RAPID COMMUNICATION 

Annals of Nuclear Medicine Vol. 7 No. 3, 187-192, 1993 

Differentiation of transiently ischemic from infarcted nryocardium by Thallium-201 exercises scintigram after active ergometer rehabilitation 

Tomoyuki YAMBE, Shin-ichi NITTA, Motonao TANAKA, Tai-ichiroh MEGURO,* Yoshifumi SAIJOH,* Shigeru NAGANUMA,* Shin-ichi KOBAYASHI,* Norio ENDoH,** Yoshio TERASAWA,** Yoshiaki KATAmRA,*** Taroh SoNOBE,*** Keiko NrrTA,*** Hisanao TAKEDA,**** Kazuhiko TAKAHASrn,***** Yoshihisa SmMANUKI,***** and Hisao ITOH***** 

Department of Medical Engineering and Cardiology, Research Institute for Chest Diseases and Cancer, Tohoku University, *Department of Cardiology, Sendai Kousei Hospital, **Department of Cardiology, Sendai Shakaihoken Hospita/, ***Department of Cardiology, Tohoku Kousei-nenkin Hospital, ****Department of Cardiology, Miyagi Prefectural Semine Hospital, *****Department of Radiology, Tohoku University School of Medicine 

It has been frequently reported that while myocardial viability is neglected in conventional methods of diagnosis such as left ventriculography, ECG, and exercise thallium-201 myo-cardial scintigraphy (Ex-T1), revascularization often results in improving left ventricular wall motility. In the present study, the authors contrived a method to accurately evaluate the viability ot the myocardium by means of exercise rehabilitation, and tested the method in clinical cases. Among patients with myocardial infarction, we selected a patient with negative viability in the diseased area as determined by chronic ECG, Ieft ventriculography (LVG), coronary angiography and Ex-Tl. This patient went through two weeks of active exercise rehabilitation gauged with an ergometer, and was then re-examined by Ex-Tl. After the evaluation, revascularization was performed for the patient who demonstrated viability of the infarcted myocardium in EX-TI after rehabilitation, and significant improve-ment in contractility was shown in the chronic LVG. These findings indicate that our method of detecting potential viability of the infarcted myocardium is of clinical significance. 

Key words : Exercise Revascu-larization, 
SPECT Tl-201 myocardial scintigraphy, Viability, Rehabilitation,

INTRODUCTION 

In differentiating infarcted myocardium in the chronic stage from ischemic myocardium in patients with myocardial infarction, exercise Tl-201 myo-cardial scintigraphy (EX-Tl) is frequently used and its usefulness has been widely accepted.1,2 Nonethe-less, it has frequently been reported that while myocardial viability is neglected in Ex-Tl, reascular-ization by percutaneous transluminal coronary angioplasty (PTCA), or coronary artery bypass grafting (CABG) restores the contractility of the myocardium.3 In this regard, various procedures such as a delayed scan have been developed in an attempt to measure the viability of the myocardium more accurately.5 
The present study was designed to develop a method to clearly diagnose the presence of ischemic myocardium while noting viable myocardium within the infarcted region, as it has not been possible to confirm this by conventional procedures. There are reports showing that exercise rehabilitation has the effect of developing collateral coronary circulation for the ischemic myocardium. On the other hand, many reports show that exercise rehabilitation would not help in developing collateral circulation for the infarcted myocardium.5,6 Thus, if exercise rehabili-tation accelerates the development of collateral circulation for the ischemic myocardium, Iocated in the peripheral area of the infarcted region in patients with chronic myocardial infarction, it would become a useful procedure in diagnosing ischemic myo-cardium around the infarcted myocardium. 
A new way to cardium from the below. distinguish the ischemic infarcted myocardium is myo-shown 
First, patients with acute myocardial infarction (AMl) in the chronic stage, for whom the conven-tional methods failed to determine the viability of the myocardium, are selected. 
Second, these patients exercise rehabilitation on a specific period. 
are subjected to active a bicycle ergometer for 
Then, finally, the amount of viable myocardium in the infarcted myocardium is re-evaluated by Ex-T1. 
In this study, we discussed whether it is possible to accurately diagnose the presence of myocardial viability by this method, and compare the results with those obtained by conventional diagnostic procedures. 

SUBJECT AND METHOD 

1) Patient selection Of the patients admitted to our or affiliated hospitals for anterior AMI, those having fulfilled the follow-ing four conditions during the examination, were included in the present study over four weeks after the onset of the disease. (1) QS pattern in the anterior wall area isrecognized on the electrocadiogram (ECG). 
(2) Dyskinesis or akinesis in the anterior wall disclosed by left ventriculography (LVG) or ultrasonic cardiography (UCG). 
(3) Stenosis of 90% or more of the left anterior descending artery is shown in the coronary 
angiography (CAG). 
(4) Persistent defect disclosed by Ex-Tl. The first patient who met the above requirements had stable hemodynamic parameters. Treatment with a calcium antagonist and a nitrite agent resulted in good clinical development, and he completed the routine program for rehabilitation following myo-cardial infarction. 
2) Viability identification protocol The protocol of the present study is shown in Fig. l. For exercise scintigraphy, a bicycle ergometer was used. It followed a multi-stage incremental method, starting at 25W and increasing by 25W every three minutes. The exercise was ended following the appearance of chest pains or fatigue in the lower extremities, attaining the target heart rate, the appearance of remarkable ST-T changes on the ECG, or the onset of arrhythmia. 
Immediately after the exercise was stopped, 2 or 3 mCi of Tl-201 was injected intravenously, then the exercise was restarted and continued for about a minute. Pictures were taken, 4-5 min and 4 hr after intravenous injection with a Gamma Camera (ZLC-3700. Siemens) fitted with a singlehead high-resolution collimator. A Shimadzu Scintipac 2400 was used (ZLC-3700. Siemens) in processing nuclear medicine data. 
For the patients selected, an active exercise reha-bilitation program with the bicycle ergometer was ^followed for two additional weeks. The exercise program provided for the patients to operate the ergometer twice daily (morning and evening) with the load near their capacity (50 to 75W for 5 to lO min). HR was maintained within 50-150 beats/ min. After two weeks of exercise rehabilitation, Ex-TI was performed and scintigram results were analyzed . 
If any improvement is recognized on the scinti-grams after two weeks of rehabilitation, myocardial viability should be determined at this point. 
RESULTS 
In the first patient selected for this study, there was significant improvement in the Ex-TI after active rehabilitation with the bicycle ergometer compared with EX-TI before active rehabilitation. This sug-gested that there are clinical cases, whose viable myo-cardium within the infarcted area cannot be detected by conventional clinical examination, but can be detected by our newly developed method. The first case subjected to this study is described below. CASE REPORT

The patient is a 58-year-old man with acute myo-cardial infarction seen at our hospital four days after the onset of the disease. The left ventricular and coronary angiograms taken during the chronic phase showed akinesis in the anterior wall as shown in Fig. 2, and there was 99 ~ stenosis of the coronary artery with a remarkable contrasting delay in the #7 left anterior descending artery as shown in Fig. 3. Ex-TI disclosed a persistent defect in the anterior wall as shown in Fig. 4, and together with the ECG findings evident in Fig. 5 and the left ventricular image in Fig. 2, viability of the anterior wall was virtually ruled out. 
Bicycle ergometer rehabilitation was instituted for this patient, resulting in a fill-in in the anterior wall as shown by Ex-Tl, demonstrating possible viability in the anterior wall. And collateral circu-lation to the left anterior descending artery tended to increase in the coronary angiography (Fig. 5). Thus, PTCA was performed as shown in Fig. 3 to obtain satisfactory dilatation of the left anterior descending artery from 99 ~ to 25 ~ stenosis. The left ventricular image taken three months later disclosed a marked 
improvement in the motility of the anterior wall. 

DISCUSSION 

Ex-TI is frequently used for the evaluation of viable myocardium in patients with old myocardial infarc-tion to determine the indications for revascular-ization such as PTCA or CABG.3 A persistent defect in the Ex-TI is diagnosed as the infarcted zone and is not taken as an indication for the revascularization.4 However, several investigators reported that while myocardial viability is ruled out by Ex-Tl, revascu-larization restores the contractility of the myo-cardium.4,6 Since Braunwald et al. reported the concepts of stunned myocardium and hibernating myocardium, the existence of this phenomena sug-gested to us that movement of the left ventricular wall shown in the LVG and UCG is not useful in the evaluation of myocardial viability.7 It is therefore very important to develop a method to diagnose clearly the presence of ischemic but noting viable myocardium within the infarcted region, as it has not been possible to confirm this by conventional procedures. 
One of the major findings in this study is the existence of a clinical case whose viable myocarium within the infarcted area could not be detected by the conventional clinical examination, but could be detected by our newly developed method, suggesting the clinical efficiency of our procedure. This phe-nomenon is probably due to the development of the collateral circulation to the ischemic, but viable, myocardium within the infarcted myocardium. Many reports show that exercise rehabilitation does not help in developing the collateral circulation for the infarcted myocardium, but has the the effect of developing collateral coronary circulation for the ischemic myocardium.4,8. Therefore, acceleration of the development of collateral circulation for the ischemic myocardium located in the peripheral area of the infarcted region in patients with chronic myocardial infarction by means of active reha-bilitation with a bicycle ergometer, becomes a useful procedure in diagnosing ischemic myocardium around the infarcted myocardium. 
Another procedure for the evaluation of the ischemic myocardium within the infarcted myo-cardium has been developed by various investigators using positrontomography.5 However, it is evident that it is not useful for a small hospital like ours because positrontomography is too expensive. 
It is very important for us to develop a simple and economical procedure to determine the indi-cations for the revascularization. Our newly developd procedure shown here is a very simple and eco-nomical method for the small hospital and useful in accurately diagnosing the presence of myocardial viability . 
To sum up, the authors contrived a method to accurately evaluate the viability of the myocardium by means of exercise rehabilitation, and tested the method in a clinical case. From among the patients with myocardial infarction, we selected a patient with negative viability in the diseased area as deter-mined by chronic ECG, LVG. CAG, and Ex-Tl. This patient went through two weeks of active exercise rehabilitation gauged with an ergometer, and was then re-examined by scintigraphy. After the evaluation, revascularization was performed on the patient who demonstrated viability of the infarcted myocardium in EX-TI after rehabilitation, and showed improvement in contractility, according to the chronic LVG. These findings indicate that our method of detecting potential viability of the in-farcted myocardium is of clinical significance. 

ACKNOWLEDGMENT 

The authors thank Mrs. Hisako lijima, and Miss Taeko Ishiyama for their technical assistance. 

REFERENCES 

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