Left Ventricular Discoordination Index Measured by Speckle Tracking Strain Rate Imaging Predicts Reverse Remodelling and Survival After Cardiac Resynchronization Therapy
Abstract Aims This study aimed to evaluate the predictive value of a baseline speckle tracking strain rate imaging-derived discoordination index for response to cardiac resynchronization therapy (CRT). Methods and results Ninety-seven patients with QRS ≥120 ms and left ventricular (LV) ejection fraction ≤35% were prospectively followed after CRT in the Mayo CRT Registry. The LV discoordination index (stretch/shortening or thinning/thickening during ejection) was calculated from three types of deformation, radial, circumferential, and longitudinal, using two-dimensional speckle tracking strain rate imaging. The benefit of CRT was evaluated by reverse remodelling (i.e. reduction of LV end-systolic volume ≥15% at 6-month follow-up) and survival. The optimal cut-off value of the baseline discoordination index in discriminating responders from non-responders was determined by receiver operating characteristic curve analysis. Significant differences in baseline indices between responders and non-responders were noted for radial and circumferential discoordination indices. A mid-ventricular radial discoordination index (RDI-M) >38% best predicted responders, especially in patients with ischaemic cardiomyopathy (area under the curve 0.86 for all patients, sensitivity 80%, and specificity 91%). Death occurred in 28 patients over a median follow-up of 3.2 years. When adjusted for confounding variables, lack of significant discoordination (RDI-M <38%) before CRT was associated with a particularly high mortality (hazard ratio 7.05, 95% confidence interval 2.45–26.0). Conclusion LV discoordination assessed by speckle tracking RDI-M imaging was able to predict reverse remodelling at 6 months and survival of patients who received CRT.
Background The etiology of carpal tunnel syndrome (CTS) remains idiopathic in many cases. Noninflammatory fibrosis of the subsynovial connective tissue (SSCT) within the carpal tunnel is common in CTS, and some clinicians have hypothesized that this fibrosis might be a cause rather than an effect of CTS. An animal model in which to test this hypothesis would be useful. The principal objective of this study was to investigate the effect of a surgical injury on SSCT fibrosis and median nerve function within the carpal tunnel in an in vivo rabbit model. Methods Rabbits were sacrificed 12 weeks after surgery and were evaluated by mechanical testing, histology, transmission and scanning electron microscopy, and electrophysiology. Results SSCT fibroblast density ( p<0.0001) and collagen fiber size ( p=0.0004) were significantly higher, and the median nerve distal motor amplitude was significantly lower ( p=0.0018), in the tendon injury group SSCT than in either the sham or control groups. Conclusions Our findings are similar to those seen in patients with carpal tunnel syndrome and suggest that the tendon injury procedure may be the basis of a new animal model of SSCT injury and, possibly, CTS.