MAGNETIC RESONANCE IMAGING IN THE DIAGNOSIS OF THE HEART LESIONS IN PATIENTS WITH ACROMEGALY

Background: Acromegaly is a disease caused by pathologic hypersecretion of growth hormone and insulin-like growth factors. Independent of other cardiovascular disorders, acromegalic cardiomyopathy develops in patients with acromegaly. According to the published data, it manifests by a triad of symptoms, such as hypertrophy, edema and fibrosis of the myocardium. Myocardial fibrosis (diffuse interstitial) develops due to persistent excess of growth hormone and a gradual loss of the heart muscle architectonics. It is difficult to define the rate of cardiac fibrosis in acromegalic cardiomyopathy, because studies in this area are scarce and include small patient numbers.

Aim: To develop an algorithm for cardiac magnetic resonance imaging (CMR) for identification of the key variants of myocardial abnormalities in patients with acromegaly.

Materials and methods: From 2013 to 2015, the CMR was performed in 27 patients aged from 23 to 69 years with a clinical diagnosis of acromegaly. The disease duration ranged from 4 to 38 years. The MRI investigations were performed on a MR scanner General Electric 1.5 T Optima MR450w GEM using cardiac surface coils, with contrast agents with the active substance content of 0.5 mmol / mL, at a dose of 0.3 mL / kg. Synchronization with the heart rhythm was conducted under standard VCG leads. The assessment was done in the standard planes (2- and 4-chamber, short-axis) using sequences of film loops. To identify structural myocardial abnormalities typical for acromegalic cardiomyopathy (hypertrophy, edema and interstitial fibrosis), we used a specialized protocol that in addition to the well known diagnostic sequences included new diagnostic target assessments, such as T1-mapping with a set of 30 indicators of the time inversion).

Results: The semiotics of heart abnormalities in acromegalic cardiomyopathy manifested as myocardial hypertrophy, detected in 20 (74%) patients aged 59–62 years, with disease duration from 5 to 14 years (mild, in 9, moderate, in 9, severe, in 2 cases ) and signs of interstitial fibrosis in 100% of cases. No signs of myocardial edema were found. Calculation of the difference in T1 time values obtained from the mapping of all acromegaly patients showed a change in the relaxation time of various degrees, suggesting the presence of interstitial fibrosis. Initial statistical analysis of the data revealed a significant negative correlation between T1 relaxation time of the left ventricular myocardium and growth hormone levels (r = -0.3929, p < 0.05), as well as a significant negative correlation between the difference in the left ventricular T1 relaxation time before and after administration of the contrast and growth hormone levels (r = -0.4388, p < 0.05).

Conclusion: CMR algorithm including a cine sequence seems to be the most informative in determination of the main types of myocardial abnormalities in patients with acromegaly. It allows an assessment of the functional status and myocardial hypertrophy, black blood sequence and fat saturation that help to identify myocardial edema; T1-mapping technique for the search for diffuse interstitial myocardial fibrosis.