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      The Spatial QRS-T Angle: Implications in Clinical Practice

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          Abstract

          The ventricular gradient (VG) as a concept was conceived in the 1930s and its calculation yielded information that was not otherwise obtainable. The VG was not utilized by clinicians at large because it was not easy to understand and its computation time-consuming. The contemporary spatial QRS-T angle is based on the concept of the VG and defined as its mathematical and physiological integral. Its current major clinical use is to assess the cardiac primary repolarization abnormalities in 3-dimensional spatial vectorial plans which are normally untraced in the presence of secondary electrophysiological activity in a 2-dimensional routine electrocardiogram (ECG). Currently the calculation of the spatial QRS-T angle can be easily computed on the basis of a classical ECG and contributes to localization of arrhythmogenic areas in the heart by assessing overall and local heterogeneity of the myocardial ventricular action potention duration. Recent population-based studies suggest that the spatial QRS-T angle is a dominant ECG predictor of future cardiovascular events and death and it is superior to more conventional ECG parameters. Its assessment warrants consideration for intensified primary and secondary cardiovascular prevention efforts and should be included in everyday clinical practice. This review addresses the nature and diagnostic potential of the spatial QRS-T angle. The main focus is its role in ECG assessment of dispersion of repolarization, a key factor in arrythmogeneity.

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          Most cited references 138

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          National study of physician awareness and adherence to cardiovascular disease prevention guidelines.

          Few data have evaluated physician adherence to cardiovascular disease (CVD) prevention guidelines according to physician specialty or patient characteristics, particularly gender. An online study of 500 randomly selected physicians (300 primary care physicians, 100 obstetricians/gynecologists, and 100 cardiologists) used a standardized questionnaire to assess awareness of, adoption of, and barriers to national CVD prevention guidelines by specialty. An experimental case study design tested physician accuracy and determinants of CVD risk level assignment and application of guidelines among high-, intermediate-, or low-risk patients. Intermediate-risk women, as assessed by the Framingham risk score, were significantly more likely to be assigned to a lower-risk category by primary care physicians than men with identical risk profiles (P<0.0001), and trends were similar for obstetricians/gynecologists and cardiologists. Assignment of risk level significantly predicted recommendations for lifestyle and preventive pharmacotherapy. After adjustment for risk assignment, the impact of patient gender on preventive care was not significant except for less aspirin (P<0.01) and more weight management recommended (P<0.04) for intermediate-risk women. Physicians did not rate themselves as very effective in their ability to help patients prevent CVD. Fewer than 1 in 5 physicians knew that more women than men die each year from CVD. Perception of risk was the primary factor associated with CVD preventive recommendations. Gender disparities in recommendations for preventive therapy were explained largely by the lower perceived risk despite similar calculated risk for women versus men. Educational interventions for physicians are needed to improve the quality of CVD preventive care and lower morbidity and mortality from CVD for men and women.
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            Long-term clinical course of patients after termination of ventricular tachyarrhythmia by an implanted defibrillator.

            The implanted cardioverter defibrillator (ICD) improves survival in high-risk cardiac patients. This analysis from the MADIT-II trial database examines the long-term clinical course and subsequent mortality risk of patients after termination of life-threatening ventricular tachyarrhythmias by an ICD. Life-table survival analysis was performed, and proportional hazards regression analysis was used to evaluate the contribution of baseline clinical factors and time-dependent defibrillator therapy to mortality during long-term follow-up. Of 720 patients with an ICD (average follow-up 21 months), 169 patients received 701 antiarrhythmic device therapies for ventricular tachyarrhythmias. Few baseline characteristics distinguished patients who received appropriate ICD therapy for their first ventricular tachyarrhythmic episode. The probability of survival for at least 1 year after first therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF) was 80%. The hazard ratios for the risk of death due to any cause in those who survived appropriate therapy for termination of VT and VF were 3.4 (P<0.001) and 3.3 (P=0.01), respectively, compared with those who survived without receiving ICD therapy, with a high frequency of heart failure and late nonsudden cardiac death after first successful ICD therapy for VF. Successful appropriate therapy by an ICD for VT or VF is associated with 80% survival at 1 year after arrhythmia termination. These patients are at increased risk for heart failure and nonsudden cardiac death after device termination of VT or VF and should receive special attention for the prevention and management of progressive left ventricular dysfunction during long-term follow-up.
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              Cycle length dependence of human action potential duration in vivo. Effects of single extrastimuli, sudden sustained rate acceleration and deceleration, and different steady-state frequencies.

              Using a new method for long-term recording of monophasic action potentials from the human heart, we studied in 17 patients the effects on ventricular action potential duration (APD) of three clinically pertinent cycle length perturbations: (1) single extrastimuli, (2) abrupt sustained rate acceleration and deceleration, and (3) different steady-state cycle lengths. Results were: (a) APD after single extrastimuli at progressively longer cycle lengths were related to the extrastimulus cycle length with a biphasic electrical restitution curve which after an initial steep rise and a subsequent transient descent rose again more gradually to a plateau at cycle lengths above 800-1,000 ms. (b) After a sustained step decrease in cycle length, the first APD shortened abruptly while final steady-state adaptation required up to several minutes. The transition between the rapid and slow phase of APD change was characterized by a variable alternans of APD which correlated inversely with the preceding diastolic interval. (c) In the steady state, APD correlated linearly with cycle length, increasing an average of 23 ms per 100 ms cycle length increase (r = 0.995). The divergence between steady-state and non-steady-state APD, and the slowness of steady-state adaptation, are important factors to be considered in clinical electrophysiologic studies and in rate correction algorithms of APD or QT intervals, respectively.
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                Author and article information

                Journal
                Curr Cardiol Rev
                Curr Cardiol Rev
                CCR
                Current Cardiology Reviews
                Bentham Science Publishers
                1573-403X
                1875-6557
                August 2013
                August 2013
                : 9
                : 3
                : 197-210
                Affiliations
                [1 ]First Department of Propaudeutic Internal Medicine, “Laiko” General Hospital, Athens University Medical School, Athens, Greece;
                [2 ]3rd Department of Internal Medicine, Athens General Regional Hospital “G. Gennimatas”, Athens, Greece;
                [3 ]Diabetes Research Unit, Sheffield Teaching Hospitals, University of Sheffield, Sheffield, UK
                Author notes
                [* ]Address correspondence to this author at the 24 Olenou Street, 11562 Athens, Greece; Tel: +30 210 8818539; Fax: +302108839713; E-mail: c_v_24@ 123456yahoo.gr
                Article
                CCR-9-197
                10.2174/1573403X113099990031
                3780345
                23909632
                © 2013 Bentham Science Publishers

                This is an open access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.5/), which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.

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