Traversing and Dilating Venous Collaterals: A Useful Adjunct in Left Ventricular Electrode Placement

   ABSTRACT: In patients receiving cardiac resynchronization therapy (CRT), the left ventricular electrode cannot always be positioned in the preferred lateral or posterolateral locations due to technical factors and anatomic variations in the coronary sinus. Recent reports also suggest that CRT outcomes are improved by pacing the site of latest dyssynchrony and accessing these regions is not always possible. We report the utility of applying a technique described in the interventional literature over the past 3 years, effectively traversing and dilating collateral channels. Our patients demonstrated either no venous targets in the optimal location, or problems accessing this location using a antegrade approach. Subsequently, collaterals supplying this region were traversed with a guidewire using a retrograde approach and dilated with a balloon catheter. In the first case, the pacing electrode was then advanced in similar fashion and successfully positioned in an ideal lateral location. In the second case, the retrograde guidewire was captured with a vascular snare and pulled into a second guiding catheter, allowing appropriate dilatation and stenting of a problematic proximal venous stenosis with resultant facile placement of the pacing electrode. This technique offers a potential alternative to patients with challenging venous anatomy as a method to facilitate optimal CRT outcomes. J INVASIVE CARDIOL 2010;22:E93–E96    Key words: coronary anomaly, cardiac resynchronization therapy    The evolution of cardiac resynchronization therapy (CRT) has resulted in significant benefit to patients with prolonged QRS duration and resistant heart failure.^1,2 In most cases, left ventricular (LV) stimulation is accomplished via the coronary sinus and its tributaries. Precise coronary sinus electrode placement in a preferred location can be problematic due to technical and anatomic features. Multiple reports have addressed this issue and demonstrated outcome benefit in challenging situations when the operator utilizes equipment and techniques designed for coronary and peripheral intervention.^3–7 In this article we demonstrate the utility of a helpful approach used in coronary artery intervention when resistant total occlusions are present, effectively traversing and dilating collateral channels.^8–10 By crossing the venous collaterals in our patients, we were able to successfully place the LV electrode in an ideal location despite difficulties in accessing the appropriate location due to problematic venous anatomy.    Case 1. A 72–year-old male was admitted for placement of a CRT defibrillator in the setting of prolonged QRS duration and NYHA class III heart failure on appropriate medical therapy. He had a history of hypertension, prior coronary bypass surgery, and left ventricular dysfunction. His twelve-lead electrocardiogram demonstrated prolongation of the QRS interval, measuring 152 msec, and his ejection fraction by echocardiogram was 0.20. The coronary sinus was engaged with standard technique and venography in the LAO projection demonstrated no suitable lateral or posterolateral venous tributaries (Figure 1, arrow, left panel). A large posterior branch was selectively engaged with a guiding catheter (Medtronic, Inc., Minneapolis, Minnesota), aided by a 0.035-inch angled-tip hydrophilic guidewire (Terumo Medical Corporation, Tokyo, Japan) and a #5 Fr IMA diagnostic coronary catheter (Cook Group, Inc., Bloomington, Indiana). It was felt that placement of the left ventricular electrode in this branch itself reduced the likelihood of an effective response to CRT due to its proximal, posterior location. However, selective venography did demonstrate several small-to-moderate sized distal branches extending laterally (Figure 1, right panel), with sub- sequent collateral filling of the lateral wall. The first such branch was selected with a 0.014-inch PT Graphix intermediate hydrophilic guidewire (Boston Scientific Corporation, Natick, Massachusetts) and this successfully traversed the distal aspect of the branch and with further effort, manipulated through the collateral channels (Figure 2, arrows, left panel) re-entering into the main coronary sinus. An Attain model #4193 left ventricular pacing electrode (Medtronic) was then advanced over the guidewire, but could not be positioned beyond the proximal segment of the venous branch. The electrode was then exchanged for a 2.5 x 30 mm Maverick balloon catheter (Boston Scientific Corp.) and this was advanced into the distal branch and then the collaterals. Despite mild resistance, the catheter was success- fully passed through the collaterals towards a more basal location. Sequential, gradual inflations were performed to 12 atmospheres (Figure 2, right panel) and it was gradually withdrawn. Subsequently, the electrode catheter was advanced with ease through the dilated collateral channels, achieving a lateral location (Figure 3). Capture data was 1.4 volts at 0.5 msec and no diaphragmatic stimulation was observed. The procedure was then completed and the patient discharged in stable condition.    Case 2. A 69-year-old female was admitted for implantation of a CRT defibrillator. She had a history of a non-ischemic cardiomyopathy with class III heart failure on medical therapy. Complete left bundle branch was present with a QRS duration of 172 msec. Echocardiographic study demonstrated an ejection fraction of 10%. The coronary sinus was engaged and venography in the LAO projection demonstrated a moderate-sized lateral branch with a significant “corkscrew” steno- sis present in its proximal segment (Figure 4, arrows, left panel). This stenosis could not be traversed despite attempts with a series of 0.014-inch coronary guidewires. Selective venography in a more proximal large posterolateral branch felt not to be ideal for electrode placement primarily demonstrated retrograde filling of a more preferable target lateral branch via venous collaterals (Figure 4, right panel). Two 0.014-inch hydrophilic coronary guidewires (PT Graphix, Boston Scientific Corp.) were advanced through a suitable collateral into the lateral branch and then the main coronary sinus. A series of balloon inflations were performed with 2.5 mmand3.0mmx30 mm balloon catheters (Maverick), but a severe, isolated focal stenosis in the collateral could not be dilated despite high- pressure balloon inflations to greater than twenty atmospheres, before and after placement of a 3.0 mm x 16 mm stent (Liberté, Boston Scientific Corp.) (Figure 5, arrow, left panel). The second guidewire had been left in place during inflations to utilize the forced focus technique. This stenosis impeded advancement of a pacing electrode into the lateral branch (Attain Model #4193, Medtronic). An alternative approach was then implemented with placement of a second guiding catheter into the main coronary sinus and capturing of one of the retrograde guidewires utilizing a vascular snare (Amplatz Goose Neck Snare, ev3 Endovascular, Inc. Plymouth, Minnesota) (Figure 5, arrow–right panel). The guidewire was then pulled back externally out of this second guiding catheter. Balloon angioplasty with a 3.0 mm x 30 mm balloon catheter and placement of a 3.0 mm x 16 mm coronary stent were then performed at the site of the proximal “corkscrew” stenosis. Anterograde advancement of the left ventricular pacing electrode through the second guiding catheter over the externalized guidewire was then easily performed to an optimal pacing location (Figure 6). Capture data were 1.2 volts at .5 msec. The procedure was then completed and the patient discharged in stable condition.    Discussion. In the presented patients, effectively traversing and dilating the coronary venous collaterals resulted in successful placement of the left ventricular electrodes in a preferred location. Multiple studies have reported the utility of applying interventional principles and equipment in the coronary venous circulation to accomplish optimal biventricular stimulation. Application of standard and hydrophilic coronary guidewires and diagnostic and interventional catheters have shown benefit. Early reports also demonstrated the utility of balloon angioplasty or venoplasty, generally applied in vessels with focal stenoses restricting electrode access.^3,4 Worley et al reported an early series of 35 cases in 2003 whereby interventional approaches were used, including dilatation of venous collaterals in 4 patients.⁵ A more recent article by the same author also highlighted the use of this technique in patients with severe stenoses limiting antegrade access to target vessels whereby a collateral approach provided retrograde vessel access.⁷ In addition to balloon angioplasty, more resistant lesions also respond to cutting balloon technology, the forced focus method utilizing a second parallel guidewire as was attempted in our second case, and coronary stent implantation.^6,11 Deployment of coronary stents parallel to the LV electrode has also been shown to be an effective method to prevent dislodgement. In an unique application of the trans-collateral technique, Soga et al recently described successful placement of a coronary sinus pacing electrode in a patient with total occlusion of the coronary sinus os by traversing a collateral pathway originating from the right atrial lateral wall.¹² The channel was initially visualized in delayed images of coronary arteriography and because of its mature size required no adjunctive balloon dilatation.    By crossing and dilating the venous collateral channels in the cases presented, we utilized techniques that have been reported with increasing frequency in the interventional literature. When resistant total occlusions are present in the coronary arterial vasculature, successful recanalization has been accomplished by dilating collaterals, generally in the septal regions, to allow retrograde access to the site of coronary occlusion.^8–10 To further facilitate this approach, new technology has been developed including very small caliber guidewires and balloon catheters, called channel dilators. In our patients, standard guidewires and balloon catheters were utilized to cross and dilate the collaterals, but it is conceivable that this newer equipment could be applied with advantage in CRT procedures. In some ways, the trans-collateral approach may be more facile in the venous circulation as in most patients a very dense web of interconnecting coronary sinus collaterals can be visualized, the venous system is generally more elastic when focal, resistant lesions are not present, and the concern with respect to outcomes of small perforations is less due to the low pressure in the venous circuits. Nonetheless, as collaterals are somewhat fragile vessels, much care should be taken in employing this technique with avoidance of aggressive guidewire manipulation or overexpansion of these small tributaries.    As our approach enabled us to effectively place electrodes in preferred left ventricular pacing locations, it probably enhanced both patients’ chances for an effective CRT response. As response rates to CRT are in the 70–80% range, placement of the LV electrode in the preferred lateral or posterolateral sites is generally at- tempted, but not always possible due to anatomic variations.^1,2,13 The importance of placing the electrode in the appropriate location was recently highlighted in the report of 244 CRT patients by Ypenburg et al.¹⁴ The ventricular segment with the latest activation or maximal dyssynchrony was identified by the 2D speckle tracking radial strain analysis and correlated with final electrode location. Overall, the majority of the patients (69%) showed the latest activation in the lateral or posterior segments. Improved outcomes of multiple parameters including mortality at six months were observed when the sites of maximal dyssynchrony and electrode placement were concordant. In contrast, patients in whom the electrode position was discordant from the echocardio-graphic location demonstrated significantly less benefit. The results of this study thus emphasized the need for placement of the LV electrode in an ideal posterior or lateral location, or when dyssynchrony data are available, the site of latest activation.    As the coronary venous circulation is different in every patient, large caliber branches are not always available to accept pacing electrodes in the preferred location. Potentially, collateral access to the appropriate sites in these situations may be available and channel dilatation carefully attempted. However, our report describes only two successful cases and may represent patients with particularly forgiving anatomy. Without more data it is uncertain how effective this approach will be in improving CRT implant procedures, but this approach should be considered in difficult anatomic situations with the potential to facilitate optimal CRT outcomes.

References

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_________________________________________________ From the Cardiovascular Institute of the South, Houma, Louisiana. The authors report no financial relationships or conflicts of interest regarding the content herein. Manuscript submitted September 24, 2009, provisional acceptance given October 6, 2009, final version accepted December 4, 2009. Address for correspondence: Dr. Richard P. Abben, Cardiovascular Institute of the South, 225 Dunn Street, Houma, LA 70360. Email: abben@msn.com