Frequency equation and semi-empirical mechanical coupling strength of microcantilevers in an array.

A characteristic equation for the frequencies of the T-shaped and overhang-shaped cantilevers is derived for the first time. We show that there are optimum values of the overhang lengths and widths that maximize the frequency and the number of maxima is corresponding to the mode number. The frequency of higher-order modes could be tuned by changing the overhang dimensions. Especially, a semi-empirical formula for the coupling strength κ between cantilevers in an array is proposed where the strength presents a cubic decrease with the overhang width ξ and a linear increase with the overhang length η , κ = η / ξ 3 . There is a very good agreement between the proposed formula and the values obtained in recent experiments by other researchers.

Application of machine learning in screening for congenital heart diseases using fetal echocardiography.

There is a growing body of literature supporting the utilization of machine learning (ML) to improve diagnosis and prognosis tools of cardiovascular disease. The current study was to investigate the impact that the ML framework may have on the sensitivity of predicting the presence or absence of congenital heart disease (CHD) using fetal echocardiography. A comprehensive fetal echocardiogram including 2D cardiac chamber quantification, valvar assessments, assessment of great vessel morphology, and Doppler-derived blood flow interrogation was recorded. The postnatal echocardiogram was used to ascertain the diagnosis of CHD. A random forest (RF) algorithm with a nested tenfold cross-validation was used to train models for assessing the presence of CHD. The study population was derived from a database of 3910 singleton fetuses with maternal age of 28.8 ± 5.2 years and gestational age at the time of fetal echocardiography of 22.0 weeks (IQR 21-24). The proportion of CHD was 14.1% for the studied cohort confirmed by post-natal echocardiograms. Our proposed RF-based framework provided a sensitivity of 0.85, a specificity of 0.88, a positive predictive value of 0.55 and a negative predictive value of 0.97 to detect the CHD with the mean of mean ROC curves of 0.94 and the mean of mean PR curves of 0.84. Additionally, six first features, including cardiac axis, peak velocity of blood flow across the pulmonic valve, cardiothoracic ratio, pulmonary valvar annulus diameter, right ventricular end-diastolic diameter, and aortic valvar annulus diameter, are essential features that play crucial roles in adding more predictive values to the model in detecting patients with CHD. ML using RF can provide increased sensitivity in prenatal CHD screening with very good performance. The incorporation of ML algorithms into fetal echocardiography may further standardize the assessment for CHD.

Echocardiographic Reference Ranges of Non-invasive Myocardial Work Indices in Children.

Global myocardial work (GMW) is an emerging method to characterize left ventricle (LV) function with potential advantages over both ejection fraction and global longitudinal strain (GLS). We aimed to determine the feasibility and reproducibility for echocardiographic-derived GMW in a healthy pediatric population; establish normal reference values; and investigate the influence of age, gender, and other clinical factor on normal reference ranges. We prospectively enrolled 212 individuals (median age of 9 years; interquartile range, 6 to 12 years, 112 female). Global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE) were measured from LV pressure-strain loops. Quantification of GMW was performed using a GE Vivid E95 system and available software package (Echopac V.203, GE). The mean LV EF was 64 ± 3% with GLS of -21.3 ± 1.5%. GWI was 1688 ± 219 mmHg% with mean GWE of 96.5 ± 1.4%. The GCW was 1959 ± 207 mmHg%, and the mean GWW of 61.1 ± 30.9 mmHg%. No significant difference was found in MW indices across age group and gender (p > 0.05 for all). There were significant correlations between both GWI and GCW with GLS and systolic blood pressure (p < 0.001), but not with GWE and GWW. Linear regression model revealed that GWI and GCW were more closely correlated with systolic blood pressure than GLS. LV MW indices had good intra-observer and inter-observer reproducibility. This study establishes both the feasibility and reference ranges for non-invasive echocardiographic indices of GMW in healthy children. Myocardial work appears to be a complementary modality to assess LV performance in children.

Contractile Differences Detected by Speckle Tracking Echocardiography in Pediatric Patients with Mitral Valve Prolapse.

Mitral valve prolapse (MVP) is the most common valvar dysfunction in children. There is emerging evidence that MVP is not always a benign entity, hence identification of underlying mechanisms is pertinent to clinical management. Our group previously identified a ventricular contraction abnormality named end-systolic basal eversion (ESBE) in adults that contributed to MVP. The aim of this study was to evaluate regional circumferential strain in pediatric patients with MVP and ESBE compared to normal controls. Left ventricular circumferential strain was assessed in 16 pediatric patients referred for clinical echocardiographic examination with MVP and ESBE (MVP group) and compared to age-gender-matched healthy subjects. ESBE has been previously described as late systolic bileaflet mitral valve prolapse, papillary traction, and concomitant late systolic outward movement of the basal inferior myocardium. The mean age of the MVP group was 13.8 ± 4.6 year and 75% were female. All patients with MVP and controls had qualitatively normal systolic cardiac function. The MVP group had significantly lower regional strain values for 11/16 of the segments including all 6 basal segments. Importantly, the basal inferior (- 17.02 ± 8.32% vs. - 26.10 ± 3.18, p = 0.001) and basal inferolateral (- 19.53 ± 9.76 vs. - 26.10 ± 3.18, p = 0.03) had the lowest strain values compared to the average of all other segments suggesting weaker contraction in the basal inferior segments. Pediatric patients with MVP and ESBE are subject to a similar left ventricular mechanical dysfunction previously described in adults. ESBE was evident by decreased basal circumferential strain values. These findings denoted weaker contraction which is believed to propagate the late systolic outward movement of the basal ventricular myocardium.

Association between carotid intima-media thickness and bone mineral density: a cross-sectional study in Vietnamese men and women aged 50 years and older.

OBJECTIVES: The association between osteoporosis and atherosclerosis remains controversial. We sought to define the relationship between carotid intima-media thickness and bone mineral density (BMD) in individuals of Vietnamese background. DESIGN AND SETTING: Cross-sectional study in Ho Chi Minh City, Vietnam. PARTICIPANTS: The study involved 1460 individuals (559 men) aged 50 years and older (average age 59 years) who were randomly recruited from the community. OUTCOME MEASURES: BMD at the femoral neck and lumbar spine was measured by dual-energy X-ray absorptiometry (Hologic, Waltham, Massachusetts, USA). Carotid intima-media thickness (cIMT) was measured using a Philips Ultrasonography (HD7XE). The presence of atherosclerotic plaque was ascertained for each individual. The association between cIMT and BMD was analysed by a multiple linear regression model. RESULTS: In unadjusted analysis, cIMT was positively associated with femoral neck BMD in men (p=0.005), but not in women (p=0.242). After adjusting for age, smoking, diabetes and hypertension, the association remained statistically significant in men (partial R2=0.005; p=0.015) but not in women (partial R2=0.008; p=0.369). When the analysis was limited to individuals aged 60 years and older, the association between cIMT and BMD was no longer statistically significant. There was no statistically significant association between cIMT and lumbar spine BMD in either men or women. CONCLUSIONS: In Vietnamese individuals aged 50 years and older, there is a clinically non-significant but statistically significant association between carotid intima-media thickness and BMD in men, not in women.

The clinical characteristics of coronary artery fistula anomalies in children and adults: A 24-year experience.

OBJECTIVES: The aim of our work is to investigate the clinical characteristics of coronary artery fistula (CAF) anomalies in South Vietnam. METHODS: This is a retrospective analysis of 119 patients with diagnosis of definite CAF between January 1992 and April 2016. The demographic, clinical, echocardiographic, and angiographic characteristics and management of CAF with short-term outcomes are described. RESULTS: The median age was 15 years (range, 1-79 years), with 49 male (41%) and 70 female (59%). There were 77 symptomatic patients (64.7%) and 91 patients (76.5%) who presented with a murmur. The electrocardiogram was abnormal in 45.4% and cardiac enlargement or increased pulmonary vasculature were seen in 76 patients (63.9%) on chest X-ray. The sensitivity of echocardiography for CAF diagnosis was 79%. The source of the fistula was most often from the RCA (54%), most commonly to right atrium (34.5%) or right ventricle (31.1%). In comparison with surgery, transcatheter closure had a shorter hospital length of stay (5.4 ± 3.8 days vs 12.6 ± 6.5 days, P = .02) and better postprocedural left ventricular ejection fraction (67.9 ± 8.1% vs 62.9 ± 6.0%, P = .03). CONCLUSION: The majority of fistula in this study originated from the RCA and terminated in the right atrium or the right ventricle. Transcatheter and surgical closure are both relatively safe and effective, with the potential for shortened length of hospital stay following transcatheter closure.

Microbiological profile and risk factors for in-hospital mortality of infective endocarditis in tertiary care hospitals of south Vietnam.

OBJECTIVES: We aimed to evaluate the microbiological characteristics and risk factors for mortality of infective endocarditis in two tertiary hospitals in Ho Chi Minh City, south Vietnam. MATERIALS AND METHODS: A retrospective study of 189 patients (120 men, 69 women; mean age 38 ± 18 years) with the diagnosis of probable or definite infective endocarditis (IE) according to the modified Duke Criteria admitted to The Heart Institute or Tam Duc Hospital between January 2005 and December 2014. RESULTS: IE was related to a native valve in 165 patients (87.3%), and prosthetic valve in 24 (12.7%). Of the 189 patients in our series, the culture positive rate was 70.4%. The most common isolated pathogens were Streptococci (75.2%), Staphylococci (9.8%) followed by gram negative organism (4.5%). The sensitivity rate of Streptococci to ampicillin, ceftriaxone or vancomycin was 100%. The rate of methicillin resistant Staphylococcus aureus was 40%. There was a decrease in penicillin sensitivity for Streptococci over three eras: 2005-2007 (100%), 2008-2010 (94%) and 2010-2014 (84%). The in-hospital mortality rate was 6.9%. Logistic regression analysis found prosthetic valve and NYHA grade 3 or 4 heart failure and vegetation size of more than 15 mm as strong predictors of in-hospital mortality. CONCLUSION: Streptococcal species were the major pathogen of IE in the recent years with low rates of antimicrobial resistance. Prosthetic valve involvement, moderate or severe heart failure and vegetation size of more than 15 mm were independent predictors for in-hospital mortality in IE.

Up to nine-years' experience with the Allcarbon prosthetic heart valve.

BACKGROUND AND AIM OF THE STUDY: The Allcarbon tilting disc valve has been used for valve replacement at the present authors' institution since 1993. Herein is reported their experience with Allcarbon valve implantation. METHODS: Between March 1993 and December 1998, Allcarbon valves were implanted in 599 patients (341 males, 258 females; mean age 36.2 years; range: 7-64 years). Among patients, 238 underwent mitral valve replacement (MVR), 217 aortic valve replacement (AVR), and 144 double valve replacement (DVR). The etiology of valve disease was rheumatic in 91% of cases. Follow up was 95.7% complete; cumulative follow up was 3,185 patient-years. RESULTS: Operative mortality was 2.2% (13/599). Actuarial survival at eight years was 96.6 +/- 1.2% after MVR, 96.1 +/- 1.3% after AVR, and 97.9 +/- 1.2% after DVR. Freedom from valve thrombosis at eight years was 97.0 +/- 1.3% after MVR, 100% after AVR, and 90.0 +/- 9.5% after DVR. Freedom from major bleeding at eight years was 90.0 +/- 2.7% after MVR, 93.5 +/- 2.6% after AVR, and 79.7 +/- 7.6% after DVR. There was one embolic episode after MVR. No structural valve failure was observed. Freedom from reoperation on implanted valves at eight years was 96.1 +/- 1.4% after MVR, 97.9 +/- 1.0% after AVR, and 97.9 +/- 1.5% after DVR. On completion of follow up, 91.3% of survivors were in NYHA class I, 8.5% in class II, and 0.2% in class III. CONCLUSION: Among a population of mostly young patients with rheumatic valve disease, the Allcarbon valve showed satisfactory clinical performance when implanted in the mitral and aortic positions.