In myotonic dystrophy type 2 (DM2/PROMM), cardiac muscle involvement is usuall y more benign than in DM1, but clinically severe cardiomyopathy has been reporte d in some patients. Using a novel method of magnetic resonance spectroscopy (MRS ), we examined the left ventricular myocardium and the left gastrocnemius muscle in 11 unselected DM2/ PROMM patients without overt cardiac disease. Data on car diac morphology and function were obtained by gradient echo two dimensional cin e magnetic resonance imaging (MRI); no significant differences were found betwee n DM2 patients and healthy controls, but using a median split approach older pat ients showed mildly increased left ventricular (LV) volumes, i.e., 59%increase of end systolic volume index (ESVI) and 35%increase of enddiastolic volume ind ex (EDVI), and an increase of LV mass (26%). On cardiac MRS, DM2/PROMM patients showed a reduction of phosphocreatine (PCr) and adenosine triphosphate (ATP) by 25 and 20%compared to matched healthy controls. No significant differences wer e found between younger and older patients. In skeletal muscle of the DM2 patien ts, no significant decrease of PCr and ATP concentrations was found. However, in older patients, who commonly show overt hip flexor muscle weakness, we observed reduced values for PCr and ATP. Our MRS and MRI findings reveal evidence for su bclinical cardiomyopathy in DM2/PROMM patients without overt heart disease. Futu re prospective studies are needed to clarify the risk of developing overt cardia c disease in DM2 and to define prognostic factors. Using a novel method of magnetic resonance spectroscopy (MRS), we examined the potential of the cardiac muscle involvement in a more benign than in DM1, but clinically severe cardiomyopathy has been reported in d in some patients. left ventricular myocardium and the left gastrocnemius muscle in 11 unselected DM2 / PROMM patients without overt cardiac disease. Data on car diac morphology and function were obtained by gradient echo two dimensional cin e magnetic resonance imaging (MRI); no significant differences were found betwee n DM2 patients and healthy controls, but using a median split approach older patients mildly increased left ventricular (LV) volumes, ie, 59% increase of end systolic volume index (ESVI) and 35% increase of endiastolic volume ind ex (EDVI) , and an increase of LV mass (26%). On cardiac MRS, DM2 / PROMM patients showed a reduction of phosphocreatine (PCr) and adenosine triphosphate (ATP) by 25 and 20% compared to matched healthy controls. No significant differences wer e found between younger and older patients. In skeletal muscle of the DM2 patien ts, no significant decrease of PCr and ATP concentrations was found. However, in older patients, who commonly show overt hip flexor muscle weakness, we observed reduced values ​​for PCr and ATP. Our MRS and MRI findings reveal evidence for su bclinical cardiomyopathy in DM2 / PROMM patients without overt heart disease. Futu re prospective studies are needed to clarify the risk of developing overt cardia c disease in DM2 and to define prognostic factors.