Metabolic flexibility and reverse remodelling of the failing human heart.

BACKGROUND AND AIMS: Cardiac resynchronization therapy (CRT) produces long-term reverse remodelling which requires greater adenosine triphosphate delivery to the contractile machinery. Whilst the heart retains some metabolic flexibility in non-ischaemic cardiomyopathy, whether this correlates with reverse remodelling is unknown. This study investigated whether CRT acutely changes cardiac substrate uptake, and whether this translates to favourable reverse remodelling.

METHODS

The effect of CRT on cardiac substrate uptake was assessed via direct coronary flow and arteriovenous measurements, with metabolomic/lipidomic analysis on infusions of insulin/glucose and intralipid. Cardiac function was assessed with left ventricular pressure-volume loops during implantation, and cardiac magnetic resonance before and 6 months following CRT, with and without biventricular pacing.

RESULTS

Regardless of substrate infusion, CRT acutely improved stroke work without increasing O2 uptake on both insulin/glucose (by 34%, P = .05) and intralipid (by 36%, P = .03). This was followed by increased fatty acid (FA) uptake on insulin/glucose (R = 0.89, P = .03) and increased β-hydroxybutyrate uptake (R = 0.81, P = .05) during intralipid infusion. After 6 months, there was a 48% (P < .001) reduction in left ventricular end diastolic volume, beyond that achievable by acutely shortening or lengthening QRS duration. Reverse remodelling significantly correlated with increased FA uptake with CRT on insulin/glucose (R = 0.71, P = .05) driven by long and medium chain uptake, and increased ketone uptake with CRT on intralipid (R = 0.79, P = .05).

CONCLUSIONS

CRT acutely alters the metabolic phenotype of non-ischaemic cardiomyopathy towards a more physiological picture of FA uptake which correlates with reverse remodelling. Retained metabolic flexibility may therefore be critical for subsequent reverse remodelling.