Chronic Mechanical Circulatory Support for Inotrope-Dependent Heart Failure Patients Who Are Not Transplant Candidates

Ventricular assist devices: is destination therapy a viable alternative in the non-transplant candidate?

The topic of this article, stated a more familiar way, is whether left ventricular assist devices (LVADs) are ready for 'Primetime' as a therapeutic option in and of themselves. In order to provide an update and insight on this question, we briefly review from where the field has come, and in more detail describe its current state and where we are heading. We believe the short answer to this question is 'Yes', but like many things, a short answer is not adequate. Here we attempt to deliver a more comprehensive answer, providing some historical context, outlining the great achievements that have been made, as well as the many challenges that still remain before LVADs become a truly mainstream therapy.

Fundus fluorescein angiographic findings in patients who underwent ventricular assist device implantation

Disruption of microcirculation in various tissues as a result of deformed blood rheology due to ventricular assist device (VAD) implantation causes novel arteriovenous malformations. Capillary disturbances and related vascular leakage in the retina and choroidea may also be seen in patients supported by VADs. We aimed to evaluate retinal vasculature deteriorations after VAD implantation. The charts of 17 patients who underwent VAD implantation surgery for the treatment of end-stage heart failure were retrospectively reviewed. Eight cases (47.1%) underwent pulsatile pump implantation (Berlin Heart EXCOR, Berlin Heart Mediprodukt GmbH, Berlin, Germany); however, nine cases (52.9%) had continuous-flow pump using centrifugal design (HeartWare, HeartWare Inc., Miramar, FL, USA). Study participants were selected among the patients who had survived with a VAD for at least 6 months, and results of detailed ophthalmologic examinations including optic coherence tomography (OCT) and fundus fluorescein angiography (FA) were documented. All of the 17 patients were male, with a mean age of 48.5 ± 14.8 years (15-67 years). Detailed ophthalmologic examinations including the evaluation of retinal vascular deteriorations via FA were performed at a mean of 11.8 ± 3.7 months of follow-up (6-18 months). Mean best-corrected visual acuity and intraocular pressure were found as logMAR 0.02 ± 0.08 and 14.6 ± 1.9 mm Hg, respectively in the study population. Dilated fundoscopy revealed severe focal arteriolar narrowing in two patients (11.8%), and arteriovenous crossing changes in four patients (23.5%); however, no pathological alteration was present in macular OCT scans. In patients with continuous-flow blood pumps, mean arm-retina circulation time (ARCT) and arteriovenous transit time (AVTT) were found to be 16.8 ± 3.0 and 12.4 ± 6.2 s, respectively; whereas those with pulsatile-flow blood pumps were found to be 17.4 ± 3.6 and 14.0 ± 2.1 s in patients (P=0.526 and P=0.356, respectively). FA also revealed a tendency for increased frequency of dye leakage from the optic disc in our study population. Except for remarkable delays in both ARCT and AVTT as well as a tendency for increased frequency of dye leakage from the optic disc, ophthalmologic evaluations revealed no other significant pathology or vascular deterioration in the retina that could be attributed to artificial heart systems.

The perioperative management of patients with left ventricular assist devices undergoing noncardiac surgery

OBJECTIVE

To describe the perioperative management of patients with left ventricular assist devices (LVADs) who require general anesthesia while undergoing noncardiac surgery (NCS) at a single, large tertiary referral center.

PATIENTS AND METHODS

Electronic medical records from September 2, 2005, through May 31, 2012, were retrospectively reviewed to evaluate the perioperative management and outcomes in LVAD patients undergoing NCS. Patients were included only if they required a general anesthetic and had previously been discharged from the hospital after initial LVAD implantation.

RESULTS

Thirty-three patients with LVADs underwent general anesthesia for 67 noncardiac operations. The mean ± SD time from LVAD implantation to NCS was 317 ± 349 days. All but 1 patient had axial flow LVADs. Anticoagulation or antiplatelet agents were present within 7 days before NCS in 49 procedures (73%) and reversed in 32 of 49 (65%). No perioperative thrombotic complications related to anticoagulation or antiplatelet reversal were noted. Red blood cell, fresh frozen plasma, and platelet transfusions were administered during 10, 6, and 4 operations, respectively. The only intraoperative complication was surgical bleeding. Postoperative complications were present in 12 patients after NCS and were mainly composed of bleeding. Three patients died within 30 days of NCS, with the causes of death not attributed to NCS.

CONCLUSION

Patients with LVAD safely underwent NCS in a multidisciplinary setting that included preoperative optimization by cardiologists familiar with LVADs when feasible. Anticoagulation or antiplatelet agents were present preoperatively in most patients with LVADs and were safely reversed when necessary for NCS. The relatively high occurrence of postoperative bleeding is consistent with previous series.

Advances and future directions for mechanical circulatory support

Although cardiac transplant remains the gold standard for the treatment of end-stage heart failure, limited donor organ availability and growing numbers of eligible recipients have increased the demand for alternative therapies. Limitations of first-generation left ventricular assist devices for long-term support of patients with end-stage disease have led to the development of newer second-generation and third-generation pumps, which are smaller, have fewer moving parts, and have shown improved durability, allowing for extended support. The HeartMate II (second generation) and HeartWare (third generation) are 2 devices that have shown great promise as potential alternatives to transplantation in select patients.

Elevation of Plasma Milrinone Concentrations in Stage D Heart Failure Associated With Renal Dysfunction

Purpose:

To determine steady state milrinone concentrations in patients with stage D heart failure (HF) with and without renal dysfunction

Methods:

We retrospectively identified patients with stage D HF at a single medical center on continuous milrinone infusion at the time of plasma collection for entry into a research registry database. Milrinone was prescribed and titrated to improve hemodynamic and clinical status by a cardiologist. Plasma samples were obtained at steady state milrinone concentrations. Patients were stratified by creatinine clearance (CrCl) into 4 groups: group 1 (CrCl >60 mL/min), group 2 (CrCl 60-30 mL/min), group 3 (CrCl <30 mL/min), and group 4 (intermittent hemodialysis). Retrospective chart review was performed to quantify the postmilrinone hemodynamic changes by cardiac catheterization and electrophysiologic changes by implantable cardiac defibrillator (ICD) interrogation.

Results:

A total of 29 patients were identified: group 1 (n = 14), group 2 (n = 10), group 3 (n = 3), and group 4 (n = 2). The mean infusion rate (0.391 ± 0.08 µg/kg/min) did not differ between groups ( P = 0.14). The mean milrinone concentration was 451± 243 ng/mL in group 1, 591 ± 293 ng/mL in group 2, 1575 ± 962 ng/mL in group 3, and 6252 ± 4409 ng/mL in group 4 ( P<0.05 compared to groups 1). There was no difference in postmilrinone hemodynamic improvements between the groups ( P=0.41). The ICD interrogation revealed limited comparisons, but 6 of the 8 postmilrinone ventricular tachycardia episodes requiring defibrillation occurred in group 4 patients.

Conclusion:

Patients with stage D HF having severe renal dysfunction have elevated milrinone concentrations. Future studies of milrinone concentrations are warranted to investigate the potential risk of life-threatening arrhythmias and potential dosing regimens in renal dysfunction.

Heart failure and mechanical circulatory assist devices

During the last 20 years, the management of heart failure has significantly improved by means of new pharmacotherapies, more timely invasive treatments and device assisted therapies. Indeed, advances in mechanical support, namely with the development of more efficient left ventricular assist devices (LVAD), and the total artificial heart have reduced mortality and morbidity in patients with end-stage heart failure awaiting for transplantation. However, the transplant cannot be the only solution, due to an insufficient number of available donors, but also because of the high number of patients who are not candidates for severe comorbidities or advanced age. New perspectives are emerging in which the VAD is no longer conceived only as a “Bridge to Transplant”, but is now seen as a destination therapy. In this review, the main VAD classification, current basic indications, functioning modalities, main limitations of surgical VAD and the total artificial heart development are described.

Durability of left ventricular assist devices: Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) 2006 to 2011

OBJECTIVES

The present study compared the interval until device exchange or death from pump-related failure in patients with pulsatile versus continuous flow left ventricular assist devices.

METHODS

Data from Interagency Registry for Mechanically Assisted Circulatory Support (June 23, 2006, to March 31, 2011) compared the durability of implanted pulsatile and continuous flow left ventricular assist devices. The durability issues included pump replacement for infection, thrombosis-hemolysis, driveline failure, or pump drive unit failure, and death from driveline or pump drive unit failure.

RESULTS

A total of 3302 left ventricular assist devices were implanted (486 pulsatile, 2816 continuous flow) and 98 pump exchanges or deaths from durability issues (46 pulsatile, 52 continuous flow; 3% of implants). The interval to device issue was greater for the continuous flow than for the pulsatile devices (P < .001). A comparisons of the causes for pump exchange or pump-related death showed (1) greater freedom from pump failure in the continuous flow compared with the pulsatile left ventricular assist devices (10 events/2816 continuous flow implants vs 39 events/486 pulsatile implants; P < .0001); (2) similar exchange or pump-related death for driveline failure (1/486 pulsatile vs 7/2816 continuous flow; P = .82); (3) similar exchange or pump-related death for thrombosis-hemolysis (2/486 pulsatile vs 28/2816 continuous flow; P = .25); and (4) fewer exchanges or pump-related deaths from infection in continuous flow left ventricular assist devices (4/486 pulsatile vs 7/2816 continuous flow; P = .034). Competing outcomes analysis corroborated this finding, with 54% of continuous flow versus 23% of pulsatile patients alive and receiving support at 12 months after implantation.

CONCLUSIONS

The Analysis of Interagency Registry for Mechanically Assisted Circulatory Support data showed greater durability for continuous flow than for pulsatile left ventricular assist devices. Even longer durations of support can be expected if pump durability continues to improve.

Verification of a computational cardiovascular system model comparing the hemodynamics of a continuous flow to a synchronous valveless pulsatile flow left ventricular assist device

The purpose of this investigation is to use a computational model to compare a synchronized valveless pulsatile left ventricular assist device with continuous flow left ventricular assist devices at the same level of device flow, and to verify the model with in vivo porcine data. A dynamic system model of the human cardiovascular system was developed to simulate the support of a healthy or failing native heart from a continuous flow left ventricular assist device or a synchronous pulsatile valveless dual-piston positive displacement pump. These results were compared with measurements made during in vivo porcine experiments. Results from the simulation model and from the in vivo counterpart show that the pulsatile pump provides higher cardiac output, left ventricular unloading, cardiac pulsatility, and aortic valve flow as compared with the continuous flow model at the same level of support. The dynamic system model developed for this investigation can effectively simulate human cardiovascular support by a synchronous pulsatile or continuous flow ventricular assist device.

Treatment options in end-stage heart failure: where to go from here?

Chronic heart failure is a major healthcare problem associated with high morbidity and mortality. Despite significant progress in treatment strategies, the prognosis of heart failure patients remains poor. The golden standard treatment for heart failure is heart transplantation after failure of medical therapy, surgery and/or cardiac resynchronisation therapy. In order to improve patients’ outcome and quality of life, new emerging treatment modalities are currently being investigated, including mechanical cardiac support devices, of which the left ventricular assist device is the most promising treatment option. Structured care for heart failure patients according to the most recent international heart failure guidelines may further contribute to optimal decision-making. This article will review the conventional and novel treatment modalities of heart failure.

Third-generation continuous flow left ventricular assist devices

Tremendous advances have been made in the treatment of end-stage heart failure patients with left ventricular assist devices (LVADs). An important factor playing a role in the improved clinical outcomes is the development of continuous flow, rotary LVADs. New technology using magnetic levitation and hydrodynamic suspension to eliminate contact bearings offers the potential of more durable and efficacious mechanical circulatory blood pumps. Clinical trials evaluating these novel "third-generation" LVADs are in progress.

Current status of mechanical circulatory support: a systematic review

Heart failure is a major public health problem and its management requires a significant amount of health care resources. Even with administration of the best available medical treatment, the mortality associated with the disease remains high. As therapeutical strategies for heart failure have been refined, the number of patients suffering from the disease has expanded dramatically. Although heart transplantation still represents the gold standard therapeutical approach, the implantation of mechanical circulatory support devices (MCSDs) evolved to a well-established management for this disease. The limited applicability of heart transplantation caused by a shortage of donor organs and the concurrent expand of the patient population with end-stage heart failure led to a considerable utilization of MCSDs. This paper outlines the current status of mechanical circulatory support.