Validation of intravascular ultrasound for measurement of aortic diameters: Comparison with multi-detector computed tomography

Influence of measurement and sizing techniques in thoracic endovascular aortic repair on outcome in acute complicated type B aortic dissections

OBJECTIVES

Thoracic endovascular aortic repair (TEVAR) is the first-line therapy in acute complicated type B aortic dissections (cTBAD). Nevertheless, no evidence-based consensus on the optimal measurement technique and sizing for TEVAR in cTBAD exists. The aim was to evaluate how different measurement and sizing techniques for TEVAR affect long-term outcomes.

METHODS

Retrospective analysis investigating the association between sizing and postoperative results after TEVAR in patients with cTBAD, treated between January 2003 and December 2020. Diameter measurements were performed perpendicular to a centreline in pre-interventional Computed tomography angiographies. Oversizing was determined by measuring aortic diameter in zone 2 of the aortic arch in relation to the implanted stent graft, and categorized into 2 sizing groups (≤10% and >10%). The primary outcome was freedom from aortic-related events. Secondary outcomes included mortality and a comparison of 3 alternative measurement techniques considering the estimated pre-dissection diameter.

RESULTS

Fifty-seven patients (median age 69, interquartile range 59.6-78.2 years) were included. Stent graft oversizing by ≤10% showed a trend towards fewer aortic-related events hazard ratio 0.455 (95% confidence interval 0.128-1.624, P = 0.225).The 3 measurement techniques using the pre-dissection aortic diameter differed by a mean of 1.7-4.0 mm with a variability of up to 8.4 mm. In none of the 57 patients, the same stent graft would have been chosen based on the different measurement techniques using an oversizing ≤10%.

CONCLUSIONS

TEVAR oversizing of ≤10% in patients with cTBAD might reduce aortic-related events up to 50%. Consensus on measurement techniques of the pre-dissection aortic diameter and stent graft sizing is of paramount importance.

Initiating a New Era of Cardiovascular Diagnosis and Therapy in Acute Aortic Syndromes: The Mainz-Essen Experience (Part I)-Imaging and Biomarkers

Acute aortic syndromes (AAS) encompass a group of life-threatening medical conditions (acute aortic dissection [AAD], intramural hematoma, and penetrating aortic ulcer) with a common pathophysiological pathway. Due to overlapping symptoms and signs with other cardiovascular emergencies, the diagnosis remains challenging resulting in time delays and related increased in-hospital and long-term morbidity and mortality. The Cardiovascular Department of Johannes Gutenberg University in Mainz at West-German Heart Centre in Essen (Germany) first described (in 1984) AAD by transesophageal echocardiography, AAD diagnostic features, and furtherly explored the implementation of "invasive" imaging techniques, namely, intravascular ultrasound and intraluminal phased-array imaging. Furthermore, pioneer studies were undertaken on the biomarker and imaging interplay, namely, D-dimer and F-fluorodeoxyglucose positron emission tomography/computed tomography. We discuss the unique 35-year-long Mainz-Essen experience on the diagnostic and prognostic role of serological and imaging biomarkers in AAS.

Important issues regarding planning and sizing for emergent TEVAR

In the past decades, treatment of acute thoracic aortic syndrome underwent drastic changes with a central role for thoracic endovascular aortic repair (TEVAR). One of the essential factors in the success of TEVAR is accurate sizing of the endograft, as both under- and oversizing can lead to suboptimal results and disastrous complications. The aim of this review was to give an overview of issues regarding endograft sizing in emergent TEVAR. Sizing of the endograft can be complicated by specific factors related to the underlying disease. For instance, different types of the acute thoracic aortic syndrome, i.e. blunt thoracic injury, thoracic aortic aneurysm or dissection with concomitant rupture are associated with hemorrhagic shock and the need for resuscitation, which leads to profound changes in diameter of the thoracic aorta. These diameter changes should be taken into account during endograft sizing. Measuring the thoracic aorta based on the admission CTA can lead to inaccurate sizing, even if proper centerline-based measurements are performed. The use of real-time imaging, in particular intravascular ultrasound (IVUS), has been shown to provide more accurate endograft sizing in acute thoracic aortic syndromes, especially if associated with hypovolemia. Future research should provide additional data on the exact role of different intra-operative imaging modalities (e.g. IVUS, transesophageal echocardiography [TEE], three dimensional CTA) on endograft sizing and long-term outcomes to ultimately improve patient outcome.

Acute aortic syndromes: diagnosis and management, an update

Acute aortic syndromes (AAS) encompass a constellation of life-threatening medical conditions including classic acute aortic dissection (AAD), intramural haematoma, and penetrating atherosclerotic aortic ulcer. Given the non-specific symptoms and physical signs, a high clinical index of suspicion is necessary to detect the disease before irreversible lethal complications occur. In order to reduce the diagnostic time delay, a comprehensive flowchart for decision-making based on pre-test sensitivity of AAS has been designed by the European Society of Cardiology guidelines on aortic diseases and should be thus applied in the emergency scenario. When the definitive diagnosis is made, prompt and appropriate therapeutic interventions should be undertaken if indicated by a highly specialized aortic team. Urgent surgery for AAD involving the ascending aorta (Type A) and medical therapy alone for AAD not involving the ascending aorta (Type B) are typically recommended. In complicated Type B AAD, thoracic endovascular aortic repair (TEVAR) is generally indicated. On the other hand, in uncomplicated Type B AAD, pre-emptive TEVAR rather than medical therapy alone to prevent late complications, while intuitive, requires further study in randomized cohorts. Finally, it should be highlighted that there is an urgent need to increase awareness of AAS worldwide, including dedicated education/prevention programmes, and to improve diagnostic and therapeutic strategies, outcomes, and lifelong surveillance.

Hemodynamic changes lead to alterations in aortic diameters and may challenge further stent graft sizing in acute aortic syndrome

Background

Precise stent graft sizing in Thoracic endovascular aortic repair (TEVAR) is crucial to receive optimal long-term results. Computed tomography (CT), as the current standard in assessing aortic diameters (ADs), is often performed at initial diagnosis. Since several acute aortic diseases are associated with blood loss and/or volume re-distribution, assessed AD might be influenced by impaired hemodynamic conditions. Intravascular ultrasound (IVUS) offers real-time assessment, especially after hemodynamic restoration, and might help for stent graft choice.

Methods

We investigated the correlation between CT and later IVUS measurements in elective (n=83) and emergency patients (n=32) at the level distal to the left subclavian artery (LSA), a frequent proximal landing zone in TEVAR. Patients were grouped depending on their shock index (heart rate/systolic blood pressure): emergency patients with diagnosis of acute aortic syndrome, urgently required treatment after admission and had a shock index >1, otherwise were grouped as elective. Basic hemodynamics were assessed for both groups at admission and at definite IVUS-procedure.

Results

At time of admission the emergency group showed lower blood pressure (99±19.8 vs. 141±24 mmHg; P=0.001) and higher heart rate (98±13 vs. 70±12 bpm; P=0.001) compared to elective patients. By hemodynamic stabilization comparable blood pressure and heart rate were achieved in both groups at time of IVUS. In the emergency group, we found a significantly increase in AD after hemodynamic stabilization, whereas the diameters did not change in the elective group (IVUS_meanvs. CT_mean: 5.1±1.0 vs. 0.4±2.2 mm; P=0.001 and IVUS_minvs. CT_mean: 3.9±1.3 vs. -0.3±2.2 mm; P=0.011).

Conclusions

IVUS for stent graft sizing is a valuable approach during TEVAR, especially in the light of emergency treatment by offering real-time assistance. Impaired hemodynamic conditions might lead to relevant changes in AD and may strongly influence stent graft choice. In these cases, careful stent graft selection might contribute to avoidance of stent graft related complication.

Intravascular ultrasound assisted sizing in thoracic endovascular aortic repair improves aortic remodeling in Type B aortic dissection

The precise sizing of the stent graft in thoracic endovascular aortic repair (TEVAR) affects aortic remodeling and hence, further outcome. Covering the proximal entry tear is essential for successful treatment of Type B aortic dissection. Intravascular ultrasound (IVUS) enables real-time aortic diameter assessment, and is especially useful when computed tomography (CT) image quality is poor. IVUS, however, is not routinely utilized due to cost inefficiency. We investigated the impact of IVUS-assisted stent graft sizing on aortic remodeling in TEVAR. In this single-center retrospective study we evaluated patients with Type B aortic dissection undergoing both CT and IVUS before TEVAR. We assessed the aortic diameter at the level of the left subclavian artery via both methods before stent implantation and analyzed due to which method the implanted stent graft was chosen, retrospectively. To determine the degrees of aortic remodeling involved, we evaluated true lumen and false lumen diameters, and total aortic remodeling in CT. We analyzed 45 patients with Type B aortic dissection undergoing TEVAR. The mean ages were 66.9±10.0 years fo0072 IVUS (n = 20) and 62.3±14.2 years for CT-assisted TEVAR (n = 25; p = 0.226). The follow-up time for both groups did not differ between the two groups (IVUS: 22.9±23.1 months, CT: 25.6±23.0 months; p = 0.700). While both methods were associated with advantages regarding aortic remodeling, IVUS-assisted sizing yielded a greater increase in true lumen (30.4±6.2 vs. 25.6±5.3; p = 0.008) and reductions in false lumen (14.4±8.5 vs. 23.9±9.3; p = 0.001) and total aortic diameter (35.5±6.0 vs. 39.9±8.1; p = 0.045). IVUS-guided stent graft sizing in Type B aortic dissection shows beneficial effects on aortic remodeling and might be of additional advantage in aortic diseases, especially when CT image quality is poor.

Impact of Preoperative Anemia and Postoperative Hemoglobin Drop on the Incidence of Acute Kidney Injury and In-Hospital Mortality in Patients With Type B Acute Aortic Syndromes Undergoing Thoracic Endovascular Aortic Repair

BACKGROUND

The impact of preoperative anemia and postoperative hemoglobin (Hb) drop on the incidence of acute kidney injury (AKI) after thoracic endovascular aortic repair (TEVAR) for type B acute aortic syndromes (AAS) as well as their prognostic value is unknown.

METHODS

This retrospective study included 144 patients with type B AAS undergoing TEVAR at our center. Preoperative anemia was classified as no/mild (Hb ≥ 12.0 g/dL in men; ≥11.3 g/dL in women), moderate (Hb 10.80-11.99 g/dL in men; 10.23-11.29 g/dL in women), and severe (<10.80 g/dL in men; <10.23 g/dL in women). Postoperative Hb drop was classified as mild (<2 g/dL), moderate (2-4 g/dL), and severe (>4 g/dL). End points of the study were postoperative AKI and in-hospital mortality.

RESULTS

Postoperative AKI was higher in the severe and moderate anemia groups than the no/mild anemia group (63.2%, 52.0%, and 31.0%, respectively, P = .01). In-hospital mortality and AKI were higher in patients with severe postoperative Hb drop (40.9% and 86.4%) than patients with moderate (6.9% and 36.2%) and mild (4.7% and 25.0%) postoperative Hb drop (both P < .001). Postoperative Hb drop (odds ratio [OR]:1.67, P = .036), postoperative Hb levels (OR: 0.57, P = .025), and mesenteric ischemia (OR: 4.65, P = .044) were identified as independent predictors of in-hospital mortality. Preoperative Hb (OR: 0.26, P = .001), postoperative Hb drop (OR: 4.34, P < .001), contrast medium (OR: 1.82, P = .004), and diabetes mellitus (OR: 3.79, P = .001) were independent predictors of AKI. At follow-up, anemia and postoperative Hb drop were not associated with increased mortality.

CONCLUSION

Preoperative Hb and postoperative Hb drop were significant risk factors for AKI. Postoperative Hb drop and Hb levels predicted in-hospital mortality.