الفهرس 
Acquisition, Processing, attenuation correctionOnly 14 pages are availabe for public view
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Abstract
Artifacts are a significant source of false-positive interpretations of myocardial perfusion single-photon emission computed tomography (SPECT) especially in the non-gated studies and so many patients are referred for unnecessary catheterization. Combination of myocardial perfusion imaging and the pulsed wave tissue doppler imaging may help in differentiating the attenuation artifacts from the true perfusion defects especially in non –gated studies.
Aim of the work
Is to identify the relation between regional myocardial perfusion defects observed in the Tc99m MIBI SPECT study and the regional systolic and diastolic left ventricular functions observed in (PW-TDI)
Subjects and methods
This study included 60 consecutive patients referred to the nuclear cardiac laboratory of Ain Shams University Hospital as well as 10 patients with normal coronary angiography and normal myocardial perfusion served as control.
Exclusion criteria
• Patients with previous myocardial infarction referred for viability study.
• Patients with technically difficult echocardiography.
• Patients with atrial fibrillation, paced rhythm, intraventricular conduction disturbance, sustained supraventricular or ventricular arrhythmias.
• Patients with valvular heart diseases (except mitral regurgitation of ischemic origin but not exceeding mild degree).
• Patients with hypertrophic obstructive cardiomyopathy.
• Patients with LVH at baseline TTE study (SWT or PWT > 1.1 cm).
• Patients unable to exercise
All patients were subjected to the following: Clinical Assessment-Resting ECG- Echocardiographic examination-Technetium-99m Sestamibi SPECT imaging (stress and rest)-Examination with Pulsed wave Tissue Doppler Imaging- Coronary angiography for the patients with reversible perfusion defects diagnosed as ischemic defects.
Results
LV segments in Group I [ischemic patients] exhibited significantly lower e wave (p=0.002), e/a ratio (p=0.0002), & S wave (p=0.03) and higher a wave (P=0.003) TDI velocities as compared to Group II [Attenuation defects].
Segments presumed to be attenuation artifacts were compared with the corresponding segments in the control group. There was no significant difference as regards systolic and diastolic velocities.
Segments in Group I [LAD] [Ischemic with LAD lesion] exhibited significantly lower e wave (P=0.001), e/a ratio (P=0.0002) & S wave (P=0.02) and significantly higher a wave (P=0.002) TDI velocity compared to the control group. Segments in Group I [RCA] [Ischemic with RCA lesion] exhibited significantly lower e wave (P=0.002), e/a ratio (P=0.0001) & S wave (P=0.03) and significantly higher a wave (P=0.003) TDI velocity compared to the control group.
This study showed that e wave ≤8.8 cm/s a wave velocity ≥ 8.13 cm/s, e/a ≤ 1.1, & S wave velocity ≤ 7.0 cm/s were associated with sensitivity 62%,95.7%,63%,&64% respectively as well as specifity of 100%,56%,99%,&90% respectively to detect ischemia.
Discussion:
Artifacts and normal variants are a significant source of false-positive interpretations of myocardial perfusion single-photon emission computed tomography (SPECT). Tissue Doppler Imaging facilitates the quantitative assessment of the regional systolic and diastolic left ventricular functions. Combination of both techniques can increase the specificity of the SPECT and avoid unnecessary catheterization of normal patients.
In this study, the ischemic segments exhibited significantly lower e/a ratio (p=0.0002) & S wave (p=0.02) of TDI velocities as compared to the control.
This is supported by the study of Garcia-Fernandez et al who reported several differences between diseased and normal wall segments: the mean velocity (e wave) was reduced (P < 0.01); the e/a diastolic velocity ratio was decreased (P < 0.01) (159). During ischemia, the a wave velocity (that depends on the atrial contraction) is less prone to show alteration than the e wave (163). We found that the statistical difference between a wave velocity (p=0.002) in ischemic group as compared to the control was less than that observed for the e wave (p=0.001). This may be explained by the fact that a wave is less prone to show alteration than e wave during ischemia.
In this study, a cutoff value of regional e wave velocity ≤ 8.8 cm/s had a sensitivity of 62 % and a specifity of 100 % to detect ischemic myocardial segments. On the other hand, a cutoff value of ≤ 1.1has a sensitivity of 63 % and a specifity of 99% to detect the ischemic myocardial segments. Regional a wave velocity with a cutoff value of ≥ 8.13 cm/s had a sensitivity of 95.7% and a specifity of 56 % to detect the ischemic myocardial segments. Of these three indices, e/a ratio offered the advantage of being not influenced by the Doppler limitation of angle-dependence (159). Finally, regional S wave velocity ≤ 7.0 cm/s had sensitivity of 64.3 % and specifity of 90 %. There is no general agreement in the literature as regards the sensitivity and the specifity of various PW-TDI measurements in detecting ischemic changes, especially the systolic velocity. Garcia et al, reported that an S wave velocity < 12 cm/s was associated with 86% sensitivity and 96% specifity (169) whereas in another study by El Noamany et al, S wave velocity< 12 cm/s was associated with 96.3% sensitivity and 50% specifity (170).
Conclusion:
The clinical profile of the patient in addition to the inclusion of more than one segment in the perfusion defect help to differentiate ischemic defect from attenuation artifact .PW-TDI allowed the differentiation of attenuation artifacts from ischemic perfusion defects.