The European Society of Cardiology
Implantation: tips and tricks – the cardiologist's view
a Department of Cardiology, Heart Centre North Rhine-Westphalia, Ruhr University Bochum, Bad Oeynhausen, Germany
b Department of Thoracic and Cardiovascular, Surgery, Heart Centre North Rhine-Westphalia, Ruhr University Bochum, Bad Oeynhausen, Germany
Received 3 May 2004; accepted 24 May 2004.
* J. Vogt, MD, Department of Cardiology, Heart Centre North Rhine-Westphalia, Ruhr University of Bochum, Bad Oeynhausen, Germany. Tel.: +49-5731-971258; fax: +49-5731-972194
akohlstaedt{at}hdz-nrw.de
Abstract
Since the development of the first epicardial left ventricular pacemaker leads, the design of transvenous coronary leads has progressed tremendously. Due to the safe access to the target region independent of previous surgical interventions and a low morbidity, the transvenous placement has become the method of choice.
Catheterization of the coronary sinus is required to place the coronary venous lead. The most difficult anatomical situation is the pipe-shaped coronary sinus. A systolic compression of the proximal coronary sinus may be associated with a risk of dissection particularly in elderly patients. Access to the coronary sinus is best made by two combination systems with a steerable electrophysiology catheter or a telescoping inner catheter. Furthermore, special guiding catheters for the access from the right subclavian vein particularly to upgrade right-sided pacemakers and ICD systems have been developed. Complex, i.e. sharp-angled and corkscrew veins may only serve as target veins, if sharp-angled angiography catheters and over the wire technique are used. The pseudobipolar stimulation against the ring of the right ventricular lead has been developed for the safe function of a CRT defibrillator. This design is associated with an anodal stimulation of the right ventricle, which might result in clinical non-responders especially in patients with optimal left ventricular pacing mode (30%). For this reason, coronary sinus leads should basically be designed as bipolar leads.
Key Words: Resynchronization • Coronary venous lead • Coronary sinus access • Complex coronary veins • Pseudobipolar anodal stimulation
Introduction
Results from randomized trials and the cardiac resynchronization register reveal clinical benefit of resynchronization therapy to patients with severe heart failure. This inspired several groups as early as the mid-90s to implant conventional pacemaker leads into coronary sinus tributaries for biventricular pacing via a Y-connector.1 Since then, the design of transvenous guiding catheters and transvenous coronary vein leads has progressed tremendously.2 In cases of a difficult coronary vein anatomy, cardiologists may disagree among themselves and with surgeons regarding the most effective approach for implantation. Some centres continue to use a "mini-thoracotomy" to secure special pacing leads onto the epicardium in cases with an unsuccessful lead placement or even primarily, if the coronary vein anatomy appears to impede lead placement. From today's vantage point one should, however, realize that leads placed through such a "mini-thoracotomy" can be positioned only suboptimally, e.g. more anterolateral between the first and second diagonal branch and the left anterior descending coronary artery. This location is disadvantageous because the posterolateral target region is not reached. To gain access to the posterolateral target region parallel to the obtuse marginal branches of the circumflex coronary artery, the heart needs to be rotated, a manoeuver requiring a much larger posterolateral thoracotomy. This approach is more stressful as it requires single lung ventilation and is frequently complicated by pleural effusions during the recovery period. The morbidity is thus far beyond that of the transvenous approach. Screw-in type active fixation leads are not particularly well suited because of significant incidence of increasing pacing thresholds. The maximal invasive method may be limited further by the fact that epicardial adhesions subsequent to previous cardiac surgical procedures limit satisfactory lead positioning in the typical target region.
The rapid development of suitable coronary vein leads, with special emphasis on over-the-wire leads, was therefore pursued by cardiologists. A combination of surgical, interventional, and electrophysiological methods is therefore the state of the art technique for the implantation of coronary vein leads.3
From a cardiologist's viewpoint, three important aspects regarding coronary vein lead implantation and pacing should be focussed on:
- access to the specific anatomical variants of the coronary sinus,
- handling of complex target vein anatomies,
- effect of the pseudobipolar configuration on the pacing mode.
Coronary sinus access
In patients with severe heart failure and massive ventricular and sometimes also atrial, particularly right atrial dilatation, the coronary sinus is best visualized in the 40° LAO projection without rotation as a very large vein, the ostium of which overlies the lower third of the left ventricular contour (Fig. 1). This projection will usually show the ostium in direct proximity to the anterior contour of the vertebral bodies or 1–2 cm more anteriorly. The anatomy in the posteroseptal region, including the superior/inferior location of the coronary sinus ostium, tends to be highly variable. The straight or slightly inferiorly curved coronary sinus ostium projects over the left ventricular contour and can easily be cannulated by advancing the guiding catheter during counter-clockwise rotation. If the ostium is located more superiorly, towards the mid-atrial septum, a more central area of Koch's triangle, it may be especially difficult to identify the ostium without resorting to angiographic contrast.
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The most difficult situation for coronary sinus ostium cannulation is referred to as the "pipe-shaped" ostium, which is a narrow pipe mouth pointing cranially before the remainder of the coronary sinus turns inferiorly at an angle and continues in the cranio-lateral direction (Fig. 2).
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The most difficult obstacle for cannulating the coronary sinus tends to be a very tight upward angulation next to a very low posterior venous tributary. This angle may be so acute that an antero-posterior projection plus radiographic contrast injection are required to allow for turning the catheter away from the wall and into the coronary sinus opening. Some cases additionally require a steerable electrophysiologic catheter with a very small bending radius, before the acute angle can be negotiated and a rail created for passing the guiding catheter (Fig. 3).
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Another technically demanding variation of the coronary sinus morphology with a potential for higher complication rates is pronounced systolic compression of the posterolateral-posterior coronary sinus segment, especially in the elderly. It is very easy to advance the guiding catheter far into the subintimal plane without any noticeable resistance. Extensive dissection of the entire coronary sinus may result. Fortunately, this type of dissection is directed against the downstream flow, usually does not result in perforations and generally heals without sequelae within a couple of weeks.
After more than 450 implantations, we recommend to use one of two different systems matched to the individual take-off angle and shape of the coronary sinus ostium. Our standard system comprises a pre-shaped coronary sinus guiding catheter (Attain system, manufactured by Medtronic, Inc.) in combination with a 6 Fr steerable electrophysiology catheter with a fixed D-curve (manufactured by Biosense Webster) (Fig. 4). By advancing the electrode tip of the electrophysiology catheter directly beyond the ostium of the guiding catheter, deflection of the steerable catheter allows to elevate or lower the tip of the guiding catheter to an extent sufficient to intubate even difficult variations of the coronary sinus by quick counter-clockwise rotation. The use of a 9 Fr guiding catheter combined with a 6 Fr steerable electrophysiology catheter makes the catheter side port valve available for injecting radiographic contrast agents to visualize the coronary sinus ostium in such difficult anatomical situations. A steerable electrophysiology catheter alone permits coronary sinus cannulation in demanding circumstances and provides a safe guide to advance the guiding catheter into the coronary sinus. Steerability of the electrophysiology catheter will also allow its uncomplicated and atraumatic placement in the proximal segment of the great cardiac vein where it can serve as a rail to place a guiding catheter far down into the coronary sinus. This combination guarantees the highest flexibility for each particular vascular anatomy.
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We were involved in the development of a second guiding catheter with adjustable curvature. This consists of a stiffer pre-shaped 8 Fr guiding catheter, which contains a second telescoping 6 Fr catheter (Fig. 5). Moving the inner catheter back and forth within the area of the tip of the outer guiding catheter changes the curvature of the outer catheter to match the coronary sinus anatomy and facilitates cannulation. If necessary, contrast agent may be injected through the slightly curved inner catheter to visualize the coronary sinus ostium. Additionally, the inner catheter provides a rail for advancing the guiding catheter into a far distal position of the coronary sinus. To permit bilateral subclavian vein access, we initiated production of special curvatures (Rapido Guiding Catheter, Guidant). With these new curvatures, clockwise rotation easily permits intubation of the coronary sinus ostium via the right subclavian vein. No additional torque needs to be applied to the catheter during the intervention. When the guiding catheter is withdrawn over the lead at the end of the implantation, the tip of the guiding catheter does not have a tendency to flip or rotate during pull-back. This prevents lead displacement.
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The inner catheter of the Rapido System can also be used to cannulate coronary venous tributaries directly and to deliver contrast agent into these target vessels (Fig. 6).
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Advancing the guiding catheter as closely as possible to the ostium of the target vein is the most effective technique for quick coronary vein lead placement or guide wire positioning utilizing the over-the-wire method. This position is either reached via a rail such as the inner catheter of the Rapido System or a steerable electrophysiologic catheter. Another option is the use of a soft 0.035 in. wire. The latter approach may, however, make the sharp edge of the guiding catheter catch an obstacle inside the coronary sinus.
Management of complex target veins
Especially veins with a posterior ostium are often tortuous in their proximal segment and form an acute angle with the coronary sinus. Frequently, their ostium is in close proximity to the coronary sinus ostium. When using the over-the-wire technique, this particular anatomy hampers introduction of the guidewire into a complex-shaped ostium. Direct intubation with the guiding catheter is then a very helpful technique. Selective intubation of these veins is first started by advancing the guiding catheter into a more distal segment of the coronary sinus, before the catheter tip is straightened by deflecting the steerable electrophysiology catheter, whose tip is directly at or protruding slightly from the tip of the guiding catheter. The entire unit is then pulled back under counter-clockwise rotation within the plane of the posterior venous ostium. This motion makes the tip of the steerable electrophysiology catheter slip into the venous ostium (Fig. 7). After successful intubation, contrast injection visualizes the entire course of the tortuous vein so that the steerable electrophysiology catheter can be carefully advanced along the vessel's course while maintaining counter-clockwise torque. If the vein exhibits pronounced corkscrew-like proximal tortuosities, it may be necessary to also rotate the electrophysiology catheter in counter-clockwise direction while keeping it slightly flexed, before advancing it deeply into the venous tributary. When the electrophysiology catheter assumes a position far down the vein, it can be easily used as a rail for advancement of the guiding catheter into the mid or proximal section of this particular vessel. Subsequently, contrast agent can be injected before a lead is atraumatically advanced into the target area of the vein, either directly or using the over-the-wire technique in case the vessel caliber is small.
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Especially target veins in the lateral section of the coronary sinus tend to have a take-off too acute to be passed with a soft or stiff coronary wire. We addressed this issue by developing a special technique in the late nineties.4 For this technique, which facilitates intubation, a 4 Fr or 5 Fr coronary angiography catheter, most often an internal mammary catheter with a tight customized bend, is positioned distal to the venous ostium, best protected by a soft guide wire. After the guide is pulled back and contrast injected, the pre-shaped angiography catheter is easily rotated into the acute take-off of the venous tributary (Fig. 8). Selective angiography of the target vein may then be accomplished through the internal mammary catheter. Subsequently, a 0.014 in. coronary wire is advanced through this catheter and the catheter exchanged by the over-the-wire lead. Stretch of the acute venous take-off by the coronary wire will often significantly facilitate advancement of the over-the-wire lead beyond the ostial angle of the target vein.
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If corkscrew tortuosities and acute take-off angles of the only acceptable posterolateral target veins make intubation fail, a coronary wire can be used to place a Multifunctional Probing catheter® (manufactured by Boston Scientific) into the proximal vein segment. This particular catheter is equipped with a monorail and an over-the-wire lumen as well as a marker close to the tip. Use of this multifunctional catheter as a rail for the coronary wire facilitates pushing and torquing of the guidewire, that can then be directed much easier through very tortuous vein segments: Contrast agent can be injected through the second over-the-wire lumen to verify proper placement, and a second stiffer coronary wire can be advanced into the vein as a more effective rail for lead positioning.
Impact of pseudobipolar lead configuration and pacing mode
While testing the acute haemodynamic response to resynchronization in more than 400 cases, we learned that approximately 1/3 of the responders had a significantly higher pulse pressure increase with just left ventricular pacing than with biventricular pacing. Adding right ventricular apical stimulation completely reversed the beneficial effect of resynchronization in some patients. To find the most suitable implant configuration, we attempted isolated left ventricular stimulation in these patients. While determining right ventricular pacing thresholds as part of our follow-up studies on patients under resynchronization therapy, a positive R wave identical to left ventricular stimulation and dependent on the shortening of the AV delay was found in the right precordial V leads of the paced ECG. This was due to unremarkable anodal left ventricular pacing.
Since defibrillator implantation made unipolar stimulation obsolete, left ventricular resynchronization devices were designed to utilize a pseudobipolar configuration: tip of the coronary vein lead against ring or coil of the right ventricular lead (Fig. 9). Depending on the pacing amplitude of the left ventricular coronary vein lead, a specific threshold for anodal co-stimulation of the right ventricle can be found (Fig. 10). While lower amplitudes cause pure left ventricular pacing, amplitudes at the usual margin of safety will begin to make the ECG look identical or nearly identical to pure biventricular pacing.
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Modern resynchronization stimulators allow unipolar left ventricular pacing against the can of the device. Patients who only experience a predominant and significant response to left ventricular stimulation and require combined defibrillators/resynchronization units should be implanted with bipolar coronary vein leads if at all possible.
In summary, the technical prerequisites and the training required for interventionalists implanting biventricular systems demonstrate that the procedure may be very complex and technically demanding.4,5 It is therefore desirable that surgeons and interventional cardiologists or cardiac electrophysiologists cooperate closely or join forces when performing implantations.
References
- Daubert JC, Ritter P, Le Breton H, et al. Permanent left ventricular pacing with transvenous leads inserted into the coronary veins. PACE. 1998;21:239–245
- Hansky B, Vogt J, Güldner H, et al. Left heart pacing – experience with several types of coronary vein leads. J. Intervent. Cardiac. Electrophysiol. 2002;5:71–75
- Auricchio A, Klein H, Tockman B, et al. Transvenous biventricular pacing for heart failure: can the obstacles be overcome. Am. J. Cardiol. 1999;83:136D–142D[CrossRef][Web of Science][Medline]
- Vogt J, Hansky B, Lamp B, et al. Biventricular stimulation in heart failure patients with ICD indication – first experience with a new implantable cardioverter/defibrillator. PACE. 2000;23:57
- Hansky B, Lamp B, Minami K, et al. Coronary vein balloon angioplasty for left ventricular pacemaker lead implantation. J. Am. Coll. Cardiol. 2002;40:2144–2149
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