Creatine kinase adenosine triphosphate and phosphocreatine energy supply in a single kindred of patients with hypertrophic cardiomyopathy

Abstract

A lethal and extensively characterized familial form of hypertrophic cardiomyopathy (HC) is due to a point mutation (Arg403Gln) in the cardiac β-myosin heavy chain gene. Although this is associated with abnormal energy metabolism and progression to heart failure in an animal model, in vivo cardiac energetics have not been characterized in patients with this mutation. Noninvasive phosphorus saturation transfer magnetic resonance spectroscopy was used to measure the adenosine triphosphate supplied by the creatine kinase (CK) reaction and phosphocreatine, the heart's primary energy reserve, in 9 of 10 patients from a single kindred with HC caused by the Arg403GIn mutation and 17 age-matched healthy controls. Systolic and diastolic function was assessed by echocardiography in all 10 patients with HC. The patients with HC had impairment of diastolic function and mild systolic dysfunction, when assessed using global systolic longitudinal strain. Myocardial phosphocreatine was significantly decreased by 24% in patients (7.1 ± 2.3 μmol/g) compared with the controls (9.4 ± 1.2 μmol/g; p = 0.003). The pseudo-first-order CK rate-constant was 26% lower (0.28 ± 0.15 vs 0.38 ± 0.07 s⁻¹, p = 0.035) and the forward CK flux was 44% lower (2.0 ± 1.4 vs 3.6 ± 0.9 μmol/g/s, p = 0.001) than in the controls. The contractile abnormalities did not correlate with the metabolic indexes. In conclusion, myocardial phosphocreatine and CK-ATP delivery are significantly reduced in patients with HC caused by the Arg403Gln mutation, akin to previous results from mice with the same mutation. A lack of a relation between energetic and contractile abnormalities suggests the former result from the sarcomeric mutation and not a late consequence of mechanical dysfunction.

Fig. 1

Representative strain curves from an HC subject with strain value of 8.15% with sample volumes placed at the basal septum. AVO-aortic valve opening. AVC-aortic valve closure.

Fig. 2

(a)Transaxial scout magnetic resonance image of 52 yr old male HC patient, annotated to show location of 5 adjacent tissue volumes sampled by ³¹P magnetic resonance spectroscopy (b–d) in the chest wall (blue arrows), and anterior myocardium (red arrows). Spectra in (b) were acquired with no saturation applied for the purpose of measuring absolute concentrations. Spectra in (c) and (d) were acquired with control saturation (green arrow) and with γ-ATP saturated (amber arrow). The change in the height of the PCr peak (blue and red lines) is due to the forward flux through CK, and is proportional to the pseudo first-order rate constant. Each magnetic resonance spectroscopy data set was acquired in about 6min.

Fig. 3

[PCr], k_f and CK flux data in HC patients and healthy controls.