Zuo-Xiang He

Diagnosis of coronary artery disease by exercise thallium-201 tomography in patients with a right ventricular pacemaker

OBJECTIVES We sought to study the accuracy of exercise perfusion scintigraphy in patients with an implanted apical right ventricular pacemaker. BACKGROUND The specificity of exercise perfusion scintigraphy is decreased in patients with a left bundle branch block. Patients with a permanent ventricular pacemaker have a similar conduction abnormality that may also potentially result in similar false positive perfusion defects. METHODS One hundred five patients with a right ventricular pacemaker underwent exercise thallium-201 tomography and coronary angiography within 7 days of each other. Patients with a previous myocardial infarction were excluded. RESULTS Patients were classified into four groups according to the agreement or disagreement between the thallium tomographic and coronary angiographic results. Only 8% of patients with normal results by both techniques were continuously paced during exercise, compared with 78% of patients with normal angiographic results but abnormal scintigraphic results. The mean defect size was 12% in the latter group. Most of the false positive defects were localized to the inferoposterior (71%), apical (50%) and inferoseptal (28%) walls. CONCLUSIONS Patients who are paced in the right ventricular apex and who continue to be paced throughout exercise have a high incidence of false positive thallium-201 single-photon emission computed tomographic defects.

Deceleration Time in Ischemic Cardiomyopathy

Background—In patients with heart failure secondary to left ventricular (LV) systolic dysfunction, a short deceleration time (DT) successfully predicts clinical outcome. The impact of myocardial viability and revascularization on the mitral inflow velocities, however, is unknown. Methods and Results—Forty patients with ischemic cardiomyopathy underwent 201Tl scintigraphy (SPECT) and 2D, Doppler, and dobutamine echocardiography (DE, to 40 μg · kg−1 · min−1) 2 days before CABG. Echocardiography was repeated 3 months after revascularization to determine recovery of function. Significant correlations were present between DT and LV contractile reserve by DE (r=0.72), scar perfusion defect by SPECT (r=−0.69), and the change in ejection fraction (ΔEF) after surgery (r=0.77) (all P 150 ms effectively identified (sensitivity 79%, specificity 81%) patients with ΔEF ≥5%. The population was divided into 2 groups according to DT: group 1 (DT >150 ms, n=21) and group 2 (DT ≤150 ms, n=19). At baseline, NYHA c...

Myocardial Blood Flow and Myocardial Uptake of 201Tl and 99mTc-Sestamibi During Coronary Vasodilation Induced by CGS-21680, a Selective Adenosine A2A Receptor Agonist

Background —We investigated the hemodynamic and coronary vasodilatory effects of CGS-21680, a potent selective adenosine A 2A agonist, as well as its potential use as a new stress modality in combination with perfusion scintigraphy. Methods and Results —A stenosis of the left anterior descending coronary artery (LAD) was produced in dogs to reduce the reactive hyperemic response to 201 Tl (0.5 mCi) and 99m Tc-sestamibi (5 mCi) were injected at the maximal dose of CGS-21680. Heart rate decreased with adenosine but increased during CGS-21680 infusion ( P P P P P =NS), and transmural 201 Tl and 99m Tc-sestamibi count-activity ratios (0.48±0.11 and 0.51±0.09, respectively) were also comparable ( P =NS). Myocardial scintigraphy uncovered perfusion defects in all dogs. Conclusions —CGS-21680 elicits coronary vasodilation comparable to that of adenosine and produces profound heterogeneity of MBF and of 201 Tl and 99m Tc-sestamibi myocardial uptake, rendering it a promising agent for pharmacological myocardial perfusion imaging.

Nitrate-augmented myocardial imaging for assessment of myocardial viability

Abstract201Tl myocardial perfusion imaging is presently done by several possible strategies. Stress/delayed redistribution, stress/redistribution/reinjection, and rest/redistribution imaging can be useful in the clinical assessment of myocardial viability. Unfortunately, the extent of myocardial viability may still be underestimated even by 201Tl reinjection imaging, compared with 18F-fluorodeoxyglucose positron emission tomography. 99mTc-labeled sestamibi imaging provides results similar to those of 201Tl imaging in the detection of coronary artery disease, but several previous studies suggest that stress/rest 99mTc-labeled sestamibi imaging significantly underestimates myocardial viability. Recently it has been reported that the administration of nitrates, before 201Tl reinjection, improves detection of defect reversibility. Several studies also suggested that administration of nitrates before the injection of 99mTc-labeled sestamibi significantly improved detection of reversibility with this agent, whereas additional studies showed further that this combination improves the predictive accuracy for recovery of left ventricular function and perfusion after coronary revascularization, compared with a standard rest 99mTc-labeled sestamibi study. Nitrate administration before the injection of 201Tl and 99mTc-labeled sestamibi may thus be a potentially attractive alternative for the evaluation of myocardial viability. Although the available results are encouraging, further studies are needed to evaluate the clinical value of 201Tl and 99mTc-labeled sestamibi imaging, in combination with nitrates, for predicting recovery of left ventricular dysfunction.

Evaluation of myocardial viability by myocardial perfusion imaging: should nitrates be used?

ConclusionECG GSPECT myocardial perfusion imaging is easily performed with most available imaging systems. It does not involve additional patient time and adds only minimal processing time for the technologist. GSPECT is the only study that allows simultaneous assessement of perfusion and function. This technique has demonstrated increases in test specificity and diagnostic accuracy and may eliminate the need for additional procedures.

Nitrate-augmented myocardial perfusion imaging for assessment of myocardial viability: recent advances.

Nitrate-augmented myocardial perfusion imaging has been demonstrated to improve the detection of myocardial viability and accurately predicts recovery of left ventricular (LV) function in patients with severe coronary artery disease and LV dysfunction. Recently, several studies showed the prognostic utility of nitrate imaging in evaluation of event-free survival in ischemic LV dysfunction. Furthermore, the diagnostic power of nitrate imaging compared with positron emission tomography or MRI, as well as the mechanism of nitrate-enhanced imaging, were also studied. We describe recent studies using nitrate-augmented myocardial perfusion imaging for the assessment of myocardial viability.