Computational medical imaging and hemodynamics framework for functional analysis and assessment of cardiovascular structures.

Cardiac dysfunction constitutes common cardiovascular health issues in the society, and has been an investigation topic of strong focus by researchers in the medical imaging community. Diagnostic modalities based on echocardiography, magnetic resonance imaging, chest radiography and computed tomography are common techniques that provide cardiovascular structural information to diagnose heart defects. However, functional information of cardiovascular flow, which can in fact be used to support the diagnosis of many cardiovascular diseases with a myriad of hemodynamics performance indicators, remains unexplored to its full potential. Some of these indicators constitute important cardiac functional parameters affecting the cardiovascular abnormalities. With the advancement of computer technology that facilitates high speed computational fluid dynamics, the realization of a support diagnostic platform of hemodynamics quantification and analysis can be achieved. This article reviews the state-of-the-art medical imaging and high fidelity multi-physics computational analyses that together enable reconstruction of cardiovascular structures and hemodynamic flow patterns within them, such as of the left ventricle (LV) and carotid bifurcations. The combined medical imaging and hemodynamic analysis enables us to study the mechanisms of cardiovascular disease-causing dysfunctions, such as how (1) cardiomyopathy causes left ventricular remodeling and loss of contractility leading to heart failure, and (2) modeling of LV construction and simulation of intra-LV hemodynamics can enable us to determine the optimum procedure of surgical ventriculation to restore its contractility and health This combined medical imaging and hemodynamics framework can potentially extend medical knowledge of cardiovascular defects and associated hemodynamic behavior and their surgical restoration, by means of an integrated medical image diagnostics and hemodynamic performance analysis framework.

Left ventricular diastolic function assessment using time differences between mitral annular velocities and transmitral inflow velocities in patients with heart failure.

BACKGROUND: Evaluation of left ventricular (LV) diastolic function is important in clinical echocardiography. The relationship between mitral annular velocities and transmitral inflow velocities provide additional information about LV filling and diastolic function. This study evaluates the relationships of time intervals between peaks E of mitral inflow velocities and E' of mitral annular velocities, and peaks A and A' in patients with heart failure (HF). METHODS: Eighty patients with HF and 50 age- and gender-matched normal healthy subjects were prospectively recruited and underwent full echocardiograms. The following time intervals were measured: (1) from the onset of R-wave on the ECG to the peak of E-wave on the transmitral flow (TMF) (R-pE); (2) from R to peak of E'-wave on the LV lateral wall of tissue Doppler imaging (TDI) (R-pE'); (3) from onset of P-wave to peak of A-wave on the TMF (P-pA); and (4) from onset of P-wave to peak of A'-wave (P-pA') of TDI. Early-diastolic temporal discordance (EDTD) and late-diastolic temporal discordance (LDTD) were calculated as the difference between the time intervals (R-E) and (R-E'), (P-pA) and (P-p A'). RESULTS: EDTD significantly decreased in patients with HF compared with normal subjects (18.0±54.1ms vs. 28.0±33.5ms, P<0.05). There was also a significant decrease in LDTD in HF patients compared with normal subjects (19.6±23.5ms vs. 34.8±20.6; P<0.05). CONCLUSIONS: EDTD and LDTD decreased in patients with heart failure, and they may be useful tools in identifying abnormal LV relaxation and left atrial contraction for LV diastolic function.

Assessment of left ventricular preload by cardiac magnetic resonance imaging predicts exercise capacity in adult operated tetralogy of Fallot: a retrospective study.

BACKGROUND: The optimal timing of pulmonary homograft valve replacement (PVR) is uncertain. Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) are often used to guide the clinical decision for PVR in operated tetralogy of Fallot (TOF) patients with significant pulmonary regurgitation (PR). We aim to study the relationship between exercise capacity and CMR in these patients. METHODS: The study is a single-centre retrospective analysis of 36 operated TOF patients [median 21.4 (interquartile range 16.4, 26.4) years post-repair; 30 NYHA I, 6 NYHA II; median age 25.2 (interquartile range 19.5-31.7) years, 29 males] with significant PR on CMR who underwent CPET within 15 [median 2.0 (interquartile range 0.8-7.2)] months from CMR. CPET parameters were compared with 30 age- and sex-matched healthy controls [median age 27.8 (interquartile range 21.0-32.8) years; 24 males]. RESULTS: Peak systolic blood pressure (177 versus 192 mmHg, p = 0.007), Mets (7.3 versus 9.9, p < 0.001), peak oxygen consumption (VO2max) (29.2 versus 34.5 ml/kg/min, p < 0.001) and peak oxygen pulse (11.0 versus 13.7 ml/beat, p = 0.003) were significantly lower in TOF group versus control. Univariate analyses showed negative correlation between PR fraction and anaerobic threshold. There was a positive correlation between indexed left (LV) and right (RV) ventricular end-diastolic volumes, as well as indexed LV and effective RV stroke volumes, on CMR and VO2max and Mets achieved on CPET. These remained significant after adjustment for age and sex. CONCLUSIONS: TOF subjects have near normal exercise capacity but significantly lower Mets, VO2max and peak oygen pulse achieved compared to controls. Increased PR fraction in TOF subjects was associated with lower anaerobic threshold. Higher indexed effective RV stroke volume, a measure of LV preload, was associated with higher VO2max and Mets achieved, and may potentially be used as a predictor of exercise capacity.

Regional assessment of left ventricular surface shape from magnetic resonance imaging.

Left ventricular functional abnormalities are postulated to be associated with regional modification of surface curvature. This study describes the computation of the differential properties of the LV surface via an analytic approach using local surface fitting. Quantification was implemented with cine magnetic resonance imaging (MRI), which was used as the source to derive 3D wire-frame models and the related shape descriptors. Based on these shape descriptors, the shape of LV could be represented in both static and dynamic manners. These may have implications for diverse cardiac diseases.