Background-Experimental studies suggest that the interval between peak and end of T wave (Tpe) in transmural ECGs reflects transmural dispersion of repolarization (TDR), which is amplified by ␤-adrenergic stimulation in the LQT1 model. In 82 patients with genetically identified long-QT syndrome (LQTS) and 33 control subjects, we examined T-wave morphology and various parameters for repolarization in 12-lead ECGs including corrected QT (QTc; QT/R-R 1/2 ) and corrected Tpe (Tpec; Tpe/R-R 1/2 ) before and during exercise stress tests. Methods and Results-Under baseline conditions, LQT1 (nϭ51) showed 3 cardinal T-wave patterns (broad-based, normal-appearing, late-onset) and LQT2 (nϭ31) 3 patterns (broad-based, bifid with a small or large notch). The QTc and Tpec were 510Ϯ68 ms and 143Ϯ53 ms in LQT1 and 520Ϯ61 ms and 195Ϯ69 ms in LQT2, respectively, which were both significantly larger than those in control subjects (402Ϯ36 ms and 99Ϯ36 ms). Both QTc and Tpec were significantly prolonged during exercise in LQT1 (599Ϯ54 ms and 215Ϯ46 ms) with morphological change into a broad-based T-wave pattern. In contrast, exercise produced a prominent notch on the descending limb of the T wave, with no significant changes in the QTc and Tpec (502Ϯ82 ms and 163Ϯ86 ms: nϭ19) in LQT2. Conclusions-Tpe interval increases during exercise in LQT1 but not in LQT2, which may partially account for the finding that fatal cardiac events in LQT1 are more often associated with exercise.

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The sympathetic baroreflex is an important feedback system in stabilization of arterial pressure. This system can be decomposed into the controlling element (mechanoneural arc) and the controlled element (neuromechanical arc). We hypothesized that the intersection of the two operational curves representing their respective functions on an equilibrium diagram should define the operating point of the arterial baroreflex. Both carotid sinuses were isolated in 16 halothane-anesthetized rats. The vagi and aortic depressor nerves were cut bilaterally. Carotid sinus pressure (CSP) was sequentially altered in 10-mmHg increments from 80 to 160 mmHg while sympathetic efferent nerve activity (SNA) and systemic arterial pressure (SAP) were recorded simultaneously under various hemorrhagic conditions. The mechanoneural arc was characterized by the response of SNA to CSP and the neuromechanical arc by the response of SAP to SNA. We parametrically analyzed the relationship between input and output for each arc using a four-parameter logistic equation model. In baseline states, the two arcs intersected each other at the point at which the instantaneous gain of each arc attained its maximum. Severe hemorrhage lowered the gain and offset of the neuromechanical arc and moved the operating point, whereas the mechanoneural arc remained unchanged. The operating points measured under the closed-loop conditions were indistinguishable from those estimated from the intersections of the two arc curves on the equilibrium diagram. The average root mean square errors of estimate for arterial pressure and SNA were 2 and 3%, respectively. Such an analytic approach could explain a mechanism for the determination of the operating point of the sympathetic baroreflex system and thus helps us integratively understand its function.

Aim:The effects of exercise intervention and to assess its long-term efficacy in preventing subsequent cardiovascular events in patients with type 2 diabetes were little known on randomized controlled trial. Methods: Thirty-eight type 2 diabetic patients (21 men and 17 women) were assigned to either the exercise group (n 21) or the control group without exercise training (n 17) by simple randomization. The exercise training group was scheduled for aerobic and resistance exercise programs for 3 months. After the 3-month, we investigated endothelial function, insulin resistance, adipocytokines and inflammatory markers. The endothelial function was evaluated by examining a flow-mediated endothelium-dependent vasodilatation (FMD). Furthermore, we followed the incidence of cardiovascular events for 24 months. Results: After 3-month, HbA1C was decreased significantly in both groups. FMD was increased from 7.3 4.7% to 10.9 6.2% only in the exercise group ( p 0.05). Long-term follow-up data showed that the control group developed cardiovascular events more frequently than did the exercise group ( p 0.05). Conclusions: Exercise improves endothelial dysfunction independently of glycemic control and insulin sensitivity in patients with type 2 diabetes. The beneficial effects of 3-month exercise to reduce cardiovascular events persist for 24 months. J Atheroscler Thromb, 2010; 17:828-833.

Our findings suggest that Na+ channel blockers amplify existing I(Na) and possibly other ion channel defects, with a potency inversely proportional to the rate of dissociation of the drug from the Na+ channel, thus causing a prominent elevation of the ST segment and, in some cases, prolongation of QRS duration in patients with Brugada syndrome.