Cardiac biomarkers at Poliklinika Analiza

What is NT-proBNP and when is it used?

Natriuretic peptides are key proteins that regulate circulation. In addition to regulating blood pressure, they are important because they prevent heart muscle hypertrophy. B-type natriuretic peptide belongs to this group of peptides, and its precursor, NT-proBNP is a cardiac biomarker used in diagnosing and monitoring treatment success in cardiac weakness, or heart failure.

Values >300 pg/mL are elevated, and the result is interpreted according to the clinical presentation and other investigations performed. Other diseases can also affect NT-proBNP values: this cardiac biomarker is elevated in kidney failure, diabetes and acute coronary syndrome, and is lower in overweight patients.

The most important indication for measuring NT-proBNP is dyspnoea (difficulty breathing, breathlessness). Elevated NT-proBNP values suggest a cardiac cause of breathing difficulty with a sensitivity of approximately 97%. With elevated values, the patient should be referred for further cardiac investigations (ECG, echocardiography).

Normal NT-proBNP values generally rule out heart failure, and the patient is then directed towards investigating non-cardiac causes of breathing difficulty, such as asthma or pneumonia. NT-proBNP is a useful prognostic marker in patients with chronic heart failure.

What is H-FABP ?

H-FABP is a relatively newer biomarker also used in diagnosing heart failure and as a predictor of cardiovascular mortality risk. Values >7 ng/mL are considered elevated and must be interpreted alongside the clinical presentation and other diagnostic investigations. H-FABP is considered an early indicator of heart muscle injury. This biomarker can also detect minor heart muscle injuries.

What is cardiac troponin?

Cardiac troponins are structural (binding) proteins, a small fraction of which are present as free troponins in the cytosol: 6-8% for cTnT and 3.5% for cTnI. During a heart attack, heart muscle cell membranes rupture, releasing larger amounts of troponin into the blood, where they can therefore be detected as elevated. Troponin measurement is considered 100% sensitive if measured 6-12 hours after the onset of chest pain.

We offer cTnI. Values >1 pg/mL are elevated and are interpreted according to the clinical presentation and other diagnostic investigations (particularly ECG). Troponin is predominantly used in emergency services. A patient with clear symptoms and signs of acute coronary syndrome, which includes unstable angina, ST-segment elevation myocardial infarction on ECG (STEMI) and non-ST-segment elevation myocardial infarction on ECG, should be referred immediately to the nearest emergency department, where troponin is measured under continuous medical supervision.

When and for whom are these investigations recommended?

Our triad of cardiac biomarkers (NT-proBNP, cTnI, H-FABP) is recommended for all cardiac patients (chronic heart failure, angina pectoris, implanted pacemaker, follow-up after a heart attack, follow-up after stent placement or coronary bypass surgery) who want more detailed information about their heart muscle health and are not acutely ill. In this case, silent myocardial ischaemia can be detected early, before symptoms develop; for example, elevated cTnI and H-FABP may indicate early heart muscle injury even in patients who have not yet developed symptoms. It is then reasonable to refer such a patient to the nearest hospital emergency department.

This test is in no way intended for patients with clear symptoms and signs of acute heart failure or an acute heart attack (difficulty breathing, marked weakness, pain in the left arm, severe chest pain and similar), because in that case they must attend the nearest emergency department IMMEDIATELY and WITHOUT DELAY; cardiac biomarkers are then measured in hospital under continuous medical supervision!

REFERENCES:

1. Novack ML, Zubair M. Natriuretic Peptide B Type Test. 2023 Apr 23. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 32310596.

2. Rezar, R., Jirak, P., Gschwandtner, M., Derler, R., Felder, T. K., Haslinger, M., Kopp, K., Seelmaier, C., Granitz, C., Hoppe, U. C., & Lichtenauer, M. (2020). Heart-Type Fatty Acid-Binding Protein (H-FABP) and its Role as a Biomarker in Heart Failure: What Do We Know So Far?. Journal of clinical medicine, 9(1), 164. https://doi.org/10.3390/jcm9010164

3. Rezar R, Jirak P, Gschwandtner M, Derler R, Felder TK, Haslinger M, Kopp K, Seelmaier C, Granitz C, Hoppe UC, Lichtenauer M. Heart-Type Fatty Acid-Binding Protein (H-FABP) and its Role as a Biomarker in Heart Failure: What Do We Know So Far? J Clin Med. 2020 Jan 7;9(1):164. doi: 10.3390/jcm9010164. PMID: 31936148; PMCID: PMC7019786.

4. Stark M, Kerndt CC, Sharma S. Troponin. 2023 Apr 23. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 29939582.

Author: Domina Petrić, MD

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