Tsuneo Tsuya

The prevalence and prognostic significance of arrhythmias in Duchenne type muscular dystrophy

To investigate the prevalence and prognostic significance of cardiac arrhythmias in Duchenne type muscular dystrophy 24-hour ambulatory ECG was performed in 80 patients with Duchenne type muscular dystrophy, and they were followed up for 5 years. Various arrhythmias were observed in 63.8% (51 of 80) of the patients. Ventricular premature beats were found in 30% (24 of 80), and the incidence of ventricular premature beats increased as the clinical severity of skeletal muscle involvement advanced. Forty-seven patients survived for 5 years, but the incidence of arrhythmias increased from 38.3% (18 of 47) to 74.5% (35 of 47) (p < 0.001). During the 5-year period, four of 33 deaths were sudden. Malignant ventricular premature beats (ventricular couplets, ventricular tachycardia, and R-on-T-type ventricular premature beats) were observed in three of these four patients. It appears that cardiac arrhythmias are a common complication of Duchenne type muscular dystrophy and that the incidence of ventricular arrhythmias increases with the progression of myocardial involvement. There is an association between ventricular arrhythmias and sudden death, but the reduction of ventricular arrhythmias may not reduce the incidence of episodes of sudden death.

Effect of dipyridamole at the usual oral dose on exercise-induced myocardial ischemia in stable angina pectoris

A randomized, double-blind, placebo-controlled study was performed to investigate the effect of dipyridamole at a usual oral dose of 150 mg/day on 18 patients with angina pectoris and positive treadmill exercise electrocardiography. After their angina pectoris was stabilized in phase 1, the patients were randomly assigned to sequence group A or B. Group A received a placebo 3 times daily in phase 2 and then 50 mg of dipyridamole 3 times daily in phase 3. Group B received the treatment in the reverse order. The degree of ST depression and the threshold for angina pectoris in treadmill exercise electrocardiography, which was performed on the last days of phases 2 and 3, were compared. The mean duration of exercise was 5 minutes and 23 seconds during dipyridamole and 5 minutes and 13 seconds during placebo administration, with no significant difference. Dipyridamole caused an aggravating effect on the ST change (earlier appearance of ST depression and/or deeper total sum of ST depression at the end of the exercise) in 3 patients, a salutary effect in 5 and no effect in 10. Dipyridamole decreased the threshold for angina pectoris in 5 patients, increased it in 6 and did not change it in 7. To summarize, dipyridamole showed adverse effects (aggravative effects on the ST change and/or on the threshold for angina pectoris) in 6 patients, beneficial effects in 8 and no effect in 4. A usual oral dose of dipyridamole induced myocardial ischemia during exercise in some patients while it improved it in a similar number of patients.

A 10-year follow-up study by orthogonal Frank lead ECG on patients with progressive muscular dystrophy of the Duchenne type

A 10-year follow-up study by orthogonal Frank lead electrocardiography was performed on 25 patients with progressive muscular dystrophy of the Duchenne type (DMD). With advancing age, no apparent changes were observed in the duration and amplitude of the P wave or in the PR interval, whereas the duration of the QRS complex tended to increase. The amplitudes of the R wave in lead X (Rx) and lead Y (Ry) tended to decrease from 1.75 +/- 0.90 and 1.96 +/- 0.59 mV to 0.80 +/- 0.63 and 1.39 +/- 0.62 mV (p < 0.01), whereas the amplitude of the S wave in lead X tended to increase from 0.24 +/- 0.23 mV to 0.53 +/- 0.36 mV in 10 years after initiation of the study (p < 0.01). It is noteworthy that the Ry amplitude began to decrease markedly from the seventh year after the initiation of this study, whereas the Rx amplitude showed a gradual and unceasing decline through the 10-year period. Observation of the sequential changes of the QRS loops in three planes clearly demonstrated that the electrical force tended to decrease in the leftward and inferior directions and increase in the rightward direction. It is of interest that the frequency of occurrence of the deep Q wave was found to be quite high even in the early stages of DMD and that it did not display a direct relation to the sequential evolution of this disease. It can be concluded that observation of the sequential changes in the QRS complex allows estimation of the extent and direction of myocardial involvement in DMD.