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Rochela Vázquez, Luis M.; Batista Cuéllar,
Stusser Beltranena, Rodolfo; Pérez Valdés, Marilyn;
Peña Quián, Yamile; Hernández Cairo, Abel;
Coca Pérez, Marco A.
Clinical Research Center, Havana City, Cuba
Different criteria exist with relationship to the efficacy of the 99mTc-MIBI in relation to the TL201 to define the percent of infarcted area by means of perfusion myocardial SPECT with study of myocardial viability.
Objective: To compare the efficacy of 99mTc-MIBI with the TL201 as standard radiotracer for these studies.
Material and method: It was studied a sample of 166 patients with antecedents of myocardial infarction (MI) that underwent SPECT with TL201 (n =66) or 99mTc-MIBI (n =66), and 34 patients that had SPECT with both radiotracers that included effort y/o rest, redistribution and reinjection y/o rest-nitroglycerine. Of these last ones, each separate study was analyzed, increasing both groups to 100 studies, without significant differences [(p > .05)] for age and % of reached heart frequency (see ).
Results: Comparing both groups
(with similar proportion of IM Q and no-Q similar [p > .05]), it was observed
that the means of the 6 analyzed variables were similar with both radiotracers
without significant differences ([p > .05] see ).
Conclusion: Both radiotracer were equivalent for the study of the percent of infarcted area with independence of the type of MI Q and no-Q.
Different approaches exist with relationship to the effectiveness of the 99mTc-MIBI with regard to the TL201 to define the percent of infarcted area (IFA) of the Left Ventricle (LV) by means of the SPECT of Myocardial Perfusion with study of Viability, although authors that have already studied this, but without differential the type of MI (1,2) and they affirm that its capacity to determine the IFA is similar to that of the TL201 (1,2,3). In the case of the TL201 it is a radiotracer (RT) of older use and therefore better studied in the determination of the IFA in that which authors outline that it is adapted (1) and it has even been compared with the PET (3,4) and autopsy (1,5) for what we will use it as gold standard. It motivates us to this comparison the growing use of marked RT with 99mTc due to the advantages that these products present like they are a bigger operability for their work, for not having to pass the patient directly to the acquisition of the images, possibility to completely recover to the later patient to the stress (period vulnerable to arrhythmias), bigger emission energy (150kev) what diminishes the probability of false positive for attenuation (mammary, diaphragmatic etc) and it produces better image quality, possibility of carrying out studies of gated myocardial perfusion which contribute additional functional information to the perfusion one (3).
Compare the efficiency of the SPECT of myocardial perfusion with study of viability with 99mTc-MIBI with regard to the one carried out with TL201 in the patients with MI.
MATERIAL AND METHOD
One carries out the exploratory study of 166 patients (masculine =138, 83.13%) with antecedents of MI (of those which 77, 46.38% was Q-MI), with an average of age of 51,7años, a percent of reached heart frequency of 84.9% and 31 patients (18.6%) with trombolisis. All had been carried out SPECT of myocardial perfusion with study of viability that include Effort and/or Rest, Redistribution and Reinjection y/o Rest-nitroglycerine (NTG) of those which 66 (37.79%) they were carried out with TL201, 66 using 99mTc-MIBI and 34 (20,48%) they had carried out studies with both RT, of these last ones we analyzes each study for separate that which the sample increased to 100 studies with each RT what facilitate to have a total of 200 studies for the analysis. The patients that had among their antecedents causes of false positive gammagraphics were excluded.
In this sample of 200 studies we observe that the age average was of 51,7años and the percent of reached heart frequency was of 85.41% so we can affirm that these studies were useful. This sample was divided in Grupo1, studies with TL201 and Group 2, studies with 99mTc-MIBI not finding statistically significant differences (SSD) between both groups in these parameters ().
Each group was subdivided in subgroup A (it includes the studies of each group that characteristic Q of MI presents in ECG) and the subgroup B (that includes the studies of each group with absence of characteristic Q of MI in ECG) ().
The subgroup of 34 patients to which are carried
out studies with both RT (to each patients) it allowed us to validate the results
of the work in general to be this ideal sample for this type of comparison.
In the same one they had 27 patients (79.4%) masculine, 21 patients with Q-MI
(61.76%) and 5 patients (4.70%) with trombolisis. The age average was 50.2años,
the average of time lapsed studies between both was of 75días and the
percent of heart frequency reached in general it was 86,78% without SSD between
both RT (TL201 86.18% / 99mTc-MIBI
87.38% p =0.256) for what is considered that in general the studies were useful
from the point of diagnose view.
For the realization of these studies the following protocols of SPECT of myocardial perfusion were used:
1- Effort, Redistribution and Reinjection with TL201: One carries out diagnoses ergometry under the protocol of Bruce with injection from 2,5 to 3mci of TL201 (and continuation of the effort during one minute) when the percent of reached heart frequency was > 85% and/or some approach of detention of the teas appeared, later on spent to the gammacamera (SOPHA DS7) where 32 images of 40 seg each one were acquired, when traveling 180grados in circular orbit from the position right anterior oblique (RAO) until the position left posterior oblique (LPO). The visual field of the gammacamera was equipped with 61 tubes photomultipliers, a thickness of the glass of NaI (Tl) of 3/8inch, and a collimator of general purpose, low energy and parallel holes. The window of energy of 20% was centered on the 80Kev of the pick of rays X 4horas were expected to allow the redistribution of the product and they took images of redistribution under equal conditions, then it was reinjected 1mci additional of TL201 20min were expected and was carried out the acquisition of the images of the reinjection in the same form, later on all the projections were stored in a magnetic disk using a womb of 64 x 64 (16 bit). The images were processed using a filter Hamming-Hann, in a system Sopha-Medical. The cuts tomographics was obtained in the three axes for each phase of the test as well as the corresponding polar images. The algorithm developed in language Forth in a prosecution station SOPHY 20P, divided the image in 13 sectors, calculating the quantity of absolute counts for each segment and comparing them with the maximum value determining, this way the percent that represents the value of the counts of each sector with regard to the maximum that represents 100% of that image.
2- Rest, Redistribution and Reinjection with TL201: Executed in the patients that had contraindicated the ergometry and only differs in that the initial dose was injected in rest.
3- Exercise, Rest and Rest-nitroglycerine: (different day) with 99mTc-MIBI: Was carried out diagnoses ergometry it and injection of the radioisotope in similar conditions and requirements (that for the TL201) injecting a dose from 25 to 30mci of 99mTc-MIBI, later on at the 30min. of the injection the patients drink 8oz of milk rich in fat, beginning the acquisition 60min. after the injection the one which only differs (of the TL201) in that the taking of each image lasted 20 seg. The journey was LPO to RAO and the energy window was centered in the 140kev of the pick of rays X. After 48horas you proceeded to take the images of rest for that which repeated same procedure of administration of the 99mTc-MIBI and acquisition of the images (except the effort that is not carried out) and later at 48horas you proceeded to the study of viability for that which were administered via sublingual 2 pills of NTG 0,4mg and after 10min. then you proceeded to the administration of the 99mTc-MIBI, later proceeded the same as for the taking of rest. As for the storage, prosecution, and interpretation of the images the only difference (with regard to the TL201) it was the use of the filter Butterworth 5/23.
4- Rest and Rest-NTG (different day) with 99mTc-MIBI: Executed in the patients that had contraindicated the ergometry, and only differs of the previous one in that the stress image is obviated.
These protocols are comparable due to using in agreement filters with the dose and the used RT; our work also used the percents of uptake of each sector with regard to that same image, not the number of absolute counts of each sector.
Later on in both patients groups, on the polar image of viability by means of software of DETERMINATION OF AREAS (version 1,0) the perfusions defects corresponding to the percents of uptake < 30% and > 30 < 50% were looked for to determine the percent that represents the area of the defect of uptake of the area of the polar image of the LV that you considers percent of IFA, nevertheless to make sure that those defects were not reversible so much the polar images of stress like of viability they were subjected to a quantification program that divides this in 13 sectors giving the percent of uptake of each sector and that every sector that don't improve more of 10% in the image of viability with regard to the stress you considers fixed or not reversible defect (that correspond with the IFA) therefore for each sector that was reversible and their final uptake was > 30% is subtracted 7.69% to the IFA (therefore is added the IRA) it stops later on to compare both RT for types of MI and to observe if SSD exist as for this aspect. With the objective of determining the percent of IRA calculates the percentage difference (differs among the percent that represents the area of the defect of stress perfusion and the percent that it represents the area of the defect of perfusion of viability) among the perfusion defects with uptake < 50% stress and viability. With the objective of quantifying the severity of the defects of perfusion of the polar image of viability take the smallest uptake percent inside the ranges that we settled down, in the event of not having any defect of perfusion < 50% we take the existent minor.
In the observations made in the 200 studies we see that both RT had similar behavior in front of the MI in general ( ) as well as in the Q-MI and noQ in all the analyzed variables ( and ).
In general we observe in the subgroup of 34 patients don't exist SSD as for the behavior of both RT, only finding SSD in the percent of IFA (99mTc-MIBI 17.6 / TL201 12.9 p =0.48) but with media difference (4.7) very low with regard to the range (0 at 72.6) in which moved this parameter. The same thing was happened to the area percent with uptake < 30% (99mTc-MIBI =5.8% and TL201 =3.8%, p = 0.013, media differentiates = 2, range: 0 at 46.3) (). Similar results observe in front of the noQ-MI, where we only found SSD in the percent of IFA that is bigger with the 99mTc-MIBI (99mTc-MIBI 13.5 / TL201 7.9, p =0.007) but with a small half difference (5.6) with regard to the range (0 at 72.6) in that the dates moved for what we say these differences doesn't have value ( ) .In the behavior of both RT in the Q-MI didn't exist SSD in none of the studied parameters ( ).
The fact of not finding SSD in the comparison among the two RT in the 200 studies when studying their behavior in front of the MI in general, neither when they were subdivided in their two types of MI, it allows us to confirm that outlined by other authors in relation to that the 99mTc-MIBI and the TL201 have the same capacity to determine viability (1, 2, 3, 6, 7 and 8) (and for exclusion IFA because this it is the whole non viable area) but in our work with the contributions that the quantification was carried out in the polar image (which gives a global image of the LV) which has already been validated and used by other authors (1,9), the area of the defects was quantified based on the uptake percents that is to say a completely quantified study (for that this free of subjectivity some), in our study both RT has study of viability, aspect this very important one so that they are comparable, because this demonstrated the importance of the Reinjection in the case of the TL201 (1) and the NTG in the case of the 99mTc-MIBI in the study of the viability (3, 6, 7, 9, 10, 11, 12), because otherwise this it can be undervalued and therefore overestimated the IFA, the behavior of both RT is also studied in front of each type of MI.
In the analysis of the subgroup of 34 patients (that consider it the ideal for this comparison since each patient was studied with the two RT) in general and in the MI-noQ one observes bigger area percent with uptake £30% and percent of IFA with 99mTc-MIBI that with TL201 that which can have relationship with the statements of some authors that the TL201 has bigger capacity to determine myocardial severely hypoperfused myocardial but viable that the 99mTc-MIBI (2, 14) that which makes that they appear bigger the areas of having not myocardial viable with the 99mTc-MIBI and in the case of the noQ-MI, we say SSD is due to that to be most of this type of MI. are subendocardic has viable myocardial but severely hypoperfused to its surroundings where it arrives the TL201 better that the 99mTc-MIBI what doesn't happen in the Q-MI what explains the no-existence of SSD in the behavior of both RT in this type of MI, but we don't give relevance to this discovery to have differences very small stockings with regard to the range in that these parameters moved, we also consider caution it should be had with this "bigger capacity" of the TL201 to determine viable myocardium because Thimothy F. et al (to the 6 weeks post-MI when it is supposed that recovered the stunned myocardium) found better correlation of the ejection fraction of the LV with the IFA the 99mTc-MIBI that with that of the TL201 (1) that which presupposes that the TL201 with reinyección undervalues the IFA with regard to the 99mTc-MIBI (this without study of viability).
We consider that our work has limitations like it is the fact that its reported by other authors that the SPECT overestimates the IFA (2) but it was not our objective to determine the absolute percent of this, but characterizing the behavior of both RT in front of the MI in general and its types, also in such a case the error margin will be the same one for the two RT, we consider insufficient the patients sample with studies carried out with both RT in which we confirm the results of the comparison of both RT (and we exhort the colleagues to carry out this study type but with big samples).
We conclude that both RT has a similar behavior in infarcted patients (whenever equivalent protocols are used) since they have the same aptitude to determine the IFA and IRA and both RT they maintain a similar behavior in front of each type of MI, therefore we recommend the use of the two RT indistinctly in infarcted patients independently type of MI of the although it is preferable the use of the 99mTc-MIBI in the obese and women to exist smaller attenuation probability.
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