American journal of physiology. Heart and circulatory physiology
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Am. J. Physiol. Heart Circ. Physiol. · Dec 2009
Comparative StudyRight ventricular free wall pacing improves cardiac pump function in severe pulmonary arterial hypertension: a computer simulation analysis.
In pulmonary arterial hypertension (PAH), duration of myofiber shortening is prolonged in the right ventricular (RV) free wall (RVfw) compared with that in the interventricular septum and left ventricular free wall. This interventricular mechanical asynchrony eventually leads to right heart failure. We investigated by computer simulation whether, in PAH, early RVfw pacing may improve interventricular mechanical synchrony and, hence, cardiac pump function. ⋯ Time courses of circumferential strain in the ventricular walls as simulated were similar to the ones measured in healthy subjects (uniform strain patterns) and in PAH patients (prolonged RVfw shortening). When simulating pacing in decompensated PAH, RV pump function was best upon 40-ms RVfw preexcitation, as evidenced by maximal decrease of RV end-diastolic volume, reduced RVfw myofiber work, and most homogeneous distribution of workload over the ventricular walls. Thus our simulations indicate that, in decompensated PAH, RVfw pacing may improve RV pump function and may homogenize workload over the ventricular walls.
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Am. J. Physiol. Heart Circ. Physiol. · Dec 2009
RC time constant of single lung equals that of both lungs together: a study in chronic thromboembolic pulmonary hypertension.
The product of resistance, R, and compliance, C (RC time), of the entire pulmonary circulation is constant. It is unknown if this constancy holds for individual lungs. We determined R and C in individual lungs in chronic thromboembolic pulmonary hypertension (CTEPH) patients where resistances differ between both lungs. ⋯ Total RC time was 0.49+/-0.2 s, and RC times for the LF and HF lung were 0.45+/-0.2 and 0.45+/-0.1 s, respectively, not different. Proximal arterial compliance, given by the sum of main, right, and left PA compliances, was only 19% of total lung compliance. The RC time of a single lung equals that of both lungs together, and pulmonary arterial compliance comes largely from the distal vasculature.
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Am. J. Physiol. Heart Circ. Physiol. · Dec 2009
Comparative StudyMyocardial reperfusion injury management: erythropoietin compared with postconditioning.
Ischemic postconditioning (IPost) and erythropoietin (EPO) have been shown to attenuate myocardial reperfusion injury using similar signaling pathways. The aim of this study was to examine whether EPO is as effective as IPost in decreasing postischemic myocardial injury in both Langendorff-isolated-heart and in vivo ischemia-reperfusion rat models. Rat hearts were subjected to 25 min ischemia, followed by 30 min or 2 h of reperfusion in the isolated-heart study. ⋯ Second, in vivo, IPost and EPO induced an infarct size reduction compared with control (40.5+/-3.6% and 28.9+/-3.1%, respectively, vs. 53.7+/-4.3% of the area at risk; P<0.05). Again, EPO decreased significantly more infarct size and transmurality than IPost (P<0.05). In conclusion, with the use of our protocols, EPO showed better protective effects than IPost against reperfusion injury through higher phosphorylation of GSK-3beta.