Speckle-Tracking Echocardiography for Monitoring Acute Rejection in Transplanted Heart.

BACKGROUND: The diagnosis of acute cellular rejection (ACR) is a major objective in the management of heart transplant recipients. The aim of this study was to assess the utility of speckle-tracking derived parameters in identifying patients at risk of graft rejection. METHODS: A prospective, single-center study was carried out involving 45 consecutive heart transplant patients who underwent a total of 220 routine endomyocardial biopsies (EMBs) with correlative echocardiographic examination. RESULTS: No significant ACR (grade 0-1R) was seen in 190 biopsies (81.2% of the ACR-free group), and moderate ACR requiring specific treatment (grade 2R) was detected in 30 biopsies (13.6% of the ACR group). Grade 3R was not observed. All longitudinal left ventricular (LV) and right ventricular (RV) strain parameters were greater in the ACR-free group than in patients with ACR, while no differences were observed between radial and circumferential strain parameters. In our analysis, we selected RV free wall longitudinal strain (RV FW) ≤ 16.8% and 4-chamber longitudinal strain (4CH LS) ≤ 13.8%, which related to the presence of ACR requiring treatment. We assigned 1 point for each parameter (minimum 0, maximum 2 points) and derived a new echocardiographic index, the Strain Rejection Score (SRS). Our proposed approach-a combination of the 2 abovementioned indices-for screening patients at risk of ACR ≥ 2R, when expressed by a score 2 points, showed good specificity, strong negative predictive value, and the highest area under the curve. CONCLUSIONS: Our study demonstrated that combination of 4CH LS and RV FW as a new echocardiographic index, the Strain Rejection Score, can be useful as a noninvasive assessment of ACR during the first year of follow-up after heart transplant.

Distribution of DNA fragment sizes after irradiation with ions.

Ionizing radiation is responsible for production of double-strand breaks (DSBs) in a DNA structure. In contrast to sparsely ionizing radiation, densely ionizing radiation produces DSBs that are non-randomly distributed along the DNA molecule and can form clusters of various size. The paper discusses minimalistic models that describe observable patterns of fragment length in DNA segments irradiated with heavy ions and applies the formalism to interpret the recent experimental data collected by use of atomic force microscope (AFM).

Distribution of double-strand breaks induced by ionizing radiation at the level of single DNA molecules examined by atomic force microscopy.

Double-strand breaks (DSBs) are the most critical radiation-induced lesions, because they result in the fragmentation of the DNA molecule and because a single unrepaired DSB may lead to cell death. We present the results of radiation-induced fragmentation of plasmid DNA analyzed by atomic force microscopy (AFM) to allow the visualization of individual DNA molecules. Linear PhiX174 plasmid DNA was exposed to a wide range of doses of low-LET X rays and high-LET carbon, nickel and uranium ions. The induced DNA fragments were detected and measured based on the recorded AFM images and fragment length distributions were derived for each radiation type and dose. The results show a dose- and radiation type-dependent DNA fragmentation with a significantly larger fraction of short fragments produced by high-LET radiation compared to X rays. This can be considered as experimental evidence of DSB clustering due to inhomogeneous energy deposition at the level of the plasmid DNA molecule. Additionally, the experimentally derived fragment profiles were compared and found to be in agreement with the prediction of a model simulating the fragmentation of DNA molecules induced by radiation.