Gorcsan J, Gasior T A, Mandarino W A, Deneault L G, Hattler B G, Pinsky M R
University of Pittsburgh Medical Center, PA 15261.
Circulation. 1994 Jan;89(1):180-90. doi: 10.1161/01.cir.89.1.180.
Pressure-volume relations have been established as useful measures of left ventricular (LV) performance. Application of these methods to the intraoperative setting have been limited because of difficulties acquiring LV volume data. Transesophageal echocardiographic automated border detection can measure LV cross-sectional area as an index of volume, which can be coupled with pressure data to construct pressure-area loops on-line. The purpose of this study was to evaluate intraoperative LV performance in patients undergoing coronary bypass surgery before and immediately after cardiopulmonary bypass using on-line pressure-area relations.
Studies were attempted in 13 consecutive patients. Simultaneous measures of LV cross-sectional area, LV pressure, and electromagnetic flow probe-derived aortic flow recorded on a computer work station interfaced with the ultrasound system. Pressure-area loops were compared with simultaneous pressure-volume loops constructed from pressure and flow data during inferior vena caval occlusions before and after bypass. Pressure-volume calculations (end-systolic elastance, maximal elastance, and preload-recruitable stroke work) were then applied to pressure-area loops with area substituted for volume data. Changes in stroke force from pressure-area loops were closely correlated with changes in estimates of stroke work from pressure-volume loops for individual patients before bypass (r = .99 +/- .03, SEE = 5 +/- 2%, n = 10) and after bypass (r = .96 +/- .05, SEE = 5 +/- 2%, n = 9). Pressure-area estimates of end-systolic elastance, maximal elastance, and preload-recruitable stroke force decreased significantly from before to after cardiopulmonary bypass in the 7 patients with paired data sets. Load-dependent measures of LV function (stroke volume, cardiac output, and fractional area change) were unchanged after surgery in these same patients.
Intraoperative pressure-area loops may be acquired and displayed on-line using transesophageal echocardiographic automated border detection and readily analyzed in a manner similar to pressure-volume loops. LV performance was depressed immediately after cardiopulmonary bypass compared with before. On-line pressure-area relations may be clinically useful to assess LV performance in patients undergoing cardiac surgery in whom load and contractility may be expected to vary rapidly.
压力-容积关系已被确立为评估左心室（LV）功能的有用指标。由于获取左心室容积数据存在困难，这些方法在术中的应用受到限制。经食管超声心动图自动边界检测可测量左心室横截面积作为容积指标，并可与压力数据相结合以在线构建压力-面积环。本研究的目的是利用在线压力-面积关系评估冠状动脉搭桥手术患者在体外循环前及刚结束体外循环后术中的左心室功能。
对连续13例患者进行了研究。在与超声系统相连的计算机工作站上同时测量左心室横截面积、左心室压力以及电磁流量探头测得的主动脉流量。将压力-面积环与在体外循环前后下腔静脉阻断期间由压力和流量数据构建的同步压力-容积环进行比较。然后将压力-容积计算值（收缩末期弹性、最大弹性和可预负荷诱发的每搏功）应用于以面积替代容积数据的压力-面积环。对于个体患者，在体外循环前（r = 0.99 ± 0.03，标准误差估计值[SEE] = 5 ± 2%，n = 10）和体外循环后（r = 0.96 ± 0.05，SEE = 5 ± 2%，n = 9），压力-面积环测得的每搏力变化与压力-容积环测得的每搏功估计值变化密切相关。在7例有配对数据集的患者中，体外循环后收缩末期弹性、最大弹性和可预负荷诱发的每搏力的压力-面积估计值较体外循环前显著降低。在这些相同患者中，手术后左心室功能的负荷依赖性指标（每搏量、心输出量和面积变化分数）未改变。
术中压力-面积环可通过经食管超声心动图自动边界检测获取并在线显示，且能以类似于压力-容积环的方式进行分析。与体外循环前相比，体外循环后左心室功能立即降低。在线压力-面积关系对于评估心脏手术患者的左心室功能可能具有临床实用性，因为这些患者的负荷和收缩性可能会迅速变化。
