Relationship between Pulsatility Index and Volume Status in Patients with Left Ventricular Assist Devices

Abstract

Introduction Volume overload continues to be a common complication after left ventricular assist device (LVAD) implantation due to years of heart failure complicated with pulmonary hypertension, right ventricle dysfunction and poor nutritional status. In fact, fluctuation in volume status is one of the most dynamic parameters in patients with LVADs and becomes one of the key components of the routine clinical evaluation in these patients. We hypothesize that postural changes in the pulsatility index (PI) may be an accurate non-invasive measure of volume status that can potentially be easily used in clinic or by patients at home to adjust their fluid intake and diuretics. Methods We included patients at least 1 month post-LVAD implantation being followed in the Advance Heart Failure Clinic at Scripps Clinic. We excluded patients unable to stand for at least 10 minutes or too unstable to cooperate. We measured systolic (SBP), diastolic and mean (MAP) blood pressure, heart rate and LVAD parameters including PI supine and after 2 minutes of standing. Supine and standing inferior vena cava (IVC) assessment was performed by bedside echocardiography. All measurements were obtained within 1 hour with no interval intervention. Results We included 20 patients status post continuous flow LVAD. Mean time from implant was 947.5 days (range 55 - 2533 days). We were able to obtain both supine and standing echocardiograms for IVC assessment in 14 (70%) patients. We found a positive and significant correlation between postural changes in PI and postural changes in IVC (R= 0.61, p = 0.02). There were no significant changes in supine and standing SBP and MAP (SBP: 101 ± 10 and 100 ± 10 mmHg, p=0.59; MAP: 82 ± 6 and 85 ± 7 mmHg, p=0.13). We did not find a statistically significant correlation between postural changes in PI and postural changes in MAP (r = 0.15, p = 0.55). Five patients (25%) had positive orthostatic vital signs and 14 (70%) had documented PI events the days prior to the study inclusion. There was a trend for larger postural PI changes in patients with positive orthostatic vital signs or PI events, although this did not reach statistical significance (p = 0.88 and p = 0.79, respectively). Conclusion Changes in LVAD PI seem to correlate with volume status rather than systemic blood pressure. There is a trend for larger postural PI changes in orthostatic patients and those with documented PI events. Postural PI change assessment could aid in the immediate bedside evaluation of volume status in LVAD patients. Furthermore, PI changes could be documented by patients remotely and used by providers for interval treatments without presentation to clinic.