Remodeling after myocardial infarction and effects of heart failure treatment investigated by hyperpolarized [1‐13C]pyruvate magnetic resonance spectroscopy.

Purpose: Hyperpolarized [1‐13C]pyruvate MRS can measure cardiac metabolism in vivo. We investigated whether [1‐13C]pyruvate MRS could predict left ventricular remodeling following myocardial infarction (MI), long‐term left ventricular effects of heart failure medication, and could identify responders to treatment. Methods: Thirty‐five rats were scanned with hyperpolarized [1‐13C]pyruvate MRS 3 days after MI or sham surgery. The animals were re‐examined after 30 days of therapy with β‐blockers and ACE‐inhibitors (active group, n = 12), placebo treatment (placebo group, n = 13) or no treatment (sham group, n = 10). Furthermore, heart tissue mitochondrial respiratory capacity was assessed by high‐resolution respirometry. Metabolic results were compared between groups, over time and correlated to functional MR data at each time point. Results: At 30 ± 0.5 days post MI, left ventricular ejection fraction (LVEF) differed between groups (sham, 77% ± 1%; placebo, 52% ± 3%; active, 63% ± 2%, P <.001). Cardiac metabolism, measured by both hyperpolarized [1‐13C]pyruvate MRS and respirometry, neither differed between groups nor between baseline and follow‐up. Three days post MI, low bicarbonate + CO2/pyruvate ratio was associated with low LVEF. At follow‐up, in the active group, a poor recovery of LVEF was associated with high bicarbonate + CO2/pyruvate ratio, as measured by hyperpolarized MRS. Conclusion: In a rat model of moderate heart failure, medical treatment improved function, but did not on average influence [1‐13C]pyruvate flux as measured by MRS; however, responders to heart failure medication had reduced capacity for carbohydrate metabolism. [ABSTRACT FROM AUTHOR]