Exercise performance of chronic heart failure patients in the early period of support by an axial-flow left ventricular assist device as destination therapy

Exercise Performance and Quality of Life of Left Ventricular Assist Device Patients After Long-Term Outpatient Cardiac Rehabilitation

PURPOSE

Exercise performance and quality of life (QoL) of left ventricular assist device (LVAD) patients improve after early cardiac rehabilitation (CR). The purpose of this study was to examine the efficacy of multiprofessional long term phase 3 outpatient CR, and whether cardiopulmonary exercise testing (CPX) and 6-min walk testing (6MWT) post-LVAD implantation predict hospital readmission.

METHODS

This retrospective observational cohort study included 29 LVAD patients (58.6 ± 7.7 yr, female: 13.8%, body mass index: 29.4 ± 3.3 kg/m 2 ). Functional performance tests (CPX, 6MWT, sit-to-stand test), QoL, and psychological surveys (Kansas City Cardiomyopathy Questionnaire, hospital anxiety and depression scale, and Control Convictions about Disease and Health [KKG]) were performed at baseline and at the end of CR.

RESULTS

The CR was initiated at a median (IQR) of 159 (130-260) d after LVAD implantation for a duration of 340 (180-363) d with 46.8 ± 23.2 trainings. The 6MWT (408.4 ± 113.3 vs 455.4 ± 115.5 m, P = .003) and sit-to-stand test (16.7 ± 6.9 vs 19.0 ± 5.3 repetitions, P = .033) improved, but relative peak oxygen uptake (V˙ o2peak : 9.4 [8.2-14.4] vs 9.3 [7.8-13.4] mL/min/kg, P = .57) did not change. Using receiver operating characteristic curve analysis, baseline V˙ o2peak values were associated with readmission 1-yr after CR onset (C-statistic = 0.88) with a cutoff value of V˙ o2peak < 9.15 mL/min/kg (100% sensitivity, 78% specificity, P < .001). The Kansas City Cardiomyopathy Questionnaire self-efficacy and knowledge (+6.3 points), QoL (+5.0 points), and social limitation (+7.1 points) demonstrated clinically important changes. In addition, the hospital anxiety and depression scale showed a significant reduction in anxiety (4.6 ± 3.2 vs 2.6 ± 2.4, P = .03).

CONCLUSIONS

Long-term CR is safe and LVAD outpatients showed improvement of QoL, anxiety, and submaximal exercise performance. In addition, V˙ o2peak and 6MWT have prognostic value for readmission.

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.

Exercise oscillatory ventilation in patients with advanced heart failure with and without left ventricular assist device

BACKGROUND

Exercise oscillatory ventilation (EOV), indicating pathological fluctuations on pulmonary arterial pressure, is associated with mortality in patients with heart failure (HF). Whether left ventricular assist device (LVAD)-induced ventricular unloading can reverse EOV and may prevent short-term rehospitalization has not been investigated.

METHODS

We performed a retrospective single-center in- and outpatient analysis of patients with (n = 20, LVAD) and without (n = 27, HF) circulatory support and reduced ejection fraction (EF, 22.8 ± 7.9%). The association of cardiopulmonary exercise testing (CPET) variables and 3 months-rehospitalization (3MR) as a primary outcome was analyzed. Furthermore, CPET variables were compared regarding the presence of EOV (+/-).

RESULTS

Lower VO_2peak (11.6 ± 4.9 ml/kg/min vs. 14.4 ± 4.3 ml/kg/min, p = 0.039), lower increase of PETCO₂ (CI = 0.049-1.127; p = 0.068), and higher VE/VCO₂ (43.8 ± 9.5 vs. 38.3 ± 10.6; p = 0.069) were associated with 3MR. Flattening of O₂ pulse (CI = 0.139-2.379; p = 0.487) had no impact on 3MR. EOV was present in 59.5% (n = 28/47) of patients, without a significant difference between LVAD and HF patients (p = 0.959). Patients with HF/EOV+ demonstrated significantly lower VO_2peak compared with HF/EOV- (p = 0.039). LVAD/EOV+ displayed significantly lower EF (p = 0.004) and fewer aortic valve opening than LVAD/EOV- (p = 0.027).

CONCLUSIONS

Lower VO_2peak , but not EOV, was associated with 3MR. EOV occurred at a similar rate in LVAD and HF patients, which may illustrate insufficient unloading during exercise in chronic LVAD therapy and may contribute to the limited exercise capacity following LVAD implantation. Simultaneous CPET and right heart catheterization studies are needed to elucidate whether EOV may serve as a non-invasive predictor of insufficient LV unloading necessitating LVAD reprograming.

Long-term preservation of functional capacity and quality of life in advanced heart failure patients with bridge to transplant therapy: A report from Japanese nationwide multicenter registry

BACKGROUND

Under the revised heart allocation system in the United States, bridge to transplant (BTT) patients with left ventricular assist device (LVAD) have a longer waitlist period, as they are now lowly prioritized. However, little is known regarding the long-term trajectory of functional capacity (FC) and health-related quality of life (HR-QOL) among BTT-LVAD patients.

METHODS

We retrospectively analyzed 442 consecutive patients with BTT-LVAD between April 2013 and May 2019 from a Japanese nationwide registry. FC (New York Heart Association [NYHA] functional class, peak oxygen uptake [VO₂], and 6-min walk test [6MWT]) and HR-QOL (European Quality of Life [EQ-5D index] and Visual Analogue Scale [EQ-VAS]) were assessed at baseline and for up to 60 months after LVAD implantation.

RESULTS

During the follow-up period of 30 months (IQR 18-42 months), 100 (22.6%) patients underwent transplantation, 37 (8.3%) died, and 14 (3.1%) underwent explantation for recovery. Mean peak VO₂, 6MWT distance, EQ-5D index, and EQ-VAS significantly improved 3 months after LVAD implantation (p = 0.0012, p = 0.0037, p < 0.001, p < 0.001, respectively). Furthermore, these improvements were sustained for up to 60 months following LVAD implantation. Major adverse events including device failure, infection, stroke, and bleeding, which occurred within the first 3 months after LVAD implantation may have not affected FC or HR-QOL for up to 60 months (p = 0.15, p = 0.22, respectively).

CONCLUSIONS

BTT patients showed long-term preservation of FC and HR-QOL, suggesting that BTT remains an option despite the long waiting time to HTx.

Physiology of Continuous-Flow Left Ventricular Assist Device Therapy

The expanding use of continuous-flow left ventricular assist devices (CF-LVADs) for end-stage heart failure warrants familiarity with the physiologic interaction of the device with the native circulation. Contemporary devices utilize predominantly centrifugal flow and, to a lesser extent, axial flow rotors that vary with respect to their intrinsic flow characteristics. Flow can be manipulated with adjustments to preload and afterload as in the native heart, and ascertainment of the predicted effects is provided by differential pressure-flow (H-Q) curves or loops. Valvular heart disease, especially aortic regurgitation, may significantly affect adequacy of mechanical support. In contrast, atrioventricular and ventriculoventricular timing is of less certain significance. Although beneficial effects of device therapy are typically seen due to enhanced distal perfusion, unloading of the left ventricle and atrium, and amelioration of secondary pulmonary hypertension, negative effects of CF-LVAD therapy on right ventricular filling and function, through right-sided loading and septal interaction, can make optimization challenging. Additionally, a lack of pulsatile energy provided by CF-LVAD therapy has physiologic consequences for end-organ function and may be responsible for a series of adverse effects. Rheological effects of intravascular pumps, especially shear stress exposure, result in platelet activation and hemolysis, which may result in both thrombotic and hemorrhagic consequences. Development of novel solutions for untoward device-circulatory interactions will facilitate hemodynamic support while mitigating adverse events. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.

Depressive symptoms interfere with the improvement in exercise capacity by cardiac rehabilitation after left ventricular assist device implantation

BACKGROUND

Although depressive symptoms are associated with an increased risk of readmission after left ventricular assist device (LVAD) implantation, it is unclear whether they affect the efficacy of exercise-based cardiac rehabilitation (EBCR). This study aimed to investigate the effect of depressive symptoms on EBCR efficacy.

METHODS

We analyzed 48 patients who participated in EBCR after LVAD implantation (mean age 45 ± 12 years; 60% male). Patients were classified into two groups using the Zung Self-Rating Depression Scale (SDS): depressive group (SDS ≥40, n = 27) and non-depressive group (SDS <40, n = 21). We examined changes in peak oxygen uptake (VO₂ ), knee extensor muscular strength (KEMS), and quality of life (QOL) during EBCR using analysis of covariance.

RESULTS

Although baseline characteristics were similar between the two groups, the non-depressive group was less likely to receive diuretics (22% vs. 52%, p = 0.030). Peak VO₂ , KEMS, and QOL significantly increased over time in both groups (all p < 0.05). The depressive group had a significantly lower change in peak VO₂ than the non-depressive group (2.7 vs. 1.6 ml/kg/min; mean difference: -1.1 ml/kg/min, 95% confidence interval [CI]: -0.045 to -2.17; p = 0.041, d = 0.59). There was no between-group difference regarding the change in KEMS or QOL. Adjusting for the baseline value, a significant difference between groups was observed only in peak VO₂ (p = 0.045).

CONCLUSIONS

Although EBCR significantly improved exercise capacity after LVAD implantation, depressive symptoms interfered with this improvement. Further studies are needed to determine whether psychological interventions for depression, in addition to EBCR, would improve the response to EBCR after LVAD implantation.

Proportional Assist Ventilation Improves Leg Muscle Reoxygenation After Exercise in Heart Failure With Reduced Ejection Fraction

Background

Respiratory muscle unloading through proportional assist ventilation (PAV) may enhance leg oxygen delivery, thereby speeding off-exercise oxygen uptake ( V . ⁢ O 2 ) kinetics in patients with heart failure with reduced left ventricular ejection fraction (HFrEF).

Methods

Ten male patients (HFrEF = 26 ± 9%, age 50 ± 13 years, and body mass index 25 ± 3 kg m²) underwent two constant work rate tests at 80% peak of maximal cardiopulmonary exercise test to tolerance under PAV and sham ventilation. Post-exercise kinetics of V . ⁢ O 2 , vastus lateralis deoxyhemoglobin ([deoxy-Hb + Mb]) by near-infrared spectroscopy, and cardiac output (Q _T ) by impedance cardiography were assessed.

Results

PAV prolonged exercise tolerance compared with sham (587 ± 390 s vs. 444 ± 296 s, respectively; p = 0.01). PAV significantly accelerated V . ⁢ O 2 recovery (τ = 56 ± 22 s vs. 77 ± 42 s; p < 0.05), being associated with a faster decline in Δ[deoxy-Hb + Mb] and Q _T compared with sham (τ = 31 ± 19 s vs. 42 ± 22 s and 39 ± 22 s vs. 78 ± 46 s, p < 0.05). Faster off-exercise decrease in Q _T with PAV was related to longer exercise duration (r = -0.76; p < 0.05).

Conclusion

PAV accelerates the recovery of central hemodynamics and muscle oxygenation in HFrEF. These beneficial effects might prove useful to improve the tolerance to repeated exercise during cardiac rehabilitation.

The left ventricular assist device as a patient monitoring system

Technological progress of left ventricular assist devices (LVADs) towards rotary blood pumps and the optimization of medical management contributed to the significant improvements in patient survival as well as LVAD support duration. Even though LVAD therapy is now well-established for end-stage heart failure patients, the long-term occurrence of adverse events (AE) such as bleeding, infection or stroke, still represent a relevant burden. An early detection of AE, before onset of major symptoms, can lead to further optimization of patient treatment and thus mitigate the burden of AE. Continuous patient monitoring facilitates identification of pathophysiological states and allows anticipation of AE to improve patient management. In this paper, methods, algorithms and possibilities for continuous patient monitoring based on LVAD data are reviewed. While experience with continuous LVAD monitoring is currently limited to a few centers worldwide, the pace of developments in this field is fast and we expect these technologies to have a global impact on the well-being of LVAD patients.

Left Ventricular Assist Device as Destination Therapy: a State of the Science and Art of Long-Term Mechanical Circulatory Support

PURPOSE OF REVIEW

The purpose of this review is to synthesize and summarize recent developments in the care of patients with end-stage heart failure being managed with a left ventricular assist device (LVAD) as destination therapy.

RECENT FINDINGS

Although the survival of patients treated with LVAD continues to improve, the rates of LVAD-associated complication, such as right ventricular failure, bleeding complications, and major infection, remain high, and management of these patients remains challenging. The durability and hemocompatibility of LVAD support have greatly increased in recent years as a result of new technologies and novel management strategies. Challenges remain in the comprehensive care of patients with destination therapy LVADs, including management of comorbidities and optimizing patient function and quality of life.

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.

Living Without a Pulse: The Vascular Implications of Continuous-Flow Left Ventricular Assist Devices

Pulsatility seems to have a teleological role because evolutionary hierarchy favors higher ordered animals with more complex, multichamber circulatory systems that generate higher pulse pressure compared with lower ordered animals. Yet despite years of such natural selection, the modern generation of continuous-flow left ventricular assist devices (CF-LVADs) that have been increasingly used for the last decade have created a unique physiology characterized by a nonpulsatile, nonlaminar blood flow profile with the absence of the usual large elastic artery Windkessel effect during diastole. Although outcomes and durability have improved with CF-LVADs, patients supported with CF-LVADs have a high rate of complications that were not as frequently observed with older pulsatile devices, including gastrointestinal bleeding from arteriovenous malformations, pump thrombosis, and stroke. Given the apparent fundamental biological role of the pulse, the purpose of this review is to describe the normal physiology of ventricular-arterial coupling from pulsatile flow, the effects of heart failure on this physiology and the vasculature, and to examine the effects of nonpulsatile blood flow on the vascular system and potential role in complications seen with CF-LVAD therapy. Understanding these concomitant vascular changes with CF-LVADs may be a key step in improving patient outcomes as modulation of pulsatility and flow characteristics may serve as a novel, yet simple, therapy for reducing complications.

Exercise Performance During the First Two Years After Left Ventricular Assist Device Implantation

Exercise performance of patients with left ventricular assist devices (LVADs) improves after postimplant cardiac rehabilitation (CR). Few studies assess the effectiveness of a CR and its long-term effect of exercise performance. For this purpose, we retrospectively analyzed data from LVAD patients, who underwent a stationary CR twice after pump implantation. Data from exercise training and cardiopulmonary exercise tests (CPETs) were analyzed. Fifteen patients (age: 57 ± 10 years, male 87%) were admitted to the rehabilitation clinic twice 39 ± 18 and 547 ± 197 days after LVAD implantation. An improvement from the beginning to the end of the second CR was observed in bicycle ergometer training (14.0 ± 8.8 vs. 35.7 ± 14.7 W; p < 0.001), in muscular strength (e.g., leg press: 41 ± 10 vs. 53 ± 14 kg; p < 0.001), and in 6 minute walk distance (421 ± 126 m vs. 480 ± 133 m; p = 0.040). Between the first and the second CR, improvement in all the training modules was observed as well as an increase in CPETs peak workload (56 ± 24 vs. 83 ± 26 W; p < 0.001) but not in peak oxygen consumption (12.3 ± 3.2 vs. 12.2 ± 4.0 ml/min/kg; p = 0.906). Thus, over long implant periods, patients showed improvement of their exercise performance in the submaximal load range, but no change in the aerobic capacity was observed.

Supervised exercise training versus usual care in ambulatory patients with left ventricular assist devices: A systematic review

Implantation of left ventricular assist devices (LVAD) has increased because of improved safety profile and limited availability of heart transplantation. Although supervised exercise training (ET) programs are known to improve exercise capacity and quality of life (QoL) in heart failure (HF) patients, similar data is inconclusive in LVAD patients. Thus, we performed a systematic review on studies that incorporated supervised ET and measured peak oxygen uptake in LVAD patients. A total of 150 patients in exercise and 55 patients in control groups were included from 8 studies selected from our predefined criteria. Our systematic review suggests supervised ET has an inconsistent effect on exercise capacity and QoL when compared to control groups undergoing usual care. A quantitative sub-analysis was performed with 4 studies that provided enough data to compare peak oxygen uptake and QoL at baseline and at follow-up. After at least 6 weeks of training, LVAD patients undergoing supervised ET demonstrated significant improvement in exercise capacity (standardized mean difference [SMD] = 0.735, 95% Confidence Interval-[CI], 0.31-1.15 units of the standard deviation, P = 0.001) and QoL scores (SMD = 1.58, 95% CI 0.97-2.20 units of the standard deviation, P <0.001) when compared to the usual care group, with no serious adverse events with exercise. These results suggest that supervised ET is safe and can improve patient outcomes in LVAD patients when compared to the usual care.

Comparison of novel physiological load-adaptive control strategies for ventricular assist devices

Terminal heart failure (HF) is the most prevalent cause of death in the Western world and the implantation of a left ventricular assist device (LVAD) has become the gold standard therapy today. Most of the actually implanted devices are driven at a constant speed (CS) regardless of the patient’s physiological demand. A new physiological controller [power ratio (PR) controller], which keeps a constant ratio between LVAD power and left ventricular power, a previous concept [preload responsive speed (PRS) controller], which adds a variable LVAD power to reach a defined stroke work, and a CS controller were compared with an unimpaired ventricle in a full heart computer simulation model. The effects of changes in preload, afterload and left ventricular contractility are displayed by global hemodynamics and ventricular pressure-volume loops. Both physiological controllers demonstrated the desired load dependency, whereas the PR controller exceeded the PRS controller in response to an increased load and contractility. Response was inferior when preload or contractility was decreased. Thus, the PR controller might lead to an increased exercise tolerance of the patient. Additional studies are required to evaluate the controllers

Physical Capacity in LVAD Patients: Hemodynamic Principles, Diagnostic Tools and Training Control

Over time left ventricular assist devices (LVAD) have become an alternative to heart transplantation because of enormous technical development and miniaturization. Most patients present a significant improvement in clinical conditions and exercise capacity. Nevertheless, exercise tolerance remains markedly limited even after LVAD implantation compared to a control group. The complex physiological and hemodynamic changes in LVAD patients, both at rest and during exercise, are not yet understood, or at least not completely.

It is the aim of the present paper to describe the current state of scientific knowledge. Furthermore, the spectrum of diagnostic tools, including the noninvasive inert gas rebreathing method for measurement of cardiac output and associate parameters, are discussed. Options for training control in this special patient group are presented.