Europace Advance Access originally published online on September 4, 2008
Europace 2008 10(11):1308-1312; doi:10.1093/europace/eun245
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Cardiac resynchronization therapy
Primary failure of cardiac resynchronization therapy: what are the causes and is it worth considering a second attempt? A single-centre experience
Department of Cardiology, Brest University Hospital, CHU de la Cavale Blanche, Bd Tanguy Prigent, 29609 Brest Cedex, France
Manuscript submitted 13 June 2008. Accepted after revision 11 August 2008.
* Corresponding author. Tel: +33 2 98 34 73 91/92; fax: +33 2 98 34 73 93. E-mail address: marjaneh.fatemi{at}chu-brest.fr
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Abstract |
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Aims: Cardiac resynchronization therapy (CRT) has been validated as an effective treatment for patients with drug-refractory congestive heart failure and left bundle branch block. Failure of implantation of the left ventricular (LV) lead has been reported in 10–15% of patients. The goal of our study was to determine the causes of failure and the success rate following a repeat procedure by the same operators.
Methods and results: We reviewed our last 100 consecutive cases of CRT before July 2007. The procedure was considered as unsuccessful if it had to be interrupted before the placement of the LV lead in an appropriate position, because of patient’s haemodynamic status or if the procedure duration exceeded 3 h. Cardiac resynchronization therapy was unsuccessful in 10 patients (5 men, mean age: 72 ± 11 years). The causes of failure of CRT were as follows: no target vein other than the great cardiac vein (n = 5), coronary sinus dissection (n = 1), and a lateral vein too small to provide a stable location for the LV lead (n = 4). A second procedure was attempted in four patients and was successful in all cases.
Conclusion: In our study results, failure of CRT was observed in 10% of the patients. A second procedure can be attempted in a selected group of patients and is associated with a high success rate.
Key Words: Heart failure, Cardiac resynchronization therapy, Technical success
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Introduction |
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Cardiac resynchronization therapy (CRT) is currently recognized as an effective therapy for patients with symptoms of congestive heart failure (CHF) due to systolic left ventricular (LV) dysfunction and LV dyssynchrony.1
Reports from several randomized clinical trials confirm that CRT decreases symptoms, improves quality of life, and reduces mortality and hospitalizations for heart failure in patients with drug-refractory CHF with New York Heart Association (NYHA) functional class III–IV symptoms, low LV ejection fraction (LVEF 
35%), dilated LV, and a large QRS duration (
120 ms).2–4 Although this therapy has been accepted as safe and reliable, implantation of a CRT device remains a technical challenge. Even with the use of dedicated lead systems, it requires special skill to place the LV lead in a tributary of the coronary sinus with a stable pacing threshold and no diaphragmatic contraction. Previous reports indicate that the success rate of CRT varies from 85 to 95%5–7 and improves with the operators’ experience.7 In some patients, after a first unsuccessful attempt, CRT can be successfully achieved on a second procedure, but this has not been precisely evaluated in previous reports. The goal of our study was to determine the rate and causes of failure of the first CRT attempt and the success rate of a repeat procedure performed by the same operators with a long-term experience of CRT.
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Methods |
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We conducted a retrospective observational study on the last 100 patients referred to our institution for implantation of a CRT device between February 2003 and July 2007. All patients had moderate or severe CHF (NYHA functional class III or IV) lasting for more than 6 months, despite optimal medical therapy due to dilated ischaemic or non-ischaemic cardiomyopathy with LVEF
35% and dilated LV (LV end-diastolic diameter 60 mm), and echocardiographic evidence of dyssynchrony defined by: pre-ejection aortic delay > 140 ms and inter-ventricular mechanical delay > 40 ms. The implantation of a CRT device was also considered in some NYHA class II patients who had ECG and echocardiographic criteria for CRT and who were candidates for the implantation of a standard pacemaker or an internal defibrillator.
Implantation technique
The technical aspects of lead and device implantation have been described in detail in a previous publication.5 Briefly, the coronary sinus was cannulated from a subclavian entry site using a long peelable guiding sheath through which a quadripolar 7 Fr 4 mm-tip steerable electrophysiological catheter was introduced as distally as possible. The guiding sheath was advanced along the electrode catheter which was then removed, and the permanent pacing lead was inserted and placed in a lateral branch of the coronary sinus where the latest local electrogram was recorded relative to the QRS onset and where the pacing threshold was considered adequate without diaphragmatic contraction. The diaphragmatic threshold had to be at least three times the pacing threshold. If the latter was >3 V, the diaphragmatic threshold had to be >10 V. The lateral lead position was confirmed by the left anterior oblique view. In order to avoid unnecessary injection of contrast dye, a coronary venogram was obtained to identify a target vein only if a lateral branch was not found by simple lead manipulation. When a posterior vein was used, the lead was pushed as distally as possible to end up in a lateral position through an interbranch collateral. For each procedure, skin-to-skin procedure duration and fluoroscopy times were precisely recorded by a technician.
Failure of CRT was defined as the inability to place the LV lead in a stable position in a lateral vein with an adequate pacing threshold and a reasonable margin below the diaphragmatic contraction threshold within 3 h or if the procedure had to be interrupted because of patients’ intolerance or haemodynamic instability. The great cardiac vein was not considered as an acceptable site for the insertion of the LV lead, even when a lateral branch was not found .
Statistical analysis
Categorical data are expressed as incidence, and non-categorical data are expressed as mean ± standard deviation.
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Results |
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During the study period, we failed to implant a CRT device in 10 patients (10%) on first attempt. Baseline characteristics of patients in whom the first CRT attempt was unsuccessful are summarized in Table 1. In these 10 patients, mean age was 72 ± 11 years and mean LVEF was 24 ± 8%. Mean procedure duration was 127 ± 29 min and mean fluoroscopy time was 52 ± 10 min. In all patients, the coronary sinus was successfully cannulated. Coronary venogram was obtained in all but two patients: one patient was known to be allergic to contrast dye and in the other patient, despite an interesting lead position, the target vein failed to provide a stable location and lead dislodgement was repeatedly observed. The causes of failure of CRT were as follows: in five patients, the great cardiac vein was the only tributary of the CS that was found, in one patient dissection of the CS was observed, and in four patients a lateral vein was found but was too small to provide a stable location for the insertion of the LV lead.
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In six patients, CRT was not reattempted: three patients were in poor haemodynamic state; one patient had a class 1 indication for DDD pacing (second degree Mobitz II AV block) and severe systolic dysfunction, but had NYHA class II and was eventually implanted with a right atrio-ventricular DDD pacemaker; one patient was a candidate for prophylactic implantable cardioverter defibrillator for ischaemic heart disease based on MADIT II criteria8
and had left bundle branch block (LBBB) but was also in NYHA class II; and one patient with atrial fibrillation and signs of severe heart failure improved his functional status after AV node ablation and implantation of a right ventricular VVIR pacemaker. In the remaining four patients, a CRT device was successfully implanted by the same operators in the second attempt. Table 2 summarizes procedure durations and fluoroscopy times of primary implantations and repeat CRT. Mean time from the first procedure was 74 ± 43 days. Mean procedure duration on the second attempt was 144 ± 38 min and mean fluoroscopy time was 62 ± 20 min. In Patients 1 and 8, during the first procedure, the long sheath was ejected while attempts were made to push the sheath more distally inside the coronary sinus. The target vein was a small lateral branch that could not be cannulated as distally as necessary to obtain a stable position. The procedure was interrupted because both patients developed severe hypotension. The second procedure was successful in both patients who were in better haemodynamic condition and could tolerate long procedure durations to achieve placement of the LV lead in the same vein. In Patient 5, coronary sinus dissection occurred during manipulation of the deflectable electrophysiological catheter before a lateral branch could be identified, and we were unable to find a target vein through the dissection. During the second procedure, the blood flow in the coronary sinus was restored and the coronary venogram was obtained immediately after the insertion of the long sheath and before the placement of the LV lead that was inserted in a postero-lateral branch. In Patient 10, the technical difficulty that resulted in failure of the procedure was a small lateral branch that originated from the coronary sinus with an acute angle. It was therefore impossible to obtain a stable position for the LV lead. On the second procedure, a thinner over-the-wire lead system was used that could be pushed more distally inside the same branch. All of these four patients subsequently responded to CRT and improved their functional status by at least one NYHA class at 6-month follow-up. Table 3 shows pacing and diaphragmatic thresholds during the second procedure and pacing thresholds at 1- or 6-month follow-up. No further complication that required reintervention occurred at 6-month follow-up in successfully reimplanted patients.
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In the remaining 90 patients (67 men, mean age: 71 ± 8 years), the implantation of a CRT device was successful on first attempt. Mean procedure duration was 96 ± 35 min and mean fluoroscopy time was 30 ± 18 min. The acute pacing threshold was 1.1 ± 0.8 V. The acute diaphragmatic threshold assessed during the procedure was >10 V in 82 patients, 8 V in 2 patients, 7 V in 2 patients, 4 V in 1 patient, and 2 V in 1 patient. Evolution of pacing thresholds is depicted in Figure 1. At 1- and 6-month follow-up, mean pacing threshold was 1.1 ± 0.9 and 1 ± 0.8 V, respectively. In one patient, the elevation of pacing threshold required a second intervention. Diaphragmatic contractions were observed in 11 patients, which could be overcome by lowering the pacing amplitude in 7 patients, but led to lead repositioning in 4 patients. In these four patients, acute diaphragmatic contraction threshold was >10 V and acute pacing threshold was 0.6, 1, 1.6, and 0.7 V, respectively, during the first successful procedure.
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Discussion |
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Although CRT has modified patients’ prognosis in terms of quality of life and survival in the presence of LV systolic dysfunction and dyssynchrony, it is a challenging procedure that requires particular skill for placeing the LV lead. Unlike standard right ventricular pacing, the implantation of CRT is not successful in 100% of cases, and in order to obtain a high success rate with minimal complications, it should be performed by experienced teams. To achieve this therapeutic goal, it is critical that the LV epicardial lead be positioned appropriately in the region with delayed activation and mechanical dyssynchrony.9
Transvenous LV lead placement is dependent on the availability of a vein, and because of the variable coronary venous anatomy,10 there may not always be a suitable major vein in the region of interest that can accommodate a pacing lead with acceptable pacing parameters. The high degree of variability in the number of branches between the middle cardiac vein and the anterior inter-ventricular vein, the interbranch collateralization, and intramural vs. epicardial course may significantly impact selection and cannulation of a cardiac vein as well as the stability and pacing threshold of an implanted lead. The limiting factors that explain the failure of CRT are as follows: (i) The coronary sinus opens into the right atrium postero-medially, with its opening being guarded in some patients by the thebesian valve, which can hinder its cannulation.11 (ii) The acute angle at the origin of the coronary sinus can also represent a difficulty, particularly in patients with a highly dilated right atrium. (iii) The anatomy of the tributaries of the coronary sinus explains why in some patients the only branch available is the great cardiac vein, or lateral veins are present but they are too small to provide a stable location for the LV lead. Of all the branches of the coronary venous system, the great cardiac and the middle cardiac vein are the two most consistently present branches.10 Lateral and posterior venous branches that are usually the first choices for lead placement are together seen in <50% of human hearts, unlike the anterior inter-ventricular and middle cardiac veins that are seen in more than 90%.12 (iv) Coronary sinus dissection may result from catheter manipulation and hampers the placement of the LV lead. (v) In some patients, the lead is placed successfully in a lateral branch, but diaphragmatic contraction occurs at pacing amplitudes very close to the pacing threshold, which makes it impossible to leave the LV lead in that position. (vi) Pacing thresholds in lateral veins are sometimes unacceptably high. (vii) Finally, lead dislodgement can occur at the end of the procedure at the time of peeling the long sheath. This complication can be limited if two operators are available, one peeling the sheath, while the other one holds the lead.
At first, when CRT was introduced, dedicated lead systems were not available, and standard pacing leads were used. The failure rate was as high as 47%.13 With the development of leads specifically designed to be implanted in the coronary venous system, the success rate increased to 88%.
In MUSTIC2 and MIRACLE3 studies, the primary success rate was 92%. In the MUSTIC study,2 a lateral position was reached in only 80% of the patients. Early dislodgement occurred in 12.5%, which was successfully corrected in 8%. Overall, at the end of the crossover phase, 88% of patients had a functional LV lead. In these two studies, there is no mention of a second attempt after initial failure of implantation of the LV lead.
In the CARE-HF study,4,7 the overall success rate was 95.9% and the primary success rate was 86.7%. In this study, up to three attempts were allowed and, in order to increase the likelihood of implanting the CRT pacemaker, referral to more experienced centres was allowed or even encouraged. The only independent predictor of successful implantation of a CRT pacemaker was the operators’ experience.
Our study results indicate a high success rate of 90% in the first CRT attempt and our overall success rate was 94%, which is in the range of percentages previously reported in the literature. On the basis of our data, when we conducted a second attempt in a selected group of patients, we were successful in all cases. The originality of our report is that repeat procedures were performed by the same operators, and patients were not sent to a different institution. We started CRT in 1996 and we can consider that our leaning curve has been completed. It is also noteworthy that each procedure was performed by two experienced operators, which might have contributed to our high success rate.
Another interesting finding of our study lies in the fact that, except in one patient who had a thinner LV lead system during the second procedure, all successful reattempts were made with the same material. The time delay between the first and the second attempt was <4 months. Thus, there was no effect of changes of equipment over time on our success rate.
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Limitations of the study |
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The first limitation of our study is the small number of patients recruited in a single centre that made impossible any statistical analysis in order to identify predictors of unsuccessful implantation.
Another limitation is that we performed a second procedure in only 4 of our 10 patients in whom the first implantation was unsuccessful, and in 6 patients we did not schedule a repeat procedure. This low rate of reimplantation attempt limits the generalizability of our results to other centres and does not support the hypothesis that a second procedure is likely to be successful in all cases. When coronary sinus dissection or a patient’s haemodynamic intolerance is the cause of failure, a second procedure can be attempted after restoration of blood flow in the coronary sinus and improvement of patient’s haemodynamic status. The use of pain medication may also improve patient’s tolerance and increase the likelihood of success. When a small vein does not provide a stable position for the LV lead, the success rate can be improved by the use of a thinner over-the-wire lead system.
In five of our patients, the only tributary of the coronary sinus was the great cardiac vein. In none of them was a second procedure considered. This population of patients may be candidates for epicardial lead placement. However, one should be cautious in interpreting the results of direct coronary venography. Although visualization of tributaries of the coronary sinus is of crucial importance for selection of an adequate branch, depending on the anatomy of the coronary venous system and the way the venogram is obtained, all the branches may not be identified. In some patients, the origin of the posterior branch is very proximal and may even be separated from the ostium of the coronary sinus. Therefore, if contrast dye is injected too distally inside the coronary sinus, the posterior branch may not be identified. To overcome this limitation, the coronary venous anatomy can be visualized by electron beam computed tomography angiography prior to the procedure.12
Two of our 10 patients with failed implants did not have a contrast venogram during the procedure. These two patients did not benefit from a second procedure: one patient with LBBB, ischaemic heart disease, and MADIT II criteria for implantation of a defibrillator and class II NYHA was allergic to contrast dye contrast. Since she did not have symptoms of advanced heart failure, we did not consider a second attempt with pre-treatment by anti-allergy medications. She ended up with a single-chamber defibrillator. During follow-up, her CHF status remained stable on medications. In the other patient, repeated lead dislodgement was observed. After several attempts, the LV lead could eventually be stabilized. Thus, we did not perform coronary venography to identify another site. But at the time of sheath removal, the lead was ejected from the coronary sinus and the procedure was interrupted. She was in too poor haemodynamic state to go through a second attempt.
Among the 90 patients who were successfully implanted with a CRT device on first attempt, 6 patients had an acute diaphragmatic contraction threshold <10 V. We had to settle for sites with lower diaphragmatic thresholds after failure of positioning the lead in other sites. Some authors suggest that any diaphragmatic threshold <10 V should be avoided because of a high likelihood of reintervention. Surprisingly, none of these six patients required subsequent lead revision for diaphragmatic contraction.
Five of our patients who were successfully implanted on first attempt required lead revision: one for early lead dislodgement and four for diaphragmatic contraction. As the goal of our study was to determine the incidence and the causes of primary failures, these patients were not included in our study population. In these cases, we consider lead dislodgement as a complication of a primarily successful procedure and not a failure. Surprisingly, all four patients who had lead revision for diaphragmatic contraction had a diaphragmatic threshold >10 V and pacing thresholds <2 V during the first successful procedure.
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Conclusion |
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Our results show that the success rate of implantation of the LV lead is very high. After an initial failure, a repeat procedure can be attempted by the same operators in a highly selected group of patients, which is associated with a high success rate. These encouraging results remain to be verified on larger populations of patients.
Conflict of interest: none declared.
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References |
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