BACKGROUND: In myotonic dystrophy (DM), striated muscle is involved in relation to the size of the DNA mutation. Smooth muscle may be similarly impaired at the level of the urinary and digestive apparatus and possibly at the level of small vessels, since microangiopathy has been described in the iris and digital capillaries. Our purpose was to study the function of the myocardial microvasculature in relation to the size of the mutation in DM patients without clinical cardiac involvement and with normal left ventricular dimensions and function and normal large coronary arteries. METHODS AND RESULTS: In 6 control subjects and 10 DM patients, we investigated the coronary blood flow reserve using positron emission tomography with 15O-labeled water. Global and regional flow reserves were obtained from myocardial regions of interest manually drawn on a static FDG image encompassing, respectively, the whole left ventricle and the anterior, septal, and lateral walls. The DNA mutation size was determined on circulating lymphocytes in each DM patient. Compared with control subjects, DM patients had decreased global (2.39 +/- 0.39 versus 4.00 +/- 0.67, P = .00003) and regional (anterior, 2.39 +/- 0.64 versus 3.87 +/- 0.92, P = .002; septal, 2.60 +/- 0.48 versus 4.00 +/- 0.70, P = .0003; lateral, 2.26 +/- 0.58 versus 4.16 +/- 1.11, P = .0005) coronary reserves. In DM patients, the coronary reserve correlated strongly and inversely with the DNA mutation size (r = -.77, P = .009). CONCLUSIONS: The study demonstrated that global and regional coronary reserves are impaired, in relation to the DNA mutation size, in symptom-free DM patients with normal ventricular dimensions and function and normal large coronary vessels. We suggest that a gene-related blunted coronary reserve resulting from an impairment of vascular smooth muscle is an early component of DM cardiomyopathy.
BACKGROUND: In myotonic dystrophy (DM), striated muscle is involved in relation to the size of the DNA mutation. Smooth muscle may be similarly impaired at the level of the urinary and digestive apparatus and possibly at the level of small vessels, since microangiopathy has been described in the iris and digital capillaries. Our purpose was to study the function of the myocardial microvasculature in relation to the size of the mutation in DMpatients without clinical cardiac involvement and with normal left ventricular dimensions and function and normal large coronary arteries. METHODS AND RESULTS: In 6 control subjects and 10 DMpatients, we investigated the coronary blood flow reserve using positron emission tomography with 15O-labeled water. Global and regional flow reserves were obtained from myocardial regions of interest manually drawn on a static FDG image encompassing, respectively, the whole left ventricle and the anterior, septal, and lateral walls. The DNA mutation size was determined on circulating lymphocytes in each DMpatient. Compared with control subjects, DMpatients had decreased global (2.39 +/- 0.39 versus 4.00 +/- 0.67, P = .00003) and regional (anterior, 2.39 +/- 0.64 versus 3.87 +/- 0.92, P = .002; septal, 2.60 +/- 0.48 versus 4.00 +/- 0.70, P = .0003; lateral, 2.26 +/- 0.58 versus 4.16 +/- 1.11, P = .0005) coronary reserves. In DMpatients, the coronary reserve correlated strongly and inversely with the DNA mutation size (r = -.77, P = .009). CONCLUSIONS: The study demonstrated that global and regional coronary reserves are impaired, in relation to the DNA mutation size, in symptom-free DMpatients with normal ventricular dimensions and function and normal large coronary vessels. We suggest that a gene-related blunted coronary reserve resulting from an impairment of vascular smooth muscle is an early component of DM cardiomyopathy.
Authors: Georgia Besant; Pierre R Bourque; Ian C Smith; Sharon Chih; Mariana M Lamacie; Ari Breiner; Jocelyn Zwicker; Hanns Lochmüller; Jodi Warman-Chardon Journal: Front Cardiovasc Med Date: 2022-06-03