Postoperative myocardial fibrosis assessment in aortic valvular heart diseases-a cardiovascular magnetic resonance study.

AIMS: Left ventricular remodelling occurs during the chronic course of aortic regurgitation (AR) and aortic stenosis (AS), leading to myocardial hypertrophy and fibrosis. Several studies have shown that extracellular volume fraction (ECV) and indexed extracellular volume (iECV) are important surrogate markers of diffuse myocardial fibrosis (MF). Postoperative data on these cardiovascular magnetic resonance (CMR) extracellular expansion parameters for either AS or AR are scarce. This study aimed to demonstrate the postoperative changes that occur in diffuse MF, and the influence of preoperative MF on the reversal of LV remodelling, in patients with AR or AS. METHODS AND RESULTS: Patients with severe AR or AS and indications for surgery were prospectively enrolled. Patients underwent pre- and postoperative CMR, and ECV and iECV were quantified. Data from 99 patients were analysed (32 with AR and 67 with AS). After surgery, the left ventricle mass index decreased in both groups (AR: 110 vs. 91 g/m2; AS: 86 vs. 68 g/m2, both P < 0.001). The late gadolinium enhancement fraction (AR: preoperative 1.9% vs. postoperative 1.7%, P = 0.575; AS: preoperative 2.4% vs. postoperative 2.4%, P = 0.615) and late gadolinium enhancement mass (AR: preoperative 3.8 g vs. postoperative 2.5 g, P = 0.635; AS: preoperative 3.4 g vs. postoperative 3.5 g, P = 0.575) remained stable in both groups. Preoperative iECV and ECV were greater in the AR group (iECV: 30 mL/m2 vs. 22 mL/m2, P = 0.001; ECV: 28.4% vs. 27.2%, P = 0.048). Indexed extracellular volume decreased after surgery in both groups (AR: 30-26.5 mL/m2, AS: 22-18.2 mL/m2, both P < 0.001); it was still greater in the AR group (AR: 26.5 mL/m2 vs. AS: 18.2 mL/m2, P < 0.001). Postoperative ECV remained stable in the AR group (preoperative 28.4% vs. postoperative 29.9%; P = 0.617) and increased in the AS group (preoperative 27.2% vs. postoperative 28.6%; P = 0.033). CONCLUSION: Patients with both AR or AS presented reduction in iECV after surgery, unfolding the reversible nature of diffuse MF. In contrast to patients with AS, those with AR developed postoperative iECV regression with stable ECV, suggesting a balanced reduction in both intracellular and extracellular myocardial components.

Closed- and open-state models of human skeletal muscle sodium channel.

Voltage-gated sodium channels play important roles in human physiology. However, their complexity hinders the understanding of their physiology and pathology at atomic level. We took advantage of the structural reports of similar channels obtained by cryo-EM (EeNav1.4, and NavPaS), and constructed models of human Nav1.4 channels at closed and open states. The open-state model is very similar to the recently published cryo-EM structure of hNav1.4. The comparison of both models shows shifts of the voltage sensors (VS) of DIII and DIV. The activated position of VS-DII in the closed model was demonstrated by Ts1 docking, thereby confirming the requirement that VS-DI, VS-DII and VS-DIII must be activated for the channel to open. The interactions observed with VS-DIII suggest a stepwise, yet fast, transition from resting to activated state. These models provide structural insights on the closed-open transition of the channel.

Atenolol blunts blood pressure increase during dynamic resistance exercise in hypertensives.

AIMS: This study was conducted to determine whether atenolol was able to decrease BP level and mitigate BP increase during dynamic resistance exercise performed at three different intensities in hypertensives. METHODS: Ten essential hypertensives (systolic/diastolic BP between 140/90 and 160/105mmHg) were blindly studied after 6 weeks of placebo and atenolol. In each phase, volunteers executed, in a random order, three protocols of knee-extension exercises to fatigue: (i) one set at 100% of 1RM; (ii) three sets at 80% of 1RM; and (iii) three sets at 40% of 1RM. Intra-arterial radial blood pressure was measured throughout the protocols. RESULTS: Atenolol decreased systolic BP maximum values achieved during the three exercise protocols (100% = 186 ± 4 vs. 215 ± 7, 80% = 224 ± 7 vs. 247 ± 9 and 40% = 223 ± 7 vs. 252 ± 16mmHg, P < 0.05). Atenolol also mitigated an increase in systolic BP in the first set of exercises (100% =+38 ± 5 vs.+54 ± 9; 80% =+68 ± 11 vs. +84 ± 13 and 40% =+69 ± 7 vs.+84 ± 14, mmHg, P < 0.05). Atenolol decreased diastolic BP values and mitigated its increase during exercise performed at 100% of 1RM (126 ± 6 vs. 145 ± 6 and +41 ± 6 vs.+52 ± 6, mmHg, P < 0.05), but not at the other exercise intensities. CONCLUSIONS: Atenolol was effective in both reducing systolic BP maximum values and mitigating BP increase during resistance exercise performed at different intensities in hypertensive subjects.