Surgical ventricular restoration in our study has clearly demonstrated a positive effect on LV geometry.
The study by Khoo et al. (1) and the subsequent editorial (2) were read with great enthusiasm and some sense of skepticism. The study comes from 2 well-known pediatric cardiac centers, and the surgical results of the study appear to be commendable. But the authors' conclusion of systemic right ventricle (RV) with an "LV [left ventricular] like contraction" pattern appears to be too much of a generalization and may be far from the target and truth. It is akin to a "pot-bellied" individual trying to do a ballet dance or a computer trying to get emotional intelligence. When we consider the differences between the RV and LV with regard to embryology, anatomy, physiology, and hemodynamics (3-5), it is inconceivable that the RV could adapt to an LV type of contraction. An RV without a middle, circular layer of muscle fibers and without twist or torsion, translation, or radial thickening cannot be compared with the LV.In the RV, the anatomy of the conus (infundibulum), the "mighty midget" of Van Pragh et al. (6) that is absent in the LV, deserves due consideration while the function of the RV is evaluated by any imaging technique. The unique blood supply pattern (7,8) and the importance of the interventricular septum cannot be underestimated. The extreme difficulty of getting the RV in a 4-chamber view is well appreciated. In the example given, Figure 2, a reasonable image was obtained; it is intriguing that the septum was convex toward the systemic RV. It is interesting to note how far the septum is functionally incorporated into the RV for its systolic function.A comparison of the pathological data from 3 patients dying within 1 month of the Norwood/Sano palliation with those from the 7 patients dying within the interstage period may throw light on some of the changes in the RV muscle, specially the "circumferential fibers" running parallel to the atrioventricular groove merging with the superficial fibers of the LV (9) and the changes in the conus muscularis. The different patterns of coronary supply may explain the ischemic theory (the post-systolic strain) observed by the researchers. In the mechanism of RV contraction, apart from the inward movement of the free wall ("bellow effect") and the contraction of the longitudinal fibers, the traction of the free wall at the points of attachment to the LV needs to be considered (10).The LV, however small in hypoplastic left heart syndrome, may have a role to play in RV function. Ventricular interdependence cannot be underestimated.Not withstanding the above considerations, speckle track images to study the RV strain, strain rate, and contraction synchrony will be a great boon to follow up the surgically corrected "little wonders." Powerful imagination is needed to conceive of an RV that can adapt like the LV. At this stage of understanding, we can only have guarded optimism and expectation for the continued performance of the systemic ventricle. The RV adapts better to volume overload than to pressure overload; gradually the RV shows decreased systolic reserve and low ca...
The article 'Assessment of left ventricular systolic function by vector velocity imaging' by Narayanan et al 1 was read with enthusiasm. The authors have studied 49 patients (mentioned only in the abstract). The authors' introduction to the relatively new technique of vector velocity imaging (VVI) falls short of expectation for an average reader. One may get the impression that VVI is mainly used to calculate the ejection fraction (EF), whereas its mainstay is objective quantification of multidirectional components of left ventricular (LV) deformation and fairly accurate assessment of regional and global function by various parameters like strain, strain rate, and twist characteristics.Calculation of EF by VVI may have theoretical and practical limitations. The usual methods of calculation of EF by 2D/3D echocardiography or magnetic resonance imaging, nuclear scintigraphy and conventional LV angiogram, are volume dependant calculation, and if done meticulously, are a reliable index of LV function. On the contrary, calculation of EF by VVI is based on velocity and movement of the myocardium i.e. by spatial dislocation and deformation of the myocardium (leave alone Langrangian or Eulerian concepts). Let us not compare and confuse the EF calculated by two entirely different methodologies giving us another set of values, to which we have to add a "correction factor" (probably variable correction values for various levels of LV dysfunction).The editorial regarding the article has given a fair update on VVI and its applications, however it has missed the main theme of the article by Narayanan et al. It has not elaborated the short comings of the article. 2 In the future, it is likely that EF will still continue to be the most frequently used parameter for LV function for cardiologists, cardiac surgeons and research workers. However the parameters available from VVI may become more useful for decision making for therapeutic and surgical purposes. Global LV longitudinal strain has been well validated as a reliable quantitative index of global LV function and may be in the forefront as an alternative for EF. 3 It may become the "throned monarch better than his crown". 4 Only time will unravel the future. Prophesy is difficult especially about the future! DisclaimerThe authors have no relationships to disclose. They have not received any support in the form of grants or other. r e f e r e n c e s
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