Reduction of Iatrogenic Atrial Septal Defects with an Anterior and Inferior Transseptal Puncture Site when Operating the Cryoballoon Ablation Catheter
PREPARAÇÃO DO INSTRUTOR
CONCEITOS
PROTOCOLO DO ALUNO
Ethical Statement: All methods and procedures performed in these examinations were typical and standard-of-care during this time period of data collection. Informed consent was obtained from all patients, and local institutional review board approval was granted for both studies.
1. Transseptal Access
NOTE: Procedural methods and techniques have now been well described in several publications6-11, and the cryoballoon ablation strategy used here was similar to published descriptions.
- Examine patients with a transesophageal echocardiogram on the day of the AF ablation procedure. Use transesophageal echocardiogram imaging to assess the LA for thrombus presence or formation.
- Re-schedule ablation for any patient with LA thrombus present, and correct the patient anticoagulation strategy.
- Establish patient sedation with the use of general anesthesia (with an agent such as intravenous propofol) or conscious sedation (with agents such as intravenous fentanyl and versed). In both sedation methods, do not use a paralytic agent so that phrenic nerve monitoring can be used during the ablation procedure.
- During the AF ablation procedure, use ICE guidance for the transseptal catheterization with a Mullins-type sheath. Use the ICE guidance to position the transseptal needle at the septum, to avoid aortic puncture, and to safeguard against inadvertent LA lateral wall needle-puncture (by examining the needle “tenting” distance during transseptal puncture)12.
NOTE: In the traditional FO location, the transseptal access point is at the thinnest septal tissue depth near the center of the septum which is evaluated by “tenting” the septum with the transseptal needle under ICE imaging (Figure 1). - For the IL transseptal location, enter approximately one centimeter below the traditional FO site and at an anterior septal location (Figure 1; panels A and B). The IL location is found through evaluation of ICE and fluoroscopy once the FO site is established.
- Use ICE plane imaging to define the entry point in the IL location. Sweep the ICE image anterior towards the plane of the mitral value to define the anterior position of the site.
- The inferior location will be dependent on the IL, which is triangular in cross-section. Place the transseptal needle puncture at the center of this triangular area.
- Facilitate the IL puncture by further bending the transseptal needle approximately ½ inch from this distal tip. Needle bending is customized to the approach angle on LAO view of the inferior vena cava into the right atrium. Use more needle bending when the approach angle is vertical rather than horizontal to the patient’s body axis.
- Optionally, use a radiofrequency transseptal needle to facilitate the IL position technique; however, only standard transseptal needles were used for this study.
- Immediately after transseptal puncture, administer heparin bolus using a patient weight-based protocol and then give supplemental doses of heparin throughout the procedure with the goal of maintaining active clotting time between 350 and 400 sec.
- Establish the transseptal access route with an exchange of the transseptal needle with a guidewire.
2. Cryoballoon Ablation
- Use the guidewire to introduce the cryoballoon sheath. Then deploy the cryoballoon catheter and the dedicated inner lumen circular mapping catheter into the LA through the cryoballoon sheath.
- During each cryoballoon ablation, inflate the cryoballoon and advance it over the inner lumen circular mapping catheter which is wired towards the PV ostium.
- Inject 5 to 10 ml of radiopaque contrast agent (isovue 300) through the cryoballoon catheter inner lumen.
- Confirm cryoballoon-to-PV occlusion by using the retention of contrast agent after injection at the distal tip of the balloon.
- Additionally (or alternatively), confirm cryoballoon-to-PV occlusion by ICE imaging under color-flow Doppler using the lack of flow around the balloon anterior surface as an indicator of occlusion.
- Start the cryoballoon cryoablation once occlusion is established by pressing the “start” button on the cryoconsole. This action will push cryorefrigerant into the cryoballoon catheter and initiate cryoablation.
- On right-sided PVs, use a diagnostic catheter in the right atrial/superior vena caval junction and position it to pace the right phrenic nerve.
- Pace the phrenic nerve at 20 mA amplitude and 2.0 msec pulse width, and monitor phrenic nerve function by manual detection of diaphragmatic contractions. Immediately terminate any ablation if phrenic nerve function is diminished, delayed, or lost.
- Deliver a minimum of two freezes, each lasting 120 to 180 sec, while using the inner lumen circular mapping catheter to monitor both real-time and post-ablation PVI through entrance and exit block testing.
- Once entrance and exit block is established at each PV, withdraw the cryoballoon, sheath, and inner lumen circular mapping catheter.
- Use standard medical care to stop bleeding at vascular entry points and discharge patients via hospital protocols, which may include anticoagulation pharmaceutical therapy and guidance on antiarrhythmic drugs.
Reduction of Iatrogenic Atrial Septal Defects with an Anterior and Inferior Transseptal Puncture Site when Operating the Cryoballoon Ablation Catheter
Learning Objectives
The 200 consecutive patients that underwent retrospective chart review were all given a transseptal puncture near the IL position. Examination of the equipment list and ablation records are used to established the proportion of patients that achieved PVI with a singular usage of the cryoballoon catheter. An additional group of 173 patients were assessed and tested for the differential usage of transseptal entry location. The data is collected in a 3:1 manner, whereby 128 patients are examined with an IL transseptal location and compared to 45 patients who had a FO transseptal site. Acute IASD rates for FO versus IL transseptal locations are assessed by Doppler ICE imaging and later compared by Fisher’s exact statistical testing. In this study, statistical significance is set at P <0.05.
In the group of 200 patients undergoing an IL site transseptal puncture, 186 patients (93%) did not require the usage of an additional focal radiofrequency ablation catheter. Representative fluoroscopy images of each of the four PVs during cryoballoon ablation are illustrated in Figure 2A-D. Examination of Figure 2 demonstrates that the cryoballoon catheter and steerable sheath were not required to use full catheter and sheath deflection to achieve PVI at the inferior PVs. Furthermore, analyses of catheter and sheath deflection angles during inferior PV cryoablation via IL transseptal puncture in all 328 patients shows that full cryoballoon catheter and sheath deflection were never necessary to achieve a cryoballoon-to-PV occlusion.
Analysis of the ICE Doppler flow acutely after removal of the ablation sheath revealed that all 45 patients who had a FO puncture site had evidence of atrial septal flow consistent with a small atrial septal defect with left-to-right atrial fluid movement (Qp—Qs ratio greater than 1). By contrast, 42 of the 128 patients (32.8%) with the IL puncture site demonstrated acute Doppler ICE flow after removal of the transseptal sheath (Figure 3). The difference in acute Doppler flow detection between the IL and FO transseptal puncture site was statistically significant by Fisher’s Exact testing (P <0.0001).
Lastly, during the entire examination of 373 patients, no patient experienced a pericardial effusion or tamponade. Also, neither septal dissections nor hematoma formations were observed for either FO or IL transseptal techniques. A combination of ICE and fluoroscopy imaging during all procedures demonstrated qualitatively that the IL position often had ample distance at a lower entry position from collateral tissue puncture. In the IL position, the transseptal needle would point towards the mitral valve rather than the left atrial appendage or left atrial roof. Both of the latter two left atrial lateral structures required more imaging attention when utilizing the FO transseptal approach.
Figure 1 demonstrates that “tenting” of the FO can help to determine an inferior and anterior transseptal location near the IL. This anterior and inferior transseptal location can allow the cryoballoon catheter to be used with minimal catheter and/or sheath deflection. Specifically, with ablations in the lower PVs, the IL transseptal location allows for a “more direct” alignment between the cryoballoon catheter and the tubular section of each PV. As demonstrated in Figure 2, this alignment between the PV and cryoballoon catheter allows for the most direct transfer of occlusion force that is necessary to ensure that a complete and circumferential lesion is created surrounding each PV during the cryoballoon ablation procedure. Incomplete cryoballoon lesion sets are created when there are gaps between the cryoballoon and PV contact, which results in reduced transfer of cold between the balloon and tissue.
Figure 3 illustrates another acute advantage of using the IL location during a cryoballoon ablation procedure. When the FO location is used, immediate withdrawal of the cryoballoon and sheath will often leave an acute left-to-right blood-shunt at the transseptal puncture location, which can be observed with color-flow Doppler imaging. Alternatively the IL location for a transseptal puncture is typically in a thicker part of the septum. Consequently, when the cryoballoon and sheath are removed from the LA, there is less left-to-right shunting of blood, and in some cases there is no detectable blood shunting when viewed by color-flow Doppler imaging.
Figure 1: ICE images of FO and IL transseptal puncture. (A) The traditional placement of transseptal entry at the fossa ovalis will demonstrate “tenting” of the septum tissue due to the sparsity of tissue when viewed by fluoroscopy. (B) An inferior and anterior transseptal approach at the inferior limbus will provided a mechanical advantage when using the cryoballoon catheter. Yellow arrows indicate the transseptal puncture locations. Please click here to view a larger version of this figure.
Figure 2: Cryoablation at the PVs. Cryoballoon placement at four pulmonary vein (PV) locations with antral balloon positioning at each vein as view by fluoroscopy. All PV are viewed in LAO positioning with an inferior and anterior transseptal entry position (IL location). (A) The left superior PV is an almost straight-on approach from the transseptal entry, and it is typically the first PV that is ablated because of the ease of guidewire approach. (B) The left inferior PV will use sheath deflection to achieve proper PV-to-balloon occlusion. (C and D) Phrenic nerve pacing will be used to monitor nerve function during right-sided ablations. Both PVs will use sheath deflection, and the right inferior PV (RIPV) will typical use the highest degree of deflection. However, note that with an inferior and anterior approach, the RIPV ablation does not require the maximal deflection capability that is provided in the cryoballoon system. Yellow brackets are the cryoballoon and blue brackets are the steerable sheath. Please click here to view a larger version of this figure.
Figure 3: ICE imaging with color-flow Doppler. Doppler images from intracardiac echocardiography. Notice the amount of Doppler flow that is present after catheter removal at the septum when comparing the fossa ovalis transseptal position (A) compared to the inferior limbus position (B). Yellow arrows indicate the transseptal puncture location. Please click here to view a larger version of this figure.
Figure 4: Angles of cryoballoon approach into PVs. A virtual reconstruction of FO versus IL transseptal locations. The FO puncture site achieved complete occlusion at the following deflection angles: 131°, 32°, 206°, and 329°. By comparison, the IL transseptal site achieved occlusion with the following deflection angles: 121°, 45°, 182°, and 349°. Note that less catheter deflection is needed in the inferior PVs for the IL location. Green lines are representative of the cryoballoon catheter direction from a FO site, and red lines denote the cryoballoon direction from an IL site. Please click here to view a larger version of this figure.
List of Materials
| Arctic Front Advance Cardiac CryoAblation Catheter | Medtronic, Inc. | 2AF284 | 28mm Cryoballoon catheter |
Preparação do Laboratório
The cryoballoon catheter ablates atrial fibrillation (AF) triggers in the left atrium (LA) and pulmonary veins (PVs) via transseptal access. The typical transseptal puncture site is the fossa ovalis (FO) – the atrial septum’s thinnest section. A potentially beneficial transseptal site, for the cryoballoon, is near the inferior limbus (IL). This study examines an alternative transseptal site near the IL, which may decrease the frequency of acute iatrogenic atrial septal defect (IASD). Also, the study evaluates the acute pulmonary vein isolation (PVI) success rate utilizing the IL location. 200 patients were evaluated by retrospective chart review for acute PVI success rate with an IL transseptal site. An additional 128 IL transseptal patients were compared to 45 FO transseptal patients by performing Doppler intracardiac echocardiography (ICE) post-ablation to assess transseptal flow after removal of the transseptal sheath. After sheath removal and by Doppler ICE imaging, 42 of 128 (33%) IL transseptal patients demonstrated acute transseptal flow, while 45 of 45 (100%) FO transseptal puncture patients had acute transseptal flow. The difference in acute transseptal flow detection between FO and IL sites was statistically significant (P <0.0001). Furthermore, 186 of 200 patients (with an IL transseptal puncture) did not need additional ablation(s) and had achieved an acute PVI by a “cryoballoon only” technique. An IL transseptal puncture site for cryoballoon AF ablations is an effective location to mediate PVI at all four PVs. Additionally, an IL transseptal location can lower the incidence of acute transseptal flow by Doppler ICE when compared to the FO. Potentially, the IL transseptal site may reduce later IASD complications post-cryoballoon procedures.
The cryoballoon catheter ablates atrial fibrillation (AF) triggers in the left atrium (LA) and pulmonary veins (PVs) via transseptal access. The typical transseptal puncture site is the fossa ovalis (FO) – the atrial septum’s thinnest section. A potentially beneficial transseptal site, for the cryoballoon, is near the inferior limbus (IL). This study examines an alternative transseptal site near the IL, which may decrease the frequency of acute iatrogenic atrial septal defect (IASD). Also, the study evaluates the acute pulmonary vein isolation (PVI) success rate utilizing the IL location. 200 patients were evaluated by retrospective chart review for acute PVI success rate with an IL transseptal site. An additional 128 IL transseptal patients were compared to 45 FO transseptal patients by performing Doppler intracardiac echocardiography (ICE) post-ablation to assess transseptal flow after removal of the transseptal sheath. After sheath removal and by Doppler ICE imaging, 42 of 128 (33%) IL transseptal patients demonstrated acute transseptal flow, while 45 of 45 (100%) FO transseptal puncture patients had acute transseptal flow. The difference in acute transseptal flow detection between FO and IL sites was statistically significant (P <0.0001). Furthermore, 186 of 200 patients (with an IL transseptal puncture) did not need additional ablation(s) and had achieved an acute PVI by a “cryoballoon only” technique. An IL transseptal puncture site for cryoballoon AF ablations is an effective location to mediate PVI at all four PVs. Additionally, an IL transseptal location can lower the incidence of acute transseptal flow by Doppler ICE when compared to the FO. Potentially, the IL transseptal site may reduce later IASD complications post-cryoballoon procedures.
Procedimento
The cryoballoon catheter ablates atrial fibrillation (AF) triggers in the left atrium (LA) and pulmonary veins (PVs) via transseptal access. The typical transseptal puncture site is the fossa ovalis (FO) – the atrial septum’s thinnest section. A potentially beneficial transseptal site, for the cryoballoon, is near the inferior limbus (IL). This study examines an alternative transseptal site near the IL, which may decrease the frequency of acute iatrogenic atrial septal defect (IASD). Also, the study evaluates the acute pulmonary vein isolation (PVI) success rate utilizing the IL location. 200 patients were evaluated by retrospective chart review for acute PVI success rate with an IL transseptal site. An additional 128 IL transseptal patients were compared to 45 FO transseptal patients by performing Doppler intracardiac echocardiography (ICE) post-ablation to assess transseptal flow after removal of the transseptal sheath. After sheath removal and by Doppler ICE imaging, 42 of 128 (33%) IL transseptal patients demonstrated acute transseptal flow, while 45 of 45 (100%) FO transseptal puncture patients had acute transseptal flow. The difference in acute transseptal flow detection between FO and IL sites was statistically significant (P <0.0001). Furthermore, 186 of 200 patients (with an IL transseptal puncture) did not need additional ablation(s) and had achieved an acute PVI by a “cryoballoon only” technique. An IL transseptal puncture site for cryoballoon AF ablations is an effective location to mediate PVI at all four PVs. Additionally, an IL transseptal location can lower the incidence of acute transseptal flow by Doppler ICE when compared to the FO. Potentially, the IL transseptal site may reduce later IASD complications post-cryoballoon procedures.