Ru San Tan

Left ventricular regional wall curvedness and wall stress in patients with ischemic dilated cardiomyopathy

Geometric remodeling of the left ventricle (LV) after myocardial infarction is associated with changes in myocardial wall stress. The objective of this study was to determine the regional curvatures and wall stress based on three-dimensional (3-D) reconstructions of the LV using MRI. Ten patients with ischemic dilated cardiomyopathy (IDCM) and 10 normal subjects underwent MRI scan. The IDCM patients also underwent delayed gadolinium-enhancement imaging to delineate the extent of myocardial infarct. Regional curvedness, local radii of curvature, and wall thickness were calculated. The percent curvedness change between end diastole and end systole was also calculated. In normal heart, a short- and long-axis two-dimensional analysis showed a 41 +/- 11% and 45 +/- 12% increase of the mean of peak systolic wall stress between basal and apical sections, respectively. However, 3-D analysis showed no significant difference in peak systolic wall stress from basal and apical sections (P = 0.298, ANOVA). LV shape differed between IDCM patients and normal subjects in several ways: LV shape was more spherical (sphericity index = 0.62 +/- 0.08 vs. 0.52 +/- 0.06, P < 0.05), curvedness at end diastole (mean for 16 segments = 0.034 +/- 0.0056 vs. 0.040 +/- 0.0071 mm(-1), P < 0.001) and end systole (mean for 16 segments = 0.037 +/- 0.0068 vs. 0.067 +/- 0.020 mm(-1), P < 0.001) was affected by infarction, and peak systolic wall stress was significantly increased at each segment in IDCM patients. The 3-D quantification of regional wall stress by cardiac MRI provides more precise evaluation of cardiac mechanics. Identification of regional curvedness and wall stresses helps delineate the mechanisms of LV remodeling in IDCM and may help guide therapeutic LV restoration.

Lipid Goal Attainment and Prescription Behavior in Asian Patients with Acute Coronary Syndromes: Experience from a Tertiary Hospital:

Lipid goal attainment studies in Asian patients with acute coronary syndrome (ACS) are limited. The objectives of this study were to determine low-density lipoprotein cholesterol (LDL-C) goal attainment rate at 4 months, and to examine prescription behavior influencing lipid goal attainment in Asian patients with ACS. A retrospective analysis of 267 patients with ACS was performed. The mean follow-up duration was 41.2 ± 10.7 months. LDL-C goal attainment rate was highest at 4 months (36.7%) but declined progressively throughout follow-up. More than 85% of patients were discharged with equipotent statin dose of 2 (equivalent to simvastatin 20 mg) or less. In patients who did not attain LDL-C goals, the statin dose remained low throughout follow-up because of a lack in responsive dose titration. Aggressive lipid-lowering therapy should be initiated early to improve goal attainment in these high-risk patients.

Cardiac Myocardial Disease States Cause Left Ventricular Remodeling with Decreased Contractility and Lead to Heart Failure;Interventions by Coronary Arterial Bypass Grafting and Surgical Ventricular Restoration Can Reverse LV Remodeling with Improved Cont

Dhanjoo N. Ghista1, Liang Zhong2, Leok Poh Chua3, Ghassan S. Kassab4, Yi Su5 and Ru San Tan2 1Department of Graduate and Continuing Education, Framingham State University, Framingham, Massachusetts, 2Department of Cardiology, National Heart Centre, 3School of Mechanical and Aerospace Engineering, Nanyang Technological University, 4Departments of Biomedical Engineering, Surgery, Cellular and Integrative Physiology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, 5Institute of High Performance Computing, Agency for Science, Technology and Research, 1,4USA 2,3,5Singapore

Noninvasive Assessment of Left Ventricular Remodeling: Geometry, Wall Stress, and Function

Left ventricular (LV) remodeling after myocardial infarction (MI) plays an important role in the progression of heart failure (HF). Changes in the shape, size, and function of the LV are caused by altered mechanical properties of the injured myocardium. As the survival rate after MI improves with medical advances, the incidence of HF patients increases. Hence, an accurate depiction of the LV remodeling process facilitates disease surveillance and monitoring of therapeutic efficacy. It may also help determine the choice of treatment, e.g., surgery to remove the infarcted wall segment and reduce the LV cavity size. Traditionally, there are several ways of characterizing LV remodeling: changes in LV diameter, LV volume, ejection fraction, and qualitative or semi-quantitative descriptors of LV shape. In this chapter, we present a new approach to quantify LV shape (in terms of curvedness), wall stress, and function by using computational modeling.