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About myocardial viability in dysfunctioning myocardium, evaluation of coronary flow reserve, feasibility of evaluation of ischemia with ultrafast SPECT and finally impact of nuclear medicine in women.
N Engl J Med. 2011 Apr 28;364(17):1617-25. Epub 2011 Apr 4.
Bonow RO, Maurer G, Lee KL, et al; STICH Trial Investigators. Myocardial viability and survival in ischemic left ventricular dysfunction.
In this article, the Authors analyzed the impact of myocardial viability on survival in a population of patients with left ventricular dysfunction randomized to CABG or medical therapy.
Single-photon-emission computed tomography (SPECT), dobutamine echocardiography, or both were used to assess myocardial viability on the basis of prespecified thresholds.
Among the 1212 patients enrolled in the randomized trial, 601 underwent assessment of myocardial viability. Of these patients, 298 were randomly assigned to receive medical therapy plus CABG and 303 to receive medical therapy alone. A total of 178 of 487 patients with viable myocardium (37%) and 58 of 114 patients without viable myocardium (51%) died (hazard ratio for death among patients with viable myocardium, 0.64; 95% confidence interval [CI], 0.48 to 0.86; P=0.003). However, after adjustment for other baseline variables, this association with mortality was not significant (P=0.21). There was no significant interaction between viability status and treatment assignment with respect to mortality (P=0.53).
The Authors concluded that the presence of viable myocardium was associated with a greater likelihood of survival in patients with coronary artery disease and left ventricular dysfunction, but this relationship was not significant after adjustment for other baseline variables. The assessment of myocardial viability did not identify patients with a differential survival benefit from CABG, as compared with medical therapy alone.
Incremental prognostic value of coronary flow reserve assessed with single-photon emission computed tomography.
J Nucl Cardiol. 2011 Aug;18(4):612-9. Epub 2011 May 28.
Daniele S, Nappi C, Acampa W, et al.
The Authors assessed the prognostic value of coronary flow reserve (CFR) estimated by single-photon emission computed tomography (SPECT) in patients with suspected myocardial ischemia.
At this purpose, myocardial perfusion and CFR were assessed in 106 patients using dipyridamole/rest Tc-99m sestamibi SPECT and follow-up was obtained in 103 (97%) patients. Four early revascularized patients were excluded and 99 were assigned to normal (summed stress score <3) vs abnormal myocardial perfusion and to normal (≥2.0) vs abnormal CFR. During the follow-up (5.8 ± 2.1 years), 28 patients experienced a cardiac event. Abnormal perfusion (P < .01) and abnormal CFR (P < .05) were independent predictors of cardiac events at Cox proportional hazard regression analysis. Also in patients with normal perfusion, abnormal CFR was associated with a higher annual event rate compared with normal CFR (5.2% vs 0.7%; P < .05). CFR data improved the prognostic power of the model including clinical and myocardial perfusion data increasing the global chi-square from 18.6 to 22.8 (P < .05). Finally, at parametric survival analysis, in patients with normal perfusion the time to achieve ≥2% risk of events was >60 months in those with normal and <12 months in those with abnormal CFR.
In conclusions, myocardial perfusion findings and CFR at SPECT imaging are both independent predictors of cardiac events. Estimated CFR provides incremental prognostic information over those obtained from clinical and myocardial perfusion data, particularly in patients with normal perfusion findings.
Nuclear myocardial perfusion imaging with a novel cadmium-zinc-telluride detector SPECT/CT device: first validation versus invasive coronary angiography
Fiechter M, Ghadri JR, Kuest SM, et al. .
Eur J Nucl Med Mol Imaging. 2011 Jul 15. [Epub ahead of print]
The Authors evaluated the diagnostic accuracy of attenuation corrected nuclear myocardial perfusion imaging (MPI) with a novel hybrid ultrafast dedicated cardiac gamma camera with cadmium-zinc-telluride (CZT) detectors integrated onto a multislice CT scanner to detect coronary artery disease (CAD). Invasive coronary angiography served as the standard of reference.
The study population included 66 patients (79% men; mean age 63±11 years) who underwent 1-day (99m)Tc-tetrofosmin pharmacological stress/rest examination and angiography within 3 months.
The prevalence of angiographic CAD in the study population was 82%. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 87, 67, 92, 53 and 83%, respectively.
In conclusions, in this first report on CZT SPECT/CT MPI comparison versus angiography a high accuracy for detection of angiographically documented CAD was confirmed.
Comparative Effectiveness of Exercise Electrocardiography With or Without Myocardial Perfusion Single Photon Emission Computed Tomography in Women With Suspected Coronary Artery Disease: Results From the What Is the Optimal Method for Ischemia Evaluation in Women (WOMEN)
Shaw LJ, Mieres JH, Hendel RH, et al, for the WOMEN Trial Investigators. Trial. Circulation. 2011 Aug 15. [Epub ahead of print]
Up to now, it remains unclear whether the addition of myocardial perfusion imaging (MPI) to the standard ECG exercise treadmill test (ETT) provides incremental information to improve clinical decision making in women with suspected CAD. To this aim, the Authors randomized symptomatic women with suspected CAD, an interpretable ECG, and ≥5 metabolic equivalents on the Duke Activity Status Index to 1 of 2 diagnostic strategies: ETT or exercise MPI. The primary end point was 2-year incidence of major adverse cardiac events, defined as CAD death or hospitalization for an acute coronary syndrome or heart failure. A total of 824 women were randomized to ETT or exercise MPI. For women randomized to ETT, ECG results were normal in 64%, indeterminate in 16%, and abnormal in 20%. By comparison, the exercise MPI results were normal in 91%, mildly abnormal in 3%, and moderate to severely abnormal in 6%. At 2 years, there was no difference in major adverse cardiac events (98.0% for ETT and 97.7% for MPI; P=0.59). Compared with ETT, index testing costs were higher for exercise MPI (P<0.001), whereas downstream procedural costs were slightly lower (P=0.0008). Overall, the cumulative diagnostic cost savings was 48% for ETT compared with exercise MPI (P<0.001). In conclusions, in low-risk, exercising women, a diagnostic strategy that uses ETT versus exercise MPI yields similar 2-year posttest outcomes while providing significant diagnostic cost savings. The ETT with selective follow-up testing should be considered as the initial diagnostic strategy in symptomatic women with suspected CAD.
Impact of ischaemia and scar on the therapeutic benefit derived from myocardial revascularization vs. medical therapy among patients undergoing stress-rest myocardial perfusion scintigraphy.
Hachamovitch R, Rozanski A, Shaw LJ, et al.
Eur Heart J. 2011 Jan 21.
In this paper, Hachamovitch et al analyzed the interaction between the extent of ischaemia and myocardial scar with performance of revascularization on patient survival. A large number of 13 969 patients were evaluated using adenosine or exercise stress SPECT myocardial perfusion scintigraphy. In this large observational series with long-term follow-up, patients with significant ischaemia and without extensive scar were likely to realize a survival benefit from early revascularization. In contrast, the survival of patients with minimal ischaemia was superior with medical therapy without early revascularization.
Detection of silent myocardial ischemia in asymptomatic patients with diabetes: results of a randomized trial and meta-analysis assessing the effectiveness of systematic screening.
Lièvre MM, Moulin P, Thivolet C et al. Trials. 2011 Jan 26; 12: 23.
DYNAMIT was a prospective, randomized, open, blinded end-point multicenter trial run between 2000 and 2005, with a 3.5 year mean follow-up in ambulatory care in 45 French hospitals. The patients were randomized centrally to either screening for silent ischemia using a bicycle exercise test or Dipyridamole Single Photon Emission Computed Tomography (N = 316), or follow-up without screening (N = 315). These results suggest that the systematic detection of silent ischemia in high-risk asymptomatic patients with diabetes is unlikely to provide any major benefit on hard outcomes in patients whose cardiovascular risk is controlled by an optimal medical treatment.
Improved outcome prediction by SPECT myocardial perfusion imaging after CT attenuation correction.
Pazhenkottil AP, Ghadri JR, Nkoulou RN et al. J Nucl Cardiol 2011; 52: 166-200.
The aim of this study was to determine the impact of attenuation correction with CT (CT-AC) on the prognostic value of SPECT myocardial perfusion imaging (SPECT MPI) in 876 consecutive patients undergoing a 1-d stress-rest (99m)Tc-tetrofosmin SPECT MPI study. CT-AC for SPECT MPI allows improved risk stratification. At a mean follow-up of 2.3 ± 0.6 y, a summed stress score (SSS) of 0-3 best distinguished patients with a low major aderse cardiac event (MACE) rate (0.6%), followed by an SSS of 4-8 (4.3%), with increased MACE rate, and an SSS of 9-13 (3.8%), which was comparable. By contrast, with CT-AC the discrimination of low from intermediate MACE rate was best observed between an SSS of 0 (0%) and an SSS of 1-3 (3.7%), with a plateau at an SSS of 4-8 (3.2%). The prognostically relevant SSS cutoff is shifted toward lower values.
Relationship between infarct size and severity measured by gated SPECT and long-term left ventricular remodelling after acute myocardial infarction.
Berti V, Sciagrà R, Acampa W, et Colleagues. Eur J Nucl Med Mol Imaging 2011; Feb 15
This study aimed to investigate by gated SPECT the long-term evolution of myocardial perfusion and LV function after AMI and to identify the predictors of LV remodelling. Sixty-eight AMI patients successfully treated by primary percutaneous coronary intervention underwent (99m)Tc-sestamibi gated SPECT at 1 month (baseline) and over 6-month follow-up after the acute event. LV remodelling was defined as 20% increase in LV end-diastolic volume at follow-up. Perfusion parameters assessed by gated SPECT in the subacute phase after successfully treated AMI correlate with changes in functional parameters at long-term follow-up. Infarct severity is more effective than infarct size, but both are helpful for predicting LV remodelling.
STICH trial: Coronary Artery Bypass Graft Surgery in Patients with Ischemic Heart Failure
STICH trial tested the hypothesis that assessment of myocardial viability identified patients with CAD and LV dysfunction who had the greatest survival benefit with CABG compared to aggressive medical therapy. 1,212 patients from the STICH revascularization study underwent imaging tests: SPECT or dobutamine echo. Viability was determined for those with usable test results. Over 6 years of follow-up, no significant difference in characteristics or mortality within each subgroup based on medical therapy vs. CABG. Those with viability had a 36% reduced risk in all cause mortality (HR 0.64; 95% CI 0.48, 0.86; P=0.003).
In conclusion, in patients with CAD and LV dysfunction, assessment of myocardial viability does not identify patients who will have the greatest survival benefit from adding CABG to aggressive medical therapy. However, assessment is useful in identifying the risk of patients and getting information about prognosis.
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