Biomedical subjects

Chi-Ming Chow

Publications and source records attributed to Chi-Ming Chow.

16 recordsLinked to original sources

PubMed2006

Age-related differences in the management and outcome of patients with acute coronary syndromes.

BACKGROUND: Age-related differences in patients with an acute coronary syndrome (ACS) have not been well characterized in prior observational studies that often included only certain age groups or subjects with myocardial infarction (MI). METHODS: We stratified 4627 patients admitted with an ACS across 9 provinces between 1999 and 2001 enrolled in the Canadian ACS Registry into 3 age groups (< 65, 65-74, and > or = 75 years) to evaluate differences in clinical characteristics, management, and 1-year outcome. RESULTS: Older patients more frequently had previous angina, MI, or heart failure and were less likely to have positive cardiac markers, ST elevation, and Q-wave MI or to receive thrombolytics, beta-blockers, and cholesterol-lowering and antiplatelet agents in hospital, at discharge, and at 1 year. In multivariable analyses controlling for patient factors, every decade increase in age was independently associated with reduced use of coronary angiography (odds ratio [OR] 0.79, 95% CI 0.74-0.84, P < .001) and percutaneous coronary intervention (OR 0.88, 95% CI 0.81-0.95, P = .001). When adjusted for validated clinical prognosticators and differences in management, every decade of age increment independently predicted an increased risk of death at 1 year (OR 1.87, 95% CI 1.66-2.12, P < .001). CONCLUSIONS: Across the broad spectrum of ACS, elderly patients had more complex comorbidities and worse outcome, yet they were less likely to undergo revascularization or to receive acute and long-term evidence-based medications. Our findings emphasize the ongoing need to better define and promote optimal therapeutic regimens for elderly patients with ACS.

Age Factors↗

PubMed2006

ST-segment depression in non-ST elevation acute coronary syndromes: quantitative analysis may not provide incremental prognostic value beyond comprehensive risk stratification.

BACKGROUND: It is unclear whether quantitative ST-segment assessment can improve risk stratification of unselected acute coronary syndrome (ACS) patients using the validated Global Registry of Acute Cardiac Events (GRACE) risk model. METHODS: In the prospective, multicenter, Canadian ACS Registry, the admission electrocardiogram was evaluated centrally at a blinded core laboratory. Patients with ST-elevation myocardial infarction and other electrocardiogram confounders were excluded. ST depression (ST down) was measured and summed in all leads except aVR. Patients with ST down were divided into 3 groups based on tertiles of cumulative ST down. A multivariable model was developed to examine the independent prognostic value of ST down severity after adjusting for other known prognosticators in the GRACE risk model. RESULTS: Among 2590 patients with non-ST-elevation ACS, more severe ST down was associated with advanced age, higher heart rate and Killip class, elevated creatinine, abnormal biomarkers, higher GRACE risk score, and higher 1-year mortality (all P < .001). After adjusting for these confounding prognosticators, the presence of any ST down remained independently associated with higher 1-year mortality (odds ratio 1.78, 95% CI 1.21-2.63, P = .004). However, the gradient of risk with increasing magnitude of ST down was no longer evident (adjusted odds ratios 1.77, 1.77, 1.81, for ascending tertiles of cumulative ST down, respectively). Moreover, quantitative ST down did not improve the model discrimination for 1-year mortality. The results were similar when the number of leads with ST down or the maximum magnitude of ST down was analyzed, after adjusting for tertiles of GRACE risk score or inhospital revascularization, or using the composite end point of death or myocardial (re)infarction at 1 year. CONCLUSIONS: Greater ST down is associated with other adverse prognosticators across the broad spectrum of non-ST-elevation ACS. Although the presence of any ST down is an independent predictor of 1-year mortality, its quantitative assessment is not as important as its mere presence when studied on the background of comprehensive clinical and biomarker evaluation in a nonclinical trial-based ACS population.

Aged↗

PubMed2006

Underuse of evidence-based treatment partly explains the worse clinical outcome in diabetic patients with acute coronary syndromes.

BACKGROUND: Diabetes-related differences in treatment and clinical outcome of patients across the entire spectrum of acute coronary syndromes (ACSs) have potential clinical implications but have not been well studied. METHODS: The multicenter, prospective, Canadian ACS Registry enrolled 4578 patients hospitalized for ACS between 1999 and 2001 across 9 provinces in Canada. We compared baseline characteristics, in-hospital and post-discharge treatments, and clinical outcome of diabetic and non-diabetic patients. The impact of diabetes on use of thrombolytic therapy and coronary revascularization; and the independent association between diabetes, treatments, and diabetes-treatment interactions on outcome were examined. RESULTS: Diabetic patients with ACS had more cardiovascular risk factors and higher-risk clinical presentation. They paradoxically received less evidence-based medications in-hospital, at discharge, and at 1-year. Although diabetes independently predicted higher 1-year mortality (OR 1.47, 95% CI 1.15-1.87; P = .002) after adjustment for validated prognosticators, it was also an independent predictor of not receiving thrombolytic therapy (OR 0.72, 95% CI 0.54-0.95; P = .021) and coronary revascularization (OR 0.69, 95% CI 0.59-0.82; P < .001). These underused therapies were all independently associated with reduced 1-year mortality, with no significant diabetes-related treatment-outcome heterogeneity. Importantly, diabetes remained an independent adverse prognosticator even after further adjustment for these differences in treatment. CONCLUSIONS: Evidence-based therapies are underused in the contemporary management of diabetic patients with ACS, which partly explains their worse outcome. Diabetes should be considered a high-risk feature in ACS risk stratification that encourages more intensive treatments. Continued efforts to promote adherence to existing proven therapies and to develop novel treatment strategies targeting diabetes-specific cardiovascular pathophysiology are imperative to improve their adverse prognosis.

Acute Disease↗

PubMed2005

Increasing Internet use among cardiovascular patients: new opportunities for heart health promotion.

BACKGROUND: Information technology is revolutionizing health care delivery. Although data exist for other patient populations, awareness and use of information technology in cardiovascular patients have not been well described to date. OBJECTIVES: To assess the awareness and use of information technology in cardiovascular patients over time. METHODS: A survey of consecutive cardiovascular inpatients and outpatients attending a tertiary care, Canadian academic centre was conducted in 2001. Awareness and use of the Internet, use of the Internet for health information, attitudes toward information technology and barriers to use were studied at baseline (n=300) and at one-year follow-up (n=199). The socioeconomic correlation was also examined. RESULTS: Most respondents were aware of the Internet and e-mail. Internet use for health information was prevalent and increased over time (62 of 105 patients [59%] at baseline versus 76 of 105 patients [72%] at one-year follow-up). E-mail use was also prevalent (102 of 189 patients [54%]) but did not increase over time. Cardiovascular patients who used the Internet for health information and e-mail were employed, and were significantly younger and better educated than patients who did not use them; income status was not a significant indicator of Internet or e-mail use. Most patients (95 of 131 patients [72%]) were interested in communicating with their specialists via e-mail. CONCLUSIONS: Information technology is well accepted by cardiovascular patients in Canada. Internet use for health information was prevalent and increased over time. The present findings suggest that the 'digital divide' is evolving, with a narrowing socioeconomic divide, possibly due to the increasing public access to the Internet. This has important implications for patient education and the specialist-patient relationship.

Cardiovascular Diseases↗

PubMed2005

Regional variation in self-reported heart disease prevalence in Canada.

BACKGROUND: Cardiovascular disease is the leading cause of death in Canada. OBJECTIVE: To provide an analysis of the self-reported prevalence of heart disease and three specific cardiac conditions--myocardial infarction (MI), angina and congestive heart failure (CHF)--in subgroups of the Canadian population. METHODS: Data from the Public Use Microdata File from Statistics Canada's 2000/2001 Canadian Community Health Survey (CCHS) were used to estimate the crude self-reported prevalence of heart disease, MI, angina and CHF in Canada. The data are reported by age and sex groups, as well as by province or territory and health region. RESULTS: Based on the 2000/2001 CCHS data, it was estimated that among Canadians 12 years of age and older, 5.0% (n=1,286,000) have heart disease, 2.1% (n=537,000) have had a heart attack, 1.9% (n=483,000) have angina and 1.0% (n=264,000) have CHF. Marked variation in the prevalence of heart disease and the other specific cardiac conditions exists across age and sex groups, and across geographical regions. The prevalence of heart disease is low among those younger than 50 years; thereafter, the prevalence of heart disease increases and is more common among men than among women. By 70 years of age, at least one in four men and one in five women report having heart disease. Large differences in the burden of heart disease were observed across provinces, territories and health regions. Comparison of the highest and lowest prevalence rates among provinces and territories revealed a 1.9-fold difference for heart disease, a 2.8-fold difference for MI, a 2.3-fold difference for angina and a 3.3-fold difference for CHF. CONCLUSIONS: Large regional differences in the prevalence of heart disease and other specific cardiac conditions were observed across Canada. These data may assist health system planners to identify those regions and population subgroups most affected by heart disease, and to support the development of heart disease prevention and treatment programs.

Adolescent↗

PubMed2005

Natural course of left atrial thrombi after bioprosthetic mitral valve replacement in a patient with heparin-induced thrombocytopenia.

Left atrial (LA) clots involving prosthetic mitral valves are unusual complications of heparin-induced thrombocytopenia (HIT), and little is known about their natural history. A 73-year-old woman underwent bioprosthetic mitral valve replacement, which was complicated by atrial fibrillation and LA thrombus due to HIT. She was treated medically and followed up for 18 months. The present case provides unique insights into the natural history of HIT-related LA thrombus involving a bioprosthetic valve. It highlights the importance of having a high index of suspicion for this condition and avoiding the use of warfarin early in the course of the condition.

Aged↗

PubMed2004

One-year outcome of patients after acute coronary syndromes (from the Canadian Acute Coronary Syndromes Registry).

The objective of this study was to determine the management and outcome of less [corrected] selected patients with an acute coronary syndrome during hospitalization and up to 1 year after discharge. The Canadian Acute Coronary Syndromes Registry was a prospective observational study of patients admitted with suspected acute coronary syndromes. Data on demographic and clinical characteristics, in-hospital treatment, and outcomes were recorded. At 1 year, vital status, medication use, recurrent cardiac events, and procedures were determined by telephone contact. Of the 5,312 patients enrolled, 4,627 had a final diagnosis of acute coronary syndrome, with Q-wave myocardial infarction in 27.7%, non-Q-wave myocardial infarction in 33.2%, and unstable angina pectoris in 39.1%. During hospitalization, coronary angiography and revascularization were performed in 39.6% and 20.3% of patients, respectively. The in-hospital mortality rate was 2.4% overall. At discharge, 87.8%, 76.4%, 56.0%, and 54.8% of patients were prescribed aspirin, beta blockers, angiotensin-converting enzyme inhibitors, and lipid-lowering agents, respectively. Unadjusted 1-year mortality rates for hospital survivors were 6.5%, 10%, and 5.4% for those with Q-wave myocardial infarction, non-Q-wave myocardial infarction, and unstable angina pectoris groups, respectively (p <0.0001). This difference in mortality rate remained significant after adjusting for other prognosticators, whereas the use of coronary angiography and revascularization after discharge was similar across patients. At 1 year, fewer patients were maintained on aspirin and beta blockers, whereas the use of lipid-lowering therapy increased (all p <0.0001). Despite similar rates of coronary angiography and revascularization after discharge, patients with non-Q-wave myocardial infarction had worse outcomes at 1 year. Moreover, there was a significant opportunity to enhance the discharge and long-term use of evidence-based secondary prevention therapies.

Aged↗

PubMed2004

Clinical trial--derived risk model may not generalize to real-world patients with acute coronary syndrome.

BACKGROUND: Accurate risk stratification can guide clinical decision-making in the management of acute coronary syndromes (ACS). However, the applicability of risk models to the general ACS population remains unclear. The purpose of this study was to validate and compare a modified international clinical trial and a registry-based risk model in a contemporary, less selected ACS population. METHODS: In the prospective, observational Canadian ACS Registry, 4627 patients with ACS were enrolled from 51 centers. Baseline patient data were recorded on standardized case report forms. We evaluated risk models derived from the Platelet glycoprotein IIb/IIIa in Unstable angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) and the Global Registry of Acute Cardiac Events (GRACE) predicting in-hospital death among patients with non-ST-elevation ACS. Model discrimination was measured by the c-statistic, and calibration was assessed graphically and by the Hosmer-Lemeshow goodness-of-fit test. RESULTS: In-hospital mortality rates were 2.4% overall and 1.5% among the patients with non-ST-elevation ACS (n = 2925; 63.2%) in our validation cohort. Both the in-hospital PURSUIT and GRACE risk models showed similar and good prognostic discrimination (c-statistics = 0.84 and 0.83, respectively; P = .69 for difference). The GRACE model also demonstrated good calibration (Hosmer-Lemeshow P = .40). In contrast, calibration in the PURSUIT model was poor (Hosmer-Lemeshow P < .001), with consistent overestimation of risks. CONCLUSIONS: Both the PURSUIT and GRACE models demonstrated good discrimination for in-hospital mortality rates in the Canadian ACS Registry. However, the GRACE risk model, derived from a less selected population, provided superior calibration in risk assessment across the spectrum of ACS. Our findings underscore the potential importance of risk model validation in the general ACS population rather than a clinical trial population to establish its generalizability before integration into clinical practice.

Adult↗

PubMed2004

Prosthetic mitral regurgitation can be mimicked by Doppler color flow mapping: avoiding misdiagnosis.

OBJECTIVES: We sought to characterize a region of apparent systolic flow resembling mitral regurgitation (MR) in patients with mechanical disk mitral prostheses as artifact. BACKGROUND: Diagnosing MR in the presence of mechanical prostheses is challenging. Occasionally, important MR is suggested by a substantial region of systolic Doppler color flow in an acoustically shadowed region of the left atrium when, in fact, only trace MR exists. We hypothesized this pseudo-MR is caused by acoustic mirroring of the left ventricular outflow tract (LVOT) flow by sound reflected off the prosthesis, projecting flow into the left atrium because of longer transit time. METHODS: We reviewed 19 patients with mechanical mitral valves and trace MR by transesophageal echocardiography who had transthoracic echocardiography studies within 1 week (group A), and prospectively studied 22 consecutive patients by transthoracic echocardiography with subtle transducer angulation variation to detect pseudo-MR and characterize it by pulsed Doppler (group B). RESULTS: In group A, 12 of 19 patients had evidence of pseudo-MR on review of their transthoracic echocardiograms, absent by transesophageal echocardiography. In group B, this pseudo-MR signal was present in 13 of 22 patients, with velocity and timing by pulsed Doppler comparable with LVOT flow (onset at 125 +/- 27 milliseconds vs 135 +/- 11 milliseconds from QRS, P = not significant). The angle between the mitral plane and the LVOT, which determines whether this mirroring can occur, was smaller for patients with pseudo-MR. CONCLUSION: Artifactual pseudo-MR is often seen with mechanical mitral prostheses. Its behavior and sensitivity to geometric relationships are consistent with mirroring of LVOT flow. Practically, potential misdiagnosis can be readily avoided by pulsed Doppler sampling, sparing the patient further procedures.

Aged↗

PubMed2004

Troponin is more useful than creatine kinase in predicting one-year mortality among acute coronary syndrome patients.

AIMS: To compare the long-term prognostic value of troponins (Tn) vs. conventional cardiac biomarker creatine kinase (CK) and CK-MB across the spectrum of acute coronary syndromes (ACS). METHODS AND RESULTS: In the prospective, observational Canadian ACS Registry, 4627 patients with ACS were enrolled from 51 centres. The CK, CK-MB, Tn samples were analysed in each hospital clinical laboratory and the results related to the reference levels of the individual laboratories. The study cohort comprised 3138 (67.8%) patients who had both CK (or CK-MB) and Tn measurements during the first 24 h of hospitalisation. Vital status at one-year was determined by standardized telephone interview. 61.2% and 59.0% of patients had abnormal Tn and CK (or CK-MB) levels, respectively. Vital status at one-year was ascertained for 2950 patients (6% lost to follow-up). Among patients with normal CK (or CK-MB) levels, elevated Tn was associated with increased one-year mortality (odds ratio [OR] 2.06; 95% CI 1.37-3.11; P=0.001). Similarly, among patients with abnormal CK (or CK-MB) levels, abnormal Tn predicted higher one-year mortality (OR 1.83; 95% CI 1.14-2.93; P=0.01). In contrast, abnormal CK (or CK-MB) was not predictive of mortality after stratification by Tn status. In multivariable analysis controlling for other known prognosticators including creatinine, abnormal Tn (adjusted OR 1.78; 95% CI 1.30-2.44; P<0.001) but not CK/CK-MB was independently associated with increased one-year mortality. CONCLUSIONS: Elevated Tn was independently associated with worse outcome at one-year, while CK or CK-MB status did not provide incremental prognostic information. Our findings support the use of Tn in the risk stratification of unselected ACS patients.

Aged↗

PubMed2004

Canadian Cardiovascular Society Consensus Conference 2002: Management of heart disease in the elderly patient.

Cardiovascular disease is a major health issue for the elderly patient. Many diagnostic, therapeutic and ethical issues are specific for the the older adult with heart disease. The Canadian Cardiovascular Society 2002 Consensus Conference provides recommendations for the most frequently encountered cardiac problems in the elderly patient. A common theme of the recommendations is the need to apply the best evidence based medicine together with an assessment of frailty, comorbidity and quality of life. A major goal of the conference was to identify treatments that are not optimally used in the older patient.

Aged↗

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↗

PubMedDate not supplied

Calcific bicuspid aortic valve disease in a patient with Cornelia de Lange syndrome: linking altered Notch signaling to aortic valve disease.

We describe a patient with Cornelia de Lange syndrome (CdLS) and a severely calcified bicuspid aortic valve. Cornelia de Lange syndrome is characterized by altered Notch signaling, and recent studies have provided a link between Notch signaling and heart valve development and calcific bicuspid aortic valve disease. In this case report, we propose that altered Notch signaling in CdLS may be causally linked to the calcific bicuspid aortic valve disease in these patients. Patients with CdLS should undergo routine echocardiographic examination for possible congenital cardiac defects including bicuspid aortic valve.

Adult↗

PubMedDate not supplied

Factors influencing patient knowledge of warfarin therapy after mechanical heart valve replacement.

BACKGROUND AND RESEARCH OBJECTIVE: Patients with mechanical heart valves must follow lifelong warfarin therapy. Warfarin, however, is a difficult drug to manage because it has a narrow therapeutic window and potentially serious side effects. Successful anticoagulation treatment is dependent upon the patient's knowledge of this drug; however, little is known regarding the determinants of such knowledge. Therefore, the purpose of this study was to determine the influence of both in-hospital teaching practices as well as socioeconomic status and demographic variables on patients' knowledge of warfarin therapy. SUBJECTS AND METHODS: A telephone survey was conducted among 100 patients 3 to 6 months after mechanical heart valve replacement. A previously validated 20-item questionnaire was used to measure the patient's knowledge of warfarin, its side effects, and vitamin K food sources. Demographic information, socioeconomic status data, and medical education information were also collected. Knowledge scores were compared using the Student t test or one-way analysis of variance. Variables with P < or = .2 on univariate analysis were entered in multiple stepwise regression analysis. RESULTS AND CONCLUSIONS: Sixty-one percent of participants had scores indicative of insufficient knowledge of warfarin therapy (score < or = 80%). Age was negatively related to warfarin knowledge scores (r = 0.27, P = .007). Patients with family incomes greater than $25,000, who had greater than a grade 8 education, and who were employed or self-employed had significantly higher warfarin knowledge scores (P = .007, P = .002, and P = .001, respectively). Gender, ethnicity, and warfarin therapy before surgery were not related to warfarin knowledge scores. Furthermore, none of the in-hospital teaching practices significantly influenced knowledge scores, whereas receiving postdischarge community counseling significantly improved knowledge scores (P = .001). Multivariate regression analysis revealed that understanding the concept of International Normalized Ratio, knowing the acronym, age, and receiving community counseling after discharge were the strongest predictors of warfarin knowledge. Accessing postdischarge counseling resulted in significantly improved warfarin knowledge scores. Because improved knowledge has been associated with improved compliance and control, our findings support the need to develop a comprehensive postdischarge education program or at least to ensure that patients have access to a community counselor to compliment the in-hospital education program.

Anticoagulants↗