Impact of nuclear cardiology in clinical decision making (Part1)

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. Read more

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. Read more

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. Read more

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 . Read more

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.

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.