Volume and dimensions of angiographically normal coronary arteries assessed by multidetector computed tomography

Cardiac computed tomography-derived coronary artery volume to myocardial mass in patients with severe coronary artery disease

BACKGROUND

Coronary artery lumen volume (V) to myocardial mass (M) ratio (V/M) can show the mismatch between epicardial coronary arteries and the underlying myocardium.

METHODS

The V, M and V/M were obtained from the coronary computed tomography angiography (CCTA) of patients in the FAST-TRACK CABG study, the first-in-human trial of coronary artery bypass grafting (CABG) guided solely by CCTA and fractional flow reserve derived from CCTA (FFRCT) in patients with complex coronary artery disease (CAD). The correlations between V/M ratios and baseline characteristics were determined and compared with those from the ADVANCE registry, an unselected cohort of historical controls with chronic CAD.

RESULTS

The V/M ratio was obtained in 106 of the 114 pre-CABG CCTAs. Mean age was 65.6 years and 87% of them were male. The anatomical SYNTAX score from CCTA was significantly higher than the functional SYNTAX score derived using FFRCT [43.1 (15.2) vs 41.1 (16.5), p ​< ​0.001]. Mean V, M, and V/M were 2204 ​mm3, 137 ​g, and 16.5 ​mm3/g, respectively. There were weak negative correlations between V and anatomical and functional SYNTAX scores (Pearson's r ​= ​-0.26 and -0.34). V and V/M had a strong correlation (r ​= ​0.82). The V/M ratio in the current study was significantly lower than that in the ADVANCE registry (median 16.1 vs. 24.8 [1st quartile 20.1]).

CONCLUSION

Systematically smaller V/M ratios were found in this population with severe CAD requiring CABG compared to an unselected cohort with chronic CAD. The V/M ratio could provide additional non-invasive assessment of CAD especially when combined with FFRCT.

The Role of CCTA-derived Cardiac Structure and Function Analysis in the Prediction of Readmission in Nonischemic Heart Failure

Cardiac function and structure significantly impact nonischemic heart failure (HF) patient outcomes. This study investigated 236 patients (107 nonischemic heart failure, 129 healthy) to assess the relationship between coronary computed tomography angiography (CCTA)-derived parameters and clinical outcomes. Among the nonischemic heart failure patients, 37.3% experienced readmissions. In this group, specific CCTA measurements were identified as significant predictors of readmission: epicardial adipose tissue (CTEAT) at 54.49 cm3 (HR: 1.05; 95% CI: 1.03-1.07; P < 0.001), cardiac muscle mass to lumen volume (CTV/M) at 20% (HR: 0.59; 95% CI: 0.48-0.72; P < 0.001), peri-coronary adipose (CTPCAT) at -64.68 HU (HR: 1.1; 95% CI: 1.03-1.16; P = 0.002) for the right coronary artery, -81.07 HU (HR: 1.3; 95% CI: 1.1-1.53; P = 0.002) for the left anterior descending artery, and -73.42 HU (HR: 1.33; 95% CI: 1.18-1.51; P < 0.001) for the circumflex branch of the left coronary artery. In patients with nonischemic heart failure, increased CTEAT, CTPCAT, and CTV/M independently predicted rehospitalization.

Pill or pump? Nitroglycerin 0.5 mg tablet vs 0.8 mg spray: Effect on proximal vessel diameters at Coronary CT Angiography (CCTA)

INTRODUCTION

The administration of sublingual Nitroglycerin (NTG) prior to CT coronary angiography (CCTA) can be perfomed using pump spray or tablets. Choice of method seems to be based on local preference, rather than published guidelines. This retrospective analysis tested whether proximal coronary diameters differed dependent on the sublingual administration of 0.5 mg Nitroglycerin (NTG) tablets or 0.8 mg NTG spray.

METHODS

287 ECG-gated CCTA studies with optimal image quality and Agatston scores<400 were included in this retrospective analysis. 143 of the patients were dosed with NTG tablets at a dose of 0.5 mg prior to CCTA. 144 patients received 2 puffs of 0.4 mg NTG spray for a total dose of 8 mg. All were scanned on a second-generation Dual Source CT. Diameters of proximal segments of Left Main (LM), Right (RCA), Left Anterior (LAD) and circumflex (CX) coronary arteries were measured using semi-automatic electronic callipers by two blinded readers. Results were summarised as the mean of maximum and minimum diameters. Sex-specific analysis of diameters was carried out using repeated-measures ANOVA for each vessel. Agreement between readers was examined with Bland-Altman analysis and intra-class-correlation coefficient (ICC).

RESULTS

No significant differences in coronary diameters were found except in the RCA for women and LM for men. In both cases, diameters were smaller in the spray group (11 and 9%, respectively). Reader agreement was excellent, with ICC>0.96 for all vessels, and no significant bias, except in CX (0.03 mm).

CONCLUSIONS

We found no evidence for the systematic superiority of either administration method in proximal coronary vessels.

IMPLICATIONS FOR PRACTICE

Choosing between tablet or spray NTG prior to CCTA can be guided by practical, economical and hygienic considerations alone.

Advances in Coronary Computed Tomographic Angiographic Imaging of Atherosclerosis for Risk Stratification and Preventive Care

The diagnostic evaluation of coronary artery disease is undergoing a dramatic transformation with a new focus on atherosclerotic plaque. This review details the evidence needed for effective risk stratification and targeted preventive care based on recent advances in automated measurement of atherosclerosis from coronary computed tomography angiography (CTA). To date, research findings support that automated stenosis measurement is reasonably accurate, but evidence on variability by location, artery size, or image quality is unknown. The evidence for quantification of atherosclerotic plaque is unfolding, with strong concordance reported between coronary CTA and intravascular ultrasound measurement of total plaque volume (r >0.90). Statistical variance is higher for smaller plaque volumes. Limited data are available on how technical or patient-specific factors result in measurement variability by compositional subgroups. Coronary artery dimensions vary by age, sex, heart size, coronary dominance, and race and ethnicity. Accordingly, quantification programs excluding smaller arteries affect accuracy for women, patients with diabetes, and other patient subsets. Evidence is unfolding that quantification of atherosclerotic plaque is useful to enhance risk prediction, yet more evidence is required to define high-risk patients across varied populations and to determine whether such information is incremental to risk factors or currently used coronary computed tomography techniques (eg, coronary artery calcium scoring or visual assessment of plaque burden or stenosis). In summary, there is promise for the utility of coronary CTA quantification of atherosclerosis, especially if it can lead to targeted and more intensive cardiovascular prevention, notably for those patients with nonobstructive coronary artery disease and high-risk plaque features. The new quantification techniques available to imagers must not only provide sufficient added value to improve patient care, but also add minimal and reasonable cost to alleviate the financial burden on our patients and the health care system.

Cardiac computed tomography-derived coronary artery volume to myocardial mass

In the absence of disease impacting the coronary arteries or myocardium, there exists a linear relationship between vessel volume and myocardial mass to ensure balanced distribution of blood supply. This balance may be disturbed in diseases of either the coronary artery tree, the myocardium, or both. However, in contemporary evaluation the coronary artery anatomy and myocardium are assessed separately. Recently the coronary lumen volume to myocardial mass ratio (V/M), measured noninvasively using coronary computed tomography angiography (CTCA), has emerged as an integrated measure of myocardial blood supply and demand in vivo. This has the potential to yield new insights into diseases where this balance is altered, thus impacting clinical diagnoses and management. In this review, we outline the scientific methodology underpinning CTCA-derived measurement of V/M. We describe recent studies describing alterations in V/M across a range of cardiovascular conditions, including coronary artery disease, cardiomyopathies and coronary microvascular dysfunction. Lastly, we highlight areas of unmet research need and future directions, where V/M may further enhance our understanding of the pathophysiology of cardiovascular disease.

Evaluation of a no-reference image quality metric for projection X-ray imaging using a 3D printed patient-specific phantom

PURPOSE

Feasability of a no-reference image quality metric was assessed on patient-like images using a patient-specific phantom simulating a frame of a coronary angiogram.

METHODS

One background and one contrast-filled frame of a coronary angiogram, acquired using a clinical imaging protocol, were selected from a Philips Integris Allura FD (Philips Healthcare, Best, The Netherlands). The background frame's pixels were extruded to a thickness proportional to their grey value. One phantom was 3D printed using composite 80% bronze filament (max. thickness of 5.1 mm), the other was a custom PMMA cast (max thickness of 8.5 cm). A vessel mold was created from the contrast-filled frame and injected with a solution of 320 mg I/ml contrast fluid (75%), water and gelatin. Still X-ray frames of the vessel mold + background phantom + 16 cm PMMA were acquired at manually selected different exposure settings using a Philips Azurion (Philips Healthcare, Best, The Netherlands) in User Quality Control Mode and were exported as RAW images. The signal-difference-to-noise-ratio-squared (SDNR²) and a spatial-domain-equivalent of the noise equivalent quanta (NEQ_SDE) were calculated. The Spearman's correlation of the latter parameters with a no-reference perceptual image quality metric (NIQE) was investigated.

RESULTS

The bronze phantom showed better resemblance to the original patient frame selected from a coronary angiogram of an actual patient, with better contrast and less blur than the PMMA phantom. Both phantoms were imaged using a comparable imaging protocol to the one used to acquire the original frame. The bronze phantom was hence used together with the vessel mold for image quality measurements on the 165 still phantom frames. A strong correlation was noted between NEQ_SDE and NIQE (SROCC = -0.99, p < 0.0005) and between SDNR² and NIQE (SROCC = -0.97, p < 0.0005).

CONCLUSION

Using a cost-effective and easy to realize patient-specific phantom we were able to generate patient-like X-ray frames. NIQE as a no-reference image quality model has the potential to predict physical image quality from patient images.

Questionable necessity of nitroglycerin for diagnostic coronary artery examination using 320-row multi-detector computed tomography

OBJECTIVE

This study aims to analyze and compare the diagnostic effectiveness of 320-row multi-detector computed tomography for coronary artery angiography (MDCTA) in subjects with and without sublingual vasodilator (nitroglycerin).

MATERIALS AND METHODS

From September 2015 to September 2016, 70 individuals without history of major cardiovascular diseases who underwent MDCTA for health examination were retrospectively categorized into sublingual nitroglycerin (NTG) and non-NTG groups. Medical history, CT dose index (CTDI), and multi-slice CT images were compared between two groups. A diameter of coronary artery (DA, mm) was computed and analyzed.

RESULTS

A total of 41 males and 29 females (mean age: 55.43±8.84 years, range: 34- 76) were reviewed. Normal and abnormal MDCTA findings were noted in 54 and 16 participants, respectively, with the detection rate of coronary artery disease being 23%. There was no significant difference in inter-observer variability of coronary CTA image quality and diagnosis between the NTG and non-NTG groups among three experienced radiologists. Although the percentage dilatation of left anterior descending branch (LAD), right coronary artery (RCA) and left circumflex branch (LCX) following in the NTG group were 12.4%, 12.8% and 25.3%, respectively (p < 0.01), there was no significant difference in image quality and diagnosis between the two groups.

CONCLUSIONS

Despite the recommendation of routine nitroglycerin use for subjects undergoing computed tomography for coronary artery angiography, our results showed no significant advantage of its use in improving image quality and rate of diagnosis accuracy.

Subtraction CT angiography improves evaluation of significant coronary artery disease in patients with severe calcifications or stents-the C-Sub 320 multicenter trial

OBJECTIVES

Diagnostic accuracy of conventional coronary CT angiography (CCTA_conv) may be compromised by blooming artifacts from calcifications or stents. Blooming artifacts may be reduced by subtraction coronary CT angiography (CCTA_sub) in which non-contrast and contrast CT data sets are subtracted digitally. We tested whether CCTA_sub in patients with severe coronary calcification or stents reduces the number of false-positive stenosis evaluations compared with CCTA_conv.

METHODS

In this study, 180 symptomatic patients scheduled for invasive coronary angiography (ICA) were prospectively enrolled and CT scanned (2013-2016) at three international centers. CCTA_conv, and CCTA_sub data sets were reconstructed. Target segments were defined as motion-free coronary segments with a suspected stenosis (> 50% of lumen) potentially due to blooming of either calcium or stents. Target segments were evaluated with respect to misregistration artifacts from the CCTA_sub reconstruction process, in which case evaluation was omitted. CCTA_sub and CCTA_conv were compared with ICA. Primary outcome measure was the frequency of false positives by CCTA_conv versus CCTA_sub to identify > 50% coronary stenosis by ICA on a per-segment level.

RESULTS

After exclusion of 76 patients, 104 (14% females) with mean age 67 years and median Agatston score 852 were included. There were 136 target segments with misregistration and 121 target segments without. Accuracy calculations in target segments without misregistration showed a reduction of the false positives from 72% [95% confidence interval (CI): 63-80%] in CCTA_conv to 33% (CI:25-42%) in CCTA_sub, at the expense of 7% (CI:3-14%) false negatives in CCTA_sub.

CONCLUSIONS

In severely calcified coronary arteries or stents, CCTA_sub reduces the false-positive rate in well-aligned, calcified or stent segments suspected of significant stenosis on CCTA_conv. Nevertheless, misregistration artifacts are frequent in CCTA_sub.

KEY POINTS

• A high calcium-score reduces the diagnostic accuracy in patients scanned with cardiac CT. • These patients would normally need an invasive angiogram for diagnosis. • In this prospective, multicenter study, subtraction CT, when evaluable, reduces false-positive stenosis evaluations. • Subtraction coronary CT angiography may, when evaluable, reduce excessive downstream testing.

Measurements of Lumen Areas and Diameters of Proximal and Middle Coronary Artery Segments in Subjects Without Coronary Atherosclerosis

There are plenty of data on morphology and lumen dimensions of diseased coronary arteries. However, information on normal coronary vessel anatomy is scarce. We provided computed tomography angiography-derived reference values of lumen dimensions in proximal and middle coronary segments in a healthy population with respect to gender and vessel dominance. Consecutive 2,849 computed tomography angiography examinations were reviewed to identify 201 subjects (77 men, patient age 50 ± 13 years) whose coronary arteries were free from any sign of atherosclerosis (calcium score 0, no detectable plaque). For all proximal and middle coronary segments, lumen areas (LAs) and lumen diameters were measured. Coronary vessel segmentation and dominance pattern were defined using the Syntax Score. Normal values of LAs and lumen diameters were significantly smaller for women compared with men except for the proximal right coronary artery and the left main coronary artery (LMCA) (20.2 ± 6.6 mm² vs 23.0 ± 6.1 mm², p = 0.0003, and 5.0 ± 0.8 mm vs 5.4 ± 0.7 mm, p = 0.0001). The lower limit of normal for the LMCA (defined as mean LA - 2 standard deviations) equaled 7.0 and 10.8 mm² for women and men, respectively. Subjects with left (vs right) coronary dominance had significantly larger areas and diameters of the LMCA (26.2 ± 9.2 mm² vs 20.7 ± 6.0 mm², p = 0.0017, and 5.7 ± 1.0 mm vs 5.1 ± 0.7 mm, p = 0.0017, respectively) and proximal left circumflex (13.8 ± 2.7 mm² vs 10.4 ± 3.8 mm², p = 0.0001, and 4.2 ± 0.4 mm vs 3.6 ± 0.7 mm, p = 0.0001, respectively) and smaller areas and diameters of the proximal right coronary artery (7.1 ± 2.0 mm² vs 13.3 ± 3.6 mm², p <0.0001, and 3.0 ± 0.4 mm vs 4.1 ± 0.6 mm, p <0.0001, respectively). In conclusion, gender and coronary artery dominance pattern significantly impact normal LAs and dimensions in subjects without coronary atherosclerosis.