European Journal of Cardiovascular Medicine

The Clinical Imperative in Acute PE

Acute pulmonary embolism (PE) represents a significant global health burden, ranking as the third most frequent cause of cardiovascular death, surpassed only by myocardial infarction and stroke. [1]. In the Indian subcontinent, its incidence is estimated at 15.9% in adults, with a staggering mortality rate in 80% of these cases. If left untreated, the condition carries an overall mortality rate that can reach 30%, a figure that underscores the urgency of accurate diagnosis and effective management [14]. The clinical presentation of PE is notoriously variable, spanning a wide spectrum from being an asymptomatic, incidental finding on imaging to causing profound obstructive shock and sudden cardiac death [2]. This heterogeneity makes clinical assessment challenging and necessitates a robust framework for risk stratification to tailor therapeutic intensity to individual patient risk.

The primary goal of modern PE management is to prevent early mortality, which is almost invariably caused by acute right ventricular (RV) failure secondary to a sudden increase in pulmonary vascular resistance [6]. The embolic obstruction of the pulmonary arterial tree imposes a severe afterload on the thin-walled right ventricle, leading to dilatation, hypokinesis, and eventually, cardiogenic shock and circulatory collapse. Therefore, identifying patients at high risk for hemodynamic decompensation is the cornerstone of effective treatment, and any diagnostic modality that can simultaneously confirm the diagnosis and assess its physiological impact on the heart offers a profound clinical advantage.

Beyond Diagnosis: The Shift of CTPA Towards Prognostic Imaging

The diagnostic pathway for PE has evolved considerably. Historically, ventilation-perfusion (V/Q) scintigraphy was a mainstay, but its utility was often limited by indeterminate results. Invasive catheter-based pulmonary angiography, once the gold standard, has been largely supplanted due to its invasive nature and associated risks. The advent of multi-detector computed tomography (MDCT) revolutionized PE diagnosis. Computed Tomography Pulmonary Angiography (CTPA) has emerged as the undisputed diagnostic standard, valued for its high sensitivity (96%-100%) and specificity (89%-96%), rapid acquisition, broad availability, and its ability to directly visualize thrombi within the pulmonary arterial tree [3]. Furthermore, it offers the crucial benefit of identifying alternative or ancillary diagnoses, such as pneumonia or aortic dissection, which can mimic the symptoms of PE [12].

This evolution has precipitated a paradigm shift in the role of the CTPA examination itself. Initially, the primary clinical question posed to a CTPA was binary: "Is there a PE?" However, as therapeutic options have become more sophisticated, ranging from anticoagulation to advanced catheter-directed therapies, the need for more nuanced information at the point of diagnosis has grown. This study is predicated on the hypothesis that the CTPA can transcend its role as a static, diagnostic image and become a source of dynamic, actionable data. It posits that a single imaging modality can diagnose, risk-stratify, and trigger the entire downstream therapeutic cascade, transforming the radiologist's report from a simple observation into a critical determinant of immediate clinical action.

The Central Challenge: Risk-Stratifying the Intermediate-Risk Patient

Current international guidelines, most notably from the European Society of Cardiology (ESC), advocate for a risk-stratification model that categorizes patients into low, intermediate, or high-risk groups based on hemodynamic stability, clinical severity scores, and evidence of RV dysfunction [1]. The management pathways for the extremes of this spectrum are well-defined. High-risk patients, defined by the presence of shock or hypotension, require immediate reperfusion therapy. Low-risk patients can often be managed safely with anticoagulation alone [20], with some even being candidates for outpatient treatment.

The central clinical challenge lies in the management of the large and heterogeneous group of "intermediate-risk" patients. These individuals are hemodynamically stable at presentation but exhibit evidence of RV dysfunction or myocardial injury [18]. This group has a significant risk of subsequent clinical deterioration, and identifying the subset of patients—often termed "intermediate-high risk", who might benefit from more aggressive therapies beyond standard anticoagulation is an area of intense clinical debate. It is within this context that prognostic tools capable of refining risk assessment at the initial point of diagnosis are most critically needed. An objective, reproducible method for quantifying the severity of the embolic insult and its immediate impact on the heart can provide the granularity required to sub-stratify this ambiguous group, allowing clinicians to intervene proactively before hemodynamic collapse occurs.

Pillars of Prognostication: Quantifying Clot Burden and RV Dysfunction

CTPA is uniquely positioned to provide this crucial prognostic information at the same time as diagnosis by assessing two key factors: the anatomical extent of the clot burden and its physiological impact on the right ventricle.

Anatomical Clot Burden: Intuitively, the extent of the embolic obstruction should correlate with the severity of the disease. To objectively quantify this, the Qanadli obstruction index, a well-validated and reproducible semi-quantitative scoring system, estimates the percentage of the pulmonary arterial tree that is obstructed by weighting thrombi based on their location and degree of occlusion. This provides an objective measure of the anatomical insult 10].

Right Ventricular Dysfunction (RVD): As previously noted, the pathophysiology of life-threatening PE is centered on acute RV failure [6]. A simple, reproducible, and robust marker of this process on CTPA is the RV/LV diameter ratio. An RV/LV ratio greater than 1.0, indicating that the right ventricle is larger than the left, is widely accepted as a sign of RVD and has been consistently associated with adverse clinical outcomes, including 30-day mortality [4]. A landmark meta-analysis demonstrated that an increased RV/LV ratio was associated with a 2.5-fold increased odds of all-cause mortality and a 5.0-fold increased odds of PE-related mortality.

Rationale for the Current Study

While the prognostic value of CTPA-derived markers is increasingly recognized, there is a continuous need for validation in diverse patient populations and healthcare settings. Most large-scale studies have been conducted in North American or European populations. This study was designed to prospectively evaluate the diagnostic and prognostic utility of the RV/LV diameter ratio and the Qanadli index in a cohort of patients with suspected PE at a large tertiary care center in North India. By investigating the relationship between the anatomical clot burden (Qanadli index) and its direct hemodynamic consequence (RV/LV ratio), this research aims to provide a clearer understanding of how these two key markers can be integrated to enhance risk stratification at the point of initial diagnosis and, critically, to inform the selection of patients for advanced interventional therapies.

Aims and Objectives

Primary Objective: To evaluate the role of CTPA-derived quantitative markers, specifically the RV/LV diameter ratio and the Qanadli pulmonary artery obstruction index (PAOI), in diagnosing and predicting the severity of pulmonary embolism.

Secondary Objectives:

• To determine the correlation between the degree of pulmonary artery obstruction (Qanadli index) and the extent of right ventricular strain (RV/LV ratio).
• To identify independent CT-based predictors for the presence of acute PE.
• To explore the implications of these CTPA findings for guiding advanced therapeutic strategies, including those offered by interventional radiology.

This prospective, observational, cross-sectional study was conducted at the Department of Radiodiagnosis and Department of Interventional Radiology, Mahatma Gandhi Medical College & Hospital, Jaipur, India, a tertiary care referral center. All procedures were performed in accordance with the ethical standards of the Declaration of Helsinki. Written informed consent was obtained from all participants or their legal guardians prior to enrollment in the study.

Patient Population

The study population consisted of 70 consecutive adult patients who were referred to the radiology department for CTPA with a clinical suspicion of PE. Clinical suspicion was based on the presence of signs and symptoms such as acute-onset dyspnea, pleuritic chest pain, hemoptysis, or syncope.

Inclusion criteria encompassed all patients referred for CTPA with a clinical suspicion of pulmonary embolism. Exclusion criteria were: (1) refusal to provide informed consent; (2) pregnancy or lactation; (3) known severe hypersensitivity or a history of an anaphylactic reaction to iodinated contrast media; and (4) severe renal impairment (acute or chronic kidney disease) that precluded the safe administration of intravenous contrast.

CTPA Protocol: Image Acquisition and Reconstruction

All CTPA examinations were performed on a 128-slice GE Optima CT scanner using a standardized protocol. A preliminary non-contrast, low-dose screening scan of the chest was performed from the lung apices to the bases at 120/140 kVp and 250-350 mA.

For the contrast-enhanced phase, an 18- or 20-gauge intravenous cannula was placed in an antecubital vein. A total of 80 to 90 mL of a non-ionic, low-osmolar iodinated contrast agent was administered at a rate of 4–5 ml/s using a power injector, followed by a 40 mL saline chaser bolus at the same rate. Scan acquisition was timed using an automated bolus-tracking technique. A region of interest (ROI) was placed within the main pulmonary artery (MPA), and scanning was automatically triggered once the attenuation within the ROI reached a predefined threshold of 150 Hounsfield Units (HU). Scanning was performed in a single breath-hold during inspiration, proceeding in a caudocranial direction from the diaphragm to the lung apices to minimize respiratory motion artifact in the lung bases. Images were reconstructed as thin axial sections of 1-2 mm thickness with a 1 mm overlap to allow for high-quality multiplanar reformations.

Image Analysis and Quantitative Measurements

All CTPA images were transferred to a dedicated picture archiving and communication system (PACS) workstation and were independently reviewed by two radiologists with expertise in cardiovascular imaging; any discrepancies were resolved by consensus.

Diagnosis of Pulmonary Embolism: The definitive diagnosis of acute PE was based on the direct visualization of an intraluminal filling defect within a pulmonary artery, manifesting as a central or eccentric defect or a complete vessel occlusion.

Qanadli Index (Pulmonary Artery Obstruction Index - PAOI): The severity of pulmonary arterial obstruction was quantified using the Qanadli scoring system. This method involves a systematic assessment of all 20 segmental pulmonary arteries (10 per lung). For each embolus, two values are determined:

• Location score (n): The value assigned to the most proximal location of the thrombus, equal to the number of distal segmental arteries supplied by that vessel.
• Obstruction score (d): A weighting factor where d=1 for a partial defect and d=2 for a complete, occlusive defect.

The total Qanadli score is calculated by summing the product of these two values for each embolus: ∑(n×d). The final index is expressed as a percentage of the maximum possible score of 40: (∑(n×d)/40)×100%.

RV/LV Diameter Ratio: Right ventricular strain was assessed by measuring the RV/LV diameter ratio. On the axial image that best demonstrated the maximal dimensions of both ventricles, typically just below the level of the mitral and tricuspid valves, the largest short-axis diameter of the RV and LV was measured [15]. The measurement was taken from the inner surface of the ventricular free wall to the interventricular septum, perpendicular to the long axis of the heart. This method is highly practical and has been shown to be accurate and reproducible.

Other Measurements: The maximal diameters of the main pulmonary artery (at the level of its bifurcation), the ascending aorta (at the same level), and the coronary sinus were also measured on axial images.

Statistical Analysis

All data were entered into a database and analyzed using SPSS Statistics version 29 (IBM Inc, USA). The distribution of continuous variables was assessed for normality using the Shapiro-Wilk test. Descriptive statistics were calculated and are presented as mean ± standard deviation (SD) for continuous variables and as frequencies and percentages for categorical variables. The independent-samples t-test was used to compare the means of continuous variables between the PE-positive and PE-negative groups. The Chi-square test or Fisher's exact test, as appropriate, was used to assess associations between categorical variables. The Pearson correlation coefficient (r) was calculated to measure the strength and direction of the linear relationship between the Qanadli index and the RV/LV ratio. To identify independent predictors of PE, a multivariate logistic regression model was constructed. Variables that were significant in the univariate analysis or deemed clinically relevant (gender, age, Qanadli index, and RV/LV ratio) were entered into the model. For all statistical tests, a two-tailed p-value of less than 0.05 was considered statistically significant.

Cohort Characteristics and Clinical Presentation

Of the 70 patients with clinically suspected PE who underwent CTPA, 40 (57.1%) were diagnosed with acute PE. The mean age of the cohort was 48.9±20 years, with a range from 0.04 to 79 years. The cohort was predominantly male (50 patients, 71.4%), as shown in Figure 1. While patients with confirmed PE were, on average, older, a statistically significant difference was observed when analyzed by age categories (p=0.032), with a higher proportion of PE patients in the 40.1–60 years age group. The baseline demographic, clinical, and comorbidity data for the entire cohort, stratified by PE status, are presented in Table 1.

The most common presenting symptoms were dyspnea and chest pain, each occurring in 60% of the total cohort (Figure 2). Notably, a history of deep vein thrombosis (DVT) was significantly more prevalent in patients with confirmed PE compared to those without (23.1% vs. 3.3%, p=0.035). As expected, mean D-dimer levels were also significantly elevated in the PE-positive group (2002±1985 ng/mL) compared to the PE-negative group (1109±693 ng/mL, p=0.033).

Table 1: Baseline Demographic and Clinical Characteristics of the Study Cohort

Data are presented as mean ± SD or n (%). P-values < 0.05 are in bold.

Figure 1: Gender Distribution of the Study Cohort (N=70)

Figure 2: Frequency of Presenting Symptoms in the Overall Cohort (N=70)

CTPA Findings: Embolus Location and Prognostic Markers

Among the 40 patients with PE, emboli were located in central (main, trunk, or lobar) and peripheral (segmental or subsegmental) arteries, with the right pulmonary artery and its branches being the most common sites of involvement. The core quantitative CTPA measurements demonstrated significant differences between the PE and non-PE groups, as shown in Table

The most striking finding was the mean RV/LV ratio, which was significantly higher in patients with PE (1.06±0.20) compared to those without PE (0.86±0.10), a difference that was highly statistically significant (p<0.001) (Figure 3).

The mean Qanadli index, calculated for the 40 patients with PE, was 56.1%±28.5%, indicating a moderate to severe overall clot burden in this cohort. The distribution of PE severity by the Qanadli index is illustrated in Figure 4, showing that over half of the patients with PE (57.5%) had a clot burden exceeding 50%.

Table 2: Comparison of CTPA-Derived Cardiovascular Measurements

Data are presented as mean ± SD. P-values < 0.05 are in bold. N/A: Not Applicable.

Figure 3: Comparison of RV/LV Diameter Ratio in Patients With and Without Pulmonary Embolism

Figure 4: Distribution of PE Severity by Qanadli Obstruction Index in PE-Positive Patients (n=40)

The Core Relationship: Correlation Between Clot Burden and Ventricular Strain

A primary objective of this study was to investigate the relationship between the anatomical extent of the embolic obstruction and its physiological impact on the right ventricle. A statistically significant, strong positive correlation was found between the Qanadli index and the RV/LV ratio (r=0.505, p=0.008). This relationship is visualized in the scatter plot in Figure 5, which demonstrates that as the percentage of pulmonary artery obstruction increases, there is a corresponding and predictable increase in the degree of right ventricular dilatation.

Figure 5: Correlation Between Qanadli Obstruction Index and RV/LV Diameter Ratio

(A scatter plot with Qanadli Index (%) on the x-axis and RV/LV Ratio on the y-axis. Data points show a clear positive trend, visually representing the correlation. The correlation coefficient r=0.505 and p=0.008 are noted on the plot.)

Independent Predictors of Pulmonary Embolism

To identify which factors were independently associated with the presence of PE, a multivariate logistic regression analysis was performed. The overall model was statistically significant (χ2(4)=68.173, p<.0001) and demonstrated excellent predictive power, explaining 84.9% (Nagelkerke R2) of the variance in PE status and correctly classifying 92.9% of cases. The results of the regression analysis are detailed in Table 3. After adjusting for age and gender, two CTPA-derived parameters emerged as significant independent predictors for the presence of PE: an increased RV/LV ratio and an elevated Qanadli index. Furthermore, a Receiver Operating Characteristic (ROC) curve analysis determined that an RV/LV ratio cutoff of 0.89 provided the optimal balance of sensitivity and specificity for discriminating between patients with and without PE.

Table 3: Multivariate Logistic Regression Analysis for Predictors of Pulmonary Embolism

P-values < 0.05 are in bold.

Illustrative Cases from the Cohort

The following cases from the study cohort illustrate the spectrum of findings on CTPA, from acute, high-burden PE causing significant hemodynamic stress to the more subtle signs of chronic thromboembolic disease.

Case 1: CT angiogram of a 60-year-old male patient with thromboembolism in the ascending and descending branches of the right pulmonary artery, extending to the adjacent right upper and lower lobe, segmental and subsegmental pulmonary branches, as well as some segmental-subsegmental branches of the left lobar pulmonary artery.

Figure 6: Acute Massive Pulmonary Embolism

(This case exemplifies a high clot burden, with extensive thrombus visible in the central and peripheral pulmonary arteries. Such widespread obstruction would correspond to a high Qanadli index and is typically associated with significant right ventricular strain, as evidenced by an elevated RV/LV ratio.)

Case 2: CT angiogram of a 52-year-old male with a hypodense filling defect suggestive of thrombus in lobar and segmental-subsegmental branches of the right upper, middle, left lingula and both lower lobe pulmonary arteries.

Figure 7: Bilateral Lobar and Segmental PE

(This image clearly demonstrates the characteristic appearance of acute thrombus as hypodense filling defects within multiple lobar and segmental branches. The direct visualization of these defects is the primary diagnostic strength of CTPA.)

Case 3 : CT angiogram of a 47-year-old male showing an intraluminal filling defect indicative of a pulmonary thromboembolism in the left upper lobar pulmonary artery branch, as well as in the segmental and subsegmental pulmonary artery branches of the left lingula and lower lobe.

Figure 8: Central and Peripheral PE

(This case illustrates the involvement of both proximal (lobar) and distal (segmental, subsegmental) vessels. The ability of modern multidetector CT to resolve these smaller, peripheral clots is crucial for accurate diagnosis and for calculating a comprehensive clot burden score.)

Case 4 : CT angiogram of a 54-year-old female demonstrates linear hypodense bands with subtle partial eccentric filling defects within the lumen of segmental and subsegmental branches of the bilateral lower lobe pulmonary arteries, indicative of chronic thromboembolism.

Figure 9: Chronic Thromboembolism

(In contrast to the acute findings, this image shows features of chronic, organized thrombus. The linear, web-like bands and subtle eccentric defects are characteristic of chronic thromboembolic disease, which can be a long-term sequela of acute PE and may lead to chronic thromboembolic pulmonary hypertension (CTEPH).)

Case 5 : CT angiogram of a 61-year-old male demonstrating partial eccentric filling defects in the descending branch of the right pulmonary artery, the adjacent right inferior lobar pulmonary artery, and its segmental-subsegmental branches. Additionally, partial defects are observed in the left pulmonary artery at the hilum and the adjacent left inferior lobar pulmonary artery, indicative of chronic thromboembolism.

Figure 10: Chronic Eccentric Thromboembolism

(This case further highlights the typical appearance of chronic PE. The filling defects are eccentric, adhering to the vessel wall, rather than centrally located like many acute emboli. This finding is critical for differentiating acute from chronic disease, which has significant therapeutic implications.)

Case 6: CT angiogram of a 41-year-old male revealing partial intraluminal thrombosis in the upper and lower branches of the right pulmonary artery, resulting in mild luminal compromise. Additionally, minimal partial intraluminal thrombosis is observed in the lower lobe branches of the left pulmonary artery.

Figure 11: Partial Intraluminal Thrombosis

(This image demonstrates a case of non-occlusive thrombus. While not completely blocking the vessel, this partial thrombosis still contributes to the overall clot burden and can cause significant perfusion deficits, underscoring the importance of identifying both occlusive and non-occlusive emboli.)

This prospective study confirms and extends the understanding of CTPA's role in acute pulmonary embolism, demonstrating that it serves as more than just a diagnostic tool. The principal finding is that quantitative markers of right ventricular strain (RV/LV ratio) and pulmonary artery clot burden (Qanadli index), derived from the initial diagnostic scan, are not only strongly correlated but also function as independent predictors for the presence of PE. This dual capacity of CTPA—to provide a definitive diagnosis and immediate prognostic information—is of paramount importance for the timely and appropriate risk stratification of patients, particularly in the context of modern, multidisciplinary management pathways.

The Pathophysiological Link: A Quantitative Bridge from Clot Burden to Ventricular Strain

A cornerstone of this study is the demonstration of a strong, significant positive correlation between the Qanadli index and the RV/LV ratio (r=0.505). This statistical finding provides a powerful in-vivo visualization of the fundamental pathophysiological cascade that defines severe PE [6]. The Qanadli index offers an objective, anatomical measure of the embolic burden obstructing the pulmonary vasculature, the primary insult or "cause". As this obstruction increases, pulmonary vascular resistance rises acutely, imposing a sudden and severe afterload on the right ventricle. The RV/LV ratio, in turn, provides a quantitative measure of the heart's response to this hemodynamic stress—the immediate "effect" [16]. The direct correlation observed in this study quantitatively links this cause to its effect, transforming a theoretical concept into a measurable clinical reality.

This provides a clear mechanistic rationale for why both markers are independently predictive in the multivariate analysis. They are not redundant; rather, they offer complementary information. The Qanadli index reflects the magnitude of the primary insult, while the RV/LV ratio reflects the patient's specific hemodynamic response to that insult. This interplay is crucial, as the same degree of clot burden may result in different degrees of RV strain depending on a patient's pre-existing cardiopulmonary reserve. This result lends strong support to the emerging concept of integrated or combined scoring systems, which propose that incorporating both anatomical and physiological parameters provides superior predictive power for short-term mortality compared to either marker alone [18].

Clinical Implications and Contextualization of CTPA Markers

The finding that the mean RV/LV ratio was significantly elevated in PE patients (1.06) aligns with a large body of literature that has established RV dilatation as a key prognostic marker [17]. Numerous meta-analyses and large cohort studies have consistently shown that an RV/LV ratio >1.0 on CTPA is a robust predictor of adverse outcomes, including 30-day all-cause mortality, PE-related mortality [14], and the need for rescue therapies. A particularly novel finding from this study's analysis is the identification of an RV/LV ratio cutoff of 0.89 for discriminating the presence of PE. This does not imply that a normal-sized RV is indicative of PE. Rather, it suggests that in a population of patients with clinical suspicion of PE, even subtle increases in RV size, below the traditional prognostic threshold of 1.0, are highly associated with the presence of an underlying embolic process. This positions the RV/LV ratio as a potentially sensitive ancillary diagnostic marker. In cases where intraluminal filling defects are small or equivocal, the presence of even mild RV dilatation could increase confidence in a positive diagnosis.

This study also found that the Qanadli index was a significant independent predictor of PE (OR = 1.412), contributing valuable information even after accounting for the effect of RV dilatation. This result contributes to an ongoing discussion in the literature regarding the index's utility. While some studies have suggested its standalone prognostic value for mortality is limited, this study's findings align with other research demonstrating that a high clot burden is a significant predictor of adverse outcomes [11] and correlates with long-term complications like pulmonary hypertension. The most balanced interpretation is that the Qanadli index is an invaluable objective measure of the anatomical severity of the disease. While ultimate prognosis is dictated by the patient's hemodynamic response (RVD), the clot burden represents the primary driver of this response. Its strength lies in quantifying the extent of vascular obstruction, which is crucial for planning interventions (such as catheter-directed thrombolysis or surgical embolectomy) and for monitoring treatment response on follow-up imaging.

Forging the Imaging-Intervention Axis with Bridging Prognosis to Intervention: The Role of Interventional Radiology Guiding the PERT Model

The findings of this study have profound implications that extend beyond diagnosis and into the realm of advanced therapeutic intervention. The ability of CTPA to quantify both clot burden and RV strain provides the critical, front-line data necessary to forge a direct, efficient "scan-to-intervention" pathway, guided by a multidisciplinary Pulmonary Embolism Response Team (PERT) [7, 20]. The establishment of PERTs represents a paradigm shift in the management of high-risk PE, moving from a sequential, single-specialty consultation model to a rapid, collaborative, and evidence-based approach. The quantitative data from CTPA is the fuel for this modern workflow.

This evidence-based pathway can be conceptualized as follows:

1. Initial Diagnosis and Triage: A patient with suspected PE undergoes a CTPA. The resulting report is no longer a simple binary confirmation but a quantitative risk assessment, stating, for example, "PE positive with a Qanadli Index of 65% and an RV/LV Ratio of 1.4."
2. PERT Activation: These objective, high-risk markers, validated by this study, serve as an automatic trigger for the activation of the institution's PERT. This team typically includes specialists from interventional radiology, cardiology, pulmonary/critical care, and cardiac surgery.
3. Rapid, Data-Driven Decision-Making: The PERT convenes (often virtually), using this precise CT data to rapidly risk-stratify the patient as intermediate-high or high-risk. This bypasses the potential need for additional, time-consuming tests like formal echocardiography, allowing for a more immediate and informed decision.
4. Deployment of Advanced Therapies: Based on the high clot burden and evidence of severe RV strain, the PERT can recommend advanced reperfusion therapies. For patients with intermediate-high-risk or high-risk PE, standard anticoagulation may be insufficient. While systemic thrombolysis is an option, it carries a significant risk of major bleeding. This has paved the way for minimally invasive, catheter-directed therapies (CDT) performed by interventional radiologists, which include Catheter-Directed Thrombolysis, Ultrasound-Assisted Thrombolysis (USAT), and Percutaneous Mechanical Thrombectomy [19].

For patients with intermediate-high-risk or high-risk PE, standard anticoagulation may be insufficient [1]. In these cases, rapid reperfusion is necessary to alleviate the afterload on the right ventricle. While systemic thrombolysis is an option, it carries a significant risk of major bleeding. This has paved the way for minimally invasive, catheter-directed therapies (CDT) performed by interventional radiologists, which include:

• Catheter-Directed Thrombolysis: Low-dose infusion of a thrombolytic agent directly into the clot, maximizing efficacy while minimizing systemic bleeding risk.
• Ultrasound-Assisted Thrombolysis (USAT): Utilizes ultrasound waves to increase the penetration and effectiveness of the co-administered thrombolytic agent.
• Percutaneous Mechanical Thrombectomy/Aspiration: Uses specialized catheters to mechanically break up or aspirate the thrombus, achieving immediate debulking.

Studies have shown that these interventions can lead to significant and rapid improvements in the RV/LV ratio and reduction in clot burden scores [8, 9]. The objective CTPA findings from studies like this one provide the evidence base for a PERT to formulate a consensus recommendation for the best course of action. A high clot burden coupled with a dilated right ventricle provides a clear signal that a patient may benefit from immediate consideration for advanced intervention.

Strengths and Limitations

The primary strength of this study is its prospective design, which minimizes the selection and information bias inherent in many retrospective analyses. The use of a modern 128-slice CT scanner and a standardized protocol for image acquisition and measurement enhances the internal validity and reproducibility of the findings.

However, several limitations must be acknowledged. The study was conducted at a single center with a relatively modest sample size of 70 patients, which may limit the generalizability of the findings and increases the risk of a Type II statistical error. The primary endpoint of the analysis was the presence or absence of PE, not long-term clinical outcomes such as morbidity or 30-day mortality. Therefore, while the study robustly demonstrates that the RV/LV ratio and Qanadli index are predictive of the presence and severity of PE, direct conclusions about their ability to predict mortality cannot be drawn from this dataset alone. Additionally, the study did not include a direct, systematic comparison with echocardiography, which remains a key tool for assessing RV function, nor did it correlate findings with cardiac biomarkers like troponin, which are integral to ESC risk stratification. Future research should aim to validate these findings in larger, multi-center prospective trials that correlate CTPA parameters with hard clinical outcomes and compare them directly with echocardiographic and biomarker data.

Computed Tomography Pulmonary Angiography is an indispensable tool that extends beyond the accurate diagnosis of acute pulmonary embolism to provide crucial, immediate prognostic information that can guide clinical management. This study demonstrates that the quantitative assessment of both the anatomical clot burden, via the Qanadli index, and its resultant hemodynamic impact on the right ventricle, via the RV/LV diameter ratio, offers a powerful and integrated approach to patient risk stratification.

The strong correlation between these two markers underscores a direct pathophysiological link, while their independent predictive value highlights their complementary roles in a comprehensive assessment. The routine incorporation of these simple, reproducible measurements into standard CTPA reporting can transform a diagnostic test into a vital prognostic tool, facilitating more timely and tailored care for patients with this life-threatening condition. Crucially, these imaging biomarkers serve as the nexus between diagnosis and advanced therapy, providing the objective evidence needed by multidisciplinary teams to identify high-risk patients who may benefit from life-saving interventions delivered by interventional radiology.

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