Intravascular Ultrasound Catheter Research Articles

Rotational Intravascular Multidirectional Ultrasound Catheter for Sonothrombolysis of Retracted Clots: An in Vitro and in Vivo Study

Thromboembolism in blood vessels poses a serious risk of stroke, heart attack, and even sudden death if not properly managed. Sonothrombolysis combined with ultrasound contrast agents has emerged as a promising approach for the effective treatment of thromboembolism. Recent reports have highlighted the potential of intravascular sonothrombolysis as a safe and effective treatment modality for deep vein thrombosis (DVT). However, its efficiency has not been validated through in vivo testing of retracted clots. This study aimed to develop a miniaturized multidirectional transducer featuring two 4-layer lead zirconate titanate (PZT-5A) stacks with an aperture size of 1.4 mm × 1.4 mm, enabling both forward- and side-looking treatment. Integrated into a custom two-lumen 10-French (Fr) catheter, the capability of this device for intravascular sonothrombolysis was validated both in vitro and in vivo. With low-dose tissue plasminogen activators and nanodroplets, the rotational multidirectional transducer reduced the retracted clot mass (800 mg) by an average of 52% within 30 min during in vitro testing. The lysis rate was significantly higher by 37% than that in a forward-viewing transducer without rotation. This improvement was particularly noteworthy in the treatment of retracted clots. Notably, a long-retracted clot (> 10 cm) was successfully treated within 40 min in vivo by creating a flow channel with a diameter > 4 mm in a porcine DVT model. In conclusion, these findings strongly suggest the potential of this technique for clinical applications in sonothrombolysis, offering a feasible solution for effectively treating thromboembolism, particularly in challenging cases involving retracted clots.

A 1.11 mm2 IVUS SoC with ±50°-Range Plane Wave Transmit Beamforming at 40 MHz.

Intravascular ultrasound (IVUS) imaging catheters are significant tools for cardiovascular interventions, and their use can be expanded by realizing IVUS imaging guidewires and microcatheters. The miniaturization of these devices creates challenges in SNR due to the need for higher frequencies to provide adequate resolution. An integrated IVUS system with transmit beamforming can mitigate these limitations. This work presents the first practical highly integrated system-on-a-chip (SoC) with plane wave transmit beamforming at 40 MHz for IVUS on guidewire or microcatheters. The front-end circuitry has a 20-channel ultrasound transmitter (Tx) and receiver (Rx) array interfaced with a capacitive micromachined ultrasound transducer (CMUT) array. During each firing, all 20 Tx are excited with the same analog delay with respect to each other, which can be continuously adjusted between ~0 and 10 ns in two directions, generating a steerable plane wave in a range of ±/-50° for a phased array at 40 MHz. The unit delays are generated via a voltage-controlled delay line (VCDL), which only needs two external controls, one tuning the unit delay and the other determining the steering direction. The SoC is fabricated using a 180-nm high-voltage (HV) CMOS process and features a slender active area of 0.3 mm × 3.7 mm. The proposed SoC consumes 31.3 mW during the receiving mode. The beamformer's functionality and the SoC's overall performance were validated through acoustic characterization and imaging experiments.

Surgical Removal of A Broken Intravascular Ultrasonography Catheter for PCI Followed by Off-Pump Coronary Artery Bypass

Surgical Removal of A Broken Intravascular Ultrasonography Catheter for PCI Followed by Off-Pump Coronary Artery Bypass

CARDIAN: a novel computational approach for real-time end-diastolic frame detection in intravascular ultrasound using bidirectional attention networks.

Changes in coronary artery luminal dimensions during the cardiac cycle can impact the accurate quantification of volumetric analyses in intravascular ultrasound (IVUS) image studies. Accurate ED-frame detection is pivotal for guiding interventional decisions, optimizing therapeutic interventions, and ensuring standardized volumetric analysis in research studies. Images acquired at different phases of the cardiac cycle may also lead to inaccurate quantification of atheroma volume due to the longitudinal motion of the catheter in relation to the vessel. As IVUS images are acquired throughout the cardiac cycle, end-diastolic frames are typically identified retrospectively by human analysts to minimize motion artefacts and enable more accurate and reproducible volumetric analysis. In this paper, a novel neural network-based approach for accurate end-diastolic frame detection in IVUS sequences is proposed, trained using electrocardiogram (ECG) signals acquired synchronously during IVUS acquisition. The framework integrates dedicated motion encoders and a bidirectional attention recurrent network (BARNet) with a temporal difference encoder to extract frame-by-frame motion features corresponding to the phases of the cardiac cycle. In addition, a spatiotemporal rotation encoder is included to capture the IVUS catheter's rotational movement with respect to the coronary artery. With a prediction tolerance range of 66.7 ms, the proposed approach was able to find 71.9%, 67.8%, and 69.9% of end-diastolic frames in the left anterior descending, left circumflex and right coronary arteries, respectively, when tested against ECG estimations. When the result was compared with two expert analysts' estimation, the approach achieved a superior performance. These findings indicate that the developed methodology is accurate and fully reproducible and therefore it should be preferred over experts for end-diastolic frame detection in IVUS sequences.

Intravascular Ultrasound in the Detection of Bridging Stent Graft Instability During Fenestrated and Branched Endovascular Aneurysm Repair Procedures: A Multicentre Study on 274 Target Vessels

The use of intravascular ultrasound (IVUS) reduces contrast medium use and radiation exposure during conventional endovascular aneurysm repair (EVAR). The aim of this study was to evaluate the safety and efficacy of IVUS in detecting bridging stent graft (bSG) instability during fenestrated and branched EVAR (F/B-EVAR). This was a prospective observational multicentre study. The following outcomes were evaluated: (1) technical success of the IVUS in each bSG, (2) IVUS findings compared with intra-operative angiography, (3) incidence of post-operative computed tomography angiography (CTA) findings not detected with IVUS, and (4) absence of IVUS related adverse events. Target visceral vessel (TVV) instability was defined as any branch or fenestration issues requiring an additional manoeuvre or re-intervention. Any IVUS assessment that detected stenosis, kinking, or any geometric TVV issue was considered to be branch instability. All procedures were performed in ad hoc hybrid rooms. Eighty patients (69% males; median age 72 years; interquartile range 59, 77 years) from four aortic centres treated with F/B-EVAR between January 2019 and September 2021 were included: 70 BEVAR (21 off the shelf; 49 custom made), eight FEVAR (custom made), and two F/B-EVAR (custom made), for a total of 300 potential TVVs. Two TVVs (0.7%) were left unstented and excluded from the analysis. The TVVs could not be accessed with the IVUS catheter in seven cases (2.3%). Furthermore, 17 (5.7%) TVVs could not be examined due to a malfunction of the IVUS catheter. The technical success of the IVUS assessment was 91.9% (274/298), with no IVUS related adverse events. Seven TVVs (2.5%) showed signs of bSG instability by means of IVUS, leading to immediate revisions. The first post-operative CTA at least 30 days after the index procedure was available in 268 of the 274 TVVs originally assessed by IVUS. In seven of the 268 TVVs (2.6%) a re-intervention became necessary due to bSG instability. This study suggests that IVUS is a safe and potentially valuable adjunctive imaging technology for intra-operative detection of TVV instability. Further long term investigations on larger cohorts are required to validate these promising results and to compare IVUS with alternative technologies in terms of efficiency, radiation exposure, procedure time, and costs.

A Novel Dual-Element Catheter for Improving Non-Uniform Rotational Distortion in Intravascular Ultrasound.

For the early diagnosis of atherosclerosis and interventions, intravascular ultrasound (IVUS) is a valuable tool for intravascular luminal imaging. Compared with the array-based method, mechanically rotating IVUS catheters dominate the clinical applications because of their less complexity and better suitability for high-frequency ultrasound imaging. However, mechanically rotating catheters are suffering from non-uniform rotational distortion (NURD) which hinders accurate image acquisition. In this study, a dual-element imaging catheter is proposed, in which two elements with the same frequency and similar performance are assembled in a back-to-back arrangement. When the catheter encounters a NURD due to acute bending, the abnormal image of one element can be replaced by the normal image of the opposite element, thus eliminating the NURD in the reconstructed image. Moreover, two images can be obtained in one rotation and the imaging frame rate is doubled in the absence of NURD. The performance of the two elements was quantitatively assessed by a wire phantom. And the complementary imaging protocols were evaluated by a tissue phantom and ex vivo porcine vessel. The results show that the proposed strategy can be promising in clinical studies.

Intravascular ultrasound imaging for diagnosis and characterization of the popliteal compression syndrome.

Functional popliteal artery entrapment syndrome (fPAES) is a rare form of nonatherosclerotic claudication most often seen in young athletic patients. Diagnosis remains challenging, with various imaging modalities showing equivocal or subtle findings that may be missed. We sought to critically examine and quantitate the utility of intravascular ultrasound (IVUS) imaging, a common diagnostic tool for vascular compression syndromes, in diagnosis and characterization of fPAES. Patients presenting to a single tertiary care center between 2019 and 2022 with symptoms of PAES but without an anatomic etiology or equivocal workup were selected. Angiogram and IVUS with maneuvers were performed on affected extremities at rest, active plantarflexion/dorsiflexion, and plantarflexion/dorsiflexion against resistance. IVUS examination was recorded using a pull-back technique from the tibial vessels to the superficial femoral artery. The degree, length, and anatomic location of compression using the two imaging modalities were compared. Angiogram and IVUS with maneuvers were performed on 17 lower extremities (9 left, 8 right) in 15 patients (88% female; mean age, 21.2years). Evidence of arterial compression on angiography was noted in 88.2% (n= 15) of limbs (66.7% complete contrast cessation and 20% popliteal artery tapering); 13.3% (n= 2) only demonstrated sluggish flow as possible evidence of compression. Arterial compression was seen on IVUS imaging in 15 of 17 limbs, and all completely compressed around the IVUS catheter. The IVUS-measured mean length of compression was 10.5cm± 4.2 (median, 11cm; range, 4-23cm). Compression involved only the popliteal vessels in 86.7% (n= 13); one patient had both popliteal and tibioperoneal trunk compression, whereas another had tibioperoneal trunk and peroneal artery compression. Popliteal vein compression was 100%. The contrast cessation point on angiography and the proximal point of compression on IVUS imaging differed in 80% of cases (P< .05). The distal extent of compression was unable to be determined by angiogram findings but was clearly delineated by IVUS imaging in all cases. IVUS imaging is a more sensitive diagnostic and descriptive imaging modality compared with angiogram in patients with possible fPAES. IVUS and angiogram findings are greatly discordant; moreover, IVUS imaging can provide detailed information such as the precise extent and anatomic location of the arterial compression, which may be useful in aiding surgical planning. IVUS imaging should be considered the gold standard for diagnosing and characterizing fPAES before intervention planning.

Intravascular Ultrasound Guidance in Percutaneous Mechanical Thrombectomy: A Single-Center Experience From the FLASH Registry

BackgroundTraditionally, iodinated contrast is utilized during catheter-based mechanical thrombectomy for pulmonary embolism (PE). Recently, there have been disruptive contrast shortages. Furthermore, contrast can cause contrast-induced acute kidney injury especially in patients with pre-existing chronic kidney disease, necessitating an alternative imaging method. We present utilization and feasibility of an intravascular ultrasound (IVUS)-guided strategy for mechanical thrombectomy in PE from the FLASH registry. MethodsIn this FLASH patient subset, IVUS was used to image the pulmonary arteries (PAs) before and after mechanical thrombectomy with the FlowTriever System at one study site comprising three hospitals. The Philips Visions PV 0.035” IVUS catheter was used for all the IVUS-guided cases in a standardized manner. ResultsBetween July 2019 and December 2021, 26 FLASH patients enrolled at this site underwent IVUS-guided thrombectomy. Most patients (96.2 %) had intermediate-risk PE and 3.8 % had high-risk PE. The mean baseline composite RV/LV ratio was 1.36 ± 0.27 and the mean simplified Pulmonary Embolism Severity Index (sPESI) score was 1.9 ± 1.2. A decreasing trend in contrast agent volume usage was observed over time and several later procedures were performed with IVUS guidance alone. Mean PA pressure significantly decreased immediately following thrombectomy from 34.8 ± 8.3 to 25.5 ± 7.3 mmHg (p < 0.0001). Systolic PA pressure also significantly decreased immediately from 55.4 ± 13.9 to 39.5 ± 12.5 mmHg (p < 0.0001). Significant improvements were seen in echocardiographic assessments of RV function at a mean 87-day follow-up compared with baseline. ConclusionsIn conclusion, the use of IVUS guidance with minimal or no angiographic contrast during mechanical thrombectomy for acute PE is technically feasible.

Impact of the adjunctive use criteria for intravascular ultrasound-guided percutaneous coronary intervention and clinical outcomes

The impact of the adherence to the adjunctive use criteria (AUC) for intravascular ultrasound (IVUS) guided percutaneous coronary intervention (PCI) and clinical outcomes in low IVUS volume countries are limited. The current study compared the procedural success and complication rates between used and not used IVUS catheter in the patients who were met (C +) and were not met (C−) the AUC for IVUS-guided PCI. From June 2018 through June 2019, a total of 21,066 patients were included in the Thai PCI registry. Among the study population, 15,966 patients (75.8%) have met the IVUS-AUC. The IVUS-guided PCI rates were 14.5% and 11.3% in the C + and C − groups, respectively. After adjusting for covariables by propensity model, IVUS-guided PCI was identified as an independent predictor of the procedural success rate regardless of whether the AUC were met with the relative risk [RR (95% confidence interval (CI)] of 1.033(1.026–1.040) and 1.012(1.002–1.021) in C + and C− groups, respectively. IVUS-guided PCI increased the procedural complication risks in both groups but were not significant with corresponding RRs of 1.171(0.915–1.426) and 1.693(0.959–2.426). Procedural success was achieved with IVUS-guided PCI regardless of whether the AUC were met. IVUS-guided PCI did not lead to an increase in procedural complications.

Preliminary study of the significance of reverberation by IVUS detection for patients with severe calcified lesions.

To explore the potential significance of the reverberation of calcification by comparing both intravascular ultrasound (IVUS) and optical coherence tomography (OCT) measurement post manual coregistration. The reverberation phenomenon is often detected by IVUS for severe calcified lesions post rotational atherectomy (RA), which is thought to be due to the glassy and smooth inner surfaces of calcifications. Because of the poor penetration of IVUS, it is impossible to measure the thickness of calcifications, and the relationship between multiple reverberations and the thickness of calcification lesions has not been reported before. A total of forty-nine patients with severe calcified coronary lesions that were detected by IVUS and OCT simultaneously were enrolled in our retrospective study. If reverberation phenomena were detected by IVUS, intravascular imaging (IVI) data (including distance between the IVUS catheter center and the inner surface of the reverberation signal, the intervals between all adjacent reverberation signals, the number of layers of reverberation in IVUS, and the thickness of the calcification in OCT) were measured at the same position and same direction (each cross-section had 4 mutually perpendicular directions) at 1-mm intervals. The correlation between each reverberation observational value and OCT data was the primary target in this retrospective study, and the correlation between reverberation and calcium crack post predilatation was analyzed in other 15 patients. Four hundred twenty-eight valid observational points were analyzed simultaneously by IVUS and OCT; among them, 300 points had a single layer of reverberation, 83 had double layers of reverberation and 42 had multiple layers (≥ 3 layers) of reverberation by IVUS detection post-RA. Multivariate logistic regression analysis showed that the number of layers of reverberation by IVUS was significantly related to the thickness of calcifications by OCT at the same point and in the same direction (p < 0.001). Single, double, and multiple layers of reverberation in IVUS correspond to median calcification thicknesses (interquartile ranges (IQRs)) of 0.620mm (0.520-0.720), 0.950mm (0.840-1.040) and 1.185mm (1.068-1.373), respectively, by OCT detection. Another 100 points in other 15 patients with integrated IVUS data pre- and post-predilatation showed that only single layer of reverberation was related to calcium crack (p < 0.001). The number of layers of reverberation signal detected by IVUS is positively correlated with the thickness of calcifications measured by OCT post-RA and single layer of reverberation is correlated to calcium crack post-predilatation.

Intravascular Ultrasonography (IVUS)-A Tool for Imaging the Eustachian Tube?

The Eustachian tube (ET) has a key role in the pathogenesis of otitis media. Until now, there has been a lack of meaningful imaging methods to investigate the ET and its surrounding tissue. The aim of the current study was to investigate the possibilities of imaging the ET using Intravascular Ultrasonography (IVUS). ETs from sheep were scanned ex vivo and in vivo with different IVUS probes. In addition to native ETs, water was also used to improve coupling. Scans were subsequently compared with histological sections and a 3D model of the ET. In addition, ETs with a stenosis induced by a hyaluronic acid depot, after stent insertion, and during lower jaw movement were examined. The IVUS catheter was inserted into the ET lumen without any problems or injuries in all cases. The surrounding structures of the ET were identified in the ultrasound image. In addition, a change in size of the ET lumen due to movement was observed, and the position of the stent and the depot of hyaluronic acid could be examined. With the use of IVUS, a non-invasive possibility to examine the ET over its course with the adjacent structures as well as after different treatments is presented.

The Importance of Early Thrombus Removal

Historically, anticoagulation has been the primary treatment for acute lower extremity deep venous thrombosis (DVT) with or without thrombolysis. Despite large amounts of clinical research data supporting an ‘open vein hypothesis’, which favours early thrombus removal, clinicians have been hesitant to take this option due to a historically high risk of major bleeding and a few notable studies that failed to show any meaningful benefit. The ATTRACT trial failed to show the benefit of using pharmacomechanical catheter-directed thrombolysis (PCDT) for iliofemoral and femoropopliteal DVT but did result in more bleeding. However, the CaVent study before it revealed a significant reduction in post-thrombotic syndrome (PTS) for patients with iliofemoral and femoral DVT after long-term follow-up past 24 months that grew over time. Since these trials, there have been significant advancements in magnetic resonance and CT venography, intravascular ultrasound (IVUS), venous stenting and thrombectomy catheters meaning there is little to no need for adjunct thrombolytics. Results from ongoing research such as CLEAR-DVT reflect the advances in modern technology.

Role of Intravascular Ultrasound for In Situ Sizing and Technical Assessment of Directional Branches During Branched Endovascular Aortic Repair

To compare intraoperative and early outcomes of branched endovascular aortic repair (BEVAR) of thoracoabdominal aortic aneurysms with or without the use of intravascular ultrasound (IVUS). We conducted a single-center retrospective study of consecutive patients treated for thoracoabdominal aortic aneurysms with branched devices (2019-2021). Two groups were compared. In standard BEVAR (s-BEVAR), sizing was based exclusively on the preoperative computed tomography angiogram, and the technical assessment consisted of intraoperative angiography. From 2020 (iv-BEVAR), IVUS (Philips platform with 0.035-in. Volcano IVUS catheter) was routinely used for in situ sizing of the bridging stent (diameter and length of the distal landing zone, total bridging stent length) and for technical assessment of the bridging stent after deployment (kink, compression, malapposition, or inadequate sealing). s-BEVAR and iv-BEVAR patients were compared in terms of procedural metrics (duration of surgery, radiation dose, radiation time, and contrast volume), technical success (successful introduction and deployment of the device and bridging stents, in the absence of surgical conversion or mortality, type I or III endoleak, branch occlusion, or graft limb obstruction), and 30-day outcomes. There were 59 target vessels (n = 15 patients) in the s-BEVAR group and 56 (n = 15 patients) in the iv-BEVAR group. Aneurysm anatomic classification was similar (extent I-III, 73% vs 67%; extent IV, 27% vs 33%; P = .999). Comparing s-BEVAR vs iv-BEVAR, the total operating time (280 ± 62 minutes vs 293 ± 84 minutes; P = .073) and contrast volume (168 ± 42 mL vs 153 ± 38 mL; P = .312) were similar, although iv-BEVAR had a lower radiation time (119 ± 35 minutes vs 92 ± 42 minutes; P = .042) and dose (745 ± 75 Gy vs 635 ± 85 Gy; P = .010). The use of IVUS identified a significant branch technical defect in 8 of 56 target vessels (14%) not identified by standard angiography; bridging stent compression in five cases and incomplete stent-to-wall apposition in three. These were all intraoperatively corrected with success. Technical success was 100% for both groups, and there were no postoperative deaths and no IVUS-related complications. At 30 days, there were no complications related to the main endograft or directional branches. The use of IVUS for in situ sizing and technical assessment of BEVAR was safe and allowed for reduced radiation time and exposure during BEVAR, maintaining a similar operating time. Compared with sole angiography, the intraoperative use of IVUS led to adjunctive intraoperative maneuvers in a non-negligible portion of target vessels. Further studies are needed to evaluate the clinical role of IVUS in BEVAR.

The principles of ultra-low contrast percutaneous coronary intervention

Ultra-low contrast percutaneous coronary intervention (ULCPCI) can be performed electively in advanced chronic kidney disease. Engage guide catheter and advance guidewire into the coronary artery without using contrast. IVUS-guided PCI can reduce the contrast load. Perform co-registration of distal and proximal radio-opaque marker bands of intravascular ultrasound (IVUS) catheter. Deploy the stent at the target lesion under fluoroscopic guidance of these co-registered position of the IVUS-marking images. Complete the ULCPCI procedure with a final angiography using minimal contrast. Newer contrast sparing techniques and intravascular imaging technologies provide opportunities to perform ULCPCI efficiently with good results and the least complications.

Prediction of medial damage by rotational atherectomy using intravascular ultrasound.

This study evaluated whether intravascular ultrasound (IVUS) images before rotational atherectomy (RA) can predict medial injury caused by RA burr passage in advance. Thirty-three patients with de-novo lesions located in the left anterior descending coronary artery (LAD) who underwent IVUS before and immediately after RA were enrolled. The spatial axes of the two matched pre- and post-RA IVUS cross-sectional images were merged. The segment was considered to have medial damage when the continuity of the intimal layer was disrupted and the medial layer was in direct contact with the lumen on post-RA IVUS. Medial injuries on post-RA IVUS were identified in seven segments of five patients. All segments with medial injury were located near the bifurcation of the LAD and the diagonal branch, and the spatial orientations of the medial injury region were mostly distributed in the lateral side with a diagonal branch take-off. The lumen area was significantly smaller in segments with medial injury than in those without medial injury (P < 0.01). The IVUS catheter was in contact with the healthy side of the arterial wall on pre-RA IVUS images for more than 1 mm in length in all segments with medial injury. When the guidewire and IVUS catheter are close to the healthy side of the arterial wall on pre-RA IVUS images, there is a higher risk of medial injury due to the RA procedure, especially near the bifurcation of the LAD and diagonal branch.

Impact of the Degree of Wire Bias in the Vessel's Healthy Portion on Coronary Perivascular Trauma in Rotational Atherectomy

BackgroundIn rotational atherectomy (RA), the risk of coronary perforation is considered to increase when the wire is in contact with the healthy portion of the vessel. However, the relationship between the extent of wire bias in the healthy portion of the vessel and the risk of coronary perivascular trauma (CPT) has not been reported. MethodsWe examined 90 consecutive cases wherein intravascular ultrasound (IVUS) was performed before and after RA. The IVUS catheter in contact with the healthy region of the vessel was defined as the healthy portion wire bias (HWB), of which we measured the bias diameter, defined as the media-to-media length between the site where the IVUS catheter was in contact and the opposite side of the vessel. The bias ratio was defined as the ratio of the bias diameter to the short diameter at the region where the wire bias was the strongest. The relationship between the bias ratio and the CPT risk was evaluated. ResultsCPT was significantly higher in the HWB group than in the non-HWB group (9% vs. 0%, P = 0.048). In the HWB group, the bias ratio was significantly greater in the CPT group than in the non-CPT group (1.31 ± 0.09 vs. 1.06 ± 0.06; P < 0.0001). The cutoff value of the bias ratio for CPT was 1.2, which was the maximum value of the sum of sensitivity 100% and specificity 97%. ConclusionsLesions without HWB had no CPT. CPT risk increased when the bias ratio exceeded 1.2.

Intravascular ultrasound for peri-procedural geometric orifice area measurement during transcatheter pulmonary valve replacement

Abstract Introduction Large imaging filed intravascular ultrasound (IVUS) offering superior online tomographic perspective and visual accuracy could guide transcatheter pulmonary valve replacement (TPVR) for right ventricular outflow tract (RVOT) insufficiency. It is unknown whether geometric orifice area (GOA) measured by IVUS corresponds with effective orifice area (EOA) measure by transthoracic echocardiography (TTE) after successful TPVR. Purpose To compare minimal inner-leaflets cross-sectional area delineated in systole (min GOA) measured by IVUS versus EOA calculated = right ventricle stroke volume (measured in baseline cardiac magnetic resonance) / pulmonary valve velocity time integral (measured early post-procedure by Vivid e95). Methods After successful TPVR a 10MHz Vision PV 0.035" (60mm imaging field) IVUS catheter was slowly pulled from the distal pulmonary artery to the right ventricle with continuous imaging of RVOT. IVUS measurements included inner-valve dimension for several evenly spaced cross-sections along the entire length and perpendicular to RVOT long axis. Measured were outer-frame diameters (minimal and maximal) and its cross-sectional area, and cross-sectional area of the visual orifice (min GOA) identified exclusively at the coaptation site (Fig 1). Results There were 11 pts (median age 30 [25–36] yrs, 4 ♀, all but one with Tetralogy of Fallot) who had undergone prior corrective surgery (5 transannular patch, 2 bioprosthetic valve or 4 pulmonary homograft). Overall, 176 cross-sections were analyzed. Overall, min GOA measured 3.7±1.0cm2, and was 68%±9% of the valve-outer area (5.5±1.5cm2). It was substantially larger than calculated EOA (3.7±1.0cm2 vs 2.0±0.5cm2; p&amp;lt;0.001). The ratio of max/min GOA diameter was 1.11±0.11 signifying low eccentricity and was not related to EAO. Conclusions After successful balloon-expandable valve implantation to treat RVOT insufficiency, geometric orifice dimension was significantly smaller then outer valve frame dimension. Visual measure of geometric orifice area during the procedure using IVUS documented its circularity and indicated that it was larger than EOA calculated upon functional measure. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): This work was supported by the research grant (2.4/VI/18) founded by the National Institute of Cardiology in Warsaw (Poland). IVUS visualization of ES3.

Clinical decision making in frequently encountered anomalous aortic origin of coronary arteries, the impact of IVUS

Abstract Introduction The aim in the diagnostic work-up of patients with an anomalous aortic origin of coronary arteries (AAOCA) is to determine whether the course of the coronary artery is benign or malignant. In patients with AAOCA with an interarterial course the guidelines on diagnostics are concise. Recommended CT-scan imaging does not evaluate stress-induced functional consequences like external compression by the pulmonary artery as the scan is performed in a resting state. Non-invasive ischemia detection techniques often lack sufficient sensitivity. To improve functional stratification, exploration of new diagnostic modalities in the diagnostic workup of AAOCA is mandatory. Purpose The purpose is to explore the potential role of intravascular ultrasound (IVUS) in the diagnostic workup of patients with AAOCA. Methods Nine patients with an anomalous right coronary artery with an interarterial course were analyzed. A cardiologist evaluated the complaints. Anatomical features of the AAOCA were assessed with CT-scan imaging. Further analyses included ischemia detection and coronary angiography. To assess stress-induced ischemia IVUS and invasive measurements – fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) – were performed at rest and during adrenaline-induced stress. A slit-like orifice was classified as a width/length (W/L) ratio of ≤0.50, an oval orifice as 0.51–0.9 and a round orifice as &amp;gt;0.91. Results Potential cardiac complaints were present in seven patients. In 8 (89%) patients CT-images showed an acute angle, in 8 (89%) proximal narrowing and an aortic take-off above the pulmonary valve in 4 (44%). In 7 (78%) patients a slit-like orifice and in two (22%) an oval orifice were observed (table 1). IVUS at rest showed a slit-like orifice in one patient classified as an oval orifice on the CT-images and vice versa in another patient (table 2). The patients classified as an oval orifice with IVUS showed no external compression during adrenaline-induced stress. In 4 (57%) out of 7 patients with an slit-like orifice on IVUS, the width remained unchanged or increased during adrenaline infusion. In 2 patients the width decreased slightly, however, these patients were asymptomatic and no ischemia was detected. In 1 (14%) patient the width remained 1.4mmm and the length increased from 3.2mm to 4.7mm. In this case the vessel ostium was fully engaged with the IVUS catheter, hence, the width could not decrease during adrenaline infusion. This was regarded as external compression. In addition, in this patient ischemia was detected. Conclusion(s) In two (22%) out of 9 patients IVUS gave a better insight of the shape of the orifice than CT. Additionally, the anatomic and functional-dynamic components of compression could be defined with adrenaline-induced stress. Therefore, IVUS can contribute to a better understanding of the functional consequences of the anatomical features and of potential stress-induced external compression. Funding Acknowledgement Type of funding sources: None. Table 1Table 2

Intravascular ultrasound for valve frame expansion and orifice area measurement as well as paravalvular leak assessment during transcatheter aortic valve replacement

Abstract Introduction Valve frame expansion (measured outer valve frame area/nominal valve dimension), but not oversizing (nominal valve dimension/annulus area, %) determines pattern of restored blood flow after transcatheter aortic valve replacement (TAVR). There is no online measure of frame expansion, and error in current echocardiographic assessment of effective orifice area (EOA) and paravalvular leak (PVL) are common. Purpose To evaluate large imaging field intravascular ultrasound (IVUS) during TAVR for measuring valve geometry [frame expansion, minimal geometric orifice area (min GOA), and mechanism of PVL] with transthoracic echo and angio-CT serving for comparative measures, along with the nominal EOA as established by Hahn et al. Methods After successful TAVR either a 10MHz Vision PV 0.035" (60mm imaging field) or 20MHz Vision PV 0.018" (24mm imaging field plus Chr omaFlo) IVUS catheter (Philips) was slowly pulled from the left ventricle outflow (LVOT) to the aorta with continuous imaging of the aortic root. Results There were 16 pts (80.8±7.1 yrs, 8 female) treated for de novo aortic stenosis (n=15) or failed bioprosthesis (n=1), 7 of whom were treated with balloon-expandable TAVR. PV 0.35" catheters were used in 8 pts (including valve-in-valve) and allowed complete geometry assessment of 26.6±2.7mm nominal prosthesis Ø (Figure 1A) whereas PV 0.018" allowed complete geometry assessment in only 4 of 8 pts with nominal prosthesis Ø of 26.1±2.8mm (Figure 1B). Actual % valve inflow expansion (IVUS outer frame/valve nominal dimension) was significantly smaller than % valve oversizing (80%±19% vs 125±19%, p=0.005). Min GOA was substantially bigger than corresponding nominal EOA and EOA calculated using the post-procedural LVOT diameter (272±84mm2 vs 174±25mm2 vs 181±59mm2, p=0.001 correspondingly). However, min GOA was similar to EOA calculated using baseline LVOT area (272±84mm2 vs 230±90mm2; r=0.713, p=0.009). IVUS and angio-CT measurements of outer prosthesis frame area were similar for inflow, coaptation site, and outflow (460±143mm2 vs 454±134mm2 and 455±134mm2 vs 447±114mm2 and 722±174mm2 vs 725±180; p≤0.001 for all paired correlations). Inflow expansion (IVUS outer frame/baseline CT annulus area) tended to be smaller among valves with ≥mild vs no PVL (95±14% vs 107±11%, p=0.156), with clear ChromaFlo signal seen in the space between the aortic annulus wall and outer-valve frame surface (Figure 1C). Conclusions Large imaging field IVUS during TAVR allows for peri-procedural assessment of actual valve geometry that differs substantially from nominal. IVUS offers online tomographic perspective and highest accuracy in anatomy evaluation corresponding with valve function. Funding Acknowledgement Type of funding sources: None. Figure 1

High frequency focal transducer with a Fresnel zone plate for intravascular ultrasound

The diameter of an intravascular ultrasound (IVUS) catheter is always less than 1 mm, because it must be inserted into a blood vessel to obtain ultrasound images. Owing to this requisite small size, it is difficult to perform geometric focusing on the surface of an IVUS transducer to improve the spatial resolution of the image. This study proposes a high frequency transducer with a Fresnel zone plate (FZP) for intravascular ultrasound imaging. Through theoretical calculations, the parameters and structure of the transducer are optimized for high-frequency ultrasound. The acoustic beam is simulated using COMSOL software. The aperture size of the ultrasound element is 0.778 × 0.9 mm2. Transducers with or without the FZP layer are designed and fabricated in this study. The center frequency and –6 dB bandwidth of the FZP transducer are 52.5 MHz and 42%, respectively. Meanwhile, the center frequency and –6 dB bandwidth of the plane-shape transducer are 51.3 MHz and 58%, respectively. Wire phantom and porcine artery imaging experiments were performed to evaluate the performance of the designed transducers. The spatial resolution of the FZP transducer is 46.8 μm axially and 183.6 μm laterally, and the resolution of the plane-shape transducer is 44.3 μm axially and 313.5 μm laterally. The results demonstrate that the FZP transducer provides superior lateral imaging resolution for IVUS applications.