Left ventricular assist devices (LVADs) have become a common therapy in those resistant to medical heart failure (HF) regimens. It is increasingly becoming important to understand whether specific subsets of patients may benefit from LVAD hemodynamic optimization. African Americans (AA) are disproportionately affected, carrying higher rates of morbidity and mortality as compared with non-AA.1 However, there is limited knowledge regarding the physiology of this phenomenon. Ramp speed optimization studies allow for evaluation of echocardiographic/hemodynamic parameters across a range of LVAD speeds, helping with device troubleshooting and speed optimization.2 Given the history of race-linked discrepancies in surgical interventions,3 understanding the physiological response of AA patients to LVADs may provide insight into understanding differences in outcomes, if they exist, and may impact therapeutic decisions.
Patients with LVADs in the outpatient setting who underwent a standardized hemodynamic/echocardiographic ramp testing2 for speed optimization between May 2014 and August 2016 were prospectively enrolled in this study. Unloading slopes for individual echocardiographic/hemodynamic characteristics were calculated using linear regression modeling per 400 RPM for HeartMate 2 LVADs and 100 RPM for HeartWare LVADs. Unloading slopes between AA and non-AA were compared via unpaired two-sample t tests. All-cause and HF readmissions were compared between groups using Wilcoxon rank sum tests.
Patient characteristics and pre-LVAD implantation hemodynamic parameters are summarized in Table 1 for the 65 patients, including 26 AA, enrolled in the study. AA were younger, more likely to be female, and had higher rates of nonischemic cardiomyopathy as compared with non-AA. Pre-LVAD, baseline, and set-speed echocardiographic (valvular insufficiency, left ventricular end-diastolic diameter [LVEDD], and right ventricle function) and hemodynamic parameters were similar between the AA and non-AA group, with the exception of a higher set-speed cardiac output (CO; 5.9 ± 1.7 vs. 5.1 ± 1.0 L/min, p = 0.03) in AA.
The relationships between RPM steps with each of the echocardiographic and hemodynamics parameters are summarized in Table 2. Hemodynamic response to ramp testing was more pronounced in the AA group given more rapid increase in CO and cardiac index, as well as rapid decrease in LVEDD as compared with non-AA. Similar results were seen when limiting to those with HeartMate 2 devices.
Over a mean follow-up of 353 ± 168 days, AA patients had higher rates of all-cause readmissions (2.62 ± 2.09 vs. 1.66 ± 1.56 admissions/patient-year, p = 0.03), but not HF readmissions (0.40 ± 0.99 vs. 0.36 ± 0.24 admissions/patient-year, p = 0.49). AA and non-AA patients who achieved optimal filling pressures (central venous pressure ≤12 and pulmonary capillary wedge pressure ≤18 mm Hg) had similar rates of HF readmissions (0.21 ± 0.43 vs. 0.23 ± 0.90 admissions/patient-year, p = 0.51).
We show that despite similar preramp hemodynamics, during speed optimization, a more dramatic response in hemodynamic and echocardiographic parameters (CO, cardiac index, LVEDD) were seen in AA as compared with non-AA. This may be related to the predominance of nonischemic cardiomyopathy and younger age among the AA group, which predisposes toward greater ventricular and vascular compliance.4 Nonetheless, similar rates of optimal hemodynamics were found between AA and non-AA at set-speed, likely leading to the similar HF readmissions between AA and non-AA in the overall sample and the hemodynamically optimized subset.
Previous studies have shown no difference in follow-up outcomes based on race for patients with LVADs.5 Interestingly, this study shows that AA patients with LVADs had an increase in overall readmissions after a ramp study as compared with non-AA patients. It is possible that this is related to the higher percentage of women in the AA group, as there is mounting data that women implanted with LVADs may have a higher readmissions rate, including an increased incidence of neurological events.6 Additionally, factors such as low socioeconomic status and health literacy have been well documented as resulting in disparities in non-Caucasian ethnic groups with HF.7
Limitations of this study include the single-center design, lack of randomization, and small sample size. Further, although this was a prospectively enrolled study, patients were followed for approximately 1 year, leading to relatively low readmission rates and undefined long-term outcomes.
In conclusion, AA patients with LVADs may have a more pronounced hemodynamic response during ramp testing as compared with non-AA patients with LVADs. However, this did not translate to a significant difference in overall hemodynamic optimization or improvement in HF readmissions in AA as compared with non-AA.
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