CARDIAC OUTPUT WITH PACEMAKERS

提出了一种方法和设备，该方法和设备需要 为植入的起搏器设定最佳频率。方法是 适用于固定频率起搏器以及运动应答型起搏器和 采用连续测量每搏量和射血分数， 通过测量一对电极之间的阻抗变化来检测 右室的起搏导管。冲程音量阻抗 变化(SVDeltaZ)通过单次转换为真实行程体积(SV 单次静脉注射阿司匹林测量心输出量 稀释生理盐水作为指示剂。起搏时的附加电极 用导管检测生理盐水稀释曲线。稀释曲线 电极位于行程-容量测量电极之间 右室(起搏)导管。稀释曲线记录了 单纯性心肌梗死后右室血电阻率的变化 静脉注射稀盐水指示剂。稀释曲线为 通过知道血液以何种方式通过电子方式轻松校准 电阻率变化(DelTAP)对盐度变化的响应 浓度(Deltac)；DELTAP/DELTAC量是特定于给定的 物种。我们已经获得了狗和人的这样的数据。心脏 然后将输出量除以心率，以获得真实每搏量(SV)。 因此，SVDeltaZ是根据真实SV进行校准的；现在冲程音量是 在节拍的基础上提供。射血分数将被确定 根据SVDeltaZ与ZD的比率，其中ZD为右心室。 确定最佳起搏频率的方法包括绘制心脏 输出量(SVDeltaZ乘以起搏率)与起搏率的关系。这样的一个 随着起搏速度的增加，曲线上升到一个平台期。最佳起搏 速率是将曲线带到平台期的最低值。什么也得不到 通过以更快的速度走来。 在房室传导阻滞的狗，心输出量和射血分数将是 源于右室阻抗的变化。心输出量将 与起搏率的关系图。射血分数(SVDeltaZ/ZD)也将 绘制与起搏速度的关系图，以评估其值以确定最佳 起搏率。这一过程将在正常休息和有节奏的情况下进行研究 狗和狗在跑步机上进行适度和剧烈的运动。

It is proposed to create a method and the apparatus needed to enable setting the optimum rate for an implanted pacemaker. The method is applicable to fixed-rate, as well as exercise-responsive pacemakers and employs continuous measurement of stroke volume and ejection fraction, detected by the impedance change meaasured between a pair of electrodes on the pacing catheter in the right ventricle. The stroke volume impedance change (SVDeltaZ) is converted to true stroke volume (SV) by a single measurement of cardiac output using a single intravenous injection of dilute saline as the indicator. Additional electrodes on the pacing catheter are used to detect the saline dilution curve. The dilution-curve electrodes are located between the stroke-volume measuring electrodes on the right-ventricular (pacing) catheter. The dilution curve is a record of the change in resistivity of right-ventricular blood following the single intravenous injection of dilute saline indicator. The dilution curve is easily calibrated electrically by knowing the manner in which blood resistivity changes (Deltap) in response to a change of saline concentration (Deltac); the quantity Deltap/Deltac is specific for a given species. We have already obtained such data for dog and man. Cardiac output is then divided by heart rate to obtain true stroke volume (SV). Thus, the SVDeltaZ is calibrated in terms of true SV; now stroke volume is available on a beat-by-beat basis. Ejection fraction will be determined from the ratio of SVDeltaZ to Zd, where Zd is the right ventricle. The method of identifying the optimum pacing rate involves plotting cardiac output (SVDeltaZ multiplied by pacing rate) versus pacing rate. Such a curve rises to a plateau with increasing pacing rate. The optimum pacing rate is the lowest that brings the curve to the plateau. Nothing is gained by pacing at a higher rate. In dogs with A-V block, cardiac output and ejection fraction will be derived from the right-ventricular impedance change. Cardiac output will be plotted versus pacing rate. Ejection fraction (SVDeltaZ/Zd) will also be plotted versus pacing rate to assess its value to identify the optimum pacing rate. The procedure will be studied in normal resting and paced dogs and dogs exercising moderately and vigorously on the treadmill.