Biomedical subjects

Wen-Chol Voon

Publications and source records attributed to Wen-Chol Voon.

48 records · Page 3Linked to original sources

PubMed2004

Coronary artery aneurysms in a young patient with acute myocardial infarction: a case report.

Coronary artery aneurysms are not uncommon. They are usually arteriosclerotic in origin, and may be congenital or secondary to injury, dissection, infection, inflammation, or Kawasaki disease (KD). Herein, we report a case involving a 25-year-old male smoker with acute myocardial infarction (AMI). Coronary angiography showed triple-vessel disease, coronary artery aneurysms, and diffuse ectasia. Coronary artery bypass grafting was performed without complications. Based on his history, serologic examinations, and angiographic findings, we suspected that his coronary artery aneurysms and ectasia were the adult sequelae of KD. This case is a good reminder that KD victims may suffer from young-onset AMI.

Adult↗

PubMed2004

A case of subarahnoid hemorrhage with persistent shock and transient ST elevation simulating acute myocardial infarction.

Electrocardiographic changes in neurovascular disease are not rare. Patients with subarachnoid hemorrhage have electrocardiographic (ECG) abnormalities that may mimic ischemic heart disease and acute myocardial infarction. Outflow of catecholamines in the early stage of subarachnoid hemorrhage contributes to elevated blood pressure in most patients. Hypotension is a rare presentation in subarachnoid hemorrhage. We report a case of subarachnoid hemorrhage with transient ST elevation and intractable shock simulating acute myocardial infarction, and review the mechanism of ECG changes in subarachnoid hemorrhage.

Aged↗

PubMed2004

High prevalence of isovolumic relaxation flow in healthy subjects.

BACKGROUND: Inhomogenous left ventricular activation-inactivation has been suggested to play a role in the genesis of segmental early relaxation and in turn of isovolumic relaxation flow (IRF). The spatial distribution of conduction system in the left ventricle leads to heterogenous activation sequence even in healthy subjects. This study was conducted to evaluate our hypothesis that IRF should be ubiquitous in healthy subjects. METHODS: This prospective study included 126 healthy subjects (aged 15-81 years) free of acute or chronic illness by history and physical examination. No significant abnormality appeared in the resting 12-lead electrocardiogram or transthoracic echocardiogram. With the pulsed-wave Doppler echocardiography, the sample volume was placed at the mid-ventricle to detect the IRF. RESULTS: An apically directed IRF, with the velocity 17-101 cm/sec and the duration 57-145 ms, could be detected in all the study subjects. There was no inter-sex difference in such characteristics of IRF. However, its duration and velocity got longer and higher with aging. The fractional shortening of the left ventricle and the interventricular septal thickness were stepwisely selected as the determinants of the IRF velocity, and the transmitral E-to-A wave velocity ratio, the left ventricular inflow propagation velocity, and the interventricular septal thickness as the determinants of the IRF duration. CONCLUSIONS: IRF is ubiquitous in healthy subjects. Both the duration and the velocity of IRF present an aging trend and may be mainly related to left ventricular diastolic and systolic performance, respectively.

Adolescent↗

PubMed2002

Left ventricular inflow propagation velocity: comparisons between pulsed wave and color M-mode Doppler echocardiography.

Sixty-six participants (age 58 +/- 16 years) were included for evaluation of the relationship between color M-mode and pulsed wave Doppler left ventricular inflow propagation velocity (LVIPVcmm and LVIPVpw, respectively). LVIPVpw was measured through the application of the range ambiguity phenomenon, and LVIPVcmm was obtained by manually tracing the first aliasing velocity during the early filling. The variability for LVIPVpw measurements was significantly less than that for LVIPVcmm measurements. There was a significant correlation (r = 0.678, P <.001) between LVIPVcmm and LVIPVpw for all study participants. However, LVIPVpw was greater than LVIPVcmm, especially when the inflow propagation time was relatively short. Age was the only determinant of both LVIPVcmm and LVIPVpw in the control group. As for the patients with diseases retarding inflow propagation, age remained its determinant. However, its impact decreased and the end-systolic dimension and fractional shortening of the left ventricle, instead, turned out to be its major determinant. In conclusion, LVIPVpw measurements are more reproducible than LVIPVcmm measurements. LVIPVpw correlates with LVIPVcmm and their difference significantly correlates with left ventricular inflow propagation time.

Blood Flow Velocity↗

PubMed2002

Differential effects of adenosine on antegrade fast pathway, antegrade slow pathway, and retrograde fast pathway in atrioventricular nodal reentry.

Adenosine has a potent negative dromotropic effect. However, comparative effects of adenosine on the three pathways of atrioventricular (AV) nodal reentry remain unclear. In this study, we sought to determine the effects of adenosine on the antegrade fast, antegrade slow, and retrograde fast pathway conduction in patients with AV nodal reentrant tachycardia (AVNRT). Twenty patients with common slow-fast AVNRT (mean cycle length 360 +/- 49 ms) were studied. The effects of adenosine on the antegrade slow pathway and on the retrograde fast pathway conduction were determined during sustained AVNRT and constant right ventricular pacing at identical cycle lengths (mean 360 +/- 49 ms), respectively. Incremental doses of adenosine were rapidly administered: initial dose of 0.5 mg, followed by stepwise increases of 0.5 or 1.0 mg given at 5-min intervals until termination of AVNRT or second-degree ventriculoatrial block occurred. After the antegrade slow pathway conduction was selectively and completely ablated by radiofrequency catheter ablation, the effect of adenosine on the antegrade fast pathway conduction was evaluated. The dose-response curve of adenosine and the dose of adenosine required to produce AV or ventriculoatrial block among the representative three conduction pathways were compared. The dose-response curve for the effect of adenosine on the antegrade fast pathway lies to the left and upward to that of the effect of adenosine on the antegrade slow pathway which in turn lies to the left and upward to that of the retrograde fast pathway. The mean dose of adenosine required to produce conduction block at antegrade fast, antegrade slow, and retrograde fast pathways were 1.4 +/- 0.5, 4.2 +/- 1.6, and 8.5 +/- 2.6 mg, respectively (p < 0.01). Adenosine has a differential potency to depress antegrade fast, antegrade slow, and retrograde fast pathway conduction in patients with AVNRT. The depressant effect of adenosine on the antegrade fast pathway is more potent than that on the antegrade slow pathway which in turn is more potent than that on the retrograde fast pathway conduction.

Adenosine↗

PubMed2002

Cold effect on qt dispersion in healthy subjects.

Thirty-one healthy subjects, aged 35 +/- 6 (21 to 48) years, were included in the study to evaluate the effect of ice water immersion on QT dispersion. There was no difference in the age between females (n = 11) and males (n = 20). Baseline, stress (at the end of ice water immersion, 4 degrees C, for 3 minutes) and recovery 12-lead electrocardiograms (ECGs) were recorded on each subject. During the test, a significant variability developed in both the QT dispersion (52 +/- 17, 68 +/- 25 and 59 +/- 21 ms; p = 0.015) and the corrected QT dispersion (56 +/- 17, 76 +/- 27 and 64 +/- 23 ms; p = 0.005), but not in the heart rate (74 +/- 11, 76 +/- 9, and 74 +/- 9 bpm, respectively; p = 0.447). There was no inter-sex difference in the baseline heart rate or QT dispersion, or in their response to ice water immersion. Age significantly correlated with the variation of QT dispersion to ice water immersion (r = 0.380, p = 0.035). With 37 years of age as a separation point, the variation of QT dispersion to ice water immersion was more obvious in the older group (28 +/- 22 vs. 10 +/- 19 ms, p = 0.023). In conclusion, cold may increase QT dispersion in healthy subjects, with a more obvious effect in the older ones.

Adult↗

PubMed2002

Changes of coronary risk factors after eradication of Helicobacter pylori infection.

Several epidemiological studies have shown a positive correlation between chronic gastric infection with Helicobacter pylori (HP) and coronary artery disease. A number of reports also claimed that there are strong relationships between HP infection and coronary risk factors. However, clinical studies concerning the changes of coronary risk factors after eradication of HP infection are few and contradictory. We conducted a prospective study aiming to compare sugar, lipid and fibrinolytic profiles before HP eradication with those after HP eradication. HP infection was confirmed by endoscope-based examinations and eradicated by a standard OAC (omeperazole-amoxicillin-clarithromycin) regimen. We measured and compared pre- and post-eradication blood sugar, lipid profiles (total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglyceride) and fibrinolytic profiles (tissue-plasminogen activator, plasminogen activator inhibitor-1, fibrinogen, and D-dimer levels). Forty-eight patients (male:female, 25:23; mean age, 50.8 +/- 11.3 years) with gastric HP infection were enrolled in this study. Although HP infection was confirmed to have been successfully eradicated, no significant changes of blood fasting sugar, lipids or fibrinolytic profiles were found in patients after treatment. Coronary risk factors including fasting sugar, lipid and fibrinolytic profiles were not changed after successful HP eradication treatment. The relationship between HP infection and coronary artery disease needs to be clarified.

Adult↗

PubMed1998

Simple Way to Resolve the Range Ambiguity.

PURPOSE: The purpose of this study was to test the hypothesis that with the range gate fixed, random adjustment of the pulse repetition frequency will offer a rapid and accurate way to avoid misinterpretation of range ambiguity. BACKGROUND: Traditionally, to avoid the misdiagnosis of Doppler artifacts caused by range ambiguity, time must be spent on checking the flow patterns in the calculated phantom range gates. METHODS: Twenty-four patients (mean age 64 +/- 15 years, 15 men and nine women) with mitral regurgitation were included in the study. Pulsed Doppler evaluation was performed with sample volume initially at the shallow left ventricle and then, along the direction of ultrasonic beam, at the calculated range gate distal to the mitral valve to search for the high velocity Doppler signal. The highest velocity scale was initially selected. After detection of high velocity signal, the velocity scale was lowered to achieve the lower pulse repetition frequency. RESULTS: For all patients, a high velocity regurgitant Doppler signal could be recorded both distal to the mitral valve and at the shallow left ventricle. Such signal persisted at the range gate distal to the mitral valve but disappeared at the range gate at the shallow left ventricle after manual adjustment of the velocity scale. The sensitivity, specificity, and accuracy of disappearance of the high velocity Doppler signal after adjustment of the pulse repetition frequency for confirmation of a phantom phenomenon are 100%, 100%, and 100%, respectively. CONCLUSIONS: Without the necessity of exact information about the pulse repetition frequency used, random adjustment of the pulse repetition frequency for the selected gate range is a rapid and exact method for initial differentiation of in situ from phantom signal in pulsed Doppler echocardiography.

Journal Article↗

PubMed1998

Abnormal Inflow Wave Propagation in Patients with Doppler Characteristics of Impaired Left Ventricular Relaxation: Assessment by a Novel Method Through Application of the Range Ambiguity.

With application of the range ambiguity, a delay between the flow onset at both the mitral valve and the apex has been shown to be present in patients with a severely dilated and poorly contracting left ventricle and those with acute myocardial infarction with abnormal apical wall motion, but the delay has been absent in normal subjects. Nevertheless, whether there is a delay between the flow onset at both regions in the presence of impaired left ventricular relaxation remains unknown. This study was undertaken to evaluate the left ventricular inflow wave propagation in control subjects and patients with impaired left ventricular relaxation. Eighteen patients with normal systolic function and Doppler characteristics of impaired relaxation of the left ventricle and 17 age- and sex-matched healthy control subjects were included. Range ambiguity was used to simultaneously record the phantom Doppler signals from the mitral valve region and the true ones from the apex. The inflow wave propagation velocity was derived from the inflow wave propagation distance divided by the time between the mitral valve and the apex. There was always some delay between the flow onset at both the mitral valve and the apex in both the controls and the patients (47 +/- 13 msec vs 85 +/- 19 msec, P < 0.001). The inflow wave propagation velocity was 160 +/- 50 cm/sec and 90 +/- 20 cm/sec in the control subjects and the patients, respectively (P < 0.001). Multiple linear regression analyses of the significantly correlated variables stepwisely selected the deceleration time of the E wave (R(2) = 0.53, P < 0.001) and age (R(2) = 0.06, P = 0.039) as the significant determinants of the left ventricular inflow wave propagation velocity. In conclusion, the application of the range ambiguity offers a new method of determining the left ventricular inflow wave propagation velocity, and Doppler characteristics of impaired left ventricular relaxation are associated with a slower inflow wave propagation from the mitral valve to the apex.

Journal Article↗

PubMed1997

Doppler Study of Transmitted Transmitral A Wave in Patients with a Fourth Heart Sound.

To investigate the characters of the transmitted transmitral A wave associated with a fourth heart sound, left ventricular inflow, and outflow Doppler echocardiography and phonocardiography were recorded in 13 patients with a fourth heart sound and 9 age-matched control subjects. The Doppler echocardiographic data were compared between both groups and the peak velocity and acceleration rate of the transmitted transmitral A wave were correlated with other parameters. The peak velocity and acceleration rate of the transmitted transmitral A wave were significantly greater, but the A wave transit time from the mitral valve to the left ventricular outflow tract (A-Ar interval) was significantly shorter in patients with a fourth heart sound. There was a significant correlation between the A-Ar interval and the peak velocity (r = -0.54, P = 0.01) or acceleration rate (r = -0.63, P = 0.002) of the transmitted transmitral A wave. The A-Ar interval was shown to be the independent determinant of both the peak velocity and acceleration rate of the transmitted transmitral A wave by stepwise multiple linear regression. In conclusion, the presence of a fourth heart sound was associated with a higher peak velocity and acceleration rate of the transmitted transmitral A wave, to which increased ventricular stiffness may make some contributions.

Journal Article↗

PubMed1997

Doppler Evaluation of Left Ventricular Diastolic Inflow and Outflow Waveforms in Normal Subjects.

The measurements of the left ventricular inflow parameters do not necessarily reflect the measurements of the respective outflow ones. The A wave transit time from the mitral valve to the left ventricular outflow tract has been demonstrated to have a fair correlation with measures of the left ventricular late diastolic stiffness. We performed this study to obtain the normal patterns of the diastolic left ventricular outflow as well as inflow waveforms and to evaluate the roles of aging and other physiological parameters in their evolution. The study population consisted of 60 healthy subjects (aged 22-66 years). They were divided into three groups: group 1 (aged 20-34 years), group 2 (aged 35-49 years), and group 3 (aged 50-70 years). Pulse-wave Doppler echocardiography was performed to get the patterns of diastolic left ventricular inflow and outflow waveforms. With aging, the peak velocity and velocity-time integral of the transmitted transmitral E wave decreased, and those of the transmitted transmitral A wave increased with a progressive decrease in their ratio of transmitted transmitral E to A wave. The diastolic left ventricular inflows followed a similar aging course. There was no obvious aging trend in the A wave transit time from the mitral valve to the left ventricular outflow tract. Multiple linear regression analyses selected age as the most important determinant in the differences in most left ventricular inflow and outflow indices among normal subjects. Besides, heart rate had modest influences on some Doppler indices. This study confirms the age related changes in the left ventricular inflow waveforms and further establishes the concept that the diastolic left ventricular outflow waveforms are also significantly influenced by age and heart rate. Hence, both factors should be taken into account in interpreting the diastolic left ventricular outflow as well as inflow indices.

Journal Article↗

PubMedDate not supplied

Q-wave regression after acute myocardial infarction assessed by Tl-201 myocardial perfusion SPECT.

BACKGROUND: The actual relationship between the interval change of myocardial thallium 201 (Tl-201) radioactivity in the infarct area and the pattern of Q-wave regression is still unknown. This study was conducted to evaluate their relationship after acute myocardial infarction (AMI). METHODS AND RESULTS: A total of 30 patients who had a first Q-wave AMI (11 without Q-wave regression and 19 with Q-wave regression) were retrospectively included. Two sets of 12-lead surface electrocardiograms and Tl-201 myocardial perfusion images were obtained 0 to 2 months and 14 to 84 months after the AMI event, respectively. The acute/subacute redistribution Tl-201 radioactivity was similar between the patients with and those without Q-wave regression. However, the patients with Q-wave regression had higher chronic redistribution Tl-201 radioactivity than those without Q-wave regression. Moreover, the patients with Q-wave regression presented a higher gradient in the redistribution Tl-201 radioactivity between the chronic and acute/subacute images than those without Q-wave regression. CONCLUSIONS: This study supports the role of functional recovery of stunning and/or hibernating myocardium in the disappearance of Q waves after AMI.

Coronary Vessels↗