Biomedical Engineering Reference
In-Depth Information
the percentage change in maximum rate of pressure development (d P /d t max )to
differentiate between pacing sites [ 2 ] as opposed to long term outcomes, such as
hospitalization, reverse remodeling, or death.
d P /d t max provides a general metric of cardiac contractility. However, CRT is
known to alter the distribution and variation of regional contraction, stress, work,
and activation time, which may contribute to CRT outcome but may be poorly
represented by d P /d t max . In this study, we evaluate the impact of lead location on
d P /d t max , regional work, stress, contraction, and activation time in a biophysical
patient-specific model.
2 Methods
2.1 Patient Data
All data was obtained from a 60-year-old female with NYHA Class III HF despite
optimal medical treatment. There was significant left ventricular (LV) systolic
dysfunction with an LV ejection fraction of 25%. Mitral regurgitation was trivial.
The surface ECG demonstrated significant conduction disease with LBBB mor-
phology and a QRS duration of 154 ms. Cardiac MRI showed a small area of
subendocardial apical septum scar and severe LV dysfunction.
2.2 Model Development
The model development, fitting, governing equations, and validation have been
described previously [ 3 ]. A brief description is provided here.
2.2.1 Geometry
Cardiac MR imaging was performed using a 1.5 T Philips Achieva system with
32 channel cardiac coil. Data acquired included a 2D short axis cine SSFP
(1.5
10 mm 25 cardiac phases) breath-hold scans covering the ventricles
and 2D short axis and long axis gadolinium late-enhancement (1.5
1.5
10 mm)
breath-hold scans. The model geometry was fitted to the end diastolic short axis
cine MRI. The MRI was manually segmented within CMGUI 1 to create a data
cloud of ~2,000 points characterizing the LV & RV endocardium and the epicar-
dium. A 64 cubic Hermite Element mesh, with eight elements in the circumferential
1.5
1 www.cmiss.org/cmgui
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