Biomedical subjects

R A Nishimura

Publications and source records attributed to R A Nishimura.

170 records · Page 10Linked to original sources

PubMedDate not supplied

Quantitative hemodynamics by Doppler echocardiography: a noninvasive alternative to cardiac catheterization.

Doppler echocardiography has greatly enhanced the information provided by two-dimensional echocardiography. By providing information concerning pressure gradients, intracardiac pressures, volumetric flow, and diastolic filling of the heart, most hemodynamic information that in the past could be obtained only from cardiac catheterization can now be provided accurately and noninvasively by Doppler echocardiography. Future developments in instrument technology and understanding of the various Doppler velocity curves should further aid in the ability to obtain a complete, noninvasive hemodynamic assessment of the patient with cardiac disease.

Cardiac Catheterization↗

PubMedDate not supplied

Pulmonary venous velocity patterns in mitral stenosis.

Pulmonary venous (PV) velocities obtained by transthoracic echocardiography are used to assess diastolic function. The systolic/diastolic (S/D) PV velocity ratio is increased with impaired early diastolic filling and decreased with elevated mean left atrial pressure (LAP). Mitral stenosis (MS) is characterized by impaired filling and elevated LAP. We hypothesized that the S/D ratio would be increased in MS except in severe MS with high LAP, in which the S/D ratio would be decreased. Patients with isolated MS who underwent transthoracic echocardiography were studied. The PV S/D ratio was compared in mild (n = 18), moderate (n = 16), and severe (n = 7) MS. There was no characteristic PV pattern, with each category showing a wide range of S/D ratios (mild, S/D ratio = 1.42 +/- 0.56; moderate, S/D ratio = 1.19 +/- 0.59, and severe, S/D ratio = 1.33 +/- 0.53) (mean +/- SD). Furthermore, there was no relationship between the S/D ratio and any index of severity of MS. There is no characteristic PV velocity pattern in MS.

Atrial Function, Left↗

PubMedDate not supplied

Measurement of left ventricular dp/dt by simultaneous Doppler echocardiography and cardiac catheterization.

Left ventricular dp/dt is a useful isovolumic index for evaluating acute directional changes in myocardial contractility. To test the hypothesis that Doppler echocardiography can measure left ventricular dp/dt by using the mitral regurgitation velocity curve, 14 patients with at least a mild degree of mitral regurgitation (four with coronary artery disease, four with valvular heart disease, four with dilated cardiomyopathy, one with carcinoid, and one with mitral valve prosthesis) were studied by continuous-wave Doppler echocardiography. Simultaneously, left ventricular pressure was measured with a manometer-tipped catheter to generate actual dp/dt. Curves of left ventricular pressure and mitral regurgitant Doppler-derived velocities of three cardiac cycles were digitized at 1-msec intervals. The rate of Doppler-derived velocity increase was converted to a rate of pressure increase by using the modified Bernoulli equation. Mean dp/dt during various time intervals of the mitral regurgitation velocity envelope (1 to 2 m/sec, 2 to 3 m/sec, and 1 to 3 m/sec) corresponding to left ventricular-left atrial pressure differences of 12, 20, and 32 mm Hg, respectively, were calculated. Doppler-derived left ventricular dp/dt (y) correlated with catheter-derived left ventricular dp/dt (x) as follows: at the 1 to 2 m/sec interval, y (mm Hg/sec) = 0.84x + 137, r = 0.91, SEE = 90; at the 2 to 3 m/sec interval, y = 1.1x - 89, r = 0.96, SEE = 80; and at the 1 to 3 m/sec interval, y = 1.1x + 23, r = 0.98, SEE = 50.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMedDate not supplied

Mitral flow velocity curves as a function of different loading conditions: evaluation by intraoperative transesophageal Doppler echocardiography.

Transesophageal pulsed wave Doppler echocardiography was performed intraoperatively on 10 patients undergoing coronary artery bypass operation. Mitral flow velocity curves and hemodynamic values were recorded during control conditions and intravenous infusion of (1) nitroglycerin, (2) phenylephrine, and (3) fluids. During nitroglycerin infusion blood pressure and wedge pressure decreased, peak filling velocity decreased, and deceleration time increased compared with control values. During infusion of phenylephrine blood pressure increased, there was a trend toward a decrease in peak filling velocity, and deceleration time increased. During infusion of fluids wedge pressure increased, deceleration time decreased, and peak filling velocity increased. Mitral flow velocity curves are therefore altered by changes in hemodynamic loading conditions.

Adult↗

PubMedDate not supplied

Variability between methods of calculating mitral valve area: simultaneous Doppler echocardiographic and cardiac catheterization studies conducted before and after percutaneous mitral valvuloplasty.

The purpose of this study was to assess the variability of measuring the mitral valve area (MVA) by the cardiac catheterization (Gorlin) method and two Doppler echocardiographic methods, the pressure half-time and continuity equation methods. The determinants of MVA were measured simultaneously before and after percutaneous mitral balloon valvuloplasty (PBMV). Thirty-three patients with severe mitral stenosis underwent simultaneous measurements of MVA by the three methods immediately before and within 15 minutes after PBMV. After combining all data, the correlation between the catheterization and pressure half-time methods was significant (r = 0.65; p < 0.001), as was that between the catheterization and continuity equation methods (r = 0.64; p < 0.001). However, there was a large degree of variability among the measurements with the three techniques. The mean difference between the catheterization and pressure half-time methods of measuring MVA before PBMV was -0.2 +/- 0.4 cm2 and 0.1 +/- 0.3 cm2 between the catheterization and continuity equation methods. This variability was even more marked after PBMV: -0.5 +/- 0.9 cm2 between the catheterization and pressure half-time methods and 0.4 +/- 0.6 cm2 between the catheterization and continuity equation methods. Although previous studies have shown a good correlation between MVA as measured with the catheterization and two Doppler echocardiographic methods, they included a wide range of MVAs. In our study of patients with hemodynamically significant mitral stenosis, there was a large degree of variability between the catheterization and simultaneously performed Doppler echocardiographic methods. The calculated MVA by any method should not be used as the single measure of severity of stenosis.

Adult↗

PubMedDate not supplied

Systolic aortic valve compression from partial dehiscence of an aortic valve homograft.

Implantation of valve prostheses provide improvement of symptoms and prolongation of life in selected patients with valvular heart disease. Meticulous follow-up of patients after valve surgery is essential as complications of valve failure, valve dehiscence, valve thrombosis, and infection may occur. The major mode of failure of aortic valve homografts is valve regurgitation, which is readily detected by physical examination. We report a case of left ventricular outflow obstruction after implantation of an aortic valve homograft.

Adult↗

PubMedDate not supplied

Assessment of left ventricular end-diastolic pressure by Doppler echocardiography: contribution of duration of pulmonary venous versus mitral flow velocity curves at atrial contraction.

The difference in the durations of flow with atrial contraction (A duration) at the pulmonary veins and mitral valve has been reported to detect the presence of elevated left ventricular end-diastolic pressure. It is postulated that with left ventricular filling during atrial contraction, reduced ventricular compliance results in the transmission of increased pressure into the left atrium, resulting in prolongation of the pulmonary venous flow with atrial contraction. However, the relationship between ventricular compliance during atrial contraction and the pulmonary venous and mitral A durations and their difference have not been carefully examined. We performed recordings of left ventricular pressure and complete Doppler analysis of pulmonary venous and transmitral flow in 87 patients. Operant ventricular compliance at atrial contraction was estimated by measuring the increase in ventricular pressure with atrial contraction (left ventricular a wave) and by using a compliance index, which incorporated an estimate of flow into the ventricle with atrial contraction from the Doppler transmitral a wave. The difference in pulmonary venous and mitral A durations correlated well with left ventricular end-diastolic pressure (r = 0.73, p < 0.01) and the pulmonary venous reversal duration exceeding the duration of the mitral A velocity curve provided high sensitivity (82%) and specificity (92%) for the detection of an end-diastolic pressure of 20 mm Hg or greater. The pulmonary venous A duration increased with a moderate decrease in ventricular compliance but was not increased further in patients with a severe decrease in compliance. In contrast, mitral A duration was not different in patients with moderate reduction in compliance, but was shorter in patients with severe decreases in ventricular compliance. Pulmonary venous and mitral A durations are related to ventricular compliance and they change in an opposite and progressive manner. Their difference is a sensitive method for the detection of the elevated end-diastolic pressure associated with reduction in ventricular compliance.

Adult↗

PubMedDate not supplied

Right ventricular infarction associated with anteroseptal myocardial infarction: a clinicopathologic study of nine cases.

The association of right ventricular (RV) infarction with inferoseptal myocardial infarction is well established. However, a question remains about the occurrence of RV infarction in association with anteroseptal myocardial infarction. To determine the frequency and clinical correlates of this entity, we studied autopsied hearts from patients with isolated anteroseptal left ventricular (LV) infarcts. Among 3,249 autopsy specimens, 88 cases were identified. From each, sections were taken from the RV anterior, lateral, and inferior regions at basal, middle, and apical levels. All 1,584 slides were reviewed by blinded assessment. RV and LV infarcts were compared to confirm similarity in age. Patient records and cardiac investigations were reviewed for evidence of RV involvement. Of the 88 hearts with anteroseptal LV infarcts, 9 (10%) had coexistent RV infarction (6, old; 3, new). For these 9, the RV infarction involved 11% to 33% of the RV area, and the left anterior descending coronary artery was the infarct-related artery in each. All 3 patients who had an echocardiographic examination within 4 weeks of anteroseptal LV infarction had RV dysfunction. One patient, studied 15 years after infarction, had a normal right ventricle by echocardiography. In 3 patients with acute myocardial infarction, right heart catheterization during the acute phase revealed increased right-sided diastolic pressures out of proportion to left-sided diastolic pressures (right atrial pressure to pulmonary capillary wedge pressure, 60% to 95%). In conclusion, 10% of patients with an isolated anteroseptal LV infarct had evidence of RV free wall infarction. The RV infarction was associated with identifiable hemodynamic and echocardiographic features.

Adult↗