Toombs C F, Vinten-Johansen J, Yokoyama H, Johnston W E, Julian J S, Cordell A R
Department of Cardiothoracic Surgery, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27103.
Am J Physiol. 1991 Jun;260(6 Pt 2):H1802-9. doi: 10.1152/ajpheart.1991.260.6.H1802.
The slope and diameter axis intercept (D0) of the linear indexes end-systolic pressure-diameter relation (ESPDR), maximum of the first derivative of left ventricular pressure (dP/dtmax)-end-diastolic diameter relation (dP/dtmax-Ded), and dimensional preload-recruitable stroke work relation (PRDSW) are used to describe left ventricular performance. We tested the hypothesis that nonlinearity in these indexes would preclude accurate estimation of slope and D0. In nine pentobarbital-anesthetized dogs, right heart bypass was used to obtain a wide range of pressure-minor axis diameter (sonomicrometry) points from which the three indexes were derived. For ESPDR and dP/dtmax-Ded, a nonlinear fit (y = ax2 + bx + c) approximated the data better than a linear fit, with significant nonlinearity toward the diameter axis (a = -10.28 +/- 3.42 and -111.2 +/- 26.2, respectively, P less than 0.05). Although linear D0 was significantly less than nonlinear D0, this difference was overcome by the diameter intercept at a midrange value of end-systolic pressure or dP/dtmax. PRDSW demonstrated no significant nonlinearity (a = -4.40 +/- 3.53, P = 0.86) but extrapolation to D0 demonstrated linear and nonlinear differences. We conclude that 1) ESPDR and dP/dtmax-Ded demonstrate significant nonlinearity, while PRDSW is well-approximated by a linear fit over a large range of data points; and 2) extrapolation of D0 is inaccurate in all three indexes, while a midrange intercept is independent of the model used to fit the data. Left ventricular performance may be more accurately described by linear slope and midrange diameter intercept over comparable ranges of data.
线性指标——收缩末期压力-直径关系（ESPDR）、左心室压力一阶导数最大值（dP/dtmax）-舒张末期直径关系（dP/dtmax-Ded）以及维度前负荷可招募搏功关系（PRDSW）的斜率和直径轴截距（D0），用于描述左心室功能。我们检验了这样一个假设，即这些指标中的非线性会妨碍对斜率和D0的准确估计。在9只戊巴比妥麻醉的犬中，采用右心旁路来获取一系列压力-短轴直径（超声测量法）数据点，由此得出这三个指标。对于ESPDR和dP/dtmax-Ded，非线性拟合（y = ax2 + bx + c）比线性拟合能更好地拟合数据，在直径轴方向存在显著非线性（a分别为-10.28±3.42和-111.2±26.2，P<0.05）。虽然线性D0显著小于非线性D0，但在收缩末期压力或dP/dtmax的中值处的直径截距克服了这一差异。PRDSW未显示出显著非线性（a = -4.40±3.53，P = 0.86），但外推至D0显示出线性和非线性差异。我们得出结论：1）ESPDR和dP/dtmax-Ded显示出显著非线性，而PRDSW在大范围数据点上通过线性拟合能得到较好近似；2）在所有这三个指标中，D0的外推都是不准确的，而中值截距与用于拟合数据的模型无关。在可比的数据范围内，通过线性斜率和中值直径截距可能能更准确地描述左心室功能。
