Significance of XXXX during @entity4710 .

@entity1 @entity662 @entity308 @entity2917 @entity301 @entity591 @entity880 @entity741 @entity453 @entity4710
During @entity4710 , @entity1 frequently experience @entity662 and marked @entity308 suggesting @entity741 . The purpose of this study was to assess whether ST @entity308 during @entity4710 is caused by @entity741 as reflected by net myocardial @entity880 production. Twenty-five @entity1 (14 @entity1 , 11 @entity1 ) who had a history of @entity4710 and a mean age (+/- SD) of 38 +/- 14 years underwent electrophysiologic testing. Twenty-four of these @entity1 had no evidence of @entity301 , whereas one @entity1 had undergone previous coronary bypass surgery. Nineteen @entity1 had orthodromic and six @entity1 had @entity2917 . A 12 lead electrocardiogram and simultaneous femoral artery and coronary sinus blood samples for @entity880 determinations were obtained at baseline and at 5 and 10 min of @entity4710 . Mean baseline heart rate of 83 +/- 12 beats/min increased to 180 +/- 25 beats/min during @entity4710 . All @entity1 had 1 to 8 mm of @entity308 in 1 to 9 of the 12 leads. @entity662 occurred in 64% of @entity1 during @entity4710 . Baseline myocardial @entity880 extraction was 28 +/- 13% with no significant change at 5 or 10 min of @entity591 . In contrast, in a comparison group of seven @entity1 with known @entity453 , atrial pacing at 168 +/- 26 beats/min in five @entity1 resulted in greater than or equal to 1 mm ST @entity308 in 2 to 7 of the 12 leads and a change in @entity880 extraction from a baseline of 29 +/- 13% to -27 +/- 20% (p less than 0.05) indicating net myocardial @entity880 production.(ABSTRACT TRUNCATED AT 250 WORDS)
