MedicalResearch.com Interview with:
David A. Bluemke, MD PhD, MsB
Editor in Chief (2018), Radiology
University of Wisconsin-Madison,
School of Medicine and Public Health
Madison WI 53792
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Heart failure is expected to markedly increase in the United States, because of the aging population (https://www.ncbi.nlm.nih.gov/pubmed/23616602. For patients with congestive heart failure, NT-proBNP is an excellent marker of disease severity. The presence of elevated levels of NT-proBNP also predicts future cardiac events.
For individuals who do not have clinically diagnosed heart failure, the significance of small elevations in NT-proBNP is not known. We hypothesized that these small elevations were related to subclinical elevations in myocardial wall stress. However, in patients with advanced heart disease, we do know that greater myocardial wall stress is associated with histological evidence of fibrosis — i.e., replacement of myocardial muscle by greater fibrotic tissue.
New techniques using MRI can find evidence of expansion of the space between myocytes (the extracellular volume). The most common cause of this expansion is diffuse myocardial fibrosis/ collagen deposition. Using MRI to detect myocardial fibrosis is an advance because MRI is non-invasive (we would not otherwise perform myocardial biopsy for patients without clinically evident disease). Thus we can use MRI to probe the actual composition of myocardial tissue.
Using MRI, we found evidence that individuals in the community (in the MESA study) who had small elevations of NT-proBNP also have evidence of myocardial fibrosis. The mean NT-proBNP levels in the MESA study (1,334 study subjects) was 65 pg/ml. That level is considered to be normal; levels of NT-proBNP of 1200 pg/ ml or greater are found in patients with congestive heart failure.
Of note, the relationship between elevations of NT-proBNP and myocardial fibrosis were independent of multiple risk factors such as age, gender, smoking status, blood pressure, cholesterol levels and diabetes. That is, if the NT-proBNP level was slightly higher (for example, due to increased wall stress), then MRI found an association with greater myocardial fibrosis.