Adjusting Atrial Size Parameters for Body Surface Area: Does it Affect the Association With Pulmonary Embolism-related Adverse Events?

PURPOSE

Small left atrial (LA) volume was recently reported to be one of the best predictors of acute pulmonary embolism (PE)-related adverse events (AE). There is currently no data available regarding the impact that body surface area (BSA)-indexing of atrial measurements has on the association with PE-related adverse events. Our aim is to assess the impact of indexing atrial measurements to BSA on the association between computed tomography (CT) atrial measurements and AE.

MATERIALS AND METHODS

Retrospective study (IRB: 2015P000425). A database of hospitalized patients with acute PE diagnosed on CT pulmonary angiography (CTPA) between May 2007 and December 2014 was reviewed. Right and left atrial volume, largest axial area, and axial diameters were measured. Patients undergo both echocardiographies (from which the BSA was extracted) and CTPAs within 48 hours of the procedure. The patient's body weight was measured during each admission. LA measurements were correlated to AE (defined as the need for advanced therapy or PE-related mortality at 30 days) before and after indexing for BSA. The area under the ROC curve was calculated to determine the predictive value of the atrial measurements in predicting AE.

RESULTS

The study included 490 acute PE patients; 62 (12.7%) had AE. There was a significant association of reduced BSA-indexed and non-indexed LA volume (both <0.001), area (<0.001 and 0.001, respectively), and short-axis diameters (both <0.001), and their respective RA/LA ratios (all <0.001) with AE. The AUC values were similar for BSA-indexed and non-indexed LA volume, diameters, and area with LA volume measurements being the best predictor of adverse outcomes (BSA-indexed AUC=0.68 and non-indexed AUC=0.66), followed by non-indexed LA short-axis diameter (indexed AUC=0.65, non-indexed AUC=0.64), and LA area (indexed AUC=0.64, non-indexed AUC=0.63).

CONCLUSION

Adjusting for BSA does not substantially affect the predictive ability of atrial measurements on 30-day PE-related adverse events, and therefore, this adjustment is not necessary in clinical practice. While LA volume is the better predictor of AE, LA short-axis diameter has a similar predictive value and is more practical to perform clinically.

Transthoracic echocardiography is a simple tool for size matching in cardiac xenotransplantation

BACKGROUND

Preoperative size matching is essential for both allogeneic and xenogeneic heart transplantation. In preclinical pig-to-baboon xenotransplantation experiments, porcine donor organs are usually matched to recipients by using indirect parameters, such as age and total body weight. For clinical use of xenotransplantation, a more precise method of size measurement would be desirable to guarantee a "perfect match." Here, we investigated the use of transthoracic echocardiography (TTE) and described a new method to estimate organ size prior to xenotransplantation.

METHODS

Hearts from n = 17 genetically modified piglets were analyzed by TTE and total heart weight (THW) was measured prior to xenotransplantation into baboons between March 2018 and April 2022. Left ventricular (LV) mass was calculated according to the previously published method by Devereux et al. and a newly adapted formula. Hearts from n = 5 sibling piglets served as controls for the determination of relative LV and right ventricular (RV) mass. After explantation, THW and LV and RV mass were measured.

RESULTS

THW correlated significantly with donor age and total body weight. The strongest correlation was found between THW and LV mass calculated by TTE. Compared to necropsy data of the control piglets, the Devereux formula underestimated both absolute and relative LV mass, whereas the adapted formula yielded better results. Combining the adapted formula and the relative LV mass data, THW can be predicted with TTE.

CONCLUSIONS

We demonstrate reliable LV mass estimation by TTE for size matching prior to xenotransplantation. An adapted formula provides more accurate results of LV mass estimation than the generally used Devereux formula in the xenotransplantation setting. TTE measurement of LV mass is superior for the prediction of porcine heart sizes compared to conventional parameters such as age and total body weight.

Opportunistic Screening for Atrial Fibrillation on Routine Chest Computed Tomography

PURPOSE

Quantitative biomarkers from chest computed tomography (CT) can facilitate the incidental detection of important diseases. Atrial fibrillation (AFib) substantially increases the risk for comorbid conditions including stroke. This study investigated the relationship between AFib status and left atrial enlargement (LAE) on CT.

MATERIALS AND METHODS

A total of 500 consecutive patients who had undergone nongated chest CTs were included, and left atrium maximal axial cross-sectional area (LA-MACSA), left atrium anterior-posterior dimension (LA-AP), and vertebral body cross-sectional area (VB-Area) were measured. Height, weight, age, sex, and diagnosis of AFib were obtained from the medical record. Parametric statistical analyses and receiver operating characteristic curves were performed. Machine learning classifiers were run with clinical risk factors and LA measurements to predict patients with AFib.

RESULTS

Eighty-five patients with a diagnosis of AFib were identified. Mean LA-MACSA and LA-AP were significantly larger in patients with AFib than in patients without AFib (28.63 vs. 20.53 cm 2 , P <0.000001; 4.34 vs. 3.5 cm, P <0.000001, respectively), both with area under the curves (AUCs) of 0.73. Multivariable logistic regression analysis including age, sex, and VB-Area with LA-MACSA improved the AUC for predicting AFib (AUC=0.77). An LA-MACSA threshold of 30 cm 2 demonstrated high specificity for AFib diagnosis at 92% and sensitivity of 48%, and LA-AP threshold at 4.5 cm demonstrated 90% specificity and 42% sensitivity. A Bayesian machine learning model using age, sex, height, body surface area, and LA-MACSA predicted AFib with an AUC of 0.743.

CONCLUSIONS

LA-MACSA or LA-AP can be rapidly measured from routine chest CT, and when >30 cm 2 and >4.5 cm, respectively, are specific indicators to predict patients at increased risk for AFib.

Standardized Criteria for Identification of Cardiac Tamponade on Non-Electrocardiogram-gated Computed Tomography: Correlation With Echocardiographic Findings

PURPOSE

To identify imaging parameters that can help in the diagnosis of cardiac tamponade on non-electrocardiogram (ECG)-gated computed tomography (CT) of the chest.

MATERIALS AND METHODS

Retrospective analysis of 64 patients who had undergone CT and echocardiography for evaluation of cardiac tamponade. Of 64 patients, 34 were diagnosed with tamponade and underwent pericardiocentesis for further diagnosis and treatment. CT measurements obtained were: pericardial effusion (PeEff) pocket size in 6 locations (anterior, posterior, superior, inferior, right, and left lateral), pericardial thickening, diameters of the coronary sinus, upper superior vena cava, lower superior vena cava, and inferior vena cava. In addition, cardiac chamber sizes were measured. Subjective assessment of coronary sinus compression, pericardial enhancement, and pericardial thickening were also recorded.

RESULTS

Measurement of the sum of the right lateral and left lateral PeEff thickness resulted in 91.2% sensitivity and 86.7% specificity for cardiac tamponade with a threshold of 30 mm (receiver-operating characteristic area under the curve=0.94 [0.84 to 0.98], P <0.0001). Using the combination of inferior PeEff >16 mm, sum of right lateral and left lateral PeEff>30 mm, and presence of pericardial thickening resulted in 56% sensitivity and 100% specificity and positive predictive value for the determination of cardiac tamponade.

CONCLUSIONS

Our study suggests that CT measurements related to PeEff size and thickness aid in the diagnosis of cardiac tamponade.

Artificial intelligence can detect left ventricular dilatation on contrast-enhanced thoracic computer tomography relative to cardiac magnetic resonance imaging

OBJECTIVES

To assess the diagnostic accuracy of an automated algorithm to detect left ventricular (LV) dilatation on non-ECG gated CT, using cardiac magnetic resonance (CMR) as reference standard.

METHODS

Consecutive patients with contrast-enhanced CT thorax and CMR within 31 days (2016-2020) were analysed (n = 84). LV dilatation was defined against age-, sex- and body surface area-specific values for CMR. CTs underwent automated artificial intelligence(AI)-derived analysis that segmented ventricular chambers, presenting maximal LV diameter and volume. Area under the receiver operator curve (AUC-ROC) analysis identified CT thresholds with ≥90% sensitivity and highest specificity and ≥90% specificity with highest sensitivity. Youden's Index was used to identify thresholds with optimised sensitivity and specificity.

RESULTS

Automated diameter analysis was feasible in 92% of cases (77/84; 45 men, age 61 ± 14 years, mean CT to CMR interval 10 ± 8 days). Relative to CMR as a reference standard, 45% had LV dilatation. In males, an automated LV diameter measurement of ≥55.5 mm was ≥90% specific for CMR-defined LV dilatation (positive predictive value (PPV) 85.7%, negative predictive value (NPV) 61.2%, accuracy 68.9%). In females, an LV diameter of ≥49.7 mm was ≥90% specific for CMR-defined LV dilatation (PPV 66.7%, NPV 73.1%, accuracy 71.9%). AI CT volumetry data did not significantly improve AUC performance.

CONCLUSION

Fully automated AI-derived analysis LV dilatation on routine unselected non-gated contrast-enhanced CT thorax studies is feasible. We have defined thresholds for the detection of LV dilatation on CT relative to CMR, which could be used to routinely screen for dilated cardiomyopathy at the time of CT.

ADVANCES IN KNOWLEDGE

We show, for the first time, that a fully-automated AI-derived analysis of maximal LV chamber axial diameter on non-ECG-gated thoracic CT is feasible in unselected real-world cases and that the derived measures can predict LV dilatation relative to cardiac magnetic resonance imaging, the non-invasive reference standard for determining cardiac chamber size. We have derived sex-specific cut-off values to screen for LV dilatation on routine contrast-enhanced thoracic CT. Future work should validate these thresholds and determine if technology can alter clinical outcomes in a cost-effective manner.

Visual Ordinal Scoring of Coronary Artery Calcium on Contrast-Enhanced and Non-Contrast Chest CT: A Retrospective Study of Diagnostic Performance and Prognostic Utility

Background: Current guidelines recommend visual evaluation of coronary artery calcium (CAC) on all non-gated non-contrast chest CT examinations. However, chest CT examinations are often performed with contrast material administration. Objective: To evaluate diagnostic performance, prognostic utility, and interobserver agreement of visual CAC assessment on chest CT performed for other indications. Methods: This retrospective study included 260 patients (mean age, 60±11 years; 158 male, 102 female) who underwent both non-gated chest CT (contrast-enhanced in 116 patients; non-contrast in 144 patients) and cardiac calcium-score CT within a 12-month interval. A cardiothoracic radiologist visually assessed CAC on chest CT using an ordinal scale (absent, mild, moderate, or severe). Cardiac CT Agatston calcium scores were quantified according to established guidelines and categorized as absent (0), mild (1-99), moderate (100-299), or severe (≥300). Diagnostic performance of chest CT for presence of CAC was assessed using cardiac CT as reference standard. Major adverse cardiac events (MACE) were assessed as a composite of cardiovascular death and myocardial infarction and evaluated using Cox proportional hazards models. A second cardiothoracic radiologist performed visual CAC assessments in a random subset of 50 chest CT examinations to assess interobserver agreement. Results: For presence of any CAC on cardiac CT, contrast-enhanced and non-contrast chest CT had sensitivity of 83% [62/75] and 90% [85/95] (p=.20) and specificity of 100% [41/41] and 100% [49/49] (p=.99). CAC present on cardiac CT was misclassified as absent on 13 contrast-enhanced and 10 non-contrast chest CT examinations; Agatston score was less than 30 in all such patients, and none experienced MACE. Visual ordinal CAC score was associated with MACE for contrast-enhanced [hazard ratio (HR)=4.5 [95% CI 1.2, 16.4], p=.02) and non-contrast (HR=3.4 [95% CI 1.5, 7.8], p=.003) chest CT. Interobserver agreement was excellent for contrast-enhanced (κ =0.95) and non-contrast (κ =0.89) chest CT. Conclusions: Visual ordinal CAC assessment on both contrast-enhanced and non-contrast chest CT has high diagnostic performance, prognostic utility, and interobserver agreement. Clinical Impact: Routine reporting of CAC on all chest CT examinations regardless of clinical indication and contrast material administration could identify a large number of patients with previously unknown CAC who might benefit from preventive treatment.

Diagnostic accuracy of automated 3D volumetry of cardiac chambers by CT pulmonary angiography for identification of pulmonary hypertension due to left heart disease

OBJECTIVES

To assess diagnostic accuracy of automated 3D volumetry of cardiac chambers based on computed tomography pulmonary angiography (CTPA) for the differentiation of pulmonary hypertension due to left heart disease (group 2 PH) from non-group 2 PH compared to manual diameter measurements.

METHODS

Patients with confirmed PH undergoing right heart catheterisation and CTPA within 100 days for diagnostic workup of PH between August 2013 and February 2016 were included in this retrospective, single-centre study. Automated 3D segmentation of left atrium, left ventricle, right atrium and right ventricle (LA/LV/RA/RV) was performed by two independent and blinded radiologists using commercial software. For comparison, axial diameters were manually measured. The ability to differentiate group 2 PH from non-group 2 PH was assessed by means of logistic regression.

RESULTS

Ninety-one patients (median 67.5 years, 44 women) were included, thereof 19 patients (20.9%) classified as group 2 PH. After adjustment for age, sex and mean pulmonary arterial pressure, group 2 PH was significantly associated with larger LA volume (p < 0.001), larger LV volume (p = 0.001), lower RV/LV volume ratio (p = 0.04) and lower RV/LA volume ratio (p = 0.003). LA volume demonstrated the highest discriminatory ability to identify group 2 PH (AUC, 0.908; 95% confidence interval, 0.835-0.981) and was significantly superior to LA diameter (p = 0.009). Intraobserver and interobserver agreements were excellent for all volume measurements (intraclass correlation coefficients 0.926-0.999, all p < 0.001).

CONCLUSIONS

LA volume quantified by automated, CTPA-based 3D volumetry can differentiate group 2 PH from other PH groups with good diagnostic accuracy and yields significantly higher diagnostic accuracy than left atrial diameter.

KEY POINTS

• Automated cardiac chamber volumetry using non-gated CT pulmonary angiography can differentiate pulmonary hypertension due to left heart disease from other causes with good diagnostic accuracy. • Left atrial volume yields significantly higher diagnostic accuracy than left atrial axial diameter for identification of pulmonary hypertension due to left heart disease without time-consuming manual processing.

Utility of Automated Cardiac Chamber Volumetry by Non-Gated CT Pulmonary Angiography for Detection of Pulmonary Hypertension Using the 2018 Updated Hemodynamic Definition

BACKGROUND: Noninvasive tests for pulmonary hypertension (PH) are needed to help select patients for diagnostic right heart catheterization (RHC). CT pulmonary angiography (CTPA) is commonly performed for suspected PH. OBJECTIVE: To assess the utility of CTPA-based cardiac chamber volumetric measurements for diagnosis of PH in comparison with echocardiographic and conventional CTPA parameters, using as reference the 2018 updated hemodynamic definition. METHODS: This retrospective study included 109 patients (median age, 68 years; 72 women, 37 men) who underwent non-gated CTPA, echocardiography, and RHC for workup of suspected PH between August 2013 and February 2016. Two radiologists independently used automated 3D segmentation software to determine volumes of the right ventricle (RV), right atrium (RA), left ventricle (LV), and left atrium (LA), and measured axial diameters of cardiac chambers, main pulmonary artery, and ascending aorta. Interobserver agreement was assessed, and mean values were obtained; one observer repeated volumetric measurements to assess intraobserver agreement. ROC analysis was used to assess diagnostic performance for detection of PH. A multivariable binary logistic regression model was established. RESULTS: A total of 60/109 patients had PH. Intra- and interobserver agreement were excellent for all volume measurements (intraclass correlation coefficients, 0.935-0.999). In patients with, versus without, PH, RV volume was 172.6 versus 118.1 ml, and RA volume was 130.2 versus 77.0 ml (both p<.05). Cardiac chamber measurements with highest AUC for PH were RV/LV volume ratio and RA volume (both 0.791). Significant predictors of PH after adjustment for age, sex, and body surface area included RV volume per 10 ml [odds ratio (OR)=1.21], RA volume per 10 ml (OR=1.27), RV/LV volume ratio (OR=2.91), and RA/LA volume ratio (OR=11.22). Regression analysis yielded a predictive model for PH containing two independent predictors, echocardiographic pulmonary arterial systolic pressure and CTPA-based RA volume; the model had AUC 0.898, sensitivity 83.3%, and specificity 85.7%. CONCLUSION: Automated cardiac chamber volumetry using non-gated CTPA, particularly of the RA, provides incremental utility relative to echocardiographic and conventional CTPA parameters for diagnosis of PH. CLINICAL IMPACT: Automated cardiac chamber volumetry on CTPA may facilitate early nonvinvasive detection of PH, identifying patients warranting further evaluation by RHC.

Diagnostic performance of chest radiography measurements for the assessment of cardiac chamber enlargement

Background:

The cardiothoracic ratio (CTR) is commonly assessed on chest radiography for detection of cardiac chamber enlargement, but the traditional cutpoint of 0.5 has low specificity. We sought to evaluate the diagnostic accuracy of new measurement techniques for the detection of cardiac enlargement on chest radiographs.

Methods:

We obtained retrospective cross-sectional data on consecutive patients who underwent both chest radiography and cardiac magnetic resonance imaging (MRI) within a 14-day interval between 2006 and 2016 at a large academic hospital network. We established the presence of cardiac chamber enlargement using cardiac MRI as the reference standard. We evaluated the diagnostic performance of different techniques for measuring heart size and CTR on frontal chest radiographs.

Results:

Of 152 patients included, 81 (53%) were men and the mean age was 52 years. Maximum heart diameter had the highest area under the receiver operating characteristic curve for detection of cardiac enlargement (0.827, 95% confidence interval 0.760–0.894). In the subgroup of posteroanterior chest radiography studies (n = 101), a CTR cutpoint of 0.50 had only moderate sensitivity (72%) and specificity (72%). In men, a maximum heart diameter cutpoint of 15 cm had a sensitivity of 86% and a negative likelihood ratio of 0.24, and a cutpoint of 19 cm had a specificity of 100% and a positive likelihood ratio of infinity. In women, a maximum heart diameter cutpoint of 13 cm had a sensitivity of 91% and a negative likelihood ratio of 0.15, and a cutpoint of 17 cm had a specificity of 91% and a positive likelihood ratio of 3.5.

Interpretation:

A traditional CTR cutpoint of 0.5 has limited diagnostic value. Simple heart diameter measurements have higher diagnostic performance measures than CTR.

Improving CT assessment for pulmonary hypertension in patients with severe aortic stenosis, correlation with right heart catheterization

PURPOSE

To identify CT parameters useful for assessment of pulmonary hypertension (PH) in patients with severe aortic stenosis (AS).

MATERIALS AND METHODS

Retrospective study of 165 patients who had undergone right heart catheterization (RHC), and CTA of the thorax for preoperative aortic valve replacement (TAVR) planning. These were divided into groups based on mean pulmonary artery (PA) pressure (mPAP) of 25 mm Hg on RHC (85 cases and 80 controls). Diameters of main pulmonary artery diameter (MPAD), left pulmonary artery (LPA), right pulmonary artery (RPA), and maximal long axis and short axis diameters of the right atrium (RA) and ventricle (RV) were measured on the axial plane. Univariate and multivariate statistical analysis was utilized to identify metrics predictive of PH.

RESULTS

MPAD, LPA, and RPA were higher in subjects with mPAP >25 mm Hg (p < 0.0001 for all). Thresholds of 30.5 mm for MPAD (68.4% sensitivity, 82.7% specificity), and 27.5 mm for LPA and RPA (LPA: 51.9% sensitivity, 78.8% specificity; RPA: 62.0% sensitivity, 78.8% specificity) provided the best discrimination of elevated mPAP. Compared to literature values for MPAD (28.9 mm in men and 26.9 mm in women), these thresholds provide lower sensitivity but greatly increased specificity. Inclusion of RA enlargement to MPAD increased specificity to 98.5%, while inclusion of RV enlargement increased specificity to 100%.

CONCLUSION

Threshold to identify PH in patients with AS using PA enlargement is higher than previously reported range for normal. Inclusion of RA and RV enlargement improves the ability of CT to more accurately identify PH in patients with AS.

Accuracy of Non-Electrocardiographically Gated Thoracic CT Angiography for Right Atrial and Right Ventricular Enlargement

PURPOSE

To assess the role of long-axis (LA) and short-axis (SA) measurements of the right atrium (RA) and right ventricle (RV) at non-electrocardiographically (ECG) gated thoracic CT angiography for identification of RA enlargement and RV enlargement.

MATERIALS AND METHODS

This study was a retrospective case review of 138 patients who underwent both non-ECG-gated CT angiography and ECG-gated CT angiography concurrently from November 2016 through November 2018. The SA and LA of the RA and RV were measured by two observers blinded to the ECG-gated CT angiography data. ECG-gated CT angiography-derived RA end-systolic and RV end-diastolic volumes were used as standard of reference to derive cutoff values for diagnosis of RA and RV enlargement.

RESULTS

In this study, 138 patients were evaluated (70 men, 68 women; mean age, 70.0 years ± 18.4 [standard deviation]; mean body mass index, 29.3 kg/m² ± 8.1). Of these patients, ECG-gated CT angiography revealed 36.2% had RA enhancement and 19.0% had RV enhancement. The best predictor of RA enhancement was the product of atrial LA and SA measurements, for which a threshold value of 3210 mm² yielded a 94% sensitivity and 81.8% specificity (area under the curve [AUC], 0.92). A threshold of 55.5 mm for LA diameter had 86% sensitivity and 78.4% specificity in identifying RA enlargement. RV enlargement could be predicted if the SA diameter was greater than 48.5 mm (76.9% sensitivity and 64.9% specificity) and with a body surface area indexed value of 27.0 mm/m² (92.3% sensitivity and 74.8% specificity [AUC, 0.87]).

CONCLUSION

RA and RV enlargement can be accurately diagnosed by using non-ECG-gated CT angiography.© RSNA, 2019Supplemental material is available for this article.

Going beyond Cardiomegaly: Evaluation of Cardiac Chamber Enlargement at Non-Electrocardiographically Gated Multidetector CT: Current Techniques, Limitations, and Clinical Implications

Cardiac chamber enlargement is important in the prediction of morbidity and mortality for a multitude of cardiovascular processes. Although non-electrocardiographically (ECG) gated multidetector CT is a commonly used cross-sectional imaging modality to evaluate a litany of cardiothoracic processes, a standardized method for evaluating and reporting cardiac chamber size does not exist. This has led to heterogeneity in the reporting of cardiac enlargement at routine multidetector CT with most readers often using gestalt assessment and the term cardiomegaly, which does not implicate the chamber or chambers that are enlarged. The purpose of this review article is to highlight advantages and limitations of several techniques used to assess cardiac chamber size at non-ECG-gated multidetector CT and to provide readers with reproducible and rapid measurements to determine if cardiac chamber size is present. The long-term aim would be to promote discussions between radiologists and institutions that would result in improved accuracy and decreased variability when commenting on cardiac chamber size. © RSNA, 2019.

Cardiovascular findings on cross-sectional imaging: spectrum of incidental and critical findings and clinical relevance for the abdominal radiologist

Although not the primary focus of the exams, cardiovascular structures are included to some extent on all abdominal or whole-body cross-sectional studies. Cardiovascular findings often present incidentally and may range from chronic to acute and emergent pathologies. Among the most common cardiovascular findings are the presence of cardiac calcifications, most commonly coronary, which correlate with the presence of coronary artery and valvular disease. Signs of myocardial ischemia, both acute and chronic, and its complications may also be visualized. Cardiac filling defects most commonly represent thrombus and are associated with systemic arterial embolic complications. Pericardial findings often manifest as effusion or thickening, which may lead to hemodynamic consequences visible at imaging. Incidental pulmonary emboli and systemic venous thrombi may be incidentally detected, particularly in hospitalized and oncologic patients, and warrant immediate attention. This review will highlight the appearance of common and important incidental cardiovascular findings and related pitfalls and discuss reporting and follow-up recommendations relevant to the abdominal radiologist.