SUMMARY To compare two-dimensional (2-D) echocardiographic estimates of right ventricular size and performance to similar determinations from equilibrium radionuclide angiography (RNA) before and after isosorbide dinitrate, we evaluated 19 patients with severe chronic obstructive pulmonary disease. The enddiastolic and end-systolic volumes estimated from subcostal 2-D echocardiographic views of the right ventricle correlated with the RNA end-diastolic and end-systolic counts (r = 0.76 and 0.82, respectively). The 2-D echocardiographic and RNA right ventricular ejection fraction (EF)
Exercise intolerance and right ventricular (RV) dysfunction are cardinal features of pulmonary arterial hypertension (PAH). Despite the significantly elevated afterload, patients rarely experience symptoms at rest until the late stages of the disease. Recent data suggest that the ability of the right ventricle to adapt to increased afterload is an important determinant of exercise capacity and outcome in PAH [1]. RV ejection fraction (RVEF) has been demonstrated to predict outcome [2]. There is also growing evidence that a noninvasively derived right ventriculo-arterial coupling ratio (VACR) may provide important prognostic information [3]. However, it remains unclear to what extent RV contractility is impaired during exercise and which metric best describes ventricular functional adaptation to afterload in PAH. We aimed to evaluate and compare the effects of submaximal exercise on RV systolic function and VACR in PAH and healthy subjects using cardiac magnetic resonance (MRI). We also examined and compared VACR and cardiopulmonary exercise test (CPET) in estimating the severity of disease.Nine clinically compensated subjects with severe PAH (eight females aged 45.7±12.3 years, mean pulmonary artery pressure 55.8±18.7 mmHg, body mass index 24.8±3.3 kg•m −2 , World Health Organization functional class 2.2±0.4 and no significant valvular diseases) and nine healthy nonsmoking controls with no history of cardiorespiratory disease (six females aged 40.7±9.4 years, body mass index 23.4±2.7 kg•m -2 ) participated. Mean 6-min walking distance for PAH subjects was 614.6±48.9 m. All PAH subjects were on stable combination PAH-specific therapies consisting of prostanoids (n=4), phosphodiesterase-5 inhibitors (n=8) and endothelin receptor antagonists (n=9). This study was approved by the institution's Research Governance Office (HREC/14/QPCH/47).Cardiac MRI was performed on a clinical 1.5-T MR scanner (MAGNETOM Aera; Siemens Healthcare, Erlangen, Germany). A prototype ultrafast cine MRI sequence with a compressed sensing reconstruction was used to enable 12-fold acceleration of image acquisition [4] and RV function was measured utilising modified short-axis summation of slab volume technique [5]. Ventricular contractile reserve was defined as (ventricular function stress-ventricular function rest)/ventricular function rest. The approach from SANZ et al.[6] was used to calculate VACR=stroke volume/end-systolic volume (ESV).
The nrnmal range for aortic root
The metal-tipped optical fiber or "laser probe" has been extensively studied in animal preparations in vivo and in human clinical trials of revascularization. The aim of this study was to evaluate the thermal characteristics of laser probe tissue ablation and to contrast the vascular tissue response to exposure to the laser probe and bare optical fiber. A 2 mm laser probe was heated with up to 4 W of argon-ion laser irradiation and applied to six postmortem strips ofhuman nonatherosclerotic aorta as well as to five atherosclerotic aortic specimens. Surface temperature maps of the laser probe and of the vascular tissue in air were obtained via 8 to 12 ,um thermographic imaging. Laser probe temperature was additionally monitored via thermocouples. Two strips each of normal and diseased aorta were irradiated directly with the bare optical fiber. Thus a total of 43 laser probe application sites and 19 bare fiberoptic laser irradiation sites on a total of 15 aortic strips were analyzed both thermographically and histologically. Based on measured temperature rises and histologic findings, the following observations were made: (1) The laser probe heats initially at its tip and attains a uniform surface temperature distribution within 5 sec. The steady-state temperature attained by the probe is inversely related to the thermal conductivity of the surrounding media. In all media studied, probe temperature increases linearly with applied laser energy. (2) Tissue ablation starts at temperatures greater than 1000 C, and ablation temperatures typically exceed 1800 C. Adventitial temperatures during laser probe application may reach 700 C. Tissue ablation is enhanced both by greater laser energy deposition in the probe and by higher force at which the probe is applied to tissue. (3) Ablation of fibrofatty atheromata is more extensive than of nonatherosclerotic aortic tissue. This may be due to the lower thermal conductivity of atheromatous tissue. (4) In contrast to direct argon-ion laser ablation of aortic tissue, laser probe-mediated ablation occurs in a controlled fashion, is not associated with extensive subintimal dissections, and allows uniform conduction of heat to tissue as reflected by essentially "isothermal" injury lines. Circulation 76, No. 5, 1353No. 5, -1363No. 5, , 1987 ATHEROSCLEROTIC arterial occlusive disease continues to constitute the major cause of morbidity and mortality in the United States. Over the past 4 years, substantial work has been done in an attempt to develop a laser technology that can be applied to the percutaneous revascularization of obstructive peripheral vascular and coronary artery disease. In contrast to conFrom the Biomedical Engineering Program of the
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