Complications of biventricular pacing
St. Peter's Hospital, Chertsey, Surrey, UK
Received 3 May 2004; accepted 24 May 2004.
* Correspondence: Dr. Vince E. Paul, St. Peter's Hospital, Guildford Road, Chertsey, Surrey KT16 OPZ, UK. Tel.: +44-1932-872000; fax: +44-1932-722841
vince.paul{at}asph.nhs.uk
Abstract
Biventricular pacing in patients with drug refractory heart failure is not without risk. In addition to those complications associated with conventional pacing, there are also problems with left ventricular lead insertion using the preferred transvenous approach.
Key Words: Complications • Biventricular pacing • Transvenous • Perforation • Infection
Resynchronisation therapy with biventricular pacing is increasingly accepted as therapy for patients with drug resistant heart failure. The complications of device implantation include those associated with conventional pacing and those specifically related to the positioning of a lead within a branch of the coronary sinus. These complications include unsuccessful implantation, phrenic nerve stimulation, coronary sinus dissection or perforation, and embolic phenomena.
Complications common to all
Complications associated with conventional pacing may occur during biventricular pacing. These include:
- Localised/skin infection
- Systemic infection secondary to infected pacing box or lead
- Bleeding
- Haematoma
- Lead displacement
- Equipment failure i.e. fractured pacing wire, faulty pacing box
- Pneumothorax
Standard predictors of operative complications apply, those being degree of heart failure, the surgical environment, diabetes and the duration of the procedure. At least two of these apply to all patients requiring resynchronisation therapy. Although with experience the procedure times reduce, even in the best hands implantation of the left ventricular lead may be time consuming, contributing to an increased infection risk.1
Implantation of the biventricular pace maker
In the initial studies of biventricular pacing, the right atrial and right ventricular leads were inserted via the standard transvenous approach, but the epicardial left ventricular lead was placed surgically via thoracotomy or thoracoscopically. These approaches required a general anaesthetic and carried a significant morbidity and mortality.
In 1998, Daubert et al.2 introduced the preferred method of left ventricular lead insertion using the transvenous approach. The precise location of the lead is crucial and ideally the mid left ventricular cavity in a lateral or posterolateral vein.3 The use of guiding catheters within the coronary sinus and the use of purpose designed leads have increased success rates and ability to reach the target vessel.
The requirement to position a lead in a branch of the coronary sinus and the techniques required to achieve this account for the additional complications and significant failure rate seen with biventricular pacing.
In the Multisite Stimulation in Cardiomyopathies (MUSTIC),4 left ventricular pacing was achieved in 92% of 67 patients and a targeted lateral wall vein was reached in 80%. The mean LV pacing threshold was 1.4±1.1 V. Complications included: early dislodgement of the LV lead in eight patients; two developed loss of LV capture at 6 month follow up.
In the Multicenter Insync Randomised Clinical Evaluation5 (MIRACLE)6 study, an implant success rate of 93% was reported although data on the pacing site was not presented. Complications encountered with this study included: perforation or dissection of the coronary sinus in 2.1%. No other complications were reported and the Insync Resynchronisation pacing system over the short term exceeded performance and safety criteria.
This implantation success rate in the Contak CD study is reported as 91% with an average LV pacing threshold of less than 2 V. The left ventricular pacing sites were: 54% in the lateral cardiac vein, 32% in the anterior cardiac vein and 14% in the posterior vein. Complications included perforation or dissection of the coronary sinus in 1.8% and extra cardiac stimulation of 1.6% (Figs. 1–3).
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A further study carried out in Germany7 enrolled 84 patients all of whom were implanted with a cardiovertor–defibrillator incorporating cardiac resynchronisation therapy. This study tabulated their complications as:
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As can be seen from the complications encountered in the studies, these problems can arise at the time of implant or at follow up.
Implant failure
Failure of implantation remains a real issue occurring in 4–10% of cases. Some centres attempt to reduce the incidence by pre-assessment of the coronary venous anatomy. In a small percentage of patients the venous anatomy itself may preclude successful implants by conventional routes. Such problems include absence of an appropriate lateral branch and anomalous drainage into the left atrium. In other cases there may be actual stenosis or a vessel of insufficient calibre obstructing passage. Coronary vein angioplasty has been reported as safe and effective in these situations although experience is currently limited.9
The major technical problem encountered is the inability to locate and enter the coronary sinus with the guiding catheter. Anatomy may be distorted in dilated hearts increasing the difficulty. Occasionally once the coronary sinus has been located or even entered with a guide wire it remains impossible to advance the guide catheter because of acute angulation or stenosis. Once the guide catheter has engaged the coronary sinus it is rare, with the newer technologies available, not to be able to enter the target branch vessel. Stability in desired position, particularly during guide catheter removal may be an issue. Various delivery systems are available and utilise different methods of removal (splitting, slitting and over the lead removal). The lead displacement risk is dependent upon several factors including; the position and type of lead used, the angle of the opening of the coronary sinus and the experience of the operator.
Potential procedural complications
The potential procedural complications relate largely to the use and manipulation of the guiding catheters within the heart.
Electrical trauma occurs in up to 5% of all implantations. Guide catheter manipulation may cause a right bundle branch block pattern, and in those patients with existing left bundle branch block, may result in ventricular stand still. In preparation for this the right ventricular lead is usually positioned first.
Dissection or even perforation of the coronary sinus may occur due to manipulation of the guide sheath, a diagnostic catheter, occlusion balloon or the pacing wire. Most commonly this results in minor asymptomatic staining of the coronary sinus but very rarely has resulted in pericardial effusions and tamponade. The dissection in the low pressure venous system is generally well tolerated and does not appear to cause permanent disruption of the anatomy. On occasions lead exit into the pericardium may occur although this in itself may not preclude successful left ventricular pacing (Figs. 4 and 5).
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A further problem with the use of guide catheters is the tendency to form thrombus within the lumen and hence the risk of emboli. Although this undoubtedly must occur there are no reported cases of significant problems. Thrombus may also form on the angioplasty wires used to deliver some leads. The often inadequate nature of the haemostatic valves supplied makes continuous flushing less effective than desirable and occasionally anticoagulation is required. The guide catheter also clearly increases the risk of air emboli (Fig. 6).
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Once the lead has successfully been delivered to the target vein, problems may still occur with sensing and stimulation. Poor R wave is less commonly a problem than with right sided leads but far field sensing of right ventricular or left atrial activity may ocur and has been reported as potential problems in up to 11% of patients. This may result in a pace maker mediated tachycardia and had particular relevance in some of the earlier ICDs.
Despite good lead positioning, high threshold are often obtained on the left ventricular lead. Pacing thresholds up to 3 V are generally considered acceptable particularly given that the patients are generally not pacing-dependent, have back-up pacing from the right ventricular lead and have a poor prognosis.
In inadequately positioned left ventricular leads, inadvertent stimulation of the left atrium or the right ventricle may occur. More commonly it is stimulation of the phrenic nerve that causes difficulties and indeed is a major cause for failure at a given position. This is most commonly seen in the target posterior and postero-lateral branches of the coronary sinus. It is very variable with posture and respiration, and therefore may only become evident once the patient is off the table. It is rarely seen in the branches of the great cardiac vein. In some circumstance the presence of phrenic stimulation may be acceptable provided there is an adequate margin between cardiac and phrenic nerve threshold (generally threefold difference). More commonly it is necessary to reposition the lead more proximally within the vessel, in a different distal sub-branch or in a different vessel altogether.
Strategy for failure
Even in the most experienced hands occasionally the procedure is technically impossible. Certain strategies can be employed in these circumstances such as, different technology, a different operator or better visualisation with the concurrent use of transoesophageal echocardiography.10 Occasion does arrive when the operator has to resort to a surgical approach, with a limited thoracotomy or thoracoscopy, but these procedures have additional risks. Endocardial access of the left ventricular pacing lead can also be achieved via a transarterial or transeptal approach. This technique has not, to date, been studied in detail.11
Limited thoracotomy has the advantages of predictable procedure time and success rate. Direct visualisation may allow avoidance of phrenic nerve stimulation. The disadvantages are that it is an invasive procedure, often involving a hybrid approach and a prolonged hospital stay. It may also be difficult to position the lead sufficiently posterior for effective therapy. Complications, especially in this cohort of patients, are common and the financial cost is higher.
Thoracoscopy is less invasive than a limited thoracotomy. It is only done in a small number of centres and again it is usually a hybrid procedure, occasionally reverting to open surgery. A recent small study12 achieved ventricular resynchronisation in a minimally invasive fashion using a robotically assisted left ventricular epicardial approach, with good results. Efficacy in reaching the best haemodynamic position has yet to be confirmed.
Problems of re-intervention
Re-intervention after a failed transvenous approach or a dislodged left ventricular lead is not without its additional complications. There may be a change in the coronary sinus anatomy, a venous thrombosis, development of collateral vessels or fibrotic restrictions. There is rarely a problem in the lead extraction.
Conclusion
Cardiac resynchronisation therapy with biventricular pacing is increasingly used in patients with drug resistant heart failure. New centres are commencing the therapy and as such an awareness of problems and complications is important.
Complications of biventricular pacing are quite common but generally benign. Improved technology and skilled operators is reducing the incidence of problems.
Technical failure is the commonest problem, but alternative methods do exist and should be considered when failure occurs.
Footnotes
Collated from the presentation at the `First International Symposium and Workshop on Cardiac Resynchronisation Therapy', Bad Oeynhausen, September 18–19 2003.
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