J Thorac Cardiovasc Surg 2008;135:188-195
© 2008 The American Association for Thoracic Surgery
Worldwide surgical experience with the Paracor HeartNet cardiac restraint device
Charles T. Klodell, Jr, MDa,*,
Juan M. Aranda, Jr, MDb,
David C. McGiffin, MDc,
Barry K. Rayburn, MDd,
Benjamin Sun, MDe,
William T. Abraham, MDf,
Walter E. Pae, Jr, MDg,
John P. Boehmer, MDh,
Helmut Klein, MDi,
Christof Huth, MDj
a Department of Surgery, Division of Thoracic and Cardiovascular Surgery, University of Florida College of Medicine, Gainesville, Fla
b Department of Medicine, Division of Cardiology, University of Florida College of Medicine, Gainesville, Fla
c Department of Surgery, Division of Cardiothoracic Surgery, University of Alabama at Birmingham School of Medicine, Birmingham, Ala
d Department of Medicine, Division of Cardiology, University of Alabama at Birmingham School of Medicine, Birmingham, Ala
e Department of Surgery, Division of Cardiothoracic Surgery, The Ohio State University, Columbus, Ohio
f Department of Medicine, Division of Cardiology, The Ohio State University, Columbus, Ohio
g Department of Surgery, Division of Cardiothoracic Surgery, The Pennsylvania State University, Hershey, Penn
h Department of Medicine, Division of Cardiology, The Pennsylvania State University, Hershey, Penn
i Department of Cardiology, Universitatsklinikum Magdeburg, Magdeburg, Germany
j Department of Cardiothoracic Surgery, Universitatsklinikum Magdeburg, Magdeburg, Germany.
Presented at the Eighty-seventh Annual Meeting of The American Association for Thoracic Surgery, Washington, DC, May 5–9, 2007.
Received for publication May 4, 2007; revisions received August 12, 2007; accepted for publication September 20, 2007.
* Address for reprints: Charles T. Klodell, MD, Thoracic and Cardiovascular Surgery, PO Box 100286, Gainesville, FL 32610. (Email: Klodell{at}surgery.ufl.edu).
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Abstract
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Objective: An elastic ventricular restraint device has been developed for patients with heart failure who remain symptomatic despite treatment with standard therapies. The safety and efficacy of this device are under clinical investigation. Six-month data for the first 51 patients treated worldwide are reported. We hypothesize that the Paracor HeartNet device (Paracor Medical, Sunnyvale, Calif), placed through a minithoracotomy in patients with severe dilated cardiomyopathy, improves clinical and functional status.
Methods: Fifty-one patients with an ejection fraction of 35% or less, with a New York Heart Association class II or III, and receiving optimal medical therapy for at least 3 months, were selected at 15 sites (3 in Europe, 12 in the United States) to undergo implantation of the HeartNet device through a minithoracotomy. Patients were evaluated at baseline and at 6-month follow-up by echocardiography, the 6-minute walk test, cardiopulmonary exercise testing (partial oxygen pressure in mixed venous blood), New York Heart Association class, and (in the United States) the Minnesota Living with Heart Failure questionnaire.
Results: The average age was 52 years (30–73 years), with a preponderance of men and nonischemic cause of heart failure. Implantation was accomplished in 50 of 51 patients (98%). Adverse events included 2 in-hospital deaths secondary to pulmonary complications (4%), additional pulmonary complications in 7 patients (14%), arrhythmia in 14 patients (27%), epicardial laceration in 2 patients (4%), and empyema in 1 patient (2%). Six-month data demonstrated significant improvement in the 6-minute walk test (+65.7, P = .002) and Minnesota Living with Heart Failure scores (–15.7, P = .002) and improvement in echocardiographic findings.
Conclusion: The Paracor HeartNet device can be reliably implanted in patients with heart failure and marked reduction of left ventricular function. These data suggest a functional and clinical benefit, with a trend toward reverse remodeling, and support the conduct of a randomized controlled pivotal trial.
Abbreviations and Acronyms LVEDD = left ventricular end-diastolic dimension; NYHA = New York Heart Association
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Introduction
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Optimal heart failure therapy using neurohormonal blockade with angiotensin-converting enzyme inhibitors and beta-blockers in all patients, and biventricular pacing in certain patients who have prolonged QRS duration, represent the current standard of care for patients with symptomatic systolic heart failure. Despite reductions in morbidity and mortality with medical therapy, there are some patients in whom optimal medical and device-based therapy fail to halt the progressive course of this disease.1
In the current era, patients with end-stage heart failure are considered for destination therapy with a left ventricular assist device or heart transplantation as a final option.2 Multiple therapies have been used or are under investigation in an attempt to intervene earlier in the progression of this disease process. These efforts have centered on surgically reshaping the ventricle or using biventricular pacing to relieve mechanical and electrical asynchrony.3-10 Recently, other mechanical therapies have been investigated to potentially halt the progression of the failing heart and allow for reverse remodeling in patients with stage C heart failure to possibly attenuate progression to end-stage heart failure.11 In a sheep model, it has been shown that a myocardial constraint device can modify the left ventricular geometry after myocardial infarction.12-14 Myocardial constraint devices have also been shown in an ovine model of tachycardia-induced progressive dilated cardiomyopathy to improve cardiac function, reduce left ventricular volume, and reduce mitral regurgitation.15
The Paracor HeartNet device (Paracor Medical, Sunnyvale, Calif) is an elastic ventricular restraint device that was developed for patients with heart failure who remain symptomatic with progressive cardiac remodeling or who continue to remodel without concomitant clinical deterioration, despite treatment with standard evidence-based therapies. It is implanted around the heart to apply a low level of epicardial pressure, thereby reducing wall stress and potentially inducing reverse remodeling. The safety and efficacy of this device are now under clinical investigation. We previously reported the initial US experience with the device.16 This report details the current worldwide surgical experience and 6-month follow-up data for the first 51 patients treated and represents a comprehensive and consecutive series of all patients implanted with the device worldwide.
It was hypothesized that the HeartNet device could be safely implanted through a minithoracotomy in patients with heart failure and significantly reduced left ventricular systolic function and lead to improvement in clinical and functional status.
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Materials and Methods
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Fifty-one patients with an ejection fraction of 35% or less, with New York Heart Association (NYHA) class II or III, and receiving optimal medical and or device therapy for at least 3 months were selected at 15 sites (3 in Europe, 12 in the United States) to undergo implantation of the HeartNet device through a minithoracotomy. All US sites obtained investigational review board approval of the Food and Drug Administration-approved safety and feasibility trial and informed consent before patient enrollment. Criteria for enrollment included patients with symptomatic heart failure (College of Cardiology/American Heart Association stage C) caused by ischemic or nonischemic dilated cardiomyopathy and receiving stable medical and device therapy for heart failure for at least 3 months. This included pharmacologic therapy with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, as well as beta-blockers, diuretics, and aldosterone inhibitors as tolerated. An ejection fraction of less than or equal to 35% and receiving optimal medical and device therapy, including resynchronization therapy as indicated, were additionally required for consideration. Patients with NYHA class IV heart failure, acute exacerbation of symptoms, and previous cardiac operations were excluded. Left ventricular end-diastolic dimension (LVEDD) of greater than 85 mm was subsequently added as an exclusion criterion after initiation of enrollment. Patients were evaluated at baseline and at 6-month follow-up by echocardiography, 6-minute walk test, cardiopulmonary exercise testing (partial oxygen pressure in mixed venous blood), NYHA class, and (in the United States) the Minnesota Living with Heart Failure questionnaire.
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Operative Technique
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All procedures were performed via a left anterior minithoracotomy under general anesthesia. Patients were positioned supine, and fluoroscopy was used to identify the cardiac apex. Minithoracotomy incision was performed 1 or 2 interspaces lower than the apex to allow the correct trajectory for the delivery system. Rib spreading was performed only to the extent necessary to accommodate the introducer sheath. The pericardium overlying the cardiac apex was opened and suspended with stay sutures. The introducer was inserted into the intrapericardial space and expanded (Figure 1, A). Frequently the previously placed stay sutures were tensioned along the introducer to keep the edges of pericardium from protruding in the path to the cardiac apex. An unobstructed path to the cardiac apex was ensured by direct visualization or by using a 10-mm thoracoscope through the introducer. After confirmation of the introducer positioning, the delivery system (Figure 1, B) was advanced through the introducer under fluoroscopic guidance. The apex was captured with the suction cup while the device was inserted and deployed. Once the delivery system was removed, either direct visualization or the thoracoscope was used synergistically with fluoroscopy to ensure appropriate device deployment and location (Figure 2). The pericardium was loosely approximated, and a chest drain was left in place. Thoracotomy closure was accomplished in standard fashion.
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Figure 1. A, Introducer sheath used to maintain stable access to pericardial space. B, HeartNet delivery system (Paracor Medical, Sunnyvale, Calif).
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Results
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The HeartNet device was successfully implanted in 98% (50/51) of the patients enrolled. The baseline demographics of the patients are listed in Table 1. There was a preponderance of male patients and those with a nonischemic cause of heart failure. All patients had been receiving optimal medical therapy for a minimum of 3 months. Clinical and functional parameters (Table 2) and baseline echocardiographic data (Table 3) demonstrated a moderately ill cohort of patients with NYHA class II and III heart disease. Eight patients (7 nonischemic, 1 ischemic) demonstrated greater than 2+ mitral regurgitation on preoperative transthoracic echocardiography.
Procedural Data
Successful implantation was accomplished via a left anterior minithoracotomy in 50 patients. In 1 patient, the tissue of the pericardium and epicardium was determined to be extremely friable. After an epicardial laceration necessitating suture control, the procedure was aborted. In the 50 patients with successful implantations, the average total anesthesia time was 191 minutes (76–818 minutes, median 164 minutes), although the skin incision to skin closure time averaged 78 minutes (26–233 minutes, median 73 minutes) (Table 4). The actual time to deploy the device and the fluoroscopy time constituted only a small part of the procedure duration.
Postoperative Course and Adverse Events
The average time to ambulation was 1.7 days (0–6 days, median 1 day), and the average intensive care unit stay was 2.9 days (1–16 days, median 2 days). The duration of patient hospitalization averaged 8 days (3–29 days, median 6 days) (Table 4). Perioperative pain-management strategy was selected by the individual surgeon. Strategies included the use of epidural catheters, intercostal nerve blocks, local anesthetic infusion pumps placed into the wound, and selected use of ketorolac.
Serious adverse events (Table 5) included 2 patients with unilateral diaphragmatic paresis and pleural effusion, 1 which resolved completely. One patient with diaphragmatic paresis also presented for follow-up with anemia 1 month after implantation and was found to have colonic polyps. This same patient returned a third time 3 months after implantation with a period of obtundation related to overmedication with narcotics. One patient (2%) required reexploration for bleeding secondary to persistently high chest tube outputs. At reexploration, the bleeding originated from an arterial branch to the diaphragm. Fourteen patients had postprocedure arrhythmias, including 8 patients who presented after discharge with recurrent arrhythmia, which necessitated an admission for heart failure management and arrhythmia treatment.
Two patients sustained epicardial lacerations during the procedure that required suture repair. In 1 patient the implantation proceeded uneventfully after repair of the laceration. In 1 patient (2%) it was thought that the friable nature of the epicardial and pericardial tissue precluded safe implantation of the device, and the procedure was aborted.
Four patients had a total of 11 episodes of worsening heart failure after implantation of the HeartNet device. Three of these patients progressed to decompensated heart failure at 4, 8, and 22 months after implantation of the HeartNet device. Ventricular assist device placement was required in these 3 patients and was accomplished without incident.
Major adverse events (Table 5) included 2 deaths during the initial hospitalization and within 30 days of procedure (overall in-hospital and 30 day mortality was 4%). One patient had significant pulmonary dysfunction and methicillin-resistant Staphylococcus aureus pneumonia requiring reintubation. The patient progressed to multisystem organ failure and died on postoperative day 16. Postmortem examination confirmed severe bilateral necrotizing pneumonia and evidence of necrotizing pancreatitis. There was no evidence of device malfunction, nor was the device implicated as the cause of death. The pericardial adhesions to the device were noted to be mild. Pneumonia developed in 1 patient who required reintubation and had a period of hemodynamic instability requiring vasopressors. This progressed to multisystem organ failure, and the patient died on postoperative day 14. Postmortem examination showed evidence of gastrointestinal hemorrhage and bilateral lower lobe consolidation of the lungs. The report did not comment on density of intrapericardial adhesions to the device. These 2 patients had the largest LVEDDs in this series (90 mm and 94 mm, respectively). After the deaths of these 2 patients with large LVEDDs, patients with an LVEDD greater than 85 mm or an LVEDD index greater than 40 mm were excluded from implantation of the HeartNet device. There were no subsequent early deaths.
Functional parameters showed significant improvement at 6 months in the 6-minute walk test (mean increase 65.7 m, P = .002, n = 36) and Minnesota Living with Heart Failure score (mean decrease 15.7 units, P = .002, n = 26 (US only) when compared with baseline (Figure 3). The peak volume of oxygen use (n = 35) demonstrated a trend toward improvement but did not reach significance at the 6-month interval. It is known that cardiopulmonary exercise testing is a complex test with many confounding factors, requiring further analysis and study of this result.
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Figure 3. 6MWT and MLHF change from baseline to 6 months. 6MWT, 6-minute walk test; MLHF, Minnesota Living with Heart Failure; SD, standard deviation. *P value for MLHF calculated using Wilcoxon signed-rank test; t test was used for all other parameters.
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Echocardiographic parameters also demonstrated significant improvement at the 6-month interval (n = 39, 39 eligible patients, 100% follow-up) with improvements in LVEDD (mean decrease 3 mm, P = .038), end-diastolic volume (mean decrease 25.7 cm3, P = .025), end-systolic volume (mean decrease 23.5 cm3, P = .037), and left ventricular mass (mean decrease 23.1 g, P = .046). The trends in NYHA class paralleled the findings of functional and echocardiographic improvement (Figure 4).
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Discussion
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This report summarizes the current worldwide experience with the Paracor HeartNet device during the Safety and Feasibility trial of this myocardial constraint device. Previous reports have detailed the archetype myocardial constraint device: the Acorn CorCap (Acorn Cardiovascular, St Paul, Minn).11,17 The Paracor HeartNet device differs from the CorCap device in several important ways. The HeartNet device is delivered via a minimal access left thoracotomy inside the pericardium with the aid of an introducer and delivery system, and adheres to the heart because of small textured areas on the epicardial side of the device. The pericardium remaining intact around the heart has an unknown effect on the long-term progression of the disease process, but may facilitate future cardiac surgery. The HeartNet device currently has 16 sizes available and is sized by echo parameters, in theory making the fit consistent over a large size range. This pre-procedure sizing based on objective criteria should allow for reproducible fit to the myocardium and reproducible results. It is also constructed of a nitinol mesh, which is both compliant and elastic. The relatively large compliance range reduces the likelihood of developing a constrictive-type physiology, although the elasticity may provide some positive epicardial pressure that may be beneficial compared with the non-elastic construction of the CorCap device. A recently published ovine study noted that the optimal physiologic restraint level of 3 mm Hg was identified to maximize improvement without an adverse affect on systemic hemodynamics.18 The nitinol mesh may have an additional benefit of reduced adhesion formation when compared with other materials, although further study will be required. It is known that in the patients who have developed progressive heart failure and required ventricular assist devices (n = 3), the devices were implanted uneventfully. Reports from the implanting surgeons (1 HeartNet investigator, 2 not involved in the study) detailed moderate adhesions over the apex of the left ventricle at the site of the pericardial opening, but otherwise mild adhesions. This may ultimately prove a dramatic advantage to this type of device, because some of these patients inevitably will require either assist devices or cardiac transplantation. Further study of the device will help to better elucidate these advantages over other ventricular restraint devices, such as the CorCap or cardiomyoplasty procedures.
Class IV heart failure and adhesions from previous cardiac operations were considered as exclusions for the initial safety and feasibility trial of the HeartNet device. This may have led to a selection bias of a greater number of nonischemic patients with heart failure. It is unclear at this time what the impact of these exclusions would be on the eventual clinical adaptation of this device. In addition, longer follow-up will be required to determine the effect of device implantation on patients with greater than 2+ mitral regurgitation (n = 8).
This report demonstrates that the HeartNet device can be implanted with a high degree of surgical success (98%) in patients with heart failure and reduction of left ventricular function. The surgical implantation procedure was relatively straightforward with only 2 intraoperative complications and a single patient with significant postoperative bleeding. Major adverse events occurred in the 2 patients with the largest hearts as measured by end-diastolic dimension. This early experience indicates that, as with the CorCap, the patients with the largest end-diastolic dimensions are not optimal candidates for this therapy. In the remaining patients, the postoperative course parallels what might be expected after any thoracotomy in this moderately severe ill patient cohort. Also similar to post-thoracotomy care, adequate preoperative pulmonary evaluation and excellent postoperative pain control seem to be paramount to success. The 6-month paired data suggest a functional and clinical benefit, with a trend toward reverse remodeling, and support the conduct of a randomized controlled pivotal trial (Prospective Evaluation of Elastic Restraint to LESSen the effects of Heart Failure), which has begun enrollment in the United States.
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Footnotes
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William Abraham reports grant support from Paracor. John Boehmer reports consulting fees, grant support, and patents from Paracor. Charles Klodell and Barry Rayburn report consulting fees from Paracor.
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Abstract
Introduction
