Myocardial perfusion and oxygenation are impaired during stress in severe aortic stenosis and correlate with impaired energetics and subclinical left ventricular dysfunction
Masliza MahmodJane M FrancisNikhil PalAndrew LewisSairia DassRavi De SilvaMario PetrouRana SayeedStephen WestabyMatthew D. RobsonHouman AshrafianStefan NeubauerTheodoros D. Karamitsos
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Left ventricular (LV) hypertrophy in aortic stenosis (AS) is characterized by reduced myocardial perfusion reserve due to coronary microvascular dysfunction. However, whether this hypoperfusion leads to tissue deoxygenation is unknown. We aimed to assess myocardial oxygenation in severe AS without obstructive coronary artery disease, and to investigate its association with myocardial energetics and function. Twenty-eight patients with isolated severe AS and 15 controls underwent cardiovascular magnetic resonance (CMR) for assessment of perfusion (myocardial perfusion reserve index-MPRI) and oxygenation (blood-oxygen level dependent-BOLD signal intensity-SI change) during adenosine stress. LV circumferential strain and phosphocreatine/adenosine triphosphate (PCr/ATP) ratios were assessed using tagging CMR and 31P MR spectroscopy, respectively. AS patients had reduced MPRI (1.1 ± 0.3 vs. controls 1.7 ± 0.3, p < 0.001) and BOLD SI change during stress (5.1 ± 8.9% vs. controls 18.2 ± 10.1%, p = 0.001), as well as reduced PCr/ATP (1.45 ± 0.21 vs. 2.00 ± 0.25, p < 0.001) and LV strain (−16.4 ± 2.7% vs. controls −21.3 ± 1.9%, p < 0.001). Both perfusion reserve and oxygenation showed positive correlations with energetics and LV strain. Furthermore, impaired energetics correlated with reduced strain. Eight months post aortic valve replacement (AVR) (n = 14), perfusion (MPRI 1.6 ± 0.5), oxygenation (BOLD SI change 15.6 ± 7.0%), energetics (PCr/ATP 1.86 ± 0.48) and circumferential strain (−19.4 ± 2.5%) improved significantly. Severe AS is characterized by impaired perfusion reserve and oxygenation which are related to the degree of derangement in energetics and associated LV dysfunction. These changes are reversible on relief of pressure overload and hypertrophy regression. Strategies aimed at improving oxygen demand–supply balance to preserve myocardial energetics and LV function are promising future therapies.Abstract Purpose To develop a noninvasive protocol for measuring local perfusion and metabolic demand in muscle tissue with sufficient sensitivity and time resolution to monitor kinetics at the onset of low‐level exercise and during recovery. Materials and Methods Capillary‐level perfusion, the critical factor that determines oxygen and substrate delivery to active muscle, was measured by an arterial spin labeling (ASL) technique optimized for skeletal muscle. Phosphocreatine (PCr) kinetics, which signal the flux of oxidative phosphorylation, were measured by 31 P MR spectroscopy. Perfusion and PCr measurements were made in parallel studies before, during, and after three different intensities of low‐level, stimulated exercise in rat hind limb. Results The data reveal close coupling between the perfusion response and PCr changes. The onset and recovery time constants for PCr changes were independent of contractile force over the range of forces studied. Perfusion time constants during both onset of exercise and recovery tended to increase with contractile force. Conclusion These results demonstrate that the protocol implemented can be useful for probing the mechanisms that control skeletal muscle blood flow, the physiological limits to muscle performance, and the causes for the attenuated exercise‐induced hyperemia observed in disease states. J. Magn. Reson. Imaging 2007;25:1021–1027. © 2007 Wiley‐Liss, Inc.
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Left ventricular hypertrophy (LVH) is a common sequela of sustained arterial hypertension, although the correlation between spot blood pressure measurements and LV mass is not a close one. LVH has been shown to be a powerful blood pressure-independent risk factor for cardiovascular morbidity and mortality. LVH has been shown to trigger or to accelerate ventricular dysrhythmias, although the connection between ventricular dysrhythmias and sudden death is poorly documented. LVH can be reduced by specific antihypertensive therapy; however, not all drugs are equipotent in this regard. A reduction of LVH has been shown to be associated with a suppression of ventricular dysrhythmias. Preliminary studies also indicate that the reduction of LVH may reduce its inherent excessive morbidity and mortality.
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To evaluate the effects of left ventricular hypertrophy in the development of myocardial ischaemia as detected by thallium-201 exercise scintigraphy, we studied 150 patients by two-dimensional echocardiography, SPECT thallium-201 scintigraphy, and coronary arteriography. Patients were divided into four groups according to the presence or absence of left ventricular hypertrophy and coronary artery disease. There were 62 patients with coronary artery disease and 28 with left ventricular hypertrophy. Left ventricular mass index ranged from a mean of 91.2 g m-2 in the no LVH no CAD group, to a mean of 150.6 g m-2 in the LVH CAD group. For the whole group, the sensitivity of thallium for the detection of coronary artery disease was 82%, specificity 75%, positive predictive value 70%, and negative predictive value 86%. The proportion of patients with abnormal thallium was highest (100%) in the group with left ventricular hypertrophy and coronary artery disease. The second largest group with abnormal perfusion by thallium imaging comprised patients with coronary artery disease and no left ventricular hypertrophy (78%). Both coronary artery disease and left ventricular mass index were demonstrated to be independent predictors of myocardial ischaemia in a multivariate regression model (P = 0.01). We conclude that left ventricular hypertrophy sensitizes the myocardium for the development of ischaemia.
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Objective:To explore the relationship among blood pressure(BP) level and ventricular arrhythmia(VA),myocardial ischemia(MI),left ventricular hypertrophy(LVH) in patients with essential hypertension(EH).Methods:Data of 301 patients with EH from 1995 to 2001 were reviewed,and the rate of VA,MI,LVH between BP stable group and unstable group were compared.Results:The incidence of VA(14 4%),MI(24 7%),LVH(15 0%) in BP unstable group were significantly higher than that in BP stable group (2 4%,8 7%,6 3%) ( P 0 05).Which increased with advance of disease ( P 0 05).Conclusion:The control of blood pressure level is closely correlated with CA,MI,LVH.
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The changes in electrocardiographic left ventricular hypertrophy (ECG-LVH) after transcatheter aortic valve implantation (TAVI) are not fully elucidated.
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Stress Echocardiography
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<i>Background and Purpose:</i> Electrocardiographic left ventricular hypertrophy (LVH) with strain pattern has been documented as a marker for LVH. Its presence on the ECG of hypertensive patients is associated with poor prognosis. The study was carried out to assess the association of the electrocardiographic strain with left ventricular mass (LVM) and function in hypertensive Nigerians. <i>Material and Methods:</i> ECG as well as echocardiograms were performed in 64 hypertensive patients with ECG-LVH and strain pattern, 65 patients with ECG-LVH by Sokolow-Lyon (SL) voltage criteria and 62 normal controls. <i>Results:</i> The study showed that electrocardiographic left ventricular (LV) strain pattern is associated with dilated left atrium, larger LV internal dimensions and greater absolute and indexed LVM in hypertensive Nigerians compared with ECG-LVH by SL voltage criteria alone or normal controls. <i>Conclusion:</i> The findings of this study support the fact that the ECG strain pattern is associated with increased LVM and an increased risk of developing abnormal LV geometry.
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