Is periodic tachycardia a normal finding in patients with Duchenne muscular dystrophy (DMD)?

Periodic Tachycardia in Duchenne Muscular Dystrophy

Yes, sinus tachycardia is a frequent and normal finding in patients with Duchenne muscular dystrophy (DMD) and often precedes cardiac dysfunction. 1

Cardiac Manifestations in DMD

DMD is characterized by progressive skeletal muscle weakness, but cardiac involvement is a significant contributor to morbidity and mortality. The cardiac manifestations in DMD follow a predictable pattern:

Early Cardiac Changes

• Sinus tachycardia: Often one of the earliest cardiac manifestations

  • Appears frequently in DMD patients 1
  • May precede overt cardiac dysfunction 1
  • Can serve as a useful biomarker in clinical monitoring 1
  • May reflect early respiratory involvement 1

• ECG changes: In a study of pediatric DMD patients:

  • 28.57% of DMD patients exhibited sinus tachycardia (compared to 6.88% of controls) 2
  • 39.29% showed prolonged QTc intervals 2
  • These ECG manifestations may serve as an early warning sign before echocardiographic abnormalities appear 2

Disease Progression

As DMD progresses, cardiac involvement typically follows this sequence:

1. Sinus tachycardia and ECG abnormalities
2. Regional myocardial thinning and fibrosis
3. Left ventricular dysfunction
4. Dilated cardiomyopathy
5. Heart failure

Clinical Implications and Monitoring

Significance of Tachycardia

• Periodic tachycardia should be viewed as an expected finding in DMD patients
• It may serve as a biomarker for:
  • Early cardiac involvement
  • Possible respiratory component 1
  • Need for more intensive cardiac monitoring

Recommended Cardiac Monitoring

• Cardiac MRI (CMR) is preferred over echocardiography when possible 1

  • Provides superior information on tissue characteristics, chamber dimensions, and function
  • Can detect late gadolinium enhancement (an indicator of myocardial fibrosis)
  • Echocardiography may be necessary in younger children requiring sedation

• Holter monitoring is most valuable in patients with:

  • Established cardiac dysfunction (LVEF <35%) 3
  • Symptoms suggestive of arrhythmias

Risk Stratification

• Patients with normal left ventricular function (LVEF ≥55%) have low risk of significant arrhythmias despite periodic tachycardia 3
• Significant arrhythmias become more common as cardiac function deteriorates:
  • Patients with LVEF <35% have higher rates of:
    • Nonsustained atrial tachycardia
    • Frequent premature ventricular contractions
    • Ventricular couplets/triplets
    • Nonsustained ventricular tachycardia 3

Management Considerations

Early Intervention

• ACE inhibitors or ARBs should be started by 10 years of age (barring contraindications) 1
• Earlier therapy may be considered given the relatively low risk of these medications 1
• β-blockers are typically added after ACE inhibitor/ARB initiation, especially in patients with:
  • Ventricular dysfunction
  • Elevated heart rate 1

Monitoring Recommendations

• Regular cardiac assessment including:
  • ECG to monitor for tachycardia and other electrical abnormalities
  • Imaging (preferably CMR when feasible) to assess for structural changes
  • Consideration of Holter monitoring in patients with decreased LVEF or symptoms

Important Caveats

• Sinus tachycardia alone does not necessarily warrant treatment in DMD patients
• Tachycardia should prompt evaluation for:
  • Cardiac dysfunction
  • Respiratory compromise
  • Other causes (infection, anemia, pain, anxiety)
• Sudden cardiac events are rare in DMD patients with preserved cardiac function (LVEF >35%) 3
• The presence of left ventricular systolic dysfunction is a more powerful predictor of mortality than ECG abnormalities or ventricular arrhythmias 4