Myocardial Energy Status Evaluation During Hypotension in Hypertensive and Aged Models

Abstract

Objective: To evaluate the myocardial energy metabolism during hypotensive conditions in hypertensive and aged subjects, we observed real-time changes in myocardial surface NADH fluorescence as an indicator of myocardial oxygen and blood supply. Methods: Isolated rat hearts (WKY of 9, 16 wks; SHR of 9, 16 wks) were Langendorff-perfused and were subjected to hypoperfusion followed by reperfusion. NADH images were real-timely video-recorded and time-course changes in NOx (endproduct of NO) concentration in the coronary effluent was measured. Results: In all isolated hearts, myocardial NADH fluorescence during hypoperfusion increased heterogeneously within 30 sec of hypoperfuion and then reached a steady level. This heterogeneous fluorescent pattern (patchy pattern size; 500 μm2, approximately) during hypoperfusion appeared individually in different area and returned to the control level rapidly during reperfusion. Changes in NADH fluorescent intensity during hypoperfusion were not significantly different between 9-wk WKY and 9-wk SHR (55.1 ± 1.2 AU, 55.2 ± 0.9 AU, respectively). In contrast, 16-wk SHR showed significantly higher NADH intensity than 16-wk WKY (WKY, 61.8 ± 1.2 AU; SHR, 70.1 ± 12 AU; p < 0.05). Maximum NOx production during hypoperfusion significantly reduced in 16-wk SHR than control levels (57.7 ± 13.8% of control level, p < 0.05). Conclusions: Myocardial energy status changed heterogeneously during hypoperfusion/reperfusion. The heterogeneous distribution and time-course changes of NADH fluorescence were highly correlated with hypertension and aging and may reflect functional (including NO) and structural changes in the coronary microcirculation and myocardial oxygen balance.