Contrast Enhanced Ultrasound Evaluation of Skeletal Muscle Perfusion in Response to Left Ventricular Assist Device Therapy

Abstract

Purpose This pilot study investigated the novel application of contrast enhanced ultrasound (CEUS) to quantify skeletal muscle perfusion in patients pre- and post-left ventricular assist device (LVAD) based on the hypothesis that abnormalities in muscle perfusion help account for persistent frailty and poor quality of life (QOL) experienced by some LVAD recipients. Methods Patients had CEUS exams of the quadriceps muscle prior to and 3 months following HeartMate II LVAD implantation using an S3000 Helx scanner (Siemens) with a C6 probe during bolus injections of 0.3 mL of Definity (Lantheus) in resting and fatigue state. Muscle fatigue was achieved by resisted (∼50% of maximum) knee extension until exhaustion. Muscle perfusion was estimated by time intensity curves; contrast arrival time and time to peak contrast intensity were also assessed. Patients reporting >5 points increase in in Kansas City Cardiomyopathy Questionnaire 3 months post-LVAD were classified as responders. Results Seven patients completed baseline and 3-month assessments; four were classified as responders. Average LVAD speed was similar in responders (9150±191 RPMs) vs non-responders (9200±200 RPMs, p=0.75). Compared to pre-operative measures, responders exhibited increased resting muscle perfusion at 3 months (0.04±0.07 ml/s*mg) compared to non-responders (-0.01±0.02 ml/s*mg, p=0.013). Similarly, responding patients exhibited decreased time to peak CEUS enhancement (-33.95±58.6 s) at rest post-LVAD compared to baseline whereas non-responders exhibited an increase (+12.85±22.4 s, p=0.036). Responding patients showed decreased contrast arrival time following exercise at 3 months (24.0±1.8 s fatigue vs. 37.5±6.5 s rest, p=0.029) while non-responders showed no significant difference (p=0.20). There were no significant differences between responders and non-responders in improvement in knee extensor strength (p=0.70), gait speed (p=0.94) or grip strength (p=0.47) at 3 months compared to baseline. All patients tolerated the assessments without adverse events. Conclusion These findings demonstrate the feasibility of CEUS to assess muscle perfusion in LVAD recipients and support the study hypothesis. Further study of the contribution of impaired skeletal muscle perfusion to persistent frailty and poor QOL following LVAD implantation is needed.