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Biomedical subjects

N B Schiller

Publications and source records attributed to N B Schiller.

At least 19 recordsLinked to original sources
PubMed2003

Changes in regional left atrial function with aging: evaluation by Doppler tissue imaging.

AIMS: This study applies pulsed wave Doppler tissue imaging and colour Doppler tissue imaging to study changes in atrial function with ageing. We tested the following hypotheses: (1) pulsed wave Doppler tissue imaging can detect global changes of left atrial function associated with ageing similar to standard echocardiographic methods, (2) colour Doppler tissue imaging can reproducibly detect regional changes in atrial function (wall motion) of the normal young and normal aging atrium. METHODS AND RESULT: We studied 92 healthy subjects, divided into Group B (>or=50 years) and Group A (<50 years). As a reference standard the conventional measures of atrial function were determined: peak mitral A wave velocity, A wave velocity time integral, atrial emptying fraction and atrial ejection force. Pulsed wave Doppler tissue imaging estimated atrial contraction velocity (A' velocity) in late diastolic and segmental atrial contraction was determined by colour Doppler tissue imaging. A' velocities were significantly higher in Group B vs Group A (9.8+/-1.8 vs 8.5+/-1.5cm/s; P=0.0005). A' velocity correlated with atrial fraction (r=0.28; P=0.007) and atrial ejection force (r=0.21; P=0.04). Age correlated significantly with atrial ejection force (r=0.47; P=0.0001), atrial fraction (r=0.61; P=0.0001) and A' velocity (r=0.4; P=0.0002). Longitudinal segmental atrial contraction using colour Doppler tissue imaging showed an annular to superior segment decremental gradient with contraction velocities higher in Group B vs Group A. CONCLUSION: Pulsed wave Doppler tissue imaging and colour Doppler tissue imaging are reproducible and readily obtained parameters that provide unique data about global and segmental atrial contraction. In this study, changes in atrial contraction with aging were consistent with increased atrial contribution to filling accomplished by augmented atrial contractility.

Adolescent↗
PubMed2001

Usefulness of stroke distance by echocardiography as a surrogate marker of cardiac output that is independent of gender and size in a normal population.

Left ventricular outflow tract stroke distance (SD) can be measured using pulsed-wave Doppler echocardiography, and is independent of body size. Moreover, persons with structurally normal hearts (heart rate < 55 beats/min) had SD > 0.18 m, and those with a heart rate > 95 beats/min had SD < 0.22 m; outside of these parameters, low- and high-output states are likely to exist, and suspicion of these can be confirmed by calculation of minute distance (normal range 9.7 to 20.5 m/min).

Adult↗
PubMed2001

The adequacy of basic intraoperative transesophageal echocardiography performed by experienced anesthesiologists.

UNLABELLED: Transesophageal echocardiography (TEE) may improve intraoperative decision-making and patient outcome if it is performed and interpreted correctly. After revising our TEE examination to fulfill the published guidelines for basic TEE practitioners, we prospectively evaluated the ability of our cardiac anesthesiologists (all very experienced with TEE) to record and interpret this revised examination. Educational aids and regular TEE performance feedback were provided to the anesthesiologists. Their interpretations were compared with the independently determined results of experts. Compared with their own historical controls (42% recording rate), all anesthesiologists showed significant improvement in their ability to record a basic intraoperative TEE examination resulting in 81% (P < 0.0001) of all required images being recorded: 88% before cardiopulmonary bypass, 77% immediately after bypass, and 64% after chest closure. Seventy-nine percent of the images recorded at baseline were correctly interpreted, 6% were incorrectly interpreted, and 15% were not evaluated. Our attempt to assess compliance with published guidelines for basic intraoperative TEE resulted in a marked improvement in our intraoperative TEE practice. Most, but not all, standard cross-sections are recorded or interpreted correctly, even by highly experienced and motivated practitioners. IMPLICATIONS: Experienced cardiac anesthesiologists can obtain and correctly interpret most basic intraoperative transesophageal echocardiograms.

Anesthesiology↗
PubMed2000

Cardiovascular effects of 3,4-methylenedioxymethamphetamine. A double-blind, placebo-controlled trial.

BACKGROUND: The psychoactive stimulant 3, 4-methylenedioxymethamphetamine (MDMA), also known as "ecstasy," is widely used in nonmedical settings. Little is known about its cardiovascular effects. OBJECTIVE: To evaluate the acute cardiovascular effects of MDMA by using transthoracic two-dimensional and Doppler echocardiography. DESIGN: Four-session, ascending-dose, double-blind, placebo-controlled trial. SETTING: Urban hospital. PATIENTS: Eight healthy adults who self-reported MDMA use. INTERVENTION: Echocardiographic effects of dobutamine (5, 20, and 40 microg/kg of body weight per minute) were measured in a preliminary session. Oral MDMA (0.5 and 1.5 mg/kg of body weight) or placebo was administered 1 hour before echocardiographic measurements in three weekly sessions. MEASUREMENTS: Heart rate and blood pressure were measured at regular intervals before and after MDMA administration. Echocardiographic measures of stroke volume, ejection fraction, cardiac output, and meridional wall stress were obtained 1 hour after MDMA administration and during dobutamine infusions. RESULTS: At a dose of 1.5 mg/kg, MDMA increased mean heart rate (by 28 beats/min), systolic blood pressure (by 25 mm Hg), diastolic blood pressure (by 7 mm Hg), and cardiac output (by 2 L/min). The effects of MDMA were similar to those of dobutamine, 20 and 40 microg/kg per minute. Inotropism, measured by using meridional wall stress corrected for ejection fraction, decreased after administration of dobutamine, 40 microg/kg per minute, but did not change after either dose of MDMA. CONCLUSIONS: Modest oral doses of MDMA increase heart rate, blood pressure, and myocardial oxygen consumption in a magnitude similar to dobutamine, 20 to 40 microg/kg per minute. In contrast to dobutamine, MDMA has no measurable inotropic effects.

Administration, Oral↗
PubMed2000

Hemodynamics derived from transesophageal echocardiography (TEE).

Table 1 lists the parameters that are sought routinely in developing a complete hemodynamic profile by TEE. The arterial blood pressure is an essential starting point. Knowledge of the cardiac output (flow velocity integral) allows placement of the other parameters in context by providing a notion of the status of the general circulation and of the level of pulmonary and systemic vascular resistance. The mitral inflow allows segregation of the diastolic function of the left ventricle into one of three categories: (1) normal, (2) restrictive, or (3) delayed relaxation. Pulmonary vein inflow is complementary to mitral inflow and further confirms the status of the filling pressure. The MR jet is another means of gauging the systemic blood pressure and the filling pressure but is more technically demanding than recording mitral valve and pulmonary valve inflows. Tricuspid regurgitation, also technically demanding, reliably provides peak pulmonary systolic pressure, and PR provides the end-diastolic pulmonary artery pressure. Doppler [table: see text] flow in the great veins is useful in estimating right atrial pressure; this information must be integrated with TR and PR velocities to estimate pulmonary artery pressure. Finally, the motion and curvature direction of the IAS allows identification of the atrium with the higher pressure. Using the dynamic behavior of this structure enables reconstructing of the pressure in one atrium from knowledge of pressure in the other. As the case example shows, using these techniques in a routine fashion enables an accurate, comprehensive, and reliable qualitative assay of hemodynamic status.

Echocardiography, Transesophageal↗
PubMed2000

Determinants of forward pulmonary vein flow: an open pericardium pig model.

OBJECTIVE: To elucidate determinants of pulmonary venous (PV) flow. BACKGROUND: Right ventricular (RV) systolic pressure (vis a tergo), left atrial (LA) relaxation and left ventricular (LV) systole and relaxation (vis a fronte) have been suggested as determinants of the pulmonary venous (PV) anterograde Doppler flow velocities, but their relative contributions to those flow velocities have not been quantified. METHODS: We analyzed, by multiple regression analysis, the determinants of PV anterograde velocities in an open-pericardium, paced (70 and 90 beats/min) pig model in which LA afterload was modified by creating LV regional ischemia (left anterior descending coronary artery constriction). We measured high fidelity LA, LV and RV pressures and Doppler flow velocities (epicardial echocardiography). We calculated LV tau, LA relaxation (a through x pressure difference divided by time, normalized by a pressure), LA peak v through x and RV systolic through LA peak v (RVSP-v) pressure differences, LV ejection fraction, long-axis shortening, stroke volume (LV outflow integral x outflow area) and LA four-chamber dimensions, Doppler transmitral and PV flow velocities and velocity-time integrals. RESULTS: Left ventricular regional ischemia increased mildly LA y trough pressure (8 +/- 1 vs. 6 +/- 1 mm Hg, p = 0.001). Left ventricular stroke volume (coefficient: 0.5 cm/ml, SE: 0.2, p = 0.005) and LA peak v pressure (coefficient: -0.8 cm/mm Hg, SE: 0.3, p = 0.008) determined the PV total systolic integral. Left atrial relaxation determined both PV early systolic peak velocity and integral (coefficient: -0.8 cm/mm Hg, SE: 0.3, p = 0.04). Left atrial maximum area (coefficient: 2 cm(-1) SE: 0.7, p = 0.01) and RVSP-v (coefficient: 0.1 cm/mm Hg, SE: 0.05, p = 0.03) determined the late systolic integral. The PV total systolic integral determined both PV early diastolic peak velocity and integral (coefficient: 1.2, SE: 0.2, p = 0.001). CONCLUSIONS: In an experimental model of LV acute ischemia of limited duration, the main independent predictors of PV systolic anterograde flow velocities are LA relaxation and compliance (LA peak v pressure) and LV systole--all vis a fronte factors. In the setting of mildly increased LA pressures, PV systolic flow (LA reservoir filling) is an independent predictor of PV early diastolic flow (LA early conduit).

Animals↗
PubMed2000

Fatigue, mood, and hemodynamic patterns after myocardial infarction.

A descriptive design with repeated measures was used to describe patterns of fatigue, emotional stress, and left ventricular (LV) function among 22 patients with myocardial infarction (MI) from day 5 postadmission to day 21 postadmission for the MI. The severity of fatigue in patients with MI during the subacute period ranged from 32 to 44 on the 100-mm Visual Analogue Scale for Fatigue. Severity of fatigue and depression remained the same; however, LV function improved (p < .01) and patients experienced more energy (p < .01) and less anxiety (p < .01) in the third week following MI. Researchers observed five different fatigue patterns: decreasing fatigue, increasing fatigue, unchanged low fatigue, unchanged-high fatigue, and a curvilinear fatigue pattern. The finding of five different fatigue patterns after an MI suggests that all patients with MI should not be treated as a uniform group assumed to have decreasing fatigue with the passage of time.

Adult↗
PubMed1999

Best method in clinical practice and in research studies to determine left atrial size.

Although the anteroposterior dimension of the left atrium is universally used in clinical practice and research, we hypothesized that it may be an inaccurate surrogate for volume because its use is based on the unlikely assumption that there is a constant relation among atrial dimensions. The following measurements of the left atrium were made at end ventricular systole: (1) M-mode-derived anteroposterior linear dimension from the parasternal long-axis view; (2) digitized planimetry of the left atrial (LA) cavity from the apical 4-chamber view; and (3) digitized planimetry of the LA cavity from the apical 2-chamber view. The following volume calculations were obtained from these digital measurements: (1) volume derived from the M-mode dimension assuming a spherical shape; (2) volume derived from the single plane area-length of apical 4-chamber view, which assumes that LA geometry can be generalized from a single 2-dimensional plane; and (3) volume derived from the biplane method of discs. The correlation coefficient between the M-mode and biplane methods of determining LA volume was r = 0.76. The mean difference (+/-2 SDs) between these methods is -25 +/- 33 ml. The correlation coefficient between the single plane apical 4-chamber and biplane methods of determining LA volume is r = 0.97. The mean difference (+/-2 SDs) between these methods was -5.0 +/- 12 ml, indicating good agreement. The M-mode measure of the left atrium is an inaccurate representation of its size. Two-dimensional-derived LA volumes provide a more accurate measure of the true size of the left atrium and are more sensitive to changes in LA size. When an echocardiographic measure of LA size is made either in an individual patient or as a variable in a research study, the M-mode measure should be avoided.

Adolescent↗
PubMed1999

Left atrial relaxation and left ventricular systolic function determine left atrial reservoir function.

BACKGROUND: Determinants of left atrial (LA) reservoir function and its influence on left ventricular (LV) function have not been quantified. METHODS AND RESULTS: In an open-pericardium, paced (70 and 90 bpm) pig model of LV regional ischemia (left anterior descending coronary constriction), with high-fidelity LV, LA, and RV pressure recordings, we obtained the LA area with 2D automated border detection echocardiography, LA pressure-area loops, and Doppler transmitral flow. We calculated LV tau, LA relaxation (a-x pressure difference divided by time, normalized by a pressure), and stiffness (slope between x and v pressure points of v loop). Determinants of total LA reservoir (maximum-minimum area, cm(2)) were identified by multiple regression analysis. Different mean rates of LA area increase identified 2 consecutive (early rapid and late slow) reservoir phases. During ischemia, LV long-axis shortening (LAS, LV base systolic descent) and LA reservoir area change decreased (7.3+/-0.3 [SEM] versus 5.6+/-0.3 cm(2), P<0.001) and LA stiffness increased (1.6+/-0.3 versus 3.1+/-0.3 mm Hg/cm(2), P=0.009). Early reservoir area change depended on LA mean ejection rate (LA area at ECG P wave minus minimum area divided by time; multiple regression coefficient=0.9; P<0.001) and relaxation (coefficient=4.9 cm(2)xms/s; P<0.001). Late reservoir area change depended on LAS (coefficient=8 cm/s; P<0.001). Total reservoir filling depended on LA stiffness (coefficient=-0.31 cm(4)/mm Hg; P=0. 001) and cardiac output (coefficient=0.001 cm(2)xmin/L; P=0.002). The strongest predictor of cardiac output was LA reservoir filling (coefficient=301 L/minxcm(2); P<0.001). The v loop area was determined by cardiac output, LV ejection time, tau, and early transmitral flow. CONCLUSIONS: Two (early and late) reservoir phases are determined by LA contraction and relaxation and LV base descent. Acute LV regional ischemia increases LA stiffness and impairs LA reservoir function by reducing LV base descent.

Animals↗
PubMed1999

Echocardiography in patients with suspected endocarditis: a cost-effectiveness analysis.

PURPOSE: We sought to determine the appropriate use of echocardiography for patients with suspected endocarditis. PATIENTS AND METHODS: We constructed a decision tree and Markov model using published data to simulate the outcomes and costs of care for patients with suspected endocarditis. RESULTS: Transesophageal imaging was optimal for patients who had a prior probability of endocarditis that is observed commonly in clinical practice (4% to 60%). In our base-case analysis (a 45-year-old man with a prior probability of endocarditis of 20%), use of transesophageal imaging improved quality-adjusted life expectancy (QALYs) by 9 days and reduced costs by $18 per person compared with the use of transthoracic echocardiography. Sequential test strategies that reserved the use of transesophageal echocardiography for patients who had an inadequate transthoracic study provided similar QALYs compared with the use of transesophageal echocardiography alone, but cost $230 to $250 more. For patients with prior probabilities of endocarditis greater than 60%, the optimal strategy is to treat for endocarditis without reliance on echocardiography for diagnosis. Patients with a prior probability of less than 2% should receive treatment for bacteremia without imaging. Transthoracic imaging was optimal for only a narrow range of prior probabilities (2% or 3%) of endocarditis. CONCLUSION: The appropriate use of echocardiography depends on the prior probability of endocarditis. For patients whose prior probability of endocarditis is 4% to 60%, initial use of transesophageal echocardiography provides the greatest quality-adjusted survival at a cost that is within the range for commonly accepted health interventions.

Adult↗
PubMed1999

The Mitral Regurgitation Index: an echocardiographic guide to severity.

OBJECTIVES: The purpose of this study was to develop a semiquantitative index of mitral regurgitation severity suitable for use in daily clinical practice and research. BACKGROUND: There is no simple method for quantification of mitral regurgitation (MR). The MR Index is a semiquantitative guide to MR severity. The MR Index is a composite of six echocardiographic variables: color Doppler regurgitant jet penetration and proximal isovelocity surface area, continuous wave Doppler characteristics of the regurgitant jet and tricuspid regurgitant jet-derived pulmonary artery pressure, pulse wave Doppler pulmonary venous flow pattern and two-dimensional echocardiographic estimation of left atrial size. METHODS: Consecutive patients (n = 103) with varying grades of MR, seen in the Adult Echocardiography Laboratory at UCSF, were analyzed retrospectively. All patients were evaluated for the six variables, each variable being scored on a four point scale from 0 to 3. The reference standards for MR were qualitative echocardiographic evaluation by an expert and quantitation of regurgitant fraction using two-dimensional and Doppler echocardiography. A subgroup of patients with low ejection fraction (EF < 50%) were also analyzed. RESULTS: The MR Index increased in proportion to MR severity with a significant difference among the three grades in both normal and low EF groups (F = 130 and F = 42, respectively, p < 0.0001). The MR Index correlated with regurgitant fraction (r = 0.76, p < 0.0001). An MR Index > or =2.2 identified 26/29 patients with severe MR (sensitivity = 90%, specificity = 88%, PPV = 79%). No patient with severe MR had an MR Index <1.8 and no patient with mild MR had an MR Index >1.7. CONCLUSIONS: The MR Index is a simple semiquantitative estimate of MR severity, which seems to be useful in evaluating MR in patients with a low EF.

Adult↗
PubMed1999

The diagnostic validity of digitally captured intraoperative transesophageal echocardiography examinations compared with analog recordings: A pilot study.

BACKGROUND: Digital acquisition and storage of echocardiographic studies offer many advantages over analog recordings, but the amount of computer memory required may be large. "Computer compression" of data is done by machines with various algorithms. "Clinical compression" involves limiting the recordings to 1-beat loops, and although it is commonly used, its diagnostic validity has not been demonstrated in the operating room. METHODS: This prospective pilot study looked at 51 patients undergoing transesophageal echocardiography during cardiac surgery. During continuous videocassette recording, we captured digital loops to demonstrate wall motion abnormalities, ventricular systolic function, aortic insufficiency, and mitral regurgitation. Experts reviewed the loops and tapes. We then compared the diagnoses from the 2 methods. RESULTS: There were major differences in the diagnosis of wall motion between loops and tapes in only 3.4% of myocardial segments. No major differences were seen in the diagnosis of systolic function, aortic insufficiency, or mitral regurgitation in any patients. CONCLUSION: We conclude that clinical compression is a suitable method to compress data in the operating room. Large numbers of patients are required to definitively demonstrate the small differences.

Chi-Square Distribution↗
PubMed1999

Demonstration of penetrating intramyocardial coronary arteries with high-frequency transthoracic echocardiography and Doppler in human subjects.

Characterization of intramyocardial coronary artery flow may offer insight into the spectrum of coronary physiology. The purposes of this study were to test the feasibility of detection and measurement of intramyocardial coronary artery flow by using high-frequency transthoracic ultrasound and to evaluate the hemodynamic and morphologic differences in intramyocardial coronary arteries between patients with echocardiographically normal myocardium and patients with diseased myocardium. In 116 subjects (age 58 +/- 19 years; male:female 67:49; 58 normal [control subjects], 40 with left ventricular hypertrophy [LVH], 18 with systolic left ventricular dysfunction [cardiomyopathy, CM]), we examined the myocardium just beneath the apical impulse window at a depth of 3 to 5 cm by using a 6- or 7-MHz centerline frequency transducer. For color Doppler examination, a special preset coronary program with a low Nyquist limit (12 to 20 cm) was used. After obtaining linear color signals, the width and length, peak and mean diastolic pulsed Doppler flow velocities, diastolic velocity time integrals, and percent duration of diastolic Doppler flow were measured. The number of linear color flow signals per square centimeter was counted in 520 different cardiac cycles, and the angles formed by their inner curvature was measured with a graduated protractor. We identified color flow Doppler signals within the myocardium having a mean width of 1.1 +/- 0.4 mm and flow direction from epicardium to endocardium in 104 (89. 7%) subjects and spectral Doppler signals in 74 (63.8%) subjects. In 33 (45.8%) subjects, only diastolic flow was detected and in 39 (54. 2%) subjects, diastolic flow was predominant with systolic reversal. Peak and mean diastolic flow velocities and velocity time integrals of spectral Doppler signal in control subjects were 26.2 +/- 8.6 cm/s, 19.0 +/- 6.3 cm/s, and 9.5 +/- 2.7 cm, respectively. There were no significant differences in width and density of linear color flow signals among the 3 groups. The color flow signals in the LVH and CM groups had a narrower angle of inner curvature (P <.005 for LVH, P <.05 for CM, respectively), and their spectral Doppler signals showed significantly higher diastolic velocities and shorter diastolic flow duration (P <.005 for LVH, P <.05 for CM, respectively) than those of the control subjects. Detection and measurement of flow signals consistent with penetrating intramyocardial coronary arteries are feasible in a high percentage of subjects by use of high-frequency transthoracic ultrasound. The findings in patients with LVH and CM suggest that there are distinct hemodynamic and morphologic departures from those with normal left ventricles that may be a consequence of disordered myocardial perfusion in diseased myocardium.

Blood Flow Velocity↗