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D Thys

Publications and source records attributed to D Thys.

12 recordsLinked to original sources
PubMed1998

Recommendations for training in performance and interpretation of stress echocardiography. Committee on Physician Training and Education of the American Society of Echocardiography.

Stress echocardiography has emerged as a clinically useful procedure in the management of patients with ischemic heart disease and other conditions. However, the accuracy of this test relies on the ability of those who carry out the technical aspects of the test and depends critically on proper interpretation of the images. Appreciation of wall motion abnormalities is generally acknowledged as one of the most difficult skills to master in echocardiography. There is consensus that this is also one of the most difficult skills to teach. Appreciating stress-induced changes in wall motion, which sometimes are subtle, requires a significant commitment to initial training in this skill and its maintenance. This document provides recommendations for physician training in stress echocardiography.

Cardiology↗
PubMed1997

An algorithm for real-time, continuous evaluation of left ventricular mechanics by single-beat estimation of arterial and ventricular elastance.

We describe a computer algorithm that allows continuous, real-time evaluation of ventricular elastance (Ees), arterial elastance (Ea), and their coupling ratio in a clinical setting. In the conventional pressure-volume analysis of left ventricular (LV) contractility, invasive methods of volume determination and a significant, rapid preload reduction are required to generate Ees. With the help of automated border detection by transesophageal echocardiography, and a technique of estimating peak LV isovolumic pressure, Ea and Ees were determined from a single cardiac beat without the need for preload reduction. A comparison of results obtained by a conventional approach and the new algorithm technique, showed good correlation for Ea (r = 0.86, p < 0.001) and Ees (r = 0.74, p = 0.001). Bias analysis showed a bias (d) of 1.47 mmHg/cm2 for Ea with a standard deviation (SD) of 7.03 mmHg/cm2, and upper (d+2SD) and lower(d-2SD) limits of agreement of 15.24 mmHg/cm2 and -12.31 mmHg/cm2, respectively. Bias analysis showed a bias of -1.42 mmHg/cm2 for Ees with a SD of 4.88 mmHg/cm2, and limits of agreement of 8.15 mmHg/cm2 and -10.98 mmHg/cm2. The algorithm's stability to artifacts was also analyzed by comparing magnitudes of residuals of Ea and Ees from source signals with and without noise. With Ea differing by an average of 1.036 mmHg/cm2 and Ees differing by an average of 0.836 mmHg/cm2, the algorithm was found to be stable to artifacts in the source signals.

Algorithms↗
PubMed1996

Supine approach to the sciatic nerve in the popliteal fossa.

PURPOSE: Sciatic nerve block in the popliteal fossa (popliteal nerve block, PNB) is an anaesthetic technique well-suited for operations below the knee. However, difficulty with positioning the patient in the prone position often precludes the classical, posterior approach to the block. In this report, an alternative approach to PNB that can easily be performed with a patient in the supine position is described. CLINICAL FEATURES: Three patients in whom the clinical circumstances precluded the use of the classical approach to PNB are described. In each case, PNB was performed using the alternative, supine approach. With a patient in the supine position, the leg is flexed at both the hip and knee, and supported by an assistant. After the anatomical landmarks of the popliteal fossa are identified, an insulated needle attached to a peripheral nerve stimulator is inserted 7 cm above the popliteal crease, 1 cm laterally to the midline and directed 45 degrees cephalad. Upon obtaining either dorsal or plantar flexion of the foot at the output current of 0.5 mAmp or less. 30-40 ml of local anaesthetic solution are injected. CONCLUSION: The supine approach to PNB allows the use of the block in patients that cannot be positioned in the prone position. Flexion of the leg at the knee greatly facilitates identification of the anatomical landmarks. When combined with a block of the femoral or saphenous nerve, this technique provides excellent anaesthesia for patients undergoing foot and ankle surgery.

Adult↗
PubMed1994

Cardiac output by transesophageal echocardiography using continuous-wave Doppler across the aortic valve.

BACKGROUND: The use of transesophageal echocardiography for the determination of cardiac output (CO) has been limited to date. We assessed the capability of aortic continuous-wave Doppler transesophageal echocardiography to determine CO (DCO) in a transgastric long-axis imaging plane of the heart by comparing DCO to thermodilution CO (TCO). METHODS: DCO was determined in 63 consecutive patients undergoing cardiac surgery. Aortic valve area was obtained from the transverse short-axis view of the valve assuming a triangular shape for the valve orifice. Stroke volume was calculated as the product of velocity-time integral and aortic valve area: stroke volume = velocity-time integral x aortic valve area. DCO was calculated off-line, by multiplying stroke volume with heart rate: DCO = stroke volume x heart rate. RESULTS: The aortic valve orifice was easily imaged in all patients. Excellent-quality continuous-wave Doppler flow profiles were obtained in nearly all (62 of 63). A total of 109 DCO determinations were performed. Mean DCO was 4.35 +/- 1.18 l.min-1 (range 2.02-7.42 l.min-1), and mean TCO was 4.41 +/- 1.17 l.min-1 (range 2.24-8.94 l.min-1). Very high correlation and agreement were found between the two methods: DCO = 0.94 x TCO + 0.19, r = 0.94, SEE (standard error of the estimate) = 0.41 l.min-1; 95% confidence interval = 0.06 +/- 0.83 l.min-1. Relative changes from pre- to postbypass CO (delta) also showed a strong correlation (delta DCO = 0.93 x delta TCO + 5.4%, r = 0.82, SEE = 17.8%). For CO changes greater than 10%, Doppler was in accordance with thermodilution in 43 of 45 measurements. DCO repeatability coefficient was 0.51 l.min-1. CONCLUSIONS: Compared to thermodilution, continuous-wave Doppler measurements of blood flow velocity across the aortic valve in the transesophageal echocardiographic transgastric view allow accurate CO determination.

Aorta↗
PubMed1988

Control of perioperative hypertension during coronary artery surgery. A randomised double-blind study comparing isosorbide dinitrate and nitroglycerin.

A reduction in the causes of myocardial ischaemia remains of prime importance during coronary artery surgery. Hypertension with the ensuing increase in myocardial oxygen demand is a major factor in the aetiology of perioperative myocardial ischaemia. Nitroglycerin (NTG) has long been used beneficially to reduce myocardial oxygen demand by its effects on the systemic and peripheral vascular resistances. An alternative nitrate, isosorbide dinitrate (ISDN) is now available as an intravenous preparation, and may offer technical advantages, both due to its stability in solution and also its longer in vivo half-life. We designed and carried out a multi-centre study to compare and evaluate the efficacy of ISDN and NTG in the management of perioperative hypertension in 85 patients undergoing elective coronary artery surgery. A total of 288 events in which the systolic blood pressure (SBP) exceeded a predetermined trigger value were observed. ISDN was successful in treating hypertension in 63% of the events, whereas NTG had an 83% success. The SBP was significantly lowered after treatment with either ISDN, 155 mmHg to 138 mmHg, or NTG, 160 mmHg to 130 mmHg. The mean successful dose rate for ISDN was 6.5 micrograms kg-1 min-1, whereas for NTG this was 3.8 micrograms kg-1 min-1. In the ISDN group less events took place possibly due to the longer duration of this drug. In many previous studies NTG has been found to be effective in controlling hypertension; ISDN offers and alternative approach in reducing hypertension.

Coronary Artery Bypass↗
PubMed1987

The normal pericardium does not affect left ventricular function.

Whether the normal pericardium exerts a constraining effect on left ventricular (LV) diastolic compliance and/or systolic function is controversial. Left ventricular filling and performance were studied in 15 patients by two-dimensional transesophageal echocardiography (2D-TEE) measuring end-diastolic area (EDa), end-systolic area (ESa), ejection fraction area (EFa), and hemodynamics immediately pre- and post-pericardiotomy. To diminish the influences of other variables such as surgical stimulation, chest wall constraint, and autoregulation, measurements were performed in deeply anesthetized patients with the chest fully opened immediately before and after pericardiotomy (PC). No significant echocardiographic or hemodynamic changes were observed after PC. Although alterations in compliance cannot be excluded, no significant changes in LV diastolic filling (EDa, pulmonary capillary wedge pressure [PCWP]) or systolic performance (EFa, cardiac output [CO]) were found. Therefore, it is concluded that the normal pericardium does not exert a measurable constraining effect on LV performance.

Coronary Artery Bypass↗
PubMed1986

Validation of quantitative intraoperative transesophageal echocardiography.

Transesophageal echocardiography (TEE) is a new monitoring technique that images the heart and provides information on regional wall motion and left ventricular filling. However, despite its potential for inaccuracy due to its retrocardiac position and angulation, TEE has not been validated by another imaging technique. Using direct on-heart echocardiography (OHE) as a standard, the authors evaluated the ability of TEE to measure accurately left ventricular end-diastolic area (EDa), end-systolic area (ESa), and ejection fraction area (EFa). Ten patients with coronary artery disease without evidence of valvular dysfunction undergoing myocardial revascularization were studied. A Diasonics 3.5 MHz two-dimensional TEE probe was introduced into each patient's esophagus and positioned to obtain a view equivalent to the parasternal short-axis projection. A similar view was obtained by OHE using a sterilely prepared 3 MHz ATL probe placed on either the pericardium or epicardium. In each patient, immediately prior to and after pericardiotomy, both transesophageal and on-heart short-axis views at the level of the papillary muscles were obtained. Using a dedicated Diasonics computer echoanalyzer, EDa and ESa from four consecutive cardiac cycles were outlined with a light pen and averaged. EFa was calculated by the formula EFa = (EDa - ESa)/EDa. Seventeen comparable transesophageal and on-heart echocardiograms were obtained. ESa by TEE correlated well with ESa by OHE (15.13 +/- 9.62 cm2 vs. 14.92 +/- 10.53 cm2; r = 0.94). Similar results were obtained for EDa (27.75 +/- 9.88 cm2 vs. 30.40 +/- 13.99 cm2; r = 0.88) and EFa (0.49 +/- 0.17 vs. 0.54 +/- 0.13; r = 0.92). filling and ejection.

Coronary Disease↗