Faculty Bibliography

BACKGROUND:During a healthy pregnancy women experience cardiovascular and hemodynamic changes and normal ranges of left ventricular (LV) function on two-dimensional speckle tracking echocardiography (STE) are not well defined. The aim of this study was to describe the cardiovascular changes that occur during the second and third trimesters of a healthy pregnancy using STE. METHODS:Pregnant subjects were enrolled retrospectively if they underwent a transthoracic echocardiography (TTE) between 2011-2014. Subjects with abnormal TTE findings, hypertension, diabetes, preeclampsia, prior cardiac surgery, poor imaging quality or in the 1st trimester were excluded. A total of 74 pregnant subjects were categorized into the 2nd or 3rd trimesters. Twenty-one healthy age-matched females were selected as a control group. RESULTS:The heart undergoes extensive remodeling during pregnancy with increased LV septal thickness, posterior wall thickness, cavity size and mass (p=0.045, p=0.002, p<0.001, p=0.018, respectively). However, myocardial mechanical function measured by: global longitudinal strain, radial strain, circumferential strain, systolic and diastolic global longitudinal strain rate (GLSR), global radial strain rate (GRSR) and global circumferential strain rate, remains preserved. Only time to peak strain rate corrected for heart rate for diastolic GRSR and diastolic GLSR were significantly increased in the third trimester (p=0.016 for both). CONCLUSION/CONCLUSIONS:Despite extensive heart remodeling, many STE derived parameters of LV function in healthy pregnant women remain unchanged and valid for women in the 2nd and 3rd trimester. Future studies investigating early detection of pregnancy related heart disease can refer to these parameters as reference ranges.

Strain and strain rate imaging (also known as deformation imaging) are techniques used to measure myocardial deformation. These newer echocardiographic modalities overcome the limitations of conventional echocardiography and provide a sensitive means of objectively quantifying regional and global myocardial function. It has enabled us to better understand regional myocardial function and risk stratify patients with coronary artery disease, cardiomyopathies and valvular heart disease. Also, they have been used to assess left ventricular dyssynchrony, predict responders and optimize cardiac resynchronization therapy. However, the lack of standardization and inter-vendor variability in measurements are major roadblocks to using deformation imaging in routine clinical practice. This article discusses the fundamental concept of deformation, in particular relating to strain and strain rate imaging using speckle tracking imaging and tissue Doppler imaging, the clinical applications and its prognostic implications.

BACKGROUND:Echocardiography (echo)-quantified LV stroke volume (SV) is widely used to assess systolic performance after acute myocardial infarction (AMI). This study compared 2 common echo approaches - predicated on flow (Doppler) and linear chamber dimensions (Teichholz) - to volumetric SV and global infarct parameters quantified by cardiac magnetic resonance (CMR). METHODS:Multimodality imaging was performed as part of a post-AMI registry. For echo, SV was measured by Doppler and Teichholz methods. Cine-CMR was used for volumetric SV and LVEF quantification, and delayed-enhancement (DE) CMR for infarct size. RESULTS:Overall, 142 patients underwent same day echo and CMR. On echo, mean SV by Teichholz (78 ± 17 mL) was slightly higher than Doppler (75 ± 16 mL; Δ = 3 ± 13 mL; P = 0.02). Compared to SV on CMR (78 ± 18 mL), mean difference by Teichholz (Δ = -0.2 ± 14; P = 0.89) was slightly smaller than Doppler (Δ = -3 ± 14; P = 0.02), but limits of agreement were similar between CMR and echo methods (Teichholz: -28, 27 mL, Doppler: -31, 24 mL). For Teichholz, differences with CMR SV were greatest among patients with anteroseptal or lateral wall hypokinesis (P < 0.05). For Doppler, differences were associated with aortic valve abnormalities or root dilation (P = 0.01). SV by both echo methods decreased stepwise in relation to global LV injury as assessed by CMR-quantified LVEF and infarct size (P < 0.01). CONCLUSIONS:Teichholz and Doppler calculated SV yield similar magnitude of agreement with CMR. Teichholz differences with CMR increase with septal or lateral wall contractile dysfunction, whereas Doppler yields increased offsets in patients with aortic remodeling.

Key requirements for cardiac tissue engineering include the maintenance of cell viability and function and the establishment of a perfusable vascular network in millimeters thick and compact cardiac constructs upon implantation. We investigated if these requirements can be met by providing an intrinsic vascularization stimulus (via sustained action of VEGF secreted at a controlled rate by transduced myoblasts) to a cardiac patch engineered under conditions of effective oxygen supply (via medium flow through channeled elastomeric scaffolds seeded with neonatal cardiomyocytes). We demonstrate that this combined approach resulted in increased viability, vascularization and functionality of the cardiac patch. After implantation in a mouse model of myocardial infarction, VEGF-expressing patches displayed significantly improved engraftment, survival and differentiation of cardiomyocytes, leading to greatly enhanced contractility as compared to controls not expressing VEGF. Controlled VEGF expression also mediated the formation of mature vascular networks, both within the engineered patches and in the underlying ischemic myocardium. We propose that this combined cell-biomaterial approach can be a promising strategy to engineer cardiac patches with intrinsic and extrinsic vascularization potential.