Although muscle weakness is the most well-known symptom of Duchenne muscular dystrophy (DMD), this condition also quietly interferes with the heart’s normal function. According to a new study published in the Journal of Electrocardiology, these changes can be caught early on using a simple, non-invasive heart test called a lead II electrocardiogram (ECG).
A lead II ECG records the electrical activity of the heart and allows doctors to detect subtle changes before symptoms appear. In this new study, researchers used it to compare two groups: 54 boys with DMD and 31 boys of the same age without DMD.
They found several differences in heart signals among the boys with DMD — even though none had been diagnosed with heart problems. This suggests the heart may begin working differently early in the disease, well before any signs are noticeable.
These findings highlight the importance of regular heart monitoring in DMD patients.
Read more about DMD testing and diagnosis
One measurement from the lead II ECG, called the PR interval, which tracks how long it takes for electrical impulses to travel from the upper to the lower chambers of the heart, was shorter than normal in the DMD group. This suggests the heart was working too quickly at that stage of the heartbeat.
Another measurement, called the QRS interval, which reflects how long it takes the lower chambers to contract, was longer in the DMD group. The QT interval, which measures how long the heart takes to squeeze and then reset for the next beat, was also longer in boys with DMD. These longer intervals suggest the heart was having more difficulty moving through each full beat.
The researchers noticed a difference in a measurement called the Tp-Te interval, which tracks how evenly the heart muscle resets after each beat. In boys with DMD, this interval was longer. Longer Tp-Te intervals can make the heart rhythm less stable.
Finally, they also saw stronger-than-normal electrical waves in parts of the ECG. This included increases in P, Q and R waves, as well as higher points in the ST segment. These signal changes can reflect enlargement of the heart’s upper chambers.
A simple lead II ECG can pick up on all these changes early.
“Given the risk of sudden cardiac death associated with DMD, the incorporation of Lead II ECG analysis into routine clinical assessments of DMD patients is recommended,” the study’s authors said. “This approach could facilitate timely interventions, improving patient outcomes and quality of life.”
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