Acute Myocardial Infarction Early Viability Assessment by 64-Slice Computed Tomography Immediately After Coronary Angiography

The Value of Three-Dimensional Speckle-Tracking Echocardiography in the Prediction of Cardiovascular Events in Patients with Hypertension Complicated by Acute Myocardial Infarction: A Long-Term Follow-Up Study

Background

Patients with hypertension complicated by acute myocardial infarction (AMI) have a generally poor prognosis. The identification of powerful predictors for recurring cardiovascular events (RCEs) is vital. This study seeks to evaluate the predictive value of three-dimensional (3D) strain parameters for RCEs in patients with hypertension complicated by AMI.

Methods

We successfully followed up patients with hypertension and AMI from April 2015 to December 2015 in this retrospective study. Participants previously underwent 3D echocardiography, one week, and one month after percutaneous coronary intervention (PCI). The left ventricular structural function parameters, as well as 3D strain parameters including 3D global longitudinal strain (3D-GLS), 3D global circumferential strain, 3D global radial strain, and 3D global area strain (3D-GAS), were acquired. A Cox model was used to determine the relationships between these parameters and RCEs.

Results

In total, 62 patients were enrolled in the analysis. During follow-up (41.27 ± 20.45 months), 20 patients (32.3%) had RCEs that were independently predicted one month after PCI by 3D-GLS (HR: 1.481, 95% CI: 1.202–1.824, P < 0.001) and 3D-GAS (HR: 1.254, 95% CI: 1.093–1.440, P = 0.001). The optimal cutoffs for 3D-GLS and 3D-GAS in predicting cardiac events were ≥12.5% (area under the receiver operating characteristic curve [AUC]: 0.736, 95% CI: 0.611–0.862, P = 0.003), and >20.5% (AUC: 0.685, 95% CI: 0.551–0.818, P = 0.020), respectively.

Conclusion

The assessed values of 3D-GLS and 3D-GAS one month after PCI can predict RCEs in patients with hypertension complicated by AMI.

Enhancement patterns detected by multidetector computed tomography are associated with the long-term prognosis of patients with acute myocardial infarction

The present study investigated the clinical value of myocardial contrast-delayed enhancement (DE) with multidetector computed tomography (MDCT) without iodine re-injection immediately after primary percutaneous coronary intervention (PCI) for predicting future cardiovascular events after acute myocardial infarction (AMI). We performed a prospective study in which 263 consecutive patients with first AMI successfully treated with primary PCI were enrolled. Sixty-four-slice MDCT without the re-injection of contrast medium was performed immediately after PCI. Myocardial DE was considered to be transmural when involving myocardial thickness ≥ 75% (Group A; n = 104), subendocardial (< 75%, Group B; n = 108), or normal (Group C; n = 51). A semiquantitative scale score was defined for 17 left ventricular segments to investigate the extent of the DE area assessed. We examined the relationship between the presence or absence of transmural DE and long-term cardiovascular event rates. The median follow-up period was 3.5 years. Kaplan-Meier survival curves showed that patient prognosis was poorer in the group with Group A than that in the group with Group B, which was equivalent to that with Group C. A multivariate analysis identified the presence of transmural DE as the strongest predictor for future cardiovascular events (hazard ratio: 3.7; P = 0.023). Transmural myocardial DE immediately following primary PCI without an iodine re-injection for AMI is a major risk factor for future cardiovascular events.

Impact of delayed hyperenhancement obtained by non-contrast computed tomography following coronary angiography in patients undergoing extracorporeal cardiopulmonary resuscitation

Background

Extracorporeal cardiopulmonary resuscitation (ECPR) has the potential to improve outcomes in patients with refractory cardiac arrest. However, the outcome is difficult to predict on admission. Recent reports have described early evaluation of myocardial damage in patients with acute myocardial infarction by detecting delayed enhancement in non-contrast computed tomography (CT) following coronary angiography (CAG). We investigated the impact of delayed hyperenhancement obtained by non-contrast CT following CAG in patients with ischaemic and non-ischaemic cardiovascular diseases who underwent ECPR for refractory cardiac arrest.

Methods

Forty-two patients who underwent ECPR, CAG, and postprocedural CT for refractory cardiac arrest in our institute were retrospectively enrolled. Two blinded readers independently and semi-quantitatively judged whether hyperenhancement was present or absent in non-contrast axial CT images following CAG. We evaluated the relationship between in-hospital death and delayed hyperenhancement.

Results

The identification of delayed hyperenhancement was highly consistent between the two readers (kappa ​= ​0.71). The survival rate was 21.4% in this cohort. The only significant difference between the survival group and in-hospital death group was the presence of delayed hyperenhancement, which was detected only in the in-hospital death group (p ​= ​0.03). The prevalence of cardiac death was higher in patients with than without delayed hyperenhancement. Delayed hyperenhancement was observed even in areas perfused by non-obstructive coronary arteries.

Conclusions

Delayed hyperenhancement of the left ventricular wall on non-contrast CT imaging following CAG might help to predict in-hospital death in patients undergoing ECPR for refractory cardiac arrest.

Computed tomography of cardiomyopathies

Cardiac computed tomography (CT) is increasingly used in the evaluation of cardiomyopathies, particularly in patients who are not able to undergo other non-invasive imaging tests such as magnetic resonance imaging (MRI) due to the presence of MRI-incompatible pacemakers/defibrillators or other contraindications or due to extensive artifacts from indwelling metallic devices. Advances in scanner technology enable acquisition of CT images with high spatial resolution, good temporal resolution, wide field of view and multi-planar reconstruction capabilities. CT is useful in cardiomyopathies in several ways, particularly in the evaluation of coronary arteries, characterization of cardiomyopathy phenotype, quantification of cardiac volumes and function, treatment-planning, and post-treatment evaluation. In this article, we review the imaging techniques and specific applications of CT in the evaluation of cardiomyopathies.

Infarct characterization using CT

Myocardial infarction (MI) is a major cause of death and disability worldwide. The incidence is not expected to diminish, despite better prevention, diagnosis and treatment, because of the ageing population in industrialized countries and unhealthy lifestyles in developing countries. Nowadays it is highly requested an imaging tool able to evaluate MI and viability. Technology improvements determined an expansion of clinical indications from coronary plaque evaluation to functional applications (perfusion, ischemia and viability after MI) integrating additional phases and information in the mainstream examination. Cardiac computed tomography (CCT) and cardiac MR (CMR) employ different contrast media, but may characterize MI with overlapping imaging findings due to the similar kinetics and tissue distribution of gadolinium and iodinated contrast media. CCT may detect first-pass perfusion defects, dynamic perfusion after pharmacological stress, and delayed enhancement (DE) of non-viable territories.

Non-contrast cardiac CT immediately after percutaneous coronary intervention: does it predict the risk of left ventricular remodeling in patients with ST-elevation myocardial infarction?

To assess the clinical utility of non-contrast cardiac CT (CCT) immediately after successful percutaneous coronary intervention (PCI) for predicting the risk of left ventricle (LV) remodeling in the management of patients with acute myocardial infarction (AMI), 35 patients with AMI underwent non-contrast CCT immediately after PCI. Volume and transmural extent of myocardial delayed enhancement (DE) were assessed on non-contrast CCT. Serial echocardiography and serologic biomarkers were evaluated at baseline and at 2 and 12 months after AMI. Based on an increase in left ventricular end-diastolic volume (LVEDV) ≥20 % at 2 months, patients were classified into two groups: LV remodeling (group 1, n = 14) and no LV remodeling (group 2, n = 21). Clinical characteristics, imaging parameters, and serologic biomarkers were compared between the two groups. Higher incidence of hypertension, longer time to reperfusion, and higher Killip classification at admission were observed for group 1 than for group 2, but these differences were not statistically significant (P > 0.05). Greater volume and transmural extent of DE on non-contrast CCT and poorer resolution of ST-segment elevation on ECG were observed in group 1 compared to group 2, but these results were not statistically significant (P > 0.05). Measurement of biochemical markers showed that probrain natriuretic peptide (proBNP), initial high sensitivity C reactive protein (hs-CRP), and maximum troponin T level were significantly higher in group 1 than in group 2 (P < 0.05) at 2 months. Based on the trend of greater volume and transmural extent of DE in group 1 compared to group 2, non-contrast CCT immediately after PCI, in combination with serologic biomarkers (proBNP, hs-CRP, and troponin T) might be useful for managing patients with AMI.

Early prediction of myocardial viability after acute myocardial infarction by two-dimensional speckle tracking imaging

Background

Identifying the transmural extent of myocardial necrosis and the degree of myocardial viability in acute myocardial infarction (AMI) is important clinically. The aim of this study was to assess myocardial viability using two-dimensional speckle tracking imaging (2D-STI) in patients with AMI.

Methods

2D-STI was performed at initial presentation, three days, and six months after primary percutaneous coronary intervention (PCI) in 30 patients with AMI, who had a left anterior descending coronary artery (LAD) culprit lesion. In addition, 20 patients who had minimal stenotic lesions (< 30% stenosis) on coronary angiography were also included in the control group. At six months dobutamine echocardiography was performed for viability assessment in seven segments of the LAD territory. According to the recovery of wall motion abnormality, segments were classified as viable or non-viable.

Results

A total of 131 segments were viable, and 44 were nonviable. Multivariate analysis revealed significant differences between the viable and nonviable segments in the peak systolic strain, the peak systolic strain rate at initial presentation, and peak systolic strain rate three days after primary PCI. Among these, the initial peak systolic strain rate had the highest predictive value for myocardial viability (hazard ratio: 31.22, P < 0.01).

Conclusions

2D-STI is feasible for assessing myocardial viability, and the peak systolic strain rate might be the most reliable predictor of myocardial viability in patients with AMI.

Enhancement patterns detected by multidetector computed tomography are associated with microvascular obstruction and left ventricular remodelling in patients with acute myocardial infarction

AIMS

This study evaluated the clinical value of myocardial contrast-delayed enhancement (DE) with multidetector computed tomography (MDCT) for detecting microvascular obstruction (MVO) and left ventricular (LV) remodelling revealed by DE magnetic resonance imaging after acute myocardial infarction (AMI).

METHODS AND RESULTS

In 92 patients with first AMI, MDCT without iodine reinjection was performed immediately following successful percutaneous coronary intervention (PCI). Delayed-enhancement magnetic resonance imaging performed in the acute and chronic phases was used to detect MVO and LV remodelling (any increase in LV end-systolic volume at 6 months after infarction compared with baseline). Patients were divided into two groups according to the presence (n = 33) or absence (n = 59) of heterogeneous enhancement (HE). Heterogeneous enhancement was defined as concomitant presence of hyper- and hypoenhancement within the infarcted myocardium on MDCT. Microvascular obstruction and LV remodelling were detected in 49 (53%) and 29 (32%) patients, respectively. In a multivariable analysis, HE and a relative CT density >2.20 were significant independent predictors for MVO [odds ratio (OR) 13.5; 95% confidence interval (CI), 2.15-84.9; P = 0.005 and OR 12.0; 95% CI, 2.94-49.2; P < 0.001, respectively). The presence of HE and relative CT density >2.20 showed a high positive predictive value of 93%, and the absence of these two findings yielded a high negative predictive value of 90% for the predictive value of MVO. Heterogeneous enhancement was significantly associated with LV remodelling (OR 6.75; 95% CI, 1.56-29.29; P = 0.011).

CONCLUSION

Heterogeneous enhancement detected by MDCT immediately after primary PCI may provide promising information for predicting MVO and LV remodelling in patients with AMI.

Role of cardiac multidetector computed tomography beyond coronary angiography

Cardiac multidetector computed tomography (MDCT) has become a useful noninvasive modality for anatomical imaging of coronary artery disease (CAD). Currently, the main clinical advantage of coronary computed tomography angiography (CCTA) appears to be related to its high negative predictive value at low or intermediate pretest probability for CAD. With the development of technical aspects of MDCT, clinical practice and research are increasingly shifting toward defining the clinical implication of plaque morphology, myocardial perfusion, and patient outcomes. The presence of positive vessel remodeling, low-attenuation plaques, napkin-ring sign, or spotty calcification on CCTA could be useful information on high-risk vulnerable plaques. The napkin-ring sign, especially, showed higher accuracy for the detection of thin-cap fibroatheroma. Recently, it was reported that cardiac 3D single-photon emission tomography/CT fusion imaging, noninvasive fractional flow reserve computed from CT, and integrated CCTA and CT myocardial perfusion were associated with improved diagnostic accuracy for the detection of hemodynamically significant CAD. Furthermore, several randomized, large clinical trials have evaluated the clinical value of CCTA for chest pain triage in the emergency department or long-term reduction in death, myocardial infarction, or hospitalization for unstable angina. In this review we discuss the role of cardiac MDCT beyond coronary angiography, including a comparison with other currently available imaging modalities used to examine atherosclerotic plaque and myocardial perfusion.

Diagnostic performance of resting CT myocardial perfusion in patients with possible acute coronary syndrome

OBJECTIVE

Coronary CT angiography has high sensitivity, but modest specificity, to detect acute coronary syndrome. We studied whether adding resting CT myocardial perfusion imaging improved the detection of acute coronary syndrome.

SUBJECTS AND METHODS

Patients with low-to-intermediate cardiac risk presenting with possible acute coronary syndrome received both the standard of care evaluation and a research thoracic 64-MDCT examination. Patients with an obstructive (> 50%) stenosis or a nonevaluable coronary segment on CT were diagnosed with possible acute coronary syndrome. CT perfusion was determined by applying gray and color Hounsfield unit maps to resting CT angiography images. Adjudicated patient diagnoses were based on the standard of care and 3-month follow-up. Patient-level diagnostic performance for acute coronary syndrome was calculated for coronary CT, CT perfusion, and combined techniques.

RESULTS

A total of 105 patients were enrolled. Of the nine (9%) patients with acute coronary syndrome, all had obstructive CT stenoses but only three had abnormal CT perfusion. CT perfusion was normal in all other patients. To detect acute coronary syndrome, CT angiography had 100% sensitivity, 89% specificity, and a positive predictive value of 45%. For CT perfusion, specificity and positive predictive value were each 100%, and sensitivity was 33%. Combined cardiac CT and CT perfusion had similar specificity but a higher positive predictive value (100%) than did CT angiography.

CONCLUSION

Resting CT perfusion using CT angiographic images may have high specificity and may improve CT positive predictive value for acute coronary syndrome without added radiation and contrast. However, normal resting CT perfusion cannot exclude acute coronary syndrome.

Acute myocardial infarction: early CT aspects of myocardial microcirculation obstruction after percutaneous coronary intervention

OBJECTIVE

To evaluate the capabilities of delayed enhanced multidetector CT (DE-MDCT), performed immediately after percutaneous coronary intervention (PCI), in predicting myocardial microvascular obstruction (MVO) formation assessed by delayed enhanced MRI (DE-MRI).

METHODS

Thirty-two patients presenting with a primary acute myocardial infarction, successfully recanalised by PCI, underwent a DE-MDCT immediately after PCI and a DE-MRI within 1 week. The left ventricle was split into 64 subsegments, rated as "healthy", "infarcted" or "MVO" on DE-MRI. Their mean density was measured on DE-MDCT and calculated relative to the patient's mean healthy myocardium density. Hypoenhanced DE-MDCT subsegments, termed "CT early MVO", were also recorded. Sensitivity and specificity of DE-MDCT for MRI-assessed "MVO" subsegments detection was calculated for mean CT relative density (threshold determined from a ROC analysis), "CT early MVO" and both.

RESULTS

Mean CT relative density was higher in MRI-assessed "MVO" than in "infarcted" and "healthy" subsegments (1.82 ± 0.46, 1.43 ± 0.36 and 1.0 ± 0.13 respectively; P < 0.001) leading to a sensitivity and specificity of 94.3 % and 89.2 % for a cutoff of 1.36. Sensitivity and specificity were respectively 16.9 % and 99.8 % for "CT early MVO" and 95.3 % and 89.3 % when considering the two patterns.

CONCLUSION

DE-MDCT, performed immediately after PCI, allows for an accurate prediction of MVO formation.

KEY POINTS

• Myocardial microvascular obstruction (MVO) is an important prognostic sequel following myocardial infarction. • MVO can be accurately predicted by multidector CT (MDCT). • Both hypo- and hyperenhanced myocardial areas can be analysed by MDCT. • MDCT may become a useful prognostic tool for acute MI outcome.

CT imaging of myocardial perfusion: possibilities and perspectives

Functional imaging in patients with suspected or known coronary artery disease (CAD) is crucial for the identification of patients who could benefit from coronary revascularization. Several studies demonstrated the high diagnostic accuracy of Single-photon-emission computed tomography myocardial perfusion imaging, stress perfusion magnetic resonance imaging, and of invasive FFR measurements for the detection of hemodynamic relevant stenosis. Cardiac computed tomography (CT) used to be limited to coronary angiography (CTA); current guidelines recommend CTA only for the exclusion of CAD. Technological advances now offer the possibility to assess myocardial perfusion by computed tomography (CT-MPI). Though different acquisition protocols and post-processing algorithms still have to be evaluated, initial clinical studies could already show a diagnostic accuracy comparable to the established imaging modalities. Thus, cardiac CT may offer a combined approach of anatomical and functional imaging. Beside the need for further studies, especially on the prognostic value of CT-MPI to stratify future cardiovascular events, the comparatively high radiation exposure and additional administration of contrast agent has to be taken in account.

Clinical experiences of delayed contrast enhancement with cardiac computed tomography: case series

Background

Myocardial delayed enhancement (MDE) by gadolinium-enhanced cardiac MRI is well established for myocardial scar assessment in ischemic and non-ischemic heart disease. The role of MDE by cardiac CT (CT-MDE) is not yet defined.

Findings

We reviewed all clinical cases of CT-MDE at a tertiary referral center to present the cases as a case series. All clinical cardiac CT exams which utilized CT-MDE imaging between January 1, 2005 and October 1, 2010 were collected as a series and their findings were also compared with available myocardial imaging to assess for myocardial abnormalities, including echocardiography (wall motion, morphology), cardiac MRI (delayed enhancement, morphology), SPECT MPI (perfusion defects). 5,860 clinical cardiac CT exams were performed during the study period. CT-MDE was obtained in 18 patients and was reported to be present in 9 patients. The indications for CT-MDE included ischemic and non-ischemic heart diseases. In segments positive for CT-MDE, there was excellent agreement of CT with other modalities: echocardiography (n=8) demonstrated abnormal morphology and wall motion (k=1.0 and k=0.82 respectively); prior MRI (n=2) demonstrated abnormal delayed enhancement (MR-MDE) (k=1.0); SPECT MPI (n=1) demonstrated fixed perfusion defects (k=1.0). In the subset of patients without CT-MDE, no abnormal segments were identified by echocardiography (n=8), MRI (n=1) and nuclear MPI (n=0).

Conclusions

CT-MDE was performed in rare clinical situations. The indications included both ischemic and non-ischemic heart disease and there was an excellent agreement between CT-MDE and abnormal myocardium by echocardiography, cardiac MRI, and nuclear MPI.

Prognostic value of myocardial contrast delayed enhancement with 64-slice multidetector computed tomography after acute myocardial infarction

OBJECTIVES

This study evaluated the clinical value of myocardial contrast delayed enhancement (DE) with multidetector computed tomography (MDCT) for predicting clinical outcome after acute myocardial infarction (AMI).

BACKGROUND

Although some studies have described the use of MDCT for assessment of myocardial viability after AMI, clinical experience remains limited.

METHODS

In 102 patients with first AMI, 64-slice MDCT without iodine reinjection was performed immediately following successful percutaneous coronary intervention (PCI). We measured the size of myocardial contrast DE on MDCT and compared it with clinical outcome. Primary composite cardiac events were cardiac death or hospitalization for worsening heart failure.

RESULTS

Among the 102 patients (24 ± 10 months follow-up), 19 patients experienced primary composite cardiac events (cardiac death, n = 7; heart failure, n = 12). Kaplan-Meier analysis showed higher risk of cardiac events for patients in the third tertile of myocardial contrast DE size (≥ 36 g) than for those in the other 2 tertiles (p < 0.0001). Multivariable Cox proportional hazards regression analysis indicated that myocardial contrast DE size (adjusted hazard ratio [HR] for tertile 3 vs. 1: 16.1, 95% confidence interval [CI]: 1.45 to 72.4, p = 0.022; HR for tertile 3 vs. 2: 5.06, 95% CI: 1.25 to 22.7, p = 0.039) was a significant independent predictor for cardiac events after adjustment for Thrombolysis In Myocardial Infarction risk score, left ventricular ejection fraction, total defect score on single-photon emission CT with technetium tetrofosmin, and transmural extent of myocardial contrast DE on MDCT.

CONCLUSIONS

Myocardial contrast DE size on MDCT immediately after primary PCI may provide promising information for predicting clinical outcome in patients with AMI.

Computed tomography imaging in myocardial infarction

Over recent decades, noninvasive imaging has become well established in the diagnostic work-up of patients suffering from myocardial infarction. It provides insights into the individual patient's prognosis and guides therapeutic decisions. MRI has long been considered the standard of reference in the noninvasive imaging of myocardial infarction. Only recently have different multidetector-row spiral computed tomography (MDCT) techniques successfully been evaluated for the visualization of myocardial infarction. This article describes different concepts of cardiac MDCT imaging in acute and chronic myocardial infarction. MDCT assessment of myocardial edema, myocardial perfusion and delayed myocardial contrast enhancement are introduced, with the latter evolving as key concept of viability imaging by means of MDCT. The current status of MDCT in the diagnostic work-up of myocardial infarction is reviewed.

Cardiac imaging after myocardial infarction

After myocardial infarction, optimal clinical management depends critically on cardiac imaging. Remodelling and heart failure, presence of inducible ischaemia, presence of dysfunctional viable myocardium, future risk of adverse events including risk of ventricular arrhythmias, need for anticoagulation, and other questions should be addressed by cardiac imaging. Strengths and weaknesses, recent developments, choice, and timing of the different non-invasive techniques are reviewed for this frequent clinical scenario.

Assessment of acute myocardial infarction: current status and recommendations from the North American society for Cardiovascular Imaging and the European Society of Cardiac Radiology

There are a number of imaging tests that are used in the setting of acute myocardial infarction and acute coronary syndrome. Each has their strengths and limitations. Experts from the European Society of Cardiac Radiology and the North American Society for Cardiovascular Imaging together with other prominent imagers reviewed the literature. It is clear that there is a definite role for imaging in these patients. While comparative accuracy, convenience and cost have largely guided test decisions in the past, the introduction of newer tests is being held to a higher standard which compares patient outcomes. Multicenter randomized comparative effectiveness trials with outcome measures are required.

Comparison of postprocessing techniques for the detection of perfusion defects by cardiac computed tomography in patients presenting with acute ST-segment elevation myocardial infarction

BACKGROUND

Despite rapid advances in cardiac computed tomography (CT), a strategy for optimal visualization of perfusion abnormalities on CT has yet to be validated.

OBJECTIVE

We evaluated the performance of several postprocessing techniques of source data sets to detect and characterize perfusion defects in acute myocardial infarctions with cardiac CT.

METHODS

Twenty-one subjects (18 men; 60 +/- 13 years) that were successfully treated with percutaneous coronary intervention for ST-segment myocardial infarction underwent 64-slice cardiac CT and 1.5 Tesla cardiac magnetic resonance imaging (MRI) scans after revascularization. Delayed enhancement MR images were analyzed to identify the location of infarcted myocardium. Contiguous short-axis images of the left ventricular myocardium were created from the CT source images with 0.75-mm multiplanar reconstruction (MPR), 5-mm MPR, 5-mm maximal intensity projection (MIP), and 5-mm minimum intensity projection (MinIP) techniques. Segments already confirmed to contain infarction by MRI were then evaluated qualitatively and quantitatively with CT.

RESULTS

Overall, 143 myocardial segments were analyzed. On qualitative analysis, the MinIP and thick MPR techniques had greater visibility and definition than the thin MPR and MIP techniques (P < 0.001). On quantitative analysis, the absolute difference in Hounsfield unit attenuation between normal and infarcted segments was significantly greater for the MinIP (65.4 Hounsfield unit [HU]) and thin MPR (61.2 HU) techniques. However, the relative difference in Hounsfield unit attenuation was significantly greatest for the MinIP technique alone (95%; P < 0.001). Contrast to noise was greatest for the MinIP (4.2) and thick MPR (4.1) techniques (P < 0.001).

CONCLUSION

The results of our current investigation found that MinIP and thick MPR detected infarcted myocardium with greater visibility and definition than MIP and thin MPR.

Myocardial viability imaging and revascularization in chronic ischemic left ventricular systolic dysfunction

The high rate of periprocedural morbidity and mortality associated with revascularization in moderate-to-severe left ventricular systolic dysfunction has provided the rationale for noninvasive viability imaging. The most established viability imaging techniques are PET, single-photon emission computed tomography and dobutamine echocardiography. Cardiac MRI is gaining widespread use and accessibility, and computed tomography is emerging as a promising technique. Each imaging modality has unique advantages but also suffers from limitations. Furthermore, evidence of the impact of viability imaging on patient outcomes has generally been limited to observational studies. Uncertainty remains regarding the optimal treatment strategy in this patient subset. This review describes the current status of viability imaging and revascularization in chronic moderate-to-severe ischemic left ventricular systolic dysfunction.

Viability imaging by cardiac computed tomography

First-pass perfusion and delayed enhancement cardiac imaging have been shown to be feasible by cardiac CT. However, questions remain about its reliability, and ideal scanning parameters have yet to be fully established. In general, scar imaging with cardiac CT typically requires 2 scans, with first-pass perfusion information derived from the same data set used to visualize the coronary arteries. Reduced contrast enhancement on first-pass cardiac CT images represents reduced perfusion. Higher doses of contrast are required to perform viability imaging by cardiac CT. Approximately 10 minutes after contrast administration, viability information is obtained by performing a second (noncontrast) scan. In addition to the concepts of perfusion and viability imaging by cardiac CT, we review parameters such as scan timing, tube settings, contrast delivery, reconstruction, and postprocessing techniques, as well as the associated pitfalls and technical limitations in perfusion and viability imaging by cardiac CT.

Negative contractile reserve with low-dose dobutamine in patients with ischemic cardiomyopathy investigated by gated myocardial perfusion SPECT

INTRODUCTION AND OBJECTIVES

To investigate negative contractile responses in the left ventricle during low-dose dobutamine (LDD) gated single-photon emission computed tomography (SPECT) in patients with ischemic cardiomyopathy.

METHODS

Sixty-eight consecutive patients (mean age, 60 + or - 11 years; 7 male) with ischemic cardiomyopathy (i.e., left ventricular ejection fraction [LVEF] < or = 40%) were evaluated using gated-SPECT at rest and during LDD infusion. Associations between a negative contractile reserve (i.e., a > or = 1-grade improvement in wall thickening score with LDD infusion) and scintigraphic viability criteria and coronary angiography findings were analyzed.

RESULTS

Some 42.6% (29/68) of patients had a negative contractile reserve in one or more segments. In 14.7% (n=10), the LVEF decreased by > or = 4% with LDD. These patients had more segments with a negative contractile reserve (2.8 + or - 2.5 vs. 0.87 + or - 0.40; P=.042), and the cut-off value on receiver operating characteristic curve analysis was > or =2 segments with a negative contractile reserve (sensitivity 70%, specificity 74%, positive likelihood ratio 2.71, negative likelihood ratio 0.40). Some 94% (74/79) of segments with a negative contractile reserve were in viable myocardium (i.e. normal or viable on scintigraphy). Twelve of 17 segments with akinesia or severe hypokinesia and a negative contractile reserve satisfied scintigraphic viability criteria, with the majority (10/12) lying in territories supplied by a patent coronary artery.

CONCLUSIONS

A negative contractile reserve was not uncommon in patients with ischemic cardiomyopathy and was associated with a general decrease in left ventricular systolic function. It was observed mainly in myocardial segments that appeared viable on scintigraphy and were supplied by a patent coronary artery.

Assessment of myocardial edema by computed tomography in myocardial infarction

OBJECTIVES

The aim of this study was to analyze whether cardiac computed tomography (CT) permits the assessment of myocardial edema in acute myocardial infarction (MI).

BACKGROUND

Several studies proved the value of detecting myocardial edema from T2-weighted cardiac magnetic resonance (CMR) for differentiating acute from chronic MI. Computed tomography is suited for depicting MI, but there are no data on CT imaging of myocardial edema. We hypothesized that areas of reduced attenuation in acute MI may correspond to edema.

METHODS

In 7 pigs (55.2 +/- 7.3 kg), acute MI was induced using a closed chest model. Animals underwent unenhanced arterial and late-phase dual source computed tomography (DSCT) followed by T2-weighted and delayed contrast-enhanced CMR. Animals were sacrificed, and the excised hearts were stained with 2,3,5-triphenyltetrazolin chloride (TTC). Size of MI, contrast-to-noise ratio, and percent signal difference were compared among the different imaging techniques with concordance-correlation coefficients (rho(c)), Bland-Altman plots, and analysis of variance for repeated measures.

RESULTS

Infarction was transmural on all slices. On unenhanced, arterial, and late-phase DSCT, mean sizes of MI were 27.2 +/- 8.5%, 20.1 +/- 6.9%, and 23.1 +/- 8.2%, respectively. Corresponding values on T2-weighted and delayed enhanced CMR were 28.5 +/- 7.8% and 22.2 +/- 7.7%. Size of MI on TTC staining was 22.6 +/- 7.8%. Best agreement was observed when comparing late-phase CT (rho(c) = 0.9356) and delayed enhanced CMR (rho(c) = 0.9248) with TTC staining. There was substantial agreement between unenhanced DSCT and T2-weighted CMR (rho(c) = 0.8629). Unenhanced DSCT presented with the lowest percent signal difference (46.0 +/- 18.3) and the lowest contrast-to-noise ratio (4.7 +/- 2.0) between infarcted and healthy myocardium.

CONCLUSIONS

Unenhanced DSCT permits the detection of myocardial edema in large acute MI. Further studies including smaller MI in different coronary artery territories and techniques for improving the contrast-to-noise ratio are needed.

Applications of cardiac multidetector CT beyond coronary angiography

Noninvasive imaging of the coronary arteries using multidetector CT (MDCT) represents one of the most promising diagnostic imaging advances in contemporary cardiology. This challenging application has driven a rapid and impressive advancement in CT technology over the past 10 years; leading to increased spatial and temporal resolution, decreased scan times and substantial reductions in radiation dose. Recent technological improvements have not only improved the status of CT coronary angiography but have also enabled new functional myocardial applications that are gaining a foothold in clinical practice as adjuncts or replacements for conventional coronary angiographic studies. Wide-detector CT designs along with prospective ECG-triggered protocols have opened the possibility of performing multiple complementary myocardial measurements during a coronary CT exam with acceptable radiation and contrast exposure. In this Review, we discuss recent technical developments in cardiac MDCT and outline newly enabled noncoronary cardiac applications including viability assessment, myocardial perfusion and molecular imaging.

[Technological advances in cardiac CT]

The SFR-SFC presents guidelines dedicated to cardiac and coronary imaging using CT in the area of indications, technological requirement including both hardware and software, patient conditioning, CT protocols and related results concerning radiation dose, image quality and diagnostic value. These guidelines are based either on up-dated medical literature proofs and/or on expert consensus.

Left ventricular myocardial volumes measured during arterial and delayed phases of multidetector row computed tomography: a study on intra- and interobserver variability

To compare and correlate left ventricular (LV) myocardial volumes obtained using arterial and delayed phases of multidetector row computed tomography (CT) and evaluate their intra- and interobserver variation. Two observers evaluated the arterial- and delayed-phase serial short-axis images of 45 healthy volunteers. Intra- and interobserver variations in LV myocardial volumes were correlated with four factors-myocardial volume, contrast-volume-to-body-weight ratio, and contrast-to-noise ratios in the arterial and delayed phases. Variations in the apex, mid-ventricle, and base were compared. Intra- and interobserver analyzes revealed no statistical difference and good correlation. Intra- and interobserver variations were within 5 and 10%, respectively, and were independent of the four factors. Variations were the highest at the apex. LV myocardial volumes measured using arterial- and delayed-phase cardiac CT exhibit no significant difference and good correlation. Intra- and interobserver variations are both clinically acceptable, and the apex contributes most to these variations.

Comparison of multidetector CT with F-18-FDG-PET and SPECT in the assessment of myocardial viability in patients with myocardial infarction: a preliminary study

OBJECTIVE

To evaluate the ability of MDCT to detect a nonviable myocardium in patients with myocardial infarction (MI).

METHODS AND MATERIAL

This study included 17 patients with MI in the acute (n=13) or chronic stage (n=4). MDCT, SPECT, and F-18-FDG-PET were performed in 10 patients during the acute stage and in 2 during the chronic stage of MI. MDCT and SPECT were performed in 13 patients with acute stage and in 4 with chronic stage of MI. Sixteen-slice MDCT was performed 10 min after injection of 120 mL of nonionic contrast media. MDCT, SPECT and PET images were analyzed using a 17-segment model. The depth of hyperenhancement >2/3 was defined as nonviable at MDCT.

RESULTS

MDCT and SPECT were concordant in localizing the MI in 84.2% (272/323 segments) and were discordant in 15.8% (51/323). MDCT and PET were concordant in localizing MI in 89.2% (182/204) and discordant in 10.8% (22/204). The sensitivity, specificity and diagnostic accuracy of MDCT in determining the nonviable segments were 70.4%, 85.3%, 81.4% as compared with PET, respectively, and 69.4%, 81.8%, 79.9% compared with SPECT, respectively, and 73.5%, 79.4%, 78.4% compared with combined PET and SPECT, respectively. MDCT findings suggested nonviability in additional 16 segments (5.0%) and 7 segments (3.4%) where MI was not detected on SPECT and FDG-PET, respectively.

CONCLUSION

MDCT is useful for determining myocardial viability in patients with myocardial infarction and more sensitive than SPECT and FDG-PET in detecting a nonviable myocardium.

Combined coronary and late-enhanced multidetector-computed tomography for delineation of the etiology of left ventricular dysfunction: comparison with coronary angiography and contrast-enhanced cardiac magnetic resonance imaging

Aims

To evaluate whether comprehensive evaluation of coronary anatomy and delayed enhancement (DE) by multidetector-computed tomography (MDCT) would allow determination of etiology of left ventricular dysfunction (LVD) as compared with coronary angiography (CA) and DE-magnetic resonance (CMR).

Methods and results

Seventy-one consecutive patients (50 males, 59 ± 16 years) with LVD (ejection fraction: 26 ± 11%) of unknown etiology underwent MDCT, LGE (late Gd-DTPA-enhanced)-CMR and CA. Patients were classified into four groups according to coronary artery disease (CAD) by CA and LGE-CMR patterns. Patients (n = 24) with CAD and transmural or sub-endocardial DE by CMR were considered having definite ischaemic LVD (group 1). Patients (n = 36) without CAD by CA and with no/atypical LGE-CMR were considered non-ischaemic LVD (group 2). Further we identified four patients with transmural DE but no CAD (group 3) and seven patients with CAD but no DE (group 4). On per-patient basis, combined coronary and DE-MDCT had excellent agreement (κ = 0.89; P < 0.001) with CA/LGE-CMR to classify patients into the same four groups. Sensitivity, specificity and accuracy of MDCT were 97, 92 and 94%, respectively for detecting patients with definite (group 1) or likely (groups 3 and 4) ischaemic LVD.

Conclusion

Combined coronary and DE-MDCT can accurately differentiate ischaemic vs. non-ischaemic etiology of LVD.