Hyung Kwan Kim

Normal Echocardiographic Measurements in a Korean Population Study: Part I. Cardiac Chamber and Great Artery Evaluation

Background Measurement of the cardiac chamber is essential, and current guidelines recommend measuring and reporting values for both sides of the cardiac chamber during echocardiographic evaluation. Normal echocardiographic reference values have been suggested previously, but detailed information about right-sided chambers and values according to gender was not included. Methods This is a prospective multicenter (23 centers) study evaluating normal Korean adult subjects using comprehensive echocardiography. We included normal adult subjects (age; 20-79 years old) who had no significant cardiac disorders or illnesses, such as hypertension or diabetes, which could affect cardiac structure and function. We measured the cardiac chamber including both right and left ventricles as well as atria according to current echocardiography guidelines and compared values according to gender and age groups. Results A total of 1003 subjects were evaluated and the mean age was 48 ± 16 years. Left ventricular (LV) dimensions increased, but LV volume decreased in older subjects. Right ventricular (RV) area decreased in women and older subjects, and the RV long-axis dimension showed a similar trend. Left atrial (LA) volume increased in men but there were no differences in LA volume index between men and women. The dimension of great arteries increased in men and older subjects. Conclusion Since there were considerable differences between men and women and in the different age groups, and the trends differed significantly between different echo variables, normal echocardiographic cutoff values should be differentially applied based on age and gender.

B-Type Natriuretic Peptide in Isolated Severe Tricuspid Regurgitation: Determinants and Impact on Outcome

Background The plasma B-type natriuretic peptide (BNP) level is a useful prognostic marker in heart failure and valvular heart disease. In patients with isolated severe tricuspid regurgitation (TR), little is known about the determinants of plasma BNP levels and the correlation with future outcome. The purpose of this study was to identify the determinants of plasma BNP levels in patients with isolated severe TR and the value of the BNP level in predicting postoperative outcomes after corrective surgery. Methods We prospectively enrolled 39 patients with isolated, severe TR undergoing corrective surgery. A plasma BNP assay and cardiac magnetic resonance (CMR) imaging were performed before surgery. The combined end-point was the occurrence of cardiac death or readmission due to heart failure. Results Linear regression analysis showed that the left ventricular ejection fraction and right ventricular end systolic volume were the most important determinants of the BNP levels (p = 0.002, R2 = 0.315). Based on the receiver operating characteristics (ROC) curve, we were able to derive an optimal cutoff value (200 pg/mL) to predict postoperative cardiac death with a sensitivity of 80% and a specificity of 85%. The one-year survival rate was 96% in patients with a BNP < 200 pg/mL and 53% in patients with a BNP ≥ 200 pg/dL (p = 0.001). Conclusion An elevation in the BNP level is determined by the functional status of the right and left ventricles in patients with isolated, severe TR. An elevated BNP predicts adverse events after corrective surgery. Therefore, the BNP level should be included in the clinical evaluation and risk stratification of patients with isolated TR.

Normal 2-Dimensional Strain Values of the Left Ventricle: A Substudy of the Normal Echocardiographic Measurements in Korean Population Study

Background It is important to understand the distribution of 2-dimensional strain values in normal population. We performed a multicenter trial to measure normal echocardiographic values in the Korean population. Methods This was a substudy of the Normal echOcardiogRaphic Measurements in KoreAn popuLation (NORMAL) study. Echocardiographic specialists measured frequently used echocardiographic indices in healthy people according to a standardized method at 23 different university hospitals. The strain values were analyzed from digitally stored images. Results Of a total of 1003 healthy participants in NORMAL study, 2-dimensional strain values were measured in 501 subjects (265 females, mean age 47 ± 15 years old) with echocardiographic images only by GE echocardiographic machines. Interventricular septal thickness, left ventricular (LV) posterior wall thickness, systolic and diastolic LV dimensions, and LV ejection fraction were 7.5 ± 1.0 mm, 7.4 ± 1.0 mm, 29.9 ± 2.8 mm, 48.9 ± 3.6 mm, and 62 ± 4%, respectively. LV longitudinal systolic strain (LS) values of apical 4-chamber (A4C) view, apical 3-chamber (A3C) view, apical 2-chamber (A2C) view, and LV global LS (LVGLS) were −20.1 ± 2.3, −19.9 ± 2.7, −21.2 ± 2.6, and −20.4 ± 2.2%, respectively. LV longitudinal systolic strain rate (LVLSR) values of the A4C view, A3C view, A2C view, and LV global LSR (LVGLSR) were −1.18 ± 0.18, −1.20 ± 0.21, −1.25 ± 0.21, and −1.21 ± 0.21−s, respectively. Females had lower LVGLS (−21.2 ± 2.2% vs. −19.5 ± 1.9%, p < 0.001) and LVGLSR (−1.25 ± 0.18−s vs. −1.17 ± 0.15−s, p < 0.001) values than males. Conclusion We measured LV longitudinal strain and strain rate values in the normal Korean population. Since considerable gender differences were observed, normal echocardiographic cutoff values should be differentially applied based on sex.

Normal Ranges and Physiological Changes of Midwall Fractional Shortening in Healthy Korean Population

Background and Objectives Left ventricular (LV) midwall fractional shortening (FSmw) reflects systolic function more accurately than LV endocardial fractional shortening (eFS) in patients with increased LV wall thickness. Although the normal reference ranges of LV-FSmw have been suggested in Western population studies, its reference values and age-related physiological changes in Eastern populations remain unknown. Subjects and Methods Conventional echocardiographic parameters, LV-FSmw, and stress-corrected LV-FSmw were assessed in 160 healthy and clinically normal subjects with a mean age of 45 (range, 11-72 years; 104 males, 56 women), all of whom were confirmed to be free of disease, based on laboratory investigations, clinical and physical examination findings and computed tomographic coronary angiographic examinations. Results LV-FSmw was higher in women compared to men. However, the differences were without statistical significance (18.2±1.5% for male gender and 19.4±2.5% for female gender, p=0.07). In contrast to LV-eFS that progressively increased with age (p=0.001), LV-FSmw and stress-corrected LV-FSmw was not influenced by changes in age (p=0.88 and 0.29, respectively). The results remained unchanged when analyses were performed adjusting for gender. Conclusion The results of this study provide normal reference values for LV-FSmw and stress-corrected LV-FSmw and their natural physiological changes with advancing age. These measures can be used as reference standards for research on LV systolic function in the setting of pressure or volume overload.

Normal Echocardiographic Measurements in a Korean Population Study: Part II. Doppler and Tissue Doppler Imaging

Background Hemodynamic and functional evaluation with Doppler and tissue Doppler study as a part of comprehensive echocardiography is essential but normal reference values have never been reported from Korean normal population especially according to age and sex. Methods Using Normal echOcaRdiographic Measurements in a KoreAn popuLation study subjects, we obtained normal reference values for Doppler and tissue Doppler echocardiography including tricuspid annular velocities according to current guidelines and compared values according to gender and age groups. Results Mitral early diastolic (E) and late diastolic (A) velocity as well as E/A ratio were significantly higher in women compared to those in men. Conversely, mitral peak systolic and late diastolic annular velocity in both septal and lateral mitral annulus were significantly lower in women compared to those in men. However, there were no significant differences in both septal and lateral mitral early diastolic annular (e) velocity between men and women. In both men and women, mitral E velocity and its deceleration time as well as both E/A and E/e ratio considerably increased with age. There were no significant differences in tricuspid inflow velocities and tricuspid lateral annular velocities between men and women except e velocity, which was significantly higher in women compared to that in men. However, changes in both tricuspid inflow and lateral annular velocities according to age were similar to those in mitral velocities. Conclusion Since there were significant differences in Doppler and tissue Doppler echocardiographic variables between men and women and changes according to age were even more considerable in both gender groups, normal Doppler echocardiographic values should be differentially applied based on age and sex.

Prognostic Value of Renal Function for Cardiac Events in Patients Without Significant Stenosis on Coronary Computed Tomography Angiography

This study was conducted to determine clinical parameters predicting future major adverse cardiovascular events (MACEs) in patients without significant stenosis on coronary computed tomographic angiography (CCTA). A total of 625 patients with suspected coronary artery disease (CAD) who underwent CCTA that revealed insignificant (< 50%) CAD was reviewed in three cardiac centers. The MACEs including cardiac death, non-fatal myocardial infarction (MI), unstable angina and late (> 90 days after CCTA) revascularization were assessed. During the mean follow-up period of 819 ± 529 days (median 837 days), there were 28 cases of MACEs (4.5%). In multivariable Cox regression analysis, independent predictors for MACEs were male sex (hazard ratio [HR], 2.40; 95% confidence interval [CI], 1.01-5.69; P = 0.046) and low estimated creatinine clearance (eCCr) (< 60 mL/min/1.73 m2) (HR, 3.07; 95% CI, 1.22-7.74; P = 0.017). Low eCCr was the only independent predictor for hard events including cardiac death and MI (HR, 17.6, 95% CI, 1.44-215.7; P = 0.025). In conclusion, renal function is an independent predictor for cardiovascular events among patients without significant CAD by CCTA. Careful monitoring and preventive strategy are warranted in patients with impaired renal function even without significant CAD. Graphical Abstract