The experiments were designed to determine the contribution of the leg muscle relaxation to the sensitization of the vestibular function under weightlessness, The neuromuscular unit (NMU) discharges were continuously recorded with microelectrodes from the anti-gravitational soleus muscle and its antagonist, the tibialis anterior, of a man standing first upright on the level floor of a dry water tank, and then gradually being immersed in water till it reached his neck; while he was buoyed with an airtube placed under his armpit. In each of the successive states, the caloric nystagmus was evoked, analyzed and compared with the NMU discharge as well as with subjective symptoms associated with the nystagmus. The results indicate that the nystagmogenic activity had a significant correlation with the appearance of the active NMU in the soleus, and they also suggest that the reduction of ascending signals from the antigravity muscles might be one of the causes of atypical vestibular responses occuring in weightlessness.

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PubMedDate not supplied

Transthoracic Doppler echocardiographic measurements of pulmonary venous flow velocity patterns: comparison with transesophageal measurements.

Recently, we and other groups showed that analysis of transthoracic pulmonary venous flow velocity patterns is useful in the estimation of left ventricular diastolic function and left atrial pressure; however, it is unclear whether transthoracic tracings, in contrast to transesophageal tracings, provide reliable quantitation of the abnormal pulmonary venous flow characteristics in patients with and without cardiac disorders. This study was attempted to validate transthoracic pulmonary venous flow measurements by comparing them with transesophageal measurements in eight normal volunteers and 17 patients with a variety of cardiac disorders. Transesophageal and transthoracic measurements of peak diastolic forward flow velocity, the ratio of peak systolic/diastolic forward flow velocities, and the peak reversal flow velocity at atrial contraction sampled in the right upper pulmonary vein showed good correspondence to each other. The flow velocities were higher in the right upper pulmonary vein than in the left upper pulmonary vein. Narrower spectral flow velocity patterns with higher velocities were obtained 1 to 2 cm distal to the orifice in the pulmonary vein than at the orifice. Thus transthoracic measurements of the pulmonary venous flow velocity pattern are feasible and accurate in patients and may be used to assess left ventricular function and hemodynamics as a substitute for transesophageal measurements.

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PubMedDate not supplied

Progressive intraventricular drop of early diastolic flow velocity reflects impaired active ventricular diastolic function in hypertensive heart disease: comparative study between early diastolic and atrial contraction phases.

Left ventricular (LV) diastolic function in the early diastolic phase includes both active and passive processes, but in the atrial contraction phase it includes only passive processes. To elucidate the relation between the intraventricular dispersion of the flow velocity in diastole and LV diastolic process, 31 normal volunteers and 12 patients with hypertensive heart disease were studied. In these subjects the flow velocity pattern at the mitral tip was recorded simultaneously with regional flow velocity patterns 1, 2, or 3 cm from the mitral tip toward the apex, respectively, with multigate pulsed Doppler echocardiography from the apical long-axis view with the guidance of Doppler color-flow imaging. Although the ratio of regional peak flow velocity/mitral peak flow velocity in the atrial contraction phase decreased from the mitral tip to the apex to the same degree in the normal volunteers and patients with hypertensive heart disease, there was a significant difference in the intraventricular dispersion of the early diastolic flow velocity between the two groups. These results suggest that the progressive intraventricular drop of the flow velocity in the early diastolic phase in patients with hypertensive heart disease may reflect the impairment of active rather than passive LV diastolic function.

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PubMedDate not supplied

Transthoracic Doppler assessment of pattern of left ventricular dysfunction in hypertensive heart disease: combined analysis of mitral and pulmonary venous flow velocity patterns.

Although mitral flow velocity pattern changes with the progression of left ventricular (LV) diastolic dysfunction, it lacks predictive value in individual patients because of pseudonormalization in the presence of congestive heart failure and many physiologic and pathologic contributors to the mitral flow velocity pattern. To determine whether analysis of pulmonary venous flow velocity patterns complements the information obtainable from the mitral flow velocity patterns in the evaluation of patterns of LV dysfunction of hypertensive heart disease in individual patients, the ratio of the peak early diastolic filling velocity/peak filling velocity at atrial contraction (E/A ratio) in the mitral flow velocity pattern and the ratio of the peak systolic forward flow velocity (S)/peak diastolic forward flow velocity (D) (S/D ratio) in the pulmonary venous flow velocity pattern by the transthoracic approach were determined in 107 hypertensive patients with and without congestive heart failure. Age-related normal values of the E/A and S/D ratios were determined in 61 normal subjects and used to judge the normality or abnormality of the patterns. Results of the study indicate that (1) although an increased mitral E/A ratio is strongly indicative of heart failure with normal LV systolic function, the mitral E/A ratio is frequently within the normal range in hypertensive patients with heart failure; (2) association of decreased pulmonary venous S/D ratios with a normal mitral flow velocity pattern indicates the presence of heart failure as a result of LV systolic dysfunction that is usually observed at the most advanced pattern of LV dysfunction; (3) mild LV diastolic dysfunction is likely to exist in patients with normal E/A ratios if the pulmonary venous S/D ratio is higher than normal value; (4) predictive accuracy in the detection of LV systolic and diastolic dysfunction would be improved if both mitral and pulmonary venous flow velocity patterns rather than the mitral flow velocity pattern alone were analyzed. In conclusion, analysis of pulmonary venous flow velocity recordings improves accuracy and reliability of the Doppler assessment of LV systolic and diastolic dysfunction, particularly in individual hypertensive patients with normal mitral flow velocity patterns.

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