Michael C. Slack

Real-Time Magnetic Resonance Imaging–Guided Stenting of Aortic Coarctation With Commercially Available Catheter Devices in Swine

Background—Real-time MR imaging (rtMRI) is now technically capable of guiding catheter-based cardiovascular interventions. Compared with x-ray, rtMRI offers superior tissue imaging in any orientation without ionizing radiation. Translation to clinical trials has awaited the availability of clinical-grade catheter devices that are both MRI visible and safe. We report a preclinical safety and feasibility study of rtMRI-guided stenting in a porcine model of aortic coarctation using only commercially available catheter devices. Method and Results—Coarctation stenting was performed wholly under rtMRI guidance in 13 swine. rtMRI permitted procedure planning, device tracking, and accurate stent deployment. “Active” guidewires, incorporating MRI antennas, improved device visualization compared with unmodified “passive” nitinol guidewires and shortened procedure time (26±11 versus 106±42 minutes; P=0.008). Follow-up catheterization and necropsy showed accurate stent deployment, durable gradient reduction, and appropriate neointimal formation. MRI immediately identified aortic rupture when oversized devices were tested. Conclusions—This experience demonstrates preclinical safety and feasibility of rtMRI-guided aortic coarctation stenting using commercially available catheter devices. Patients may benefit from rtMRI in the future because of combined device and tissue imaging, freedom from ionizing radiation, and the ability to identify serious complications promptly.

Antegrade Percutaneous Closure of Membranous Ventricular Septal Defect Using X-Ray Fused With Magnetic Resonance Imaging

OBJECTIVES We hypothesized that X-ray fused with magnetic resonance imaging (XFM) roadmaps might permit direct antegrade crossing and delivery of a ventricular septal defect (VSD) closure device and thereby reduce procedure time and radiation exposure. BACKGROUND Percutaneous device closure of membranous VSD is cumbersome and time-consuming. The procedure requires crossing the defect retrograde, snaring and exteriorizing a guidewire to form an arteriovenous loop, then delivering antegrade a sheath and closure device. METHODS Magnetic resonance imaging roadmaps of cardiac structures were obtained from miniature swine with spontaneous VSD and registered with live X-ray using external fiducial markers. We compared antegrade XFM-guided VSD crossing with conventional retrograde X-ray-guided crossing for repair. RESULTS Antegrade XFM crossing was successful in all animals. Compared with retrograde X-ray, antegrade XFM was associated with shorter time to crossing (167 +/- 103 s vs. 284 +/- 61 s; p = 0.025), shorter time to sheath delivery (71 +/- 32 s vs. 366 +/- 145 s; p = 0.001), shorter fluoroscopy time (158 +/- 95 s vs. 390 +/- 137 s; p = 0.003), and reduced radiation dose-area product (2,394 +/- 1,522 mG.m(2) vs. 4,865 +/- 1,759 mG.m(2); p = 0.016). CONCLUSIONS XFM facilitates antegrade access to membranous VSD from the right ventricle in swine. The simplified procedure is faster and reduces radiation exposure compared with the conventional retrograde approach.

Transcatheter coil closure of a right pulmonary artery to left atrial fistula in an ill neonate.

Although rare, a congenital direct fistula connection between the proximal right pulmonary artery and the left atrium can present as cyanosis in the newborn. We report the first case in which catheter‐based coil closure of such a fistula in a neonate resulted in rapid clinical improvement, obviating the need for surgical repair. Cathet. Cardiovasc. Intervent. 50:330–333, 2000.

Detection of Carbon Monoxide During Routine Anesthetics in Infants and Children

BACKGROUND: Carbon monoxide (CO) can be produced in the anesthesia circuit when inhaled anesthetics are degraded by dried carbon dioxide absorbent and exhaled CO can potentially be rebreathed during low-flow anesthesia. Exposure to low concentrations of CO (12.5 ppm) can cause neurotoxicity in the developing brain and may lead to neurodevelopmental impairment. In this study, we aimed to quantify the amount of CO present within a circle system breathing circuit during general endotracheal anesthesia in infants and children with fresh strong metal alkali carbon dioxide absorbent and define the variables associated with the levels detected. METHODS: Fifteen infants and children (aged 4 months to 8 years) undergoing mask induction followed by general endotracheal anesthesia were evaluated in this observational study. CO was measured in real time from the inspiratory limb of the anesthesia circuit every 5 minutes for 1 hour during general anesthesia. Carboxyhemoglobin (COHb) levels were measured at the 1-hour time point and compared with baseline. RESULTS: CO was detected in all patients older than 2 years (0–18 ppm, mean 3.7 ± 4.8 ppm) and rarely detected in patients younger than 2 years (0–2 ppm, mean 0.2 ± 0.6 ppm). Only the relationship between CO concentration and fresh gas flow to minute ventilation ratio (FGF:&OV0312;e) remained significant after adjustment in longitudinal regression analysis (P < 0.001). Although not powered to determine such a relationship, CO levels were weakly associated with the use of desflurane and female sex. There was no significant association between CO concentration and anesthetic concentration. Baseline COHb levels were higher in children younger than 2 years and decreased significantly at the 1-hour time point compared with baseline and children older than 2 years. However, COHb levels increased significantly from baseline in a predictable manner consistent with CO exposure in children older than 2 years. FGF:&OV0312;e correlated significantly with change in COHb using simple linear regression (r = 0.62; P < 0.02). CONCLUSIONS: CO was detected routinely during general anesthesia in infants and children when FGF:&OV0312;e was <1. Peak CO levels measured in the anesthesia breathing circuit were in the range thought to impair the developing brain. Further study is required to identify the source of CO detected (CO produced by degradation of volatile anesthetic versus rebreathing CO from endogenous sources or both). However, these findings suggest that avoidance of low-flow anesthesia will prevent rebreathing of exhaled CO, and use of carbon dioxide absorbents that lack strong metal hydroxide could limit inspired CO if detection was attributable to degradation of volatile anesthetic.

Percutaneous Closure of a Left Ventricular Outflow Tract Pseudoaneurysm Causing Extrinsic Left Coronary Artery Compression by Transseptal Approach

A 44-year-old man underwent aortic valve replacement with a porcine bioprosthesis 21 years ago for infective endocarditis complicated by a cerebral mycotic aneurysm and intracranial bleeding. Nine years ago, he had a second aortic valve replacement with a mechanical bileaflet tilting-disk prosthesis because of porcine prosthesis degeneration. No pseudoaneurysm was noted on the operative report. Six months ago, he developed angina and had a positive stress test for ischemia. Angiography showed severe left main coronary artery (LM) stenosis, which was treated with intravascular ultrasound–guided percutaneous coronary intervention with a zotarolimus-eluting stent. Two months ago, he again developed angina. Follow-up angiography and intravascular ultrasound revealed severe in-stent restenosis in the proximal third of the LM and systolic narrowing of the distal third, suggestive of extrinsic compression (Figure 1 and online-only Data Supplement Movie 1). In-stent restenosis was treated at that time with a sirolimus-eluting stent. A transesophageal echocardiogram revealed a large pseudoaneurysm lateral to the aortic root; color …

Transthoracic delivery of large devices into the left ventricle through the right ventricle and interventricular septum: preclinical feasibility

BackgroundWe aim to deliver large appliances into the left ventricle through the right ventricle and across the interventricular septum. This transthoracic access route exploits immediate recoil of the septum, and lower transmyocardial pressure gradient across the right versus left ventricular free wall. The route may enhance safety and allow subxiphoid rather than intercostal traversal.MethodsThe entire procedure was performed under real-time CMR guidance. An “active” CMR needle crossed the chest, right ventricular free wall, and then the interventricular septum to deliver a guidewire then used to deliver an 18Fr introducer. Afterwards, the right ventricular free wall was closed with a nitinol occluder. Immediate closure and late healing of the unrepaired septum and free wall were assessed by oximetry, angiography, CMR, and necropsy up to four weeks afterwards.ResultsThe procedure was successful in 9 of 11 pigs. One failed because of refractory ventricular fibrillation upon needle entry, and the other because of inadequate guidewire support. In all ten attempts, the right ventricular free wall was closed without hemopericardium. There was neither immediate nor late shunt on oximetry, X-ray angiography, or CMR. The interventricular septal tract fibrosed completely. Transventricular trajectories planned on human CT scans suggest comparable intracavitary working space and less acute entry angles than a conventional atrial transseptal approach.ConclusionLarge closed-chest access ports can be introduced across the right ventricular free wall and interventricular septum into the left ventricle. The septum recoils immediately and heals completely without repair. A nitinol occluder immediately seals the right ventricular wall. The entry angle is more favorable to introduce, for example, prosthetic mitral valves than a conventional atrial transseptal approach.

Severe tricuspid valve stenosis secondary to pacemaker leads presenting as ascites and liver dysfunction: a complex problem requiring a multidisciplinary therapeutic approach

Tricuspid stenosis secondary to ventricular pacemaker leads is uncommon. We present a unique case of iatrogenic tricuspid stenosis secondary to fusion of the valve leaflets to transvenous implanted pacing leads. This occurred in an adult with childhood repaired Tetralogy of Fallot and high grade surgical heart block following multiple pacemaker procedures. The case was complicated by superior vena cava (SVC) and innominate vein stenosis secondary to implanted pacing leads, severe tricuspid valve (TV) stenosis, perforation of the heart by one of the implanted transvenous ventricular pacing leads, prolapse of the transvenous atrial pacing lead into the right ventricle, and unusual coronary sinus anatomy. We describe a multidisciplinary approach to management.

Management of a large atrial septal occluder embolized to the left ventricular outflow tract without the use of cardiac surgery.

Transcatheter closure of secundum‐type atrial septal defects (ASDs) using the AMPLATZER™ Septal Occluder (ASO) has been in use for more than a decade since its US Food and Drug Administration approval in 2001. Device embolization remains an uncommon complication, which can sometimes occur after the initial deployment. Previous reports of ASO devices embolized to the left ventricle have primarily been managed by open‐heart surgical retrieval. We present a case of an ASO device embolized to the left ventricular outflow tract (LVOT) 18 hr after initial implantation, which was successfully retrieved percutaneously, followed by successful closure of the ASD using a larger device.

Percutaneous closure of a prosthetic pulmonary paravalvular leak.

Paravalvular leak following prosthetic valve surgery has the potential to cause serious complications such as hemolysis and congestive heart failure. Successful percutaneous closures of prosthetic mitral and aortic paravalvular leaks have been performed as an alternative to reoperation. This case represents the first known report of successful percutaneous closure of a prosthetic pulmonary paravalvular leak in an adult patient with a history of congenital heart disease using two muscular ventricular septal defect occluder devices.

Balloon angioplasty with stenting to correct a functionally interrupted aorta: A case report with three-year follow-up.

A 16‐year‐old male presenting with upper extremity hypertension was found to have a severe form of discrete coarctation with complete luminal obliteration, causing a functional interruption of the thoracic aorta. Fluoroscopically guided perforation of the obstruction and creation of a neo‐aortic lumen was performed. This was followed by balloon angioplasty and stent placement, successfully relieving the coarctation. The procedural method, acute and late follow‐up results, and a discussion of the potential risks and benefits are presented.