J Thorac Cardiovasc Surg 2007;133:204-209
© 2007 The American Association for Thoracic Surgery
Initial United States experience with the Paracor HeartNet* myocardial constraint device for heart failure
Charles T. Klodell, Jr, MDa,*,
David C. McGiffin, MDb,
Barry K. Rayburn, MDb,
,
Benjamin Sun, MDc,
William T. Abraham, MDc,,
John V. Conte, MDd,
Stuart D. Russell, MDd,
Walter E. Pae, Jr, MDe,,
John P. Boehmer, MDe,,
Juan M. Aranda, Jr, MDa
a University of Florida College of Medicine, Gainesville, Fla
b University of Alabama at Birmingham School of Medicine, Birmingham, Ala
c The Ohio State University, Columbus, Ohio
d Johns Hopkins Medical Institutions, Baltimore, Md
e The Pennsylvania State University, Hershey, Pa.
Read at the Eighty-sixth Annual Meeting of The American Association for Thoracic Surgery, Philadelphia, Pa, April 29–May 3, 2006.
Received for publication April 28, 2006; revisions received August 6, 2006; accepted for publication August 25, 2006.
* 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: This study was undertaken to review the initial results and surgical safety data for the US Food and Drug Administration safety and feasibility trial of the Paracor HeartNet (Paracor Medical, Inc, Sunnyvale, Calif.) myocardial constraint device.
METHODS: Patients with New York Heart Association functional class II or III heart failure underwent device implantation (n = 21) through a left minithoracotomy.
RESULTS: The average age was 53 years (31–72 years). There were 18 men and 3 women, and 17 patients had nonischemic etiology of heart failure. Mean heart failure duration was 8.3 years (1.4-18.8 years). Average ejection fraction was 22% (11%-33%), with an average left ventricular end-diastolic dimension of 74 mm (55-94 mm). Previous medical therapy included angiotensin-converting enzyme inhibitors, ß-blockers, diuretics, digoxin, and aldosterone receptor blockers. At implantation, 17 patients had implantable electronic devices: 1 biventricular pacemaker, 11 biventricular pacemakers with cardioverter-defibrillators, and 5 implantable cardioverter-defibrillators. Patient comorbidities included hypertension in 10 cases, diabetes mellitus in 8, myocardial infarction in 1, and ventricular tachycardia in 8. Mean operative time was 68 minutes (42–102 minutes), and implantation time averaged 15 minutes (5–51 minutes). The average time to ambulation was 1.6 days (1–4 days). The intensive care unit stay averaged 3.3 days (1–16 days), and hospital stay averaged 6.3 days (4–16 days). Atrial fibrillation occurred in 2 patients, and there were 2 in-hospital deaths.
CONCLUSIONS: The Paracor device can be implanted in patients with heart failure and reduced left ventricular function with a high degree of success. Significant surgical complications were infrequent. The initial US experience supports the conduct of a randomized, controlled, pivotal trial.
Abbreviations and Acronyms NYHA = New York Heart Association
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Introduction
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Dr Klodell
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Optimal medical heart failure therapy consisting of neurohormonal blockade with angiotensin-converting enzyme inhibitors and ß-blockers for all patients, with biventricular pacing for certain patients with prolonged QRS duration, represents the current standard of care for patients with symptomatic heart failure. Despite reductions in morbidity and mortality with medical therapy, there are some patients for whom neurohormonal blockade fails 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 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 for the potential to halt the progression of the failing heart and allow reverse remodeling.11 It has been shown that a myocardial constraint device can modify the left ventricular geometry after myocardial infarction in a sheep model.12-14 Myocardial constraint devices have also been shown to improve cardiac function, reduce left ventricular volume, and reduce mitral regurgitation in an ovine model of tachycardia-induced progressive dilated cardiomyopathy.15
The Paracor HeartNet (Paracor Medical, Inc, Sunnyvale, Calif) is an elastic ventricular restraint device that has been developed for patients with heart failure who continue to have symptoms and progressive cardiac remodeling, despite treatment with standard evidence-based therapies. It is implanted around the heart to reduce the wall stress and potentially allow reverse remodeling. It was hypothesized that the HeartNet could be safely implanted through a minithoracotomy in patients with heart failure and would significantly reduce left ventricular systolic function, leading to improvement in clinical and functional status. The safety and efficacy of this device are now under clinical investigation. The initial surgical experience and 6-month data for the first 21 patients treated in the United States are reported here.
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Methods
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After investigational review board approval of the Food and Drug Administration-approved safety and feasibility trial and informed consent, 21 patients at five US sites with New York Heart Association (NYHA) functional class II or III heart failure who had been receiving optimal medical therapy for at least 3 months were selected to undergo implantation of the HeartNet through a minithoracotomy. Patients with NYHA functional class IV heart failure and those with previous cardiac operations were excluded. Patients were evaluated at baseline and at 6-month follow up by echocardiography, 6-minute walking test, cardiopulmonary exercise testing, NYHA functional class assessment, and the Minnesota Living With Heart Failure questionnaire.
Operative Technique
All procedures were performed through a left anterior minithoracotomy with general anesthesia. Patients were positioned supine, and fluoroscopy was used to locate the cardiac apex. Minithoracotomy incision was performed slightly 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 pericardium and expanded (Figure 1, A). An unobstructed path to the cardiac apex was ensured either by direct visualization or by passing 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 grasped 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 (Paracor Medical, Inc, Sunnyvale, Calif) delivery system.
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Results
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The HeartNet was successfully implanted in 95% of the patients enrolled (n = 20/21). The baseline demographic characteristics of the patients are listed in Table 1. There was a preponderance of male patients and those with a nonischemic etiology for 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 in NYHA functional classes II and III. The patients in functional class II who were included (n = 7/21) had elevated Minnesota Living With Heart Failure scores and dramatically reduced 6-minute walking test and cardiopulmonary exercise testing results, similar to the patients in functional class III (Table 4). Three patients (2 nonischemic etiology, 1 ischemic etiology) demonstrated either 2+ or 3+ mitral regurgitation on preoperative transthoracic echocardiography.
Procedural Data
Successful implantation was accomplished through a left anterior minithoracotomy in 20 patients. In 1 patient, the tissues of the pericardium and epicardium were determined to be extremely friable. After an epicardial laceration necessitated suture control, the procedure was aborted. Among the 20 patients with successful implantation, the average total anesthesia time was 177 minutes (95-402 minutes), although the time from skin incision to skin closure averaged 68 minutes (42–102 minutes; Table 5). 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 1.6 days (range 1–4 days, median 1 day). The average intensive care unit stay was 3.3 days (range 1–16 days, median 1.5 days). Duration of patient hospitalization averaged 6.3 days (range 4-16 days, median 5.5 days; Table 5). Perioperative pain management strategy was selected according to individual surgeon preference. 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 6) included 1 case of unilateral diaphragmatic paresis and pleural effusion, which resolved completely. The same patient was seen 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. Two patients had atrial fibrillation after discharge, which necessitated an admission in each case for heart failure management and arrhythmia treatment.
Major adverse events (Table 6) included 2 deaths during the initial hospitalization and within 30 days of procedure (overall in-hospital and 30-day mortality 10%, n = 2/21). One patient had significant pulmonary dysfunction and methicillin-resistant Staphylococcus aureus pneumonia necessitating reintubation. The patient had progression to multisystem organ failure and died on postoperative day 16. Post mortem examination confirmed severe bilateral necrotizing pneumonia with 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. A second patient also had pneumonia necessitating reintubation and a period of hemodynamic instability necessitating vasopressors. This progressed to multisystem organ failure, and the patient died on postoperative day 14. Autopsy showed evidence of gastrointestinal hemorrhage and bilateral lower lobe consolidation of the lungs. The autopsy report did not comment on density of intrapericardial adhesions to the device. These 2 patients had the largest left ventricular end-diastolic dimensions in this series, at 90 and 94 mm, respectively. There were no additional major adverse events in the 6-month follow up. Overall in-hospital and 30-day mortality was 10% (n = 2/21).
Six-month data available (n = 10) showed improvement in multiple clinical and functional parameters (Table 7). Although the small number of patients in this sample precludes reliable statistical analysis, favorable trends were noted in almost all parameters. The Minnesota Living With Heart Failure scores showed the most dramatic reduction after device implantation. Although these data are encouraging, they must be interpreted cautiously as uncontrolled and unblinded.
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Discussion
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This is the first report on the US experience with the Paracor HeartNet during the safety and feasibility trial of this myocardial constraint device. Previous reports have detailed the archetypal myocardial constraint device, the Acorn CorCap (Acorn Cardiovascular, Inc, St Paul, Minn).11,16 The Paracor HeartNet differs from the CorCap in several important ways. The HeartNet is delivered through a minimal access left thoracotomy inside the pericardium with the aid of an introducer and delivery system and adheres the heart because of small textured areas on the epicardial side of the device. The HeartNet currently has 12 sizes available and is sized by echocardiographic parameters, in theory making the fit consistent across a large size range. It is also constructed of a nitinol mesh that is both compliant and elastic. The relatively large compliance range reduces the likelihood of development of a constrictive type physiology, whereas the elasticity may provide some positive epicardial pressure that may be beneficial relative to the inelastic construction of the CorCap device. The nitinol mesh may have an additional benefit of reduced adhesion formation relative to other materials, although further study is required.
Class IV heart failure and adhesions from previous cardiac operations were considered to be exclusion criteria for the initial safety and feasibility trial of the Paracor device. This may have led to a selection bias of a greater number of patients with nonischemic heart failure. It is unclear at this time what the impact of these exclusions would be on the eventual clinical adaptation of this device. Additionally, longer follow-up is required to determine the effect of device implantation on patients with mitral regurgitation (n = 3).
This report demonstrates that the HeartNet can be implanted with a high degree of surgical success (95%) in patients with heart failure and reduction of left ventricular function. The surgical implantation procedure was relatively straightforward, with only a single intraoperative complication. Major adverse events occurred in the 2 patients with the largest hearts, as measured by end-diastolic dimension. This early experience may indicate that, similar to the CorCap, the patients with the largest end-diastolic dimensions may not be optimal candidates for this therapy. In the remaining cases the postoperative course parallels what might be expected after any thoracotomy in this moderately to severely ill patient cohort. Also similar to general postthoracotomy care, adequate preoperative pulmonary evaluation and excellent postoperative pain control appear 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.
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Footnotes
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* Paracor Medical, Inc, Sunnyvale, Calif. 
W.T.A., J.P.B., W.E.P., and B.K.R. report grant support from Paracor Medical, Inc.
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Abstract
Introduction
