Abnormal mitochondrial L-arginine transport contributes to the pathogenesis of heart failure and rexoygenation injury

Impaired mitochondrial function is fundamental feature of heart failure (HF) and myocardial ischemia. In addition to the effects of heightened oxidative stress, altered nitric oxide (NO) metabolism, generated by a mitochondrial NO synthase, has also been proposed to impact upon mitochondrial function. However, the mechanism responsible for arginine transport into mitochondria and the effect of HF on such a process is unknown. We therefore aimed to characterize mitochondrial L-arginine transport and to investigate the hypothesis that impaired mitochondrial L-arginine transport plays a key role in the pathogenesis of heart failure and myocardial injury.

Analysis of cardioprotective effects using purified Saliva miltiorrhiza extract on isolated rat hearts

The purpose of the current study is to evaluate the cardioprotective effects of purified Salvia miltiorrhiza extract (PSME) on myocardial ischemia/reperfusion injury in isolated rat hearts. Hearts were excised and perfused at constant flow (7 – 9 ml · min⁻¹) via the aorta. Non-recirculating perfusion with Krebs-Henseleit (KH) solution was maintained at 37°C and continuously gassed with 95% O₂ and 5% CO₂. KH solution with or without PSME (100 mg per liter solution) was used after 30-min zero-flow ischemia for the PSME and control group, respectively. Left ventricular (LV) developed pressure; its derivatives, diastolic pressure, and so on were continuously recorded via a pressure transducer attached to a polyvinylchloride balloon that was placed in the left ventricle through an incision in the left atrium. PSME treated hearts showed significant postischemic contractile function recovery (developed pressure recovered to 44.2 ± 4.9% versus 17.1 ± 5.7%, P<0.05; maximum contraction recovered to 57.2 ± 5.9% versus 15.1 ± 6.3%, P<0.001; maximum relaxation restored to 69.3 ± 7.3% versus 15.4 ± 6.3%, P<0.001 in the PSME and control group, respectively). Significant elevation in end-diastolic pressure, which indicated LV stiffening in PSME hearts might have resulted from the excess high dose of PSME used. Further study will be conducted on the potential therapeutic value with lower dose of PSME on prevention of ischemic heart disease.

Reperfusion-induced myocardial dysfunction is prevented by endogenous annexin-A1 and its N-terminal-derived peptide Ac-ANX-A12-26

BACKGROUND AND PURPOSE : Annexin-A1 (ANX-A1) is an endogenous, glucocorticoid-regulated anti-inflammatory protein. The N-terminal-derived peptide Ac-ANX-A12–26 preserves cardiomyocyte viability, but the impact of ANX-A1-peptides on cardiac contractility is unknown. We now test the hypothesis that ANX-A1 preserves post-ischaemic recovery of left ventricular (LV) function.

EXPERIMENTAL APPROACH : Ac-ANX-A12–26 was administered on reperfusion, to adult rat cardiomyocytes as well as hearts isolated from rats, wild-type mice and mice deficient in endogenous ANX-A1 (ANX-A1–/–). Myocardial viability and recovery of LV function were determined.

KEY RESULTS: Ischaemia–reperfusion markedly impaired both cardiomyocyte viability and recovery of LV function by 60%. Treatment with exogenous Ac-ANX-A12–26 at the onset of reperfusion prevented cardiomyocyte injury and significantly improved recovery of LV function, in both intact rat and wild-type mouse hearts. Ac-ANX-A12–26 cardioprotection was abolished by either formyl peptide receptor (FPR)-nonselective or FPR1-selective antagonists, Boc2 and cyclosporin H, but was relatively insensitive to the FPR2-selective antagonist QuinC7. ANX-A1-induced cardioprotection was associated with increased phosphorylation of the cell survival kinase Akt. ANX-A1−/− exaggerated impairment of post-ischaemic recovery of LV function, in addition to selective LV FPR1 down-regulation.

CONCLUSIONS AND IMPLICATIONS : These data represent the first evidence that ANX-A1 affects myocardial function. Our findings suggest ANX-A1 is an endogenous regulator of post-ischaemic recovery of LV function. Furthermore, the ANX-A1-derived peptide Ac-ANX-A12–26 on reperfusion rescues LV function, probably via activation of FPR1. ANX-A1-based therapies may thus represent a novel clinical approach for the prevention and treatment of myocardial reperfusion injury.

Remotely delivered exercise-based cardiac rehabilitation: design and content development of a novel mHealth platform

BACKGROUND: Participation in traditional center-based cardiac rehabilitation exercise programs (exCR) is limited by accessibility barriers. Mobile health (mHealth) technologies can overcome these barriers while preserving critical attributes of center-based exCR monitoring and coaching, but these opportunities have not yet been capitalized on.

OBJECTIVE: We aimed to design and develop an evidence- and theory-based mHealth platform for remote delivery of exCR to any geographical location.

METHODS: An iterative process was used to design and develop an evidence- and theory-based mHealth platform (REMOTE-CR) that provides real-time remote exercise monitoring and coaching, behavior change education, and social support.

RESULTS: The REMOTE-CR platform comprises a commercially available smartphone and wearable sensor, custom smartphone and Web-based applications (apps), and a custom middleware. The platform allows exCR specialists to monitor patients' exercise and provide individualized coaching in real-time, from almost any location, and provide behavior change education and social support. Intervention content incorporates Social Cognitive Theory, Self-determination Theory, and a taxonomy of behavior change techniques. Exercise components are based on guidelines for clinical exercise prescription.

CONCLUSIONS: The REMOTE-CR platform extends the capabilities of previous telehealth exCR platforms and narrows the gap between existing center- and home-based exCR services. REMOTE-CR can complement center-based exCR by providing an alternative option for patients whose needs are not being met. Remotely monitored exCR may be more cost-effective than establishing additional center-based programs. The effectiveness and acceptability of REMOTE-CR are now being evaluated in a noninferiority randomized controlled trial.

Hemodynamic team decision making in the cardiac surgical intensive care context

Purpose
The purpose of this study was to explore the extent and sources of variability of critical care nurses’ hemodynamic decision making as a function of contextual factors in the immediate 2-hour period after cardiac surgery.

Methods
A qualitative exploratory design with observation and interview was used. Eight critical care nurses were observed on different occasions in clinical practice for a 2-hour period. A brief interview immediately followed each observation to clarify observation data.

Findings
Analysis of the data revealed that patient management decisions were made both by individual nurses and by a team of nurses and health professionals. Team decision making (TDM) is described in this study as integrated or non-integrated and refers to an intra-professional nursing team. During displays of integrated TDM, the primary nurse, who was assigned to care for the patient, made most hemodynamic decisions and nurses who assisted the primary nurse deferred decisions. During displays of non-integrated TDM, nurses assisting the primary nurse assumed responsibilities for most patient-related decisions. Non-integrated TDM occurred more frequently when inexperienced cardiac surgical intensive care nurses were in the role of primary nurse, whereas integrated TDM was more common among experienced cardiac surgical intensive care nurses.

Conclusions
This observed variability can occur in multiple ways and in hemodynamic decision making has implications for patient outcomes as behaviors of non-integrated TDM led to nurses sensing a loss of control of patient management.

Postoperative pulmonary dysfunction in adults after cardiac surgery with cardiopulmonary bypass: clinical significance and implications for practice

Postoperative pulmonary complications are the most frequent and significant contributor to morbidity, mortality, and costs associated with hospitalization. Interestingly, despite the prevalence of these complications in cardiac surgical patients, recognition, diagnosis, and management of this problem vary widely. In addition, little information is available on the continuum between routine postoperative pulmonary dysfunction and postoperative pulmonary complications. The course of events from pulmonary dysfunction associated with surgery to discharge from the hospital in cardiac patients is largely unexplored. In the absence of evidence-based practice guidelines for the care of cardiac surgical patients with postoperative pulmonary dysfunction, an understanding of the path ophysiological basis of the development of postoperative pulmonary complications is fundamental to enable clinicians to assess the value of current management interventions. Previous research on postoperative pulmonary dysfunction in adults undergoing cardiac surgery is reviewed, with an emphasis on the pathogenesis of this problem, implications for clinical nursing practice, and possibilities for future research.

The haemodynamic status of cardiac surgical patients in the initial 2-h recovery period

Background
Critical care nurses caring for cardiac patients in the immediate postoperative period continually make decisions about the implications and treatment of their patients' haemodynamic status.

Aim
The aim of this study was to describe the haemodynamic status of patients on admission to critical care and over the 2-h period following cardiac surgery.

Methods
A quantitative, descriptive design was used. Data were collected using non-participant observation and an observation tool. The sample consisted of 38 patients.

Results
Analysis of data revealed the dynamic nature of the haemodynamic status of postoperative cardiac patients. On admission, 60% of patients (n = 23) were haemodynamically unstable. The instability in these patients (n = 23) was due to hypotension (34%), bleeding (21%) and hypoxaemia (18%). During the 2-h recovery period, 55% of patients were hypotensive, 16% of patients had low cardiac output syndrome and 16% of patients had low systemic vascular resistance (SVR) syndrome. Twenty-one percent of patients experienced bleeding complications. Shivering was a clinically significant problem in terms of occurrence (23%) and duration (X = 45, S.D. = 30 min). Twenty-nine percent of patients (n = 11) had a profound deterioration in haemodynamic status, necessitating urgent interventions.

Conclusion
Haemodynamic parameters indicate that 95% of patients in this study were haemodynamically unstable at some time during the initial 2-h recovery period. These findings inform resourcing decisions by organisations and have implications for nurses' assessment and interventional haemodynamic decision making.

Haemodynamic instability after cardiac surgery: nurses` perceptions of clinical decision-making

Background. Cardiac surgical patients are distinguished by their potential for instability in the early postoperative period, highly invasive haemodynamic monitoring technologies and unique clinical presentations as a result of undergoing cardiopulmonary bypass. Little is known about nurses’ perceptions of assuming responsibility for such patients. An nderstanding of nurses’ perceptions may identify areas of practice that can be improved and assist in determining the adequacy of current decision supports.

Aim. The aim of this study was to describe critical care nurses’ perceptions of assuming responsibility for the nursing management of cardiac patients in the initial two-hour postoperative period. Design. An exploratory descriptive study based on naturalistic decision-making.

Methods. Thirty-eight nurses were interviewed immediately following a two-hour observation of their clinical practice. Content analysis and a systematic thematic analysis process called ‘Framework’ were used to analyse the interview transcripts.

Results. Nurses described their perceptions of managing patients in terms of how they felt about making decisions for complex cardiac surgical patients and in terms of how clinical processes unique to the admission phase impacted their decision-making. Nurses felt either daunted or stimulated and challenged when making decisions. Nurses identified handover from anaesthetists, settling in procedures and forms of
collegial assistance as important processes that impacted their decision-making.

Conclusion. Nurses’ previous experiences with similar patients influenced how they felt about making decisions during the initial two-hour postoperative period, but did not alter their views about processes important for patient safety during this time. Relevance to clinical practice. Feelings expressed by nurses in this study highlight the need for clinical supervision and appropriate allocation of resources during the immediate recovery period after cardiac surgery. Nurses identified ways to improve clinical processes that impacted their decision-making during the immediate recovery of cardiac surgical patients.

The influence of patient complexity and nurses` experience on haemodynamic decision-making following cardiac surgery

Critical care nurses’ haemodynamic decision-making in the immediate postoperative cardiac surgical context is complex. To optimise patient outcomes, nurses of varying levels of experience are required to make complex decisions rapidly and accurately. In a dynamic clinical context such as critical care, the quality of such decision-making is likely to vary considerably. The aim of this study was to describe variability of nurses’ haemodynamic decision-making in the 2-hour period after cardiac surgery as a function of interplay between decision complexity, nurses’ levels of experience, and the support provided. A descriptive study based on naturalistic decision-making was used. Data were collected using continuous non-participant observation of clinical practice for a 2-hour period and follow-up interview. Purposive sampling was used to recruit 38 nurses for inclusion in the study. The quality of nurses’ decision-making was influenced by interplay between the complexity of patients’ haemodynamic presentations, nurses’ levels of cardiac surgical intensive care experience, and the form of decision support provided by nursing colleagues. Two factors specifically influenced decision-making quality: nurses’ utilisation of evidence for practice and the experience levels of both nurses and their colleagues. The findings have implications for staff resourcing decisions and postoperative patient management, and may be used to inform nurses’ professional development and education.

Issues in the provision of nursing care to people undergoing cardiac surgery who also have type 2 diabetes

There has been little investigation of the issues associated with caring for patients presenting for cardiac surgery with a comorbid diagnosis of diabetes although there is some evidence that the diabetes management is suboptimal. This study aimed to identify issues that patients and cardiac specialist nurses experience with the provision of inpatient services for people undergoing cardiac surgery who also have type 2 diabetes. A qualitative interpretive design, using individual interviews with patients and nurses, provided data about some of these issues. The study found that nurses had high levels of confidence in their cardiac care but little confidence in diabetes management. Patients described concerns about their diabetes care and treatment regimens. A 'typical journey' for a person with diabetes undergoing cardiac surgery was identified. The findings support the need to build increased capacity in specialist nurses to support diabetes care as a secondary diagnosis.

Financial, family, and social factors impacting on cardiac rehabilitation attendance

Background
Attendance in phase 2 cardiac rehabilitation program after acute myocardial infarction is poor.

Objective
To identify and explore the demographic factors that influence peoples’ decisions to attend cardiac rehabilitation programs.

Methods
A descriptive-interpretive design was used. Semi-structured interviews were conducted with 10 people post infarction in Victoria, Australia after their first scheduled appointment to attend outpatient cardiac rehabilitation. The interview transcripts were thematically analysed.

Results
The perceived relevance of cardiac rehabilitation related to the context of people’s lives, namely their financial, family and social situation, and how important program outcomes were seen to be relevant to this context.

Conclusion
The findings of this study suggest that there are a proportion of people unlikely to attend outpatient cardiac rehabilitation programs following an AMI despite encouragement to attend. It may be unrealistic to aim for 100% referral and uptake into cardiac rehabilitation programs and therefore an inappropriate endpoint by which to evaluate such programs.