Association of coronary microvascular dysfunction and cardiac muscle injury in acute myocardial infarction: results of comparison of dynamic SPECT and cardiac MRI.

Aim      To study the interrelation of changes in coronary microcirculation by data of dynamic single photon emission computed tomography (SPECT) and myocardial injury by data of magnetic resonance imaging (MRI) in patients with acute myocardial infarction (AMI).Material and methods  The study included patients admitted to the emergency cardiology department with new-onset AMI. Contrast-enhanced cardiac MRI was performed for all patients on day 2-7 of admission. Dynamic SPECT of the myocardium with evaluation of semiquantitative and quantitative parameters of perfusion was performed on day 7-10.Results All patients were divided into two groups based on the type of MR contrast agent accumulation: 1) patients with the ischemic type of contrast enhancement (n=34; 62 %); 2) patients with the non-ischemic type of contrast enhancement (n=21; 38 %). According to data of myocardial perfusion scintigraphy (MPS), the group of ischemic MR pattern had larger perfusion defects at rest and during a stress test. Moreover, this group was characterized by lower global stress-induced blood flow and absolute and relative myocardial flow reserve (MFR). When the study group was divided into patients with transmural (n=32; 58 %) and non-transmural (n=23; 42 %) accumulation of the MR-contrast agent, lower values of global stress-induced blood flow and of absolute and relative MFR were observed in the group of transmural MR-enhancement pattern. A moderate inverse correlation was found between the stress-induced myocardial blood flow and the volume of myocardial edema (r= -0.47), infarct area (r= -0.48) and microvascular obstruction area (r= -0.38).Conclusion      The variables of dynamic SPECT characterizing microcirculatory disorders that are independent on or due to injuries of the epicardial coronary vasculature reflect the severity and depth of structural changes of the myocardium in AMI. In this process, quantitative variables of myocardial perfusion are interrelated with the myocardial injury more closely than semiquantitative MPS indexes. The findings of the present study can also contribute to the heterogenicity of a patient group with acute coronary syndrome and AMI. Further study is required for understanding the prognostic significance of dynamic SPECT parameters.

Interstitial Edema of the Interatrial Septum in Patients with Atrial Fibrillation and Chronic Heart Failure.

We studied the presence of interstitial edema of the interatrial septum in patients with chronic heart failure (CHF) with atrial fibrillation (n=23) or without rhythm disturbances (n=9). The intensity of the MRI signal of the interatrial septum, interventricular septum, and skeletal muscle by T2-weighted MRI and the enhancement index of interatrial septum (the ratio of the signal intensity of the interatrial septum to the signal intensity of the skeletal muscle) were evaluated. The enhancement index of interatrial septum ⩾2 was regarded as an MRI sign of myocardial edema. The enhancement index of interatrial septum in patients with persistent atrial fibrillation was 2.4 (2.21; 2.69) and was higher than in CHF patients with paroxysmal atrial fibrillation and in CHF patients without arrhythmias and surpassed the control values (p<0.05), which indicates the presence of MRI signs of edema of the myocardium of the interatrial septum. The obtained data confirm the presence of myocardial edema of the interatrial septum in CHF patients and persistent form of atrial fibrillation, which expands the understanding of the pathogenesis of this condition.

Subacute myocardial infarction detected by technetium-99m-labeled somatostatin analog scintigraphy.

Recently, the applicability of somatostatin receptor-targeted (SSTR-t) radiotracers for post-ischemic myocardial inflammation imaging has been shown using PET. Currently, there are no studies which demonstrate ability of SPECT and technetium-99m SSTR-t radiotracers to detect inflammation, which appears in response to acute myocardial infarction (AMI). A case of 51-year-old male with acute anterior myocardial infarction (AMI) with ST elevation has been presented. This patient on 7th day after AMI onset underwent SPECT/CT (by cardiac cadmium-zinc-telluride gamma-camera) with 99mTc-Tectrotide, cardiac MRI with gadolinium and, on 9th day after AMI, myocardial perfusion scintigraphy (MPS) at rest. Clear myocardial uptake of 99mTc-Tectrotide, predominantly in apical and intermediate anterior wall of left ventricle was detected. The uptake matched with areas of hypoperfusion (by SPECT) and myocardial injury (by MRI). This case demonstrated the applicability of technetium-99m-labeled SSTR-t radiotracers for post-infarction inflammation imaging. Currently assumed, that SSTR-t radiotracers reflect an increased number of activated macrophages infiltrating infarcted myocardium, which is not possible using any other imaging technique. Thus, potentially, SSTR scintigraphy may be useful for diagnosis and monitoring of myocardial post-infarction inflammation as well as for anti-inflammatory image-guide therapy assessment.