General Introduction and Thesis Outline | 15 the cardiac cycle. Changes are expressed in percentages of lengthening or shortening over time and referred to as myocardial strain (Figure 2). Reproducibility of deformation imaging is superior compared to multiple conventional functional measures. Besides, it is more robust compared to visual assessment of regional wall motion abnormalities, which is especially challenging in the thin walled RV and highly dependent on experience of the observer. When compared to other high-end imaging modalities, the non-invasive nature, low cost and wide availability of echocardiographic deformation imaging are important advantages for routine clinical practice. Figure 2. Echocardiographic speckle tracking deformation imaging In the left ventricle, ventricular wall motion is tracked in the apical long axis (APLAX) view, the apical 4-chamber (4CH) and apical 2-chamber (2CH) view. In the right ventricle (RV), the free wall is tracked in an RV-focused 4CH view. The aortic valve closure (AVC) and pulmonic valve closure (PVC) mark the end of the systole. Longitudinal strain is expressed in percentages of lengthening or shortening over time. Longitudinal strain is displayed for 18 LV segments and for 3 RV free wall segments. Systolic peak strain is the peak negative strain occurring up to the moment of valve closure. Previous studies have repeatedly demonstrated the potential value of deformation imaging in ARVC. It was demonstrated that this technique may help to reveal early disease manifestation in desmosomal genetic variant carriers without an overt ARVC phenotype.12,20,21 One study from our own institute identified characteristic deformation patterns in the subtricuspid segment of the RV free wall, known as the first affected region in ARVC. These abnormal patterns were seen in half of the genetic variant carriers without overt signs of disease by conventional diagnostics.12 The CircAdapt model, a computer simulation model of the heart and circulation developed at Maastricht University, was used to link deformation abnormalities to a possible underlying disease substrate of reduced contractility and increased stiffness (Figure 3). The abnormal deformation pattern with delayed onset to shortening, reduced peak strain and post-systolic shortening was a robust finding22 which turned out to be a precursor of disease progression.23 1
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