Interventional cardiovascular magnetic resonance: state-of-the-art

Transcatheter cardiovascular interventions increasingly rely on advanced imaging. X-ray fluoroscopy provides excellent visualization of catheters and devices, but poor visualization of anatomy. In contrast, magnetic resonance imaging (MRI) provides excellent visualization of anatomy and can generate real-time imaging with frame rates similar to X-ray fluoroscopy. Realization of MRI as a primary imaging modality for cardiovascular interventions has been slow, largely because existing guidewires, catheters and other devices create imaging artifacts and can heat dangerously. Nonetheless, numerous clinical centers have started interventional cardiovascular magnetic resonance (iCMR) programs for invasive hemodynamic studies or electrophysiology procedures to leverage the clear advantages of MRI tissue characterization, to quantify cardiac chamber function and flow, and to avoid ionizing radiation exposure. Clinical implementation of more complex cardiovascular interventions has been challenging because catheters and other tools require re-engineering for safety and conspicuity in the iCMR environment. However, recent innovations in scanner and interventional device technology, in particular availability of high performance low-field MRI scanners could be the inflection point, enabling a new generation of iCMR procedures. In this review we review these technical considerations, summarize contemporary clinical iCMR experience, and consider potential future applications.

Aortopulmonary collaterals: An etiology for pediatric tracheostomy hemorrhage

OBJECTIVE

To report a single-institution's experience of symptomatic aortopulmonary collaterals presenting as tracheostomy tube hemorrhage.

STUDY DESIGN

Retrospective case series and Contemporary Review.

SETTING

Tertiary care children's hospital.

METHODS

Retrospective review, from 2015 to 2020, of patients <18 years old who were treated for tracheostomy hemorrhage with endovascular embolization of aortopulmonary collateral (APC) vessels.

RESULTS

4 patients were identified, 2 males and 2 females, ages 15 months-to 14 years-old, with a range of cyanotic congenital heart diseases. Direct laryngoscopy and bronchoscopy were necessary for excluding proximal airway sources. Chest computed tomography angiography did not localize pulmonary hemorrhage, but helped identify aortopulmonary collaterals. Cardiac catheterization was both diagnostic and therapeutic with use of endovascular embolization techniques by pediatric interventional cardiology and interventional radiology. Previously reported APC-related pulmonary hemorrhages occurred in significantly different settings compared to our patients, and evaluation by an otolaryngologist was key to rule out upper airway etiologies.

CONCLUSION

Symptomatic aortopulmonary collaterals is an important etiology in pediatric tracheostomy tube hemorrhage in patients with cyanotic congenital heart disease.

Neonatal Myocardial Infarction: A Proposed Algorithm for Coronary Arterial Thrombus Management

BACKGROUND

Neonatal myocardial infarction is rare and is associated with a high mortality of 40% to 50%. We report our experience with neonatal myocardial infarction, including presentation, management, outcomes, and our current patient management algorithm.

METHODS

We reviewed all infants admitted with a diagnosis of coronary artery thrombosis, coronary ischemia, or myocardial infarction between January 2015 and May 2021.

RESULTS

We identified 21 patients (median age, 1 [interquartile range (IQR), 0.25-9.00] day; weight, 3.2 [IQR, 2.9-3.7] kg). Presentation included respiratory distress (16), shock (3), and murmur (2). Regional wall motion abnormalities by echocardiogram were a key criterion for diagnosis and were present in all 21 with varying degrees of depressed left ventricular function (severe [8], moderate [6], mild [2], and low normal [5]). Ejection fraction ranged from 20% to 54% (median, 43% [IQR, 34%-51%]). Mitral regurgitation was present in 19 (90%), left atrial dilation in 15 (71%), and pulmonary hypertension in 18 (86%). ECG was abnormal in 19 (90%). Median troponin I was 0.18 (IQR, 0.12-0.56) ng/mL. Median BNP (B-type natriuretic peptide) was 2100 (IQR, 924-2325) pg/mL. Seventeen had documented coronary thrombosis by cardiac catheterization. Seventeen (81%) were treated with intracoronary tPA (tissue-type plasminogen activator) followed by systemic heparin, AT (antithrombin), and intravenous nitroglycerin, and 4 (19%) were treated with systemic heparin, AT, and intravenous nitroglycerin alone. Nineteen of 21 recovered. One died (also had infradiaphragmatic total anomalous pulmonary venous return). One patient required a ventricular assist device and later underwent heart transplant; this patient was diagnosed late at 5 weeks of age and did not respond to tPA. Nineteen of 21 (90%) regained normal left ventricular function (ejection fraction, 60%-74%; mean, 65% [IQR, 61%-67%]) at latest follow-up (median, 6.8 [IQR, 3.58-14.72] months). Two of 21 (10%) had residual trivial mitral regurgitation. After analysis of these results, we present our current algorithm, which developed and matured over time, to manage neonatal myocardial infarction.

CONCLUSIONS

We experienced a lower mortality rate for infants with neonatal infarction than that reported in the literature. We propose a post hoc algorithm that may lead to improvement in patient outcomes following coronary artery thrombus.

MRI-Guided Cardiac Catheterization in Congenital Heart Disease: How to Get Started

PURPOSE OF REVIEW

Cardiac magnetic resonance imaging provides radiation-free, 3-dimensional soft tissue visualization with adjunct hemodynamic data, making it a promising candidate for image-guided transcatheter interventions. This review focuses on the benefits and background of real-time magnetic resonance imaging (MRI)-guided cardiac catheterization, guidance on starting a clinical program, and recent research developments.

RECENT FINDINGS

Interventional cardiac magnetic resonance (iCMR) has an established track record with the first entirely MRI-guided cardiac catheterization for congenital heart disease reported nearly 20 years ago. Since then, many centers have embarked upon clinical iCMR programs primarily performing diagnostic MRI-guided cardiac catheterization. There have also been limited reports of successful real-time MRI-guided transcatheter interventions. Growing experience in performing cardiac catheterization in the magnetic resonance environment has facilitated practical workflows appropriate for efficiency-focused cardiac catheterization laboratories. Most exciting developments in imaging technology, MRI-compatible equipment and MRI-guided novel transcatheter interventions have been limited to preclinical research. Many of these research developments are ready for clinical translation. With increasing iCMR clinical experience and translation of preclinical research innovations, the time to make the leap to radiation-free procedures is now.

Institutional Trend in Device Selection for Transcatheter PDA Closure in Premature Infants

We report our experience with transcatheter patent ductus arteriosus (PDA) closure in premature infants and compare patients grouped by the device used for closure: the Microvascular Plug, "MVP" (Medtronic, Minneapolis, MN); Micro Plug Set, "Micro Plug" (KA Medical, Minneapolis, MN); and Amplatzer Piccolo Occluder, "Piccolo" (Abbot, Santa Clara, CA). We also report trends in device selection over time. Studies examining outcomes according to device selection for PDA closure in premature infants are lacking. We performed a retrospective review of all percutaneous PDA closures in premature infants at a single center (June 2018-May 2021). Patients were grouped by initial device selected for PDA closure (intention to treat). Institutional Review Board approval was obtained. 58 premature infants [MVP (n = 25), Micro Plug (n = 25), and Piccolo (n = 8)] underwent successful transcatheter PDA closure (mean gestational age 27 weeks 2 days; mean weight at procedure 1.4 kg; mean age at procedure 28 days). Pre-procedural demographics, procedural data, and follow-up data were similar between groups. There were no significant procedural adverse events. Three devices (2 MVP, 0 Micro Plug, 1 Piccolo p = 0.27) embolized after the procedure. One other device was removed for concern for aortic obstruction. Device selection evolved with a clear trend toward the Micro Plug device over time. Demographic, procedural, and follow-up data were similar between the MVP, Micro Plug, and Piccolo groups. The Micro Plug did not require exchange for suboptimal fitting or embolize and became our preferred device in most cases.

Expanded Use of the One-Step Technique for Simultaneous Landing Zone Stenting and Placement of the Melody Transcatheter Pulmonary Valve

OBJECTIVES

We report a multicenter experience with simultaneous right ventricular outflow tract (RVOT) stenting and transcatheter pulmonary valve implantation using the Melody valve (Medtronic).

BACKGROUND

Prestenting the RVOT before Melody valve implantation is now the standard of care. Prestenting is usually performed as a separate step. The "one-step" technique for simultaneous landing zone stenting and Melody delivery was previously reported using only Max LD stents (Medtronic). We report a multicenter experience of simultaneous stenting and Melody implantation using multiple stent types in combination.

METHODS

This retrospective cohort study includes 33 patients from 3 centers who underwent simultaneous stenting and Melody valve implantation between 2017 and 2020. Key variables were compared with 31 patients from the same centers who underwent standard (non-simultaneous) prestenting followed by Melody implantation during the same time frame.

RESULTS

The 2 groups were similar in terms of age, weight, sex, and total procedure time. The 2 groups had similar clinical results and safety profiles, with no difference between the postimplantation right ventricle (RV) to pulmonary artery systolic pressure gradient, RV to aortic pressure ratio, and complication rate. The simultaneous group had lower radiation exposure as measured by dose area product. Up to 3 stents were safely placed simultaneously with a Melody valve.

CONCLUSIONS

Simultaneous RVOT stenting and Melody valve implantation can safely be used to place up to 3 stents outside a Melody valve. This approach can simplify the catheterization procedure and potentially reduce radiation dose.

Intravascular Ultrasound (IVUS) Provides the Filling for the Angiogram's Crust: Benefits of IVUS in Pediatric Interventional Cardiology

BACKGROUND

Intravascular ultrasound (IVUS) is a catheter-based imaging modality that generates cross-sectional views of vessel walls and lumens. This technique is used in adult interventional and vascular surgeries to guide the management of coronary artery and peripheral arterial disease. IVUS has been described as superior to angiography in providing data about lesions of interest, including degree of vessel stenosis and stent apposition following intervention. IVUS use to guide transcatheter management of congenital heart disease is limited.

OBJECTIVE

We reviewed our experience using IVUS as an adjunctive tool to diagnose lesions and assess intervention in pediatric patients during cardiac catheterization.

METHODS AND RESULTS

A retrospective chart review of all pediatric patients who underwent IVUS during cardiac catheterization to evaluate the cross-sectional lumen of non-coronary vessel(s) at Rady Children's Hospital from January 2018 to December 2019 was performed. Median patient age was 637 days (range, 44-4328 days), with mean weight of 12.1 ± 9 kg. Twenty-six vessels were interrogated with IVUS (pulmonary venous stenosis [n = 8], coarctation [n = 5], branch pulmonary artery stenosis [n = 6], systemic shunts and conduits [n = 3], and other peripheral vasculature [n = 4]). IVUS added value in all cases (100%). We found that IVUS guided the intervention in 88% of procedures and defined the endpoint in 62% of transcatheter interventions. There were no IVUS-related complications.

CONCLUSIONS

IVUS enhanced our diagnostic interpretation and identified occult lesions not visualized by angiography. IVUS was valuable in guiding and defining the endpoints of these interventions.

Patent Ductus Arteriosus Stenting for All Ductal-Dependent Cyanotic Infants: Waning Use of Blalock-Taussig Shunts

[Figure: see text].

An Anterior Anastomosis for the Modified Fontan Connection: A Hemodynamic Analysis

This hemodynamic feasibility study examined total cavopulmonary connection (TCPC) designs connecting the extracardiac conduit to the anterior surface of pulmonary arteries (PAs) or superior vena cava (SVC) rather than to the inferior PA surface (traditional TCPC). The study involved twenty-five consecutive Fontan patients meeting inclusion criteria from a single institution. A virtual surgical platform mimicked the completed traditional TCPC and generated three anterior anastomosis designs: Anterior-PA, Middle-SVC, and SVC-Inn (Inn: innominate vein). Hemodynamic performance of anterior anastomosis designs was compared with the traditional TCPC regarding indexed power loss (iPL) and hepatic flow distribution (HFD). Compared to the traditional TCPC, the Anterior-PA design produces a similar iPL. The Middle-SVC design is also similar, though the iPL difference is positively correlated with the anastomosing height. The SVC-Inn design had significantly more iPL. The three anterior anastomosis designs did not have a significant difference in HFD (from traditional TCPC). Pulmonary flow distribution (PFD) has a stronger correlation with HFD from the anterior anastomosis designs than the traditional TCPC. This hemodynamic feasibility study examined anterior anastomosis, extracardiac TCPC designs that may offer surgeons clinical dexterity. The Anterior-PA design may be equivalent to the traditional TCPC. Fontan extracardiac conduit anastomosis just superior to the PAs (Middle-SVC) also preserves hemodynamic performance and avoids direct PA anastomosis. These designs could simplify surgical Fontan completion, and may particularly benefit patients requiring surgical dissection, having atypical PA orientation, or after PA stent angioplasty.

Advances in Transcatheter Electrosurgery for Treating Valvular Heart Disease

Delivery of electrosurgery energy through catheters and guidewires enables interventionists to ‘cut’ through obstructive intravascular lesions or across cardiac chambers. A novel application of transcatheter electrosurgery is to make controlled lacerations in heart valve leaflets. This review describes three applications of transcatheter electrosurgery of aortic and mitral valve leaflets to enable transcatheter heart valve implantation. Intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow obstruction splits and splays the anterior mitral valve and enables transcatheter mitral valve replacement without left ventricular outflow tract obstruction. Technique modifications and novel applications are described. Bioprosthetic or native aortic scallop intentional laceration to prevent iatrogenic coronary artery obstruction enables transcatheter aortic valve replacement without coronary artery obstruction. The technique is described and novel uses, especially in the setting of repeat transcatheter aortic valve replacement, are discussed. Finally, electrosurgical laceration and stabilization of mitral valve clip devices (ELASTA-Clip) enables transcatheter mitral valve replacement after MitraClip implantation. In conclusion, transcatheter electrosurgery is an important and versatile new tool in structural heart intervention.

Purpose-built transcatheter cavopulmonary anastomosis device requirements: Multi-modality imaging evaluation

BACKGROUND/PURPOSE

Patients with a functional single ventricle undergo multiple, palliative open-heart surgeries. This includes a superior cavopulmonary anastomosis or bidirectional Glenn shunt. A less-invasive transcatheter approach may reduce morbidity.

METHODS/MATERIALS

We analyzed pre-Glenn X-ray contrast angiography (XA), cardiac computed tomography (CT), and cardiac magnetic resonance (CMR) studies.

RESULTS

Over an eleven-year period (1/2007 - 6/2017), 139 Glenn surgeries were performed at our institution. The typical age range at surgery was 59 - 371 days (median = 163; IQR = 138 - 203). Eight-nine XA, ten CT, and ten CMR studies obtained from these patients were analyzed. Cephalad SVC measurements (millimeters) were 7.3 ± 1.7 (XA), 7.7 ± 1.6 (CT) and 6.9 ± 1.8 (CMR). RPA measurements were 7.3 ± 1.9 (XA), 7.4 ± 1.6 (CT) and 6.6 ± 1.9 (CMR). Potential device lengths were 10.9 ± 6 - 17.4 ± 6.4 (XA), 10.1 ± 2.1 - 17.7 ± 2.4 (CT) and 17.3 ± 4. - 23.7 ± 5.5 (CMR). SVC-RPA angle (degrees) was 132.9 ± 13.2 (CT) and 140 ± 10.2 (MRI). Image quality of all CT (100%), almost all XA (SVC 100%, RPA 99%), and most MRI (SVC 80%, RPA 90%) were deemed sufficient. Parametric modeling virtual fit device with 10 mm diameter and 20 - 25 mm length was ideal.

CONCLUSIONS

Ideal transcatheter cavopulmonary shunt device for the typical patient would be 10 mm in diameter and 20-25 mm in length.

Serial Dilation of Low-Profile Stents Delivered in the Aorta and Pulmonary Arteries in Pediatric Patients Leads to Spontaneous Fractures but Not to Adverse Events

OBJECTIVES

Low-profile stents placed in pediatric patients with congenital heart disease must be expanded by balloon angioplasty to accommodate patient growth. During the process of serial dilation, some stents may spontaneously fracture. The incidence and safety profile of spontaneous fracture is unclear. We report the performance characteristics and safety profile of a cohort of low-profile, premounted stents placed in the pulmonary arteries and aorta and then serially dilated over time to accommodate patient growth, including incidence of fracture and any adverse events.

METHODS

A retrospective chart review was conducted of 25 pediatric patients who underwent 27 stent placements with low-profile, premounted stents from January 2005 to September 2018.

RESULTS

Nine stents (33%) sustained a spontaneous fracture. There was no statistically significant association between stent fracture and our variables of interest, ie, patient gender, patient weight at time of original stenting, stent location (aorta vs pulmonary artery), stent type, original diameter of stent, and weight at the time of stent implantation. There was no association between time to spontaneous fracture and the aforementioned variables of interest. The majority of the spontaneous fractures occurred within the first 4 years after stent implantation, and there was no difference in survival between the 3 stent types investigated in our cohort.

CONCLUSION

One-third of stents undergoing serial dilation for patient growth fractured spontaneously. Patients with fractured stents were free from significant adverse events in this cohort.

Early experience with the Micro Plug Set for preterm patent ductus arteriosus closure

OBJECTIVES

We intend to describe early experience using a new, commercially available Micro Plug Set for preterm neonate and infant transcatheter patent ductus arteriosus (PDA) occlusion.

BACKGROUND

Transcatheter PDA occlusion in premature neonates and small infants is safe and effective. The procedure is early in its evolution.

METHODS

Procedural and short-term outcomes of preterm neonates and infants undergoing transcatheter PDA occlusion with a new, commercially available device were reviewed.

RESULTS

Eight preterm neonates and infants born at median 27 weeks gestation (23-36 weeks) underwent transcatheter PDA device closure with the Micro Plug Set. The device is short (2.5 mm) with a range of diameters (3, 4, 5, 6 mm) and delivered through a microcatheter. Procedures were performed at median 41 days of age (12-88 days) and at 1690 g (760-3,310 g). Transvenous PDA device occlusion was performed with fluoroscopic and echocardiography guidance. All procedures were successful with complete PDA occlusion. There were no procedural or short-term adverse events.

CONCLUSIONS

Preterm neonate and infant transcatheter PDA device closure with a new, commercially available short and microcatheter delivered device (Micro Plug Set) was safe and effective in a small, early series of patients.

Alternative Access in Congenital Heart Disease

Limited arterial vascular access precluded necessary transcatheter intervention in a 22-year-old woman with repaired interrupted aortic arch type B. Alternative transcaval vascular access enabled percutaneous therapy. This practice evolution is likely to benefit the growing numbers of adults with congenital heart disease. (Level of Difficulty: Advanced.)

Aortic Root Thrombosis on ECMO-A Novel Management Strategy

A 15-year-old presented in cardiogenic shock secondary to viral myocarditis requiring venoarterial extracorporeal membrane oxygenation (ECMO) support. He developed large thrombi of the left ventricle and aortic root. Anticoagulation was increased, and medications were initiated to decrease the likelihood of aortic valve opening. He underwent balloon atrial septostomy followed by placement of a left atrial vent. A pigtail catheter was placed in the ascending aorta for direct heparin infusion. Serial echocardiograms showed progressive resolution of the thrombi. He was successfully weaned from ECMO and discharged home without neurological deficits.

Transcatheter Electrosurgery: JACC State-of-the-Art Review

Transcatheter electrosurgery refers to a family of procedures using radiofrequency energy to vaporize and traverse or lacerate tissue despite flowing blood. The authors review theory, simulations, and benchtop demonstrations of how guidewires, insulation, adjunctive catheters, and dielectric medium interact. For tissue traversal, all but the tip of traversing guidewires is insulated to concentrate current. For leaflet laceration, the "Flying V" configuration concentrates current at the inner lacerating surface of a kinked guidewire. Flooding the field with non-ionic dextrose eliminates alternative current paths. Clinical applications include traversing occlusions (pulmonary atresia, arterial and venous occlusion, and iatrogenic graft occlusion), traversing tissue planes (atrial and ventricular septal puncture, radiofrequency valve repair, transcaval access, Potts and Glenn shunts), and leaflet laceration (BASILICA, LAMPOON, ELASTA-Clip, and others). Tips are provided for optimizing these techniques. Transcatheter electrosurgery already enables a range of novel therapeutic procedures for structural heart disease, and represents a promising advance toward transcatheter surgery.

An Elusive Prize: Transcutaneous Near InfraRed Spectroscopy (NIRS) Monitoring of the Liver

Introduction: We postulate a relationship between a transcutaneous hepatic NIRS measurement and a directly obtained hepatic vein saturation. If true, hepatic NIRS monitoring (in conjunction with the current dual-site cerebral-renal NIRS paradigm) might increase the sensitivity for detecting shock since regional oxygen delivery changes in the splanchnic circulation before the kidney or brain. We explored a reliable technique for hepatic NIRS monitoring as a prelude to rigorously testing this hypothesis. This proof-of-concept study aimed to validate hepatic NIRS monitoring by comparing hepatic NIRS measurements to direct hepatic vein samples obtained during cardiac catheterization. Method: IRB-approved prospective pilot study of hepatic NIRS monitoring involving 10 patients without liver disease who were already undergoing elective cardiac catheterization. We placed a NIRS monitor on the skin overlying liver during catheterization. Direct measurement of hepatic vein oxygen saturation during the case compared with simultaneous hepatic NIRS measurement. Results: There was no correlation between the Hepatic NIRS values and the directly measured hepatic vein saturation (R = -0.035; P = 0.9238). However, the Hepatic NIRS values correlated with the cardiac output (R = 0.808; P = 0.0047), the systolic arterial blood pressure (R = 0.739; P = 0.0146), and the diastolic arterial blood pressure (R = 0.7548; P = 0.0116). Conclusions: Using the technique described, hepatic NIRS does not correlate well with the hepatic vein saturation. Further optimization of the technique might provide a better measurement. Hepatic NIRS does correlate with cardiac output and thus may still provide a valuable additional piece of hemodynamic information when combined with other non-invasive monitoring.

X-ray fused with MRI guidance of pre-selected transcatheter congenital heart disease interventions

OBJECTIVES

To determine whether X-ray fused with MRI (XFM) is beneficial for select transcatheter congenital heart disease interventions.

BACKGROUND

Complex transcatheter interventions often require three-dimensional (3D) soft tissue imaging guidance. Fusion imaging with live X-ray fluoroscopy can potentially improve and simplify procedures.

METHODS

Patients referred for select congenital heart disease interventions were prospectively enrolled. Cardiac MRI data was overlaid on live fluoroscopy for procedural guidance. Likert scale operator assessments of value were recorded. Fluoroscopy time, radiation exposure, contrast dose, and procedure time were compared to matched cases from our institutional experience.

RESULTS

Forty-six patients were enrolled. Pre-catheterization, same day cardiac MRI findings indicated intervention should be deferred in nine patients. XFM-guided cardiac catheterization was performed in 37 (median age 8.7 years [0.5-63 years]; median weight 28 kg [5.6-110 kg]) with the following prespecified indications: pulmonary artery (PA) stenosis (n = 13), aortic coarctation (n = 12), conduit stenosis/insufficiency (n = 9), and ventricular septal defect (n = 3). Diagnostic catheterization showed intervention was not indicated in 12 additional cases. XFM-guided intervention was performed in the remaining 25. Fluoroscopy time was shorter for XFM-guided intervention cases compared to matched controls. There was no significant difference in radiation dose area product, contrast volume, or procedure time. Operator Likert scores indicated XFM provided useful soft tissue guidance in all cases and was never misleading.

CONCLUSIONS

XFM provides operators with meaningful three-dimensional soft tissue data and reduces fluoroscopy time in select congenital heart disease interventions.

Hepatic Vein Incorporation Into the Azygos System in Heterotaxy and Interrupted Inferior Vena Cava

Background:

Patients with heterotaxy, single ventricle and interrupted inferior vena cava are at risk of developing significant pulmonary arteriovenous malformations and cyanosis, and inequitable distribution of hepatic factor has been implicated in their development. We describe our experience with a technique for hepatic vein incorporation that reliably provides resolution of cyanosis and presumably equitable hepatic factor distribution.

Methods:

A retrospective review of a single-surgeon experience was conducted for patients who underwent this modified Fontan operation utilizing an extracardiac conduit from the hepatic veins to the dominant superior cavopulmonary connection. Preoperative characteristics and imaging, operative details, and postoperative course and imaging were abstracted.

Results:

Median age at operation was 5 years (2-10 years) and median weight was 19.6 kg (11.8-23 kg). Sixty percent (3/5) of patients had Fontan completion without cardiopulmonary bypass, and follow-up was complete at a median of 14 months (range 1-20 months). Systemic saturations increased significantly from 81% ± 1.9% preoperatively to 95% ± 3.5% postoperatively, P = .0008. Median length of stay was 10 days (range: 7-14 days). No deaths occurred. One patient required reoperation for bleeding and one was readmitted for pleural effusion. Postoperative imaging suggested distribution of hepatic factor to all lung segments with improved pulmonary arteriovenous malformation burden.

Conclusions:

Hepatic vein incorporation for patients with heterotaxy and interrupted inferior vena cava should optimally provide equitable pulmonary distribution of hepatic factor with resolution of cyanosis. The described technique is performed through a conventional approach, is facile, and improves cyanosis in these complex patients.

Pulmonary artery interventions after the arterial switch operation: Unique and significant risks

BACKGROUND

In the modern era, results of the arterial switch operation (ASO) for transposition of the great arteries are excellent. However, because of the LeCompte maneuver, there may be a propensity for development of pulmonary artery stenosis. We encountered atypical complications of pulmonary artery stenting in patients after the ASO, including aorto-pulmonary fistula and coronary compression.

METHODS

We performed a 10-year retrospective review of catheterizations performed in patients after ASO in our institution with a focus on adverse events.

RESULTS

Diagnostic and interventional catheterizations were performed in 47 patients. In 29 patients, 37 interventional procedures performed, which included pulmonary artery angioplasty and/or stenting. In this group, there were five major adverse events (14%), including three aorto-pulmonary fistulae and one coronary artery compression among patients having stent implantation or stent redilation. In addition, there were 6/37 (16%) intended stent procedures, which were aborted because there appeared to be high-risk of significant adverse events.

CONCLUSIONS

This review suggests that percutaneous intervention on pulmonary artery stenosis after ASO has high-risk and should be undertaken advisedly. Prior thorough evaluation of coronary arteries is mandatory as coronary reimplantation sites may be adjacent to sites of pulmonary artery stenosis. Furthermore, if pulmonary artery stent implantation or stent redilation is contemplated, the risk of stent fracture and possible AP fistula should be recognized. Primary use of reinforced covered stents should be considered.

Endograft rescue of compromised interposition aortic graft in an adult patient with congenital heart disease

In a 19-year-old male with interrupted aortic arch and complex congenital heart disease, we report percutaneous repair of a compromised aortic conduit. The patient had aortic arch repair in childhood utilizing a 12 mm Hemashield Dacron conduit. CT angiography showed multiple segments of this conduit were dilated to 16 mm suggesting conduit degeneration and failure with pseudoaneurysm formation. We utilized a self-expanding aortic endograft supported by internal placement of bare metal stents to repair the conduit. Our repair was guided by 3D rotational angiography. This adult patient with complex congenital heart disease and interrupted aortic arch is an example of patients in whom endograft repair of compromised aortic conduits presents a much lower risk alternative than surgical revision.

Physiological Recording in the MRI Environment (PRiME): MRI-Compatible Hemodynamic Recording System

Hemodynamic recording during interventional cardiovascular procedures is essential for procedural guidance, monitoring patient status, and collection of diagnostic information. Recent advances have made interventions guided by magnetic resonance imaging (MRI) possible and attractive in certain clinical scenarios. However, in the MRI environment, electromagnetic interference (EMI) can cause severe distortions and artifacts in acquired hemodynamic waveforms. The primary aim of this paper was to develop and validate a system to minimize EMI on electrocardiogram (ECG) and invasive blood pressure (IBP) signals. A system was developed which incorporated commercial MRI compatible ECG leads and pressure transducers, custom electronics, user interface, and adaptive signal processing. Measurements were made on pediatric patients (N = 6) during MRI-guided catheterization. Real-time interactive scanning, which is known to produce significant EMI due to fast gradient switching and varying imaging plane orientations, was selected for testing. The effectiveness of the adaptive algorithms was determined by measuring the reduction of noise peaks, amplitude of noise peaks, and false QRS triggers. During real-time gradient-intensive imaging sequences, peak noise amplitude was reduced by 80% and false QRS triggers were reduced to a median of 0. There was no detectable interference on the IBP channels. A hemodynamic recording system front-end was successfully developed and deployed, which enabled high-fidelity recording of ECG and IBP during MRI scanning. The schematics and assembly instructions are publicly available to facilitate implementation at other institutions. Researchers and clinicians are provided a critical tool in investigating and implementing MRI guided interventional cardiovascular procedures.

An MR-Based Model for Cardio-Respiratory Motion Compensation of Overlays in X-Ray Fluoroscopy

In X-ray fluoroscopy, static overlays are used to visualize soft tissue. We propose a system for cardiac and respiratory motion compensation of these overlays. It consists of a 3-D motion model created from real-time magnetic resonance (MR) imaging. Multiple sagittal slices are acquired and retrospectively stacked to consistent 3-D volumes. Slice stacking considers cardiac information derived from the ECG and respiratory information extracted from the images. Additionally, temporal smoothness of the stacking is enhanced. Motion is estimated from the MR volumes using deformable 3-D/3-D registration. The motion model itself is a linear direct correspondence model using the same surrogate signals as slice stacking. In X-ray fluoroscopy, only the surrogate signals need to be extracted to apply the motion model and animate the overlay in real time. For evaluation, points are manually annotated in oblique MR slices and in contrast-enhanced X-ray images. The 2-D Euclidean distance of these points is reduced from 3.85 to 2.75 mm in MR and from 3.0 to 1.8 mm in X-ray compared with the static baseline. Furthermore, the motion-compensated overlays are shown qualitatively as images and videos.

Radiation-free CMR diagnostic heart catheterization in children

BACKGROUND

Children with heart disease may require repeated X-Ray cardiac catheterization procedures, are more radiosensitive, and more likely to survive to experience oncologic risks of medical radiation. Cardiovascular magnetic resonance (CMR) is radiation-free and offers information about structure, function, and perfusion but not hemodynamics. We intend to perform complete radiation-free diagnostic right heart catheterization entirely using CMR fluoroscopy guidance in an unselected cohort of pediatric patients; we report the feasibility and safety.

METHODS

We performed 50 CMR fluoroscopy guided comprehensive transfemoral right heart catheterizations in 39 pediatric (12.7 ± 4.7 years) subjects referred for clinically indicated cardiac catheterization. CMR guided catheterizations were assessed by completion (success/failure), procedure time, and safety events (catheterization, anesthesia). Pre and post CMR body temperature was recorded. Concurrent invasive hemodynamic and diagnostic CMR data were collected.

RESULTS

During a twenty-two month period (3/2015 - 12/2016), enrolled subjects had the following clinical indications: post-heart transplant 33%, shunt 28%, pulmonary hypertension 18%, cardiomyopathy 15%, valvular heart disease 3%, and other 3%. Radiation-free CMR guided right heart catheterization attempts were all successful using passive catheters. In two subjects with septal defects, right and left heart catheterization were performed. There were no complications. One subject had six such procedures. Most subjects (51%) had undergone multiple (5.5 ± 5) previous X-Ray cardiac catheterizations. Retained thoracic surgical or transcatheter implants (36%) did not preclude successful CMR fluoroscopy heart catheterization. During the procedure, two subjects were receiving vasopressor infusions at baseline because of poor cardiac function, and in ten procedures, multiple hemodynamic conditions were tested.

CONCLUSIONS

Comprehensive CMR fluoroscopy guided right heart catheterization was feasible and safe in this small cohort of pediatric subjects. This includes subjects with previous metallic implants, those requiring continuous vasopressor medication infusions, and those requiring pharmacologic provocation. Children requiring multiple, serial X-Ray cardiac catheterizations may benefit most from radiation sparing. This is a step toward wholly CMR guided diagnostic (right and left heart) cardiac catheterization and future CMR guided cardiac intervention.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02739087 registered February 17, 2016.

CMR fluoroscopy right heart catheterization for cardiac output and pulmonary vascular resistance: results in 102 patients

BACKGROUND

Quantification of cardiac output and pulmonary vascular resistance (PVR) are critical components of invasive hemodynamic assessment, and can be measured concurrently with pressures using phase contrast CMR flow during real-time CMR guided cardiac catheterization.

METHODS

One hundred two consecutive patients underwent CMR fluoroscopy guided right heart catheterization (RHC) with simultaneous measurement of pressure, cardiac output and pulmonary vascular resistance using CMR flow and the Fick principle for comparison. Procedural success, catheterization time and adverse events were prospectively collected.

RESULTS

RHC was successfully completed in 97/102 (95.1%) patients without complication. Catheterization time was 20 ± 11 min. In patients with and without pulmonary hypertension, baseline mean pulmonary artery pressure was 39 ± 12 mmHg vs. 18 ± 4 mmHg (p < 0.001), right ventricular (RV) end diastolic volume was 104 ± 64 vs. 74 ± 24 (p = 0.02), and RV end-systolic volume was 49 ± 30 vs. 31 ± 13 (p = 0.004) respectively. 103 paired cardiac output and 99 paired PVR calculations across multiple conditions were analyzed. At baseline, the bias between cardiac output by CMR and Fick was 5.9% with limits of agreement -38.3% and 50.2% with r = 0.81 (p < 0.001). The bias between PVR by CMR and Fick was -0.02 WU.m2 with limits of agreement -2.6 and 2.5 WU.m2 with r = 0.98 (p < 0.001). Correlation coefficients were lower and limits of agreement wider during physiological provocation with inhaled 100% oxygen and 40 ppm nitric oxide.

CONCLUSIONS

CMR fluoroscopy guided cardiac catheterization is safe, with acceptable procedure times and high procedural success rate. Cardiac output and PVR measurements using CMR flow correlated well with the Fick at baseline and are likely more accurate during physiological provocation with supplemental high-concentration inhaled oxygen.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01287026 , registered January 25, 2011.

Acute Cardiac MRI Assessment of Radiofrequency Ablation Lesions for Pediatric Ventricular Arrhythmia: Feasibility and Clinical Correlation

BACKGROUND

Arrhythmia ablation with current techniques is not universally successful. Inadequate ablation lesion formation may be responsible for some arrhythmia recurrences. Periprocedural visualization of ablation lesions may identify inadequate lesions and gaps to guide further ablation and reduce risk of arrhythmia recurrence.

METHODS

This feasibility study assessed acute postprocedure ablation lesions by MRI, and correlated these findings with clinical outcomes. Ten pediatric patients who underwent ventricular tachycardia ablation were transferred immediately postablation to a 1.5T MRI scanner and late gadolinium enhancement (LGE) imaging was performed to characterize ablation lesions. Immediate and mid-term arrhythmia recurrences were assessed.

RESULTS

Patient characteristics include median age 14 years (1-18 years), median weight 52 kg (11-81 kg), normal cardiac anatomy (n = 6), d-transposition of great arteries post arterial switch repair (n = 2), anomalous coronary artery origin post repair (n = 1), and cardiac rhabdomyoma (n = 1). All patients underwent radiofrequency catheter ablation of ventricular arrhythmia with acute procedural success. LGE was identified at the reported ablation site in 9/10 patients, all arrhythmia-free at median 7 months follow-up. LGE was not visible in 1 patient who had recurrence of frequent premature ventricular contractions within 2 hours, confirmed on Holter at 1 and 21 months post procedure.

CONCLUSIONS

Ventricular ablation lesion visibility by MRI in the acute post procedure setting is feasible. Lesions identifiable with MRI may correlate with clinical outcomes. Acute MRI identification of gaps or inadequate lesions may provide the unique temporal opportunity for additional ablation therapy to decrease arrhythmia recurrence.

Transcatheter Myocardial Needle Chemoablation During Real-Time Magnetic Resonance Imaging: A New Approach to Ablation Therapy for Rhythm Disorders

BACKGROUND

Radiofrequency ablation for ventricular arrhythmias is limited by inability to visualize tissue destruction, by reversible conduction block resulting from edema surrounding lesions, and by insufficient lesion depth. We hypothesized that transcatheter needle injection of caustic agents doped with gadolinium contrast under real-time magnetic resonance imaging (MRI) could achieve deep, targeted, and irreversible myocardial ablation, which would be immediately visible.

METHODS AND RESULTS

Under real-time MRI guidance, ethanol or acetic acid was injected into the myocardium of 8 swine using MRI-conspicuous needle catheters. Chemoablation lesions had identical geometry by in vivo and ex vivo MRI and histopathology, both immediately and after 12 (7-17) days. Ethanol caused stellate lesions with patchy areas of normal myocardium, whereas acetic acid caused homogeneous circumscribed lesions of irreversible necrosis. Ischemic cardiomyopathy was created in 10 additional swine by subselective transcoronary ethanol administration into noncontiguous territories. After 12 (8-15) days, real-time MRI-guided chemoablation-with 2 to 5 injections to create a linear lesion-successfully eliminated the isthmus and local abnormal voltage activities.

CONCLUSIONS

Real-time MRI-guided chemoablation with acetic acid enabled the intended arrhythmic substrate, whether deep or superficial, to be visualized immediately and ablated irreversibly. In an animal model of ischemic cardiomyopathy, obliteration of a conductive isthmus both anatomically and functionally and abolition of local abnormal voltage activities in areas of heterogeneous scar were feasible. This represents the first report of MRI-guided myocardial chemoablation, an approach that could improve the efficacy of arrhythmic substrate ablation in the thick ventricular myocardium.

Magnetic Resonance Imaging-Guided Transcatheter Cavopulmonary Shunt

OBJECTIVES

The aim of this study was to test the hypothesis that real-time magnetic resonance imaging (MRI) would enable closed-chest percutaneous cavopulmonary anastomosis and shunt by facilitating needle guidance along a curvilinear trajectory, around critical structures, and between a superior vena cava "donor" vessel and a pulmonary artery "target."

BACKGROUND

Children with single-ventricle physiology require multiple open heart operations for palliation, including sternotomies and cardiopulmonary bypass. The reduced morbidity of a catheter-based approach would be attractive.

METHODS

Fifteen naive swine underwent transcatheter cavopulmonary anastomosis and shunt creation under 1.5-T MRI guidance. An MRI antenna-needle was advanced from the superior vena cava into the target pulmonary artery bifurcation using real-time MRI guidance. In 10 animals, balloon-expanded off-the-shelf endografts secured a proximal end-to-end caval anastomosis and a distal end-to-side pulmonary anastomosis that preserved blood flow to both branch pulmonary arteries. In 5 animals, this was achieved with a novel, purpose-built, self-expanding device.

RESULTS

Real-time MRI needle access of target vessels (pulmonary artery), endograft delivery, and superior vena cava shunt to pulmonary arteries were successful in all animals. All survived the procedure without complications. Intraprocedural real-time MRI, post-procedural MRI, x-ray angiography, computed tomography, and necropsy showed patent shunts with bidirectional pulmonary artery blood flow.

CONCLUSIONS

MRI guidance enabled a complex, closed-chest, beating-heart, pediatric, transcatheter structural heart procedure. In this study, MRI guided trajectory planning and reproducible, reliable bidirectional cavopulmonary shunt creation.

Interventional-Cardiovascular MR: Role of the Interventional MR Technologist

BACKGROUND

Interventional-cardiovascular magnetic resonance (iCMR) is a promising clinical tool for adults and children who need a comprehensive hemodynamic catheterization of the heart. Magnetic resonance (MR) imaging-guided cardiac catheterization offers radiation-free examination with increased soft tissue contrast and unconstrained imaging planes for catheter guidance. The interventional MR technologist plays an important role in the care of patients undergoing such procedures. It is therefore helpful for technologists to understand the unique iCMR preprocedural preparation, procedural and imaging workflows, and management of emergencies. The authors report their team's experience from the National Institutes of Health Clinical Center and a collaborating pediatric site.

Segmented nitinol guidewires with stiffness-matched connectors for cardiovascular magnetic resonance catheterization: preserved mechanical performance and freedom from heating

BACKGROUND

Conventional guidewires are not suitable for use during cardiovascular magnetic resonance (CMR) catheterization. They employ metallic shafts for mechanical performance, but which are conductors subject to radiofrequency (RF) induced heating. To date, non-metallic CMR guidewire designs have provided inadequate mechanical support, trackability, and torquability. We propose a metallic guidewire for CMR that is by design intrinsically safe and that retains mechanical performance of commercial guidewires.

METHODS

The NHLBI passive guidewire is a 0.035" CMR-safe, segmented-core nitinol device constructed using short nitinol rod segments. The electrical length of each segment is less than one-quarter wavelength at 1.5 Tesla, which eliminates standing wave formation, and which therefore eliminates RF heating along the shaft. Each of the electrically insulated segments is connected with nitinol tubes for stiffness matching to assure uniform flexion. Iron oxide markers on the distal shaft impart conspicuity. Mechanical integrity was tested according to International Organization for Standardization (ISO) standards. CMR RF heating safety was tested in vitro in a phantom according to American Society for Testing and Materials (ASTM) F-2182 standard, and in vivo in seven swine. Results were compared with a high-performance commercial nitinol guidewire.

RESULTS

The NHLBI passive guidewire exhibited similar mechanical behavior to the commercial comparator. RF heating was reduced from 13 °C in the commercial guidewire to 1.2 °C in the NHLBI passive guidewire in vitro, using a flip angle of 75°. The maximum temperature increase was 1.1 ± 0.3 °C in vivo, using a flip angle of 45°. The guidewire was conspicuous during left heart catheterization in swine.

CONCLUSIONS

We describe a simple and intrinsically safe design of a metallic guidewire for CMR cardiovascular catheterization. The guidewire exhibits negligible heating at high flip angles in conformance with regulatory guidelines, yet mechanically resembles a high-performance commercial guidewire. Iron oxide markers along the length of the guidewire impart passive visibility during real-time CMR. Clinical translation is imminent.

Characterizing the angiogenic activity of patients with single ventricle physiology and aortopulmonary collateral vessels

OBJECTIVES

Patients with single ventricle congenital heart disease often form aortopulmonary collateral vessels via an unclear mechanism. To gain insights into the pathogenesis of aortopulmonary collateral vessels, we correlated angiogenic factor levels with in vitro activity and angiographic aortopulmonary collateral assessment and examined whether patients with single ventricle physiology have increased angiogenic factors that can stimulate endothelial cell sprouting in vitro.

METHODS

In patients with single ventricle physiology (n = 27) and biventricular acyanotic control patients (n = 21), hypoxia-inducible angiogenic factor levels were measured in femoral venous and arterial plasma at cardiac catheterization. To assess plasma angiogenic activity, we used a 3-dimensional in vitro cell sprouting assay that recapitulates angiogenic sprouting. Aortopulmonary collateral angiograms were graded using a 4-point scale.

RESULTS

Compared with controls, patients with single ventricle physiology had increased vascular endothelial growth factor (artery: 58.7 ± 1.2 pg/mL vs 35.3 ± 1.1 pg/mL, P < .01; vein: 34.8 ± 1.1 pg/mL vs 21 ± 1.2 pg/mL, P < .03), stromal-derived factor 1-alpha (artery: 1901.6 ± 1.1 pg/mL vs 1542.6 ± 1.1 pg/mL, P < .03; vein: 2092.8 pg/mL ± 1.1 vs 1752.9 ± 1.1 pg/mL, P < .02), and increased arterial soluble fms-like tyrosine kinase-1, a regulatory vascular endothelial growth factor receptor (612.3 ± 1.2 pg/mL vs 243.1 ± 1.2 pg/mL, P < .003). Plasma factors and sprout formation correlated poorly with aortopulmonary collateral severity.

CONCLUSIONS

We are the first to correlate plasma angiogenic factor levels with angiography and in vitro angiogenic activity in patients with single ventricle disease with aortopulmonary collaterals. Patients with single ventricle disease have increased stromal-derived factor 1-alpha and soluble fms-like tyrosine kinase-1, and their roles in aortopulmonary collateral formation require further investigation. Plasma factors and angiogenic activity correlate poorly with aortopulmonary collateral severity in patients with single ventricles, suggesting complex mechanisms of angiogenesis.

Optimized protocols for cardiac magnetic resonance imaging in patients with thoracic metallic implants

BACKGROUND

Cardiac magnetic resonance (MR) imaging is a valuable tool in congenital heart disease; however patients frequently have metal devices in the chest from the treatment of their disease that complicate imaging. Methods are needed to improve imaging around metal implants near the heart. Basic sequence parameter manipulations have the potential to minimize artifact while limiting effects on image resolution and quality.

OBJECTIVE

Our objective was to design cine and static cardiac imaging sequences to minimize metal artifact while maintaining image quality.

MATERIALS AND METHODS

Using systematic variation of standard imaging parameters on a fluid-filled phantom containing commonly used metal cardiac devices, we developed optimized sequences for steady-state free precession (SSFP), gradient recalled echo (GRE) cine imaging, and turbo spin-echo (TSE) black-blood imaging. We imaged 17 consecutive patients undergoing routine cardiac MR with 25 metal implants of various origins using both standard and optimized imaging protocols for a given slice position. We rated images for quality and metal artifact size by measuring metal artifact in two orthogonal planes within the image.

RESULTS

All metal artifacts were reduced with optimized imaging. The average metal artifact reduction for the optimized SSFP cine was 1.5+/-1.8 mm, and for the optimized GRE cine the reduction was 4.6+/-4.5 mm (P < 0.05). Quality ratings favored the optimized GRE cine. Similarly, the average metal artifact reduction for the optimized TSE images was 1.6+/-1.7 mm (P < 0.05), and quality ratings favored the optimized TSE imaging.

CONCLUSION

Imaging sequences tailored to minimize metal artifact are easily created by modifying basic sequence parameters, and images are superior to standard imaging sequences in both quality and artifact size. Specifically, for optimized cine imaging a GRE sequence should be used with settings that favor short echo time, i.e. flow compensation off, weak asymmetrical echo and a relatively high receiver bandwidth. For static black-blood imaging, a TSE sequence should be used with fat saturation turned off and high receiver bandwidth.

Intentional right atrial exit for microcatheter infusion of pericardial carbon dioxide or iodinated contrast to facilitate sub-xiphoid access

OBJECTIVES

We test the safety of transatrial pericardial access using small catheters, infusion of carbon dioxide (CO2 ) or iodinated contrast to facilitate sub-xiphoid access, and catheter withdrawal under full anticoagulation.

BACKGROUND

Sub-xiphoid pericardial access is required for electrophysiological and structural heart interventions. If present, an effusion protects the heart from needle injury by separating the myocardium from the pericardium. However, if the pericardium is 'dry' then there is a significant risk of right ventricle or coronary artery laceration caused by the heart beating against the needle tip. Intentional right atrial exit is an alternative pericardial access route, through which contrast media could be infused to separate pericardial layers.

METHODS

Transatrial pericardial access was obtained in a total of 30 Yorkshire swine using 4Fr or 2.8Fr catheters. In 16 animals, transatrial catheters were withdrawn under anticoagulation and MRI was performed to monitor for pericardial hemorrhage. In 14 animals, iodinated contrast or CO2 was infused before sub-xiphoid access was obtained.

RESULTS

Small effusions (mean 18.5 ml) were observed after 4Fr (1.3 mm outer-diameter) but not after 2.8Fr (0.9 mm outer-diameter) transatrial catheter withdrawal despite full anticoagulation (mean activated clotting time 383 sec), with no hemodynamic compromise. Pericardial CO2 resorbed spontaneously within 15 min.

CONCLUSIONS

Intentional transatrial exit into the pericardium using small catheters is safe and permits infusion of CO2 or iodinated contrast to separate pericardial layers and facilitate sub-xiphoid access. This reduces the risk of right ventricular or coronary artery laceration. 2.8Fr transatrial catheter withdrawal does not cause any pericardial hemorrhage, even under full anticoagulation.

Fully percutaneous transthoracic left atrial entry and closure as a potential access route for transcatheter mitral valve interventions

BACKGROUND

Percutaneous access for mitral interventions is currently limited to transapical and transseptal routes, both of which have shortcomings. We hypothesized that the left atrium could be accessed directly through the posterior chest wall under imaging guidance.

METHODS AND RESULTS

We tested percutaneous transthoracic left atrial access in 12 animals (10 pigs and 2 sheep) under real-time magnetic resonance imaging or x-ray fluoroscopy plus C-arm computed tomographic guidance. The pleural space was insufflated with CO2 to displace the lung, an 18F sheath was delivered to the left atrium, and the left atrial port was closed using an off-the-shelf nitinol cardiac occluder. Animals were survived for a minimum of 7 days. The left atrial was accessed, and the port was closed successfully in 12/12 animals. There was no procedural mortality and only 1 hemodynamically insignificant pericardial effusion was observed at follow-up. We also successfully performed the procedure on 3 human cadavers. A simulated trajectory to the left atrium was present in all of 10 human cardiac computed tomographic angiograms analyzed.

CONCLUSIONS

Percutaneous transthoracic left atrial access is feasible without instrumenting the left ventricular myocardium. In our experience, magnetic resonance imaging offers superb visualization of anatomic structures with the ability to monitor and address complications in real-time, although x-ray guidance seems feasible. Clinical translation seems realistic based on human cardiac computed tomographic analysis and cadaver testing. This technique could provide a direct nonsurgical access route for future transcatheter mitral implantation.