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Yat-Yin Lam

Publications and source records attributed to Yat-Yin Lam.

8 recordsLinked to original sources
PubMed2006

Ventricular endocrine and mechanical function following thrombolysis for acute myocardial infarction.

OBJECTIVE: The objective of this study was to assess natriuretic peptide release following acute myocardial infarction, and its relationship with ventricular function. METHODS: A total of 44 patients with acute myocardial infarction were studied; 13 anterior, age (57+/-12 years) and 31 inferior, age (58+/-12 years). Peptide levels and left ventricular function by echocardiography were assessed at admission and on days 7 and 30 after thrombolysis. Healthy volunteers (n=21) served as controls. RESULTS: Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) levels rose from admission to day 7 (p=0.002). While ANP remained elevated at day 30 in both groups, BNP levels fell in patients with anterior myocardial infarction (p=0.03). Left ventricular fractional shortening was reduced at admission in the two groups (p=0.01) but returned towards normal in 7 days (p=0.001) in inferior myocardial infarction and in 30 days in anterior myocardial infarction (p=0.02). Left ventricular long axis amplitude was universally reduced at admission (p=0.01) and remained abnormal at day 30 (p=0.01) in both groups. At day 7, BNP and ANP levels inversely correlated with long axis amplitude of lateral wall in anterior myocardial infarction; (r=-0.7, p=0.01). BNP correlated inversely with fractional shortening in anterior myocardial infarction (r=-0.7, p=0.01) at day 30. CONCLUSION: The elevated peptide levels at 7 days post-myocardial infarction correlate with reduced mechanical activity of the adjacent noninfarcted segment. Natriuretic peptides release seem to be related to failure of compensatory hyperdynamic activity of the noninfarcted area rather than directly from the injured myocardial segments.

Atrial Natriuretic Factor↗
PubMed2006

Benefits of cardiac resynchronization therapy for heart failure patients with narrow QRS complexes and coexisting systolic asynchrony by echocardiography.

OBJECTIVES: This study was designed to evaluate the role of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with narrow QRS complexes (<120 ms) and echocardiographic evidence of mechanical asynchrony. BACKGROUND: Cardiac resynchronization therapy is currently recommended to advanced HF patients with prolonged QRS duration. Echocardiographic assessment of systolic mechanical asynchrony has been proven useful to predict a favorable response after CRT. METHODS: A total of 102 HF patients with New York Heart Association (NYHA) functional class III or IV were enrolled. Among them, 51 had wide QRS (>120 ms) and 51 had narrow QRS (<120 ms). Tissue Doppler imaging (TDI) was employed to select patients with systolic asynchrony (increased asynchrony index) in the narrow-QRS group. Clinical and echocardiographic assessments were performed at baseline and 3 months after CRT. RESULTS: There was a significant reduction of left ventricular (LV) end-systolic volume in both narrow (122 +/- 42 cc vs. 103 +/- 47 cc, p < 0.001) and wide (148 +/- 74 cc vs. 112 +/- 64 cc, p < 0.001) QRS groups. Improvement of NYHA functional class (both p < 0.001), maximal exercise capacity (both p < 0.05), 6-min hall-walk distance (both p < 0.01), ejection fraction (both p < 0.001), and mitral regurgitation (both p < 0.005) was also observed. In both groups, the degree of baseline mechanical asynchrony determined LV reverse remodeling to a similar extent, as shown by the superimposed regression lines. Withholding CRT for 4 weeks resulted in loss of echocardiographic benefits. CONCLUSIONS: Cardiac resynchronization therapy for HF patients with narrow QRS complexes and coexisting mechanical asynchrony by TDI results in LV reverse remodeling and improvement of clinical status. The amplitude of benefit is similar to the wide-QRS group provided that similar extent of systolic asynchrony is selected.

Aged↗
PubMed2006

Diastolic and systolic asynchrony in patients with diastolic heart failure: a common but ignored condition.

OBJECTIVES: The present study aimed to examine whether diastolic and systolic asynchrony exist in diastolic heart failure (DHF) and their prevalence and relationship to systolic heart failure (SHF) patients. BACKGROUND: Few data exist on mechanical asynchrony in DHF. METHODS: Tissue Doppler echocardiography was performed in 373 heart failure patients (281 with SHF and 92 with DHF) and 100 normal subjects. Diastolic and systolic asynchrony was determined by measuring the standard deviation of time to peak myocardial systolic (Ts-SD) and peak early diastolic (Te-SD) velocity using a 6-basal, 6-mid-segmental model, respectively. RESULTS: Both heart failure groups had prolonged Te-SD (DHF vs. SHF vs. controls subjects: 32.2 +/- 18.0 ms vs. 38.0 +/- 25.2 ms vs. 19.5 +/- 7.1 ms) and Ts-SD (31.8 +/- 17.0 ms vs. 36.7 +/- 15.2 ms vs. 17.6 +/- 7.9 ms) compared with the control group (all p < 0.001 vs. control subjects). Based on normal values, the DHF group had comparable diastolic (35.9% vs. 43.1%; chi-square = 1.48, p = NS), but less systolic asynchrony than the SHF group (39.1% vs. 56.9%; chi-square = 8.82, p = 0.003). Normal synchrony, isolated systolic, isolated diastolic, and combined asynchrony were observed in 39.1%, 25.0%, 21.7%, and 14.1% of DHF patients, respectively, and these were 25.6%, 31.3%, 17.4%, and 25.6%, correspondingly, in SHF (chi-square = 10.01, p = 0.019). The correlation between systolic and diastolic asynchrony, and between the myocardial velocities and corresponding mechanical asynchrony appeared weak. A wide QRS duration (>120 ms) was rare in DHF (10.9% vs. 37.7% in SHF) (chi-square = 16.69, p < 0.001). CONCLUSIONS: Diastolic and/or systolic asynchrony was common in 61% of DHF patients despite narrow QRS complex. The presence of asynchrony was not related to myocardial systolic or diastolic function. Systolic and diastolic asynchrony were not tightly coupled, implying distinct mechanisms.

Aged↗
PubMed2006

Are left ventricular diastolic function and diastolic asynchrony important determinants of response to cardiac resynchronization therapy?

Cardiac resynchronization therapy (CRT) has been shown to reduce symptoms and reverse left ventricular (LV) remodeling. It is not known, however, whether diastolic function will improve after CRT and diastolic asynchrony will predict LV reverse remodeling. Seventy-six patients (mean age 65 +/- 12 years, 74% men) who received CRT were studied at baseline and after 3 months. Diastolic function was assessed by transmitral Doppler and tissue Doppler imaging. LV systolic and diastolic asynchrony were assessed by the time to peak myocardial contraction (Ts) and early diastolic relaxation (Te) using the 6 basal, 6 mid-segmental model. There were 42 responders (55%) with LV reverse remodeling (defined as a reduction of LV end-systolic volume >or=15%). Parameters of systolic function were significantly improved only in the responders. For diastolic function, there were reductions of transmitral E velocity in the 2 groups, without any change in atrial velocity or the E/A ratio. Tissue Doppler imaging revealed that myocardial early diastolic velocity was unchanged in responders but was significantly worsened in nonresponders. The systolic asynchrony index (the SD of Ts of 12 LV segments) correlated significantly with LV reverse remodeling (r = -0.64, p <0.001) but not the diastolic asynchrony index (the SD of Te of 12 LV segments) (r = -0.10, p = NS). The systolic asynchrony index was the only independent predictor of reverse remodeling (beta = -0.99, 95% confidence interval -1.41 to -0.58, p <0.001). In conclusion, CRT improves systolic function and systolic asynchrony but has a neutral effect on diastolic function and diastolic asynchrony. LV reverse remodeling response is determined by the severity of prepacing systolic asynchrony but not diastolic asynchrony or the diastolic filling pattern.

Aged↗
PubMed2006

"Isolated" diastolic dysfunction in left ventricular outflow tract obstruction.

We sought to investigate the prescence of "isolated" diastolic disease, defined as reduced long-axis early diastolic velocity with normal systolic velocity, in 21 young patients with left outflow tract obstruction. Most patients had depressed systolic velocities despite normal ejection fractions. The close relations amond long-axis velocities suggest isolated diastolic disease is unlikely.

Adult↗
PubMed2006

Effect of age and heart rate on atrial mechanical function assessed by Doppler tissue imaging in healthy individuals.

BACKGROUND: The potential usefulness of Doppler tissue imaging (DTI) to assess atrial mechanical function in cardiac disease has been demonstrated. However, there are few reports on normal values of atrial function by DTI analysis. METHODS: Echocardiography with color-coded DTI was performed in 131 healthy control subjects. The peak atrial contraction velocity (V(A)) and the timing of mechanical events were assessed offline at the left atrial (LA) and right atrial (RA) free wall and interatrial septum. RESULTS: V(A) was higher in the RA (9.0 +/- 2.6 cm/s) than the LA (7.5 +/- 2.4 cm/s, P < .001), and both sites were higher than the interatrial septum (5.6 +/- 1.3 cm/s, both P < .001). The interatrial delay was 24 +/- 21 milliseconds. V(A) at the LA was higher in the participants aged 60 years or older than those who were younger than 60 years (8.1 +/- 2.7 vs 6.7 +/- 1.4 cm/s, P < .001), as was the velocity at the RA (9.6 +/- 2.8 vs 8.0 +/- 2.1 cm/s, P < .01). V(A) at the LA was higher in the participants with heart rate of 60/min or higher than those with lower heart rate (7.9 +/- 2.5 vs 6.8 +/- 1.8 cm/s, P < .05). Sex difference had no effect on V(A) and timings of atrial events. CONCLUSIONS: Assessment of atrial mechanical function by DTI is feasible in healthy individuals. The V(A) is the highest at the RA, followed by LA, and the lowest at the interatrial septum. Older age and faster heart rate seems to augment V(A) in the atrial walls.

Aging↗