Duchenne muscular dystrophy (DMD) is an inherited muscular disease characterized by progressive and fatal muscle weakness. Electrocardiographic (ECG) abnormalities, including abnormal R wave amplitudes are frequently observed in DMD. However, clinical implications of abnormal R wave amplitudes remain unclear. Hence, DMD patients were examined for changes in R wave amplitude over time using synthesized 18-lead ECG and the relationship between R wave amplitude and cardiac function. The results of 969 ECG examinations of 193 patients with DMD who underwent electrocardiography and echocardiography on the same day were retrospectively reviewed. A negative correlation was observed between R wave amplitude and age. Positive correlations between R wave amplitude and left ventricular ejection fraction were observed in leads V4, V5, V6, syn-V7, syn-V8, and syn-V9, with V6 showing the strongest correlation (r = 0.52). Mean R wave amplitude during cardiac dysfunction was lower than that observed with preserved cardiac function in leads V6 to syn-V9. Patients had preserved R wave amplitude up to three years before the onset of cardiac dysfunction, with a sharp decrease two years before cardiac dysfunction in leads V6 to syn-V9. In DMD patients, the R wave amplitude decreases with age. The sharp decline in R amplitude two years before cardiac dysfunction indicates that electrophysiological damage to the myocardium of the left ventricle lateral to the posterior wall precedes the finding of cardiac dysfunction. The R amplitude in V6 of the standard 12-lead ECG is a convenient predictive marker of cardiac dysfunction, similar to that of the 18-lead ECG.

Eighteen-lead electrocardiography (18-ECG) includes, in addition to those in standard 12-lead ECG (12-ECG), six additional chest leads: V7–V9 and V3RV5R. Leads V7–V9 require the patient to be in a lateral decubitus position for the electrodes to be attached to the back. Synthesized 18-ECG (syn18-ECG) is a method that only records 12-ECG and uses computational logic to record the posterior wall (V7–V9) and right-sided (V3R–V5R) leads. We review the clinical utility of syn18-ECG in conditions including acute coronary syndromes, arrhythmias, acute pulmonary embolism, and Duchenne muscular dystrophy. The syn18-ECG waveform correlates well with the actual 18-ECG waveform, indicating that syn18-ECG is an excellent substitute for 18-ECG, excluding negative T waves. ST elevation in leads V7–V9 has the effect of reducing missed acute coronary syndromes in the posterior wall. In cases of arrhythmia, syn18-ECG can accurately estimate the target site of radiofrequency catheter ablation using a simple algorithm. The use of additional leads in Duchenne muscular dystrophy is expected to provide new insights. To facilitate gaining more knowledge regarding diseases that have not yet been investigated, it is imperative that the cost of syn18-ECG is reduced in the future.

Background/Objectives: Duchenne muscular dystrophy (DMD) is an X-linked inherited muscle disease. Patients with DMD demonstrate improved prognosis with angiotensin-converting enzyme inhibitors and beta-blockers at the time of cardiac dysfunction. However, most deaths due to DMD are due to cardiac dysfunction. Fragmented QRS (fQRS) is an abnormal finding that forms a notch in the QRS wave on electrocardiography (ECG) and is associated with fibrosis and scarring of the myocardium. Methods: Patients with DMD were examined for the number of leads of fQRS, their sites of appearance, changes in cardiac dysfunction, and age using the chest leads of a synthesized 18-ECG. A retrospective analysis of 184 patients under 20 years of age with DMD and known genetic mutations was performed; they were divided into three age groups: 3–10, 11–15, and 16–20 years. The chest leads of the ECG were defined as follows: V1-3, anterior leads; V4-6, lateral leads; V7-9, posterior leads; and V3R-V5R, right-sided chest leads. Cardiac dysfunction was defined as a left ventricular (LV) ejection fraction <53% on the same day, and echocardiography was performed. LV dilation was defined as dilation beyond the normal range, considering the body surface area. Results: In 167 of 184 patients (91%), fQRS was present in one or more chest leads. The number of fQRS leads in the anterior and lateral walls was significantly higher in 16–20-year-olds than in 3–10-year-olds. The total number of chest leads with fQRS was 4.9 ± 3.1 in the cardiac dysfunction group and 3.5 ± 2.5 in the preserved group. The cardiac dysfunction group had a significantly greater number of fQRS leads than did the preserved group (p = 0.003). The group with LV dilation had a significantly greater number of fQRS leads than did the non-dilation group (p = 0.009). Conclusions: The fQRS site is associated with age, cardiac dysfunction, and LV dilation. Multivariate regression analysis revealed that the number of anterior leads of the fQRS correlated with age and that of lateral leads of the fQRS with cardiac dysfunction and LV dilation. The number of fQRS leads on the lateral wall marks cardiac dysfunction and LV dilation.