A new method of CT for the cardiac measurement: correlation of computed tomography measured cardiac parameters and pulmonary obstruction index to assess cardiac morphological changes in acute pulmonary embolism patients

Left Atrial Phasic Function Impairment in Subacute and Chronic Pulmonary Embolism Patients With Different Degrees of Obstruction: An MRI Feature Tracking Study

BACKGROUND

The alteration of left atrial (LA) phasic function in subacute and chronic pulmonary embolism (PE) patients is unclear.

PURPOSE

To investigate LA phasic strain and LA-right ventricular (RV) interaction in subacute and chronic PE patients with different degrees of obstruction by MRI-feature tracking (MRI-FT).

STUDY TYPE

Retrospective.

POPULATION

One hundred three PE patients (54 subacute [2 weeks to 3 months after initial symptoms], 49 chronic [>3 months after initial symptoms]) and 80 controls.

FIELD STRENGTH/SEQUENCE

3.0 T/balanced steady state free precession sequence.

ASSESSMENT

Patients were divided into mild (pulmonary artery obstruction index [PAOI] < 30%, N = 57), moderate (30% ≤ PAOI < 50%, N = 27), and severe (50% ≥ PAOI, N = 19) PE subgroups. LA reservoir, conduit, and active pump longitudinal strains (εs, εe, and εa) and strain rates (SRs, SRe, and SRa) and biventricular global strains were measured. Determinants of LA strains were investigated.

STATISTICAL TESTS

ANOVA, t-tests, Mann-Whitney U tests, linear regression. P < 0.05 was considered statistically significant.

RESULTS

For both subacute and chronic PE patients, LA reservoir, conduit, and active pump strains and strain rates were significantly lower than in controls. However, there were no significant differences in LA strains between patients with subacute and chronic PE (P = 0.933, 0.625, and 0.630 for εs, εe, and εa). The severe PE subgroup had significantly higher εa and SRa than the mild and moderate PE subgroups. LA strains were significantly correlated with RV diameter and biventricular strains, and RV diameter (β = -6.836, -4.084, and -1.899 for εs, εe, and εa) was independently associated with LA strains after adjustment for other factors (R2 = 0.627, 0.536, and 0.437 for εs, εe, and εa).

DATA CONCLUSION

LA phasic function evaluated by MRI-FT was significantly impaired in subacute and chronic PE patients, and LA active pump function in the severe PE subgroup was higher than that in the mild and moderate PE subgroups. The independent association between RV diameter and LA strains demonstrates that RV diameter may be an important indicator for monitoring LA dysfunction in PE patients.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 3.

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.

Biatrial Volumetric Assessment by Non-ECG-Gated CT Pulmonary Angiography Correlated with Transthoracic Echocardiography in Patients with Normal Diastology

Atrial size is a predictor of cardiovascular mortality. Non-ECG-gated computed tomography pulmonary angiography (CTPA) is a common test for cardiopulmonary evaluation but normative values for biatrial volumes are lacking. We derived normal CT biatrial volumes using manual and semiautomated segmentation with contemporaneous transthoracic echocardiography (TTE) to confirm normal diastology. Thirty-five consecutive cases in sinus rhythm with no history of cardio-vascular, renal, or pulmonary disease and normal diastolic function were selected. Planimetric CTPA measurements were compared to TTE volumes measured using area length method. TTE and CTPA derived normal LAVi and RAVi were 27 + 5 and 20 + 6 mL/m², and 30 + 8 and 29 + 9 mL/m², respectively. Bland-Altman analysis revealed an underestimation of biatrial volumes by TTE. TTE-CT mean biases for LAV and RAV were -5.7 + 12.0 mL and -16.2 + 14.8 mL, respectively. The CT intraclass correlation coefficients (ICC 95% CI) for LA and RA volumes were 0.99 (0.96-1.00) and 0.96 (0.76-0.99), respectively. There was excellent correlation (p &lt; 0.001) between the semiautomated and manual measurements for LA (r 0.99, 95% CI 0.98-0.99) and RA (r 0.99, 95% CI 0.99-1.00). Atrial volumetric assessment on CTPA is easy and reproducible and can provide additional metric in cardiopulmonary assessment.

Evidence for Left Atrial Volume Being an Indicator of Adverse Events in Patients With Acute Pulmonary Embolism: Retrospective Case-control Pilot Study

PURPOSE

To assess the association between computed tomography pulmonary angiography (CTPA) atrial measurements and both 30-day pulmonary embolism (PE)-related adverse events and mortality, and non-PE-related mortality, and to identify the best predictors of these outcomes by comparing atrial measurements and widely used clinical and imaging variables.

PATIENTS AND METHODS

Retrospective single-center pilot study. Acute PE patients diagnosed on CTPA who also had a transthoracic echocardiogram, electrocardiogram, and troponin T were included. CTPA left atrial (LA) and right atrial (RA) volume and short-axis diameter were measured and compared between outcome groups, along with right ventricular/left ventricular diameter ratio, interventricular septal bowing, tricuspid annular plane systolic excursion, electrocardiogram, and troponin T.

RESULTS

A total of 350 patients. LA volume and diameter were associated with PE-related adverse events (P≤0.01). LA volume was the only atrial measurement associated with PE-related mortality (P=0.03), with no atrial measurements associated with non-PE-related mortality. Troponin was most associated with PE-related adverse events and mortality (both area under the curve [AUC]=0.77). On multivariate analysis, combination models did not greatly improve PE-related adverse events prediction compared with troponin alone. For PE-related mortality, the best models were the combination of troponin, age, and either LA volume (AUC=0.86) or diameter (AUC=0.87).

CONCLUSION

Among patients with acute PE, CTPA LA volume is the only imaging parameter associated with PE-related mortality and is the best imaging predictor of this outcome. Reduced CTPA LA volume and diameter, along with increased RA/LA volume and diameter ratios, are significantly associated with 30-day PE-related adverse events, but not with non-PE-related mortality.

Acute Pulmonary Embolism: Prognostic Role of Computed Tomography Pulmonary Angiography (CTPA)

Computed Tomography Pulmonary Angiography (CTPA) is considered the gold standard diagnostic technique in patients with suspected acute pulmonary embolism in emergency departments. Several studies have been conducted on the predictive value of CTPA on the outcomes of pulmonary embolism (PE). The purpose of this article is to provide an updated review of the literature reporting imaging parameters and quantitative CT scores to predict the severity of PE.

CT Pulmonary Angiography for Risk Stratification of Patients with Nonmassive Acute Pulmonary Embolism

Purpose

To investigate the prognostic value of an integrative approach combining clinical variables and the Qanadli CT obstruction index (CTOI) in patients with nonmassive acute pulmonary embolism (PE).

Materials and Methods

This retrospective study included 705 consecutive patients (mean age, 63 years; range, 18-95 years) with proven PE. Clot burden was quantified using the CTOI, which reflects the ratio of fully or partially obstructed pulmonary arteries to normal arteries. Patients were subdivided into two groups according to the presence (group A) or absence (group B) of preexisting cardiopulmonary disease. Thirty-day and 3-month mortality was evaluated. CTOI thresholds of 20% and 40% were used to stratify patients regarding outcome (low, intermediate, and high risk). The predictive value of CTOI was assessed through logistic regression analysis.

Results

Analysis included 690 patients (mean age, 63.3 years ± 18 [standard deviation]) with complete follow-up data: 247 (36%) in group A and 443 (64%) in group B. The mean CTOI was 23% ± 19, 30-day mortality was 9.7%, and 3-month mortality was 11.6%. Three-month mortality was higher in group A than in group B (17.8% and 8.1%, respectively; P = .001). Within group B, CTOI predicted outcome and allowed stratification: significantly higher mortality with CTOI greater than 40% (P < .001) and lower mortality with CTOI less than 20% (P = .05). CTOI did not predict outcome in group A. Age was an independent mortality risk factor (P ≤ .04).

Conclusion

CTOI predicted outcome in this cohort of patients with PE and no cardiopulmonary disease, and it may provide a simple single-examination-based approach for risk stratification in this subset of patients.© RSNA, 2020See also the commentary by Kay and Abbara in this issue.

Left atrial size measured on CT pulmonary angiography: another parameter of pulmonary embolism severity? A systematic review

We systematically review the potential role of left atrial (LA) size, evaluated at computed tomography angiography (CTA) in patients with acute pulmonary embolism (PE), as a new parameter of PE severity. A literature search based on PubMed (MEDLINE), Scopus, Cochrane library and Google Scholar databases was performed to locate previous published investigations reporting data on the severity of acute PE based on the evaluation of LA size (either volume, diameter or area). Six studies, corresponding to a total of 990 patients, published between 2012 and 2019 were included into the analysis. The severity of acute PE, in terms of hemodynamic impairment, increases with the reduction of the LA volume and a significant negative correlation was observed between the pulmonary artery obstruction index (PAOI) and the LA area. Similarly, the longest left-to-right as well as the anteroposterior diameters of the LA had a significant positive correlation with the PAOI index for both the measurement. The LA volume significantly decreased with the increasing of the PAOI index. Moreover, a lower LA volume was observed in those subjects with a saddle PE appearing as the best single parameter able to discriminate between patients having or not a saddle acute PE. Intriguingly, PE patients died within 30 days from the acute event had a significant small LA volume compared to survivors. Data obtained from the current medical literature seem to suggest that the evaluation of LA size evaluation could be a new parameter of PE severity. Further and larger prospective studies are needed to confirm preliminary findings.

Risk stratification of acute pulmonary embolism based on the clot volume and right ventricular dysfunction on CT pulmonary angiography

OBJECTIVE

To test the feasibility of the clot volume and right ventricular dysfunction for risk stratification of acute pulmonary embolism (APE) patients.

METHODS

CT pulmonary angiography (CTPA) images of 158 APE patients were collected. After excluding 38 (24.1%) patients due to unsatisfactory quality, 120 APE patients (61 males and 59 females) were divided into high-risk (n = 37) and non-high-risk (n = 83) groups. Clot burden was measured by an automated programme (clot volume) and by two semi-quantitative systems (Qanadli and Mastora scores). The ratios of the right ventricular diameter to left ventricular diameter (RVd/LVd) and area (RVa/LVa) were obtained. The correlations amongst the above parameters were analysed. Receiver operating characteristic (ROC) curves were calculated to determine the efficacy of high-risk APE. Multivariate analyses were used to identify the independent predictors.

RESULTS

Strong positive correlations were found between the clot volume and both Qanadli score (r²  = 0.696, P < 0.001) and Mastora score (r²  = 0.728, P < 0.001), and moderate correlations were found between the clot volume and both RVd/LVd (r²  = 0.392, P < 0.001) and RVa/LVa (r²  = 0.389, P < 0.001). The clot volume contributed the highest efficacy (AUC = 0.992) for the identification of high-risk cases, followed by Mastora score (0.968), Qanadli score (0.952), RVa/LVa (0.900) and RVd/LVd (0.892). The clot volume and RVd/LVd were two independent factors of high-risk APE.

CONCLUSIONS

The clot volume is correlated with semi-quantitative clot burden scores and CT measured cardiac parameters. The clot volume and RVd/LVd were two independent factors of high-risk APE patients.

Can a Trained Radiology Technician Do Arterial Obstruction Quantification in Patients With Acute Pulmonary Embolism?

Objectives: To assess interobserver variability between a trained radiology technician (RT) and an experienced radiologist in arterial obstruction quantification using the Qanadli obstruction index (QOI), in patients diagnosed with acute pulmonary embolism (APE) at CT pulmonary angiography (CTPA).

Materials and Methods: A RT and a radiologist independently reviewed CTPAs of 97 consecutive, prospectively enrolled patients with APE, and calculated the QOI. They classified patients into three risk categories: high for QOI ≥40%, intermediate for QOI 20–37.5%, low for QOI <20%. Interobserver variability was investigated for QOI as a continuous variable and as a categorical variable (high, intermediate, and low-risk groups).

Results: Mean QOI (±SD) was 39.5 ± 24.3% and 38.6 ± 18.9% for the RT and the radiologist, respectively. The mean QOI was not statistically different between the RT and the radiologist (p = 0.502), and the interobserver agreement was excellent (ICC = 0.905). The RT classified 54 patients (55.7%) as high, 17 (17.53%) as intermediate, and 26 (26.8%) as low risk. The radiologist classified 55 patients (56.7%) as high, 22 (22.7%) as intermediate, and 20 (20.6%) as low risk. The interrater agreement for risk stratification was excellent (weighted kappa = 0.844).

Conclusion: Once the diagnosis of APE was established, an adequately trained RT achieved an accuracy comparable to that of an experienced radiologist regarding QOI calculation and risk assessment.