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Biomedical subjects

R A Nishimura

Publications and source records attributed to R A Nishimura.

At least 91 records · Page 5Linked to original sources
PubMed1994

Quantitative evaluation of left ventricular systolic function by Doppler echocardiographic techniques.

Doppler echocardiography provides the ability to measure blood flow velocities noinvasively. These blood flow velocities can be used to obtain powerful hemodynamic information about systolic contractility of the left ventricle, which in the past could only be determined from invasive cardiac catheterization or cumbersome pulse recordings. Volumetric flow rates can be measured using the hydraulic principle of flow through a rigid tube, providing a measurement of stroke volume and cardiac output. The rate of the left ventricular pressure rise derived from a mitral regurgitation velocity curve provides a nonejection phase index of systolic contractility. Acceleration time can be obtained from an ascending aortic velocity and is an indicator of maximum myocardial force. Systolic time intervals can now be quickly and accurately obtained from the standard Doppler tracings. These quantitative measurements of the status of the left ventricular are accurate, reproducible, and should be incorporated into the routine noninvasive assessment of patients with cardiac disease.

Aorta↗
PubMed1994

Systolic and diastolic dysfunction in patients with clinical diagnosis of dilated cardiomyopathy. Relation to symptoms and prognosis.

BACKGROUND: Dilated cardiomyopathy is an important cause of morbidity and mortality among patients with congestive heart failure. Hemodynamic and prognostic characterization are critical in guiding selection of medical and surgical therapies. METHODS AND RESULTS: A cohort of 102 patients with the clinical diagnosis of dilated cardiomyopathy who underwent echocardiographic examination between 1986 and 1990 was identified and followed up through July 1, 1991. Patients with moderate or severe symptoms had lower indices of systolic function and greater left atrial and right ventricular dilation. Mitral inflow Doppler signals were characterized by a restrictive left ventricular filling pattern. In multivariate logistic regression analysis, deceleration time, ejection fraction, and peak E velocity were independently associated with symptom status. Over a mean follow-up of 36 months, 35 patients died. Kaplan-Meier estimated survival at 1, 2, and 4 years was 84%, 73%, and 61%, respectively, and was significantly poorer than that of an age- and sex-matched population. The subgroup with an ejection fraction < 0.25 and deceleration time < 130 milliseconds had a 2-year survival of only 35%. The subgroup with ejection fraction < 0.25 and deceleration time > 130 milliseconds had an intermediate 2-year survival of 72%, whereas patients with an ejection fraction > or = 0.25 had 2-year survivals > or = 95% regardless of deceleration time. In multivariate analysis, ejection fraction and systolic blood pressure were independently predictive of subsequent mortality. Mitral deceleration time was significant in univariate analysis. CONCLUSIONS: In patients with the clinical diagnosis of dilated cardiomyopathy, markers of diastolic dysfunction correlated strongly with congestive symptoms, whereas variables of systolic function were the strongest predictors of survival. Consideration of both ejection fraction and deceleration time allowed identification of subgroups with divergent long-term prognoses.

Aged↗
PubMed1994

Quantitative echocardiography: a comparison with ultrafast computed tomography in patients with chronic aortic regurgitation.

Chronic aortic regurgitation leads to progressive left ventricular dilatation and hypertrophy. It is important to be able to measure these variables for clinical decision making on the timing of aortic valve replacement. M-mode and two-dimensional echocardiography are widely utilized in clinical practice for a qualitative assessment of left ventricular size and function. Recent recommendations have been proposed for the use of quantitative assessment by left ventricular size and left ventricular mass by two-dimensional echocardiography; there has been no study examining the validity of these measurements in patients with aortic regurgitation. The purpose of this study was to prospectively examine the various geometric models of echocardiographically determined left ventricular mass and volumes in patients with chronic aortic regurgitation compared with cine-computed tomographic scanning. Twenty-two patients with chronic aortic regurgitation were prospectively identified and underwent two-dimensional echocardiographic and cine-computed tomographic scanning. M-mode and two-dimensional echocardiographic images were analyzed on an off-line measurement digital system. Seven previously described geometric models were used in this study for quantitative analysis. Both left ventricular mass and left ventricular volume were calculated from real-time ultrafast tomographic scans. Left ventricular mass determinations by two-dimensional echocardiography correlated more than M-mode determinations (r = 0.84 vs. r = 0.75, standard error of the estimate (SEE) = 38 g vs. 139 g). Biplane two-dimensional echocardiography formulas using Simpson's rule construct yielded more accurate values for left ventricular end-diastolic volumes (r = 0.92, SEE = 24 ml) than either the single-plane Simpson's rule (r = 0.58, SEE = 73 mL) or methods using predetermined models of left ventricular shape (r = 0.80, SEE = 38 ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Percutaneous balloon mitral valvuloplasty: comparison of double and single (Inoue) balloon techniques.

To assess relative merits of the double and single (Inoue) balloon techniques of percutaneous balloon mitral valvuloplasty for treating symptomatic mitral stenosis, 33 patients who underwent dilatation with the double balloon were compared retrospectively with 28 who underwent dilatation with the Inoue balloon. There were no baseline differences in mean left atrial pressure, mean mitral gradient, or calculated mitral valve area between the two groups. The procedure was successful in 89% of patients in the double balloon group and in 93% in the Inoue balloon group. Final mitral valve area and absolute increase in mitral valve area were significantly greater in the double balloon group, in which there was a nonsignificant trend toward greater incidence of acute complications. Final left atrial pressure and mitral gradient were not different. Both techniques are useful and safe.

Catheterization↗
PubMed1993

Failure of calcium channel blockers to improve ventricular relaxation in humans.

OBJECTIVES: The objective of this study was to ascertain whether the reversal of low peak filling rates after administration of calcium channel blockers in patients with diastolic dysfunction indicates true improvement in the rate of ventricular relaxation and left ventricular end-diastolic pressure measured by invasive indexes. BACKGROUND: Depressed filling rates measured noninvasively have been associated with diastolic dysfunction, specifically abnormal relaxation of the left ventricle. There is a reversal of these low peak filling rates after administration of calcium channel blockers. METHODS: Doppler echocardiographic measurements of peak filling rates were made and invasive high fidelity manometer-tipped pressures were measured before and after administration of verapamil (0.1 mg/kg body weight) in 20 patients with coronary artery disease who had an ejection fraction > 40% and decreased peak filling rates. RESULTS: Verapamil caused significant increases in the peak filling rate, as measured by early transmitral (E) flow velocity, from 0.57 +/- 0.16 m/s to 0.77 +/- 0.15 m/s (p < 0.01), indicating reversal of decreased peak filling rates. Concomitantly, left ventricular end-diastolic pressure increased from 18.0 +/- 7.7 mm Hg to 24.1 +/- 9.0 mm Hg (p < 0.001). The time constant of relaxation was variable, with an overall significant increase from 45.8 +/- 10.4 ms to 53.2 +/- 14.6 ms (p = 0.01). CONCLUSIONS: Verapamil administered intravenously produced reversal of decreased peak filling rates in patients with coronary artery disease and normal ventricular function. However, there was an increase in left ventricular end-diastolic pressure as well as an overall prolongation of the time constant of relaxation. Therefore, changes in peak filling rates do not accurately reflect the response of ventricular relaxation to drug interactions. Thus, calcium channel blockers should be used cautiously in the empiric treatment of patients with diastolic dysfunction.

Aged↗
PubMed1993

Use of intracoronary ultrasound imaging for assessing left main coronary artery disease.

Coronary angiography has many limitations for the assessment of coronary artery disease. Intracoronary ultrasound imaging may overcome some of these limitations by providing direct visualization of the luminal area and plaque morphologic features. Although the size of the currently available intracoronary ultrasound catheters precludes their use in many diseased coronary vessels, lesions in the relatively large vessels, such as the left main coronary artery, can be readily assessed. Intracoronary ultrasound imaging was performed in five patients in whom the status of the left main coronary artery was unclear after conventional coronary angiography. Qualitative assessment of atherosclerotic involvement and quantitative analysis of the absolute luminal area and the percentage of area of stenosis were performed. No complications were associated with the intracoronary ultrasound procedure. In all five patients, the ultrasound studies provided additional information on which a clinical decision could be made. Intracoronary ultrasound imaging is useful for assessing disease of the left main coronary artery in selected patients in whom current angiographic techniques have provided equivocal results.

Aged↗
PubMed1993

Noninvasive measurement of rate of left ventricular relaxation by Doppler echocardiography. Validation with simultaneous cardiac catheterization.

BACKGROUND: The instantaneous pressure gradient between the left ventricle and left atrium during systole can be calculated from the mitral regurgitation Doppler velocity curve. The purpose of our study was to determine the accuracy of measuring the time constant of relaxation (TAU) derived from the Doppler mitral regurgitation signal by comparing it with simultaneous high-fidelity left ventricular pressure measurements in humans. METHODS AND RESULTS: Twenty-five patients had continuous-wave Doppler mitral regurgitation recordings performed with simultaneous high-fidelity left ventricular pressure measurements. Fifteen of these patients had measurements of six to eight beats at various RR intervals. Doppler velocity curves were converted to left ventricular pressure curves by different methods through application of the modified Bernoulli equation at 3-msec intervals. The correlation between catheter-derived and Doppler-derived TAU was best when a zero asymptote and knowledge of the left ventricular end-diastolic pressure were used. A less optimal but acceptable method used the addition of 20 mm Hg to the Doppler-derived ventriculoatrial gradient. Use of a nonzero asymptote for calculation of TAU yielded poor correlation between catheter and Doppler measurements. The correlation of percentage change in Doppler-derived TAU plotted against percentage change in catheter-derived TAU was poor. CONCLUSIONS: The descending limb of the Doppler-derived mitral regurgitation velocity signal can be used as a semiquantitative estimate of the rate of ventricular relaxation. This method requires knowledge of left atrial pressure and may not be sufficiently accurate for detecting small changes in the rate of relaxation on a beat-to-beat basis.

Atrial Function, Left↗
PubMed1993

Second natural history study of congenital heart defects. Aortic stenosis: echocardiography.

BACKGROUND: Recent advances in the field of echocardiography have made it possible to obtain a complete morphological and hemodynamic assessment of patients with aortic stenosis. Therefore, comprehensive two-dimensional and Doppler examinations were performed on patients with aortic stenosis returning for the Second Natural History Study of Congenital Heart Defects (NHS-2). METHODS AND RESULTS: Two hundred thirty-two patients with aortic stenosis underwent comprehensive two-dimensional and Doppler examinations. Of these, 96 were in the medically treated group, 49 had undergone aortic valve replacement, and 87 had had aortic valvotomy. The valve replacement group had a significantly smaller left ventricular diastolic cavity than did the medically treated group; both had smaller dimensions than the valvotomy group. There was no significant difference in left ventricular wall thickness or fractional shortening among the three groups. The valvotomy group had a significantly higher mean aortic valve gradient than did either the medically treated group or the valve replacement group. The degree of aortic regurgitation was more severe in the valvotomy group than in the other two groups. For all patients, there was a direct relation between the aortic valve gradient and the mean wall thickness and an inverse relation between the aortic valve mean gradient and fractional shortening. The only echocardiographic parameter that correlated with the presence or absence of symptomatology was the fractional shortening. CONCLUSIONS: These observations provide an objective measurement for assessing the status of the aortic valve and left ventricular response in patients with aortic stenosis returning for NHS-2. Limitations of echocardiography in this study are discussed.

Adolescent↗
PubMed1993

Second natural history study of congenital heart defects. Pulmonary stenosis: echocardiography.

BACKGROUND: Two-dimensional and Doppler echocardiography can provide information about valve morphology, right ventricular size and function, and hemodynamics in patients with pulmonary stenosis. Therefore, two-dimensional and Doppler echocardiographic examinations were performed on patients with pulmonary stenosis returning for the Second Natural History Study of Congenital Heart Defects. METHODS AND RESULTS: Three hundred twenty-five patients with pulmonary stenosis underwent two-dimensional and Doppler echocardiographic examinations. Of these, 115 were in the medically treated group, and 210 had undergone a previous operation. Patients in the valvotomy group had a higher incidence of right ventricular dysfunction and a larger right ventricular diastolic dimension. The valvotomy group had a lower pulmonary valve mean gradient and a lower right ventricular systolic pressure than the medically treated group. For all patients, there was no significant correlation of the echocardiographic variables with the presence or absence of symptoms, reflecting the low incidence of patients with cardiac decompensation. CONCLUSIONS: These observations provide an objective measurement for assessing the status of the pulmonary valve and right ventricular response in patients with pulmonary stenosis. Limitations of echocardiography in this study are discussed.

Adolescent↗
PubMed1993

Second natural history study of congenital heart defects. Ventricular septal defect: echocardiography.

BACKGROUND: Two-dimensional and Doppler echocardiography can provide structural and hemodynamic information for patients with ventricular septal defects (VSDs). Therefore, two-dimensional and Doppler echocardiographic examinations were performed on patients with VSDs returning for the Second Natural History Study of Congenital Heart Defects. METHODS AND RESULTS: Five hundred fifty-six patients with VSDs underwent two-dimensional and Doppler echocardiographic examinations. Three hundred twenty-four patients were in the medically treated group, and 232 had undergone a previous operation. The location of the VSD was classified in 235 patients. Several Doppler measurements were used to calculate pulmonary artery pressures: tricuspid regurgitation peak systolic velocity, peak systolic velocity of VSD jet, pulmonary regurgitation end-diastolic velocity, and pulmonary artery acceleration time. The two methods that were found to be reliable consisted of the tricuspid regurgitation peak systolic velocity and the pulmonary regurgitation end-diastolic velocity. These measurements were obtained in only 26% of patients at all centers. At one center in which adult and pediatric echocardiography was performed in a single laboratory, these values were obtained in 60% of patients. CONCLUSIONS: Two-dimensional and Doppler echocardiography has the ability to provide a noninvasive method of assessing morphology and hemodynamics in patients with VSDs. However, the reliability and accuracy of hemodynamic measurements are dependent on operator experience.

Blood Pressure↗
PubMed1992

Ventricular relaxation and myocardial ischemia: a comparison of different models of tau during coronary angioplasty.

This study compares the sensitivity and variability of four models of tau, the time constant of ventricular relaxation, to detect the presence of myocardial ischemia. High fidelity left ventricular pressure recordings were obtained in ten patients undergoing coronary angioplasty at baseline, during balloon inflation, and at recovery. Four models of tau were considered: 1) a semilogarithmic, zero asymptote model (TL), 2) a semilogarithmic model using data from the first 40 ms of isovolumic relaxation (T40), 3) an exponential non-zero asymptote model (TE), and 4) a derivative non-zero asymptote model (TD). TL, T40, and TE increased significantly during inflation and returned to near baseline values at recovery. TD showed no change during inflation. Comparisons of TL, T40, and TE using the derived relaxation half-time (T1/2), failed to reveal significant differences between the models at baseline, during inflation, or at recovery. The non-zero asymptote models were associated with a greater beat-to-beat variability than the semilogarithmic models. Thus, T1/2 using the semilogarithmic zero asymptote models (TL and T40) may be more useful and consistent when measuring the rate of isovolumic relaxation during myocardial ischemia.

Angioplasty, Balloon, Coronary↗
PubMed1992

Semiquantitation of aortic regurgitation by different Doppler echocardiographic techniques and comparison with ultrafast computed tomography.

Fourteen patients with chronic aortic regurgitation were studied by several two-dimensional and Doppler echocardiographic methods to determine the severity of aortic regurgitation. Semiquantitation of aortic regurgitation was performed by various color-flow imaging measurements, diastolic half-time of the continuous-wave regurgitation jet, and pulsed-wave velocity curve in the descending aorta. These measurements were compared with regurgitant volume and fraction by ultrafast computed tomography. All Doppler methods demonstrated a significant correlation for severity of aortic regurgitation with regurgitant fraction by ultrafast computed tomographic scanning, but scatter was present with each method. The methods with the closest correlation were at the lowest level of obtainable results. In clinical practice, all Doppler methods must be used to determine the severity of aortic regurgitation.

Adult↗
PubMed1992

Recurrence of symptoms after percutaneous aortic balloon valvuloplasty: relationship to Doppler diastolic filling values.

Short-term follow-up after percutaneous aortic balloon valvuloplasty shows a high incidence of restenosis. Yet a high percentage of patients with restenosis continue to show symptomatic improvement. Those with decreased left ventricular function originally tend to have a recurrence of symptoms. In this study Doppler-derived diastolic filling values at follow-up were most highly associated with symptom status, suggesting that change in diastolic filling after percutaneous aortic balloon valvuloplasty is one of the factors related to symptoms.

Aged↗
PubMed1991

Doppler echocardiographic findings in adults with severe symptomatic valvular aortic stenosis. Balloon Valvuloplasty Registry Echocardiographers.

Baseline echocardiographic data in 680 adults (mean age 78 years) undergoing balloon aortic valvuloplasty at 24 medical centers were analyzed to describe the degree of outflow obstruction in patients with symptomatic aortic stenosis. Maximal aortic jet velocity ranged from 2.3 to 6.6 m/s (mean 4.4 +/- 0.8) and continuity equation valve area ranged from 0.1 to 1.4 cm2 (mean 0.6 +/- 0.2). Of note, 36% had a jet velocity less than or equal to 4.0 m/s but only 3% had a valve area greater than 1.0 cm2 due to a high prevalence of impaired systolic function (54%). Outflow tract diameter was poorly correlated with body surface area (p = 0.26), although the group mean diameter was smaller in women than in men (1.9 +/- 0.2 vs 2.1 +/- 0.3 cm, p = 0.0001). Mean pressure gradient was related closely to maximal gradient (r = 0.92) and to maximal jet velocity (mean delta P = 2.4 V2 + 0.75 mm Hg). Simpler measures of aortic stenosis severity were correlated with Doppler and invasive valve area as follows: maximal jet velocity (r = -0.36 and -0.32), mean gradient (r = -0.33 and -0.29), outflow tract to jet velocity ratio (r = 0.67 and 0.40), and the fractional shortening velocity ratio (r = 0.29 and 0.22). This study demonstrates marked variability in stenosis severity in symptomatic adults referred for balloon aortic valvuloplasty. The absence of a predictable relation between outflow tract diameter and body size emphasizes the importance of this measurement in each patient if definition of valve area is needed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Patient age and results of balloon aortic valvuloplasty: the Mansfield Scientific Registry experience. The Mansfield Scientific Aortic Valvuloplasty Registry Investigators.

Patients enrolled in the Mansfield Scientific Aortic Valvuloplasty Registry were followed up a mean of 7 months after balloon aortic valvuloplasty. Results were compared for patients less than 70, 70 to 79 and greater than or equal to 80 years of age at time of valvuloplasty. As assessed by aortic valve area indexed to body surface area, stenosis was more severe in the older patients and the incidence of congestive heart failure was also greater in those aged greater than or equal to 80 years. The results of valvuloplasty were comparable in all three age groups, and indexed final valve area was not significantly different among the groups. In-hospital mortality ranged from 4.2% to 9.4%, but this and other complications were not significantly different among the groups. Total 7 month mortality was 23%. As performed in this registry study, balloon aortic valvuloplasty produced similar results in older and younger patients, despite initially more severe disease in the older patients.

Age Factors↗