Angiographic and scintigraphic (perfusion and electrocardiogram-gated SPECT) correlates of clinical presentation in unstable angina

Influences of radionuclides on left ventricular phase analysis of gated myocardial perfusion single-photon emission computed tomography images in ischemic heart disease

OBJECTIVE

Phase analysis is expected to improve the accuracy of myocardial ischemia diagnosis in conjunction with myocardial perfusion and wall motion imaging and quantification. Although previous studies have reported perfusion image disagreements in relation to radionuclides, a few reports have examined the influences of radionuclides on phase analysis. We evaluated the influences of different radionuclides on stress-induced left ventricular mechanical dyssynchrony by phase analysis using electrocardiogram (ECG)-gated myocardial perfusion single photon emission computed tomography (SPECT) (MPS) imaging in patients with ischemic heart disease (IHD).

METHODS

A total of 202 patients with suspected or known IHD were investigated retrospectively. All the patients underwent coronary arteriography and were subsequently classified into the following groups: 43 patients without any coronary lesion (0VD), 71 patients with single-vessel disease (1VD), 59 patients with two-vessel disease (2VD), and 29 patients with three-vessel disease (3VD). Both stress and rest gated-MPS were performed using ^99mTc-methoxyisobutylisonitrile (MIBI)/tetrofosmin (TF) in 118 patients and with ²⁰¹TlCl in 84 patients. Phase analysis was performed to obtain the peak phase, phase standard deviation (SD), and bandwidth. Finally, we investigated potential differences between the phase analysis indices and the respective radionuclides used.

RESULTS

The peak phase did not exhibit any significant differences in the numbers of affected branches in either ^99mTc-MPS or ²⁰¹Tl-MPS during stress or rest MPS. Furthermore, both the phase SD and bandwidth demonstrated a tendency to increase in patients with increased numbers of affected branches. A significant difference was observed in the stress MPS when ^99mTc-MIBI/TF was used (p < 0.05), but no significant difference was observed in the stress MPS when ²⁰¹TlCl was used. Both the phase SD and bandwidth of all patients in ^99mTc-MPS during stress were significantly larger than those at rest (p < 0.05). Conversely, both the phase SD and bandwidth of all patients in ²⁰¹Tl-MPS at stress was significantly smaller than that at rest (p < 0.05).

CONCLUSION

Phase analysis using ^99mTc-MPS was considered to be useful for the detection of stress-induced left ventricular mechanical dyssynchrony, although it is necessary to be careful when using ²⁰¹Tl-MPS.

Development of a 2-Layer Double-Pump Dynamic Cardiac Phantom

The conventional dynamic cardiac phantom used in the field of nuclear medicine has a structure for which the size of the external side of the heart (the outer membrane substituting the myocardial layer) is fixed and only the inner side (the inner membrane substituting the ventricle part) moves anteroposteriorly. Therefore, its usefulness in technical evaluation is limited. Hence, we developed a new dynamic cardiac phantom in which the outer and inner membranes freely move.

METHODS

Using a SPECT/CT system, we performed validation by filling the myocardial layer of the dynamic cardiac phantom with solution and the ventricle part with contrast medium. We evaluated myocardial wall motions of 3 segments (basal, mid, and apical) by setting the stroke ratios at 20:20 and 10:10 (ventricle-to-myocardial layer ratio).

RESULTS

The myocardial wall motions (mean ± SD) at the stroke ratio of 20:20 were 7.50 ± 0.44, 11.15 ± 0.56, and 9.90 ± 0.24 mm in the basal, mid, and apical segments, respectively. The wall motions (mean ± SD) at the stroke ratio of 10:10 were 3.82 ± 0.43, 5.63 ± 0.39, and 4.53 ± 0.10 mm, respectively.

CONCLUSION

In our dynamic cardiac phantom, different movements could be induced in the myocardial wall by freely changing the stroke ratio. These results suggest that the use of this phantom can realize technical evaluation that presumes various clinical conditions.

Performance of rest myocardial perfusion imaging in the management of acute chest pain in the emergency room in developing nations (PREMIER trial)

BACKGROUND

Rest myocardial perfusion imaging (MPI) is effective in managing patients with acute chest pain in developed countries. We aimed to define the role and feasibility of rest MPI in low-to-middle income countries.

METHODS AND RESULTS

Low-to-intermediate risk patients (n = 356) presenting with chest pain to ten centers in eight developing countries were injected with a Tc-99m-based tracer, and standard imaging was performed. The primary outcome was a composite of death, non-fatal myocardial infarction (MI), recurrent angina, and coronary revascularization at 30 days. Sixty-nine patients had a positive MPI (19.4%), and 52 patients (14.6%) had a primary outcome event. An abnormal rest-MPI result was the only variable which independently predicted the primary outcome [adjusted odds ratio (OR) 8.19, 95% confidence interval 4.10-16.40, P = .0001]. The association of MPI result and the primary outcome was stronger (adjusted OR 17.35) when only the patients injected during pain were considered. Rest-MPI had a negative predictive value of 92.7% for the primary outcome, improving to 99.3% for the hard event composite of death or MI.

CONCLUSIONS

Our study demonstrates that rest-MPI is a reliable test for ruling out MI when applied to patients in developing countries.

Value of simultaneous functional assessment in association with acute rest perfusion imaging for predicting short- and long-term outcomes in emergency department patients with chest pain

BACKGROUND

Rest tomographic myocardial perfusion imaging (MPI) has significant utility for clinical decision making in emergency department chest pain patients. The role of functional data, commonly acquired with perfusion, has not been systematically evaluated.

METHODS AND RESULTS

Low- to moderate-risk patients undergoing rest MPI for risk stratification were included. The patients' MPI findings were classified as normal (normal perfusion or function), abnormal (perfusion defect with abnormal regional function), or discordant (perfusion defect with normal regional function). Ejection fraction was determined from the gated MPI studies. Events based on perfusion classifications and ejection fraction were evaluated. A total of 2,826 consecutive patients (abnormal MPI results in 40%, normal in 32%, and discordant in 27%) were studied. Outcomes were similar for those with normal MPI results versus those with discordant MPI results (myocardial infarction [MI] based on troponin I [TnI], 3.5% vs 4.0%; MI based on creatine kinase-MB, 1.5% vs 1.7%; revascularization, 5.2% vs 5.5%; and MI/revascularization based on TnI, 7.9% vs 8.1%) (P = not significant for all). Both groups had significantly fewer events (P < .001 for all) when compared with patients with abnormal MPI studies (MI based on TnI, 15%; MI based on creatine kinase-MB, 10%; revascularization, 17%; MI based on TnI or revascularization, 24%). The mortality rate was not different among the 3 groups. Multivariate analysis showed that mild/moderate and severe systolic dysfunction were independent predictors of 30-day and 1-year mortality rates (P = .001).

CONCLUSIONS

The concurrent evaluation of perfusion and function (regional and global) with MPI provides significant risk/outcome predictive power.

Imaging in the evaluation of the patient with suspected acute coronary syndrome

Over the last decade, major advances have been made in the treatment of acute coronary syndromes (ACSs). However, effective implementation of these treatments requires timely and accurate identification of the high-risk patient among all those presenting to the emergency department (ED) with symptoms suggestive of ACS. The opportunity for improving outcomes is time-dependent, so that early identification of the patient who has true ACS is essential. This necessity further increases the need for rapid triage tools, especially in the current setting of ED and hospital overcrowding that has become the norm in large urban centers.

Imaging in the evaluation of the patient with suspected acute coronary syndrome

Patients presenting to the emergency department with chest pain have a common problem. Definitive diagnosis at presentation is difficult due to limitations of the initial evaluation, and, thus, the majority of patients are admitted. Recognition of these limitations has driven the investigation of alternative evaluation techniques and protocols to attempt to improve diagnostic sensitivity without increasing overall costs. Acute myocardial perfusion imaging has been a highly valuable technique for risk stratification of intermediate to low-risk patients with chest pain. However, for a variety of reasons, it has not been widely embraced. In the past few years, alternative techniques have been investigated for use in the diagnosis of acute coronary syndromes in the acute setting. Coronary calcium scoring and cardiac magnetic resonance imaging show promise as new tools in the armamentarium for acute coronary syndromes. The challenge now lays in developing a strategy that uses these and future techniques most appropriately to support optimal medical decision making.

Validation of quantitative gated single photon emission computed tomography and an automated scoring system for the assessment of regional left ventricular systolic function

Despite its ability to quantify regional perfusion and function, there is no established method for quantification of regional perfusion and function by myocardial gated single photon emission computed tomography (SPECT). The aim of this study was to establish a quantitative index for regional perfusion and systolic function assessment using gated SPECT. Myocardial SPECT was performed at rest using (99m)Tc sestamibi with 8-frame gating in 62 consecutive patients. In addition to computation of left ventricular ejection fraction (LVEF), a new computerized method for quantifying, displaying and automatically grading regional data was developed. Regional function was quantified as wall motion, regional EF, and imaged based, count based, and normalized per cent wall thickenings (%WTs). Regional perfusion was assessed as a relative per cent peak count. Data were displayed on a 25-segmented polar map and automatically graded with a 5-point scale, and then summed scores were calculated. These quantitative parameters were compared to data from radionuclide ventriculography (RNV) and contrast left ventriculography. Gated SPECT had high reproducibilities for calculating global and regional ejection fractions and %WT indices (r=0.811-0.984, P<0.0001), but measurement of wall motion was less reproducible (r=0.555, SEE=7.9, P<0.011). LVEF estimated by gated SPECT and summed perfusion scores correlated closely (P<0.0001) with angiographic LVEF. Among the summed function indices that correlated closely with LVEF, normalized %WT had the closest correlations with LVEF estimated by RNV (r=0.657, P<0.0001) and by gated SPECT (r=0.778, P<0.0001). Assessment by visual reviewing of cine-mode playback or by normalized %WT had greater overall sensitivity, specificity, and positive and negative predictive values for detecting impaired regional function among the functional parameters: 71%, 79%, 63% and 84% for cine format analysis, and 78%, 73%, 59% and 87% for normalized %WT, respectively. Thus, besides LVEF, quantitative gated SPECT can provide reproducible and reliable quantitative data on regional perfusion and function. Automated summed scores obtained by gated SPECT can reflect integrated abnormalities of regional perfusion and function of the left ventricle. Both visual analyses by cine-mode display and a functional map of normalized wall thickening have greater diagnostic values for detecting regional function deficit related to coronary artery disease.