Background

Percutaneous balloon pulmonary valvuloplasty (PBPV) is the treatment of choice for infants and neonates with isolated valvar pulmonary stenosis (PS) [1]. PBPV is a low-risk procedure, though the standard approach exposes the patient to ionizing radiation and iodinated contrast media [2]. No amount of radiation exposure is considered safe and children with congenital heart disease are particularly susceptible to the stochastic effects of ionizing radiation as they have immature organs, a longer anticipated lifespan following exposure, and are often exposed to a higher lifetime cumulative dose of radiation [3]. Considering these risks, there has been a global movement toward radiation reduction during cardiac catheterization procedures [4]. Furthermore, exposure to free iodide in contrast media can adversely affect thyroid function, causing transient but clinically significant hypothyroidism [5]. These exposure risks can be mitigated with the use of real-time, non-irradiating imaging modalities such as transthoracic and transesophageal echocardiography (TTE and TEE), which have been utilized to assist with device closure of shunt lesions such as atrial septal defects and patent ductus arteriosus, but have also played a role in limiting radiation exposure in extremely premature infants as well as pregnant and post-transplant patients [6,7,8,9].

Since 2019, the Interventional Cardiology Program at Lurie Children’s Hospital has used TTE guidance for PBPV in neonates and infants with isolated pulmonary valve stenosis. The initial experience using echocardiography-guided PBPV (EG-PBPV) for isolated pulmonary valve stenosis in patients less than 1 year of age is reported, testing the hypothesis that EG-PBPV has equivalent technical success and complication profile as compared to standard PBPV (S-PBPV), while reducing exposure to ionizing radiation and iodinated contrast media.

Methods

Develo** the Echo-Guided Percutaneous Balloon Pulmonary Valvuloplasty Protocol

A protocol for transthoracic EG-PBPV was created to mitigate contrast and radiation exposure (Fig. 1). Interventional and non-invasive imaging specialists performed a detailed review of our standard procedure and identified opportunities where echocardiography could be used as an alternative to fluoroscopy and/or angiography.

Fig. 1
figure 1

Patient preparation and protocol for echo-guided percutaneous balloon pulmonary valvuloplasty

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Key changes began with dra** of the patient. Groins were prepped and draped in typical fashion, but drapes were secured to the lower abdomen using attached adhesive and taped to the anterior–posterior camera in order to create a sterile screen between the chest and groins and avoid contamination of the operating field (Fig. 2). This setup left the chest exposed to allow the imaging team access for subxiphoid, apical, and parasternal imaging windows. Adjustment of the location of the defibrillator patches, typically to the back, was also required to allow echocardiographic windows. The echocardiography machine was placed to the left of the patient table with the imaging screen positioned immediately lateral to the fluoroscopy cameras to allow visualization of both the echocardiography and fluoroscopy images by the primary echocardiographer and proceduralist. A subspecialized echocardiographer was present, with a trained technician as the primary operator. Before establishing endovascular access, a baseline echocardiographic survey was performed with attention to pulmonary valve annulus diameter from parasternal views, branch pulmonary artery size, tricuspid valve function, right ventricular systolic function, pericardial effusion, and importantly, for the presence of sub-valvar or supra-valvar obstruction.

Fig. 2
figure 2

(A) Drape extended from patient abdomen to AP camera, dividing sterile and non-sterile fields. (B) Sonographer in position to allow comfortable access to patient while maintaining sterile field. (C) Drapes applied to allow subxiphoid, apical, and parasternal views

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Catheter manipulation during the right heart catheterization and guidewire positioning were done using standard fluoroscopy. The larger pulmonary artery from the echocardiographic survey was selected for wire position to ensure distal balloon accommodation during valve dilation. The balloon position across the pulmonary valve was confirmed using subcostal views and the dilation was performed with simultaneous 2D echocardiography and lateral camera fluoroscopy only with the sector collimated to ensure the sonographer’s hand was not in the beam path. A subcostal right anterior oblique (RAO) view by echocardiography was the most helpful for guiding catheter manipulation and balloon positioning as it provided a complete view of the relevant anatomy. After each dilation, various echocardiographic views were used to measure the residual valve gradient and degree of pulmonary regurgitation. We then used a 65-cm non-taper angled glide catheter (Terumo, Somerset, NJ) to perform pullback over the wire to document the residual peak-to-peak valve gradient. The procedure was considered complete once the peak-to-peak gradient was < 35 mmHg or the balloon-to-annulus ratio exceeded 1.4:1.

Upon completion, the catheter and wire were removed, and a final echocardiographic survey was performed to assess peak gradient and degree of pulmonary regurgitation in the absence of any instruments in situ. We also used this as an opportunity to evaluate for tricuspid valve injury or interval development of a pericardial effusion.

Study Design

This was a single-center retrospective case–control study comparing EG-PBPV and S-PBPV procedures over a 3-year period from 12/2017 to 12/2020. From 9/2019, patients were considered EG-PBPV candidates if they were less than 12 months of age and presented with a pre-operative diagnosis of valvar pulmonary stenosis. All cases were performed with the patient under general anesthesia with the same biplane imaging system (Toshiba Infinix, Irving, CA) with similar fluoroscopy settings (default fluoroscopy frame rate 3 or 5 frames per second (FPS) and digital acquisition 15 FPS during the study period). Vascular access was established in a femoral vein in every case. Arterial access was obtained at the discretion of the interventionalist. EG-PBPV was performed with a Philips CV**ing on TV. d Following balloon valvuloplasty, the flow acceleration across the pulmonary valve has resolved. RAO right anterior oblique, RA right atrium, RV right ventricle, PA pulmonary artery, LA left atrium, AoV aortic valve

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