Remaining of contrast dye ice cap during PVI by cryoballoon ablation; a case report

Abstract

Pulmonary vein isolation (PVI) with cryoballoon (CB) ablation technology is widely used to treat drug-resistant atrial fibrillation (AF). During CB ablation, there is a possibility of forming an ice cap of contrast-color on top of the balloon. If automatic balloon deflate occurs before the ice cap dissolves, embolization to the systemic circulation is possible. This case report describes the remaining of a contrast-colored ice cap to the systemic circulation in the left superior pulmonary vein (LSPV) and the remaining contrast-colored ice cap throughout the balloon deflate and its gradual melting a few seconds after the balloon deflate in the right superior pulmonary vein (RSPV). Additionally, a strategy for its prevention is presented.

Introduction

CB ablation is a safe and effective method for PVI to treat paroxysmal AF [1]. In patients with paroxysmal AF who have been treated with drugs but still have symptoms, PVI can be considered with class I. PVI can be done with CB ablation or radiofrequency ablation (RFA) technology and in PVI, CB has become an ablation approach that offers similar clinical efficacy compared to RFA [2]. Some side effects such as pericarditis and tamponade are less in the CB ablation compare to RFA, but other side effects (such as, embolism, and cerebrovascular accidents, damage to the femoral vein and artery, atrioesophageal fistula) are the same in both methods. During CB ablation, a contrast-colored ice cap may form on top of the balloon and often melts before the balloon is deflated. If an ice cap with contrast dye remains after balloon deflate, it may be embolized into the systemic circulation and there are few case reports about the remaining of the contrast-colored ice cap [3, 4], but extensive studies in this field have not been done so far. There are many ambiguities about the main cause of this phenomenon and the ways to prevent it. In this study, we report an interesting case that both the phenomenon of the contrast-colored ice cap remaining occurs in the LSPV and in the RSPV contrast-colored ice cap was stable throughout the balloon deflate phase and gradually resolved within a few seconds after deflation of the balloon.

Case presentation

A 70-year-old woman with a history of drug-resistant paroxysmal AF was a candidate for PVI using CB. Transesophageal echocardiography was performed before CB ablation and no clot was seen. CB ablation was performed using POLARx-TM Balloon Catheter (28 mm). The POLARx advanced technology provides a stable balloon size of 28 mm through the inflation and ablation phases.

The procedure was performed under deep sedation using bolus midazolam and Fentanyl. Three venous accesses were taken through the right femoral vein, one for the transseptal sheath and the other for the placement of catheters in the coronary sinus and superior vena cava to stimulate the right phrenic nerve. Then, trans-septal access to the left atrium was performed using a standard needle through the Agilis sheath. After performing trans-septal access to the left atrium, the Agilis sheath was replaced with a CB ablation sheath. Then, POLARx-TM Balloon catheter was sequentially placed in each PV ostium. To confirm good occlusion of each PV ostium, contrast dye was injected through the tip of the catheter.

During performing PVI of the LSPV, immediately after deflation of the balloon (with TTI = 40 s), we observed remaining of the contrast-colored ice cap from POLARx-TM to the left atrium, then to the left ventricle and finally to the descending aorta (Fig. 1, video 1). The patient had no side effects related to the remaining of this formation. Further, during the freezing phase, ice formation was observed in the RSPV, which was opaque by the contrast medium at the tip of the inflated balloon (Fig. 2, video 2). The ice cap was stable throughout the entire thawing phase of the balloon and gradually resolved within a few seconds after deflation of the balloon. Considering the patient’s stability, the procedure was continued and all four PVs were isolated. No side effects were observed during and after the procedure. The patient was discharged the next morning with good general health conditions.

Fig. 1 and video 1

During performing PVI of the LSPV, immediately after deflation of the balloon, remaining of the contrast-colored ice cap from the POLARx-TM to the left atrium, then to the left ventricle and finally to the descending aorta was observed

Fig. 2 and video 2

During the freezing phase, ice formation was observed in the RSPV and this contrast-colored ice cap was persistent throughout the balloon deflating phase and gradually resolved within seconds after balloon deflate

Discussion

Ablation is recommended as the second line of treatment after failure (or intolerance) of class I or III antiarrhythmic drugs in patients with AF. ESC and NAHA guidelines recommend first-line AF ablation in highly selected patients with symptomatic paroxysmal AF (class IIa) or persistent AF (class IIb) [1, 2]. Today, PVI is the cornerstone of catheter ablation of AF in patients with drug-resistant AF [1, 2, 5]. Many studies have compared RF and CB ablation. Some studies have shown fewer complications and fewer hospitalizations with CB ablation [6,7,8]. Our patient was suffering from paroxysmal AF and was being treated with beta blockers and class 3 antiarrhythmics for several months, but unfortunately the drug treatment was not effective and the patient remained symptomatic. Therefore, this patient became a candidate for PVI and the CB technique was used to PVI. During the isolation of LSPV, immediately after deflate of POLARx-TM Balloon, contrast-colored ice cap from POLARx-TM was embolized into the left atrium, then the left ventricle, and finally the aorta. A similar phenomenon was observed by SERGIO at et al. in 2017 during PVI in a patient with paroxysmal AF. They used of the 28-mm cryoballoon Arctic Front Advance Short Tip (ADV-ST) catheter (Medtronic, Inc., Minneapolis, MN, USA) [3]. Bordignon et al. explained the ice cap phenomenon in the second generation cryoballoon catheter and they used the second generation cryoballoon device (Arctic Front Advance, Medtronic CryoCath LP). The phenomenon reported by Bordignon was similar to our phenomenon that occurred during RSPV isolation in our patient. In fact, during CB ablation, it is not unusual for a contrasting -colored ice cap to form on top of the balloon [4]. But automatic deflation of the balloon before ice cap dissolution may increase the risk of remaining of large ice mixed contrast crystals into the systemic circulation. Fortunately, our patient did not show any side effects. Also, in other case reports related to remaining of ice pieces caused by CB ablation for PVI, no side effects were mentioned [3, 4]. Whether ice remaining poses a clinical risk is still unknown. According to the settings made by Boston Company engineers in our center, automatic balloon deflate occurs at + 20 ⁰C temperature. Although the temperature is not measured on the balloon surface and a discrepancy between reported temperatures and distal balloon surface temperature is unavoidable. In fact, balloon deflate occurs when there are still pieces of ice in the ostium of the pulmonary vein. The ice cap might not always be visible as contrast agent is not used regularly or dissolved before freezing. Probably this phenomenon is quite common but seldom visualized.