Impairments in Blood Pressure Regulation and Cardiac Baroreceptor Sensitivity Among Patients With Heart Failure Supported With Continuous-Flow Left Ventricular Assist Devices

Practical Guidance for Hemodynamic Assessment by Right Heart Catheterization in Management of Heart Failure

Heart failure is a clinical syndrome characterized by the inability of the heart to meet the circulatory demands of the body without requiring an increase in intracardiac pressures at rest or with exertion. Hemodynamic parameters can be measured via right heart catheterization, which has an integral role in the full spectrum of heart failure: from ambulatory patients to those in cardiogenic shock, as well as patients being considered for left ventricular device therapy and heart transplantation. Hemodynamic data are critical for prompt recognition of clinical deterioration, assessment of prognosis, and guidance of treatment decisions. This review is a field guide for hemodynamic assessment, troubleshooting, and interpretation for clinicians treating patients with heart failure.

Cardiopulmonary Performance Among Heart Failure Patients Before and After Left Ventricular Assist Device Implantation

BACKGROUND

Patients with heart failure with reduced ejection fraction (HFrEF) have persistent impairments in functional capacity after continuous-flow left ventricular assist device (CF-LVAD) implantation.

OBJECTIVES

This study aims to characterize longitudinal changes in exercise hemodynamics and functional capacity among patients with HFrEF before and after CF-LVAD implantation.

METHODS

Ten patients underwent 3 invasive cardiopulmonary exercise tests on upright cycle ergometry with pulmonary artery catheterization: 1) Visit 1 before CF-LVAD implantation; 2) Visit 2 after device implantation with CF-LVAD pump speed held constant at baseline speed; and 3) Visit 3 with increases in pump speed during exercise (median: 1,050 rpm [IQR: 750-1,150 rpm] and 220 rpm [IQR: 120-220 rpm] for HeartMate 3 and HeartWare VAD, respectively). Hemodynamics and direct Fick cardiac output were monitored using pulmonary artery catheterization. Gas exchange metrics were determined using indirect calorimetry.

RESULTS

Maximal oxygen uptake (Visits 1, 2, and 3: 10.8 ± 2.5 mL/kg/min, 10.7 ± 2.2 mL/kg/min, and 11.5 ± 1.7 mL/kg/min; P = 0.92) did not improve after device implantation. Mean pulmonary arterial and pulmonary capillary wedge pressures increased significantly during submaximal and peak exercise on preimplantation testing (P < 0.01 for rest vs peak exercise) and remained elevated, with minimal change on Visits 2 and 3 regardless of whether pump speed was fixed or increased.

CONCLUSIONS

Among patients with HFrEF, cardiovascular hemodynamics and exercise capacity were similar after CF-LVAD implantation, regardless of whether patients exercised at fixed or adjusted pump speeds during exercise. Further research is needed to determine methods by which LVADs may alleviate the HFrEF syndrome after device implantation. (Effect of mechanIcal circulatoRy support ON exercise capacity aMong pAtieNts with heart failure [IRONMAN]; NCT03078972).

Characteristics and Treatment of Exercise Intolerance in Patients With Long COVID

The post-acute sequalae of SARS-CoV-2, also known as "Long COVID," is characterized by profound fatigue, impaired functional capacity with post-exertional malaise, orthostatic intolerance, and tachycardia. At least 25-30% of individuals impacted by SARS-CoV-2 will go on to experience the Long COVID syndrome, underscoring the detrimental impact this condition has on society. Although efforts are underway to further understand risk factors for Long COVID and identify strategies to prevent disease development entirely, implementation of treatment strategies is warranted to alleviate symptom burden among those affected. This review provides a rationale for exercise prescriptions tailored to the Long COVID patient based on the pathophysiology underlying this syndrome, as well as the previously demonstrated benefits of exercise training in other similar populations whose clinical manifestations result from cardiac deconditioning. Herein, we discuss methods to tailor exercise protocols, accommodating exercise intolerance and post-exertional malaise that may otherwise limit the ability to participate in a training protocol, as well as data demonstrating that a focused exercise prescription may effectively alleviate symptom burden in these patients. Long COVID results, in large part, from deconditioning, which may result from as little as 20 hr of inactivity. Exercise prescriptions tailored to patients with Long COVID may effectively alleviate symptom burden associated with this condition and in the absence of overt contraindications should be considered in management.

Exertional Cardiac and Pulmonary Vascular Hemodynamics in Patients With Heart Failure With Reduced Ejection Fraction

BACKGROUND

Exertional dyspnea is a cardinal manifestation of heart failure with reduced ejection fraction (HFrEF), but quantitative data regarding exertional hemodynamics are lacking.

OBJECTIVES

We sought to characterize exertional cardiopulmonary hemodynamics in patients with HFrEF.

METHODS

We studied 35 patients with HFrEF (59 ± 12 years old, 30 males) who completed invasive cardiopulmonary exercise testing. Data were collected at rest, at submaximal exercise and at peak effort on upright cycle ergometry. Cardiovascular and pulmonary vascular hemodynamics were recorded. Fick cardiac output (Qc) was determined. Hemodynamic predictors of peak oxygen uptake (VO2) were identified.

RESULTS

Left ventricular ejection fraction and cardiac index were 23% ± 8% and 2.9 ± 1.1 L/min/m2, respectively. Peak VO2 was 11.8 ± 3.3 mL/kg/min, and the ventilatory efficiency slope was 53 ± 13. Right atrial pressure increased from rest to peak exercise (4 ± 5 vs 7 ± 6 mmHg,). Mean pulmonary arterial pressure increased from rest to peak exercise (27 ± 13 vs 38 ± 14 mmHg). Pulmonary artery pulsatility index increased from rest to peak exercise, while pulmonary arterial capacitance and pulmonary vascular resistance declined.

CONCLUSIONS

Patients with HFrEF suffer from marked increases in filling pressures during exercise. These findings provide new insight into cardiopulmonary abnormalities contributing to impairments in exercise capacity in this population.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT03078972.

Increased Dead Space Ventilation as a Contributing Factor to Persistent Exercise Limitation in Patients with a Left Ventricular Assist Device

(1) Background: The exercise capacity of patients with a left ventricular assist device (LVAD) remains limited despite mechanical support. Higher dead space ventilation (VD/VT) may be a surrogate for right ventricular to pulmonary artery uncoupling (RV-PA) during cardiopulmonary exercise testing (CPET) to explain persistent exercise limitations. (2) Methods: We investigated 197 patients with heart failure and reduced ejection fraction with (n = 89) and without (HFrEF, n = 108) LVAD. As a primary outcome NTproBNP, CPET, and echocardiographic variables were analyzed for their potential to discriminate between HFrEF and LVAD. As a secondary outcome CPET variables were evaluated for a composite of hospitalization due to worsening heart failure and overall mortality over 22 months. (3) Results: NTproBNP (OR 0.6315, 0.5037-0.7647) and RV function (OR 0.45, 0.34-0.56) discriminated between LVAD and HFrEF. The rise of endtidal CO2 (OR 4.25, 1.31-15.81) and VD/VT (OR 1.23, 1.10-1.40) were higher in LVAD patients. Group (OR 2.01, 1.07-3.85), VE/VCO2 (OR 1.04, 1.00-1.08), and ventilatory power (OR 0.74, 0.55-0.98) were best associated with rehospitalization and mortality. (4) Conclusions: LVAD patients displayed higher VD/VT compared to HFrEF. Higher VD/VT as a surrogate for RV-PA uncoupling could be another marker of persistent exercise limitations in LVAD patients.

Neurologic Complications in Patients With Left Ventricular Assist Devices

Left ventricular assist device (LVAD) use has revolutionised the care of patients with advanced heart failure, allowing more patients to survive until heart transplantation and providing improved quality for patients unable to undergo transplantation. Despite these benefits, improvements in device technology, and better clinical care and experience, LVADs are associated with neurologic complications. This review provides information on the incidence, risk factors, and management of neurologic complications among LVAD patients. Although scant guidelines exist for the evaluation and management of neurologic complications in LVAD patients, a high index of suspicion can prompt early detection of neurologic complications which may improve overall neurologic outcomes. A better understanding of the implications of continuous circulatory flow on systemic and cerebral vasculature is necessary to reduce the common occurrence of neurologic complications in this population.

The molecular makeup of peripheral and central baroreceptors: stretching a role for Transient Receptor Potential (TRP), Epithelial Sodium Channel (ENaC), Acid Sensing Ion Channel (ASIC), and Piezo channels

The autonomic nervous system maintains homeostasis of cardiovascular, respiratory, gastrointestinal, urinary, immune, and thermoregulatory function. Homeostasis involves a variety of feedback mechanisms involving peripheral afferents, many of which contain molecular receptors sensitive to mechanical deformation, termed mechanosensors. Here, we focus on the molecular identity of mechanosensors involved in the baroreflex control of the cardiovascular system. Located within the walls of the aortic arch and carotid sinuses, and/or astrocytes in the brain, these mechanosensors are essential for the rapid moment-to-moment feedback regulation of blood pressure (BP). Growing evidence suggests that these mechanosensors form a co-existing system of peripheral and central baroreflexes. Despite the importance of these molecules in cardiovascular disease and decades of research, their precise molecular identity remains elusive. The uncertainty surrounding the identity of these mechanosensors presents a major challenge in understanding basic baroreceptor function and has hindered the development of novel therapeutic targets for conditions with known arterial baroreflex impairments. Therefore, the purpose of this review is to (i) provide a brief overview of arterial and central baroreflex control of BP, (ii) review classes of ion channels currently proposed as the baroreflex mechanosensor, namely Transient Receptor Potential (TRP), Epithelial Sodium Channel (ENaC), Acid Sensing Ion Channel (ASIC), and Piezo, along with additional molecular candidates that serve mechanotransduction in other organ systems, and (iii) summarize the potential clinical implications of impaired baroreceptor function in the pathophysiology of cardiovascular disease.

Impact of Mechanical Circulatory Support on Exercise Capacity in Patients With Advanced Heart Failure

Approximately 6 million individuals have heart failure in the United States alone and 15 million in Europe. Left ventricular assist devices (LVAD) improve survival in these patients, but functional capacity may not fully improve. This article examines the hypothesis that patients supported by LVAD experience persistent reductions in functional capacity and explores mechanisms accounting for abnormalities in exercise tolerance.

Management of Hypertension in Patients With Ventricular Assist Devices: A Scientific Statement From the American Heart Association

Mechanical circulatory support with durable continuous-flow ventricular assist devices has become an important therapeutic management strategy for patients with advanced heart failure. As more patients have received these devices and the duration of support per patient has increased, the postimplantation complications have become more apparent, and the need for approaches to manage these complications has become more compelling. Continuous-flow ventricular assist devices, including axial-flow and centrifugal-flow pumps, are the most commonly used mechanical circulatory support devices. Continuous-flow ventricular assist devices and the native heart have a constant physiological interplay dependent on pump speed that affects pressure-flow relationships and patient hemodynamics. A major postimplantation complication is cerebrovascular vascular accidents. The causes of cerebrovascular vascular accidents in ventricular assist device recipients may be related to hypertension, thromboembolic events, bleeding from anticoagulation, or some combination of these. The most readily identifiable and preventable cause is hypertension. Hypertension management in these patients has been hampered by the fact that it is difficult to accurately measure blood pressure because these ventricular assist devices have continuous flow and are often not pulsatile. Mean arterial pressures have to be identified by Doppler or oscillometric cuff and treated. Although guidelines for hypertension management after ventricular assist device implantation are based largely on expert consensus and conventional wisdom, the mainstay of treatment for hypertension includes guideline-directed medical therapy for heart failure with reduced ejection fraction because this may reduce adverse effects associated with hypertension and increase the likelihood of favorable ventricular remodeling. The use of systemic anticoagulation in ventricular assist device recipients may at a given blood pressure increase the risk of stroke.

Echo-guided left ventricular assist device speed optimisation for exercise maximisation

Objective

Current generation left ventricular assist devices (LVADs) operate with a fixed rotation speed and no automated speed adjustment function. This study evaluates the concept of physiological pump speed optimisation based on aortic valve opening (AVO) imaging during a cardiopulmonary exercise test (CPET).

Methods

This prospective crossover study (NCT05063006) enrolled patients with implanted third-generation LVADs with hydrodynamic bearing. After resting speed optimisation, patients were randomised to a fixed-modified speed or modified-fixed speed CPET sequence. Fixed speed CPET maintained baseline pump settings. During the modified speed CPET, the LVAD speed was continuously altered to preserve periodic AVO.

Results

We included 22 patients, the mean age was 58.4±7 years, 4.5% were women and 54.5% had ischaemic cardiomyopathy. Exertional AVO assessment was feasible in all subjects. Maintaining periodic AVO allowed to safely raise the pump speed from 2900 (IQR 2640–3000) to 3440 revolutions per minute (RPM) (IQR 3100–3700; p<0.001). As a result, peak oxygen consumption increased from 11.1±2.4 to 12.8±2.8 mL/kg/min (p<0.001) and maximum workload from 1.1 (IQR 0.9–1.5) to 1.2 W/kg (IQR 0.9–1.7; p=0.028). The Borg scale exertion level decreased from 15.2±1.5 to 13.5±1.2 (p=0.005).

Conclusions

Transthoracic AVO imaging is possible during CPETs in patients with LVAD. Dynamic echo-guided pump speed adjustment based on the AVO improves exercise tolerance and augments peak oxygen consumption and maximum workload.

Biomarkers in Patients with Left Ventricular Assist Device: An Insight on Current Evidence

Left ventricular assist devices (LVADs) have been representing a cornerstone therapy for patients with end-stage heart failure during the last decades. However, their use induces several pathophysiological modifications which are partially responsible for the complications that typically characterize these patients, such as right ventricular failure, thromboembolic events, as well as bleedings. During the last years, biomarkers involved in the pathways of neurohormonal activation, myocardial injury, adverse remodeling, oxidative stress and systemic inflammation have raised attention. The search and analysis of potential biomarkers in LVAD patients could lead to the identification of a subset of patients with an increased risk of developing these adverse events. This could then promote a closer follow-up as well as therapeutic modifications. Furthermore, it might highlight some new therapeutic pharmacological targets that could lead to improved long-term survival. The aim of this review is to provide current evidence on the role of different biomarkers in patients with LVAD, in particular highlighting their possible implications in clinical practice.