Feasibility of the flash-replenishment concept in renal tissue: which parameters affect the assessment of the contrast replenishment?

The purpose of the study was to evaluate whether power pulse inversion (PPI) and pulse inversion (PI) techniques allow the measurement of indices of microcirculatory flow in real-time at low emission power using contrast microbubbles. PPI and PI imaging were performed in a kidney perfusion model during continuous infusion of Definity (0.12 mL/min). At steady state of tissue enhancement, contrast was destroyed by emission of echo bursts at high emission power (MI = 1.3). Consecutively, contrast replenishment was assessed at low emission power (MI = 0.09) in real-time imaging modes (PPI: 12 Hz; PI: 25 Hz). Regions-of-interest (ROI) of variable sizes were placed in the renal cortex and bigger arteries to compare replenishment of macro- and microcirculation. Nonlinear curve fitting was performed using the mathematical model y=s+A(1-e(-betat)), with A as the parameter describing blood volume and beta as a parameter describing the speed of microbubble contrast replenishment. Replenishment curves could be visually appreciated and quantitatively analyzed in all renal segments. A was significantly higher in bigger arteries compared to renal cortex (p < 0.001). beta was found to be significantly higher in the arteries as compared to the cortex (p < 0.001). The SD of beta diminishes with increasing size of the ROI. The acquisition of replenishment curves following ultrasound (US)-induced destruction of contrast microbubbles is feasible at low power using PPI and PI. Assessment of replenishment kinetics allows the differentiation between macro- and microcirculation. Size and position of the ROI have an important impact on the generation of replenishment curves in both imaging modalities, which has to be taken into account.

Do we still need CK-MB in coronary artery bypass grafting surgery?

AIM: The aim of this study was to evaluate the role of cardiac Troponin I (cTnI) and CK-MB for early prediction of outcome of patients undergoing coronary artery bypass grafting (CABG) surgery. METHODS: In 134 consecutive patients undergoing CABG-surgery blood samples were analyzed for cTnI concentration and CK-MB activity. ECG, hemodynamic parameters and the need for inotropic support, were continuously registered. Patients were divided into group A (uneventful course), group B (ischemia by ECG, hemodynamic stability) and group C (ischemia by ECG and IABP). RESULTS: After removal of X-clamp an increase cTnI and CK-MB was observed in all patients. Five hrs after stop of CPB group A (8.3+/-4.2 microg/L) had lower cTnI values compared to group B (14.8+/-5.3 microg/L) (p=0.035) and C (54+/-22.8 microg/L) (p=0.023). The cut off value was 14.8 microg/L. Sensitivity and specificity (99%/97%) was higher for cTnI than for CK-MB (90%/30%). The positive predictive value of outcome was better for cTnI (86%) than for CK-MB (33%). CONCLUSION: CTnI is a specific and sensitive marker for evaluation of perioperative myocardial ischemia (PMI). Additional determination of CK-MB activity does not provide further clinical information. CTnI should be the marker of first choice in CABG surgery.

Consumer perception of beneficial effects of probiotics for human health.

The purpose of this study was to evaluate the knowledge, perception and buying behaviour of probiotics. 72 participants in Middelburg, the Netherlands, filled out a detailed questionnaire regarding probiotics and their customer and consumer behaviour. It can be concluded from this study that the concept of probiotics is generally poorly understood. Health-conscious consumers seem to be the group most aware of the correct meaning of the term probiotics. Almost 50% of the participants did not believe that probiotics had any health effect. Independent organisations and/or government agencies appeared to be the preferred source of information on the functionality of probiotics.

Direct aortic cannulation in minimally invasive mitral-valve operations.

The minimally invasive Port-Access (Heartport, Redwood City, CA) approach in mitral-valve operations originally required femoral arterial cannulation, which is considered a disadvantage, especially in patients with peripheral vessel disease. In this study 20 patients were prospectively randomized into 2 groups, to undergo either standard femoral (group A) or direct aortic cannulation (group B). Pre- and postoperative data as well as markers for myocardial damage were assessed. Postoperatively, patients of group B showed lower levels of damage, indicating that direct aortic cannulation might provide better myocardial protection. Furthermore, the direct aortic cannulation technique may eliminate complications associated with the standard femoral artery cannulation.

Are microbubbles free flowing tracers through the Myocardium? Comparison of indicator-dilution curves obtained from dye dilution and echo contrast using harmonic power Doppler imaging.

BACKGROUND: Harmonic power Doppler imaging (H-PDI) has been introduced into the field of contrast echocardiography as a contrast-specific imaging modality. However, there has been considerable skepticism as to whether H-PDI would be quantifiable, because it depends on the destruction of microbubbles and has more complex signal processing than gray scale imaging. The aim of the present study was to evaluate the relationship between the concentration of microbubbles and the resulting H-PDI signals even under conditions where bubble destruction is most likely. Furthermore, we evaluated whether microbubbles of Levovist freely pass the microcirculation, which is a prerequisite for the assessment of myocardial blood flow. METHODS AND RESULTS: A strong positive correlation was found between the H-PDI signals and the amount of microbubbles up to the onset of acoustic shadowing (r = 0. 968, P<0.001). Time-intensity curves for H-PDI of air-filled microbubbles were compared with time-concentration curves of indocyanine green (ICG) in both a flow phantom and a working heart setup. The mean transit times (MTTs) through the myocardium of both agents were compared after a bolus injection into the left coronary artery. A close correlation was observed between 1/MTT and flow in both setups (r>0.98, P<0.0001). However, at high flow rates, the MTTs of the microbubbles were slightly, albeit not significantly, faster than those of indocyanine green. CONCLUSIONS: We conclude that microbubbles fulfill the prerequisites of free flowing tracers through the myocardium. Furthermore, H-PDI technology allows a reliable assessment of time-concentration curves of air-filled microbubbles up to the onset of acoustic shadowing.

Subendocardial steal effect seen with real-time perfusion imaging at low emission power during adenosine stress: replenishment M-mode processing allows visualization of vertical steal.

We present a patient in whom power pulse inversion imaging clearly demonstrated a subendocardial myocardial perfusion defect during contrast vasodilator stress using adenosine. The defect was best appreciated with M-mode postprocessing of power pulse inversion imaging data.