In vivo assessment of myocardial viability after acute myocardial infarction: A head-to-head comparison of the perfusable tissue index by PET and delayed contrast-enhanced CMR

Abstract

Background Early recognition of viable myocardium after acute myocardial infarction (AMI) is of clinical relevance, since affected segments have the potential of functional recovery. Delayed contrast-enhanced magnetic resonance imaging (DCE-CMR) has been validated extensively for the detection of viable myocardium. An alternative parameter for detecting viability is the perfusable tissue index (PTI), derived using [15O]H2O positron emission tomography (PET), which is inversely related to the extent of myocardial scar (non-perfusable tissue). The aim of the present study was to investigate the predictive value of PTI on recovery of LV function as compared to DCE-CMR in patients with AMI, after successful percutaneous coronary intervention (PCI).Methods Thirty-eight patients with ST elevation myocardial infarction (STEMI) successfully treated by PCI were prospectively recruited. Subjects were examined 1 week and 3 months (mean follow-up time: 97 ± 10 days) after AMI using [15O]H2O PET and DCE-CMR to assess PTI, regional function and scar. Viability was defined as recovery of systolic wall thickening ≥3.0 mm at follow-up by use of CMR. A total of 588 segments were available for serial analysis.ResultsAt baseline, 180 segments were dysfunctional and exhibited DCE. Seventy-three (41%) of these dysfunctional segments showed full recovery during follow-up (viable), whereas 107 (59%) segments remained dysfunctional (nonviable). Baseline PTI of viable segments was 0.94 ± 0.09 and was significantly higher compared to nonviable segments (0.80 ± 0.13, P < .001). The optimal cut-off value for PTI was ≥0.85 with a sensitivity of 85% and specificity of 72%, and an area under the curve (AUC) of 0.82. In comparison, a cut-off value of <32% for the extent of DCE resulted in a sensitivity of 72% and a specificity of 69%, and an AUC of 0.75 (AUC PTI vs DCE P = .14).ConclusionAssessment of myocardial viability shortly after reperfused AMI is feasible using PET. PET-derived PTI yields a good predictive value for the recovery of LV function in PCI-treated STEMI patients, in excellent agreement with DCE-CMR.

Assessment of myocardial viability with [15O]water PET: A validation study in experimental myocardial infarction

“…Both PTF and PTI have been shown to predict recovery of contractile function after revascularization in patients with MI with threshold values of at least 0.7 of the remote region. 10,[12][13][14]17,18 Our results are comparable to previous studies indicating that segmental PTF \ 0.66 and PTI \ 0.82 accurately detected non-viable myocardial segments defined as infarct volume fraction of C 75% in the corresponding segment. The original model measures MBF in water-exchanging myocardium and is independent of ROI thickness.…”

“…5 Reduced MBF by [ 15 O]water PET during vasodilator stress accurately detects regions of myocardial ischemia in patients with chest pain and suspected obstructive CAD. [6][7][8][9] Differentiation between viable and non-viable myocardium by [ 15 O]water PET is based on the concepts of reduced fraction of tissue that is capable of rapidly exchanging water [10][11][12][13][14] as well as low and heterogeneous MBF 11,[15][16][17] in the injured myocardial regions. Thus, water-perfusable tissue fraction (PTF) that is defined as the fraction of tissue capable of rapidly exchanging [ 15 O]water within a given volume of region of interest (ROI) as well as perfusable tissue index (PTI) that is the fraction of [ 15 O]water-perfusable tissue within the total anatomical tissue fraction (ATF) within the ROI containing both perfusable and non-perfusable tissue components, become reduced in the absence of viable myocardium.…”

“…Thus, water-perfusable tissue fraction (PTF) that is defined as the fraction of tissue capable of rapidly exchanging [ 15 O]water within a given volume of region of interest (ROI) as well as perfusable tissue index (PTI) that is the fraction of [ 15 O]water-perfusable tissue within the total anatomical tissue fraction (ATF) within the ROI containing both perfusable and non-perfusable tissue components, become reduced in the absence of viable myocardium. 4,[10][11][12][13][14]18 Both PTF and PTI have been shown to predict the recovery of contractile function after revascularization in patients with acute 13,18 or chronic myocardial infarction (MI). 10,12,14,17 Resting MBF by [ 15 O]water PET is reduced in areas of recent or chronic MI, 11,[15][16][17] but its value in the assessment of viability is not well defined.…”

Early risk stratification using Rubidium-82 positron emission tomography in STEMI patients

“…22 This finding is in line with our results, where extent of severe hypoperfusion was predictive of the LGE transmurality at follow-up.…”

The complexity of using resting myocardial perfusion to assess myocardial viability and predict functional recovery

“…1 While viability could be assessed without the need for additional advanced imaging with such an approach, prior results based upon quantifying resting flow have been variable with limited data available to establish the predictive ability of specific parameters in individual patients. [7][8][9][10][11][12][13] In this issue of the Journal, Benz and colleagues determined whether quantitative PET parameters can differentiate viable dysfunctional myocardium from scar in patients with ischemic cardiomyopathy. 14 Since 13 NH3 is actively metabolized by cells, modeling tracer kinetics beyond the initial uptake can characterize retention within viable cardiac myocytes.…”