I have postural orthostatic tachycardia syndrome and after a recent hospital admission my labs show elevated C‑reactive protein (11.8 mg/L), venous base excess of –8 mmol/L, and minimally detectable troponin and D‑dimer; should I be concerned?

Should You Be Concerned About These Lab Results?

Yes, you should be concerned—these results indicate acute systemic inflammation with metabolic acidosis and possible cardiac or thrombotic stress that requires immediate medical evaluation to exclude serious underlying conditions, even though your POTS may explain some findings.

Understanding Your Results in Context

Your laboratory abnormalities suggest an acute process superimposed on your chronic POTS diagnosis that warrants investigation:

C-Reactive Protein (11.8 mg/L)

• Your CRP is moderately elevated (normal <3 mg/L), indicating active systemic inflammation 1
• While CRP elevation occurs in various conditions including infections, autoimmune disorders, and cardiovascular disease, this level suggests an acute inflammatory process requiring identification 1
• In the context of cardiac symptoms, elevated CRP has prognostic significance and may indicate myocardial stress or injury 1
• This elevation is NOT explained by POTS alone—POTS patients may have baseline inflammatory markers, but this level suggests an acute trigger 2, 3

Base Excess of -8 mmol/L

• This represents moderate metabolic acidosis (normal range -2 to +2 mmol/L) that requires immediate investigation 1
• Possible causes include:
  • Lactic acidosis from tissue hypoperfusion (sepsis, shock, severe dehydration) 1
  • Diabetic ketoacidosis or other metabolic derangements 1
  • Renal dysfunction with acid accumulation 1
• This is a red flag finding that indicates your tissues may not be receiving adequate oxygen or your body cannot clear metabolic acids properly 1

Barely Detectable Troponin

• Even minimal troponin elevation is never normal and indicates some degree of myocardial injury 1, 4
• The 2021 AHA/ACC guidelines emphasize that any troponin above the 99th percentile threshold warrants serial measurement at 2-3 hour intervals to detect a rising/falling pattern 1
• Causes of troponin elevation beyond acute MI include:
  • Myocarditis (viral or autoimmune) 4, 5
  • Pulmonary embolism with right ventricular strain 5
  • Severe tachycardia causing demand ischemia 1
  • Heart failure or cardiomyopathy 1, 5
  • Sepsis with myocardial depression 1, 5
• In POTS patients specifically, prolonged severe tachycardia can cause demand ischemia and troponin leak, but this still requires cardiac evaluation 2, 3

Barely Detectable D-Dimer

• Any D-dimer elevation indicates activation of coagulation and fibrinolysis 1
• While not highly specific, elevated D-dimer in your clinical context raises concern for:
  • Pulmonary embolism (which can cause troponin elevation, tachycardia, and metabolic acidosis) 1, 5
  • Aortic dissection (though typically D-dimer is markedly elevated) 1
  • Deep venous thrombosis 1
  • Systemic inflammatory states or infection 1
• The meta-analysis cited shows D-dimer has 94% sensitivity for acute aortic dissection, making it useful for exclusion when negative 1

What You Need Now

Immediate Evaluation Required

• Serial troponin measurements at 2-3 hour intervals to determine if values are rising (suggesting acute injury) or stable (suggesting chronic elevation) 1, 4
• 12-lead ECG immediately to identify ST-segment changes, new conduction abnormalities, or ischemic patterns 1, 6
• Urgent echocardiography to assess ventricular function, wall motion abnormalities, and exclude mechanical complications 4, 5
• Arterial blood gas with lactate to better characterize the metabolic acidosis and assess tissue perfusion 5
• Complete metabolic panel including renal function, glucose, and electrolytes to identify metabolic causes of acidosis 1

Critical Diagnoses to Exclude

1. Pulmonary embolism: Can explain all your findings (troponin from RV strain, D-dimer elevation, tachycardia, metabolic acidosis from hypoperfusion) and requires CT pulmonary angiography 1, 5

2. Acute coronary syndrome: Even "barely detectable" troponin with metabolic acidosis suggests possible myocardial injury requiring coronary evaluation 1, 4

3. Myocarditis: Can present with troponin elevation, inflammatory markers, and metabolic derangements, particularly if post-viral 4

4. Sepsis or severe infection: Would explain CRP elevation, metabolic acidosis, and troponin leak from myocardial depression 1, 5

5. Severe dehydration/hypovolemia: POTS patients are prone to volume depletion, which can cause metabolic acidosis and demand ischemia 3, 7

Why This Matters for POTS Patients

• POTS patients have baseline tachycardia and orthostatic stress, but these lab abnormalities suggest an acute superimposed process 2, 3, 8
• Hypovolemia is common in POTS and can precipitate metabolic acidosis, but a base excess of -8 is severe and requires investigation beyond simple volume repletion 3, 7
• The combination of inflammatory markers, cardiac biomarkers, and metabolic acidosis is NOT typical of uncomplicated POTS and mandates evaluation for acute illness 2, 3, 8

Bottom Line

Do not attribute these findings solely to your POTS diagnosis. The constellation of moderate CRP elevation, metabolic acidosis, detectable troponin, and elevated D-dimer represents an acute process requiring urgent medical evaluation. Contact your physician immediately or return to the emergency department for serial cardiac biomarkers, ECG, echocardiography, and consideration of CT angiography to exclude pulmonary embolism 1, 4, 5. The metabolic acidosis alone warrants immediate investigation as it indicates inadequate tissue perfusion or metabolic derangement 1.