Myocardial imaging with technetium-99m CPI: initial experience in the human.

The hexakis(isonitrile)technetium(I) analog [99mTc]carbomethoxyisopropyl isonitrile (CPI) has high myocardial uptake and rapid lung and liver clearance in most animal species. To evaluate [99mTc]CPI as a myocardial imaging agent in the human, we evaluated this tracer in three normals and in six patients with coronary artery disease (CAD). In normals, [99mTc]CPI cleared quickly from the lungs and accumulated in the liver and heart. The liver activity peaked at 10-15 min and cleared through the hepatobiliary system. Planar images were of excellent technical quality with high myocardial to background ratios as early as 10 min after injection. Myocardial activity fell gradually to 76.1 +/- 2.9 (s.d.)% of initial activity by 60 min after injection. In six patients with CAD, myocardial defects were present on planar images up to 2 hr after exercise and injection. In one out of six patients, the defect was not seen 3 hr after injection. In five of the six patients, normal perfusion patterns were observed 1 hr after reinjection of CPI at rest (4 hr after the initial injection). In one patient who developed spontaneous angina prior to reinjection, the perfusion defects persisted. The repeat study 3 days later with injection of [99mTc]CPI at rest was normal. Technetium-99m CPI appears to have excellent physical and biologic properties for use in association with myocardial imaging with exercise.

Usefulness of radionuclide ventriculography in assessment of coronary artery spasm.

Provocative tests that permit detection of coronary artery spasm are widely used in patients with ischemic syndromes. To assess the usefulness of radionuclide ventriculography combined with provocative tests for diagnosis of coronary spasm, the left ventricular (LV) response to exercise, hyperventilation and a cold pressor test was determined in 3 groups. Group I included 10 normal subjects; group II, 49 patients with typical effort angina and fixed obstructive coronary artery disease at catheterization; and group III, 19 patients suspected of having vasospastic angina based on clinical and electrocardiographic findings, each of whom had normal coronary angiographic findings. In group I, LV ejection fraction (EF) increased during hyperventilation and exercise testing in 9 of 10 subjects (90%) and failed to decrease 5% in 9 of 10 subjects (90%) during cold testing. In contrast, while 18 of 49 patients (37%) of group II showed LV dysfunction with cold testing and 8% with hyperventilation, all showed abnormal LV function during exercise. Finally, in group III, LVEF increased during exercise, mimicking the response in normal group, while dysfunction was present in 14 of 19 (74%) during hyperventilation and in 17 of 19 (89%) during cold testing. When results of hyperventilation and cold testing were combined, abnormal responses were present in all patients. Thus, radionuclide ventriculography, when performed in association with 3 forms of stress--exercise, hyperventilation and cold testing--allows accurate identification of patients likely to have coronary spasm.

Simultaneous measurement of ventricular function and myocardial perfusion using the technetium-99m isonitriles.

To assess both ventricular function and myocardial perfusion, five normal volunteers, 19 patients with coronary artery disease, and two patients with cardiomyopathy and normal coronary arteries were injected with 20 mCi of Tc-99m isonitrile (either methoxyisobutyl isonitrile or carbomethoxyisopropyl isonitrile) at peak bicycle exercise and again at rest. A standard Tl-201 stress test was performed in all patients at the same level of exercise within one month of the isonitrile study. In all normal subjects, myocardial perfusion was normal at stress levels and the left ventricular ejection fraction increased 5% or more with exercise. In the 19 patients with coronary artery disease, the ejection fraction response to exercise was abnormal in 14 patients. Perfusion images with the Tc-99m isonitriles correlated well with Tl-201 images during exercise and at rest, with 89% concordance in areas of ischemia or infarction and 93% in normal segments. A simultaneous study of myocardial perfusion and ventricular function can be performed using a single Tc-99m labeled myocardial agent. Tc-99m isonitriles, particularly Tc-99m MIBI, result in sufficiently high photon flux that ventricular performance can be studied at peak exercise and again during rest using the first pass method.

Myocardial perfusion imaging with a new radiotracer, technetium-99m-hexamibi (methoxy isobutyl isonitrile): comparison with thallium-201 imaging.

Technetium-99m-hexamibi (methoxy isobutyl isonitrile) is a Tc-99m-hexakis analog that can be used as a myocardial perfusion imaging agent. This is a report of an initial study that was performed in four institutions to assess the feasibility of Tc-99m-hexamibi myocardial imaging for the detection of coronary artery disease in patients undergoing treadmill stress test. Thirty-three patients referred for evaluation of chest pain had two exercise stress tests, one with Tl-201 and at least 24 hours after, and a second one with Tc-99m-hexamibi. Myocardial planar imaging started 60 minutes after injection at stress of 10-20 mCi of Tc-99m-hexamibi. Because this agent does not redistribute in myocardium after a stress injection, a second injection of 10-20 mCi of Tc-99m-hexamibi was performed with the patient at rest a few days later. Qualitative assessment of both Tl-201 and Tc-99m-hexamibi myocardial distribution was performed in 297 left ventricle segments (three segments of each of three views). There was a good correlation for the presence of normality, scar, or ischemia with the two radiopharmaceuticals, both on a segment by segment (259/297, or 87.2%) and patient-by-patient basis (29/33, or 87.9%). The number of segments found ischemic with Tl-201 and with Tc-99m-hexamibi were nearly equal, as were the number that were normal with one radiopharmaceutical and ischemic by the other. This initial study demonstrates that it is possible to detect stress-induced abnormalities of myocardial perfusion with Tc-99m-hexamibi similar to Tl-201 imaging.

[Simultaneous test of ventricular function and myocardial perfusion, during exercise, using a new agent labeled with Tc99m]. / Test simultáneo de función ventricular y perfusión miocárdica, durante el ejercicio, mediante un nuevo agente marcado con Tc99m.

One a tribute of a Tc 99m labeled myocardial agent is the possibility to measure both ventricular function and myocardial perfusion with a single injection. To assess this, normal volunteers, 14 patients with coronary artery disease (CAD) and two suffering from cardiomyopathy with normal coronaries, were injected with 8-10 mci carbomethoxy-isopropyl-isonitrile or 20 mci Rp-30 Tc 99m at peak semi-recumbent bicycle exercise and again at rest. Thirty msec per frame first pass data, and 5 min static anterior, 40(0-) and 70(0-) left anterior oblique images were obtained. Standard Thallium 201 stress test were also done, within one month, and were at the same level of exercise. The left ventricular ejection fraction (EF) increased with exercise (69%-76%) in normal patients. All studies showed normal myocardial perfusion on exercise. In CAD patients the EF increased in some patients who had ischemia. Perfusion images with Tc 99m during exercise and at rest had an identical correlation with Thallium 201. The results support the concept of dual ventricular function and perfusion studies using a single Tc 99m labelled myocardial agent, and suggest that this could become the standard radionuclide stress tests in the future.

The utilization of Tc-99m-TBI as a myocardial perfusion agent in exercise studies: comparison with Tl-201 thallous chloride and examination of its biodistribution in humans.

Twenty-four patients were studied with both 201Tl-thallous chloride and 99mTc-TBI scintigraphy following exercise. Comparison of the two agents in detecting segmental myocardial ischemia and scar was made in 18 patients with evidence of coronary artery disease on 201Tl-thallous chloride scintigraphy. Agreement between the two studies was observed in 77% (125 of 162) of left ventricular segments, suggesting that 99mTc-TBI can be used as a myocardial perfusion agent. Limitations were related to early high background activity from lungs and liver. The high lung activity and early myocardial redistribution within the 1st hour contributed to the failure of 99mTc-TBI to detect 16 segmental defects seen in the immediate post-exercise thallous chloride scan. Persistently high liver activity additionally affected accurate interpretation in the left ventricular segments close to the diaphragm. Improvement in the accuracy of 99mTc-TBI stress studies might be achieved with tomographic imaging to reduce the problem of background activity or by the development of 99mTc-labeled isonitrile analogues with rapid lung and liver clearance.

Test simultaneo de function ventricular y perfusion miocardica durante el ejercicio mediante un nuevo agente marcado con Tc99m / Simultaneous test of ventricular function and myocardial perfusion during exercise with a anew agent labelled with Tc99m

Utilizar un radiocompuesto con Tc99m para estudiar la perfusión miocárdica, permite determinar la función ventricular en la misma inyección, mediante la técnica de primer pasaje. Fueron estudiados 4 voluntarios normales, 14 pacientes con angina de esfuerzo y 2 portadores de miocardiopatía con coronarias normales. Todos fueron inyectados con 8-10mci de Tc99 carbometoxi-isopropil isonitrilo (CPI-Tc99m), o con 20mci de Tc99m-Nen-30, en el pico del ejercicio ergométrico y luego en reposo. Fue registrado el primer pasage del bolo radioactivo en imágenes de 30ms/frame. Se adquirieron luego a los 60 min las imágenes de perfusión correspondientes al esfuerzo, en las proyecriones anterior, OAI 45- y OAI 70-. Todos los pacietnes tenían realizado un estudio de perfusión de ejercicio con Talio 201 con similares niveles de esfuerzo. la fracción de eyección (FE) de ejercicio incrementó 69-76% en los normales; la perfusión miocárdica (PM) fue normal en todos ellos. En losportadores de miocardiopatía con coronarias normales, se observó disminución de la FE y la perfusión miocárdica con CPI-Tc99m. En los pacientes isquémicos la perfusión fue anormal en los 14 pacientes y la correlación con el Talio 201 fue excelente. Durante el ejercicio la FE incrementó en 4/14, disminuyó en 6/14 y permaneció sin cambios en 4/14. Estos resultados sugieren la posibilidad de utilizar el test simultáneo de perfusión y función ventricular con un solo ejercicio y radiocompuesto. La información de estos dos estudios mejoraría considerablemente la eficiencia del método, el cual podría convertirse en el test-radioisotópico estándar en el futuro