How should troponin levels be interpreted in a patient on peritoneal dialysis (PD)?

Interpreting Troponin Levels in Peritoneal Dialysis Patients

Elevated troponin levels in peritoneal dialysis patients should be interpreted as true cardiac injury rather than simply attributed to impaired clearance, with a focus on distinguishing between acute coronary syndromes and chronic myocardial damage through serial measurements and clinical context.

Understanding Baseline Elevations

• Elevated cardiac troponins are common in peritoneal dialysis (PD) patients even without acute cardiac symptoms:
  • 42% of troponin I and 98% of troponin T measurements exceed the decision level for myocardial infarction in dialysis patients 1
  • These elevations are not spurious findings - they originate from cardiac tissue even though clearance may be altered 2
  • PD patients have similar troponin levels to hemodialysis patients (median troponin I: 21 ng/L vs. 25 ng/L; troponin T: 67 ng/L vs. 70 ng/L) 1

Diagnostic Approach for Acute Coronary Syndromes

1. Focus on pattern of change rather than absolute values:

   • A time-appropriate rise and fall pattern is key for diagnosing acute coronary syndromes 2
   • Use reference change values (RCVs) to detect significant changes: +68/-41% for troponin I and +29/-23% for troponin T 1
   • During acute coronary syndrome, troponin rises above the individual's baseline and tends to return to baseline after recovery 3

2. Integrate with clinical presentation:

   • Evaluate the triad of symptoms, ECG findings, and cardiac biomarkers 2
   • Consider the quantitative nature of troponin elevation - higher levels increase likelihood of MI 2
   • Look for new ischemic ECG changes or imaging evidence of new myocardial damage 2

Prognostic Significance

• Elevated troponin levels have important prognostic value in PD patients:
  • Troponin T is a stronger predictor of mortality than troponin I in dialysis patients 1
  • Mortality risk is doubled in patients with persistently high troponin T levels 1
  • Troponin T can predict cardiovascular congestion in PD patients and provides incremental prognostic value when combined with left ventricular mass and ejection fraction 4

Alternative Causes of Troponin Elevation

Consider non-ACS causes of troponin elevation in PD patients:

• Left ventricular hypertrophy (positive correlation between troponin T and LV mass) 5
• Chronic myocardial damage 3
• Other conditions that can elevate troponins in any patient 6:
  • Heart failure
  • Tachyarrhythmias
  • Myocarditis
  • Takotsubo cardiomyopathy
  • Pulmonary embolism
  • Hypertensive emergencies

Practical Recommendations

1. Establish baseline values:

   • Obtain baseline troponin measurements in stable PD patients
   • Use these values for comparison during acute presentations

2. Serial measurements:

   • When suspecting acute coronary syndrome, obtain serial measurements (0h, 3h)
   • Look for significant changes using reference change values

3. Risk stratification:

   • Use troponin T levels for cardiovascular risk stratification in stable PD patients 2
   • Consider additional cardiac evaluation (e.g., stress imaging) in patients with persistently elevated troponins 2

Common Pitfalls to Avoid

• Don't dismiss elevated troponins as merely due to reduced clearance - they reflect true cardiac pathology 2
• Don't rely solely on absolute cutoff values designed for the general population - focus on dynamic changes from baseline
• Don't overlook the prognostic value of elevated troponins even in asymptomatic PD patients
• Don't fail to consider the wide range of cardiac and non-cardiac conditions that can cause troponin elevation in PD patients

By following these principles, clinicians can appropriately interpret troponin levels in PD patients, avoiding both under-diagnosis of acute coronary syndromes and over-diagnosis in patients with chronic elevations.