Prognosis after acute myocardial infarction
Dear Sir, Schoeder et al. presented an informative article on "Thallium and indium antimyosin dual-isotope singlephoton emission tomography in acute myocardial infarction to identify patients at further ischaemic risk". The authors showed nicely the ischaemic risk of a highly selected group of patients with thallium-201/indium-111 antimyosin overlap after thrombolysis. They concluded, however, that clear stratification of patients with acute myocardial infarction on the basis of 2Β°~T1/llqn antimyosin SPET alone does not seem possible at the present time. They further pointed out that, to date, this method yields only a small amount of additional information compared with clinical variables, coronary angiography and exercise testing.
However, factors other than ischaemic may play a notable role in the prediction of short-term prognosis. Thus, further parameters besides overlap of perfusion and of necrosis should be taken into consideration for risk stratification. Different markers of necrosis such as technetium-99m pyrophosphate (PYP) may be better suited than 111In antimyosin to the identification of patients at higher risk. Beyond doubt, antimyosin is the most specific tracer for detection of myocardial necrosis. However, 99mTc has much better physical, and PYP, better physiological properties. Owing to the fast blood clearance, imaging is already possible within 0.5-3 h after injection of 99mTc-PYP and as early as 4 h after the onset of acute myocardial infarction. More essentialy, and as a result of the fast clearance, the uptake of 99mTc-PYP depends on the residual flow [2]. This fact, usually regarded as disadvantageous, discloses the unique opportunity for evaluation of the local perfusion state within necrosis (reflow/no reflow, patency of the coronary artery) [24]. Thus, dual use of 2Β°lTI/99mTc-PYP in combination with tomographic technique results in a complete functional image of acute myocardial infarction. As early as 1979 Rude et al. reported on the 99mTc-PYP doughnut pattern in correlationwith clinical complications. More obviously, the 2Β°lT1/99mTc-PYP accumulation pattern identifies patients at high risk for severe heart failure and cardiogenic shock . Holman and coworkers [5] demonstrated the predictive value of size of infarction as measured by 99mTc-PYP tomography. More recently, Zehender et al. showed concomitant right ventricular infarction to be an independent predictor of prognosis after acute myocardial infarction. The findings of the latter group, based on ECG findings, are in accordance with our results using 2Β°1T1/99mTc-PYP tomography .
In conclusion, simultaneous 2Β°lTI/99mTc-PYP tomography can be used for the assessment of acute myocardial necrosis. This technique might provide more comprehensive information than 2Β°~TI and J~In antimyosin imaging.