107 Remote ischaemic preconditioning and human atrial trabeculae in the diabetic heart

Abstract

coronary artery diameter was measured by quantitative angiography. An incremental pacing protocol that raised heart rate to a maximum of 150 bpm was undertaken in all patients via a temporary right atrial pacing wire. Pacing was performed in the presence of saline vehicle and then either L-NMMA or SMTC (one inhibitor per patient; n¼9 each group).Results SMTC (0.625 mmol/min) and L-NMMA (25 mmol/min) both reduced basal CBF to a similar extent (À22.8%61.24% vs À26.8%62.16%; n¼9 each; p¼NS). During saline infusion, CBF increased with atrial pacing from 58.769.90 to 87.4617.3 ml/min (n¼9, p<0.05). During L-NMMA, the increase in CBF was significantly blunted compared to that during saline (DCBF 17.764.54 ml/ min vs 28.768.08 ml/min during saline; n¼9, p<0.05 by 2-way ANOVA). In patients receiving SMTC, however, the increase in CBF with pacing was similar to that during saline (DCBF 36.566.05 ml/ min vs 25.266.65 ml/min during saline; n¼9, p¼NS by 2-way ANOVA). SMTC and L-NMMA both reduced basal coronary artery diameter to a similar extent (n¼9). L-NMMA blunted the pacinginduced increase in coronary artery diameter (n¼9, p<0.05 vs saline vehicle) whereas SMTC had no effect (n¼9, p¼NS). Conclusion These results suggest that increases in human coronary blood flow in response to incremental atrial pacing are mediated by eNOS-derived NO rather than nNOS-derived NO.