Interact CardioVasc Thorac Surg 2008;7:839-844. doi:10.1510/icvts.2008.178301
© 2008 European Association of Cardio-Thoracic Surgery
Institutional report - Arrhythmia |
Biventricular pacing for end-stage heart failure: early experience in surgical vs. transvenous left ventricular lead placement
Rony Atouia,
Vidal Essebagb,c,
Valerie Wua,
Yin Gea,
Marie-Helene Auclaira,
Tom Hadjisb,c and
Dominique Shum-Tima,*
a Division of Cardiac Surgery, McGill University Health Center, 1650 Cedar Avenue, Suite C9-169, Montreal, Quebec, H3G 1A4, Canada
b Division of Cardiology, McGill University Health Center, Montreal, Quebec, Canada
c Division of Cardiology, Sacré-Coeur Hospital, Montreal, Quebec, Canada
Received 20 February 2008;
received in revised form 18 June 2008;
accepted 19 June 2008
 Funding: This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC) and Fonds de la Recherche en Santé du Québec (FRSQ). Dr. Essebag is the recipient of a Clinician Scientist award from the Canadian Institutes of Health Research (CIHR) and Dr. Shum-Tim is the recipient of a Clinician Scientist award from the FRSQ.
*Corresponding author. Tel.: +1 (514) 934-1934 ext. 44326; fax: +1 (514) 934-8289.
E-mail address: dshumtim{at}yahoo.ca (D. Shum-Tim).
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Abstract
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Transvenous coronary sinus lead placement is currently the standard approach for left ventricular pacing. The aim of this study is to assess whether a mini-thoracotomy approach would be feasible and safe when used for cases in which transvenous procedures were ineffective or judged unlikely to succeed. Biventricular pacing was performed in 138 consecutive patients with 47 patients undergoing a mini-thoracotomy procedure. NYHA status, quality of life, electrical and echocardiographic data were assessed in the two groups over a follow-up period of 17.6±4.2 weeks. There was no significant difference in the preoperative characteristics in both groups other than a greater prevalence of renal failure and previous cardiac surgery among the surgical patients. The mean procedure time was significantly longer in the transvenous group. No significant differences were noted in the immediate or long-term pacing parameters. Two mortalities were observed in the surgical group >2 weeks following the procedure. During the follow-up period, we noted a comparable improvement in the echocardiographic parameters, QRS duration and NYHA status with both approaches. Our results suggest that even when performed on high-risk patients, epicardial lead placement through a mini-thoracotomy is beneficial and feasible as a ‘rescue’ procedure after a failed transvenous approach.
Key Words: Mini-thoracotomy; Chronic resynchronization therapy; Epicardial leads; Biventricular pacing; Congestive heart failure
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1. Introduction
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Several trials have recently demonstrated significant improvement in ventricular function, exercise tolerance, quality of life, and reduction in hospitalization and mortality in patients undergoing cardiac resynchronization therapy (CRT) [1–7]. It is estimated that approximately 30% of patients with congestive heart failure (CHF) experience significant ventricular dysynchrony which can impair the already depressed cardiac function and significantly increase the risk of death [1, 3].
After implanting the right atrial and right ventricular leads through standard percutaneous approaches, the left ventricular (LV) lead is implanted transvenously in the majority of cases and advanced through the coronary sinus into a LV epicardial vein.
Unfortunately, despite improvements in implantation techniques, the percutaneous procedure can be time consuming, often requiring long exposure to fluoroscopy and cannot be applied to all patients because of venous anatomy limitations resulting in an overall success rate of 75–93% [4]. Limited availability of suitable coronary sinus tributaries often increases the difficulties in achieving the optimal hemodynamics [8]. Furthermore, major complications such as coronary sinus perforation may occur. This has caused interest in alternative techniques, such as a limited thoracotomy or video-assisted thoracoscopy [9] with or without robotic assistance [10].
The aim of this study was to report our experience of CRT performed via a mini-thoracotomy and transvenous approaches in a cohort of patients with refractory CHF.
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2. Materials and methods
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2.1. Patient selection
Our study consists of 138 consecutive patients who underwent CRT between June 2003 and April 2006. Patient selection was based on standard biventricular pacing indications [11] and included patients with NYHA class III or IV heart failure, ischemic or non-ischemic cardiomyopathy with an EF  35% and QRS duration >120 ms. No patient who underwent CRT was excluded from this analysis.
A mini-thoracotomy approach was used in 47 patients who experienced a transvenous implantation failure (n=20) or were directly referred for surgery (n=27). A transvenous approach was considered a failure in case of unsuccessful implantation of the lead, with pacing thresholds 3.0 V at 0.5 ms, after at least 2 h of direct attempts.
Postoperative follow-up was scheduled on an outpatient basis at 1–2 weeks and 3–5 months post-implantation for device interrogation and assessment of functional status. Furthermore, a quality of life measurement as estimated by the Minnesota Living with Heart Failure Questionnaire (MLHF) was collected from the medical records or through a follow-up phone conversation. QRS durations, ventricular function and dimensions were assessed. The severity of mitral regurgitation was classified as mild (grade 1), moderate (grade 2), or severe (grade 3).
2.2. Implantation procedure
2.2.1. Transvenous approach
Right atrial and right ventricular pacing were established using standard transvenous lead models and insertion techniques via the subclavian and/or cephalic veins [12]. Under fluoroscopy, the LV leads were positioned into a lateral tributary of the coronary sinus. Venography was used to guide optimal lead positioning with the target site being the lateral or posterolateral wall. If lateral veins were not accessible, of if pacing thresholds were unacceptably high, patients were referred for epicardial LV lead placement rather than implantation of the lead in an anterior vein.
2.2.2. Mini-thoracotomy approach
The surgical epicardial implantation technique has been described elsewhere [9]. In brief, the procedures were performed under general anesthesia, with the patient placed in a 30° rotation to the right. The majority of these procedures (>90%) were performed by a single cardiac surgeon (DST).
After conventional implantation of the right atrial and ventricular leads, a 3–4 cm-long left mini-thoracotomy was made through the fifth intercostal space. The pericardium was opened longitudinally anterior to the phrenic nerve and suspended with traction sutures to better expose the lateral wall.
Epicardial leads, either screw-in type (CapSure Epi 5071, Medtronic Inc., Minneapolis, MN, USA) or steroid-eluting (CapSure Epi 4965; Medtronic Inc., MN, USA) were implanted posterior to an obtuse marginal branch avoiding areas of scarred myocardium. Once a site with satisfactory pacing threshold was identified (impedance >200 and <2000, sensing >5 mV and pacing threshold measured at 0.5 ms <2.0 V), the lead was sewn with 5-0 non-absorbable sutures. No chest tube was placed in the majority of cases and all patients were extubated in the operating room and observed in the coronary care unit overnight.
2.3. Statistical analysis
Descriptive data are expressed as percentages of patients, means±S.D. for normally distributed variables, and medians and ranges for non-normally distributed variables. The baseline characteristics of the two groups were compared using an unpaired Student t-test or a Mann–Whitney U non-parametric test when applicable. Differences in proportions were compared by a  2 analysis or Exact Fisher's test, as appropriate. Changes in preoperative and postoperative measurements were compared among individual patients with a paired t-test or Wilcoxon non-parametric tests. For all tests, two-sided comparisons were performed and a P<0.05 was considered statistically significant.
Data were collected on standard forms and analyzed using SAS for Windows version 8.02 (SAS Institute Inc., Cary, NC).
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3. Results
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3.1. Baseline demographics
Between June 2003 and April 2006, a total of 138 consecutive patients underwent CRT. In 111 patients, the transvenous procedure was first attempted. Of these, 20 patients needed to have the lead surgically implanted due to a failure to catheterize the coronary sinus or to an excessively high pacing threshold. Furthermore, 27 patients were directly referred for surgical lead placement. Therefore, a mini-thoracotomy was used in 47 patients.
Table 1 summarizes the baseline characteristics for the patients in this study. All patients were in NYHA class III or IV, with a mean EF of 19.3±6.5% and a QRS duration of 174.4±27.3 ms (Table 2). There was no significant difference in the preoperative characteristics in both groups other than a greater prevalence of renal failure and previous cardiac surgery among the surgical patients. Furthermore, pharmacological therapy did not significantly differ between the two groups.
3.2. Intraoperative data
Successful surgical implantation of the epicardial leads was accomplished in all patients with a significantly shorter average procedure time of and satisfactory pacing thresholds. These values did not significantly differ from those obtained with the transvenous approach (Table 2).
3.3. Follow-up
The mean follow-up time was 17.6±4.2 weeks, representing 57.9 patient-years and was 88% complete. There were two in-hospital mortalities in the surgical group, both occurring >2 weeks following uncomplicated surgeries; one due to a myocardial infarction and the other due to an exacerbation of heart failure after hip surgery.
Table 3 shows no significant difference in the rate of in-hospital complications between the two groups, other than a greater proportion of lead dislodgement in the transvenous group. No patient required blood transfusions and there were no reexplorations for bleeding. However, the median hospital stay after the surgical implantation was four days (range 2–6) as opposed to one day (range 1–3) for the transvenous approach.
During the follow-up period, electrical pacing parameters remained relatively stable, with no significant difference between the two groups (Table 4).
The hemodynamic benefits of CRT were also similar in both groups. There was a noticeable trend towards improvement in the overall EF associated with a reduction in the LVESD and LVEDD (Fig.1 and Table 4). Although these changes did not reach statistical significance, we noted a significant improvement in the NYHA class in both groups (Fig. 1) and a mean MLHF score of 36.8±6.8. For the entire series, the mean QRS duration decreased significantly to 148.4±17.39 ms with no significant difference between the two groups (Table 4 and Fig. 2).
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Fig. 1. Ejection fraction and NYHA class at baseline and after biventricular pacing in the transvenous and mini-thoracotomy groups. *Denotes statistically significant difference (P<0.05).
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Fig. 2. QRS duration after biventricular pacing in the transvenous and mini-thoracotomy groups. *Denotes statistically significant difference (P<0.05).
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4. Discussion
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Several prospective studies have demonstrated that biventricular pacing can improve ventricular function, exercise capacity and quality of life of patients with refractory CHF [1–7, 13]. Transvenous insertion of LV leads is currently the route of choice for CRT. Unfortunately, its success rate is about 75–93%, as it is totally dependent on the inconsistent coronary venous anatomy [12].
Although some centers do describe excellent success rates with percutaneous leads, this does not appear to reflect the average experience. Early and late implantation failures are reported to occur in about 15% and 10% of patients, respectively, with inability to cannulate the coronary sinus being the most frequent reason for failure of lead implantation [4]. Other reported causes are inappropriate capture, lead dislodgement, perforation, and phrenic nerve stimulation. The InSync Italian Registry reported a success rate of 89% with an average procedure time of 2.63±1.13 h and a dislodgement rate of 7.3% [7]. The MIRACLE trial noted a failure rate of about 8% [4], which is similar to the rate reported by the MUSTIC study [3]. Moreover, major complications may occur. In the MIRACLE trial, coronary sinus dissection or cardiac vein perforation occurred in 6% of the 571 patients, and complete heart block and/or cardiac arrest were noted in 1.2% of the cases [4]. Another recent study reported an 11% rate of transvenous lead-related complications after a follow-up of nearly four years [12].
This study confirms that transvenous lead implantation is feasible with a success rate of about 82% which correlates with the average range reported in the literature [14]. Perioperative complications were low and there was no procedure-related mortality. The main advantage of this approach is, therefore, its minimally invasive nature in this high-risk patient population. This advantage is highlighted by the lower length of stay compared with the surgical approach.
The site of LV stimulation site is key to achieving significant hemodynamic and functional benefits of CRT [3, 5]. Suboptimal lead positioning might be one of the reasons behind the high number of non-responders to CRT (30%) [4]. Placing the lead in the anterior or middle cardiac veins can actually worsen hemodynamic indices because of early stimulation of the interventricular septum [9]. Despite this evidence, transvenous LV leads are being implanted in sub-optimal positions, mainly because of anatomic constraints. In the InSync Italian Registry, only about 70% of the LV leads were positioned in the posterolateral tributaries [4].
Given the limitations of percutaneous placement, other approaches are becoming critically important for CRT. Surgical epicardial stimulation has a number of advantages: it enables direct visualization of the LV with direct access to its lateral wall, aids in choosing the most suitable surface and helps to avoid areas of fibrosis. Potentially combined electrophysiologic and echocardiographic mapping could intraoperatively guide the surgeon to more precisely identify the area of latest electrical activation and mechanical contraction [15].
In our series, there were no differences in the LV pacing performance between both approaches. This was also observed in other studies [12]. Despite its more invasive nature, we did not observe any surgery-related or immediate peri-operative complications. The two episodes of pneumonia may have been related to general anesthesia and thoracotomy. However, these two patients were hospitalized preoperatively for longer than 10 days with CHF exacerbation.
Our surgical patients presented short-term benefits comparable to patients in the transvenous group. These observations are in keeping with data from the literature. In fact, at 3–5 months follow-up, we noted a significant improvement in the NYHA functional class, correlating with the subjective improvement documented by the MLHF score. During the follow-up period, we noted two in-hospital mortalities in the surgical group. Both occurred two weeks post implantation, and were considered not to be the result of surgical complications. However, the possibility that the surgical procedure contributed to cardiac decompensation cannot be excluded.
In this study, a mini-thoracotomy was done for patients who either had a failed percutaneous intervention or were directly referred for surgery. Other centers have reported their promising experience with video-assisted throracoscopic procedures or robotically enhanced LV-leads implantations [9, 10]. However, widespread use of these techniques is limited by access to thoracoscopic or robotic systems and generally requires single-lung ventilation. Furthermore, a mini-thoracotomy can be performed by almost any cardiothoracic surgeon in any cardiac center, and does not require advanced technology or expertise in thoracoscopic or robotic procedures.
This study is limited by the fact that it is a cohort study with a relatively short follow-up period. The comparison between LV lead implantation techniques is limited by the fact that the two approaches were not randomized. In the surgical group, an anatomical approach was used for selecting the LV pacing sites targeting the lateral wall, without the use of intra-operative hemodynamic or electrophysiologic mapping techniques.
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5. Conclusion
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In conclusion, transvenous implantation of the LV lead is effective and remains the first choice approach for biventricular pacing. However, recent reports and our experience confirm that a significant failure rate still persists. The results of this study demonstrate that a mini-thoracotomy approach for LV lead implantation is feasible and may avoid some of the limiting factors of transvenous procedures. Furthermore, the observed early functional and hemodynamic improvements compare favorably with those reported for transvenous lead placement. Presently, it serves as an important ‘rescue’ procedure in the setting of failed coronary sinus cannulation. With the improvement in epicardial leads, it might even have potential benefits as primary intervention in a specific subset of patients. Meanwhile, our results suggest that a combined approach, namely a transvenous attempt followed by a back-up surgical procedure, is feasible and significantly improves the overall success of CRT.
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Acknowledgements
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We thank Mrs Jovette Rivet for her help with data collection.
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Abstract
1. Introduction
