Trends in door-to-balloon time and mortality in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention.

BACKGROUND: In patients with acute ST-elevation myocardial infarction (STEMI) who are undergoing percutaneous coronary intervention, current guidelines for reperfusion therapy recommend a door-to-balloon (DTB) time of less than 90 minutes. Considerable effort has focused on reducing DTB time with the assumption that a reduction in DTB time translates into a significant reduction in mortality; however, the clinical impact of this effort has not been evaluated. Therefore, our objective was to determine whether a decline in DTB time in patients with STEMI was associated with an improvement in clinical outcomes. METHODS: We assessed the yearly trend in DTB time for 8771 patients with STEMI who were undergoing primary percutaneous coronary intervention from 2003 to 2008 as part of the Blue Cross Blue Shield of Michigan Cardiovascular Consortium and correlated it with trends in in-hospital mortality. Patients were stratified according to risk of death using a mortality model to evaluate whether patient risk factors affect the relationship between DTB time and mortality. RESULTS: Median DTB time decreased each year from 113 minutes in 2003 to 76 minutes in 2008 (P < .001), and the percentage of patients who were revascularized with a DTB time of less than 90 minutes increased from 28.5% in 2003 to 67.2% in 2008 (P < .001). In-hospital mortality remained unchanged at 4.10% in 2003, 4.02% in 2004, 4.40% in 2005, 4.42% in 2006, 4.73% in 2007, and 3.62% in 2008 (P = .69). After the differences in baseline characteristics were adjusted for, there was no difference in the standardized mortality ratios (SMRs) across the study period (SMR, 1.00; 95% confidence interval [CI], 0.74-1.26 in 2003 compared with SMR, 0.95; 95% CI, 0.77-1.13 in 2008). CONCLUSIONS: There has been a dramatic reduction in median DTB time and increased compliance with the related national guideline. Despite these improvements, in-hospital mortality was unchanged over the study period. Our results suggest that a successful implementation of efforts to reduce DTB time has not resulted in the expected survival benefit.

Renal phenotype of UT-A urea transporter knockout mice.

The urea transporters UT-A1 and UT-A3 mediate rapid transepithelial urea transport across the inner medullary collecting duct (IMCD). In a previous study, using a new mouse model in which both UT-A1 and UT-A3 were genetically deleted from the IMCD (UT-A1/3(-/-) mice), we investigated the role of these transporters in the function of the renal inner medulla. Here the authors report a new series of studies investigating more generally the renal phenotype of UT-A1/3(-/-) mice. Pathologic screening of 33 tissues revealed abnormalities in both the testis (increased size) and kidney (decreased size and vascular congestion) of UT-A1/3(-/-) mice. Total urinary nitrate and nitrite (NOx) excretion rates in UT-A1/3(-/-) mice were more than double those in wild-type mice. Total renal blood flow was not different between UT-A1/3(-/-) and wild-type mice but underwent a greater percentage decrease in response to NG-Nitro-L-arginine methyl ester hydrochloride (L-NAME) infusion. Whole kidney GFR (FITC-inulin clearance) was not different in UT-A1/3(-/-) mice compared with controls and underwent a similar increase in response to a greater dietary protein intake. Fractional urea excretion was markedly elevated in UT-A1/3(-/-) mice on a 40% protein diet, reaching 102.4 +/- 8.8% of the filtered load, suggesting that there may be active urea secretion somewhere along the renal tubule. Although there was a marked urinary concentrating defect in UT-A1/3(-/-) mice, there was no decrease in aquaporin 2 or aquaporin 3 expression. Furthermore, although urea accumulation in the inner medulla was markedly attenuated, there was no decrease in sodium ion concentration in tissue from outer medulla or two levels of the inner medulla. These results support our conclusion that the urinary concentrating defect in UT-A1/3(-/-) mice is caused by a failure of urea transport from the IMCD lumen to the inner medullary interstitium, resulting in osmotic diuresis.