New Findings r What is the topic of this review?Studies a,contabs,longabsre reviewed showing that hypoxic pulmonary vasoconstriction and subsequent remodelling expose the right ventricle to increased afterload, and that this is occasionally a cause of high-altitude right heart failure. r What advances does it highlight?Non-invasive field studies have shown that hypoxic pulmonary hypertension limits exercise capacity in relationship to increased pulmonary artery pressures in high-altitude newcomers. This is compensated for by increased lung diffusing capacity, decreased ventilator response and polycythaemia in high-altitude inhabitants. There is recently reported echocardiographic evidence of altered right ventricular function at high altitudes at rest. These data need to be confirmed with measurements during exercise.Hypoxia causes pulmonary vasoconstriction. Regional hypoxic vasoconstriction improves the matching of perfusion to alveolar ventilation. Global hypoxic vasoconstriction increases right ventricular afterload. The hypoxic pulmonary pressor response is universal in mammals and in birds, but with considerable interspecies and interindividual variability. Chronic hypoxia induces pulmonary hypertension in proportion to initial vasoconstriction. Prolonged hypoxic exposure is also associated with an increase in red blood cell mass, which aggravates pulmonary hypertension by an increase in blood viscosity. Hypoxic pulmonary hypertension in humans is usually mild to moderate, but pulmonary vascular pressure-flow relationships are steep, which corresponds to a substantial afterload on the right ventricle during exercise. A partial recovery of 10-25% of the hypoxia-induced decrease in maximal oxygen uptake has been reported with intake-specific pulmonary vasodilating interventions. Hypoxia has been reported to decrease myocardial fibre contractility in vitro. However, the acutely hypoxic right ventricle remains able to preserve the coupling of its contractility to increased afterload in intact animals. Echocardiographic studies of the right ventricle in healthy hypoxic human subjects show altered diastolic function, but systolic function that is preserved or even increased acutely and slightly depressed chronically.
NotesOnline First articles must include the digital object identifier (DOIs) and date of initial publication. establish publication priority; they are indexed by PubMed from initial publication. Citations to may be posted when available prior to final publication Summary:Mitral regurgitation is a frequent finding in patients with aortic stenosis scheduled for aortic valve replacement. Detection of mitral regurgitation in such patients has important implications, as it can independently affect functional status and prognosis. When mitral regurgitation is moderate-to-severe, a decision to operate on both valves should only be made following a careful clinical and echocardiographic assessment. Indeed, double-valve surgery increases peri-and post-operative risks, and mitral regurgitation may improve spontaneously after isolated aortic valve replacement. Better understanding of the determinants of these changes appears particularly crucial in the light of recent advances in percutaneous aortic valve replacement. IntroductionAt the time of aortic valve replacement (AVR), many patients with aortic stenosis (AS) exhibit varying degrees of mitral regurgitation (MR). The aetiology of the MR is often functional in nature, occurring in the absence of any significant intrinsic valvular lesion. Increased afterload, left ventricular (LV) remodelling, fluid overload and concomitant ischaemic heart dysfunction may account for the development of functional MR. When there is intrinsic mitral valve disease, this may result from calcification of the mitral leaflets or annulus, particularly in the elderly, but also from rheumatic involvement, or from myxomatous degeneration. MR associated with AS should not be overlooked, as it can worsen functional status and independently affect prognosis. Moreover, a surgeon's decision to operate on both valves should only be made after careful clinical and echocardiographic assessment, because double-valve surgery increases the perioperative risk, and MR can improve spontaneously after isolated AVR. Greater awareness of the determinants of these changes appears particularly crucial in the light of recent advances in percutaneous AVR. In this article, we review current knowledge on the pathophysiology, incidence, and prognostic value of MR in severe AS, as well as the natural history of MR after isolated AVR.
Multivalvular heart disease is not an uncommon situation, but the paucity of data for each specific situation does not allow the proposal of a standardised, evidence-based management strategy. This paper aims at reviewing the available evidence on the management of multivalvular disease, taking into account the interactions between different valve lesions, the diagnostic pitfalls and the strategies that should be considered in the presence of multiple valvular disease.
There is evidence of morphological and functional abnormalities in FRDA patients with normal LVEF and mass.
Hypoxic exposure depresses myocardial contractility in vitro, but has been associated with indices of increased cardiac performance in intact animals and in humans, possibly related to sympathetic nervous system activation. We explored left ventricular (LV) function using speckle tracking echocardiography and sympathetic tone by spectral analysis of heart rate variability (HRV) in recently acclimatized lowlanders versus adapted or maladapted highlanders at high altitude. Twenty-six recently acclimatized lowlanders, 14 healthy highlanders and 12 highlanders with chronic mountain sickness (CMS) were studied. Control measurements at sea level were also obtained in the lowlanders. Altitude exposure in the lowlanders was associated with slightly increased blood pressure, decreased LV volumes and decreased longitudinal strain with a trend to increased prevalence of post-systolic shortening (p = 0.06), whereas the low frequency/high frequency (LF/HF) ratio increased (1.62 ± 0.81 vs. 5.08 ± 4.13, p < 0.05) indicating sympathetic activation. Highlanders had a similarly raised LF/HF ratio, but no alteration in LV deformation. Highlanders with CMS had no change in LV deformation, no significant increase in LF/HF, but decreased global HRV still suggestive of increased sympathetic tone, and lower mitral E/A ratio compared to healthy highlanders. Short-term altitude exposure in lowlanders alters indices of LV systolic function and increases sympathetic nervous system tone. Life-long altitude exposure in highlanders is associated with similar sympathetic hyperactivity, but preserved parameters of LV function, whereas diastolic function may be altered in those with CMS. Altered LV systolic function in recently acclimatized lowlanders may be explained by combined effects of hypoxia and changes in loading conditions.
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