Implications of abnormal right ventricular thallium uptake in acute myocardial infarction

Proposal for a Display Method for Myocardial Single Photon Emission Computed Tomography Based on Left Ventricular Volume

Bull's eye view for the display of myocardial single-photon emission computed tomography (SPECT) 3-D perfusion maps does not reflect left ventricular (LV) volume, an important parameter. We created and evaluated a myocardial SPECT display method that reflects the LV volume.Using Digital Imaging and Communications in Medicine data, short-axis slices from the apex to the base were reconstructed and interpolated into 0.5-mm thickness. We obtained the radial lengths at 1° intervals throughout 360°, and calculated the length of the LV long axis and half circumference (1/2 circ). Myocardial perfusion was displayed as 2 ellipsoidal developments that exhibited the left anterior descending coronary artery (LAD) and non-LAD regions. We created a system that can display these processes on a personal computer. Myocardial SPECT data from 526 individuals without heart disease were analyzed. The long axis and 1/2 circ were compared with the body size, LV end-diastolic diameter (LVDd) obtained by echocardiography, and the end-diastolic volume (EDV) obtained by electrocardiogram-gated SPECT analysis. The 1/2 circle correlated with the LVDd and EDV. The images obtained allowed a diagnosis comparable to that made using the conventional coordinate display system.The new myocardial display reflects ischemia and LV volume within a single image, which cannot be achieved with conventional SPECT image display. Additional studies of this display system are required to allow its application to patients with heart disease.

Right and left ventricular uptake with Rb-82 PET myocardial perfusion imaging: markers of left main or 3 vessel disease

BACKGROUND

Relative myocardial perfusion imaging may underestimate severity of coronary disease (CAD), particularly in cases of balanced ischemia. Can quantification of peak left (LV) and right (RV) ventricular Rb-82 uptake measurements identify patients with left main or 3 vessel disease?

METHODS

Patients (N = 169) who underwent Rb-82 PET MPI and coronary angiography were categorized as having no significant coronary stenosis (n = 60), 1 or 2 vessel disease (n = 81), or left main disease/3 vessel disease (n = 28), based on angiography. Maximal LV and RV ventricular myocardial Rb-82 uptake was measured during stress and rest.

RESULTS

Failure to augment LV uptake by >or= 8500 Bq/cc at stress, predicted left main or 3 vessel disease with a sensitivity of 93% and specificity of 61% (area under curve = 0.83). A >or=10% increase in RV: LV uptake ratios with stress over rest was 93% specific (area under curve = 0.74) for left main or 3 vessel disease. These indices incrementally predicted left main or 3 vessel disease compared to models including age, gender, cardiac risk factors, and summed stress and difference scores.

CONCLUSION

Quantifying maximal rest and stress LV and RV uptake with PET myocardial perfusion imaging may independently and incrementally identify patients with left main or 3 vessel disease.

Planar imaging techniques used with technetium-99m sestamibi to evaluate chronic myocardial ischemia

The results of published and some unpublished studies comparing planar imaging performed with 2 radionuclides, thallium-201 (T1-201) and technetium-99m (Tc-99m) sestamibi, are reviewed. The average sensitivity for the detection of coronary artery disease (CAD) in studies involving 594 patients was 85% (range 73 to 96%). The average sensitivity for individual vessels was 65% (range 60 to 70%). The average segmental concordance between T1-201 and Tc-99m sestamibi was 89%. End-diastolic gated perfusion images improved the concordance between Tc-99m sestamibi and angiography in 22 patients from 83.4 to 87%. Semiquantitative analysis increased the concordance between T1-201 and Tc-99m sestamibi from 89 to 91%. Ventricular function derived from gated Tc-99m sestamibi perfusion images showed a significant correlation with echocardiography (n = 62, r = 0.85); with angiography (n = 70, r = 0.91); and with equilibrium radionuclide ventriculography (n = 18, r = 0.86). The ratio of lung to left ventricle uptake and the ratio of right ventricle to left ventricle uptake was assessed. Eight of 52 patients had an abnormally elevated lung index (greater than 42%) and these patients had the most severe CAD. Six of the 52 patients had an abnormally elevated right ventricular index (greater than 56%) and these patients had more severe CAD.

Exercise myocardial perfusion scintigraphy with technetium-99m methoxy isobutylisonitrile: a comparative study with thallium-201

The evaluation of technetium-99m methoxy isobutylisonitrile for the diagnosis of coronary artery disease requires comparative validation against thallium-201, the established perfusion imaging agent. We have compared myocardial and lung uptake of both radiotracers following maximal exercise in 52 patients: 40 with angiographically proven coronary disease. Qualitative and quantitative image analysis showed the diagnostic sensitivity of technetium-99m methoxy isobutylisonitrile to compare favourably with that of thallium-201 as reflected by the mean number of ischaemic segments identified: 5.6 +/- 2.5 vs 4.8 +/- 2.1 by qualitative analysis, and 5.7 +/- 3.2 vs 5.0 +/- 2.6 segments by quantitative analysis. More reversibly ischaemic segments per patient were identified with technetium-99m methoxy isobutylisonitrile than with thallium-201: 3.6 +/- 2.3 vs 1.8 +/- 1.9. There was a higher exercise myocardial to background count ratio with technetium-99m methoxy isobutylisonitrile: 3.16:1 vs 2.58:1, and the mean exercise lung uptake normalised to left ventricular uptake ('lung index'), was lower for technetium-99m methoxy isobutylisonitrile than for thallium-201 (36 +/- 8% vs 40 +/- 10%). Five of the six patients with abnormal elevation of the thallium-201 exercise lung index also had elevation of the technetium-99m methoxy isobutylisonitrile exercise lung index, and all had extensive coronary artery disease. These results indicate that technetium-99m methoxy isobutylisonitrile is at least as effective as thallium-201 for detecting exercise induced myocardial ischaemia. However, technetium-99m methoxy isobutylisonitrile provides a better image quality and may be a more sensitive marker of defect reversibility. For both radiotracers lung uptake is increased with extensive coronary artery disease and measurement of this variable provides prognostic information.