Search PubMed⌕ Search

Biomedical subjects

T L Hsu

Publications and source records attributed to T L Hsu.

At least 55 records · Page 3Linked to original sources
PubMed1994

Intravascular ultrasound imaging in acute aortic dissection.

OBJECTIVES: This study was performed to determine the potential of intravascular ultrasound in the detection and delineation of aortic dissection. BACKGROUND: Intravascular ultrasound is a new technique capable of displaying real-time cross-sectional images of arterial vasculature. Its clinical use has been explored mostly in coronary and peripheral arterial circulation. METHODS: Intravascular ultrasound imaging of the aorta was performed using a 20-MHz ultrasound catheter in 28 patients with suspected aortic dissection. All patients underwent contrast angiography; 7 had computed tomography; and 22 had transesophageal echocardiography. RESULTS: Imaging of the aorta from the root level to its bifurcation was performed in all patients in an average of 10 min. No complications occurred. Dissection was present in 23 patients and absent in 5. In the patients without dissection, intravascular ultrasound revealed normal aortic anatomy. In all 23 patients with dissection, intravascular ultrasound demonstrated the intimal flap and true and false lumena. The longitudinal and circumferential extent of aortic dissection, contents of the false lumen, involvement of branch vessels and the presence of intramural hematoma in the aortic wall could also be identified. In cases where aortography could not define the distal extent of the dissection, intravascular ultrasound did. CONCLUSIONS: Our experience in this series of patients with aortic dissection indicates that intravascular ultrasound could be valuable in the identification and categorization of aortic dissection and in the description of associated pathologic changes that may be clinically important. It can be performed rapidly and safely and could serve as an alternative or adjunct diagnostic procedure in patients with aortic dissection.

Acute Disease↗
PubMed1994

Alteration of pulse in human subjects by three Chinese herbs.

Human subjects were fed with extract of three Chinese herbs, Panax ginseng, Panax quinquefolium roots and Ganoderma lucidum. Pulse of the radial artery was examined. Our results indicate that each herb has a specific effect on the Fourier components of the pulse, and is in agreement with traditional Chinese medical descriptions.

Adolescent↗
PubMed1994

Three-dimensional volumetric ultrasound imaging of arterial pathology from two-dimensional intravascular ultrasound: an in vitro study.

The objectives of this study were to evaluate: (1) the feasibility of generating three-dimensional (3-D) ultrasound (US) volumetric images of arterial segments from intravascular (IV) US images by retaining full range of gray levels; (2) the feasibility of volumetric quantitation of various arterial wall pathology from the 3-D volume US images of arterial segments. IVUS provides morphologic details of arterial wall diseases. This is seen as variation in gray levels. However, when a 3-D US image is generated currently, the full range of gray levels is not utilized. This limits optimal assessment of arterial wall pathology. Sequential cross-sectional IVUS images from 11 arterial segments consisting of various pathology were obtained in vitro by calibrated withdrawal of an IVUS catheter. These images were digitized by an 8 bit digitizer to retain full 256 gray levels of brightness. 3-D volume generation was carried out using "ANALYZE" software. After the IVUS imaging, arterial segments were sectioned transversely in a 0.3-0.4 mm cross section and stained with hematoxylin, eosin and elastin. Geometrical measurements and gross morphological changes of the arterial segments were noted and correlated with the corresponding section of the image from the three-dimensional volume. Arterial wall pathology, its extent and its effect on lumen geometry were easily appreciated in multiple tomographic sections of a 3-D volume image. Similarly, arterial wall pathology was easily quantitated from 3-D volume. The above assessments were only feasible by retaining full range of gray levels in the 3-D volume image. This study indicates that (1) it is feasible to generate a 3-D US volume image by retaining full range of gray levels from IVUS images, (2) retaining full range of gray levels allows optimal assessment of arterial wall pathology and its extent in 3-D volume, and (3) IVUS allows quantitation of arterial wall pathology, and thereby one can assess the effect of intervention.

Arteries↗
PubMed1993

Left ventricular diastolic collapse in regional left heart cardiac tamponade. An experimental echocardiographic and hemodynamic study.

OBJECTIVES: This study was designed to describe the hemodynamic abnormalities associated with the appearance of left ventricular diastolic collapse in the setting of regional left heart cardiac tamponade. BACKGROUND: Cardiac tamponade after heart surgery is frequently associated with localized pericardial effusion. Although right ventricular diastolic collapse and right atrial collapse are reliable echocardiographic findings in patients with circumferential pericardial effusion and tamponade, they are often not present in postoperative patients with localized pericardial effusion and regional left heart tamponade. Left ventricular diastolic collapse has been described in such patients, but the degree of hemodynamic alteration that exists with this finding is not known. METHODS: Acute regional left heart tamponade was produced 14 times in seven spontaneously breathing anesthetized dogs by infusing fluid into an isolated compartment created in the pericardial space adjacent to the left ventricular free wall. Continuous echocardiographic imaging and hemodynamic monitoring of left ventricular, systemic arterial, right atrial, pulmonary capillary wedge and pericardial pressures were performed. Measurements at baseline were compared with those made at the onset of left ventricular diastolic collapse and at decompensated tamponade. RESULTS: Left ventricular diastolic collapse was noted in all 14 episodes of regional tamponade. It occurred when pressure in the left pericardial compartment exceeded left ventricular diastolic pressure by 3.0 +/- 1.9 mm Hg. At the onset of left ventricular diastolic collapse, cardiac output and mean arterial pressure were significantly reduced from the control value (p < 0.05). Systolic hypotension was noted only twice at this stage, respiratory variation in systolic pressure > 10 mm Hg only once. The appearance of this sign was also associated with elevated left heart filling pressures. CONCLUSIONS: Left ventricular diastolic collapse is a reliable sign of regional left ventricular tamponade and is associated with a reduction in cardiac output. This echocardiographic finding usually occurs before the development of arterial hypotension and pulsus paradoxus. Thus, left ventricular diastolic collapse is potentially more reliable than hypotension or pulsus paradoxus in the diagnosis of regional left ventricular tamponade.

Acute Disease↗
PubMed1993

Intracardiac echocardiography in humans using a small-sized (6F), low frequency (12.5 MHz) ultrasound catheter. Methods, imaging planes and clinical experience.

OBJECTIVES: This study was designed to determine the clinical utility and feasibility of using 12.5-MHz ultrasound catheters for intracardiac echocardiography. BACKGROUND: Intracardiac echocardiography is a potentially useful technique of cardiac imaging and monitoring in certain settings. The feasibility of intracardiac echocardiography using 20-MHz ultrasound catheters in patients has been demonstrated. High resolution images of normal cardiac structures as well as cardiac abnormalities have been obtained. However, imaging has been limited by the shallow depth of field inherent in high frequency ultrasound imaging. METHODS: Intracardiac echocardiography with 12.5-MHz catheters was performed in eight mongrel dogs and 92 patients. Catheters were introduced percutaneously in 80 patients studied in the catheterization laboratory and directly into the heart in 12 patients in the operating room. Right heart imaging was performed in 68 patients and arterial and left heart imaging in 35 patients. RESULTS: When these catheters were introduced into the venous system, the right atrium, tricuspid valve, right ventricle, pulmonary valve and pulmonary artery were visualized. Pericardial effusion, intracardiac masses and atrial septal defects were correctly identified. The left ventricle, left atrium, mitral valve, aortic valve, aorta and coronary arteries could be imaged from the arterial circulation. Diseases identified included valvular aortic stenosis, subvalvular aortic stenosis and Kawasaki disease. Average imaging time was 10 min. No complications occurred as a result of intracardiac echocardiography. CONCLUSIONS: Intracardiac echocardiography with 12.5-MHz ultrasound catheters is safe and feasible; it also provides anatomic and physiologic information. This feasibility study provides a foundation for wider clinical use of intracardic echocardiography.

Adolescent↗
PubMed1993

[Intravenous midazolam for sedation in epidural anesthesia].

30 cases receiving epidural anesthesia for lower extremities and abdominal surgery were selected in this study. Their physical status and average age were ASA I or II and 41 +/- 10.0 years old. Premedication included intramuscular injection of pethidine, atropine and promethazine. Epidural anesthesia was accomplished with 15 ml 2% lidocaine with epinephrine (1:80,000). After the stabilization of vital signs, the patients were put asleep by 0.1 mg/kg of midazolam intravenously. They were then evaluated by the sedative, cardiovascular, respiratory and recovery effects of intravenous midazolam in epidural anesthesia. The results were as follows: The patients receiving IV midazolam averagely fell asleep in 61.6 +/- 20.5 seconds and maintained asleep for 55.4 +/- 12.7 minutes. Pain on injection was not noted in these cases. Cardiovascular parameters revealed midazolam with general depression on systolic pressure (17.4 +/- 7.3%), diastolic pressure (13.4 +/- 8.4%), mean arterial pressure (12.7 +/- 7.0%), heart rate (10.9 +/- 7.2%), stroke volume (13.7 +/- 8.9%) and cardiac output (18.4 +/- 7.0%) respectively. The peak depression reached around 10 minutes after drug administration. Respiratory parameters dropped with SaO2 (1.1 +/- 1.6%) and respiratory rate (9.7 +/- 5.7%) and fell into trough after 5 minutes of drug administration. Although all the above parameters measured were statistically significant, they were of no clinical importance that required further management. No case had delirium, anxiety and vomiting in the recovery period. Conclusively, patients receiving epidural anesthesia with supplement of intravenous midazolam provides a good sedative effect. Clinically, there was less severe untowards reaction either in cardiovascular or respiratory systems. Smooth and stable recovery was also noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Single, biplane, multiplane, and three-dimensional transesophageal echocardiography. Echocardiographic-anatomic correlations.

Advances in TEE instrumentation have led to the emergence of this modality as a powerful diagnostic tool. Numerous investigations in humans have clearly defined the plethora of clinical applications of TEE in a variety of patient care scenarios. Research in progress in the area of transducer technology and computerized image processing is likely to bring 3-D TEE to the clinical front.

Aorta, Thoracic↗
PubMed1993

Mitral regurgitation after double balloon or Inoue balloon mitral valvuloplasty.

We performed serial color Doppler echocardiographic studies prospectively before and after double balloon or Inoue balloon mitral valvuloplasty in 44 patients (mean age 45 +/- 13, range 20-74) with pure rheumatic mitral stenosis (by angiography) selected in a case-control manner to compare the incidence and severity of mitral regurgitation. After balloon dilation, mitral valve area increased from 0.9 +/- 0.2 to 1.5 +/- 0.4 cm2 (p < 0.001) in the double balloon group and from 0.9 +/- 0.3 to 1.5 +/- 0.3 cm2 (p < 0.001) in the Inoue balloon group. Twenty-four hours after balloon dilation, 3 patients in the double balloon group and 12 patients in the Inoue balloon group developed moderate to severe mitral regurgitation (p < 0.05). The severity of mitral regurgitation tended to persist or progress during follow-up in both groups, although improvement could also be observed. Two patients with severe mitral regurgitation in the Inoue balloon group underwent mitral valve replacement during follow-up. In conclusion, double balloon and Inoue balloon techniques are both effective in relieving significant mitral stenosis. However, Inoue balloon technique may be associated with slightly higher frequency of mitral regurgitation.

Adult↗
PubMed1992

Intravascular ultrasound and intracardiac echocardiography: concepts for the future.

Intravascular ultrasound imaging is a catheter-based method that has been shown to be better than contrast angiography in the detailed assessment of coronary and peripheral arterial atherosclerotic lesions, arterial dissections and clots, aortic and pulmonary arterial disorders, and the effects and complications of interventional therapy in various vascular beds. Evaluation of refined ultrasound catheters, combined imaging and therapeutic devices, and off-line 3-dimensional reconstruction capabilities indicates that intravascular ultrasound could provide guidance during various catheter-based therapeutic procedures. Early experience with intracardiac echocardiography suggests that this technique could evolve as a clinically useful method with diagnostic, monitoring, and guidance applications. Future directions for further development include designing of miniaturized imaging devices, "look-forward" imaging devices, low frequency devices for whole heart imaging, multifrequency ultrasound catheters and multifunction ultrasound consoles, and approaches to real-time 3-dimensional imaging, on-line tissue characterization, automated acoustic quantification and tissue characterization, the study of myocardial perfusion, and catheter-based acoustic myocardial biopsy. These developments could lead to the conversion of catheterization laboratories into integrated imaging, monitoring, and therapeutic stations. In addition, continuous monitoring of cardiac function could be possible in the critical care unit and in the operating room as well. Ongoing advances in catheter technology and image processing indicate that these concepts are within the realm of becoming reality.

Arteries↗
PubMed1992

The value of transesophageal echocardiography in the diagnosis of cardiac metastasis.

To assess the diagnostic value of transesophageal two-dimensional echocardiography (TEE) as compared with transthoracic echocardiography (TTE), TTE and TEE were performed in eight consecutive patients (age range from 20 to 76 years, six male and two female) with clinical evidence of malignant tumors arising from the liver (n = 1), lung (n = 3), larynx (n = 1), osteogenic sarcoma (n = 1), lymphoma (n = 1), and yolk sac tumor in the anterior mediastinum (n = 1). In one case, the gastroscope could not be inserted because of tumor compression of the esophagus. Transesophageal echocardiography provided superior imaging in the detection of intracavitary metastatic lesions. In the case of right ventricular outflow tract tumor and greater vessel involvement, TTE may provide more imaging than TEE due to a blind area in this region by the transesophageal approach. In conclusion, TEE is complementary to TTE in the diagnosis of metastatic cardiac tumor.

Adult↗
PubMed1992

Usefulness of transesophageal echocardiography for the detection of left atrial thrombi in patients with rheumatic heart disease.

Transesophageal (TEE) and transthoracic (TTE) echocardiograms were performed in 110 patients with rheumatic heart disease to evaluate the usefulness of these methods for the detection of left atrial thrombi. TEE was better than TTE for detecting left atrial thrombi (21 vs 9). The thrombi not detected by TTE were in the left atrial appendage in ten and over the left atrial posterior wall in two. Patients with left atrial thrombi had significantly smaller mitral valve area (P less than 0.01) and greater left atrial dimension (P less than 0.05) than those without. All patients with left atrial thrombi had atrial fibrillation. Thirty-one patients underwent surgical intervention and 13 were found to have left atrial thrombi. TEE detected left atrial thrombi in all 13 patients with a sensitivity of 100%, specificity of 100%, and accuracy of 100%, while TTE detected left atrial thrombi in only nine of these 13 patients with a sensitivity of 69.2%, specificity of 100%, and accuracy of 87.1%. Thus, TEE is superior to TTE for the detection of left atrial thrombi, especially for those thrombi located in the left atrial appendage and along the left atrial posterior wall.

Adult↗
PubMed1992

Multiplane transesophageal echocardiography. Imaging planes, echocardiographic anatomy, and clinical experience with a prototype phased array OmniPlane probe.

Multiplane transesophageal echocardiography is a new exciting development in echocardiography. We examined the methodology and echo-anatomic correlations of multiplane transesophageal echocardiography and its clinical applications in 100 patients. We used a 5-MHz phased array multiplane (OmniPlane) transesophageal probe. In this instrument, the transducer array can be steered through 180 degrees from any transducer location. This provides a vast assembly of imaging planes, allowing for detailed visualization of all dimensions of cardiac anatomy. This report presents our observations on the echocardiographic anatomy seen in various image planes and the unique clinical potential of multiplane transesophageal echocardiography in the diagnostic assessment of cardiovascular disorders. This technique appears to provide incremental diagnostic information that enhances the interpretative ability. Less esophageal probe manipulation is required with consequent decrease in patient discomfort. We conclude that multiplane transesophageal echocardiography enhances the versatility of transesophageal examination and offers many new avenues for developments such as three-dimensional echocardiography.

Echocardiography↗
PubMed1992

Three-dimensional and four-dimensional transesophageal echocardiographic imaging of the heart and aorta in humans using a computed tomographic imaging probe.

We evaluated the clinical applicability of a prototype tomographic transesophageal echocardiographic (TEE) system, which not only provides conventional TEE images but also three-dimensional tissue reconstruction and four-dimensional display capabilities. The probe was used in 16 patients in the echocardiographic laboratory, intensive care unit, and the operating room. The instrument is a 5-MHz, 64-element, phased array unit mounted on a sliding carriage within a casing. After appropriate probe placement within the esophagus, the probe is straightened, a balloon surrounding the probe is inflated, and data acquisition begun with ECG and respiration gating. With computer controlled transducer movement at 1-mm increments, a complete cardiac cycle is recorded at each tomographic level. These are processed using a dedicated four-dimensional software, and displayed as a dynamic three-dimensional tissue image of the heart. We were able to see the dynamic motion of the ventricles and all the valves in the four-dimensional format. In addition to four-dimensional display, we were able to cut and visualize the heart in dynamic mode in any desired plane and also in multiple planes. Patients tolerated the procedure well. We conclude that this tomographic four-dimensional approach, which does not require tedious off-line processing, can easily be performed in patients and has a strong clinical potential.

Aorta↗
PubMed1992

Response of left ventricular ejection performance following balloon valvuloplasty in patients with mitral stenosis.

In order to see if any change of left ventricular ejection performance (LEVP) would occur after successful balloon mitral valvuloplasty (BMV), a prospective study on echocardiography and calibrated carotid pulse tractings was performed two days before, two days and then six months after BMV in 24 patients with pure rheumatic mitral stenosis (MS). Echocardiographic parameters representing preload i.e. end-diastolic volume index (EDVI); afterload i.e. end-systolic wall stress (ESS), and the indices of LVEP i.e. ejection fraction (EF), fractional shortening, rate-corrected velocity of circumferential shortening (VCFc) and a ratio of ESS over end-systolic volume index (ESS/ESVI) were measured. A group of 66 normal subjects was used to establish the 95% confidence interval of the echo parameters. The incidence of depressed LVEP in MS patients was about 21% when measured by load-independent index i.e. ESS/ESVI. In the MS group, 7 out 24 (29%) patients achieved an increased cardiac index after BMV. Six (25%) MS patients showed an EF below 95% confidence interval of control (less than 55%) before BMV and, of these 6, only 3 patients increased their EDVI after the BMV. Those who showed an EF greater than or equal to 55% before BMV gave no change in their preload (EDVI) after the BMV. Only one MS patient showed high afterload (ESS) both before and after BMV. However, the ESS/ESVI showed insignificant improvement (p = 0.055) after BMV. It was therefore concluded that (1) a depressed LVEP is frequently seen in patients with MS; (2) LVEP can be improved by BMV in some (21%) patients with MS, and the improvement is not related to the change of preload or afterload but more likely secondary to an increased myocardial contractility.

Adult↗
PubMed1991

Frequency and severity of mitral regurgitation one year after balloon mitral valvuloplasty.

Mitral regurgitation (MR) was evaluated by Doppler echocardiography in 59 patients with mitral stenosis before, immediately after and 1 year after balloon mitral valvuloplasty (BMV). The severity of MR was graded on a scale from 1+ to 4+. Echocardiographic and hemodynamic variables were analyzed to study the potential factor(s) that might predict the long-term persistence of MR. Echocardiographic variables were mitral valve thickness and motion, subvalvular change, left atrial dimension, commissural calcification and effective balloon/mitral anular diameters. Hemodynamic variables were mitral pressure gradient, pulmonary arterial pressure, ejection fraction, mitral valve area index, age, gender and cardiac rhythm. Mitral valve area index increased from 0.9 +/- 0.5 to 1.5 +/- 0.8 cm2/m2 immediately after BMW, and to 1.4 +/- 0.3 cm2/m2 at 1 year follow-up (p less than 0.01). Immediately after BMV, MR grading did not change in 30 patients (51%), increased by 1+ in 23 patients (39%), by 2+ in 2 patients (3.3%) and by 3+ in 2 patients (3.3%), and decreased by 1+ in 2 others. At 1-year follow-up, only 1 patient with severe MR required valve replacement. Fifty-one patients (88%) had no change in the extent of MR (less than or equal to 1+) and 6 patients (10%) had a 1-grade decrease in their MR; only 1 patient had a 1-grade increase in MR. No clinical or hemodynamic variables or morphologic characteristics of the mitral valve could predict the development of significant MR after BMV. It is concluded that an increment in MR severity less than or equal to 2+ is frequently seen after BMV.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Intracardiac echocardiography: current developments.

Intracardiac echocardiography refers to the method of imaging cardiac structures from intracardiac locations with the use of ultrasound catheters. Advances in catheter-based interventional cardiologic procedures to treat cardiovascular lesions and the problems encountered during those procedures due to inadequate guidance provided by fluoroscopy have given the impetus to develop other guidance modalities. Experimental explorations with intracardiac ultrasound probes have indicated that detailed visualization of cardiac structures in real-time is possible by intracardiac ultrasound. Recent advances in catheter-based ultrasound technology make it feasible to safely pass small-sized catheters in humans into various intracardiac locations and acquire images of valvular structures and various chambers. Experience with 20 MHz ultrasound catheters indicates that high resolution images of normal and abnormal structures can be obtained if the catheter is manipulated close to the region of interest. The problem of the limited depth of field associated with 20 MHz catheters has led to the fabrication of catheters with lower frequency ultrasound elements. Experimental and clinical experience with 12.5 MHz ultrasound catheters points to the capability and potential of intracardiac echocardiography to not only display normal structures but also aid in the identification of valvular abnormalities, chamber dysfunction and pericardial effusions. In addition, aortic disorders such as acute dissection, coarctation and atherosclerotic disease could be delineated. Similarly, abnormalities involving the pulmonary arteries such as pulmonary embolism, organized thrombi, peripheral pulmonary arterial stenoses, and pulmonary hypertension-induced vascular changes could be recognized. Many modifications in the catheter design are being explored. With further work in the area of catheter technology and ultrasound image processing, intracardiac echocardiography is likely to become a clinical tool.

Animals↗
PubMed1991

Transesophageal color Doppler flow mapping of iatrogenic left-to-right interatrial shunting after percutaneous transluminal mitral valvotomy.

Characteristics of transesophageal color Doppler flow mapping of iatrogenic left-to-right interatrial shunts were assessed in 58 patients, 1 to 994 days after percutaneous transluminal mitral valvotomy. Transesophageal color Doppler flow mapping detected 22 cases of interatrial shunt whereas transthoracic two-dimensional echocardiography visualized only five interatrial septal defects. Five types of color Doppler flow patterns of interatrial shunts were found: type 1, a bluish jet passing through the interatrial septum into the right atrium with a small bluish proximal flow in the left atrium (50%); type 2, a bluish jet passing through the interatrial septum into the right atrium without a proximal flow (13.6%); type 3, a predominant bluish proximal flow in the left atrium passing through the interatrial septum with minimal flow entering into the right atrium (18.2%); type 4, an "en face" bluish jet in the right atrium (4.5%); and type 5, a "wall jet" with proximal flow adhering to and entering into the interatrial septum (13.6%). Oximetry demonstrated increased pulmonary-to-systemic flow ratio (range 1.07 to 3.32) in 11 patients (50%), which was significantly correlated with the maximal jet area derived from color Doppler flow mapping (r = 0.80, P = 0.001). Thus, transesophageal color Doppler flow mapping is useful in detection of left-to-right interatrial shunts after percutaneous transluminal mitral valvotomy, and recognition of the variable types of color flow mapping may further help identify these atypical interatrial shunts.

Adult↗