ASSOCIATION OF MYOTONIC-DYSTROPHY AND SICK SINUS SYNDROME, WITH SPECIAL REFERENCE TO ELECTROPHYSIOLOGICAL AND HISTOLOGICAL EXAMINATIONS

Sick sinus syndrome is a rare but potentially important cardiac disord er in patients with myotonic dystrophy. We evaluated 3 patients with m yotonic dystrophy complicated with sick sinus syndrome using intracard iac electrocardiography and endomyocardial biopsy. Electrocardiography identified sinus arrest, atrial flutter and right bundle-branch block in 2 cases and marked sinus bradycardia and first-degree atrioventric ular block in 1 case, Their sinus node recovery times were significant ly prolonged as demonstrated by the overdrive suppression test. Two pa tients had Adams-Stokes syndrome and one had tachycardia with severe p alpitations, Therefore permanent pacemaker implantation was indicated in all 3 cases, Light microscopic analysis of right ventricular endomy ocardial biopsies showed vacuolar degeneration and nuclear deformity o f cardiomyocytes in all cases and endocardial and interstitial fibrosi s in 1 case, These findings indicate that pathological changes may occ ur in any part of the myocardium in patients with myotonic dystrophy.