Functional assessment of ALCAPA syndrome by dobutamine stress thallium-201 SPECT and echocardiography.

Exercise 201TI SPECT has been used as a useful method for the assessment of patients with anomalous left coronary artery communicating to the pulmonary artery (ALCAPA syndrome). In this study, we described an adult patient with this anomaly who was evaluated by dobutamine stress testing in conjunction with simultaneous 201Tl SPECT and echocardiography before and after surgery. A large perfusion defect in the anterior wall, septum and apex was detected on the preoperative stress scan with partial reversibility on reinjection scan. Worsening of wall motion abnormalities in the septum and anterior wall was detected by stress echocardiography. In the studies performed 3 mo and 1 yr after reimplantation of the left coronary artery in the aorta, a smaller fixed perfusion defect in the anterior wall and apex was detected without reversibility. No stress-induced wall motion abnormalities were detected. Despite the improvement of perfusion, there was no improvement of regional or global left ventricular function at rest. We report that both dobutamine 201Tl SPECT and echocardiography were useful for the detection of reversible ischemia and for the assessment of the surgical outcome of an adult patient with ALCAPA syndrome.

Evaluation by quantitative 99m-technetium MIBI SPECT and echocardiography of myocardial perfusion and wall motion abnormalities in patients with dobutamine-induced ST-segment elevation.

ST-segment elevation during exercise testing has been attributed to myocardial ischemia and wall motion abnormalities (WMA). However, the functional significance of ST-segment elevation during dobutamine stress testing (DST) has not been evaluated in patients referred for diagnostic evaluation of myocardial ischemia. DST (up to 40 micrograms/kg/min) with simultaneous echocardiography and technetium-99m sestamibi single-photon emission computed tomography (SPECT) was performed in 229 consecutive patients with suspected myocardial ischemia who were unable to perform an adequate exercise test; 127 (55%) had a previous acute myocardial infarction (AMI). ST elevation was defined as > or = 1 mm new or additional J point elevations with a horizontal or upsloping ST segment lasting 80 ms. Reversible perfusion defects on SPECT and new or worsening WMA during stress on echocardiography were considered diagnostic of ischemia. ST elevation occurred in 40 patients (17%) during the test; 34 of them (85%) had previous AMI. All patients with ST-segment elevation had abnormal scintigrams (fixed or reversible defects, or both) and abnormal wall motion (fixed or transient defect, or both) at peak stress. In patients who had ST elevation and no previous AMI (n = 6), ischemia was detected in all by echocardiography and in 5 (83%) by SPECT. In patients with previous AMI, the prevalence of ischemia was not different with or without ST elevation (53% vs 43% by echocardiography and 53% vs 48% by SPECT, respectively). Baseline regional wall motion score in the infarct zone was higher in patients with ST elevation.(ABSTRACT TRUNCATED AT 250 WORDS)

Potential and limitations of Tc-99m sestamibi scintigraphy for the diagnosis of myocardial viability.

Sestamibi is a Tc labeled radiotracer particularly suitable for myocardial perfusion studies, providing similar information as thallium scintigraphy for the diagnosis of coronary artery disease. In comparison with thallium, sestamibi has the advantage of improved imaging properties due to its higher gamma emission. This is particularly relevant when SPECT imaging is considered. The myocardial uptake of sestamibi is partially passively, related to the myocardial flow, and is also related to the metabolic cellular activity, as it is proportional to the electrochemical gradient generated at cell membrane level. While the role for sestamibi in diagnosing coronary artery disease is well accepted, it is still controversial for the assessment of myocardial viability. Clinical studies reported by others and results from our own institution will be described both in the setting of a recent myocardial infarction (myocardial stunning) and of longstanding left ventricular dysfunction (hibernating myocardium). The results concordantly suggest that sestamibi underestimates myocardial viability, compared to the accepted standards of thallium (rest-redistribution or stress-reinjection protocols), 18-F FDG PET and also in the prediction of left ventricular functional recovery after revascularisation. However, the data available at present are very limited, particularly after revascularisation. Furthermore, according to new promising results, the role of sestamibi in the setting of myocardial viability has potential for improvement, if the injection at rest will be performed during nitrates. It is also foreseen that the combined use of sestamibi perfusion/wall motion scan (first pass and/or gated perfusion studies) and the development of new softwares for attenuation correction might improve the results in the setting of myocardial viability.