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Biomedical subjects

A N DeMaria

Publications and source records attributed to A N DeMaria.

At least 127 records · Page 7Linked to original sources
PubMed1989

Effect of heart rate on Doppler indexes of systolic function in humans.

Recent investigations have shown Doppler echocardiography to be useful in the noninvasive assessment of left ventricular systolic function. No data exist, however, regarding the influence of heart rate on Doppler measurements of aortic blood flow velocity and acceleration in humans. Thus, 12 normal volunteers underwent continuous wave Doppler ultrasound recording from the suprasternal notch at baseline and during progressive transesophageal atrial pacing at intervals of 10 beats/min between 90 and 140 beats/min while 100% atrial capture and 1:1 atrioventricular conduction were maintained. Subjects were studied both upright (n = 12) and supine (n = 10). With the subject upright at baseline (mean heart rate 77.8 +/- 10.6 beats/min), peak acceleration averaged to 16.8 +/- 3.4 m/s2, and peak modal velocity and flow velocity integral averaged 0.72 +/- 0.14 m/s and 8.4 +/- 2.1 cm, respectively. With pacing at 90 beats/min, peak acceleration decreased to 15.6 +/- 3.6 m/s2, a significant decline from baseline values (p less than 0.005). Similar declines were seen during pacing at 90 beats/min for peak modal velocity and flow velocity integral (0.64 +/- 0.16 m/s and 7.1 +/- 1.9 cm, respectively; both p less than 0.005 versus baseline values). At the peak pacing rate of 140 beats/min, average peak acceleration decreased to 12.8 +/- 3.1 m/s2, and peak modal velocity and flow velocity integral decreased to 0.52 +/- 0.11 m/s and 5.02 +/- 1.25 cm, respectively. A significant linear correlation (r greater than or equal to 0.97, p less than 0.0001) was obtained for the relation between heart rate and peak acceleration, peak modal velocity and flow velocity integral.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Nonuniformity of the transmural distribution of coronary blood flow during the cardiac cycle. In vivo documentation by contrast echocardiography.

This study was performed to examine the transmural (endocardial vs. epicardial) heterogeneity of myocardial blood flow during the cardiac cycle (systole vs. diastole). Twenty-four contrast echocardiographic injections were performed in seven open-chest anesthetized dogs either into left anterior descending or circumflex coronary artery or into the aortic root. Two-dimensional echocardiography in short-axis view was performed and was digitized off-line into a 256 x 256 pixel matrix with 256 gray levels/pixel. All end-diastolic and end-systolic frames before and to peak contrast were analyzed. A region of interest corresponding to the most intensely opacified myocardial segment was traced, the mean videodensity measured, and the frame of initial contrast appearance detected. The region of interest was divided into three equal parallel layers corresponding to the endocardial, midcardial, and epicardial myocardium. When the echocardiographic contrast effect initially appeared in diastole, the increment in videodensity was greater for the endocardium (131 +/- 48%) than for the epicardium (71 +/- 37% of the increment in videodensity of the entire wall) (p less than 0.05). This inhomogeneity subsequently disappeared in the following end-systolic frame. When the initial echocardiographic contrast effect appeared in systole, intensity was higher in epicardium (136 +/- 83%) than in endocardium (60 +/- 60%) (p less than 0.05). However, in the following diastole, intensity was not significantly different for the two layers. Thus, myocardial contrast echocardiography demonstrates that coronary blood flow is primarily subendocardial in distribution during diastole and subepicardial during systole.

Animals↗
PubMed1988

Pivotal role of aortic valve area calculation by the continuity equation for Doppler assessment of aortic stenosis in patients with combined aortic stenosis and regurgitation.

Aortic regurgitation (AR) may result in overestimation of the aortic pressure gradient by continuous wave Doppler in patients with mixed aortic valve disease. However, few data are available regarding the effect of AR on noninvasive estimates of aortic valve area by the continuity equation. Therefore, 25 patients with angiographically documented severe AR and peak systolic aortic velocities of greater than 2.5 m/s were studied by continuous wave Doppler to determine the accuracy of pressure gradient and aortic valve area calculations in assessing the severity of aortic stenosis (AS) in this patient population. Peak instantaneous pressure gradient showed a general correlation to but was overestimated by Doppler (r = 0.78, Doppler = 0.70 catheter + 19.9) and did not predict aortic valve area. Mean pressure gradient by Doppler correlated more closely with catheter mean gradient (r = 0.86, Doppler = 0.79 catheter + 6.1) but was a poor predictor of the severity of AS. In contrast, the continuity equation accurately predicted the aortic valve area by catheterization (r = 0.92, Doppler = 0.89 catheter -0.08). Thus, the continuity equation provides a reliable estimate of aortic valve area in patients with severe AR and should be used to evaluate the extent of AS in such patients when high systolic aortic velocities are present.

Aortic Valve↗
PubMed1988

A practical application of Doppler echocardiography for the assessment of severity of aortic stenosis.

This study evaluated a strategy that makes optimal use of Doppler echocardiography for estimating the severity of valvular aortic stenosis (AS). Fifty-eight patients with no more than moderate aortic insufficiency who underwent cardiac catheterization were evaluated with two-dimensional echocardiography and Doppler velocimetry to determine the peak velocity across the stenotic valve and aortic valve area (AVA) by means of the continuity equation. All 33 peak Doppler velocities of greater than or equal to 4 m/sec had critical AS (AVA less than or equal to 0.8 cm2 at catheterization). Conversely, six of seven patients with Doppler velocities of less than or equal to 3 m/sec had noncritical AS. The patient with a falsely low peak velocity had severely depressed left ventricular function. Doppler velocity alone was inadequate in determining severity of AS for patients with velocities between 3 and 4 m/sec. The continuity equation proved accurate in estimating AVA in the 46 patients for whom catheterization and ultrasound data were sufficient to compare calculated AVA (r = 0.81), and was also accurate for those patients with peak Doppler velocities between 3 and 4 m/sec (r = 0.90). These results suggest that Doppler velocimetry alone is adequate in determining critical vs noncritical AS in many patients, while the continuity equation should be applied for patients with peak velocities between 3 and 4 m/sec as well as in patients with severely depressed cardiac function.

Adult↗
PubMed1988

Ethical activism.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Observer variability in the quantitation of Doppler color flow jet areas for mitral and aortic regurgitation.

Early studies using Doppler color flow imaging have suggested that measurement of the regurgitant jet area provides information regarding the severity of valvular insufficiency. This study was performed to assess the observer variability of mitral and aortic regurgitant jet area measurements using the Doppler color technique. Color Doppler recordings from 45 patients were reviewed: 23 patients had aortic regurgitation and 22 had mitral regurgitation. To assess interobserver variability, the largest definable mitral regurgitant jets from three cardiac cycles were independently chosen and measured by planimetry by two observers who were unaware of other patient information. Measurements were repeated by both observers at a separate time to obtain intraobserver data. Videotapes from 23 patients with aortic regurgitation were similarly analyzed. Each observer measured the isovolumic aortic jet (before mitral valve opening) and the maximal aortic regurgitant jet (at any time during diastole) using computer-assisted planimetry. Both intraobserver and interobserver correlations were excellent for mitral regurgitant jet areas (r = 0.97 and r = 0.93, respectively). The intraobserver correlation for isovolumic aortic regurgitant jet was r = 0.73; the interobserver correlation for this measurement was only fair (r = 0.57). For the maximal aortic regurgitant jet area, intraobserver correlation was good (r = 0.86) and interobserver correlation was fair (r = 0.72). These findings suggest that intraobserver and interobserver reproducibility are acceptable for the measurement of mitral regurgitant jet area.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Left ventricular distensibility and passive elastic stiffness in atrial septal defect.

Diminished left ventricular distensibility has been postulated as a cause of left ventricular failure in atrial septal defect. To evaluate this hypothesis the indexes of left ventricular compliance and stiffness were estimated in 15 patients with atrial septal defect and the results compared with those in 10 normal subjects. Age, peak left ventricular systolic pressure, end-diastolic pressure, ejection fraction and cardiac index did not differ significantly between groups. Left ventricular end-diastolic volume for the atrial septal defect group was significantly less than that for the control group (mean +/- SD, 61 +/- 9 ml/m2 versus 73 +/- 13, p less than 0.05) in keeping with previous studies. The slope of the log pressure-volume relation was significantly greater in the group with atrial septal defect than in the normal group (0.056 +/- 0.010 versus 0.044 +/- 0.008, p less than 0.01), consistent with increased chamber stiffness. For a group of six patients with atrial septal defect and elevated left ventricular end-diastolic pressure, normalized compliance was significantly less than that in the control group (0.017 +/- 0.001 versus 0.036 +/- 0.007, p less than 0.02). The slope k of the elastic stiffness-stress relation for the total group with atrial septal defect was significantly greater than that of the normal group (21.0 +/- 2.3 versus 18.1 +/- 2.3, p less than 0.01). An index of muscle fiber stretch (dV/VdP x end-diastolic stress x 100) was significantly less in the atrial septal defect group than in the control group (74 +/- 24 versus 106 +/- 22, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Use of exercise Doppler echocardiography to evaluate cardiac drugs: effects of propranolol and verapamil on aortic blood flow velocity and acceleration.

This study evaluated the ability of exercise Doppler echocardiography to identify hemodynamic changes due to cardiac medication. Twenty young healthy volunteers (mean age 30 years) underwent continuous wave Doppler examination from the suprasternal notch at rest, during each stage of a standard exercise protocol and immediately after exercise. On completion of the control test, each subject received either 60 to 80 mg of propranolol or 120 mg of verapamil orally, and the same exercise protocol was repeated after 90 min. During the control test, values for modal velocity, acceleration and flow velocity integral all increased significantly from baseline (p less than 0.0002 for each). When exercise was repeated after propranolol administration, values for all Doppler measurements were significantly altered. Modal velocity at baseline was significantly lower after propranolol when compared with control (0.53 +/- 0.11 versus 0.63 +/- 0.17 m/s; p less than 0.0001). Similarly, modal velocity at maximal exercise was significantly lower after propranolol (1.11 +/- 0.2 versus 1.25 +/- 0.21 m/s; p less than 0.0001). The effect of propranolol on acceleration was even greater, with blunting of baseline (11.4 +/- 2 versus 15.4 +/- 5 m/s per s; p less than 0.0005) and exertional (33.4 +/- 10 versus 56.3 +/- 15 m/s per s; p less than 0.0001) acceleration. The flow velocity integral during exercise was greater after propranolol (14.1 +/- 3.1 versus 10.1 +/- 3.2 cm; p less than 0.0005) than during the control test. Verapamil failed to influence any Doppler-measured index of aortic blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1988

fMLP provokes coronary vasoconstriction and myocardial ischemia in rabbits.

Recent pathological studies of coronary arteries from humans with suspected coronary spasm have revealed an augmented intramural burden of inflammatory cells. To test the hypothesis that inappropriate activation of inflammatory cells participates in the evolution of coronary vasospasm, the present experiments employed a newly developed coronary arteriographic technique for use in pentobarbital-anesthetized rabbits to evaluate the coronary vasomotor actions of the nonselective inflammatory cell stimulant, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP). In 10 of 10 animals, selective left intracoronary injection of 200 ng fMLP evoked profound left coronary narrowing accompanied in all cases by ST segment deviation and dysrhythmias. Thallium-201 scintigraphy demonstrated hypoperfusion of the left ventricular free wall and septum supplied by the spastic coronary artery. The fMLP-induced epicardial vaso-constriction, ischemic electrocardiogram (ECG) changes, and thallium perfusion defects were reversed by intravenous nitroglycerin. Neither the right coronary artery nor its distribution were influenced by left coronary injection of fMLP. Additional experiments in isolated, salt solution-perfused rabbit hearts demonstrated that fMLP failed to exert direct coronary vasoconstrictor effects. These observations indicate that the non-selective inflammatory cell stimulant, fMLP, provokes arteriographically demonstrable coronary spasm with attendant myocardial hypoperfusion and ischemic ECG changes in anesthetized rabbits. Such a model may be useful in exploring the dynamic role of inflammatory cells in development of coronary spasm.

Angiography↗
PubMed1988

Comparison of simultaneously performed digital and film-based angiography in assessment of coronary artery disease.

This study compared digital angiography (Digital) to conventional cineangiography (Cine) for the diagnosis and quantification of coronary artery disease. Digital and Cine were obtained simultaneously under identical radiographic conditions during routine coronary arteriography. Using visual inspection and manual calipers, four independent observers identified 131 stenoses in 18 patients with multivessel coronary disease. There was no difference in interobserver variability between Digital and Cine during multiple subgroup analyses. Overall, Digital yielded significantly greater estimates of stenosis severity than did either of two separate Cine observations (p less than 0.0001; average difference, 6.25%), but the differences fell below the level of statistical significance when only the group of stenoses 50% or greater were considered. Digital and Cine correlated well for the assessment of stenosis severity (r = 0.88), but linear regression comparisons of multiple subgroups consistently indicated modest overestimation of Cine by Digital. Smaller vessels, branch vessels, and mild lesions increased the likelihood of overestimation by Digital. Digital was highly sensitive for identification of clinically relevant stenoses, but less specific and less predictive than a second observation of Cine. Our results indicate that Digital and Cine are not interchangeable imaging techniques and that potential differences must be considered when Digital is used for clinical decision making.

Angiography↗
PubMed1987

Effect of aortic regurgitation on the assessment of mitral valve orifice area by Doppler pressure half-time in mitral stenosis.

Evaluation of the severity of mitral stenosis by continuous-wave Doppler pressure half-time measurement is now well established. However, few data exist regarding the effect of aortic regurgitation (AR) on the validity of this method. Therefore, 73 patients were studied in whom cardiac catheterization and Doppler echocardiographic examinations were performed. Mitral valve orifice area was determined by the Gorlin equation, 2-dimensional echocardiography and Doppler pressure half-time. Doppler pressure half-time and catheterization estimates of mitral valve area correlated well (r = 0.85) in patients without significant mitral regurgitation. This correlation was maintained in patient subgroups with and without significant (at least 2+) AR (r = 0.86 and 0.83, respectively). Similarly, Doppler and 2-dimensional echocardiographic assessment of mitral valve area showed a strong correlation (r = 0.84). Again, the correlation between the 2 methods was similar in patients with and without significant AR (r = 0.86 and 0.82, respectively). Thus, Doppler pressure half-time estimates of mitral valve orifice area are accurate even in patients with AR.

Adult↗
PubMed1987

Determination of left ventricular ejection fraction by computer densitometric analysis of digital subtraction angiography: experimental validation and correlation with area-length methods.

Conventional methods for calculating left ventricular (LV) ejection fraction (EF) require accurate edge definition and geometric assumptions, which may be compromised in the presence of dyssynergy. Computer densitometric analysis (CDA) of digital subtraction angiography offers the potential for calculation of EF, independent of LV shape, by comparing summated brightness for regions of interest at end diastole and end systole. Therefore, the accuracy of CDA was validated for 2 mechanical heart models of differing geometry, spherical and rectangular. Both models confirmed the close correlation between calculated and measured EF (r = 0.98 and r = 0.99, respectively). Subsequently, the CDA was compared with single and biplane area-length EF calculations in 72 patients, half with a previous myocardial infarction. In patients without previous myocardial infarction, CDA correlated closely with both single-plane and biplane EF (r = 0.91 and 0.93, respectively). The close correlation was maintained regardless of whether CDA was applied to direct LV injection or intravenous digital subtraction angiography. However, in 36 patients with previous myocardial infarction, CDA correlated less closely with single-plane (r = 0.74) than with biplane (r = 0.86) area-length EF. Thus, CDA permits calculation of EF without geometric assumptions, and may be superior to the area-length method in patients with LV dyssynergy after myocardial infarction.

Adult↗