Background:Assessment of left ventricular (LV) recovery under continuous-flow LV assist device therapy is hampered by concomitant pump support. We describe derivation of noninvasive pressure-volume loops in continuous-flow LV assist device patients and demonstrate an application in the assessment of recovery.Methods and Results:Using pump controller parameters and noninvasive arterial pressure waveforms, central aortic pressure, outflow conduit pressure gradient, and instantaneous LV pressure were calculated. Instantaneous LV volumes were calculated from echocardiographic LV end-diastolic volume accounting for the integral of pump flow with respect to time and aortic ejection volume derived from the pump speed waveform. Pressure-volume loops were derived during pump speed adjustment and following bolus intravenous milrinone to assess changes in loading conditions and contractility, respectively. Fourteen patients were studied. Baseline noninvasive LV end-diastolic pressure correlated with invasive pulmonary arterial wedge pressure (r²=0.57, root mean square error 5.0 mm Hg, P=0.003). Measured noninvasively, milrinone significantly increased LV ejection fraction (40.3±13.6% versus 36.8±14.2%, P<0.0001), maximum dP/dt (623±126 versus 555±122 mm Hg/s, P=0.006), and end-systolic elastance (1.03±0.57 versus 0.89±0.38 mm Hg/mL, P=0.008), consistent with its expected inotropic effect. Milrinone reduced myocardial oxygen consumption (0.15±0.06 versus 0.16±0.07 mL/beat, P=0.003) and improved myocardial efficiency (43.7±14.0% versus 41.2±15.5%, P=0.001). Reduced pump speed caused increased LV end-diastolic volume (190±80 versus 165±71 mL, P<0.0001) and LV end-diastolic pressure (14.3±10.2 versus 9.9±9.3 mm Hg, P=0.024), consistent with a predictable increase in preload. There was increased myocardial oxygen consumption (0.16±0.07 versus 0.14±0.06 mL O₂/beat, P<0.0001) despite unchanged stroke work (P=0.24), reflecting decreased myocardial efficiency (39.2±12.7% versus 45.2±17.0%, P=0.003).Conclusions:Pressure-volume loops are able to be derived noninvasively in patients with the HeartWare HVAD and can detect induced changes in load and contractility.

中文翻译：

---

使用无创压力容积环在左心室辅助设备支持下深入了解心肌的氧气消耗，能量和效率。

背景：在连续流左心室辅助装置治疗下评估左心室（LV）的恢复受到泵辅助支撑的阻碍。我们描述了连续流LV辅助设备患者中无创压力容积环的推导，并证明了其在康复评估中的应用。方法和结果：使用泵控制器参数和无创动脉压力波形，中心主动脉压力，流出导管压力梯度，计算瞬时LV压力。从超声心动图左室舒张末期容积计算瞬时左室容积，考虑到泵流量相对于时间的积分以及从泵速度波形中得出的主动脉喷射容积。在调节泵速度期间和推注静脉给予米力农后分别得出压力-体积环，以分别评估负荷条件和收缩力的变化。研究了十四名患者。基线无创LV舒张末期压力与有创肺动脉楔压相关（r ² = 0.57，均方根误差为5.0 mm Hg，P = 0.003）。非侵入性测量，米力农显着增加左室射血分数（40.3±13.6％比36.8±14.2％，P <0.0001），最大dP / dt（623±126比555±122 mm Hg / s，P = 0.006），并且收缩弹性（1.03±0.57对0.89±0.38 mm Hg / mL，P = 0.008），与其预期的正性肌力作用一致。米力农可减少心肌耗氧量（0.15±0.06对0.16±0.07 mL /次，P = 0.003）并改善心肌效率（43.7±14.0％对41.2±15.5％，P = 0.001）。降低的泵速导致LV舒张末期容积增加（190±80 vs 165±71 mL，P<0.0001）和左室舒张末期压力（14.3±10.2对9.9±9.3 mm Hg，P = 0.024），与预紧力的可预测增加相一致。尽管卒中工作未改变（P = 0.24），但心肌耗氧量增加（0.16±0.07 vs 0.14±0.06 mL O ₂ / beat，P <0.0001 ），反映出心肌效率降低（39.2±12.7％vs 45.2±17.0％，P = 0.003）。结论：HeartWare HVAD患者可以无创地得出压力-体积环，并且可以检测到负荷和收缩力的诱发变化。