Biomedical subjects

Chi-Ming Chow

Publications and source records attributed to Chi-Ming Chow.

3 recordsLinked to original sources

PubMed2003

Interatrial septal mobility predicts larger shunts across patent foramen ovales: an analysis with transmitral Doppler scanning.

BACKGROUND: The association of patent foramen ovale (PFO) with cryptogenic stroke is strongest in patients with larger shunts and patients with atrial septal aneurysms (ASAs). We postulated that the potency of ASA as a risk factor for stroke relates to the size of shunt across PFOs associated with mobile atrial septae. The purpose of this study was to investigate the relationship between atrial septal mobility and the degree of right-to-left shunting with a transthoracic transmitral Doppler scanning (TMD) contrast technique. METHODS: In 165 consecutive patients, transthoracic TMD recordings were made during a saline contrast study with the patient at rest and after a maneuver to increase right atrial pressure. Bubble transit corresponded to high intensity signals in the velocity envelope of the mitral inflow profile and was quantified by a bubble score. RESULTS: A PFO was diagnosed in 59 patients (36%). In 50 patients with PFO and adequate echocardiography images, the incidence of ASA was 52%. In this group, both total septal mobility and leftward deviation predicted the TMD bubble score at rest (Spearman rho 0.64, 0.64, respectively, P <.001) and after the maneuver (Spearman rho 0.74, 0.73, P <.001). In 28 patients with cerebral ischemic events, the maneuver bubble score was predictive for cryptogenic stroke (P =.02, odds ratio 7.58). There was a trend toward significance between total septal motion and cryptogenic stroke (P =.06). CONCLUSION: Atrial septal mobility predicts the degree of right-to-left shunts across PFOs. The role of excessive septal mobility in the etiology of stroke may therefore be caused by the greater opportunity for paradoxical embolism because of the size of the associated trans-PFO shunt.

Adult↗

PubMed2002

Pulse inversion harmonic imaging improves endocardial border visualization in two-dimensional images: comparison with harmonic imaging.

Pulse inversion harmonic imaging (PIHI) is a new modality that increases the detection of harmonic echoes and myocardial contrast by cancelling linearly transmitted signals. We tested whether PIHI improved the detection of endocardial borders in noncontrast 2-dimensional echocardiography. We compared PIHI with tissue harmonic imaging (THI), which decreases linearly transmitted signals using filters. Fundamental mode (FM) was compared with THI and PIHI in 50 consecutive patients. The global and segmental endocardial visualization scores measured with FM were significantly improved by using either THI or PIHI. The improvement of the global score compared with FM was slightly higher using PIHI than THI, because of an improved visualization of the base and the anterior wall with the PIHI technique compared with THI. The ratio of myocardial-to-cavity signal was similarly increased from FM with THI and PIHI. PIHI, a new modality for detection of myocardial contrast, can also be used for endocardial border visualization. It provides an improvement relative to THI for specific regions of the endocardium.

Echocardiography↗

PubMed2002

Effect of destructive pulse duration on the detection of myocardial perfusion in myocardial contrast echocardiography: In vitro and in vivo observations.

UNLABELLED: Myocardial perfusion is detected with contrast echocardiography by comparing a contrast-enhanced image with a baseline obtained before contrast injection (true baseline) or after myocardial bubble destruction after a high-power destructive pulse (postdestructive pulse baseline). Although it is assumed that all bubbles are destroyed by a destructive pulse insuring optimal contrast detection, this assumption has not been tested. In 18 participants we compared the videointensity (VI) differences among the contrast-enhanced image, the postdestructive pulse baseline, and the true baseline using both triggered high-mechanical index imaging and real-time imaging. VI difference was significantly greater for the true baseline with both techniques at all ventricular levels. The benefit of using a true baseline was less when the duration of the destructive pulse was increased. Similarly, we quantified VI in a flow phantom using continuous Optison (commercially available perfluoropropane-filled albumin microbubbles) (Amersham, Princeton, NJ) infusion and variable durations of destructive pulses. VI decreased with the duration of the destructive pulse and reached a plateau after a duration of 8 to 15 frames. The plateau reached after a long destructive pulse was dependent on flow rate and concentration and never reached a true baseline, unless concentration (<100 microL/L) and flow rate (<0.5 cm/s) were very low. IN CONCLUSION: (1) in clinical studies, the difference in VI between contrast-enhanced and baseline images is greater when true baseline is used; (2) the longer the destructive pulse, the closer the postdestructive pulse baseline to true baseline; and (3) this effect exists in all regions of the left ventricle.

Adult↗