Haemodynamic Effect of Left Atrial and Left Ventricular Cannulation with a Rapid Speed Modulated Rotary Blood Pump During Rest and Exercise: Investigation in a Numerical Cardiorespiratory Model

PURPOSE

The left atrium and left ventricle are the primary inflow cannulation sites for heart failure patients supported by rotary blood pumps (RBPs). Haemodynamic differences exist between inflow cannulation sites and have been well characterized at rest, yet the effect during exercise with the same centrifugal RBP has not been previously well established. The purpose of this study was to investigate the hemodynamic effect of inflow cannulation site during rest and exercise with the same centrifugal RBP.

METHODS

In a numerical cardiorespiratory model, a simulated heart failure patient was supported by a HeartWare HVAD RBP in left atrial (LAC) and left ventricular cannulation (LVC). The RBP was operated at constant speed and sinusoidal co- and counter-pulse and was investigated in cardiovascular conditions of steady state rest and 80-watt bike graded exercise.

RESULTS

Cardiac output was 5.0 L min^-1 during rest and greater than 6.9 L min^-1 during exercise for all inflow cannulation sites and speed operating modes. However, during exercise, LAC demonstrated greater pressure-volume area and lower RBP flow (1.41, 1.37 and 1.37 J and 5.03, 5.12 and 5.03 L min^-1 for constant speed and co- and counter-pulse respectively) when compared to LVC (pressure-volume area: 1.30, 1.27 and 1.32 J and RBP flow: 5.56, 5.71 and 5.59 L min^-1 for constant speed and co- and counter-pulse respectively).

CONCLUSION

For a simulated heart failure patient intending to complete exercise, LVC seems to assure a better hemodynamic performance in terms of pressure-volume area unloading and increasing RBP flow.

Approaches to improving exercise capacity in patients with left ventricular assist devices: an area requiring further investigation

Introduction: Left ventricular assist device (LVAD) implantation has become a well-established treatment option for patients with end stage heart failure (HF) who are refractory to medical therapy. While LVADs implantation does effectively improve hemodynamic performance many patients still possess peripheral pathological adaptations often present in end-stage HF. Therefore, increased attention has been placed on investigating the effects of exercise training for patients with LVADs to improve clinical outcomes. However, the available evidence on exercise training for patients with LVADs is limited. Areas covered: The purpose of this narrative review is to summarize: 1) The evolution of LVAD technology and usage; 2) The physiological responses to exercise in patients with LVADs; 3) The available evidence regarding exercise training; 4) Potential strategies to implement exercise training programs for this patient population. Expert opinion: The available evidence for exercise training to improve physical function and clinical outcomes for patients with LVADs is promising but limited. Future research is needed to further elucidate the ideal exercise training parameters, method of delivery for exercise training, and unique barriers and facilitators to exercise training for patients receiving LVAD implantation.

Prevalence of exertional oscillatory ventilation in continuous-flow left ventricular assist device recipients

Background

Exercise oscillatory ventilation is an ominous outcome sign in heart failure due to reduced left ventricular ejection fraction; currently, the prevalence of exercise oscillatory ventilation is unknown in left ventricular assist device recipients.

Methods

We studied cardiopulmonary exercise testing in heart failure due to reduced left ventricular ejection fraction or left ventricular assist device patients and exercise oscillatory ventilation was defined according to Kremser's criteria.

Results

The occurrence of exercise oscillatory ventilation was similar in either heart failure due to reduced left ventricular ejection fraction (192 patients, 8%) or left ventricular assist device patients (85 recipients, 10%), even though the mean peak oxygen consumption and elevated ventilatory response to exercise slope was lower and higher in left ventricular assist device recipients, respectively, but the occurrence of exercise oscillatory ventilation was comparable among heart failure patients due to reduced left ventricular ejection fraction and left ventricular assist device, if those with impaired exercise capacity were considered. Of note, left ventricular assist device recipients with exercise oscillatory ventilation had a higher end-diastolic left ventricular volume and systolic pulmonary artery pressure at rest.

Conclusions

Using the largest cohort of left ventricular assist device patients performing cardiopulmonary exercise testing, we demonstrated that the occurrence of exercise oscillatory ventilation is similar in heart failure due to reduced left ventricular ejection fraction and left ventricular assist device patients. Recipients with exercise oscillatory ventilation might have haemodynamic and ventilatory dysfunction during exercise, but other factors could play a role, i.e. the duration and severity of heart failure before left ventricular assist device implantation together with the coexistence of morbidity.