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Kwan-Leung Chan

Publications and source records attributed to Kwan-Leung Chan.

12 recordsLinked to original sources
PubMed2006

Impact of blood pressure on the Doppler echocardiographic assessment of severity of aortic stenosis.

OBJECTIVE: To investigate the impact of blood pressure (BP) on the Doppler echocardiographic (Doppler-echo) evaluation of severity of aortic stenosis (AS). METHODS: Handgrip exercise or phenylephrine infusion was used to increase BP in 22 patients with AS. Indices of AS severity (mean pressure gradient (DeltaP(mean)), aortic valve area (AVA), valve resistance, percentage left ventricular stroke work loss (% LVSW loss) and the energy loss coefficient (ELCo)) were measured at baseline, peak BP intervention and recovery. RESULTS: From baseline to peak intervention, mean (SD) BP increased (99 (8) vs 121 (10) mm Hg, p<0.001), systemic vascular resistance (SVR) increased (1294 (264) vs 1552 (372) dynexs/cm(5), p<0.001) and mean (SD) transvalvular flow rate (Q(mean)) decreased (323 (67) vs 306 (66) ml/s, p = 0.02). There was no change in DeltaP(mean) (36 (13) vs 36 (14) mm Hg, p = NS). However, there was a decrease in AVA (1.15 (0.32) vs 1.09 (0.33) cm(2), p = 0.02) and ELCo (1.32 (0.40) vs 1.24 (0.42) cm(2), p = 0.04), and an increase in valve resistance (153 (63) vs 164 (74) dynexs/cm(5), p = 0.02), suggesting a more severe valve stenosis. In contrast, % LVSW loss decreased (19.8 (6) vs 16.5 (6)%, p<0.001), suggesting a less severe valve stenosis. There was an inverse relationship between the change in mean BP and AVA (r = -0.34, p = 0.02); however, only the change in Q(mean) was an independent predictor of the change in AVA (r = 0.81, p<0.001). CONCLUSIONS: Acute BP elevation due to increased SVR can affect the Doppler-echo evaluation of AS severity. However, the impact of BP on the assessment of AS severity depends primarily on the associated change in Q(mean), rather than on an independent effect of SVR or arterial compliance, and can result in a valve appearing either more or less stenotic depending on the direction and magnitude of the change in Q(mean).

Aged↗
PubMed2005

Angiotensin receptor blockade and exercise capacity in adults with systemic right ventricles: a multicenter, randomized, placebo-controlled clinical trial.

BACKGROUND: Pharmacological blockade of the renin-angiotensin system improves exercise tolerance in patients with left ventricular dysfunction, yet its impact on patients with systemic right ventricles (RVs) remains unknown. METHODS AND RESULTS: A multicenter, randomized, double-blind, placebo-controlled, crossover clinical trial was performed to assess the effects of losartan on exercise capacity and neurohormonal levels in patients with systemic RVs. Of 29 patients studied (age, 30.3+/-10.9 years), 21 had transposition of the great arteries with a Mustard baffle, and 8 had congenitally corrected transposition of the great arteries. Baseline values were as follows: VO2max, 29.8+/-5.6 mL.kg(-1).min(-1) (73.5+/-12.9% predicted value); RV ejection fraction, 41.6+/-9.3%; N-terminal pro brain natriuretic peptide (NT-proBNP), 257.7+/-243.4 pg/mL (normal <125 pg/mL); and angiotensin II, 5.7+/-4.9 pg/mL (normal <5.0 pg/mL). Comparing losartan to placebo showed no differences in VO2max (29.9+/-5.4 versus 29.4+/-6.2 mL.kg(-1).min(-1); P=0.43), exercise duration (632.3+/-123.0 versus 629.9+/-140.7 seconds; P=0.76), and NT-proBNP levels (201.2+/-267.8 versus 229.7+/-291.5 pg/mL; P=0.10), despite a trend toward increased angiotensin II levels (15.2+/-13.8 versus 8.8+/-12.5 pg/mL; P=0.08). CONCLUSIONS: In adults with systemic RVs, losartan did not improve exercise capacity or reduce NT-proBNP levels. Minimal baseline activation of the renin-angiotensin system may explain this lack of benefit and imply an alternative pathophysiological mechanism for the progressive ventricular dysfunction and impaired exercise capacity observed in such patients.

Adult↗
PubMed2004

Comparison of real-time 3-dimensional echocardiography with conventional 2-dimensional echocardiography in the assessment of structural heart disease.

We evaluated the diagnostic use of a real-time 3-dimensional (3D) echocardiographic system in 106 patients referred for echocardiography during a 4-month period. Real-time 3D echocardiography was performed and recorded in parallel with a routine, comprehensive 2-dimensional (2D) study. The diagnoses were exclusively on the basis of 2D findings. The 3D volumes were sliced offline in the 3 dimensions to selectively display specific cardiac structures and reviewed independent of the 2D findings. The 3D studies were graded as: A, new finding not on 2D studies; B, useful anatomic perspective; C, equivalent to 2D studies; or D, missed 2D findings. Compared with 2D echocardiography, 3D echocardiography was graded A in 7 (7%), B in 19 (18%), C in 65 (61%), and D in 15 (14%) cases. In the 26 grade-A and grade-B studies, mitral valve disease and congenital heart disease accounted for 16 (61%) cases. Suboptimal image quality was present in 7 (47%) of the 15 grade-D studies. Thus, real-time 3D echocardiography yields anatomic information comparable with conventional 2D echocardiography in the majority of patients. It can provide new and useful anatomic insight, particularly in patients with mitral valve disease and congenital heart disease. Suboptimal image quality remains a problem for real-time 3D echocardiography in some patients.

Echocardiography↗
PubMed2004

Prevalence and significance of increased intraventricular velocities in healthy elderly subjects.

BACKGROUND: Heart murmurs are common in the elderly and increased intracavitary velocities (IIV) within the left ventricle have been reported to be a cause of systolic murmur. OBJECTIVE: To assess the prevalence and functional significance of IIV in healthy elderly subjects METHODS: Ambulatory healthy elderly subjects were recruited from community centres and seniors' apartments. They were screened using a structured questionnaire and then underwent a comprehensive history and physical examination. Electrocardiogram, echocardiogram and 6-min walk test were performed on the same day. RESULTS: Four of the 88 subjects were excluded because of significant valvular dysfunction. Ten of the remaining 84 subjects had IIV and their demographics were similar to those of the 74 subjects without IIV. Echocardiographic parameters including left ventricular size and mass were similar between the two groups. Left ventricular mass index was lower in subjects with IIV (P=0.02). Both groups had similar 6-min walk results. CONCLUSIONS: In the healthy elderly who do not have valvular disease or left ventricular hypertrophy, IIV is uncommon and does not appear to have functional significance.

Aged↗
PubMed2003

A randomized trial of aspirin on the risk of embolic events in patients with infective endocarditis.

OBJECTIVES: This study examined the effect of aspirin on the risk of embolic events in infective endocarditis (IE). BACKGROUND: Embolism is a major complication of IE, and studies in animal models have shown that platelet inhibition with aspirin can lead to more rapid vegetation resolution and a lower rate of embolic events. METHODS: We conducted a randomized, double-blinded, placebo-controlled trial of aspirin treatment (325 mg/day) for four weeks in patients with IE to test the hypothesis that the addition of aspirin would reduce the incidence of clinical systemic embolic events. Patients with perivalvular abscess were excluded. Serial cerebral computed tomograms and transesophageal echocardiograms were obtained in a subset of patients. RESULTS: During the four-year study period, 115 patients were enrolled: 60 assigned to aspirin and 55 assigned to placebo. Embolic events occurred in 17 patients (28.3%) on aspirin and 11 patients (20.0%) on placebo, with an odds ratio (OR) of 1.62 (95% confidence interval [CI] 0.68 to 3.86, p = 0.29). There was a trend toward a higher incidence of bleeding in the patients taking aspirin versus placebo (OR 1.92, 95% CI 0.76 to 4.86, p = 0.075). Development of new intracranial lesions was similar in both groups. Aspirin had no effect on vegetation resolution and valvular dysfunction. CONCLUSIONS: In endocarditis patients already receiving antibiotic treatment, the addition of aspirin does not appear to reduce the risk of embolic events and is likely associated with an increased risk of bleeding. Aspirin is not indicated in the early management of patients with IE.

Aged↗
PubMed2003

Is aortic stenosis a preventable disease?

Aortic stenosis (AS) is the most common valvular disease requiring valve replacement. Its prevalence increases with age. When the severity of AS is only mild to moderate, it is well tolerated. When it becomes severe, AS confers significant morbidity and mortality. Adverse events can be avoided if it is possible to prevent or retard the progression from mild or moderate AS to severe AS. Progression of AS parallels the progression of sclerotic changes involving the aortic valve, which share histological and immunochemical similarities with the process of atherosclerosis. Far from being just a degenerative process, the development of AS is a complex and highly regulated process with a number of modifiable factors. One of the key factors appears to be lipoproteins, which are intimately involved in several pathways crucial to the development of AS. The importance of lipoproteins is further supported by epidemiological and clinical studies showing a strong association between lipoproteins and AS. The time has come to initiate prospective studies to assess the effect of cholesterol lowering on the progression of AS.

Animals↗
PubMed2003

Functional and echocardiographic improvement following multisite biventricular pacing for congestive heart failure.

BACKGROUND: Heart failure remains a major cause of morbidity and mortality despite advances in pharmacological treatment. Recently, multisite biventricular pacing has been used in the treatment of patients with heart failure. OBJECTIVES AND METHODS: The short and medium term effects of this treatment modality were assessed, and the association between baseline clinical characteristics and the positive response to treatment was investigated. Consecutive patients who received this treatment modality were included. They underwent comprehensive clinical and echocardiographic assessment including a 6 min walk at baseline, one month and three months. RESULTS: Between January 1998 and June 1999, 95 patients received multisite biventricular pacing therapy in the three participating hospitals. In 63 patients with complete three-month follow-ups, there were improvements from baseline to three-month follow-up in New York Heart Association heart failure (3.3 +/- 0.5 to 2.2 +/- 0.6, P<0.001) and 6 min walk (305 +/- 120 to 403 +/- 113 m, P<0.001). Significant salutary changes in echocardiographic measurements were also observed in left ventricular (LV) diastolic dimension, ejection fractions (EFs), interventricular contraction delay and severity of mitral regurgitation (MR). The 63 patients were categorized into responders (n=42) and nonresponders (n=21) based on the clinical response. Clinical characteristics were similar between the two groups. The responders had a more pronounced decrease in QRS width. An increase in LVEF and a reduction in LV diastolic dimension, interventricular mechanical delay and severity of MR were observed in the responders but not in the nonresponders. Furthermore, there was a positive association between the reduction in QRS width and the increase in LVEF. CONCLUSIONS: Cardiac resynchronization by means of multisite pacing appears to be a promising therapy in the treatment of heart failure. The salutary clinical response is associated with echocardiographic improvement.

Aged↗
PubMed2003

Acute aortic intimal tear without a mobile flap mimicking an intramural hematoma.

Several variants of aortic pathology must be considered in the differential diagnosis of the patient presenting with an acute aortic syndrome. In addition to aortic dissection, such entities include intramural hematoma, penetrating aortic ulcer, and localized intimal tear without dissection. These lesions, which lack a mobile intimal flap, may be difficult to correctly identify by transesophageal echocardiography or other imaging modalities. We present a case of an acute aortic syndrome with unusual features on transesophageal echocardiography.

Acute Disease↗
PubMed2002

Early clinical course and long-term outcome of patients with infective endocarditis complicated by perivalvular abscess.

BACKGROUND: Perivalvular abscess is an ominous development in patients with infective endocarditis. There is little information concerning the long-term outcome of these patients. METHODS: Patients admitted to a tertiary care centre in Ottawa between November 1987 and December 1995 because of infective endocarditis complicated by perivalvular abscess were identified by chart audit and by review of the transesophageal echocardiography database. The patients were followed for at least 4 years to determine cardiac complications, late cardiac surgery, long-term outcome and functional status. RESULTS: Forty-three consecutive patients with infective endocarditis and perivalvular abscess (32 men and 11 women; mean age 56 [standard deviation 16] years) were identified; 17 had native valve endocarditis and 26 had prosthetic valve endocarditis. Of the 43 patients, 31 had cardiac surgery during the hospital stay; 6 died in hospital, and 10 died during follow-up. Twelve patients received medical treatment alone; none died in hospital, and 8 died during follow-up. The medically treated patients had less severe heart failure than the surgically treated patients (p = 0.12), but the 2 groups were similar in age and infective organisms. After a mean of 4.5 years of follow-up, the cumulative death rate was 57%; survival was similar among the medically and surgically treated patients. The survivors were younger than the nonsurvivors (p = 0.04). Complications of perivalvular abscess, including pseudoaneurysms and fistulae, were common, occurring in all medically treated patients and in 10 of the 24 surgically treated patients who had follow-up transesophageal echocardiography. INTERPRETATION: Patients with infective endocarditis and perivalvular abscess had a high rate of death after hospital discharge and a high incidence of complications of perivalvular abscess, despite early surgical intervention in most patients. Lower age was the only predictor of long-term survival.

Abscess↗