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Siu-Sun Yao

Publications and source records attributed to Siu-Sun Yao.

12 recordsLinked to original sources
PubMed2006

Comparison of heart rate reserve versus 85% of age-predicted maximum heart rate as a measure of chronotropic response in patients undergoing dobutamine stress echocardiography.

The role of heart rate (HR) reserve (HRR) in the risk stratification of patients who undergo dobutamine stress echocardiography is not well defined. This study evaluated 1,323 patients (mean age 63 +/- 13 years, 47% men) who underwent dobutamine stress echocardiography. Abnormal stress echocardiographic results were defined as those with stress-induced ischemia. HRR was defined as [(peak HR - HR at rest)/(220 - age - HR at rest)] x 100, with HRR <70% defined as low. Follow-up data (2.7 +/- 1.1 years) for confirmed myocardial infarction (n = 16) and cardiac death (n = 58) were obtained. HRR risk stratified patients into normal and abnormal subgroups (event rate 1.1%/year vs 4.2%/year, p <0.0001) and further risk stratified patients into normal (adjusted HR 1 [reference] vs 2.88, p = 0.04) and abnormal (adjusted HR 4.17 vs 10.09, p <0.0001) stress echocardiography groups. Low HRR (relative risk [RR] 2.15, 95% confidence interval [CI] 1.23 to 4.01, p = 0.013) was an independent predictor of cardiac event even after controlling for standard cardiovascular risk factors, other stress electrocardiographic variables, and stress echocardiographic variables. Low HRR (chi-square 32) was superior to 85% maximum predicted HR (MPHR; chi-square 18) and provided incremental value over stress echocardiography and 85% MPHR (global chi-square increased from 48.3 to 54 to 61.3, p <0.0001) in a model consisting of stress echocardiography, MPHR, and HRR. In conclusion, HRR can further risk stratify patients who undergo dobutamine stress echocardiography and provides independent and incremental prognostic value over standard cardiovascular risk factors and also independent of echocardiographic myocardial ischemia and left ventricular dysfunction and is superior to 85% MPHR. In the setting of low HRR, normal stress echocardiographic results are prognostically less benign, whereas abnormal stress echocardiographic results are prognostically more malignant.

Adrenergic beta-Antagonists↗
PubMed2006

Role of angiographic coronary artery collaterals in transient ischemic left ventricular cavity dilatation during stress echocardiography.

BACKGROUND: The role of coronary artery collaterals in transient ischemic left ventricular (LV) dilatation (TID) during stress echocardiography is not well defined. HYPOTHESIS: Transient ischemic LV dilatation is a marker for extensive and severe coronary artery disease and represents patients without good collaterals. METHODS: We evaluated 212 consecutive patients (57 +/- 16 years, 70% male) who had coronary angiography and stress echocardiography within a 3-month period. This cohort of patients was divided into three groups based on type of collaterals: Group A: no collaterals; Group B: collaterals supplied by vessels without flow-limiting stenosis (good collaterals); Group C: collaterals supplied by vessels with flow-limiting stenosis (bad/jeopardized collaterals). In all patients, angiographic jeopardy score (AJS), ejection fraction (EF), and wall motion score index (WMSI) at rest and during stress were evaluated. Transient ischemic LV dilatation was defined as transient increase in the end-systolic dimensions from rest to peak stress. RESULTS: Transient ischemic LV dilatation was present in 42 (20%) patients. Patients with TID had a lower EF, higher AJS, greater number of ischemic segments, and higher peak WMSI. Patients with TID in Group A (no collaterals) and Group C (jeopardized collaterals) had a greater percentage of multivessel disease than those in Group B (good collaterals). Presence of Group A or Group C collaterals was a predictor of TID even after controlling for multivessel disease, rest and peak WMSI, and left anterior descending artery disease. CONCLUSIONS: Transient ischemic LV dilatation on stress echocardiography is a marker for extensive and severe coronary artery disease and represents patients with angiographically absent collaterals or those with jeopardized coronary collaterals.

Adult↗
PubMed2006

Incremental prognostic value of stress echocardiography over clinical and stress electrocardiographic variables in patients with prior myocardial infarction: "warranty time" of a normal stress echocardiogram.

BACKGROUND: Patients with prior myocardial infarction (MI) are at increased risk of subsequent cardiac events (MI or cardiac death). The incremental prognostic value and warranty time of a normal stress echocardiogram in this high-risk population is not well defined. METHODS: We evaluated 251 consecutive patients (62 +/- 11 years; 64% males) with remote history of MI (>6 weeks) undergoing stress echocardiography (83% dobutamine). Ischemia was defined as a new reversible wall motion abnormality and/or biphasic response. Follow-up for up to 4 years (mean 2.9 +/- 1.0 years) for confirmed MI (n = 7) and cardiac death (n = 15) were obtained. RESULTS: Stress echocardiography effectively risk stratified patients into normal versus abnormal subgroups (Event rate 0.8% per year vs 4.2% per year; P = 0.01; RR = 5.6, 95% CI = 1.3-24.7). In patients with a normal stress echocardiogram, the event rate at the end of 6, 12, and 18 months were <1% per year. After 18 months the event rate in patients with a normal stress echocardiogram increased greatly (>1% per year). Stress echocardiography yields incremental prognostic value over clinical and stress electrocardiographic variables (Global chi-square increased from 12.4 to 25 to 31.1, P < 0.0001 both groups). CONCLUSIONS: Stress echocardiography yields appropriate risk stratification and prognosis and provides incremental prognostic value over clinical and stress electrocardiographic variables even in patients with prior MI. A normal stress echocardiogram portends a benign prognosis (<1% event rate/year) for up to 18 months.

Cardiotonic Agents↗
PubMed2005

Comparison of prognostic value of stress echocardiography versus stress electrocardiography in patients with suspected coronary artery disease.

Stress electrocardiographic (ECG) ST-segment depression is a prognostic marker of adverse cardiac outcomes in coronary artery disease. However, use of concurrent stress echocardiography (ECHO) has lead to concordant and discordant findings on stress electrocardiogram during stress studies. The prognostic value of stress ECHO in the setting of these stress ECG findings has not been previously evaluated. Outcomes of 1,268 patients (60 +/- 12 years old, 48% women) who had normal electrocardiograms and underwent stress ECHO were analyzed. ST-segment depression > or =1.5 mm in 2 contiguous leads on stress electrocardiogram and a wall motion score index of >1 on peak stress echocardiogram were considered abnormal. Events of nonfatal myocardial infarction (n = 18) and cardiac death (n = 32) were analyzed during follow-up (2.8 +/- 0.9 years). In 91 patients (7%) who had abnormal findings on stress electrocardiogram, 38 (41%) had an abnormal finding on stress echocardiogram and 4 had cardiac events (0.6% per year), and all who had a normal finding on stress echocardiogram had no events (n = 53, 59%, p = 0.01). Among 46 events (92%) with a normal finding on stress electrocardiogram, 30 (60%) showed a discordantly abnormal finding on stress echocardiogram (3.2% per year, p <0.01). Overall, the cohort that had normal findings on stress echocardiogram showed a lower event rate (72%, 16 events, 1.1% per year) compared with the cohort that had abnormal findings on stress echocardiogram (28%, 34 events, 3.6% per year, p <0.001), independent of stress ECG response. Peak wall motion score index (hazard ratio 2.55, p <0.001) and left ventricular ejection fraction (hazard ratio 0.99, p <0.001) were independent and incremental (global chi-square, p <0.001) prognostic markers by stress ECHO. In conclusion, a normal finding on stress echocardiogram confers a benign prognosis independent of the type of stress ECG response during stress studies. In addition, peak wall motion score index and ejection fraction by ECHO are stronger prognostic markers over stress electrocardiography in patients who are evaluated for coronary artery disease.

Adult↗
PubMed2005

Stress function index, a novel index for risk stratification and prognosis using stress echocardiography.

OBJECTIVES: The purpose of the study was to define an appropriate parameter for risk stratification and prognosis of patients undergoing stress echocardiography. BACKGROUND: Among stress echocardiography variables, peak wall-motion score index (WMSI) and ejection fraction (EF) have been shown to be independent and significant predictors of cardiovascular morbidity and mortality. Data on the impact and importance of each parameter in risk stratification and prognosis are limited. METHODS: We evaluated 1560 patients (59 +/- 13 years; 51% men) undergoing stress echocardiography (36% treadmill, 64% dobutamine). Peak WMSI was derived from the cumulative sum of 16 left ventricular segments divided by sum of visualized segments at peak stress. The ratio of peak WMSI to EF was calculated for the entire cohort. Based on this ratio and using the receiver operating characteristic curve, patients were divided into 3 groups: low- (< 1.9), intermediate- (1.9-3.1), and high- (> 3.1) risk subgroups. Follow-up (2.8 +/- 1.1 years) for confirmed myocardial infarction (n = 26) and cardiac death (n = 38) were obtained. RESULTS: Stress echocardiography effectively risk stratified patients into low- (0.7%/y), intermediate- (2.0%/y), and high- (4.4%/y) risk subgroups (P < .0001) based on the ratio of peak WMSI to EF. Cox proportional hazard model showed that risk stratification based on the ratio of peak WMSI to EF (global chi2 = 106.05; P < .0001) provided incremental value beyond that provided by risk stratification by peak WMSI (global chi2 = 79.23; P < .0001) or risk stratification by EF alone (global chi2 = 87.12; P < .0001). CONCLUSIONS: The ratio of peak WMSI to EF (stress function index) provides best incremental prognostic value and effectively risk stratifies patients into low-, intermediate-, and high-risk subgroups and is better than risk stratification by either peak WMSI or EF alone. The results of stress echocardiography should routinely combine peak WMSI and EF for effective risk stratification.

Dobutamine↗
PubMed2005

Assessment of myocardial viability with dobutamine stress echocardiography in patients with ischemic left ventricular dysfunction.

The noninvasive assessment of myocardial viability has proved clinically useful for distinguishing hibernating and/or stunned myocardium from irreversibly injured myocardium in patients with chronic ischemic heart disease or recent myocardial infarction, with marked regional and/or global left ventricular (LV) dysfunction. Noninvasive techniques utilized for the detection of viability in asynergic myocardial regions include positron emission tomographic imaging of residual metabolic activity, single photon emission tomography (SPECT) of radioisotope uptake with thallium-201, low-dose dobutamine echocardiography assessment of inotropic reserve and myocardial contrast echocardiography for evaluation of microvascular integrity. Of these techniques, dobutamine stress echocardiography is a safe, widely available and relatively inexpensive modality for the identification of myocardial viability for risk stratification and prognosis. Low-dose dobutamine response can accurately predict improvement of dysfunctional yet viable myocardial regions, and thus identify a subset of patients whose LV function will improve following successful coronary revascularization.

Cardiotonic Agents↗
PubMed2004

Comparison of stress-induced myocardial ischemia in patients with and without coronary arterial collaterals.

Coronary artery collaterals may have a protective role against myocardial ischemia at rest. However, their role during stress is controversial and poorly defined. We evaluated 212 consecutive patients (57 +/- 16 years; 70% men) who underwent coronary angiography and stress echocardiography within a 3-month period. This cohort of patients (all had significant epicardial coronary artery disease) was divided into 3 groups based on the presence and type of collaterals: group A, no collaterals; group B, collaterals supplied by vessels without flow-limiting stenosis; and group C, collaterals supplied by vessels with flow-limiting stenosis. In all patients, angiographic jeopardy score, ejection fraction, and regional and cumulative wall motion score indexes (WMSIs) at rest and during stress were evaluated. Angiographic jeopardy scores were 2.9, 3.5, and 7.3 for groups A, B, and C, respectively. Baseline ejection fraction was similar between groups A and B (48% vs 46%, p = NS) but lower in group C (31%, p <0.01). During stress echocardiography, all groups demonstrated a significant increase in WMSI from baseline (WMSI at rest vs that during stress 1.72 +/- 0.06 vs 1.79 +/- 0.04 for group A, 1.97 +/- 0.06 vs 2.09 +/- 0.03 for group B, 2.35 +/- 0.11 vs 2.41 +/- 0.07 for group C; p <0.01 for all groups). In addition, the number of ischemic segments increased significantly in all groups (2.96 +/- 0.07 in group A vs 4.52 +/- 0.11 in group B vs 5.61 +/- 0.13 in group C, p <0.01). Coronary artery collaterals do not offer protection against stress-induced myocardial ischemia. Moreover, the presence of jeopardized angiographic coronary collaterals (group C) is associated with a higher angiographic jeopardy score, higher baseline WMSI, and decreased ejection fraction.

Collateral Circulation↗
PubMed2004

Novel stress echocardiographic model incorporating the extent and severity of wall motion abnormality for risk stratification and prognosis.

The prognostic value of stress echocardiography to predict future cardiac events using the extent and severity of wall motion abnormalities is not well defined. The objective of this study was to develop and validate a prognostic model for interpretation of stress echocardiographic studies by using the extent and severity of wall motion abnormalities. We evaluated 1,500 patients (59 +/- 13 years old; 51% men) who underwent stress echocardiography (34% on the treadmill exercise and 66% on dobutamine). Left ventricular regional wall motion was assessed by consensus of 2 experienced echocardiographers. Follow-up periods (mean 2.7 +/- 1.0 years) for confirmed myocardial infarction (n = 31) and cardiac death (n = 44) were identified. Multivariate regression analysis identified 2 independent predictors of cardiac events: the number of left ventricular wall segments with new wall motion abnormalities (an index of the extent of ischemia) and the maximal magnitude of new wall motion abnormalities (an index of the severity of ischemia). The ischemic extent (chi-square 48.7, p <0.0001) and maximal severity (chi-square 52.0, p <0.0001) were exponentially correlated with an increase in event rate. On the basis of these data, a prognostic model was defined that uses ischemic extent and maximal severity as stress-dependent orthogonal variables. With this 3-dimensional model, the predicted event rate ranged over sevenfold, from a low of 0.9%/year in patients without any wall motion abnormalities to a high of 6.7%/year in patients with extensive and severe wall motion abnormalities. The extent and severity of wall motion abnormalities by stress echocardiography are independent and cumulative predictors of prognosis in patients who have suspected or known ischemic heart disease.

Aged↗
PubMed2004

Prospective validation of a quantitative method for differentiating ischemic versus nonischemic cardiomyopathy by technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography.

BACKGROUND: Myocardial perfusion single-photon emission computed tomography (SPECT) permits assessment of stress perfusion and resting left ventricular (LV) function. Quantitative analysis of perfusion patterns among patients with LV dysfunction offers an opportunity for developing criteria to differentiate ischemic from nonischemic cardiomyopathy. HYPOTHESIS: Quantitative assessment of SPECT may allow differentiation between ischemic and nonischemic cardiomyopathy. METHODS: We evaluated 144 patients with LV ejection fraction < or =40%, divided into 63 patients with nonischemic and 81 with ischemic cardiomyopathy. Mean relative myocardial counts were obtained for regions drawn over defect and normal zones on rest and stress polar perfusion maps. RESULTS: Multivariate logistic regression analysis of significant univariate SPECT predictors of ischemic cardiomyopathy revealed that the stress defect severity ratio (SDSR) was the best predictor of ischemic cardiomyopathy (p < 0.0001). By receiver operator characteristic (ROC) curve analysis, an SDSR of < or =45% optimized prediction of ischemic cardiomyopathy (sensitivity 81%, specificity 96%). An SDSR of < or =45% occurred in 65 of 81 (80%) patients with ischemic cardiomyopathy, but in only 3 of the 63 (4%) patients with nonischemic cardiomyopathy (p < 0.0001). Applying the < or =45% SDSR threshold to a prospective group of 89 patients yielded a somewhat lower sensitivity (60%), but retained high specificity (91%) for identifying ischemic cardiomyopathy (p = NS vs. retrospective group). CONCLUSIONS: Presence of a severe and extensive stress perfusion defect is a hallmark of ischemic cardiomyopathy. By contrast, a mild stress perfusion defect (SDSR of >45%) is commonly present among patients with ischemic and nonischemic cardiomyopathy. An SDSR of < or =45% is a reproducible specific marker for identifying the presence of ischemic cardiomyopathy.

Aged↗
PubMed2003

Isometric handgrip exercise during dobutamine-atropine stress echocardiography increases heart rate acceleration and decreases study duration and dobutamine and atropine dosage.

BACKGROUND: Dobutamine-atropine stress echocardiography (DASE) is an established test for the diagnosis and risk stratification of patients with coronary artery disease. Atropine use to attain target heart rate prolongs test time. HYPOTHESIS: The aim of this study was to assess the utility of isometric handgrip exercise (33% maximal voluntary contraction x 4 min) with DASE. METHODS: We prospectively evaluated 131 patients undergoing DASE randomized to handgrip exercise or no handgrip. Effect of handgrip exercise on endpoints: time to target heart rate (85% maximum predicted), recovery time, total test time, mean dobutamine and atropine dosage, and the number of ischemic responses were assessed. Effect of current beta-blocker medication use was also evaluated. RESULTS: Heart rate rose more quickly in the handgrip group. At 6-10 min (peak handgrip), mean heart rate rose 51 +/- 14 beats/min in the handgrip group compared with 38 +/- 18 beats/min in the no handgrip group (p < 0.0001). With handgrip, overall dobutamine study time was reduced by a mean of 4.3 min (16.4 +/- 6.9 vs. 20.7 +/- 8.4, p = 0.004) in all patients, and by a mean of 5.9 min in patients not on beta-blocker medication (p = 0.001). The handgrip group also had a lower mean dose of dobutamine (25.8 +/- 13.5 vs. 32.4 +/- 16.4 mg, p = 0.025). The mean atropine dose was also lower (0.2 +/- 0.4 vs. 0.4 +/- 0.5 mg, p = 0.04). Handgrip exercise, however, did not decrease endpoints in patients on beta-blocker medication. CONCLUSIONS: Use of isometric handgrip exercise with DASE decreases time to target heart rate, recovery time, overall study time, and mean dosage of dobutamine and atropine. In patients not on beta-blocker medication, handgrip exercise should be routinely incorporated into all DASE protocols.

Adrenergic beta-Antagonists↗
PubMed1998

Assessment of Left Atrial Appendage Structure and Function by Transesophageal Echocardiography: A Review.

This article examines the transesophageal echocardiographic assessment of the left atrial appendage anatomy and function in individuals without significant structural heart disease and in those with atrial fibrillation with or without cardioembolism or mitral valve stenosis. We also summarize the available data in the usefulness of transesophageal echocardiographic studies in patients undergoing cardioversion for atrial fibrillation and percutaneous balloon valvuloplasty for mitral stenosis. Also, potential limitations and ongoing developments in the use of transesophageal echocardiography in the assessment of the left atrial appendage are outlined, and recommendations are given for the uniform reporting of quantitative data.

Journal Article↗