Interventions for coronary sinus access with an obstructing Thebesian valve

Key Teaching Points.

• •Catheter access to the coronary sinus can be obstructed by variations in Thebesian valve anatomy, including near or total occlusion, and may prevent successful catheter ablation of arrhythmias.
• •Open surgical access to the coronary sinus to access the bypass tract is safe and feasible, but more invasive than catheter-based approaches.
• •A novel minimally invasive approach to breach an obstructing Thebesian valve is use of a radiofrequency ablation catheter to directly perforate the obstructing membrane using thermal energy.

Introduction

Access to the coronary sinus (CS) for mapping or ablation or to perform vein of Marshall ethanol injection is helpful or even necessary for treating certain cardiac arrhythmias, including bypass tracts, atypical left atrial flutters, and atrial fibrillation.^1,2 The CS Thebesian valve (ThV) anatomy can have a multitude of variants that can make catheter access to the CS difficult or impossible, especially ThV folds, fenestrations, or complete obstruction.^3,4 This case series demonstrates 2 distinct interventional strategies for accessing the CS in patients with an obstructive ThV for a successful electrophysiology (EP) ablation procedure.

Case report

Case 1

A 45-year-old woman with recurrent syncope, preexcited atrial fibrillation, and a posteroseptal accessory pathway (Figure 1A and 1B) was referred after 4 prior unsuccessful ablation procedures without accessory pathway elimination. The prior attempts included left-sided mapping and ablation attempts using both transseptal and retrograde aortic approaches, as well as subxiphoid percutaneous epicardial mapping. Because in each case the CS was unable to be cannulated, a levophase coronary angiography was performed demonstrating an occlusive ThV and CS diverticulum (Figure 1C). Percutaneous epicardial mapping showed a continuous atrial and ventricular electrogram (Figure 1D) over the CS diverticulum; however, radiofrequency ablation at this site was unsuccessful.

Figure 1.

Surgical access of a coronary sinus for ablation of a diverticulum accessory pathway. A: Electrocardiogram with preexcitation. B: Induction of atrial tachycardia and atrial fibrillation. C: Levophase coronary sinus (CS) venogram showing obstructive CS ostium and diverticulum. D: Continuous electrogram in the epicardial space over the diverticulum. E–G: Surgical access for cryoablation and coronary sinus reconstruction. H: Loss of preexcitation postablation. LA = left atrium; LAO = left anterior oblique.

The patient was referred for open chest cardiac surgery. Figure 1E shows the diverticulum with dilated epicardial coronary veins. A CS valvuloplasty was performed, allowing successful cryoablation of the bypass tract in the diverticulum, and a new CS patient ostium was reconstructed (Figure 1F and 1G). The electrocardiogram postsurgery showed elimination of preexcitation (Figure 1H).

Case 2

A 72-year-old man with persistent atrial fibrillation despite 2 prior pulmonary vein isolation procedures was referred for redo ablation for symptomatic atypical atrial flutter (Figure 2A). During previous ablation attempts, CS cannulation had been unsuccessful. An endocardial posterolateral mitral ablation line was attempted to a treat a mitral flutter during those procedures, but mitral block was not achieved.

Figure 2.

A: Electrocardiogram with atypical atrial flutter with variable AV conduction. B: Activation and bipolar voltage (0.05–0.50 mV) maps of the clockwise mitral flutter with significant slowing (white arrows) in the posterolateral mitral isthmus at the site of a previous posterior mitral ablation. PA = posteroanterior.

During the third procedure, after transseptal puncture, activation mapping of the left atrium revealed a mitral flutter with a possible epicardial connection over the previously created posterolateral mitral line (Figure 2B). The CS was resistant to cannulation despite multiple attempts from both a femoral approach (inferiorly) and internal jugular approach (superiorly) using deflectable catheters, sheaths, guide wires, and guide catheters. A contrast injection through a deflectable sheath positioned in the CS ostium area guided by intracardiac echocardiography (ICE) revealed a completely obstructed CS ostium owing to an occlusive ThV (Figure 3). Since endocardial reablation of the previously created line did not affect the tachycardia and entrainment from a catheter placed in the CS ostium was found to be close to the circuit (postpacing interval minus tachycardia cycle length of +15 ms), an attempt to gain access to the CS using radiofrequency energy was performed.

Figure 3.

Venography through a guiding sheath in left anterior oblique view of the coronary sinus ostium showing the obstructing Thebesian valve and a decapolar catheter tenting the membrane.

For that, the 3.5 mm irrigated radiofrequency ablation catheter was advanced as deep as possible on the superior portion of the ThV. Guided by fluoroscopy, ICE, contact-force sensing, and electroanatomic mapping, radiofrequency ablation (35 watts) was applied and the catheter gained CS access within 5 seconds of the application by presumably perforating the valve (Supplemental Video 1). The sensed contact force during that radiofrequency application ranged from 8 to 16 g. After the CS was accessed, venography revealed a dilated proximal CS. The distal branches of the CS were not dilated. The vein of Marshall was then cannulated and ablated via alcohol injection and repeat endocardial and CS ablation created bidirectional block on the mitral annulus and no further arrhythmias were inducible.

Discussion

Inability to access the CS can result in unsuccessful catheter-based ablation procedures. In this case series we show 2 different solutions to allow for intra-CS ablation necessary to treat symptomatic arrhythmias. In the first case, performed 2 decades ago, the only available solution was a surgical approach, which—while successful—was significantly more invasive than a percutaneous procedure. In the second case, a minimally invasive approach was employed using direct radiofrequency ablation to cross an imperforate ThV. This was safely employed given the use of contact force sensing, fluoroscopy, ICE, and electroanatomic mapping to understand the catheter trajectory as it advanced. This method, using modern tools used in everyday EP procedures, allows for an efficient and minimally invasive approach to difficult CS access from an obstructive or nearly obstructive ThV.

The ThV is a remnant of the embryologic sinoatrial orifice (or “valve”) present in 60%–80% of human hearts.3, 4, 5, 6 It arises from the inferior part of the right side of the opening of the sinus venosus into the atrium, which forms the ThV and the Eustachian valve; the right-superior part forms the smooth-walled part of the right atrium, and the left side fuses with the septum secundum.⁷ Along with size and takeoff angle of the CS, the presence of a ThV is one of the main obstacles to CS cannulation, which in large cardiac resynchronization therapy trials failed in 5%–12% of cases.³

The prevalence of a ThV impeding access to the CS has been studied in recent autopsy series. Mak and colleagues³ defined a “potentially complicating” ThV as one that covered “>75% of the ostium, a fibrous, fibromuscular, or muscular composition, and devoid of fenestrations” and reported its presence in 16% of 75 autopsied human hearts. Using this definition, the autopsy series of Hołda and colleagues,⁴ Sławek-Szmyt and colleagues,⁵ and Shanthini and Suma⁶ reported a prevalence of 14.3%, 11%, and 7%, respectively. ThV that covered the entire CS ostium (as in our case) was reported in 2.6%, 2.0%, and 4% of cases in those series.4, 5, 6

Since CS cannulation is critical to the success of multiple device and ablation procedures, techniques to deal with obstructing CS ThV should be of broad interest to the EP community. To our knowledge, this is the first report of access to the CS ostium by radiofrequency ablation of the imperforate ThV with a standard EP catheter. In partially obstructed ThVs, it is most common for the cranial portion of the CS ostium to be the unobstructed portion, so it is reasonable to focus attempts on passing catheters across the ThV along the roof of the CS to increase the chance of success.⁸ Given the proximity of the roof of the CS ostium to the atrioventricular (AV) conduction system, great care must be taken to ensure there is adequate distance between the ablation catheter tip and the apex of the triangle of Koch near the His bundle and AV node fast pathway region, along with monitoring for junctional beats when ablating in sinus rhythm and any lengthening of the PR interval to avoid the risk of iatrogenic AV block.

Disclosures

TM has received consulting and speaking honoraria from Abbott, Inc, and Biosense Webster, Inc, and research support from LuxMed Systems. AD has received speaking and consulting honoraria from Abbott, Inc, Biosense Webster, Inc, and Biotronik, Inc, and research support from Medtronic and Abbott Inc. The remaining authors report no financial disclosures.

Appendix. Supplementary Data

Supplemental Video 1

Radiofrequency ablation through the Thebesian valve visualized on the electroanatomic mapping system. A) Posteroanterior view, B) left anterior oblique views of the moment of radiofrequency initiation and ablation catheter perforation of the Thebesian valve after 1.5 seconds of radiofrequency application.