Specific perfusion pattern in stress 201Tl myocardial scintigraphy of left main coronary artery disease

The usefulness of stress ²⁰¹Tl myocardial scintigraphy for identifying left main coronary artery disease was evaluated with data from 23 patients with 50% or more narrowing of the left main coronary artery and 56 patients with 75% or more narrowing of the major coronary arteries but without left main coronary artery involvement (no left main coronary artery disease). Quantitiative evaluation of stress perfusion scintigrams in all five patients with narrowing of the left main coronary artery of 99% or more showed a characteristic perfusion pattern (left main pattern) of extensive homogeneous defect over the whole anterolateral segment and simultaneous defects in all radii of the high anteroseptal and high posterolateral segments. On the other hand, such a perfusion pattern was noted in only 1 of 18 patients with less than 90% stenosis of the left main coronary artery and in only 1 of 56 patients with no left main coronary artery disease     

Specific perfusion pattern in stress 201Tl myocardial scintigraphy of left main coronary artery disease

The usefulness of stress 201Tl myocardial scintigraphy for identifying left main coronary artery disease was evaluated with data from 23 patients with 50% or more narrowing of the left main coronary artery and 56 patients with 75% or more narrowing of the major coronary arteries but without left main coronary artery involvement (no left main coronary artery disease). Quantitative evaluation of stress perfusion scintigrams in all five patients with narrowing of the left main coronary artery of 90% or more showed a characteristic perfusion pattern (left main pattern) of extensive homogeneous defect over the whole anterolateral segment and simultaneous defects in all radii of the high anteroseptal and high posterolateral segments. On the other hand, such a perfusion pattern was noted in only 1 of 18 patients with less than 90% stenosis of the left main coronary artery and in only 1 of 56 patients with no left main coronary artery disease.     

冠状动脉痉挛致心肌血流灌注降低：反向再分布的机制研究

目的 探讨冠状动脉痉挛患者核素心肌灌注显像反向再分布（RR）的机制.方法 选择双嘧达莫负荷201TI心肌灌注显像表现为RR且诊断为冠状动脉痉挛的患者26例（RR组）、无冠状动脉狭窄及RR者16例（对照组）,在冠状动脉造影术中重复双嘧达莫试验,测量并比较注射双嘧达莫前后RR相关、非RR相关血管和对照组相应血管的校正心肌梗死溶栓疗法（TIMI）血流帧计数（CTFC）和心肌血流灌注积分（TMPG）.统计学处理采用t检验、χ2检验及相关分析.结果 冠状动脉造影见RR相关血管僵硬,血流速度和心肌灌注明显低于非RR相关血管,且RR区域静态心肌灌注缺损与冠状动脉造影血流速度缓慢高度相关（r=0.79,t=10.18,P＜0.001） 而对照组的各支冠状动脉血流速度和心肌灌注无明显差异.RR相关血管注射双嘧达莫前后CTFC分别为（36±6）帧及（26±7）帧（t=4.15,P＜0.01） TMPG分别为（2.02±0.39）级和（2.92±0.12）级（t=2.25,P＜0.05） 非RR相关血管注射前后CTFC分别为（29±7）帧及（25±5）帧（t=2.31,P＜0.05） TMPG分别为（2.56±0.31）级和（2.96±0.06）级（t=2.17,P＜0.05） 而对照组注射双嘧达莫前后TCFC及TMPG均无明显变化（t=0.932及0.867,P均＞0.05）.结论 冠状动脉痉挛患者静息状态下RR相关血管及微血管处于轻度痉挛状态,导致血流速度及心肌灌注缓慢 而负荷状态下血管扩张,使血流速度和心肌灌注加快,因而呈现RR.     

冠状动脉痉挛致心肌血流灌注降低:反向再分布的机制研究

Objective To investigate the mechanism of reverse redistribution (RR) on dipyridamole 201Tl myocardial perfusion studies in the patients with coronary artery spasm. Methods Twenty-six patients with coronary artery spasm and presented as RR on dipyridamole 201Tl myocardial perfusion studies were enlisted as RR group, while other 16 patients with no coronary artery stenosis nor RR were enlisted as control group. Dipyridamole test was repeated during coronary angiography. Corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC) and TIMI myocardial perfusion grade (TMPG) were measured at RR related and non-RR related coronary arteries before and after dipyridamole infusion respectively.All of the data were analyzed by Student's t-test orχ2-test and correlation analysis. Results Coronary artery angiography showed slower blood flow and lower myocardial perfusion in RR related vessels when compared with non-RR related vessels in RR group, but there was no significant difference among the main coronary arteries in control group. The perfusion defects of RR area at rest were positively related to slowerblood velocity at corresponding coronary arteries ( r = 0.79, t = 10.18, P ＜ 0.001 ). In RR related vessels,CTFC were (36 ±6) frames and (26 ±7) frames (t =4.15, P ＜0.01 ), while TMPG were (2.02 ±0.39)grades and (2.92 ± 0.12) grades ( t = 2.25, P ＜ 0.05 ) before and after dipyridamole infusion, respectively.In non-RR related vessels, CTFC were (29 ±7) frames and (25 ±5) frames (t =2.31, P ＜0.05), while TMPG were (2.56 ± 0.31 ) grades and (2.96 ± 0.06) grades ( t = 2.17, P ＜ 0.05 ) before and after dipyridamole infusion, respectively. However, there were no significant changes of CTFC and TMPG before and after dipyridamole infusion in control group ( t = 0.932, 0.867, respectively, both P ＞ 0.05 ). Conclusion RR is related to the decreased blood flow and myocardial perfusion induced by coronary artery spasm at rest,which may be improved by stress test such as intravenous dipyridamole infusion.     

Assessment of left ventricular function by 201Tl ECG-gated myocardial SPECT]

We applied the QGS program for LV function analysis (described by Germano, 1995) to a 201Tl SPECT study at rest, and estimated its accuracy. We performed 201Tl ECG-gated myocardial SPECT in 25 patients with ischemic heart disease under an acquisition time used in the routine 99mTc ECG-gated SPECT study. The quality of the gated images was visually assessed with a 4-point grading system. LVEDV, LVESV, LVEF determined by the QGS program were compared with those by Simpson's method on biplane LVG in 25 patients. Regional wall motion scores in 7 myocardial segments were assessed on the three-dimensional display created by the QGS program and the cine display of biplane LVG with a 5-point grading system. Wall motion scores obtained by the QGS program were compared with those by LVG. Although 72.0% of 201Tl ECG-gated SPECT images were fair or poor in image quality, there were good correlations between the values obtained by the QGS program and LVG (LVEDV: r = 0.82, LVESV: r = 0.88, LVEF: r = 0.89). In addition, wall motion scores by the QGS program were correspondent to those by LVG in 77.1% of all 175 myocardial segments. We conclude that the QGS program provides high accuracy in evaluating left ventricular function even from 201Tl ECG-gated myocardial SPECT data.     

Regional rates of myocardial fatty acid metabolism: comparison with coronary angiography and ventriculography

In 50 patients, 1 mCi¹²³I phenylpentadecanoic acid (IPPA) was injected at peak ergometric stress and 1500 frames were acquired (1 frame/s) with a high count rate gamma camera. Parametric images of rates of decrease and increase for different time intervals after stress were compared with coronary angiography and LV ventriculography, separately evaluating the 3 main coronary territories: 18/150 territories supplied by normal coronaries presented rather homogeneous regional clearing rates, whereas a gradual decrease in clearing rates towards the end of the territory (frequently with peripheral defects) was seen in all 87/150 territories with significant coronary narrowing. In local correspondence to clearing defects, initial IPPA accumulations could be observed with later onset of clearing between 10 and 25 min. 44/150 territories presented abnormal clearing rates, mostly with a patchy pattern, with normal coronary anatomy, but all except one had LV dysfunction and a clinical diagnosis of Cadomyopathy, diabetes mellitus or hypertensive disease. Twenty four of the 41 patients with CAD had, in correspondence to a prior myocardial infarction, minimum or missing metabolic activity frequently in circumscribed zones, partly separated by bridges of still viable tissue with preserved but reduced clearing rates.     

Regional rates of myocardial fatty acid metabolism: comparison with coronary angiography and ventriculography

In 50 patients, 1 mCi 123I phenylpentadecanoic acid (IPPA) was injected at peak ergometric stress and 1500 frames were acquired (1 frame/s) with a high count rate gamma camera. Parametric images of rates of decrease and increase for different time intervals after stress were compared with coronary angiography and LV ventriculography, separately evaluating the 3 main coronary territories: 18/150 territories supplied by normal coronaries presented rather homogeneous regional clearing rates, whereas a gradual decrease in clearing rates towards the end of the territory (frequently with peripheral defects) was seen in all 87/150 territories with significant coronary narrowing. In local correspondence to clearing defects, initial IPPA accumulations could be observed with later onset of clearing between 10 and 25 min. 44/150 territories presented abnormal clearing rates, mostly with a patchy pattern, with normal coronary anatomy, but all except one had LV dysfunction and a clinical diagnosis of cardiomyopathy, diabetes mellitus or hypertensive disease. Twenty four of the 41 patients with CAD had, in correspondence to a prior myocardial infarction, minimum or missing metabolic activity frequently in circumscribed zones, partly separated by bridges of still viable tissue with preserved but reduced clearing rates.     

Prognostic value of 201Tl myocardial scintigraphy after coronary artery bypass grafting

BACKGROUND: 201Tl myocardial scintigraphy (201Tl SPECT) is of strong prognostic value in various populations with suspected or known coronary artery disease. However, its value in patients with coronary artery bypass grafting (CABG) is not fully assessed. METHODS: We examined 115 consecutive patients to determine the relation between clinical data/stress 201Tl SPECT performed 5+/-3 years after CABG, and subsequent cardiac events. RESULTS: Thirteen patients (11%) had stress-induced angina, 22 (19%) had electrical positivity, and 97 (84%) had abnormal scintigraphy, including 62 (54%) with reversible defects. During follow-up (35+/-22 months), there were nine cardiac deaths, seven myocardial infarctions, and 20 revascularization procedures. Multivariate Cox analysis identified the delay between CABG and scintigraphy (P<0.01, relative risk (RR) = 1.01), the extent of stress 201Tl defects (P = 0.04, RR = 1.18), and increased stress 201Tl lung uptake (P = 0.03, RR = 3.56) as significant predictors of cardiac deaths/infarctions. Delay between CABG and scintigraphy (P < 0.001, RR = 1.01), the extent of stress 201Tl defects (P = 0.03, RR = 1.15), and that of reversible defects (P = 0.05, RR = 1.13) were the only significant predictors of total events. CONCLUSIONS: Besides the delay between CABG and scintigraphy, the scintigraphic parameters were the only significant and additive predictors of cardiac events in 115 patients with CABG.     

Evaluation of myocardial perfusion and left ventricular function by 201Tl scintigraphy after dipyridamole

²⁰¹Tl myocardial imaging was performed at rest and after dipyridamole (0.44 mg/kg) on 50 patients with known or suspected ischemic heart disease. The dipyridamole had no effect in 14 patients (group Dip. 0). In 17 patients (group Dip±) it significantly modified the contrast of the rest image (by increasing or decreasing a rest perfusion defect). In 19 patients (group Dip-Steal) the drug induced a paradoxical response interpreted as a coronary steal effect (an active region at rest becomes hypoactive after dipyridamole while an underperfused region at rest improves).All patients underwent coronary arteriography and left monoplane ventriculography; results were interpreted in relation to these angiographic data. The mean percentage of stenoses (per patient) was about the same in the three groups but it was found that, despite these stenoses, the patients of the group Dip —Steal had a good left ventricular function ( =0.62±0.12). On the other hand, the ejection fraction was very poor in the two other groups (0.50±0.17 and 0.48±0.17). Moreover it was found that: (1) the frequency of high grade or even complete obstruction was notably less in group Dip-Steal (P<0.05); (2) the frequency of angiographically visible collaterals was higher in group Dip-Steal (P<0.05); (3) the left anterior descending artery was less diseased than the right coronary artery in group Dip-Steal (P<0.05).These results have a real prognostic value for the assessment of the preserved cardiac performance in Dip-Steal patients despite severe stenoses, and are discussed in terms of compensatory collateral circulation and preservation of the coronary-flow reserve in the myocardium distal to a critical stenosis.     

Prognostic investigations after myocardial infarction: A comparison of radionuclide angiography and 201Tl scintigraphy

The ability of pre-discharge thallium Tl201 scintigraphy and radionuclide angiography (RNA) to predict subseqeunt cardiac events was investigated in 46 apparently low-risk survivors of a first acute myocardial infarction. All patients underwent selective coronary arteriography at 3 months post-discharge. At the time of the initial investigation, half were beta-blocked, and thereafter, all patients were given prophylactic beta-blockade. During a mean follow-up period of 12±4 months, 14 patients (30%) experienced cardiac events, i.e. recurrent myocardial infarction (3 patients), angina pectoris (13 patients) and coronary surgery (8 patients). No patient died during the follow-up period. Of the 14 with subsequent cardiac events, 11 were identified by the presence of a reversible perfusion defect at ²⁰¹Tl scintigraphy, while 7 exhibited abnormal left ventricular exercise reserve on RNA. The predictive accuracy of ²⁰¹Tl (85%) for subsequent cardiac events exceeded that of RNA (56%; P<0.01) and of arteriographic multi-vessel disease (65%; P<0.05). The sensitivity of the non-invasive techniques was not influenced by beta-blockade at the time of investigation. Thus, ²⁰¹Tl scintigraphy appears to be the more accurate technique for the assessment of the prognosis of apparently low-risk patients following myocardial infarction. The accuracy of the technique was not reduced by beta-adrenergic blockade.     

Prognostic investigations after myocardial infarction: a comparison of radionuclide angiography and 201Tl scintigraphy

The ability of pre-discharge thallium Tl201 scintigraphy and radionuclide angiography (RNA) to predict subsequent cardiac events was investigated in 46 apparently low-risk survivors of a first acute myocardial infarction. All patients underwent selective coronary arteriography at 3 months post-discharge. At the time of the initial investigation, half were beta-blocked, and thereafter, all patients were given prophylactic beta-blockade. During a mean follow-up period of 12 +/- 4 months, 14 patients (30%) experienced cardiac events, i.e. recurrent myocardial infarction (3 patients), angina pectoris (13 patients) and coronary surgery (8 patients). No patient died during the follow-up period. Of the 14 with subsequent cardiac events, 11 were identified by the presence of a reversible perfusion defect at 201Tl scintigraphy, while 7 exhibited abnormal left ventricular exercise reserve on RNA. The predictive accuracy of 201Tl (85%) for subsequent cardiac events exceeded that of RNA (56%; P less than 0.01) and of arteriographic multi-vessel disease (65%; P less than 0.05). The sensitivity of the non-invasive techniques was not influenced by beta-blockade at the time of investigation. Thus, 201Tl scintigraphy appears to be the more accurate technique for the assessment of the prognosis of apparently low-risk patients following myocardial infarction. The accuracy of the technique was not reduced by beta-adrenergic blockade.     

Relationship between 201Tl uptake and oxidative metabolism in cultured myocardial cells

The uptake of thallium-201 (201Tl) by myocardial cells in cultures was assessed in the presence of 10(-3) M potassium cyanide (KCN), an inhibitor of mitochondrial respiration, and 10(-4) M dinitrophenol (DNP), an uncoupler of oxidative phosphorylation. The cultures were incubated with 14C-glucose or 14C-octanoate, allowing the measurement of the oxidative metabolism and beta-oxidation from the production of 14CO2. The results demonstrated a moderate decrease in the ratio between the intra/extracellular concentration of 201Tl (Tl i/e) in the presence of KCN (28.9 +/- 8.1 versus 35.6 +/- 9.7 in the controls, n.s.) and no change with DNP (37.6 +/- 9.7). Glycolysis and fatty acid oxidation were lowered with KCN (-28 +/- 15 and -45 +/- 22% respectively, p less than 0.05 in both cases) and were non significantly increased with DNP (+37 +/- 23 and +10 +/- 52% respectively). These results show that 201Tl intracellular uptake is not related directly, but is not totally independent of glycolysis and fatty acid oxidation.     

The unfolded map using 201Tl myocardial SPECT

The unfolded map is a new method to show the ²⁰¹Tl distribution of left ventricle using SPECT. In 52 cases these maps were obtained at the stress study and 4 h later. The maximal count profiles of the perimeters for each short axis image were unfolded and were arranged from the apex to base of the left ventricle into a two dimensional map. All patients had chest pain and were suspected of coronary artery disease. The unfolded map had significant correlations between coronary arteriogram and exercise ECG findings. In conclusion, this method reflects the ischemic area of left ventricular myocardium, closer to the real left ventricular myocardium than Bull's eye display and is useful in the diagnosis of coronary heart disease.