Endocrine function is not impaired in patients with a continuous MicroMed–DeBakey axial flow pump

Euthyroid sick syndrome in paediatric and adult patients requiring extracorporeal circulatory support and the role of thyroid hormone supplementation: a review

Non-thyroid disorders may modify thyroid hormone metabolism, resulting in an 'euthyroid sick syndrome'. Studies determining the association of cardiopulmonary bypass to thyroid function showed changes in line with this euthyroid sick syndrome. In some cases, cardiovascular dysfunction after cardiac surgery with cardiopulmonary bypass is comparable to that noticed in hypothyroidism associated with low cardiac output and elevated systemic vascular resistance. Numerous lines of research have proposed that triiodothyronine can behave acutely as a positive inotropic and vasodilator agent. The aim of this review is to present an update on the current literature about in what clinical situations the use of thyroid supplementation during the perioperative period of extracorporeal circulation in the adult and paediatric populations may impact outcome to any appreciable degree. The contribution of thyroid function in patients undergoing a ventricular assist device implantation is additionally reviewed and future study directions are proposed. This is a narrative review, where the search strategy consisted on retrieving the articles through an extensive literature search performed using electronic databases from January 1978 up to September 2019. All controlled trials randomly allocating to perioperative thyroid hormone administration in children and adults undergoing extracorporeal circulation for cardiac surgery were considered. Thyroid hormone supplementation may be recommended particularly in selected paediatric sub-populations. There is currently no firm evidence regarding the benefits of routine use of thyroid hormone administration in cardiac adult patients. Further studies are required to assess the beneficial effect of thyroid hormone on patients with end-stage heart failure supported by ventricular assist devices.

Physiologic effects of continuous-flow left ventricular assist devices

BACKGROUND

Within the past 10 years, continuous-flow left ventricular assist devices (LVADs) have replaced pulsatile-flow LVADs as the standard of care for both destination therapy and bridging patients to heart transplantation. Despite the rapid clinical adoption of continuous-flow LVADs, an understanding of the effects of continuous-flow physiology, as opposed to more natural pulsatile-flow physiology, is still evolving.

MATERIALS AND METHODS

A thorough review of the relevant scientific literature regarding the physiological and clinical effects of continuous-flow physiology was performed. These effects were analyzed on an organ system basis and include an evaluation of the cardiovascular, respiratory, hematologic, gastrointestinal, renal, hepatic, neurologic, immunologic, and endocrine systems.

RESULTS

Continuous-flow physiology is, generally speaking, well tolerated over the long term. However, several changes are manifest at the organ system level. Although many of these changes are without appreciable clinical significance, other changes, such as an increased rate of gastrointestinal bleeding, appear to be associated with continuous-flow physiology.

CONCLUSIONS

Continuous-flow LVADs confer a significant advantage over their pulsatile-flow counterparts with regard to size and durability. From a physiological standpoint, continuous-flow physiology has limited clinical effects at the organ system level. Although improved over previous generations, challenges with this technology remain. Approaching these problems with a combination of clinical and engineering solutions may be needed to achieve continued progression in the field of durable mechanical circulatory support.

Rotary Blood Pumps as Long-Term Mechanical Circulatory Support: A Review of a 15-Year Berlin Experience

This article reports our 15-year single-center experience with rotary blood pumps (RBPs) as long-term mechanical circulatory support (MCS) with emphasis on outcomes. For more than 15-year period, we have used various RBPs as bridge to transplantation or to myocardial recovery. Our group performed the first human implantation worldwide of RBCs, the MicroMed DeBakey ventricular assist device in November 1998 in a patient with end-stage heart failure who was supported for 47 days until his death. Based on this initial experience, we recognized the feasibility of providing long-term support and since then it has been our primary armamentarium in treating patients with heart failure. Between 1987 and September 2013, we have implanted 2208 ventricular assist devices ranging from pulsatile to continuous-flow systems, as short-term, long-term, or permanent support in patients with end-stage heart failure. In total, 1009 RBPs were implanted on 908 patients, and their outcomes are reported here. We have shared some milestones in MCS including the first implantation of Jarvik 2000 on the oldest patient (81-year old) in 2008 and the first worldwide implantation of a biventricular HeartWare. Over time, implantation techniques, anticoagulation, and postoperative care have been modified and individualized. A relevant aspect of our experience has been the incidence of pump thrombosis. This is particularly frustrating because the problem has occurred in the setting of full anticoagulation and antiplatelet therapy, guided by strict anticoagulation monitoring. It has become clear to us that the devices are still not perfect. Technical pump failures such as cable breaks also occur, prompting urgent pump exchange, and infection. A 15-year cumulative mortality rate is 46.9%. This report emphasizes that MCS with RBPs has evolved into a routine treatment in heart failure and is a highly feasible option for permanent therapy particularly for elderly patients.

Comparison of continuous-flow and pulsatile-flow left ventricular assist devices: is there an advantage to pulsatility?

BACKGROUND

Continuous-flow left ventricular assist devices (CFVAD) are currently the most widely used type of mechanical circulatory support as bridge-to-transplant and destination therapy for end-stage congestive heart failure (HF). Compared to the first generation pulsatile-flow left ventricular assist devices (PFVADs), CFVADs have demonstrated improved reliability and durability. However, CFVADs have also been associated with certain complications thought to be linked with decreased arterial pulsatility. Previous studies comparing CFVADs and PFVADs have presented conflicting results. It is important to understand the outcome differences between CFVAD and PFVAD in order to further advance the current VAD technology.

METHODS

In this review, we compared the outcomes of CFVADs and PFVADs and examined the need for arterial pulsatility for the future generation of mechanical circulatory support.

RESULTS

CVADs offer advantages of smaller size, increased reliability and durability, and subsequent improvements in survival. However, with the increasing duration of long-term support, it appears that CFVADs may have specific complications and a lower rate of left ventricular recovery associated with diminished pulsatility, increased pressure gradients on the aortic valve and decreased compliance in smaller arterial vessels. PFVAD support or pulsatility control algorithms in CFVADs could be beneficial and potentially necessary for long term support.

CONCLUSIONS

Given the relative advantages and disadvantages of CFVADs and PFVADs, the ultimate solution may lie in incorporating pulsatility into current and emerging CFVADs whilst retaining their existing benefits. Future studies examining physiologic responses, end-organ function and LV remodeling at varying degrees of pulsatility and device support levels are needed.

Physiologic and hematologic concerns of rotary blood pumps: what needs to be improved?

Over the past few decades, advances in ventricular assist device (VAD) technology have provided a promising therapeutic strategy to treat heart failure patients. Despite the improved performance and encouraging clinical outcomes of the new generation of VADs based on rotary blood pumps (RBPs), their physiologic and hematologic effects are controversial. Currently, clinically available RBPs run at constant speed, which results in limited control over cardiac workload and introduces blood flow with reduced pulsatility into the circulation. In this review, we first provide an update on the new challenges of mechanical circulatory support using rotary pumps including blood trauma, increased non-surgical bleeding rate, limited cardiac unloading, vascular malformations, end-organ function, and aortic valve insufficiency. Since the non-physiologic flow characteristic of these devices is one of the main subjects of scientific debate in the literature, we next emphasize the latest research regarding the development of a pulsatile RBP. Finally, we offer an outlook for future research in the field.

Rotary blood pumps as definitive treatment for severe heart failure

Rotary blood pumps are increasingly recognized as mainstream therapy for severely symptomatic heart failure. Carefully targeted refinements in patient selection and postoperative care have substantially reduced the adverse event burden. These improvements translate into better survival and quality of life in comparison with medical management. Medium-term outcomes now compete favorably with cardiac transplantation, although evidence-based outcome data indicate that transplant and ‘lifetime’ left ventricular-assist device (LVAD) candidates are fundamentally different. Significant challenges remain in relation to neurological injury and right heart failure, which may continue to limit exercise capacity. In the meantime, both physician awareness and patient access to LVAD technology remain limited. The debate is rarely between cardiac transplant or lifetime LVAD. It should focus on the choice between pump versus palliative care for the thousands of patients of all age groups who are judged ineligible for transplantation. Comprehensive healthcare systems must consider contemporary evidence and provide the most symptomatic of heart failure patients with effective care. Cardiac resynchronization therapy is no longer the ceiling for this.

Past and present of cardiocirculatory assist devices: a comprehensive critical review

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 (LVADs), and the total artificial heart have reduced mortality and morbidity in patients awaiting transplantation, so much so, that LVADs are now approved of as a strategy for destination therapy. In this review, the authors describe in detail the current basic indications, functioning modalities, main limitations of surgical LAVDs, total artificial heart development, and percutaneous assist devices, trying to clarify this complex, but fascinating topic.

Pulsatile vs. continuous flow in ventricular assist device therapy

A left ventricular assist device (LVAD) is an important treatment option for a patient with end-stage heart failure. Both continuous and non-pulsatile devices are available, each with different effects on a patient's physiology. In general, these effects are not clinically significant with the exception of bleeding events which are more common with continuous-flow devices in some series. Both devices increase survival beyond medical management. Continuous-flow devices are smaller and are associated with less overall morbidity than pulsatile devices.

The current status of heart transplantation and the development of "artificial heart systems"

BACKGROUND

In view of the major technical advances in ventricular assist devices (VAD) in recent years, the authors discuss the question whether these "artificial hearts" are still no more than a temporary measure for patients awaiting heart transplantation (HTx), or whether they can already be used as an independent form of long-term treatment.

METHODS

Statistics from Eurotransplant regarding heart transplantations and transplant waiting lists in Germany are presented. Technical developments in cardiac support systems, the variation in results depending on the indication, and the findings with respect to quality of life are all discussed on the basis of a selective review of the literature and the authors' own clinical experience.

RESULTS

The waiting list for heart transplantation in Germany has grown to a record size of nearly 800 patients, while fewer than 400 hearts are transplanted each year. Technical advances have improved outcomes in VAD therapy, but the outcome depends on the patient's preoperative condition. The physical performance of patients who have received VAD is comparable to that of HTx patients; nonetheless, HTx patients have a better quality of life.

CONCLUSIONS

Chronic VAD therapy has become a clinical reality. Because of the greater number of patients awaiting HTx, many will not receive their transplants in time. When the decision to treat with VAD is made early, it can be used as an alternative form of treatment with a comparable one-year survival (>75%).

Prospective Randomized Comparison of Coronary Bypass Grafting With Minimal Extracorporeal Circulation System (MECC) Versus Off-Pump Coronary Surgery

BACKGROUND

We aimed to evaluate the clinical results and biocompatibility of the minimal extracorporeal circulation system (MECC) compared with off-pump coronary revascularization (OPCABG).

METHODS AND RESULTS

In a prospective randomized study, 150 patients underwent coronary surgery with the use of MECC and 150 underwent OPCABG. End points were (1) circulating markers of inflammation and organ injury, (2) operative results, and (3) outcome at 1-year follow-up. Operative mortality and morbidity were comparable between the groups. Release of inflammatory markers was similar between groups at all time points (peak interleukin-6 167.2+/-13.5 versus 181+/-6.5 pg/mL, P=0.14, OPCABG versus MECC group, respectively). Peak creatine kinase was 419.3+/-103.5 versus 326+/-84.2 mg/dL (P=0.28), and peak S-100 protein was 0.13+/-0.08 versus 0.29+/-0.1 pg/mL (P=0.058, OPCABG versus MECC group, respectively). Length of hospital stay and use of blood products were similar between groups. Two cases of angina recurrence at 1 year in the MECC group were observed versus 5 cases observed in the OPCABG group (P=0.44). A residual perfusion defect at myocardial nuclear scan was less frequent among patients in the MECC group (3 versus 9 cases, P=0.14; odds ratio 0.32, 95% confidence interval 0.07 to 1.32). Six (OPCABG group) versus 3 (MECC group) coronary grafts were occluded or severely stenotic at 1 year (P=0.33, odds ratio 0.47, 95% confidence interval 0.09 to 2.14).

CONCLUSIONS

Clinical results of coronary revascularization with MECC are optimal when this procedure is performed by experienced teams. Postoperative morbidity is comparable to that with OPCABG. MECC is associated with little pump-related systemic and organ injury. It may achieve the benefits of OPCABG (less morbidity in high-risk patients) while facilitating complete revascularization in the case of complex lesions unsuitable for OPCABG.