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Objectives: To predict the QT interval in the presence of normal QRS for patients with left bundle branch block (LBBB).Background: There is no acceptable method for simple and reliable QT correction for patients with bundle branch block (BBB).Methods: We measured the QT interval in patients with new onset LBBB who had a recent electrocardiogram with narrow QRS for comparison. 48 patients who developed in-hospital LBBB were studied. Patients who had similar heart rate before and after LBBB were included. We used linear regression, the Bogossian method, and our new fixed QRS replacement method to evaluate the most reliable correction method.Results: JTc (QTc-QRS) interval was preserved before and after LBBB (328.9 ± 25.4 ms before LBBB vs. 327.3 ms post LBBB (p = 0.550). Mean predicted preLBBB QTc difference was 1.3 ms, -21.3 ms and 1.6 ms for the three methods respectively (p < 0.001 for Bogossian comparison with the other methods). Coefficients of correlation (R) between actual preLBBB QTc with predicted preLBBB QTc were 0.707, 0.683 and 0.665 respectively (p > 0.3 for R comparisons between all methods). The average absolute difference in preLBBB QTc was 15.5 ms and 16.7 ms for the regression and fixed-gender methods (p value between the two = 0.321) and 25.5 ms for the Bogossian method, which was found to be significantly underperforming.Conclusions: In patients with LBBB, replacing of the QRS duration after deriving the QTc interval with a fixed value of 88 ms for female and 95 ms for male provides a simple and reliable method for predicting the QTc before the development of LBBB. [ABSTRACT FROM AUTHOR]

Background The Norton scale is traditionally used to assess the risk of pressure ulcers. However, recent studies have shown its prognostic utilization in elderly patients with diverse medical conditions. The association between low admission Norton scale scores (ANSS), complications, and mortality in elderly patients following trans-catheter aortic valve implantation (TAVI) has never been studied. We aimed to determine if low ANSS (≤16) is associated with complications and 30-day and 1-year mortality in elderly patients undergoing TAVI. Methods The medical charts of elderly (≥70 years) TAVI patients at the Tel-Aviv Medical Center, a tertiary medical center, were studied for the following measurements: ANSS, demographics, co-morbidities, complications during hospitalization, and 30-day and 1-year mortality. Complications included: an atrio-ventricular block, stroke, and vascular complications. Results The cohort included 302 elderly patients: 179 (59.3%) were women; the mean age was 83.3 ± 5.1 years. Following TAVI, 112 (37.1%) patients had complications other than pressure ulcers, 10 (3.3%) patients died within 30 days, and 42 (13.9%) patients died within one year. Overall, 36 (11.9%) patients had low ANSS. 1-year mortality rates were almost three times higher in patients with low ANSS relative to patients with high ANSS (27.8% vs. 12.0%; the relative risk 1.1; p = 0.018). A stepwise logistic regression analysis showed that ANSS was independently inversely associated with 1-year mortality ( p = 0.018). Complications and 30-day mortality rates were similar in both groups. Conclusions Low ANSS are associated with 1-year mortality after TAVI. The Norton scale may therefore be used as an additional tool for elderly patient selection before TAVI. [ABSTRACT FROM AUTHOR]

Background Two important causes of sudden death during endurance races are arrhythmic death and heat stroke. However, "arrhythmic death" has caught practically all the attention of the medical community whereas the importance of heat stroke is less appreciated. Objectives The study sought to determine what percentage of life-threatening events during endurance races are due to heat stroke or cardiac causes. Methods This retrospective study examined all the long distance popular races that took place in Tel Aviv from March 2007 to November 2013. The number of athletes at risk was known. The number of athletes developing serious sport-related events and requiring hospitalization was known. Life-threatening events were those requiring mechanical ventilation and hospitalization in intensive care units. Results Overall, 137,580 runners participated in long distance races during the study period. There were only 2 serious cardiac events (1 myocardial infarction and 1 hypotensive supraventricular tachyarrhythmia), neither of which were fatal or life threatening. In contrast, there were 21 serious cases of heat stroke, including 2 that were fatal and 12 that were life threatening. One of the heat stroke fatalities presented with cardiac arrest without previous warning. Conclusions In our cohort of athletes participating in endurance sports, for every serious cardiac adverse event, there were 10 serious events related to heat stroke. One of the heat stroke-related fatalities presented with unheralded cardiac arrest. Our results put in a different perspective the ongoing debate about the role of pre-participation electrocardiographic screening for the prevention of sudden death in athletes. [ABSTRACT FROM AUTHOR]

Cell replacement strategies are promising interventions aiming to improve myocardial performance. Yet, the electrophysiological impact of these approaches has not been elucidated. We assessed the electrophysiological consequences of grafting of two candidate cell types, that is, skeletal myoblasts and human embryonic stem cell-derived cardiomyocytes (hESC-CMs). The fluorescently labeled (DiO) candidate cells were grafted into the rat's left ventricular myocardium. Two weeks later, optical mapping was performed using the Langendorff-perfused rat heart preparation. Images were obtained with appropriate filters to delineate the heart's anatomy, to identify the DiO-labeled cells, and to associate this information with the voltage-mapping data (using the voltage-sensitive dye PGH-I). Histological examination revealed the lack of gap junctions between grafted skeletal myotubes and host cardiomyocytes. In contrast, positive Cx43 immunostaining was observed between donor and host cardiomyocytes in the hESC-CMs-transplanted hearts. Optical mapping demonstrated either normal conduction (four of six) or minimal conduction slowing (two of six) at the hESC-CMs engraftment sites. In contrast, marked slowing of conduction or conduction block was seen (seven of eight) at the myoblast transplantation sites. Ventricular arrhythmias could not be induced in the hESC-CM hearts following programmed electrical stimulation but were inducible in 50% of the myoblast-engrafted hearts. In summary, a unique method for assessment of the electrophysiological impact of myocardial cell therapy is presented. Our results demonstrate the ability of hESC-CMs to functionally integrate with host tissue. In contrast, transplantation of cells that do not form gap junctions (skeletal myoblats) led to localized conduction disturbances and to the generation of a proarrhythmogenic substrate. STEM CELLS 2010;28:2151-2161 [ABSTRACT FROM AUTHOR]

Human embryonic stem cells (hESC) are pluripotent lines that can differentiate in vitro into cell derivatives of all three germ layers, including cardiomyocytes. Successful application of these unique cells in the areas of cardiovascular research and regenerative medicine has been hampered by difficulties in identifying and selecting specific cardiac progenitor cells from the mixed population of differentiating cells. We report the generation of stable transgenic hESC lines, using lentiviral vectors, and single-cell clones that express a reporter gene (eGFP) under the transcriptional control of a cardiac-specific promoter (the human myosin light chain-2V promoter). Our results demonstrate the appearance of eGFP-expressing cells during the differentiation of the hESC as embryoid bodies (EBs) that can be identified and sorted using FACS (purity > 95%, viability>85%). The eGFP-expressing cells were stained positively for cardiac-specific proteins ( > 93%), expressed cardiac-specific genes, displayed cardiac-specific action-potentials, and could form stable myocardial cell grafts following in vivo cell transplantation. The generation of these transgenic hESC lines may be used to identify and study early cardiac precursors for developmental studies, to robustly quantify the extent of cardiomyocyte differentiation, to label the cells for in vivo grafting, and to allow derivation of purified cell populations of cardiomyocytes for future myocardial cell therapy strategies. [ABSTRACT FROM AUTHOR]

Focuses on the use of somatic gene and cell therapy strategies for the treatment of cardiac arrhythmia. Dependency of cardiac function on the appropriate timing and synchronization of the mechanical contraction in various regions of the heart. Definition of cardiac arrhythmia as any deviation from the normal pattern or rate of cardiac electric citation; Clinical management of rhythm disturbances; Electrophysiological effects of antiarrythmic drugs.

An abstract of the article "Refractory Period Prolongation by Fibroblasts Overexpressing the Mutant Kv1.3 H401W Channel in Computer Simulation and Pig Hearts," by Ariel Shabtay and colleagues is presented.

Background: Traditional antiarrhythmic pharmacological therapies are limited by their global cardiac action, low efficacy, and significant proarrhythmic effects. We present a novel approach for the modification of the myocardial electrophysiological substrate using cell grafts genetically engineered to express specific ionic channels., Methods and Results: To test the aforementioned concept, we performed ex vivo, in vivo, and computer simulation studies to determine the ability of fibroblasts transfected to express the voltage-sensitive potassium channel Kv1.3 to modify the local myocardial excitable properties. Coculturing of the transfected fibroblasts with neonatal rat ventricular myocyte cultures resulted in a significant reduction (68%) in the spontaneous beating frequency of the cultures compared with baseline values and cocultures seeded with naive fibroblasts. In vivo grafting of the transfected fibroblasts in the rat ventricular myocardium significantly prolonged the local effective refractory period from an initial value of 84+/-8 ms (cycle length, 200 ms) to 154+/-13 ms (P<0.01). Margatoxin partially reversed this effect (effective refractory period, 117+/-8 ms; P<0.01). In contrast, effective refractory period did not change in nontransplanted sites (86+/-7 ms) and was only mildly increased in the animals injected with wild-type fibroblasts (73+/-5 to 88+/-4 ms; P<0.05). Similar effective refractory period prolongation also was found during slower pacing drives (cycle length, 350 to 500 ms) after transplantation of the potassium channels expressing fibroblasts (Kv1.3 and Kir2.1) in pigs. Computer modeling studies confirmed the in vivo results., Conclusions: Genetically engineered cell grafts, transfected to express potassium channels, can couple with host cardiomyocytes and alter the local myocardial electrophysiological properties by reducing cardiac automaticity and prolonging refractoriness.