patients. The authors showed that absolute peak longitudinal strain values were significantly lower in fibrotic lesions than in nonfibrotic lesions (Fig. 11.2). Moreover, there is an inverse association between various histopathologic findings typical of HCM (myocyte hypertrophy, disarray, small intramural coronary arteriole dysplasia, interstitial fibrosis) and septal strain rate in symptomatic HCM patients who undergo surgical myectomy, as demonstrated by Kobayashi et al. [16]. It is thus possible that myocyte disarray is related to a abnormal ventricular architecture that predisposes to worsening regional LV function. Saito et al. [17] showed that global longitudinal strain might provide useful information regarding myocardial fibrosis [correlating with late gadolinium enhancement (LGE) at CMR] and cardiac events in HCM patients with normal systolic function. Strain imaging of the LA allows for a more direct assessment of LA function. LA longitudinal function, quantified using TDI and 2D strain in HCM patients, was reduced compared with non-HCM patients with LV hypertrophy due to other conditions, as well as with healthy controls [18].

The role of 3D speckle-tracking echocardiography has also been evaluated in HCM. In particular, in the study by Baccouche et al. [19] comparing cardiac amyloidosis (CA) and HCM, basal radial strain was significantly reduced in the former condition (Fig. 11.3). Moreover, in HCM, 3D speckle-tracking parameters showed a remarkably weaker correlation with LGE compared with individuals with CA. This is most likely explained by the focal character of fibrosis, which may be less accessible for 3D strain imaging compared with amyloid changes.

Another significant advancement in the field of echocardiography is the development and refinement of 3D echocardiography, which can provide insights into mechanics of LV obstruction, LV architecture, and mitral and aortic structure and function. One major advantage of 3D echocardiography is the improved accuracy in evaluating cardiac chamber volumes by eliminating the need for geometric modeling and the errors caused by foreshortened apical views [20].

One of the most common features of HCM is LV obstruction, which is often complex in nature, involving MV leaflets, papillary muscles, and the hypertrophied septum [21]. As demonstrated by Song et al. [22

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