Are troponin levels always elevated in patients with Duchenne muscular dystrophy (DMD)?

Troponin Levels in Duchenne Muscular Dystrophy (DMD)

Troponin levels are not always elevated in patients with Duchenne muscular dystrophy (DMD), but they can be elevated in a significant proportion of patients, particularly those with cardiac involvement, and may correlate with disease progression and myocardial damage. 1, 2

Patterns of Troponin Elevation in DMD

• Troponin elevations in DMD patients can occur in both symptomatic and asymptomatic individuals, with higher levels typically seen in those with more advanced cardiac involvement 1
• In a study of DMD patients, those with mild late gadolinium enhancement (LGE) on cardiac MRI had significantly higher troponin I levels (0.28 ± 0.36 ng/ml) compared to those without LGE (0.05 ± 0.08 ng/ml) 1
• Troponin I levels correlate positively with native T1 values on cardiac MRI, suggesting a relationship between troponin elevation and myocardial fibrosis 1
• Acute chest pain episodes in DMD patients can be associated with marked troponin elevation (mean peak cTn level of 44±15.4 ng/mL) and may represent important events in cardiomyopathy progression 3

Mechanisms of Troponin Elevation in DMD

• Troponin elevation in DMD reflects myocardial damage that occurs as part of the dystrophic degeneration of cardiac muscle 4
• Unlike acute coronary syndromes where troponin elevation indicates ischemic injury, in DMD the elevation is due to ongoing cardiomyocyte damage related to the underlying dystrophinopathy 5
• The cardiac isoforms of troponin T and I are exclusively expressed in cardiac myocytes, making their detection in blood specific for myocardial damage 6
• Troponin elevation in DMD may occur in the absence of overt clinical symptoms, representing subclinical cardiac involvement 4

Clinical Significance of Troponin in DMD

• Troponin levels may serve as a useful minimally invasive biomarker to monitor myocardial disease progression in DMD cardiomyopathy 1
• Elevated troponin T levels correlate with decreased left ventricular ejection fraction (LVEF) and North Star Ambulatory Assessment scores in DMD patients 2
• Patients with North Star scores of ≤16 are at higher risk of developing cardiomyopathies and may show elevated troponin levels 2
• Troponin elevation in DMD appears to correlate with proBNP levels and LVEF values, suggesting its utility as a cardiac index for evaluating myopathic patients 2

Distinguishing Features from Other Causes of Troponin Elevation

• True false-positive troponin results have been documented in skeletal myopathies, but current assays have largely overcome these deficiencies 6
• Elevated troponin in DMD should be distinguished from other non-ischemic causes of troponin elevation such as myocarditis, heart failure, pulmonary embolism, or renal failure 6
• The pattern of troponin elevation in DMD differs from that seen in acute coronary syndromes, as it may not show the characteristic rise and fall pattern 6
• When interpreting troponin results in DMD patients, clinicians should consider the clinical context and other cardiac evaluation findings rather than assuming an acute coronary syndrome 5

Recommendations for Troponin Testing in DMD

• High-sensitivity cardiac troponin I assays are recommended for longitudinal monitoring in DMD patients 5
• Troponin should be considered as part of routine cardiac monitoring in DMD patients, particularly as they age and cardiac involvement becomes more prevalent 5
• Troponin elevation in DMD patients presenting with chest pain warrants careful evaluation, as it may indicate progression of cardiomyopathy rather than coronary artery disease 3
• Cardiac MRI should be considered in DMD patients with elevated troponin levels to assess for myocardial fibrosis and ventricular dysfunction 1, 3