Cardiac resynchronization therapy (CRT) improves symptoms and survival of patients with congestive heart failure. Cardiac resynchronization therapy is obtained by means of right and left stimulation: percutaneous placement of the right electrodes is feasible in almost all cases, whereas transvenous implantation of the left ventricular (LV) lead fails up to 25% of cases.1
In case of failure of transvenous placement, surgery should be considered and both median sternotomy and left thoracotomy are available. As previously reported,2 minimally invasive approaches reduce surgical risk and rate of complications—thanks to the reduced invasiveness.
We report our experience with CRT through a left minithoracotomy (LM) after failure of the transvenous approach.
MATERIALS AND METHODS
Institutional Review Board and Ethics Committee approval were obtained for research of the institutional database.
The MyoPore sutureless myocardial pacing lead (MSMPL) series 511210-511211-511212 (Boston Scientific Corporation, Natick, MA USA) is a permanent, sutureless, bipolar epicardial lead available at lengths from 25 to 54 cm. The peculiarity of this device belongs to the implantation technique because it is screwed into the thickness of the myocardium by means of a rotation of 2.5 laps. It is usually housed on a straightforward support that allows screwing the device into the myocardium (Fig. 1). An innovative implant tool (FasTac) with a mobile tip allows easy implantation regardless of the angle of deployment. The MSMPL has an enhanced design:
* low-profile construction for reduced electrode head size;
* quadrifilar inner conductor for added safety and durability; and
* full 3.5-mm electrode penetration for reliable fixation, pacing, and sensing; and
* the quadrichannel anode electrode provides increased surface area for enhanced sensing.
From January 2010 to September 2011, 15 consecutive patients were scheduled for surgical CRT after failure of the transvenous approach. The criteria for CRT were:
* New York Heart Association (NYHA) class III or IV,
* ejection fraction less than 35%, and
* QRS duration more than 120 milliseconds.
Patients’ characteristics are summarized in Table 1. They were operated on through an LM, screwing an MSMPL into the LV wall. Ejection fraction was 23.0% ± 5.3%, and the QRS duration was 200.0 ± 37.9 milliseconds. Three patients (20%) had previous cardiac surgery, and four patients had acute endocarditis of the lead. Mean logistic Euroscore was 20.7% ± 11.0%.
The left hemithorax was elevated up to 45 degrees by inflating a balloon under the left scapula. Under selective right lung ventilation, a lateral LM (2 cm away from the left nipple toward the posterior axillary line) was performed via the fourth or fifth intercostal space, depending on the degree of LV enlargement. The pericardium was incised 2 to 3 cm over the phrenic nerve (Fig. 2). The lateral wall was usually easily accessible in this way, and the problem of the angle of deployment (the MSMPL should be perpendicular to the area of implantation) for an effective rotation and screw-in of the lead was easily managed—thanks to this posterolateral approach. However, if the angle for deployment is not perpendicular, a slight retraction of the lateral wall by means of a small swab may be effective.
The “target area” for deployment was the muscular portion of the lateral wall (where the epicardial fat lacks), ensuring an optimal response to electric stimulation (Fig. 3). However, much attention should be paid to avoid injuries of the obtuse marginal branch.
Routinely, when the implantation was completed, the thresholds of stimulation were checked; thus, the MSMPL was connected to the generator located in a subclavicular pocket.
The LM was sutured, leaving a 30F chest drain to the costophrenic angle (Fig. 4).
Continuous variables are expressed as mean ± SD, and categorical variables were expressed as frequencies or percentages. Continuous variables were compared using the t test and the χ2 test. A value of P < 0.05 was regarded as statistically significant.
The intraoperative and postoperative details are reported in Table 2.
Time of surgery was 38.5 ± 3.0 minutes, and no surgical complications or early deaths are reported. Mechanical ventilation was usually discontinued in the operating suite, and the intensive care unit stay was 12 hours or less. No cases of surgical reexploration are reported, and the amount of bleeding was always 200 mL or less. Length of in-hospital stay was 4.0 ± 2.8 days. No cases of acute renal failure are described, although 6 patients (37.5%) experienced chronic renal failure (glomerular filtration rate Cockroft-Gault <50 mL/min).
The mean thresholds of stimulation were 1.1 ± 0.5 V (intraoperative) and 1.1 ± 0.6 V (before hospital discharge) at 0.5 milliseconds (P = not significant). The QRS duration decreased from 200.0 ± 37.9 milliseconds preoperatively to 144.0 ± 25.8 milliseconds postoperatively (P < 0.05).
After 10.7 ± 8.3 months of follow-up, the overall mortality was 0%. The mean thresholds of stimulation was stable during the follow-up (1.1 ± 0.5 V at 0.5 milliseconds) (P = not significant). NYHA class was significantly improved: 12 patients were in NYHA class II and 3 were in NYHA class I.
End-stage cardiomyopathy is a worldwide problem with a trend toward an increase. Cardiac transplantation is rarely available for lack of donors, and the debate about alternative strategies is still ongoing. Recent therapies for systolic heart failure have increased the choices of treatment for patients with end-stage cardiomyopathy.3–5 Unfortunately, heart dysfunction progresses and becomes refractory to medical treatments, with a 1-year survival rate from 10% to 30%.6 The optimization of cardiac output by CRT avoids or reverses the end-organ dysfunction, improving both the survival rate and the quality of life.
Usually, the percutaneous placement of the right leads is feasible. Conversely, the rate of success of the transvenous approach for LV lead placement ranges from 75% to 93%. Sudden injuries of the coronary sinus (up to 6% depending on the skill of the cardiologist) are rare but life-threatening complications.
A surgical approach should be considered in case of7:
* failure of percutaneous insertion,
* late dislodgement of the lead (from 7.3% to 11%),
* phrenic nerve stimulation (2.1%), or
* P-wave oversensing by the LV lead (1.6%).
However, in case of surgical implantation, both median sternotomy and LM are available and thoracotomy should be preferred mainly in redo patients when the risk of sudden injuries during the adhesion’s debridement is quite high.
In our experience, the MSMPL has several advantages:
* The sutureless implantation because the electrode is directly screwed into the thickness of the myocardium.
* The postoperative threshold of stimulation that is low probably because the lead is inserted into the myocardium.
* The threshold of stimulation is stable during the follow-up (1.1 ± 0.5 V at 0.5 milliseconds intraoperatively; 1.1 ± 0.6 V at 0.5 milliseconds before hospital discharge; 1.1 ± 0.5 V at 0.5 milliseconds after 10.7 ± 8.3 months of follow-up; P = not significant).
* The ease of implantation that requires just a rotation of the plastic handle of the lead.
* The stability of the implantation because no cases of dislodgement are described in our series, differing from the percutaneous approach, where the incidence ranges from 7.3% to 11%.
The LM should be considered in such high-risk population because the target area is easily approachable through this posterolateral approach. In our opinion, the muscular portion of the lateral wall is the target area because, in our series, it ensures a very low threshold of stimulation both in early- and medium-term. Thus, any mapping was done before implantation; considering the efficacy of this device, we usually screw-in one lead, and we had no cases of failure during 10.7 ± 8.3 months of follow-up.
The problem of the angle for deployment may be easily managed by means of a posterolateral LM; in fact, when the left thoracotomy is 1 to 2 cm away from the left nipple toward the posterior axillary line, the lateral wall is easily approachable, and the angle for deployment is usually perpendicular. However, if the angle for deployment is not perpendicular, a slight retraction of the lateral wall by means of a small swab may be effective.
Moreover, in the era of minimally invasive approaches, further evolutions may be considered because CRT through an LM should be combined with other minimally invasive procedures, such as surgical revascularization (left internal mammary artery to left anterior descending artery graft) or minimally invasive atrial fibrillation ablation, leading surgeons to a new field of cooperation with electrophysiologists. However, further experiences are required even though these perspectives are useful for this high-risk group of patients.
Several published studies7 have shown that the hemodynamic and functional benefits of CRT are highly affected by the implantation site. Thus, in case of unsatisfactory results by the percutaneous insertion, the surgical approach should be considered.
In summary, a posterolateral thoracotomy should be considered because the lateral wall is easily accessible and the angle for deployment is usually perpendicular; surgical placement of pacing leads has the advantages of direct vision of the target area that may allow accurate implantation with good electrophysiological parameters; the target area should be the muscular portion of the lateral wall, ensuring a low threshold of stimulation; the MSMPL is easily implantable, and no cases of surgical injuries have been reported in our series; and the low threshold of stimulation is noteworthy.