Biomedical subjects

Thomas D Stamos

Publications and source records attributed to Thomas D Stamos.

3 recordsLinked to original sources

PubMed2005

Using impedance cardiography to assess left ventricular systolic function via postural change in patients with heart failure.

For the diagnosis and management of heart failure, it would be useful to have a simple point-of-care test for assessing ventricular function that could be performed by a nurse. An impedance cardiography (ICG) parameter called systolic amplitude (SA) can serve as an indicator of left ventricular systolic function (LVSF). This study tested the hypothesis that patients with normal LVSF should have a significant increase in SA in response to an increase in end-diastolic volume caused by postural change from sitting upright to supine, while patients with depressed LVSF associated with heart failure should have a minimal increase or a decrease in SA from upright to supine. ICG data were obtained in 12 patients without heart disease and with normal LVSF and 18 patients with clinically diagnosed heart failure. Consistent with the hypothesis, patients with normal LVSF had a significant increase in SA from upright to supine, whereas heart failure patients had a minimal increase or a decrease in SA from upright to supine. This ICG procedure may be useful for monitoring the trend of patient response to titration of beta blockers and other medications. ICG potentially could be used to detect worsening LVSF and provide a means of measurement for adjusting treatment.

Adrenergic beta-Antagonists↗

PubMed2004

Automated volumetric flow quantification using angle-corrected color Doppler image.

We have developed a fully automated method for measuring volumetric blood flow with angle-corrected blood velocity from a color Doppler image. By computing the blood flow vector through a conduit, the angle of incidence between the direction of ultrasound beam and the direction of blood flow can be measured to correct the underestimated blood velocity. This correction immediately contributes to the improvement of measurement accuracy. The developed method also enhances the conduit identification procedure that is one of the most important factors affecting the accuracy of volumetric measurement. To evaluate the validity of the developed algorithm, experimental studies had been applied to 21 healthy subjects and 10 patients. Volumetric flows were measured from a color Doppler image of the left ventricular outflow track, which were compared with blood volumes that were measured by traditional pulsed-wave (PW)-Doppler technique. The mean stroke volume difference between two methods was -0.45 +/- 11.7 (mean +/- SD). The proposed algorithm is a viable method for determining blood flow volume in an automated fashion.

Blood Flow Velocity↗

PubMed2002

Utility of history, physical examination, electrocardiogram, and chest radiograph for differentiating normal from decreased systolic function in patients with heart failure.

To determine whether clinical parameters alone can differentiate normal versus decreased systolic left ventricular function in patients with heart failure. Detailed clinical data were collected prospectively from 225 consecutive patients who were hospitalized with heart failure. Findings in patients with normal (ejection fraction > or =45%) or decreased (ejection fraction <45%) left ventricular function were compared. Systolic function was normal in 104 patients (46%) and decreased in 121 patients (54%). Patients with normal function were older (mean [+/- SD] age, 59 +/- 13 years vs. 54 +/- 13 years, P = 0.007) and more likely to be female (56% vs. 35%, P = 0.001), obese (body mass index > or =30 kg/m(2), 62% vs. 48%, P = 0.04), have marked systolic (> or =160 mm Hg, 50% vs. 27%, P <0.001) and diastolic (> or =110 mm Hg, 25% vs. 13%, P = 0.02) hypertension, and use calcium antagonists (34% vs. 14%, P = 0.001). Patients with decreased function were more likely to use alcohol (37% vs. 20%, P = 0.007), angiotensin-converting enzyme (ACE) inhibitors (85% vs. 62%, P <0.001), and digoxin (57% vs. 27%, P <0.001); and more likely to have tachycardia (51% vs. 32%, P = 0.004), rales (89% vs. 80%, P = 0.05), electrocardiographic left ventricular hypertrophy (42% vs. 22%, P = 0.002), left atrial abnormality (52% vs. 22%, P <0.001), or flow cephalization on chest radiograph (91% vs. 79%, P = 0.02). Only sex, tachycardia, and use of digoxin and ACE inhibitors were associated with ventricular function in multivariable analysis. However, the sensitivity, specificity, and predictive values for all clinical variables were low. Differences in clinical parameters in heart failure patients with decreased versus normal systolic function cannot predict systolic function in these patients, supporting recommendations that heart failure patients should undergo specialized testing to measure ventricular function.

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