Utilization of Newer Fluoroscopic Imaging Equipment for LAA Closure in a Hybrid EP Lab: Initial Experience at a Community Hospital

Introduction

There has been a significant transition in healthcare from highly invasive surgical procedures to minimally invasive image-guided therapies. These minimally invasive therapies have helped to move inpatient procedures to day care procedures. Currently, more than 50% of patients in the United States are discharged from the hospital on the same day as their procedure — this trend is evident in cardiology as well. An upsurge in catheter-based treatments instead of open vascular interventions can be seen in all cardiac procedures. More complex procedures such as a left atrial appendage (LAA) closure device placement can now be performed in cardiac catheterization labs and hybrid labs. New fluoroscopy techniques that have been developed in the past few years have helped facilitate these complex catheter-based procedures. There has also been a transition from biplane to ceiling-mounted monoplane intervention labs with a large detector. LED surgical lighting and three-dimensional visualization systems can provide better procedural image quality and guidance. Next-generation angiography systems can also reduce radiation dose.

Among the procedures performed in an EP lab is LAA closure device placement, which is becoming the standard of care in patients with atrial fibrillation who are not candidates for conventional anticoagulation therapies.¹ Procedural safety and ease in LAA closure device placement have been greatly boosted by emerging x-ray technologies. In this article, we present two patients with non-valvular atrial fibrillation (NVAF) who underwent WATCHMAN device (Boston Scientific) implantation for stroke prevention, as they were not candidates for oral anticoagulation. One of these cases was performed in our new hybrid EP lab using newer x-ray imaging equipment (Philips’ Allura Xper FD20 x-ray system with AlluraClarity, and GE Healthcare’s Vivid E95 Cardiac Ultrasound), and the other was performed in our older conventional EP lab, just before the new lab was completed.

Case #1: 

A 74-year-old woman with a history of recurrent symptomatic permanent NVAF and longstanding hypertensive cardiovascular disease presented with worsening shortness of breath, melena, and a severe drop in hemoglobin (6.2 mg/dl) requiring hospitalization and packed red blood cell transfusion. She had been on anticoagulation with warfarin; however, it had to be stopped due to severe symptomatic anemia manifested as shortness of breath and dizziness secondary to bleeding duodenal ulcer. She was also at “fall risk” due to severe degenerative joint disease. Her CHA₂DS₂-VASc score was 4 (age, gender, coronary artery disease status post angioplasty, hypertension), and her HAS-BLED score was 3 (age, bleeding from duodenal ulcer, hypertension). In view of her recurrent symptomatic AF and high CHA₂DS₂-VASc score, secondary prevention for arterial embolization was deemed necessary. After a discussion with the patient and her family members, a non-pharmacologic approach with implantation of a LAA closure device was considered. A preoperative transesophageal echocardiogram (TEE) was performed to visualize the left atrium and left atrial appendage. It showed no evidence for left atrial appendage thrombi or mass (Figure 1). The left atrium was mildly dilated, measuring 4.4 cm in diameter. Her right atrium and ventricle were normal in size and function. Her left ventricle was normal in size with a well-preserved systolic function (60-65%), with no regional wall motion abnormalities, mild concentric left ventricular hypertrophy, and no evidence of left ventricular thrombus. 

She underwent successful insertion of a 27 mm WATCHMAN LAA closure device (Boston Scientific) under fluoroscopy and TEE guidance. This procedure was performed in the older conventional EP lab, requiring 13.4 minutes of fluoroscopy time and 871.4 mGy radiation exposure. She was discharged home on aspirin (81 mg) and warfarin (INR 2-2.5) for 45 days. 

A follow-up TEE showed no evidence for left atrial thrombus (Figure 2). The LAA closure device was well seated, with no echocardiographic evidence for device thrombus and leaks or shunts. Warfarin therapy was then discontinued; she will be treated with dual antiplatelet therapy with clopidogrel for six months, after which only a low-dose aspirin therapy will be continued. She remains asymptomatic.

Case #2: 

An 87-year-old man presented with a history of hypertensive cardiovascular disease, chronic obstructive pulmonary disease (COPD), permanent atrial fibrillation, and bradycardia-tachycardia syndrome requiring permanent pacemaker implantation in the past. Due to advanced degenerative joint disease (DJD), ambulatory dysfunction, and an unsteady gate, he suffered from several traumatic falls resulting in rib fractures (9-11th), chronic compression fracture of T12, and severe ecchymosis in his trunk as well as upper and lower extremities. Because of his high CHA₂DS₂-VASc score of 5 (advanced age, history of diastolic heart failure, TIA, hypertensive cardiovascular disease) and high HAS-BLED risk score (elderly, TA/stork, bleeding tendency, hypertension, labile INR), he was considered for a LAA closure procedure for stroke secondary prevention. 

His perioperative TEE showed no evidence of left atrial appendage thrombi or mass. His left atrium was moderately dilated, measuring 5.0 cm in diameter. His right atrium and ventricle were in the upper limits of normal size and function. His left ventricle was normal in size, with a well-preserved systolic function (60-65%), with no regional wall motion abnormalities, moderate concentric left ventricular hypertrophy, and no evidence of left ventricular thrombus. 

He underwent a successful implantation of a 24 mm WATCHMAN LAA closure device (Boston Scientific) under fluoroscopy and TEE guidance. Due to his severe COPD and elevated BMI (>38), we anticipated a more challenging procedure, but fortunately, our new hybrid EP lab was available. Fluoroscopy time was 30.1 minutes with 871 mGy radiation exposure. In spite of the longer procedure time required due to operative complexity because of his multiple comorbidities (COPD, morbid obesity, and advanced age), we noticed a significantly lower radiation exposure for this procedure. Operational modality was also felt to be swifter and more efficacious due to a higher image resolution and better delineation of the patient’s anatomy. 

He was discharged on low-dose aspirin (81 mg) and warfarin to maintain an INR of about 2 for 45 days. A follow-up TEE showed no evidence of left atrial thrombus. The LAA closure device was well seated with no echocardiographic evidence for device thrombus with leak or shunts on the WATCHMAN closure device. Warfarin therapy was then discontinued; he will be treated with dual antiplatelet therapy with clopidogrel for six months, after which only a low-dose aspirin therapy will be continued. He remains asymptomatic.

Discussion

Significant changes have occurred over the last decade in imaging systems and other technologies in the EP lab. These newer technologies have been developed to address issues such as reducing radiation dose, enhancing image quality, and improving procedural image guidance. As more complex procedures are being performed in cardiac labs and hybrid ORs, newer technologies are demonstrating distinct advantages over conventional devices. 

Radiation exposure is a big concern for patients and medical staff in the EP lab. It is known to cause disruption to the cellular DNA backbone by means of free-radical injury; this leads to individual cellular death, creating organ dysfunction.² These types of injuries are dose dependent. Almost all newer imaging devices offer advancements that lower the radiation dose. Improvements in x-ray tubes and more sensitive detectors are being used in newer devices. They combine real-time image noise reduction algorithms with advanced hardware, and significantly reduce the entrance radiation dose. They also maintain equivalent image quality at a fraction of the dose. 

Using the Philips Allura Xper FD20 x-ray system at our institution, our operators can easily adjust the frame rates to help reduce dose, and the system incorporates ClarityIQ software to achieve excellent visibility at a low x-ray dose in patients of all sizes. The software also helps to correct for motion, reduce noise, and auto-enhance the image by correcting pixel. Thus, the radiation dose barrier for new procedures and techniques in the EP lab is expected to be lowered by this newer technology. Real-time dose feedback about the cumulative amount of x-ray dose received after each procedure is beneficial. Archiving, reporting, and analyzing radiation data will help healthcare facilities prevent long-term radiation exposure. It also makes procedures quicker with more effective penetration. A powerful interventional x-ray helps deliver pertinent clinical information during the point of patient care. High-definition images help provide visual clarity and enhance physician efficacy. Image quality has been reported to be improved through the use of smaller spot sizes, shorter pulses, and automatic real-time motion compensation in subtraction imaging. Live navigation through soft tissue anatomy helps the physician to optimize treatment with a greater degree of confidence. This technology uses advanced 3D imaging with rotational angiography, which creates a computed tomography (CT) image of the anatomy. Some devices have been known to fuse the CT images with the live 2D fluoroscopic images; this fusion technology helps with better navigation and more accurate device placement. We have experienced that integration of the 3D images with the EP electromapping systems helps guide catheter ablation procedures without the need for live fluoroscopy. The newer x-ray machine has helped interventional facilities to indulge in longer and more complex procedures as well, by virtue of tissue penetration.^3-6 Risks associated with obese and elderly patients with significant comorbidities have been mitigated with these machines. 

With this evolution in imaging techniques, there have also been changes in detector devices. Currently, dedicated cardiac cath labs use smaller detectors in the range of 8- to 10-inch diagonals to allow C-arm angulations, which helps provide different views of the anatomy. Some companies have added a new 16-bit digital detector to their platform, which offers higher contrast.

Some notable ancillary features of the new device at our institution include a G-tube gravity device, which allows physicians to have radiation production without having to wear heavy lead aprons during a long procedure. An easily movable C-arm around the table provides more space to work. Complex and often long procedures can be carried out with a high degree of comfort by a large multidisciplinary team. (Figures 3, 4, and 5).

Other useful modifications in this modern imaging equipment include use of a flat emitter in the x-ray tube to generate smaller, square focal spots that can improve visibility of smaller vessels by up to 70%. Certain machines use dual-axis rotational angiography to image the entire heart in a single sweep of the C-arm (rather than multiple image acquisitions), thus protecting patients from a higher dose of contrast agents.

Conclusion

Newer technologies have been developed by various imaging system vendors to reduce radiation dose, improve image quality, and enhance procedural image guidance. More complex procedures such as LAA closure device placement and ablation procedures can be very well planned and performed in a swifter and more efficacious manner with the aid of these newer devices. We observed not only that radiation dose exposure was less with use of this newer technology, but that procedural ease was higher. Use of the WATCHMAN and other LAA closure devices will yield better outcomes and gain further popularity with their improvement of procedural safety, which can be achieved by utilizing newer fluoroscopic imaging equipment. We are excited to now be able to perform long EP procedures in elderly patients with multiple comorbidities and in those with larger body habitus. Use of a hybrid suite has also allowed our multidisciplinary team to work in a more spacious area. By virtue of its inherent capacity to convert into an open surgical room, the hybrid lab is well suited not only for cardiovascular procedures, but for vascular and neurological procedures as well.

Disclosures: The authors have no conflicts of interest to report regarding the content herein.   

References

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