Anthracyclines (AC) are antitumor antibiotics with significant activity against solid and hematologic malignancies. One problem preventing more widespread use has been the development of cardiac toxicity. Experimental evidence supports oxidant stress as an important trigger and/or mediator of AC-induced cardiotoxicity (ACT). Therefore, reducing oxidant stress should be protective against ACT. To determine whether antioxidant protein overexpression can reduce ACT, we developed a cell culture model system using the H9C2 cardiac cell line exhibiting controlled overexpression of the α4-isoform of glutathione- S-transferase (GST). Treatment with the AC doxorubicin (DOX) produced both oncosis, manifested by an increase in the number of cells staining positive for Trypan blue, and apoptosis, indicated by the presence of positive terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. In both cases, the loss of cell viability was preceded by an AC-induced increase in fluorescence with carboxy-2′,7′-dichlorofluorescein diacetate, demonstrating the presence of high levels of reactive oxygen species (ROS). The DOX-induced increase in ROS was reduced to control levels by maximal GST overexpression. Coincident with this elimination of oxidative stress, there was a reduction in both Trypan blue and TUNEL-positive cells, indicating that GST overexpression reduced both ROS and cell death in this model system. We conclude that GST overexpression may be an important part of a protective strategy against ACT and that this model system will aid in defining steps in the pathway(s) leading to AC-induced cell death that can be therapeutically manipulated.

Doppler methods for assessing left ventricular (LV) diastolic function have increased in number and complexity. However, time constraints may prevent measurement of all parameters during routine transthoracic echocardiography. Therefore, we designed a study to determine which Doppler parameters could be most successfully and quickly obtained. The recording success rate and time required to record different LV diastolic function parameters were evaluated in 80 patients. A specific recording protocol was followed by an experienced, credentialed sonographer and time intervals to record each parameter were measured. In comparison with color Doppler M-mode of LV inflow propagation velocities (Vp) and pulmonary venous (PV) flow measurements, transmitral valve (MV) flow and tissue Doppler imaging (TDI) of the mitral annulus had the highest recording success rate and required the shortest time to record. PV flow and Vp took longer to obtain (80.1+/-34.3 sec and 57.1+/-29.1 sec, respectively) than did mitral valve inflow (36.3+/-20.7 sec) and mitral valve annular TDI (29.3+/-18.4 sec for septal and 33.3+/-14.5 sec for lateral). MV flow velocities, Vp, and TDI were successfully recorded in virtually all patients (99-100%). In comparison, the PV flow velocities and durations were successfully recorded less often. The range of success rates for the six PV flow parameters was 49-84%. Since MV flow and TDI also have been shown by us to have the lowest interreader variability, measurement of these two parameters may be preferred for routine clinical evaluation of LV diastolic function in a busy echocardiography laboratory.

Cardiac troponin T (cTnT) levels are widely used to assess for evidence of myocardial infarction. We studied the effect of freezing and long-term storage on the stability of cTnT in blood samples from 178 patients with end-stage renal failure. The serum was separated and divided into multiple aliquots. Baseline cTnT levels were measured in the unfrozen aliquots. The remaining aliquots were frozen using standard techniques. The aliquots were thawed after 3, 6, 12, or 24 months and cTnT levels measured. There were no significant changes in the mean +/- SEM cTnT levels up to 12 months (0.111 +/- 0.098 microg/L) compared with baseline (0.114 +/- 0.098 microg/L); after 24 months, cTnT levels were significantly lower (0.107 +/- 0.095 microg/L) than baseline ( P = .004). The cTnT assay is a reliable method of measuring the cTnT level in human serum up to 12 months of frozen storage. However, after 24 months, the cTnT level was 0.007 microg/L lower than baseline, potentially causing erroneous interpretations. The clinical significance of the change in the cTnT level after long-term frozen storage is unclear. Further studies, including prospective analysis of patient outcomes, should be helpful.