An overview of the cardiopulmonary exercise testing assessment in patients with left ventricular assist devices and heart failure with reduced ejection fractions

ABSTRACT

Background: Patients with advanced heart failure with reduced ejection fractions have decreased life expectancies. Treatment options include cardiac transplantation, left ventricular assist device (LVAD) insertion as a destination therapy, and palliative care. These LVADs do prolong survival and improve their quality of life. However, their effect on the maximum exercise capacity seems limited. This study reviewed recent literature reporting cardiopulmonary exercise testing in patients with LVADs to better understand the clinical benefits with these devices and the post insertion factors affecting exercise performance.

Methods: The PubMed database was searched using the MeSH terms “heart-assist device,” “exercise test,” and “heart failure.” Search filters included English language publication. The focus was to identify articles which reported VO₂ max pre and post LVAD insertion, identified limiting factors in VO₂ max post LVAD, and analyzed the VO₂ burden during activities of daily living in patients with LVADs.

Results: This analysis used 11 articles which reported results in the 346 patients. The mean age was 53.1 ± 6.7 years, and 77% of the patients were male. The mean peak VO₂ was 14.0 ± 2.5 L/kg/min. The VO₂ max did not increase post LVAD insertion. Multiple factors were associated with the limitation in the VO₂ max in these patients post insertion. These included characteristics of the LVAD device, right heart function, chronotropic responses, tricuspid and aortic valve function, gas exchange, and hemodynamic stress based on BNP levels. Some patients who underwent cardiac rehabilitation had significant increases in VO₂ max, 6-minute walk distance, muscle strength, and quality of life questionnaire scores. In 1 study with 15 patients, the VO₂ increased from 16.8 ± 3.7 to 19.3 ± 4.6 mL O₂/kg/min. The 6-minute walk distance increased from 462 ± 88 m to 527 ± 76 m. Measurement of VO₂ during routine activities of daily living in these patients demonstrated that they used a significant fraction of their VO₂ max in activities; for example, walking upstairs required 66 ± 10% of peak VO₂.

Conclusion: Patients with advanced heart failure and LVAD insertion continue to have low peak VO₂ max on cardiopulmonary exercise testing. A complex set of factors, especially right ventricular dysfunction, are associated with exercise limitation. These patients do improve with cardiac rehabilitation but still use a significant fraction of their peak VO₂ to undertake routine daily activities.

Keywords: Left ventricular assist device, heart failure, cardiopulmonary exercise test