A. C. Van Rossum

The influence of through-plane motion on left ventricular volumes measured by magnetic resonance imaging: implications for image acquisition and analysis.

In the evaluation of the left ventricular (LV) function using magnetic resonance imaging (MRI), a stack of parallel short-axis (SA) cine images is acquired that covers the whole LV. The aim of this study is to quantify the contribution to the LV volume parameters, provided by the most basal image plane that shows the LV wall only in end diastole (ED) but not in end systole (ES). In 57 healthy volunteers (31 men, mean body surface area 1.87 m2), a complete set of parallel SA images was acquired (10-mm slice distance) by breathhold segmented k-space cine MRI (7 ky lines per beat). The LV end-diastolic volume (EDV), stroke volume (SV), ejection fraction (EF), and cardiac output (CO) were determined by slice summation. Calculations were performed both with and without inclusion of the most basal slice. With inclusion of the most basal slice, all parameters were significantly (p < 0.001) larger compared with the values obtained by excluding this slice. EDV was 134 +/- 29 ml versus 113 +/- 26 ml; SV was 93 +/- 18 ml versus 72 +/- 16 ml; EF was 70 +/- 4% versus 64 +/- 4%; and CO was 5.3 +/- 1.4 l/min versus 4.1 +/- 1.1 l/min. The inclusion of the most basal slice leads to significantly larger values of LV volume parameters. Thus, this most basal SA image slice should be included in calculating the EDV. Whether or not this basal SA slice also contributes to the ES volume should be decided by using anatomical criteria on the ES image. The projection line onto the ES image of a long-axis view provides an additional criterion.

MRI-derived left ventricular function parameters and mass in healthy young adults: Relation with gender and body size

Purpose: To obtain normal values of left ventricular (LV) end-diastolic volume (EDV), stroke volume (SV), cardiac output (CO) and LV mass, in relation to gender, weight (W), length (L) and body surface area (BSA). Methods: Sixty-one healthy volunteers (32 male, 22.4 ± 2.2 years) were examined, weight was 70.9 ± 12.2 kg, length was 1.78 ± 0.09 m, BSA was 1.88 ± 0.19 m2. Segmented k-space breathhold cine MRI was used to obtain a stack of parallel short-axis images, from which LV volumes and end-diastolic mass were derived by slice summation. Four different body size indices were studied: W, L, L2 and BSA. Results: After indexing for L, L2 and BSA, the gender differences in all LV parameters are still persisting. After indexing for W, gender differences persist for EDV and EDM, but are no longer observed for SV and CO. Separate regression analyses for males and females were performed. EDV, SV, CO and EDM correlated significantly with each body size index, both in males and in females. L or BSA were in general better predictors for LV parameters than W. Linear regression equations of EDV (ml) vs. L(m) were for males: EDV = 275 × L − 359 and for females: EDV = 190 × L − 215. Equations of SV(ml) vs. L were for males: SV = 186 × L − 237 and for females: SV = 118 × L − 121. Equations of LV mass(g) vs. L were for males: Mass = 175 × L − 179 and for females: Mass = 65.8 × L − 10.9. Conclusion: Most gender differences in LV parameters remain even after correction for body size indices. Normal reference values for LV parameters are given in relation to body size indices, by calculating regression coefficients separately for males and females. These normal values serve to obtain more accurate reference values for a patient with given gender, weight and length, and thus to improve the differentiation between normal and abnormal LV parameters.

Bone marrow cell therapy after acute myocardial infarction: the HEBE trial in perspective, first results.

AbstractDuring the last decennium, the role of bone marrow mononuclear cells (BMMC) has been underscored in the healing process after acute myocardial infarction (AMI). Although these cells improve left ventricular recovery after AMI in experimental studies, results from large-scale randomised trials investigating BMMC therapy in patients with AMI have shown contradictory results. To address this issue the HEBE study was designed, a multicentre, randomised trial, evaluating the effects of intracoronary infusion of BMMCs and the effects of intracoronary infusion of peripheral blood mononuclear cells after primary percutaneous coronary intervention. The primary endpoint of the HEBE trial is the change in regional myocardial function in dysfunctional segments at four months relative to baseline, based on segmental analysis as measured by magnetic resonance imaging. The results from the HEBE trial will provide detailed information about the effects of intracoronary BMMC therapy on post-infarct left ventricular recovery. In addition, further analysis of the data and material obtained may provide important mechanistic insights into the contribution of BMMCs to natural recovery from AMI as well as the response to cell therapy. This may significantly contribute to the development of improved cell-based therapies, aiming at optimising post-infarct recovery and preventing heart failure. (Neth Heart J 2008;16:436-9.)

Cardiac PET-CT: advanced hybrid imaging for the detection of coronary artery disease.

Hybrid imaging of positron emission tomography (PET) together with computed tomography (CT) is rapidly emerging. In cardiology, this new advanced hybrid imaging modality allows quantification of cardiac perfusion in combination with assessment of coronary anatomy within a single scanning session of less than 45 minutes. The near-simultaneous anatomical evaluation of coronary arteries using CT and corresponding functional status using PET provides a wealth of complementary information in patients who are being evaluated for (suspected) coronary artery disease, and could help guide clinical patient management in a novel manner. Clinical experience gained with this recently introduced advanced hybrid imaging tool, however, is still limited and its implementation into daily clinical practice remains largely unchartered territory. This review discusses principles of perfusion PET, its diagnostic accuracy, and potential clinical applications of cardiac PET-CT in patients with ischaemic heart disease. (Neth Heart J 2010;18:90–8.)

Reduction of infarct size by intravenous injection of uncultured adipose derived stromal cells in a rat model is dependent on the time point of application

Stem cell therapy is a promising tool to improve outcome after acute myocardial infarction (AMI), but needs to be optimized since results from clinical applications remain ambiguous. A potent source of stem cells is the stromal vascular fraction of adipose tissue (SVF), which contains high numbers of adipose derived stem cells (ASC). We hypothesized that: 1) intravenous injection can be used to apply stem cells to the heart. 2) Uncultured SVF cells are easier and safer when cultured ASCs. 3) Transplantation after the acute inflammation period of AMI is favorable over early injection. For this, AMI was induced in rats by 40min of coronary occlusion. One or seven days after AMI, rats were intravenously injected with vehicle, 5×10(6) uncultured rat SVF cells or 1×10(6) rat ASCs. Rats were analyzed 35 days after AMI. Intravenous delivery of both fresh SVF cells and cultured ASCs 7 days after AMI significantly reduced infarct size compared to vehicle. Similar numbers of stem cells were found in the heart, after treatment with fresh SVF cells and cultured ASCs. Importantly, no adverse effects were found after injection of SVF cells. Using cultured ASCs, however, 3 animals had shortness of breath, and one animal died during injection. In contrast to application at 7 days post AMI, injection of SVF cells 1 day post AMI resulted in a small but non-significant infarct reduction (p=0.35). Taken together, intravenous injection of uncultured SVF cells subsequent to the acute inflammation period, is a promising stem cell therapy for AMI.

‘No-reflow’ after acute myocardial infarction: direct visualisation of microvascular obstruction by gadolinium-enhanced CMR

Cardiovascular magnetic resonance is considered the standard imaging modality in clinical trials to monitor patients after acute myocardial infarction. However, limited data are available with respect to infarct size, presence and extent of microvascular injury (MVO) and changes over time, in relation to cardiac function in optimally treated patients. In the current study we prospectively investigate the change of infarct size over time, and the incidence and significance of MVO in a uniform, optimally treated patient group after AMI. (Neth Heart J 2008;16:179-81.)

Magnetic Resonance Imaging of Myocardial Perfusion in Single-Vessel Coronary Artery Disease: Implications for Transmural Assessment of Myocardial Perfusion

The purpose of the study was to investigate the potential of magnetic resonance imaging (MRI) to assess transmural differences in myocardial perfusion. Contrast-enhanced MRI was performed at rest and during hyperemia in a dog model and in 22 patients with single-vessel coronary artery disease. From MR signal intensity-versus-time curves, three perfusion parameters were derived: maximum myocardial contrast enhancement (MCE), slope, and inverse mean transit time (1/MTT). In dogs, MCE correlated well (r = 0.87, p < 0.00001) with microsphere-assessed myocardial blood flow. In the patients, the subendocardial MCE decreased during hyperemia (0.89 +/- 0.18 vs. 0.74 +/- 0.15, p < 0.003) and was lower in subendocardium than in subepicardium (0.74 +/- 0.15 vs. 0.84 +/- 0.21, p < 0.02). Parameters slope and 1/MTT paralleled MCE. Contrast-enhanced MRI reflects the transmural redistribution of myocardial perfusion during hyperemia. Perfusion abnormalities can be identified most distinctly in subendocardial myocardium.

A practical approach to MRI of coronary artery bypass graft patency and flow.

Direct visualization of coronary artery bypass grafts can be obtained non-invasively by magnetic resonance imaging. Several studies demonstrated a high sensitivity and somewhat lower specificity for detection of vein-graft patency, using the conventional spin-echo and gradient-echo techniques. In addition, the true functional status can be assessed by determining the flowrate within the graft using phase velocity mapping. Important limitations of the previously applied techniques include the inability to accurately evaluate the different segments of jump grafts and the presence of graft stenoses. Further improvement is to be expected from the recent introduction of breath-hold imaging sequences and the forthcoming introduction of bloodpool-avid contrast agents.

Magnetic resonance imaging of the heart for determination of ejection fraction

In 28 patients with various cardiac diseases we compared ejection fractions obtained by magnetic resonance imaging in a single oblique slice with monoplane ventriculography in the right anterior oblique projection, the latter serving as the standard. Also, results were evaluated for clinical relevance and relation to image quality. The correlation between the two techniques was moderate (r = 0.65). According to our standardized limits for clinical relevance, insufficiently correlating ejection fractions were obtained in 14 patients. In 8 of these patients this was attributed to poor endocardial edge detection. Edge detection problems were more frequently encountered by imaging with echo-time 20 msec than with echo-time 32 msec. Other causes for mismatching of the obtained ejection fractions are discussed. It is concluded that determination of ejection fraction by single slice magnetic resonance imaging should not be used for clinical application. Improvement can be expected by using a contiguous slicing technique, a longer echo-time in the spin-echo pulse sequence, or in due course by application of newly developed fast-imaging pulse sequences.

Ultrasound and microbubble-targeted delivery of therapeutic compounds: ICIN Report Project 49: Drug and gene delivery through ultrasound and microbubbles

The molecular understanding of diseases has been accelerated in recent years, producing many new potential therapeutic targets. A noninvasive delivery system that can target specific anatomical sites would be a great boost for many therapies, particularly those based on manipulation of gene expression. The use of microbubbles controlled by ultrasound as a method for delivery of drugs or genes to specific tissues is promising. It has been shown by our group and others that ultrasound increases cell membrane permeability and enhances uptake of drugs and genes. One of the important mechanisms is that microbubbles act to focus ultrasound energy by lowering the threshold for ultrasound bioeffects. Therefore, clear understanding of the bioeffects and mechanisms underlying the membrane permeability in the presence of microbubbles and ultrasound is of paramount importance. (Neth Heart J 2009;17:82-6.)