American journal of physiology. Heart and circulatory physiology
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Am. J. Physiol. Heart Circ. Physiol. · Apr 2004
Effects of left ventricular contractility and coronary vascular resistance on coronary dynamics.
Wave-intensity analysis, which separates upstream from downstream events and defines their interaction, has been used to study the effects of changes in left ventricular (LV) contractility (E(max)) and left circumflex coronary artery resistance (R(LCx)) on the coronary systolic flow impediment (CSFI). In 10 anesthetized, open-chest dogs, we measured coronary, aortic, and LV pressures, coronary velocity (Flowire), and flow. ⋯ I(W-) was proportional to the CSFI. We conclude that contractility and coronary resistance change CSFI by modulating the backward-going compression wave.
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Am. J. Physiol. Heart Circ. Physiol. · Mar 2004
Clinical TrialInhibition of nitric oxide synthase does not alter dynamic cerebral autoregulation in humans.
The aim of this study was to determine whether inhibition of nitric oxide synthase (NOS) alters dynamic cerebral autoregulation in humans. Beat-to-beat blood pressure (BP) and cerebral blood flow (CBF) velocity (transcranial Doppler) were measured in eight healthy subjects in the supine position and during 60 degrees head-up tilt (HUT). NOS was inhibited by intravenous NG-monomethyl-L-arginine (L-NMMA) infusion. ⋯ However, transfer function gain remained unchanged. During tilt with L-NMMA, changes in steady-state hemodynamics and BP and CBF velocity variability as well as transfer gain and phase were similar to those without L-NMMA. These data suggest that inhibition of tonic production of NO does not appear to alter dynamic cerebral autoregulation in humans.
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Am. J. Physiol. Heart Circ. Physiol. · Mar 2004
Interaction between prostanoids and nitric oxide in regulation of systemic, pulmonary, and coronary vascular tone in exercising swine.
Prostacyclin and nitric oxide (NO) are produced by the endothelium in response to physical forces such as shear stress. Consequently, both NO and prostacyclin may increase during exercise and contribute to metabolic vasodilation. Conversely, NO has been hypothesized to inhibit prostacyclin production. ⋯ In conclusion, endogenous prostanoids contribute importantly to systemic and coronary tone in awake swine at rest but are not mandatory for exercise-induced vasodilation in these beds. Endogenous prostanoids are not mandatory for the regulation of pulmonary resistance vessel tone. Finally, NO blunts the contribution of prostanoids to vascular tone regulation in the systemic but not in the coronary and pulmonary beds.
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Am. J. Physiol. Heart Circ. Physiol. · Mar 2004
Impact of acute hypoxic pulmonary hypertension on LV diastolic function in healthy mountaineers at high altitude.
In pulmonary hypertension right ventricular pressure overload leads to abnormal left ventricular (LV) diastolic function. Acute high-altitude exposure is associated with hypoxia-induced elevation of pulmonary artery pressure particularly in the setting of high-altitude pulmonary edema. Tissue Doppler imaging (TDI) allows assessment of LV diastolic function by direct measurements of myocardial velocities independently of cardiac preload. ⋯ This acute increase in pulmonary artery pressure led to a change in LV diastolic function that was directly correlated with the severity of pulmonary hypertension. However, in contrast to patients suffering from some form of cardiopulmonary disease and pulmonary hypertension, in these healthy subjects, overt LV diastolic dysfunction was not observed because it was prevented by augmented atrial contraction. We propose the new concept of compensated diastolic (dys)function.
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Am. J. Physiol. Heart Circ. Physiol. · Mar 2004
Role of cyclooxygenase in ventricular effects of adrenomedullin: is adrenomedullin a double-edged sword in sepsis?
Adrenomedullin (ADM) is upregulated in cardiac tissue under various pathophysiological conditions. However, the direct inotropic effect of ADM on normal and compromised cardiomyocytes is not clear. In rat ventricular myocytes, ADM produced an initial (<30 min) increase in cell shortening and Ca(2+) transient and, on prolonged incubation (>1 h), a marked decrease in cell shortening and Ca(2+) transient. ⋯ Indomethacin, SC-236, and tranylcypromine restored cell contractility and the decrease in Ca(2+) transient, whereas SQ-29548 had no effect, implying that prostacyclin played a role in both effects. However, with regard to cell-shortening kinetics, indomethacin and SQ-29548 decreased the amount of time taken by the cells to return to baseline, whereas SC-236 and tranylcypromine did not, implying that not only prostacyclin, but also thromboxane, is involved. The results indicate that ADM interacts with COX to yield prostanoids, which mediate its negative inotropic effect in LPS-treated rat ventricular myocytes.