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Figure 2 Calendar time trend. The geometric mean door-to-needle times for 68,439 patients (white squares) and geometric mean door-to-balloon times for 33,647 patients (black diamonds) for each quarter from January 1999 to December 2002. There was no significant trend for either door-to-needle times (p = 0.956) or door-to-balloon times (p = 0.094).