Regional Diastolic and Systolic Function by Strain Rate Imaging for the Detection of Intramural Viability during Dobutamine Stress Echocardiography in a Porcine Model of Myocardial Infarction

Challenging cardiac function post-spinal cord injury with dobutamine

There is general consensus that spinal cord injuries (SCI) above T6 result in altered sympathetic control of the heart, which negatively influences cardiac structure and function. To by-pass disrupted circuitry and investigate cardiac responses under enhanced sympathetic activity we utilized dobutamine (DOB) stress echocardiography. Animals were divided into a T2, 25g-cm contusive SCI (SCI) or an uninjured control (CON) group. Echocardiography was performed pre-SCI and at 1, 2 and 6weeks post-SCI. Increasing doses of DOB (5, 10 & 20μg/min/kg) were infused intravenously pre-SCI and at 1 and 6weeks post-SCI. Parasternal-short axis images were used to compare group differences in systolic function and track changes in response to SCI and DOB over time. One week post-SCI, stroke volume (SV), end diastolic volume (EDV), cardiac output (CO) and ejection fraction (EF) were all reduced compared to CON and these deficits persisted to 6weeks. We also found an increase in collagen deposition at 6weeks post SCI. Pre-SCI, DOB elicited a decrease in EDV and increases in CO, EF and HR but not SV. At 6weeks following SCI, in addition to increases in CO, EF and HR, DOB also induced increases in SV. This is the first report, to our knowledge, of DOB responses in a contusive SCI model with persistent cardiac impairments. The return of CO to pre-SCI levels and the substantial increase in SV at low DOB dosages shows that impaired descending control of the heart is directly contributing to reduced resting SV after SCI.

A Comparison of Hyperelastic Warping of PET Images with Tagged MRI for the Analysis of Cardiac Deformation

The objectives of the following research were to evaluate the utility of a deformable image registration technique known as hyperelastic warping for the measurement of local strains in the left ventricle through the analysis of clinical, gated PET image datasets. Two normal human male subjects were sequentially imaged with PET and tagged MRI imaging. Strain predictions were made for systolic contraction using warping analyses of the PET images and HARP based strain analyses of the MRI images. Coefficient of determination R (2) values were computed for the comparison of circumferential and radial strain predictions produced by each methodology. There was good correspondence between the methodologies, with R (2) values of 0.78 for the radial strains of both hearts and from an R (2) = 0.81 and R (2) = 0.83 for the circumferential strains. The strain predictions were not statistically different (P ≤ 0.01). A series of sensitivity results indicated that the methodology was relatively insensitive to alterations in image intensity, random image noise, and alterations in fiber structure. This study demonstrated that warping was able to provide strain predictions of systolic contraction of the LV consistent with those provided by tagged MRI Warping.

Predictive value of left ventricular remodeling by area strain based on three-dimensional wall-motion tracking after PCI in patients with recent NSTEMI

We aimed to explore whether a novel left ventricular performance index, area strain (AS), based on three-dimensional wall-motion tracking (3-D-WMT) done before and after percutaneous coronary intervention (PCI) could predict left ventricular (LV) remodeling in patients with recent non-ST elevation myocardial infarction (NSTEMI). Sixty-one patients (53.6 ± 8.8 years) with recent NSTEMI were enrolled. Coronary angiography and PCI were undertaken for reperfusion. Parameters of myocardial deformation (including LV end-diastolic volume, LV end-systolic volume, LV ejection fraction, LV global and regional peak area strain) were measured by 3-D-WMT before and 1 week after reperfusion therapy. Six months after reperfusion, LV negative remodeling was defined as lack of improvement in LV function, with increase in LV end-diastolic volume ≥15%. Patients were subdivided into remodeled group (n = 25) and non-remodeled group (n = 36) at follow-up. Patients with negative LV remodeling had significantly higher cardiac troponin I (cTnI) levels at baseline (21.21 ± 12.22 vs. 15.56 ± 8.91 ng/mL; p = 0.0357), higher B-type natriuretic peptide (BNP) level (247.56 ± 177.39 vs. 170.53 ± 97.89 pg/mL; p = 0.0336) and reduced global AS (-27.9 ± 4.6% vs. -31.9 ± 4.3%; p = 0.001) than those without remodeling. Global AS at baseline had a significantly close correlation with cTnI level 36 h after MI (r = 0.71, p < 0.001). Moreover, a weak relationship was found between LV global AS at baseline and BNP level 24 h after myocardial infarction (r = 0.423, p < 0.001). By multivariate logistic regression analysis, lack of improvement of global AS 1 week after PCI was found to be a powerful independent predictor of negative LV remodeling at follow-up (OR = 1.41, 95% CI 1.28-3.27, p = 0.003). In particular, a global AS ≤32% (absolute value) showed a sensitivity and a specificity of 86.1% and 68.0% in predicting negative LV remodeling. These data suggest that AS could be used to assess myocardial global and regional LV function with good feasibility and repeatability. Global AS 1 week after PCI is a good independent predictor of negative LV remodeling after 6-month follow-up.