Novel method for quantitative evaluation of cardiac amyloidosis using (201)TlCl and (99m)Tc-PYP SPECT.

OBJECTIVE: The degree of myocardial technetium-(99m)-pyrophosphate ((99m)Tc-PYP) accumulation in cardiac amyloidosis is conventionally evaluated by the PYP score. This method involves qualitative visual evaluation on two-dimensional images. Here, we performed three-dimensional quantitative analysis using software developed in our laboratory. METHODS: We performed dual myocardial imaging using thallium-(201)-chloride ((201)Tl-Cl) and (99m)Tc-PYP in cases of suspected cardiac amyloidosis and calculated the PYP accumulation rates of all myocardial pixels showing (99m)Tc-PYP accumulation. We defined this procedure as quantitative evaluation of the degree of (99m)Tc-PYP accumulation in the myocardium. Patients were divided into two groups with and without a diagnosis of cardiac amyloidosis, and we examined the PYP accumulation rates in both groups. In addition, we examined the PYP scores of the two groups by conventional qualitative evaluation. RESULTS: The PYP scores of the cardiac amyloidosis group were significantly higher than those of the other group. The PYP accumulation rates of the cardiac amyloidosis group were significantly higher than those of the other group. There were significant differences in the PYP accumulation rate and PYP score between the two groups. There was considered to be a threshold between the two groups in the case of the PYP accumulation rate. CONCLUSIONS: When the threshold of the PYP score was defined as 3+ and that of the PYP accumulation rate as 41.5 %, the sensitivity of the PYP score and PYP accumulation rate was 84.6 %. However, the specificity of the PYP accumulation rate was higher than that of the PYP score. Quantitative evaluation by the PYP accumulation rate of the degree of (99m)Tc-PYP accumulation in the myocardium may be useful in the diagnosis of cardiac amyloidosis.

Technetium-99m pyrophosphate/thallium-201 dual-isotope SPECT imaging predicts reperfusion injury in patients with acute myocardial infarction after reperfusion.

PURPOSE: Microcirculatory failure after reperfusion is clinically indicated to cause reperfusion injury whereas excessive intracellular calcium ion overload is experimentally proved as a key mechanism of reperfusion injury. We hypothesized that technetium-99m ((99m)Tc) pyrophosphate (Tc-PYP) uptake in injured but viable infarct-related myocardium with preserved myocardial perfusion after reperfusion estimated by thallium-201 ((201)Tl) uptake would be associated with final functional recovery. METHODS: Dual-isotope Tc-PYP/(201)Tl single-photon emission computed tomography (SPECT) was performed 2 days after successful reperfusion therapy in patients with first acute myocardial infarction, and 50 patients (63 +/- 13 years old, female 22%) with preserved (201)Tl uptakes of > or = 50% in reperfused myocardium was followed for 1 month. Tc-PYP uptake was assessed as the heart-to-sternum (H/S) ratio. Two-dimensional echocardiography was also performed 2 days and 1 month after reperfusion to evaluate functional recovery. RESULTS: High Tc-PYP uptake, defined as the H/S ratio > or = 0.81, was predictive of chronic phase no functional recovery (73.7% in 14 of 19 patients with high uptake vs 16.1% in five of 31 patients without those, p < 0.0001). After adjustment for potential confounding variables, including electrocardiographic persistent ST segment elevation at 1 h after reperfusion, high Tc-PYP uptake remained independently predictive of no functional recovery with odds ratio of 8.7 (95% confidential interval = 2 to 38.7; p = 0.005). CONCLUSION: High Tc-PYP uptake in reperfused but viable infarct-related myocardium was a powerful predictor of no functional recovery, which may reflect excessive intracellular calcium ion overload caused by reperfusion injury. Tc-PYP/(201)Tl dual-isotope SPECT imaging can provide prognostic information after reperfusion.

Implications of delayed image on simultaneous thallium-201/technetium-99m pyrophosphate dual emission computed tomography early after acute myocardial infarction.

This study aimed investigate whether thallium-201 and technetium-99m pyrophosphate dual rest-redistribution emission computed tomography early after intracoronary thrombolysis may provide supplementary information for the management of patients with acute myocardial infarction. Fifty patients who received intracoronary thrombolysis underwent simultaneous dual emission computed tomography 3 days after first acute myocardial infarction. All patients who had a technetium-99m pyrophosphate accumulation were selected. Thallium-201/technetium-99m pyrophosphate overlap in the initial and delayed images early after intracoronary thrombolysis identified successful recanalization with sensitivities of 68% and 90% (p < 0.05), specificities of 47% 79% (p < 0.05), positive predictive accuracies of 68% and 88%, negative predictive accuracies of 47% and 80% (p < 0.05), and overall accuracy of 60% and 86% (p < 0.01), respectively. The patients were divided into 3 groups according to the change in thallium-201 uptake from the initial image to the delayed image on dual emission computed tomography: 20 patients had no change in thallium-201 uptake (fixed type), 16 had increases in thallium-201 uptake (redistribution type), and 14 had decreases in thallium-201 uptake (reverse redistribution type). The number of patients with successful recanalization was significantly higher in the redistribution type than in the other types (redistribution type vs reverse redistribution type or fixed type; p < 0.01, respectively). In the redistribution type a frequency of reinfarction in the same infarcted area during the hospital course was significantly higher than in the other types (redistribution type vs reverse redistribution type or fixed type; p < 0.05, respectively), which was mainly due to the patients having high grade residual stenosis. Thus, a thallium-201/technetium-99m pyrophosphate overlap in the delayed image early after acute myocardial infarction can be used as an index for predicting successful early recanalization and probably viable myocardium. In addition, the redistribution patterns on thallium-201 emission computed tomography early after intracoronary thrombolysis can be helpful in identifying patients with successful early recanalization and a high risk subset.

Skeletal muscle fiber type does not predict sensitivity to postischemic damage.

Because the three distinct fiber types of skeletal muscle have significant metabolic differences, the predominant fiber type in a muscle may influence its sensitivity to injury from ischemia and reperfusion. The few studies to address this issue have been conflicting. We explored possible differences in the sensitivity of fiber types to ischemia/reperfusion injury with an isolated rat hindlimb preparation perfused with an albumin-enriched Krebs buffer. Following 120 min of ischemia and 60 min of reperfusion, the tibialis anteriorwhite, tibialis anteriorred, soleus, and plantaris muscles were assessed for injury by examining three parameters: skeletal muscle injury (via 99Tc-pyrophosphate), microvascular injury (via 125I-albumin), and tissue water content. There was no consistent correlation between fiber type and sensitivity to postischemic injury. Both the soleus (slow twitch) and plantaris (fast twitch) muscles sustained similar significant injury: muscle damage was 133 and 167% greater than controls, and microvascular damage 96 and 91% greater than controls, respectively. However, other fast twitch muscles (tibialis anteriorwhite and tibialis anteriorred) exhibited no significant injury. Both injured muscles were in the posterior compartment while the uninjured muscles were in the anterior compartment. Regional flow as measured by microspheres revealed no correlation between postischemic flow and muscle injury, microvascular injury, or compartmental location. Skeletal muscle fiber type was not consistently predictive of its sensitivity to ischemia/reperfusion-induced injury. Compartmental location may have played an as yet unknown role in modulating vulnerability to postischemic damage.

Relation of technetium-99m pyrophosphate accumulation to time interval after onset of acute myocardial infarction as assessed by a tomographic acquisition technique.

Technetium-99m pyrophosphate (Tc-99m PYP) myocardial scintigraphy was performed in 110 clinically stable patients with acute or healed acute myocardial infarction (AMI). Tomography was performed 12 hours to 7 days (group A), 7 to 30 days (Group B), 1 to 6 months (Group C) and after greater than 6 months (group D) after AMI. All 40 patients in group A, 9 of 31 in group B, 1 of 22 in group C, and no patient (0 of 17) in group D had a pathologic Tc-99m PYP tomogram. Relative Tc-99m PYP accumulation within the area of infarction was measured as infarct zone to blood pool ratio, which decreased significantly (p less than 0.001) from group A (1.54 +/- 0.39) to group B (0.89 +/- 0.24), group C (0.8 +/- 0.19) and group D (0.76 +/- 0.13). These data were confirmed by sequential scintigraphy in 17 patients. It is concluded that a persisting Tc-99m PYP uptake is rarely found greater than 1 month after AMI using tomographic imaging techniques in clinically stable patients with coronary artery disease. Positive results on Tc-99m PYP tomography are a reliable indicator of AMI. Thus, Tc-99m PYP tomography is not only a sensitive but also a specific imaging technique for AMI, which might be especially useful for diagnosis of reinfarction.

A comparison of radiotracer and biochemical methods for the quantitation of experimental myocardial infarct weight: in vitro relationships.

Anterior myocardial infarction (MI) was produced in conscious dogs to evaluate the relationships among: a) cardiac technetium-99m stannous pyrophosphate (TcPPi) accretion, b) creatine phosphokinase (CPK) depletion, and c) postmortem MI weight, infarct structure, and histology. In vitro, there was a close relationship between measured MI weight and MI weight calculated by the TcPPi accretion (r = 0.96) or CPK depletion (r = 0.93) in representative "cross-sectional" MI samples. Cardiac TcPPi accretion and CPK depletion showed a curvilinear relationship over the spectrum of tissue samples. Adjacent to infarcts, there was marked TcPPi uptake and modest CPK depletion where histology suggested ischemia without infarction. Within infarcts, microscopically visible calcium was rare in this series, suggesting little intracellular calcium accumulation, insensitivity of the von Kossa staining technique, and/or other cellular mechanisms to account for Tc-PPi uptake in this conscious dog model without reperfusion.