Extra-aortic Counterpulsation Research Articles

Framework for patient-specific simulation of hemodynamics in heart failure with counterpulsation support.

Despite being responsible for half of heart failure-related hospitalizations, heart failure with preserved ejection fraction (HFpEF) has limited evidence-based treatment options. Currently, a substantial clinical issue is that the disease etiology is very heterogenous with no patient-specific treatment options. Modeling can provide a framework for evaluating alternative treatment strategies. Counterpulsation strategies have the capacity to improve left ventricular diastolic filling by reducing systolic blood pressure and augmenting the diastolic pressure that drives coronary perfusion. Here, we propose a framework for testing the effectiveness of a soft robotic extra-aortic counterpulsation strategy using a patient-specific closed-loop hemodynamic lumped parameter model of a patient with HFpEF. The soft robotic device prototype was characterized experimentally in a physiologically pressurized (50–150 mmHg) soft silicone vessel and modeled as a combination of a pressure source and a capacitance. The patient-specific model was created using open-source software and validated against hemodynamics obtained by imaging of a patient (male, 87 years, HR = 60 bpm) with HFpEF. The impact of actuation timing on the flows and pressures as well as systolic function was analyzed. Good agreement between the patient-specific model and patient data was achieved with relative errors below 5% in all categories except for the diastolic aortic root pressure and the end systolic volume. The most effective reduction in systolic pressure compared to baseline (147 vs. 141 mmHg) was achieved when actuating 350 ms before systole. In this case, flow splits were preserved, and cardiac output was increased (5.17 vs. 5.34 L/min), resulting in increased blood flow to the coronaries (0.15 vs. 0.16 L/min). Both arterial elastance (0.77 vs. 0.74 mmHg/mL) and stroke work (11.8 vs. 10.6 kJ) were decreased compared to baseline, however left atrial pressure increased (11.2 vs. 11.5 mmHg). A higher actuation pressure is associated with higher systolic pressure reduction and slightly higher coronary flow. The soft robotic device prototype achieves reduced systolic pressure, reduced stroke work, slightly increased coronary perfusion, but increased left atrial pressures in HFpEF patients. In future work, the framework could include additional physiological mechanisms, a larger patient cohort with HFpEF, and testing against clinically used devices.

Hemodynamic Impact of the C-Pulse Cardiac Support Device: A One-Dimensional Arterial Model Study.

The C-Pulse is a novel extra-aortic counter-pulsation device to unload the heart in patients with heart failure. Its impact on overall hemodynamics, however, is not fully understood. In this study, the function of the C-Pulse heart assist system is implemented in a one-dimensional (1-D) model of the arterial tree, and central and peripheral pressure and flow waveforms with the C-Pulse turned on and off were simulated. The results were studied using wave intensity analysis and compared with in vivo data measured non-invasively in three patients with heart failure and with invasive data measured in a large animal (pig). In all cases the activation of the C-Pulse was discernible by the presence of a diastolic augmentation in the pressure and flow waveforms. Activation of the device initiates a forward traveling compression wave, whereas a forward traveling expansion wave is associated to the device relaxation, with waves exerting an action in the coronary and the carotid vascular beds. We also found that the stiffness of the arterial tree is an important determinant of action of the device. In settings with reduced arterial compliance, the same level of aortic compression demands higher values of external pressure, leading to stronger hemodynamic effects and enhanced perfusion. We conclude that the 1-D model may be used as an efficient tool for predicting the hemodynamic impact of the C-Pulse system in the entire arterial tree, complementing in vivo observations.

Study of wave dynamics of an extra-aortic counterpulsation device in a one-dimensional computer model of the arterial system

Study of wave dynamics of an extra-aortic counterpulsation device in a one-dimensional computer model of the arterial system

313 - Clinical Experience in Advanced HF Patients Implanted with an Extra-Aortic Counterpulsation Device (EACD)

313 - Clinical Experience in Advanced HF Patients Implanted with an Extra-Aortic Counterpulsation Device (EACD)

Sunshine Heart C-Pulse: device for NYHA Class III and ambulatory Class IV heart failure.

Advanced heart failure (HF) patients not meeting criteria for ventricular assist device or heart transplant with life-limiting symptoms are limited to medical and resynchronization therapy. The Sunshine Heart C-Pulse, based on intra-aortic balloon pump physiology, provides implantable, on-demand, extra-aortic counterpulsation, which reduces afterload and improves cardiac perfusion in New York Heart Association Class III and ambulatory Class IV HF. The C-Pulse reduces New York Heart Association Class, improves 6-min walk distances, inotrope requirements and HF symptom questionnaires. Advantages include shorter operative times without cardiopulmonary bypass, no reported strokes or thrombosis and no need for anticoagulation. Driveline exit site infections, inability to provide full circulatory support and poor function with intractable arrhythmias remain concerns. Current randomized controlled studies will evaluate long-term efficacy and safety compared with medical and resynchronization therapy.

(881) - Modulation of Autonomic Tone Assessed by Heart Rate Variability in Advanced Heart Failure Patients Treated with an Extra-Aortic Counterpulsation (EACP) System: A Single Center Experience

(881) - Modulation of Autonomic Tone Assessed by Heart Rate Variability in Advanced Heart Failure Patients Treated with an Extra-Aortic Counterpulsation (EACP) System: A Single Center Experience

Abstract 19525: Heart Failure Readmission Rates: Clinical Experience With the C-Pulse® Extra-Aortic Counterpulsation System

Introduction: Heart failure-related readmission rates remain high. In the EFFECT phase I study, 61.3% of patients had repeat hospitalization within one year of initial discharge, with the majority occurring shortly postdischarge or near end of life. Analysis of Medicare beneficiaries from 2007-2009 of 1,330,157 heart failure (HF) hospitalizations found 35% of patients readmitted for the same condition within 30 days. Readmission (RA) reflects increased morbidity, impaired quality of life, and a growing economic burden on health care resources. Hypothesis: The US feasibility investigational study gathered data to evaluate readmission in class III/ambulatory IV HF patients receiving an extra-aortic counterpulsation system (C-Pulse®, Sunshine Heart, Inc.) designed to increase coronary blood flow, reduce the workload of the left ventricle, and improve cardiac function. Methods: Between April 2009 and June 2011, twenty HF patients were enrolled in a prospective US feasibility study undergoing C-Pulse device implantation procedures at 7 centers. RA data was collected at 30 days, 6 and 12 months post implant. Results: The study included 12 males, 18 NYHA class III and 2 ambulatory NYHA class IV patients, 7 ischemic and 13 non-ischemic. Mean age was 56±7 years. Baseline ejection fraction (EF) was 28% ± 6.1. Over 12 months, 3 of the 20 implanted C-Pulse feasibility study patients (15%) had 5 HF hospitalizations after device implantation (Clinical Events Committee adjudicated, occurring at 208 days, 205 and 245 days, 33 and 52 days). Two of the three patients had low device usage compliance prior to HF events (<30% use). Conclusion: Recently published data has demonstrated preliminary indications of safety and efficacy of counterpulsation therapy with the C-pulse system for the management of chronic HF. Lifetime analysis work from the EFFECT study has shown an overall RA rate of 61.3% at 12 months in patients suffering from HF. In comparison, RA rates for patients undergoing C-pulse implantation appear to be greatly reduced at 30 days and at one year. In addition, RA rates for patients undergoing C-pulse implantation are lower than RA rates reported for other forms of durable mechanical circulatory support at 30 days and 1 year.

Abstract 15860: Arterial and Cardiac Hemodynamics in Advanced HF Patients Implanted With the C-Pulse Counterpulsation Device: Implications for Myocardial Recovery

Introduction: Despite intensive medical and device therapy, many HF patients remain symptomatic with refractory NYHA class III/IV. Therapeutic options are limited in this population, with the goal being stabilization of HF progression. A novel approach is the use of an extra-aortic counterpulsation device, C-Pulse™, consisting of an extra-vascular balloon cuff wrapped around the ascending aorta. The C-Pulse operates on principle of counterpulsation however placement on the proximal aorta may afford unique hemodynamic advantages over traditional counterpulsation devices. We report for the first time hemodynamic effects from advanced HF patients implanted with C-Pulse. Methods: Radial tonometry and office BP were measured in successive patients (N=6) NYHA Class III/IV, 5M, EF 17.2±6.6%, age 67.8±9.7 years (mean±SD), during device optimization. Median time from implant was 180 days (range 1-1356 days). Waveforms and blood pressure were obtained after 5 minute steady state OFF period followed by device optimization (ON). Results: Systolic and diastolic BP were maintained with optimization (Table). Myocardial perfusion indexed by subendocardial viability ratio (SEVR) significantly increased primarily resulting from increase in diastolic area, Ad. Cardiac ejection was enhanced; increased forward wave amplitude, P1, and reduced time to peak pressure, P2. Late systolic load from wave reflections was also reduced assessed by augmentation index (Aix). Conclusions: In this small cohort, C-Pulse increased myocardial perfusion and reduced early and late components of cardiac load. Novel finding of reduced Aix may arise from aortic arch baroreceptor stimulation due to enhanced pulsatility or mechanical deformation from the balloon. These changes may translate into improved heart failure symptoms, cardiac reverse remodeling and possibly recovery.Further studies are needed to assess these mechanisms and their association with regression of heart failure.

Ambulatory Extra-Aortic Counterpulsation in Patients With Moderate to Severe Chronic Heart Failure

ObjectivesThe study sought to assess feasibility, safety, and potential efficacy of a novel implantable extra-aortic counterpulsation system (C-Pulse) in functional class III and ambulatory functional class IV heart failure (HF) patients. Background30% to 40% of HF patients suffer from poor functional status and quality of life (QoL) but are not in need of end-stage treatments. We undertook a multicenter single-arm study to assess the C-Pulse System in such patients. MethodsNew York Heart Association (NYHA) functional class III or ambulatory functional class IV HF patients were eligible. Safety was assessed continuously through 12 months. Efficacy measurements included changes from baseline to 6 and 12 months in NYHA functional class, Minnesota Living with Heart Failure (MLWHF) and Kansas City Cardiomyopathy Questionnaire (KCCQ) scores, 6-min walk distance (6MWD), and exercise peak oxygen consumption (pVO2; 6 months only). ResultsTwelve men and 8 women (56.7 ± 7 years, 34 to 71 years of age) with ischemic (n = 7) or nonischemic (n = 13) cardiomyopathy were implanted. There was no 30-day mortality and no neurological events or myocardial infarctions through 12 months. At 6 months, there were 3 deaths (1 device-related). One-year survival was 85%. At 6 months, C-Pulse produced improvements in NYHA functional class (3.1 ± 0.3 to 1.9 ± 0.7, p = 0.0005), MLWHF (63.6 ± 19.9 to 40.2 ± 23.2, p = 0.0005), and KCCQ scores (43.6 ± 21.1 to 65.6 ± 21.5, p = 0.0002), but not 6MWD (275.5 ± 64.0 to 296.4 ± 104.9, p = NS) or pVO2 (14.5 ± 3.6 to 13.1 ± 4.4, p = NS). Improvements continued at 12 months, with 6MWD change becoming statistically significant (336.5 ± 91.8, p = 0.0425). ConclusionsUse of C-Pulse in this population is feasible, appears safe, and improves functional status and QoL. A prospective, multicenter, randomized controlled trial is underway. (C-Pulse IDE Feasability Study-A Heart Assist System; NCT00815880)

Aortic Counterpulsation: C-Pulse and Other Devices for Cardiac Support

Heart failure is the leading cause of hospitalization in the USA. Despite major advances in the medical and device-related therapy including chronic resynchronization therapy for management of heart failure, significant number of patients eventually require advanced cardiac therapy including mechanical circulatory support or heart transplant. Heart transplant is a gold standard for end-stage heart failure but is limited by the donor heart shortage creating a definite need for alternative effective therapies. The earliest and most common form of mechanical circulatory support is counterpulsation therapy. Annually, more than 150,000 patients worldwide receive counterpulsation therapy for various indications including cardiogenic shock or severe left ventricular dysfunction (Nanas and Moulopoulos in Cardiology, 84:156-167, 1994) and many thousands of lives are saved each year (65% survival) (Torchiana et al. in Journal of Thoracic and Cardiovascular Surgery, 113(4):758-764, 1997). There are different types of aortic counterpulsation devices. Here, we will give an overview of different counterpulsation devices with focus on C-Pulse device. Extra-aortic balloon counterpulsation, C-Pulse (Sunshine Heart Inc., Eden Prairie, MN), is an important and novel approach in the management of patients with advanced heart failure who remain symptomatic despite optimum medical and device-based therapy. C-Pulse is designed to provide permanent, long-term, continuous partial circulatory support for New York Heart Association class III and ambulatory class IV heart failure patients. C-Pulse is a nonblood-contacting counterpulsation using an inflatable cuff around the ascending aorta, extra-aortic balloon (EAB) counterpulsation device. A pivotal, multicenter US study to assess the safety and efficacy of C- Pulse in patient with Stage C and NYHA Class III or ambulatory Class IV heart failure is in progress.

Concept and first experimental results of a new ferromagnetic assist device for extra-aortic counterpulsation

Based on a ferromagnetic silicone cuff for extra-aortic counterpulsation, a new assist device concept was developed. The driving force is generated by an external magnetic field, which leads to contraction of a soft magnetic cuff. The force generation capacity of the device was tested in a silicone aorta model. Magnetic elastomers can be constructed through dispersion of micro- or nanoparticles in polymer matrices and were designed to act as soft actuators. Two magnetically active silicone cuffs were produced with a nanomagnet loading of 250 wt% (Cuff 1) and a micromagnet loading of 67 wt% (Cuff 2). The magnetic cuffs were applied on a silicone aorta model and contracted against hydrostatic pressure. A full contraction of Cuff 1 was possible against a maximal hydrostatic pressure of 30 cmH₂O (22 mmHg) at a magnetic flux density of 0.4 T (Tesla) and 65 cmH₂O (48 mmHg) at a magnetic flux density of 1.2 T. A 50% contraction of Cuff 2 was possible against a maximal hydrostatic pressure of 80 cmH₂O (59 mmHg) at a magnet-cuff-distance (MCD) of 0 cm. At MCDs of 1 and 2 cm a 50% contraction was possible against 33 cmH₂O (24 mmHg) and 10 cmH₂O (7 mmHg), respectively. Combining the advantages of magnetic elastomers with the principle of extra-aortic counterpulsation in a new assist device concept avoids the need for anticoagulation (no contact with bloodstream). With regard to the magnetic principle of action, no intra- to extracorporeal connection is needed. More experimental work is needed to further increase the force generated by the silicone cuff and to transfer the device concept into an in vivo setting.

Extra-Aortic Implantable Counterpulsation Pump in Chronic Heart Failure

Extra-aortic counterpulsation for the management of chronic heart failure is a novel approach. We report the use of an extra-aortic implantable counterpulsation pump in the management of a 73-year-old patient with severe heart failure refractory to medical therapy. The implantable counterpulsation pump prolonged his life and greatly improved its quality. The patient lived almost 7 months after the implantation of the device and died of septic complications secondary to gas line infection.

MECHANICAL ASSISTANCE FOR THE FAILING PEDIATRIC HEART

Treatment of pediatric heart failure after cardiac surgery remains a challenge. Support with pediatric intraaortic balloon pump (IAB), ventricular assist devices or ECMO is limited by availability, complexity, expense and limited efficacy. Based on the principles of extraaortic counterpulsation in adults, a miniature (10cc stroke volume) pulsatile assist device (MinEPAD) was designed and compared to IAB support in small animal model. Juvenile dogs (10–13kg) were studied under anesthesia. A 7cc pediatric IAB was inserted into the descending thoracic aorta, and the EPAD attached to mid ascending aorta. The MinEPAD is a disk-like valveless pneumatic pumping chamber made from thermo-formed polyurethane by vacuum-forming. A commercial IABP console was used to actuate the IAB or MinEPAD. Hemodynamic data were taken with each device at moderate and severe levels of induced heart failure. Both the IAB and MinEPAD demonstrated counterpulsation benefit in moderate heart failure. The MinEPAD produced greater arterial diastolic augmentation (+187% baseline vs 121%, p<0.05) and greater increases in cardiac output (+69% vs +20%, p<0.05) compared to IAB. In severe heart failure, the MinEPAD outperformed the IAB in augmentation and increasing cardiac output (+ 660% vs +120%, p<0.05). In the setting of moderate or severe heart failure, the miniature stroke volume (1Ucc) MinEPAD demonstrates magnitudes greater effectiveness compared to pediatric IAB assistance. This novel device may address an important clinical need in treating postoperative cardiac failure in pediatric patients.

Dynamic aortomyoplasty: clinical experience and thoracoscopic surgery feasibility study.

Surgical procedures using the latissimus dorsi (LD) muscle to assist chronic heart failure inflict major trauma on severely sick patients. A less invasive approach may prove beneficial. The aim of this article is to review our clinical and experimental approaches of dynamic aortomyoplasty (AMP) and emphasize the necessity to reorient surgical technique towards new directions and a less invasive thoracoscopic approach. A clinical pilot study on dynamic descending AMP started in June 1995 and included four patients. Two of them could benefit from LD counterpulsation, surviving 6 months and 18 months. Following this clinical experience, we investigated, on an animal model, minimally invasive thoracoscopic surgery for this procedure. Twelve goats underwent endoscopic LD harvest and video-assisted aortic wrap, and were studied after surgical recovery from an anatomical and functional standpoint. Clinical AMP using open techniques provided extraaortic counterpulsation in NYHA Class IV patients contraindicated for other surgical therapies. However, surgical technique and strategy needed improvements for optimal cardiac assistance and better patient outcome. Minimally invasive thoracoscopic surgery was feasible and reproducible in goats, achieving improved anatomy and physiology as compared to the open technique in humans. When appropriate the wrapping technique and stimulation protocol were used, an optimal counterpulsation was demonstrated. We concluded that thoracoscopic AMP may provide a minimally invasive approach to cardiac assistance and thus, a new surgical option for patients presenting with chronic heart failure.

Experimental Study of Extraaortic Balloon Counterpulsation as a Bridge to Other Mechanical Assists

A special extraaortic balloon was developed that can be placed around the ascending aorta. This balloon can easily support the heart temporarily in a median sternotomy field, especially in cases in which it is difficult to use intraaortic balloon pumping because of peripheral arterial disease. The goal of this study was to judge the applicability of this extraaortic balloon counterpulsation. An extraaortic balloon was placed around the ascending aorta of eight adult canines. Two heart failure models were used in this study: group A-moderate heart failure; group B-severe heart failure. In group A, the aortic systolic pressure was significantly reduced (9.3%, p < 0.01), but in group B, there was no significant change. In group A, there was a significant increase in cardiac output (12.0%, p < 0.01), but in group B, there was no significant change. The endocardial viability ratio in both groups significantly increased (group A: 11.3%, p < 0.01; group B: 11.9%, p < 0.05). An extraaortic balloon around the ascending aorta is easily applicable through a median sternotomy, and can be used as a bridge to more powerful mechanical assists when intraaortic balloon pumping cannot be used.

Experimental Study of Extraaortic Balloon Counterpulsation as a Bridge to Other Mechanical Assists

Experimental Study of Extraaortic Balloon Counterpulsation as a Bridge to Other Mechanical Assists

A single skeletal muscle powered ventricle that assists both systemic and pulmonary circulations.

Extraaortic counterpulsation using skeletal muscle powered ventricles (SMPVs) has been studied mainly for the purpose of assisting the systemic circulation. The purpose of this study was to investigate the possibility of assisting both the systemic and pulmonary circulations using a single SMPV. An SMPV that counterpulses the systemic circulation is placed beside the right atrium (RA) or the right ventricle (RV), the former after procedures such as a Fontan operation, and the latter in cases of biventricular failure. Because the SMPV dilates passively during cardiac systole, it is designed to press the RA or the RV directly from outside. This study is a preliminary report, and only the ability of a specially constructed SMPV to dilate was assessed. Using seven dogs with heart failure, the SMPV dilated with an internal pressure of 88 mmHg and 1.0 cm, while the volume inside increased by 10.8 ml. From these results, it is suggested that the SMPV has enough dilating power to press the RA or to assist the RV while counterpulsing the systemic circulation.

The muscle-powered dual-chamber counterpulsator: Rheologically superior implantable cardiac assist device

To enable long-term studies of a totally implantable cardiac assist device powered by transformed fatigue-resistant skeletal muscle, we developed a dual-chamber extraaortic counterpulsation system that uses hydraulic fluid for power transfer. Six dogs had our dual-chamber extraaortic counterpulsator implanted, 2 of which had undergone prior transformation of their latissimus dorsi muscle. The blood pump, with a Dacron graft at each end, was anastomosed end-to-side and parallel to the thoracic aorta, allowing continuous blood flow to minimize thrombus formation caused by stasis and turbulence. The blood pump was powered by a hydraulic bulb placed beneath the latissimus dorsi muscle. The latissimus dorsi muscle was stimulated to contract during diastole using a synchronized burst electrical stimulator. The ratio of diastolic pressure time product over systolic time tension index, which reflects the myocardial oxygen supply and demand ratio, was calculated from ascending aortic pressure tracings. A consistent increase in this ratio of 44% in 4 dogs with nontransformed latissimus dorsi muscle and of 70% in 2 dogs with transformed latissimus dorsi muscle was obtained when the device was activated. Preliminary chronic implantation studies using a Medtronic cardiomyo-stimulator (Model SP1005) as the burst stimulator for our dual-chamber extraaortic counterpulsator produced an average augmentation in aortic diastolic pressure of 34 mm Hg for up to six days. Our results indicate that, with further refinement of this device, a long-term totally implantable cardiac assist device powered by endogenous skeletal muscle will be feasible.

Evaluation of an extraaortic counterpulsation device in severe cardiac failure

A valveless, single-orifice polyurethane ventricle with a maximum stroke volume of 60 mL was implanted on the brachiocephalic artery just above the aortic arch in sheep (n = 14) to act as an extraaortic counterpulsation device. In parallel, an intraaortic balloon was placed in the descending thoracic aorta. Both devices were pneumatically driven with an intraaortic balloon pump console that was gated by the electrocardiogram to provide aortic diastolic augmentation at a stroke volume of 40 mL. To compare the efficacy of counterpulsation for each device during severe cardiac failure, biventricular block was induced by continuous infusion of esmolol (100 to 600 μg · kg −1 · min −1), titrated to reduce aortic flow and pressure to less than 75% of baseline. Pulsatile coronary and aortic flows were recorded with ultrasonic flow probes placed around their respective vessels. Aortic root and left ventricular pressures were recorded using micromanometers. The enhancement of hemodynamic variables for both devices were compared for optimal timing conditions, which were defined as inflation set just before the dicrotic notch and deflation bordering on isovolumetric systole. The extraaortic counterpulsation device was able to significantly augment aortic and coronary flows while simultaneously decreasing left ventricular tension time index and aortic end-diastolic pressure ( p < 0.02). The intraarotic balloon pump was able to significantly reduce only tension time index ( p < 0.002) to a lesser extent that the extraaortic counterpulsation device. All analysis was performed with the pairedsamples t test. The extraaortic counterpulsation device greatly improves the myocardial oxygen supply-consumption ratio of the left ventricle by increasing diastolic coronary flow and reducing left ventricular wall tension during systole. The salutary effects of the extraaortic counterpulsation device greatly exceed those of the intraaortic balloon pump, and it may, therefore, provide a viable alternative for patients in pump failure after cardiopulmonary bypass.

Aortic counterpulsation for up to 28 days with autologous latissimus dorsi in sheep

This article reports the development and assessment of an entirely autologous extraaortic counterpulsation system using skeletal muscle (latissimus dorsi). The technique has been performed and assessed in 16 sheep to quantify the effectiveness of counterpulsation over periods up to 28 days and to optimize the stimulation regimens for muscle contraction and fiber-type transformation. Hemodynamic changes have been quantified by calculation of the endocardial viability ratio. This has shown an increase of between 12% and 89% for 28 days. The wide variety of increase observed has been related to the development of an optimum flap configuration. The technique of surface impedance monitoring of flap blood flow has allowed the start of electrical stimulation after 48 hours with the introduction of hemodynamic benefit (1:4 mode) during the process of fiber-type transformation (in situ training). Extraaortic counterpulsation with autologous latissimus dorsi has been shown to be effective and safe for as long as 28 days. It has not been associated with any thromboembolic or infective complications, which we attribute to the exclusion of any foreign material in the design.