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

Potential utility of SPECT/CT with 99mTc-Tektrotyd for imaging of post-myocardial infarction inflammation

BACKGROUND

There is a need to develop methods for post-myocardial infarction (MI) inflammation monitoring. Scintigraphy with somatostatin receptor targeted radiotracers has potential in this field. The purpose was to study the association of 99mTc-Tektrotyd uptake intensity in MI area with heart contractility indices over 6-month follow-up.

METHODS

Fourteen patients with acute ST-segment elevation anterior MI (STEMI) were examined with 99mTc-Tektrotyd SPECT/CT, myocardial perfusion scintigraphy (MPS) at rest, cardiac magnetic resonance imaging (cMRI) and transthoracic echocardiography (TTE). Scintigraphic results were compared with 6-month TTE indices.

RESULTS

On the 7th day after a MI onset, cardiac 99mTc-Tektrotyd uptake was found in 7 of 14 patients. Median of 99mTc-Tektrotyd SUVmax was 1.59 (1.38; 2.83), the summed rest score (SRS) was 11 (5; 18), infarct size (by cMRI)-13.15 (3.3; 32.2) %. 99mTc-Tektrotyd SUVmax strongly correlated with 6-month heart contractility indices (r = 0.81, P < 0.05 for the end diastolic volume; r = 0.61 P < 0.05 for Δ end diastolic volume), with SRS (r = 0.85, P < 0.05) and infarct size (by cMRI) (r = 0.79, P < 0.05).

CONCLUSION

The intensity (SUVmax) of 99mTc-Tektrotyd uptake in the area of recent MI directly depends on the size of ischemic myocardial injury and correlates with changes of heart contractility indexes over the 6 month follow-up.

Detection of acute myocarditis by ECG-triggered PET imaging of somatostatin receptors compared to cardiac magnetic resonance: preliminary results

Somatostatin receptors are overexpressed by inflammatory cells but not by cardiac cells, under normal conditions. This study assesses the detection of acute myocarditis by the ECG-triggered digital-PET imaging of somatostatin receptors (68Ga-DOTATOC-PET), as compared to Cardiac Magnetic Resonance (CMR) imaging, which is the reference diagnostic method in this setting.

METHODS

Fourteen CMR-defined acute myocarditis patients had a first 15-minutes ECG-triggered 68Ga-DOTATOC PET recording, 4.4 ± 3.0 days from peak troponin, and 10 had a second 4.3 ± 0.3 months later. Myocardial/blood SUVmax ratio was analyzed relative to the normal upper limit of 2.18, which had been previously determined from oncology 68Ga-DOTATOC-PET recordings of patients with a similar age range as the myocarditis patients.

RESULTS

An increased myocardial 68Ga-DOTATOC uptake relative to blood activity was invariably observed during the acute phase. SUVmax ratio exceeded 2.18 in all patients during the acute phase but also in 3/10 patients at 4-months, at a time when there were no more signs of active inflammation on CMR. A residual myocardial 68Ga-DOTATOC uptake was still observed on all gated-PET cine loops at 4-months.

CONCLUSION

These preliminary results suggest that 68Ga-DOTATOC ECG-triggered digital-PET may be as sensitive as CMR at detecting myocarditis during the acute phase and more sensitive at later stages.