Interaction between physical activity and continuous-flow left ventricular assist device function in outpatients

Standardised Exercise Prescription for Patients with Chronic Coronary Syndrome and/or Heart Failure: A Consensus Statement from the EXPERT Working Group

Whereas exercise training, as part of multidisciplinary rehabilitation, is a key component in the management of patients with chronic coronary syndrome (CCS) and/or congestive heart failure (CHF), physicians and exercise professionals disagree among themselves on the type and characteristics of the exercise to be prescribed to these patients, and the exercise prescriptions are not consistent with the international guidelines. This impacts the efficacy and quality of the intervention of rehabilitation. To overcome these barriers, a digital training and decision support system [i.e. EXercise Prescription in Everyday practice & Rehabilitative Training (EXPERT) tool], i.e. a stepwise aid to exercise prescription in patients with CCS and/or CHF, affected by concomitant risk factors and comorbidities, in the setting of multidisciplinary rehabilitation, was developed. The EXPERT working group members reviewed the literature and formulated exercise recommendations (exercise training intensity, frequency, volume, type, session and programme duration) and safety precautions for CCS and/or CHF (including heart transplantation). Also, highly prevalent comorbidities (e.g. peripheral arterial disease) or cardiac devices (e.g. pacemaker, implanted cardioverter defibrillator, left-ventricular assist device) were considered, as well as indications for the in-hospital phase (e.g. after coronary revascularisation or hospitalisation for CHF). The contributions of physical fitness, medications and adverse events during exercise testing were also considered. The EXPERT tool was developed on the basis of this evidence. In this paper, the exercise prescriptions for patients with CCS and/or CHF formulated for the EXPERT tool are presented. Finally, to demonstrate how the EXPERT tool proposes exercise prescriptions in patients with CCS and/or CHF with different combinations of CVD risk factors, three patient cases with solutions are presented.

Validation of Intrinsic Left Ventricular Assist Device Data Tracking Algorithm for Early Recognition of Centrifugal Flow Pump Thrombosis

Advanced stage heart failure patients can benefit from the unloading effects of an implantable left ventricular assist device. Despite best clinical practice, LVADs are associated with adverse events, such as pump thrombosis (PT). An adaptive algorithm alerting when an individual’s appropriate levels in pump power uptake are exceeded, such as in the case of PT, can improve therapy of patients implanted with a centrifugal LVAD. We retrospectively studied 75 patients implanted with a centrifugal LVAD in a single center. A previously optimized adaptive pump power-tracking algorithm was compared to clinical best practice and clinically available constant threshold algorithms. Algorithm performances were analyzed in a PT group (n = 16 patients with 30 PT events) and a thoroughly selected control group (n = 59 patients, 34.7 patient years of LVAD data). Comparison of the adaptive power-tracking algorithm with the best performing constant threshold algorithm resulted in sensitivity of 83.3% vs. 86.7% and specificity of 98.9% vs. 95.3%, respectively. The power-tracking algorithm produced one false positive detection every 11.6 patient years and early warnings with a median of 3.6 days prior to PT diagnosis. In conclusion, a retrospective single-center validation study with real-world patient data demonstrated advantageous application of a power-tracking algorithm into LVAD systems and clinical practice.

Peripartum cardiomyopathy: a global effort to find the cause and cure for the rare and little understood disease

In this review, we present our current understanding of peripartum cardiomyopathy (PPCM) based on reports of the incidence, diagnosis and current treatment options. We summarise opinions on whether PPCM is triggered by vascular and/or hormonal causes and examine the influence of comorbidities such as preeclampsia. Two articles published in 2021 strongly support the hypothesis that PPCM may be a familial disease. Using large cohorts of PPCM patients, they summarised the available genomic DNA sequence data that are expressed in human cardiomyocytes. While PPCM is considered a disease predominately affecting the left ventricle, there are data to suggest that some cases also involve right ventricular failure. Finally, we conclude that there is sufficient evidence to warrant an RNAseq investigation and that this would be most informative if performed at the cardiomyocytes level rather than analysing genomic DNA from the peripheral circulation. Given the rarity of PPCM, the combined resources of international human heart tissue biobanks have assembled 30 ventricular tissue samples from PPCM patients, and we are actively seeking to enlarge this patient base by collaborating with human heart tissue banks and research laboratories who would like to join this endeavour.

Patient-Reported Issues Following Left Ventricular Assist Device Implantation Hospitalization

The purpose of this study was to explore the information reported by patients via a smartphone application (VAD Care App) used for left ventricular assist device (LVAD) self-care monitoring and reporting post hospital discharge. Specific aims were to examine the type and frequency of issues reported by patients through the app during months 1, 3, and 6 postdischarge. An exploratory-descriptive research design was used with 17 patients (12 males and 5 females) with durable LVADs, mean age of 48.6 ± 16 years. Data generated by the patients' daily smartphone app usage more than 6 months were extracted from the server. Data were coded and clustered according to issues reported by patients via the app and analyzed with descriptive statistics. Three clusters of issues were found: physiologic, behavioral (self-care), and signs and symptoms. LVAD flows and pulsatility indices, hypertension, driveline care, and heart failure symptoms were worse at month 1, and then appeared to improve at months 3-6. However, abnormal levels of the international normalization ratio were common at all assessment points. Further research is needed to understand the mechanism of the reported issues on treatment outcomes, then develop and test interventions to inform evidence-based practice and clinical guidelines for smartphone apps used in LVAD self-care monitoring.

Reviewing the clinical utility of ventricular assist device log files

Background

Ventricular assist devices (VADs) have provided a temporising solution to many individuals with refractory heart failure (HF) while awaiting a suitable donor for heart transplantation which remains the gold standard in treatment. Many of the discussions around VADs involve ongoing morbidity; however, one aspect of VADs that is often overlooked is the utility of their log files. We decided to review the literature for mentions of the clinical utility of VAD log files.

Methods

A keyword search was utilised on PUBMED using the terms 'Ventricular Assist Device' and 'Log files'. Perhaps unsurprisingly, this search only yielded 4 results with further articles being discovered through the bibliography of these publications.

Results

The 4 identified articles provided basic information on log files, particularly with reference to the HVAD. Logs can be categorised into three types-data (pump parameters), events (changes in parameters) and alarms (abnormal function). Using a combination of these logs, we can readily identify abnormal pump operation such as the development and progression of pump thrombosis, suction events and gastrointestinal bleeding. However, the research potential of log files was not discussed in these publications, particularly as it pertains to areas such as studying speed modulation and pulsatility in VADs.

Conclusions

VADs are an important staple in the treatment of patients with refractory HF. Log files provide a treasure-trove of information and knowledge that can be utilised for clinical benefit. Furthermore, log files provide an excellent tool for conducting research into device functionality. Current literature on the clinical utility of log files is sparse with much untapped potential.

Physical Activity Is Higher in Patients with Left Ventricular Assist Device Compared with Chronic Heart Failure

PURPOSE

Left ventricular assist devices (LVAD) are associated with an increased aerobic capacity in patients with chronic heart failure (CHF). However, studies evaluating the impact of LVAD implantation on physical activity (PA) are lacking. The aim of this study was to compare daily PA levels in participants with LVAD with well-matched CHF participants.

METHODS

Sixteen participants with an LVAD (age, 59.1 ± 10.8 yr) were case-matched to 16 participants with advanced CHF (age, 58.3 ± 8.7 yr), who were listed or being considered for cardiac transplantation. Participants underwent a cardiopulmonary exercise test to determine peak oxygen consumption (V˙O2 peak). Physical activity was monitored continuously for seven consecutive days with an Actiheart monitor.

RESULTS

V˙O2 peak in the CHF group (12.3 ± 3.5 mL·kg·min) was not significantly different to the LVAD group before LVAD implantation (10.4 ± 2.1 mL·kg·min), but was lower than in the LVAD group after implantation (15.8 ± 4.3 mL·kg·min; P < 0.05). Physical activity was higher in the LVAD (19.7 ± 6.4 kJ·kg·d) compared with the CHF group (11.6 ± 6.9 kJ·kg·d; P = 0.001). The LVAD participants spent more time performing moderate-intensity PA than their CHF counterparts (median, 26 min·d; interquartile range, 24-40 min·d vs median, 12 min·d; interquartile range, 9-16 min·d; P < 0.001). Physical activity was correlated with V˙O2 peak (r = 0.582; P = 0.001) across participants in the CHF and LVAD groups.

CONCLUSIONS

Higher levels of PA were observed in participants with LVAD compared with patients with advanced CHF. This may be due to a higher V˙O2 peak, resulting in an improved capacity to perform activities of daily living with less symptoms.

Restoring pulsatility and peakVO2 in the era of continuous flow, fixed pump speed, left ventricular assist devices: 'A hypothesis of pump's or patient's speed?'

Despite significant improvement in survival and functional capacity after continuous flow left ventricular assist device implantation, the patient's quality of life may remain limited by complications such as aortic valve insufficiency, thromboembolic episodes and gastrointestinal bleeding attributed to high shear stress continuous flow with attenuated or absence of pulsatile flow and by a reduced peak oxygen consumption (peakVO₂) primarily associated with a fixed pump speed operation. Revision of current evidence suggests that high technology pump speed algorithms, a 'hypothesis of decreasing pump's speed' to promote pulsatile flow and a 'hypothesis of increasing pump's speed' to increase peakVO₂, may only partially reverse these barriers. A 'hypothesis of increasing patient's speed' is introduced, suggesting that exercise training may further contribute to the patient's recovery, enhancing peakVO₂ and pulsatile flow by improving skeletal muscle oxidative capacity and strength, peripheral vasodilatory and ventilatory responses, favour changes in preload/afterload and facilitate native flow, formulating the rationale for further studies in the field.

Impact of Pump Speed on Hemodynamics With Exercise in Continuous Flow Ventricular Assist Device Patients

At fixed speed, the spontaneous increase in pump flow accompanying exercise in patients with continuous flow left ventricular assist devices (cfLVADs) is slight in comparison to normal physiologic response, limiting exercise capacity. We systematically exercised 14 patients implanted with an isolated HeartWare HVAD undergoing routine right heart catheterization at baseline and at maximal safe pump speed. In addition to hemodynamics, mixed venous oxygen saturation (SvO2), echocardiography and noninvasive mean arterial pressure, and heart rate were measured. Significantly greater pump flows were achieved with maximum pump speed compared with baseline speed at rest (mean ± standard deviation [SD]: 5.0 ± 0.7 vs. 4.6 ± 0.8 L/min) and peak exercise (6.7 ± 1.0 vs. 5.9 ± 0.9 L/min, p = 0.001). Pulmonary capillary wedge pressure was significantly reduced with maximum pump speed compared to baseline pump speed at rest (10 ± 4 vs. 15 ± 5 mmHg, p < 0.001) and peak exercise (27 ± 8 vs. 30 ± 8 mmHg, p = 0.002). Mixed venous oxygen saturation decreased with exercise (p < 0.001) but was unaffected by changes in pump speed. In summary, although higher pump speeds synergistically augment the increase in pump flow associated with exercise and blunt the exercise-induced rise in left heart filling pressures, elevated filling pressures and markedly diminished SvO2 persist at maximal safe pump speed, suggesting that physiologic flow increases are not met by isolated cfLVADs in the supported failing heart.

Exercise gas exchange in continuous-flow left ventricular assist device recipients

Exercise ventilation/perfusion matching in continuous-flow left ventricular assist device recipients (LVAD) has not been studied systematically. Twenty-five LVAD and two groups of 15 reduced ejection fraction chronic heart failure (HFrEF) patients with peak VO₂ matched to that of LVAD (HFrEF-matched) and ≥14 ml/kg/min (HFrEF≥14), respectively, underwent cardiopulmonary exercise testing with arterial blood gas analysis, echocardiogram and venous blood sampling for renal function evaluation. Arterial-end-tidal PCO₂ difference (P(a-ET)CO₂) and physiological dead space-tidal volume ratio (VD/VT) were used as descriptors of alveolar and total wasted ventilation, respectively. Tricuspid annular plane systolic excursion/pulmonary artery systolic pressure ratio (TAPSE/PASP) and blood urea nitrogen/creatinine ratio were calculated in all patients and used as surrogates of right ventriculo-arterial coupling and circulating effective volume, respectively. LVAD and HFrEF-matched showed no rest-to-peak change of P(a-ET)CO₂ (4.5±2.4 vs. 4.3±2.2 mm Hg and 4.1±1.4 vs. 3.8±2.5 mm Hg, respectively, both p >0.40), whereas a decrease was observed in HFrEF≥14 (6.5±3.6 vs. 2.8±2.0 mm Hg, p <0.0001). Rest-to-peak changes of P(a-ET)CO₂ correlated to those of VD/VT (r = 0.70, p <0.0001). Multiple regression indicated TAPSE/PASP and blood urea nitrogen/creatinine ratio as independent predictors of peak P(a-ET)CO₂. LVAD exercise gas exchange is characterized by alveolar wasted ventilation, i.e. hypoperfusion of ventilated alveoli, similar to that of advanced HFrEF patients and related to surrogates of right ventriculo-arterial coupling and circulating effective volume.

Exercise physiology in chronic mechanical circulatory support patients: vascular function and beyond

PURPOSE OF REVIEW

The majority of patients currently implanted with left ventricular assist devices have the expectation of support for more than 2 years. As a result, survival alone is no longer a sufficient distinctive for this technology, and there have been many studies within the last few years examining functional capacity and exercise outcomes.

RECENT FINDINGS

Despite strong evidence for functional class improvements and increases in simple measures of walking distance, there remains incomplete normalization of exercise capacity, even in the presence of markedly improved resting hemodynamics. Reasons for this remain unclear. Despite current pumps being run at a fixed speed, it is widely recognized that pump outputs significantly increase with exercise. The mechanism of this increase involves the interaction between preload, afterload, and the intrinsic pump function curves. The role of the residual heart function is also important in determining total cardiac output, as well as whether the aortic valve opens with exercise. Interactions with the vasculature, with skeletal muscle blood flow and the state of the autonomic nervous system are also likely to be important contributors to exercise performance.

SUMMARY

Further studies examining optimization of pump function with active pump speed modulation and options for optimization of the overall patient condition are likely to be needed to allow left ventricular assist devices to be used with the hope of full functional physiological recovery.

Left ventricular assist device-induced reverse remodeling: it's not just about myocardial recovery

INTRODUCTION

The abnormal structure, function and molecular makeup of dilated cardiomyopathic hearts can be partially normalized in patients supported by a left ventricular assist device (LVAD), a process called reverse remodeling. This leads to recovery of function in many patients, though the rate of full recovery is low and in many cases is temporary, leading to the concept of heart failure remission, rather than recovery. Areas covered: We summarize data indicative of ventricular reverse remodeling, recovery and remission during LVAD support. These terms were used in searches performed in Pubmed. Duplication of topics covered in depth in prior review articles were avoided. Expert commentary: Although most patients undergoing mechanical circulatory support (MCS) show a significant degree of reverse remodeling, very few exhibit sufficiently improved function to justify device explantation, and many from whom LVADs have been explanted have relapsed back to the original heart failure phenotype. Future research has the potential to clarify the ideal combination of pharmacological, cell, gene, and mechanical therapies that would maximize recovery of function which has the potential to improve exercise tolerance of patients while on support, and to achieve a higher degree of myocardial recovery that is more likely to persist after device removal.

Circadian variation of motor current observed in fixed rotation speed continuous-flow left ventricular assist device support

The algorithm for the physiological control provided by left ventricular assist devices (LVADs) has been controversial. In particular, little is known about the physiological control algorithm (such as for achieving physiological circadian rhythms) in continuous-flow LVADs. To investigate the existence of circadian variation, we retrospectively evaluated the LVAD flow-correlated motor current of patients supported by continuous-flow LVADs. The motor current and the pump speed were collected from the external controller every 10 min after device implantation, and the data were divided for every 30-day period, which began on midnight on the first post-operative day. The subjects were 18 patients (mean age 37.7, mean body surface area 1.71 m(2) at the time of operation) with dilated cardiomyopathy or dilated phase of hypertrophic cardiomyopathy. As of August 1, 2013, the patients' median support duration was 889 days. The mean calculated dominant period of motor current variation was 24.0 h and the mean amplitude was 11.7 mA for the entire duration. The amplitude of the motor current circadian variation tended to be increased until around the fifth month. The motor current had a tendency to be relatively low during the night time and high during the day time. A significant difference was found between the night-time and day-time mean motor current for the entire duration (p < 0.05). In conclusion, the circadian variation of the motor current could be observed over long term in patients with fixed rotation speed continuous-flow LVAD support.

Cataract surgery in patients with left ventricular assist device support

Left ventricular assist devices (LVADs) have been increasingly used for 20 years in terminally ill patients with advanced heart failure or awaiting cardiac transplantation. Despite improvement in morbidity and mortality from use of these devices, quality of life may be limited by cataract. Access to cataract surgery in this predominantly elderly population is essential but limited by unfamiliarity with these devices. We describe phacoemulsification and intraocular lens implantation in 2 patients with LVADs. The patients had extensive preoperative cardiology evaluations and were instructed to continue warfarin through the day of surgery. Monitored sedation was used with fentanyl and midazolam. Both patients experienced significant improvement in visual acuity and quality of life. Neither experienced intraoperative hemodynamic instability. Cataract surgery may be safely performed in patients with LVAD support when adequate monitoring resources are available.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.