A phantom assessment of cold stomach-related artifacts in myocardial perfusion imaging.

AIM: To study the effect of a 'cold stomach', caused by either air or water, on Tl-201 and Tc-99m myocardial perfusion single-photon emission computed tomography (MPS). MATERIALS AND METHODS: A stomach insert was created in a thorax phantom. MPS was performed with Tl-201 or Tc-99m. MPS was recorded with an empty stomach, a stomach filled with 0.5 or 1 l of water, or with 0.5 or 1 l of air. For Tc-99m, transmission scans for attenuation correction (AC) were also obtained. RESULTS: In Tl-201 MPS, filling the stomach with air caused an increase of activity in the infero-lateral wall, whereas filling the stomach with 1 l of water resulted in a slight decrease of activity in the infero-lateral wall. In Tc-99m MPS, filling the stomach with air also resulted in a higher activity in the infero-lateral wall, which normalized when AC was applied. Filling the stomach with water caused no marked differences in Tc-99m MPS with or without AC. CONCLUSION: A stomach filled with large amounts of water causes (mild) infero-lateral wall defects in Tl-201 MPS; a stomach filled with air causes a strong scintigraphic overexpression of the infero-lateral wall in both Tl-201 and Tc-99m MPS which can be compensated with AC.

Myocardial perfusion defects in right ventricular apical pacing are caused by partial volume effects because of wall motion abnormalities: a new model to study gated myocardial SPECT with the pacemaker on and off.

BACKGROUND: Myocardial perfusion defects have been shown in patients with abnormal intraventricular conduction. These defects have been ascribed to regional differences in myocardial blood flow caused by the abnormal activation. This proof of the concept study assesses the effects of abnormal electrical activation and subsequent wall motion abnormalities of the left ventricle on myocardial perfusion in a pacing model. METHODS: Fourteen patients with normal atrio-ventricular (AV) and intraventricular conduction with a right ventricular apical (RVA) pacemaker for brady-tachycardia syndrome were studied to allow for intrapatient comparison. Tc-sestamibi was injected in atrial inhibited (AAI) pacing mode allowing uptake during normal intraventricular conduction. Imaging was performed with AAI pacing and the second image was acquired directly after the first scan with AV pacing with a short AV-interval ensuring complete AV pacing with abnormal ventricular activation patterns (RVA pacing). Left ventricular ejection fraction (LVEF), wall motion score and myocardial perfusion score (SSS) were assessed with gated single photon emission computed tomography (SPECT) during normal conduction (AAI) and with RVA pacing. RESULTS: Left ventricular ejection fraction was normal in all patients. During AAI, three of 14 patients showed wall motion abnormalities, mean wall motion score 0.9+/-1.8 with a mean SSS 0.6+/-1.5 increasing to 4+/-6.2 and 3.6+/-5.8 (P<0.01), respectively during RVA pacing. Wall motion abnormalities were found in the apex, inferior, inferoseptal and septal walls. CONCLUSION: Despite a fixed amount of tracer activity in the myocardium, larger and more perfusion defects were visible during RVA pacing compared with normal conduction. The site and severity of the perfusion defects correlates with abnormal wall motion because of this pacing mode. This implies that abnormal wall motion is at least partly responsible for the apparent myocardial perfusion defects.