[Value of dual-energy computed tomography for detection of left atrial appendage thrombus]

OBJECTIVE

Contrast-enhanced computed tomography (CT) is a convenient method to visualize left atrial appendage (LAA) thrombi. We determined whether diagnostic accuracy improves by including dual-energy as compared to transesophageal echocardiography (TEE). Furthermore, the influence of protocol parameters on radiation dose were quantified.

METHODS

Patients were assigned to the different CT protocols. All CTs were assessed qualitatively for presence of LAA thrombi and dual-energy CT scans quantitatively for iodine concentration. TEE was assessed qualitatively for the presence of thrombi.

RESULTS

Of 32 enrolled patients, 6 had a thrombus in TEE. Qualitative CT assessment yielded 83% sensitivity and 88% specificity. In the 26 patients who underwent dual-energy CT, median iodine concentration was 8.6 mg/cm³ and significantly lower in patients with than without LAA thrombi ; furthermore, it provided value for detecting LAA thrombi (AUC: 0.950 vs 0.867 for combined vs. only qualitative assessment, p = 0.04). The median radiation dose was 1.83 mSv; independently lower in scanning only LAA and with prospective gating , while arrhythmia and dual-energy did not contribute independently.

CONCLUSION

CT provides good diagnostic accuracy for detecting LAA thrombi, which can further be improved if iodine density measurements by dual-energy are incorporated. With an optimized protocol, reasonably low radiation dose can be achieved.

Apoptotic cell death during accelerated rejection in sensitized rat recipients of cardiac allografts

Accelerated rejection due to host sensitization to major histocompatibility complex antigens is a critical problem in clinical organ transplantation in patients who have previously received an organ transplant, experienced acute rejection episodes, received blood transfusions, or been pregnant. The precise pathologic mechanisms underlying accelerated rejection have not been characterized. Herein, we describe apoptosis during T- and B-cell-driven accelerated rejection of cardiac allografts in presensitized recipients. In an established accelerated rejection model, Lewis rats were sensitized to skin grafts from Wistar-Furth rats; after 7 days, they received Wistar-Furth hearts. These grafts were rejected within 24 hours posttransplantation compared with 10 days in nonsensitized recipients (acute rejection, n = 5). Apoptosis was observed during accelerated rejection of cardiac allografts but not in naïve recipients of hearts, as demonstrated at DNA laddering and TUNEL (terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick-end labeling) assay. Apoptosis was discovered as a thus far unknown effector mechanism in accelerated cardiac transplant rejection that accompanies combined cellular and humoral immune alloreactivity. Apoptotic cell death in accelerated rejection and the cascade of upstream and downstream events leading to or resulting from this process should be considered critical steps in the pathogenesis of accelerated rejection.

Beneficial effects of intravenously administered N-3 fatty acids for the prevention of atrial fibrillation after coronary artery bypass surgery: a prospective randomized study

BACKGROUND

Atrial fibrillation (AF) is a common complication after coronary artery bypass grafting operation (CABG). Experimental data have shown antiarrhythmic effects of n-3 polyunsaturated fatty acids (PUFA) on myocardial cells. Orally administered PUFA could significantly reduce the rate of postoperative AF. We assessed the efficacy of PUFA for the prevention of AF after CABG. PUFA were given intravenously to prevent variation in bioavailability.

METHODS AND RESULTS

52 patients were randomized to the interventional group, 50 served as controls. In the control group free fatty acids (100 mg soya oil/kg body weight/day) were infused via perfusion pump, starting on admission to hospital and ending at discharge from intensive care. In the interventional group PUFA were given at a dosage of 100 mg fish oil/kg body weight/day. Primary end point was the postoperative development of AF, documented by surface ECG. Secondary end point was the length of stay in the ICU. The demographic, clinical and surgical characteristics of the patients in the two groups were similar. Postoperative AF occurred in 15 patients (30.6 %) in the control and in 9 (17.3 %) in the PUFA group ( P < 0.05). After CABG, the PUFA patients had to be treated in the ICU for a shorter time than the control patients. No adverse effects were observed.

CONCLUSIONS

Perioperative intravenous infusion of PUFA reduces the incidence of AF after CABG and leads to a shorter stay in the ICU and in hospital. Our data suggest that perioperative intravenous infusion of PUFA should be recommended for patients undergoing CABG.

Which mechanisms are involved in taurine-dependent granulocytic immune response or amino- and α-keto acid homeostasis?

We examined the effects of beta-alanine (taurine analogue and taurine transport antagonist), taurine (regarding its role in neutrophil (PMN) immunonutrition) and taurine combined either with L-NAME (inhibitor of *NO-synthase), SNAP (*NO donor), DON (glutamine-analogue and inhibitor of glutamine-requiring enzymes), DFMO (inhibitor of ornithine-decarboxylase) and beta-alanine on neutrophil amino- and alpha-keto acid profiles or important PMN immune functions in order to establish whether taurine transport-, nitric oxide-, glutamine- or ornithine-dependent mechanisms are involved in any of the taurine-induced effects. According to the present findings, the taurine-mediated effect appears to be based primarily on a modulation of important transmembraneous transport mechanisms and only secondarily on directly or indirectly induced modifications in intragranulocytic amino- and alpha-keto acid homoeostasis or metabolism. Although a direct relation to the parallel observed immunological modifications can only be presumed, these results show very clearly that compositional modifications in the free intragranulocytic amino- and alpha keto-acid pools coinciding with changes in intragranulocytic taurine levels are relevant metabolic determinants that can significantly influence the magnitude and quality of the granulocytic immune response.

Contrast echocardiography: a valid and sensitive imaging method in the investigation of transmyocardial laser-revascularization in an acute ischemia model

In an acute porcine myocardial ischemia model we examined the effect of transmyocardial laser-revascularization (TMLR) on the regional micro perfusion and oxygen supply. In clinical practice, contrast echocardiography is a reliable tool for the measurement of changes in regional blood flow in the ischemic myocardium. We compared contrast echocardiography with the laser Doppler measurement of micro perfusion and with the quantification of regional tissue oxygen tension using a Clark electrode. 22 pigs were randomised in the interventional group and 12 in the control group. Measurements with all three methods were performed before and after occlusion of the first diagonal branch of the left anterior descending coronary artery and, in the interventional group, after TMLR. We investigated not only the effects in the dependent ischemic myocardium, but also in two other myocardial areas, not involved in the coronary occlusion. There was a significant effect of TMLR on regional micro perfusion and local oxygen tension in the dependent ischemic myocardial area. Contrast echocardiography is a successful experimental tool to measure changes in regional myocardial perfusion which cannot be perceived using clinical imaging methods.