Diagnostic accuracy of cardiac computed tomography angiography for myocardial infarction

A Pilot Study of Third-Generation Dual-Source Computed Tomography for the Assessment of Global Dynamic Changes in Left Ventricular Structure and Function in a Porcine Model of Acute Myocardial Infarction

Background

First-generation and second-generation dual-source computed tomography (DSCT) are useful for analyzing left ventricle (LV) structure and function. This pilot study aimed to investigate the feasibility and role of third-generation DSCT for the evaluation of dynamic changes in LV structural and functional characteristics in a Diannan small-ear pig model of acute myocardial infarction (AMI).

Material/Methods

The model of AMI was established by balloon occlusion of the distal third of the left anterior descending (LAD) coronary artery in 14 Diannan small-eared pigs. Third-generation DSCT was performed to observe dynamic changes in LV structure and function before and after AMI was induced, with a follow-up period of 30 days.

Results

The mean structural measurements at baseline included interventricular septum thickness (8.50±0.90 mm), LV anterior wall thickness (8.40±1.30 mm), LV posterior wall thickness (7.80±1.20 mm), LV end-diastolic dimension (LVEDD) (45.00±4.90 mm), and LV end-systolic dimension (LVESD) (25.90±4.10 mm). The mean functional measurements at baseline included the LV end-diastolic volume (LVEDV) (74.62±13.54 ml), LV end-systolic volume (LVESV) (23.06±7.46 ml), LV ejection fraction (LVEF) (69.29±6.83%), LV mass (86.35±14.02 g), stroke volume (SV) (51.56±9.77 ml), and cardiac output (CO) (4.22±2.14 l/min). Trends of time-dependent changes were observed for LVESV, LVEF, SV, and CO, but not for LVEDV or LV mass.

Conclusions

Third-generation DSCT was validated as a tool for assessing dynamic changes in LV global function in a porcine model of AMI.

Automatic high-resolution infarct detection using volumetric multiphase dual-energy CT

OBJECTIVES

Late contrast enhancement CT (LCE-CT) visualizes the presence of myocardial infarcts. Differentiation of the contrast-enhanced infarct from blood pool is challenging. We developed a novel method using data from first pass CT angiography (CTA) imaging to enable automatic infarct detection.

MATERIALS AND METHODS

A canine model of myocardial infarction was produced in 11 animals. Two months later, first pass CTA (90 kVp) and LCE-CT (dual energy 90 kVp/150 kVp tin filtered) were performed. Late gadolinium enhancement MRI was used as reference standard. The CTA and LCE-CT were co-registered using a fully automatic non-rigid method based on curved B-splines. The method allowed for limited elastic deformation and the considerable differences in attenuation between first-pass and delayed image. The blood pool was easily identified on the CTA image by high attenuation. Because CTA and LCE-CT were registered, the blood pool segmentation can be directly transferred to the LCE-CT - thereby solving the key problem of infarct/blood pool differentiation. The remaining segmentation of infarcted vs. noninfarcted myocardium was performed using a threshold. Automatic and MRI-guided expert segmentations of LCE-CT infarcts were compared to each other on volume and area basis (intraclass correlation coefficient, ICC) and on voxel basis (dice similarity coefficient, DSC between automatic and expert CT segmentation). CT infarct volumes were compared with the reference standard MRI.

RESULTS

The infarcts were mainly subendocardial (81%) and relatively small (median MRI infarct mass 7.4 g). The automatic segmentation showed excellent agreement with expert segmentation on volume and area measurements (ICC = 0.96 and 0.87, respectively). DSC showed moderately good agreement (DSC = 0.47). Compared to MRI there was modest agreement (ICC = 0.62) and excellent correlation (R = 0.9). Manual interaction was less than 1 min per exam.

CONCLUSION

We propose an automatic method for infarct segmentation on LCE-CT using multiphase CT information, which showed excellent agreement with expert readers and favorable correlation with MRI.

Factors related to the use of reperfusion strategies in elderly patients with acute myocardial infarction

Background

About eighty percent of acute myocardial infarction (AMI) cases occur in the elderly, we aim to examine the use of reperfusion strategies in elderly patients (≥65 years) with AMI and to investigate the factors affecting the use of these strategies.

Methods

A total of 352 consecutive elderly patients (≥65 years) with ST-elevated AMI (STAMI) were admitted, they were divided into 2 groups based on reperfusion treatment (thrombolysis or percutaneous coronary intervention, PCI): reperfusion therapy group (n = 268) and non-reperfusion therapy group (n = 84). Demographic and medical data were collected for comparison. Odds ratios (OR) and 95% confidence interval (C.I.) were calculated directly from the estimated regression coefficients.

Results

About 76.1% of the elderly patients with AMI received reperfusion treatment (62.5% received PCI, and 13.6% received thrombolysis). Stepwise Logistic regression analysis revealed that a patient age ≥75 years (95% CI: 0.194 ~ 0.590, OR = 0.338, P = 0.000) and medical history of angina (95% CI: 0.281 ~ 0.928, OR = 0.501, P = 0.014) were determining factors for receiving less reperfusion therapy. Complications including right ventricular myocardial infarction (MI) (95% CI: 1.618 ~ 12.907, OR = 4.472, P = 0.003), unbearable symptoms (95% CI: 1.132 ~ 3.928, OR = 1.839, P = 0.021) and medical insurance (95% CI: 1.313 ~ 4.524, OR = 2.429, P = 0.004) were independent predictors of reperfusion therapy. The reperfusion therapy subset analysis revealed that intracranial hemorrhage (2.7% vs. 8.3%, P = 0.000), left ventricular ejection fraction (LVEF) <45% (13.2% vs. 29.2%, P = 0.019) and mortality rate within 1 year (2.7% vs. 6.3%, P = 0.045) were significantly decreased in the PCI group as compared with thrombolysis.

Conclusion

Elderly patients with a medical history of angina, right ventricular MI, unbearable symptoms and medical insurance are likely be recipients of reperfusion strategies.

Role of CT angiography for detection of coronary atherosclerosis

As laparoscopic surgery is replacing open surgery, similarly computed tomography angiography is replacing invasive conventional cardiac angiography. In the last century, marvelous efforts in research have improved strategies for cure, diagnosis and prevention of fatal human diseases; however, coronary artery disease, as the most prevalent cause of mortality and morbidity in the world, has remained a great challenge. Due to advancements in technology and research, it has become more simple and robust to diagnose and treat coronary artery disease (CAD) with minimal or no intervention, promising to not only diagnosis at an early stage but potential prevention altogether. While most with obvious CAD can be diagnosed easily and quickly with ECG, those identified as 'low risk' require more extensive testing to diagnose or rule out CAD. For example in emergency departments, low-risk patients with chest pain are diagnosed solely depending on history, ECG and blood testing for biomarkers. This approach has resulted in either delayed or miss-diagnosis of Acute coronary syndrome. To prevent this, many emergency departments now use protocols for low-risk heart patients that include cardiac stress tests and/or CT heart imaging. This review provides an overview of the current literature on the value of Computed tomography angiography and discusses how prognostic information obtained with Computed tomography angiography can be used to further integrate the technique into clinical practice.