Continuous-flow left ventricular assist devices: Management in the emergency department

Computational evaluation of heart failure and continuous flow left ventricular assist device support in anaemia

Anaemia is common in end-stage heart failure patients supported with continuous flow left ventricular assist device (CF-LVAD) and is associated with adverse outcomes such as heart failure readmission. This study evaluates the haemodynamic effects of anaemia on cardiac function and cerebral blood flow in heart failure patients supported with CF-LVAD using computational simulations. A dynamic model simulating cardiac function, systemic, pulmonary and cerebral circulations, cerebral flow autoregulatory mechanisms and gas contents in blood was used to evaluate the effects of anaemia and iron deficiency in heart failure and during CF-LVAD support. CF-LVAD therapy was simulated by a model describing HeartMate 3. Anaemia and iron deficiency were simulated by reducing the haemoglobin level from 15 to 9 g/dL and modifying scaling coefficients in the models simulating heart chamber volumes. Reduced haemoglobin levels decreased the arterial O2 content, which increased cerebral blood flow rate by more than 50% in heart failure and during CF-LVAD assistance. Reduced haemoglobin levels simulating anaemia had minimal effect on the arterial and atrial blood pressures and ventricular volumes. In contrast, iron deficiency increased end-diastolic left and right ventricular diameters in heart failure from 6.6 cm to 7 cm and 2.9 cm to 3.1 cm and during CF-LVAD support from 6.1 to 6.4 cm and 3.1 to 3.3 cm. The developed numerical model simulates the effects of anaemia in failing heart and during CF-LVAD therapy. It is in good agreement with clinical data and can be utilised to assess CF-LVAD therapy.

Characteristics and Outcomes of Patients in the Emergency Department with Left Ventricular Assist Devices

Introduction

Left ventricular assist devices (LVAD) are increasingly common among patients with heart failure. The unique physiologic characteristics of patients with LVADs present a challenge to emergency clinicians making treatment and disposition decisions. Despite the increasing prevalence of LVADs, literature describing emergency department (ED) visits among this population is sparse. We aimed to describe clinical characteristics and outcomes among patients with LVADs seen in two quaternary-care EDs in a five-year period. Secondarily, we sought to evaluate mortality rates and ED return rates for bridge to transplant (BTT) and destination therapy (DT) patients.

Methods

We conducted a retrospective cohort study of adult patients known to have an LVAD who were evaluated in two quaternary-care EDs from 2013-2017. Data were collected from the electronic health record and summarized with descriptive statistics. We assessed patient outcomes with mixed-effects logistic regression models including a random intercept to account for patients with multiple ED visits.

Results

During the five-year study period, 290 ED visits among 107 patients met inclusion criteria. The median patient age was 61 years. The reason for LVAD implantation was BTT in 150 encounters (51.7%) and DT in 140 (48.3%). The most common presenting concerns were dyspnea (21.7%), bleeding (18.6%), and chest pain (11.4%). Visits directly related to the LVAD were infrequent (7.9%). Implantable cardioverter-defibrillator discharge was reported in 3.4% of visits. A majority of patients were dismissed home from the ED (53.8%), and 4.5% required intensive care unit admission. Among all patients, 37.9% returned to the ED within 30 days, with similar rates between DT and BTT patients (32.1 vs 43.3%; P = 0.055). The LVAD was replaced in three cases (1.0%) during hospitalization. No deaths occurred in the ED, and the mortality rate within 30 days was 2.1% among all patients.

Conclusion

In this multicenter cohort study of ED visits among patients with an LVAD, dyspnea, bleeding, and chest pain were the most common presenting concerns. Visits directly related to the LVAD were uncommon. Approximately half of patients were dismissed home, although return ED visits were common.

Defibrillation in the Cardiac Arrest Patient

Defibrillation is one of the few interventions known to favorably impact survival in cardiac arrest. In witnessed arrest, survival improves with defibrillation as early as possible, whereas it may improve outcomes to administer high-quality chest compressions for 90 seconds before defibrillation in unwitnessed arrest. Minimizing pre-, peri-, and post-shock pauses has been shown to have mortality benefits. Refractory ventricular fibrillation has high mortality rates, and there is ongoing research into promising adjunctive treatment modalities. There remains no consensus on optimal pad positioning and defibrillation energy level, however, recent data suggest anteroposterior pad placement may be superior to anterolateral placement.