Letter by Wiggers et al Regarding Article by Tuunanen et al, “Free Fatty Acid Depletion Acutely Decreases Cardiac Work and Efficiency in Cardiomyopathic Heart Failure”
To the Editor:
Tuunanen et al1 report that in patients with heart failure, an acute reduction in circulating free fatty acids depresses cardiac function. These results are different from findings by our group2; they also seem to diverge from observations by Mäki et al.3 We believe that the findings of Tuunanen et al should be interpreted with caution because the results can be biased by limitations in the study design. Both in healthy subjects and in patients, an 8-mL decrease in stroke volume was observed between the initial echocardiography (baseline) and 4 to 5 hours later after treatment with acipimox. A placebo arm was not included; therefore, a potential explanation of the decrease in stroke volume observed in controls and patients is a systematic period effect occurring during the course of the study day.4 This is consistent with the duration of the resting state, a decrease in circulating catecholamines, and changes in preload.
Tuunanen H, Engblom E, Naum A, Nagren K, Hesse B, Airaksinen KE, Nuutila P, Iozzo P, Ukkonen H, Opie LH, Knuuti J. Free fatty acid depletion acutely decreases cardiac work and efficiency in cardiomyopathic heart failure. Circulation. 2006; 114: 2130–2137.
Wiggers H, Norrelund H, Nielsen SS, Andersen NH, Nielsen-Kudsk JE, Christiansen JS, Nielsen TT, Moller N, Botker HE. Influence of insulin and free fatty acids on contractile function in patients with chronically stunned and hibernating myocardium. Am J Physiol Heart Circ Physiol. 2005; 289: H938–H946.
Mäki M, Luotolahti M, Nuutila P, Iida H, Voipio-Pulkki L, Ruotsalalainen U, Haaparanta M, Solin O, Hartiala J, Harkonen R, Knuuti J. Glucose uptake in the chronically dysfuctional but viable myocardium. Circulation. 1996; 93: 1658–1666.