Schneider F, Martin D T, Schick E C, Gaasch W H
Department of Internal Medicine, Lahey Hitchcock Medical Center, Burlington, Massachusetts 01805, USA.
Am J Cardiol. 1997 Sep 1;80(5):586-90. doi: 10.1016/s0002-9149(97)00426-8.
In atrial fibrillation (AF), beat-to-beat changes in left ventricular (LV) systolic performance are caused by variations in filling (preload), aortic pressure (afterload), and ventricular inotropic or contractile state. These factors are known to be influenced by the preceding diastolic or RR interval (RR1), but the independent impact of variations in the pre-preceding RR interval (RR2) on contractile state is not well defined. This aspect was studied in 10 patients with lone AF and 8 with coronary artery disease by measuring LV peak ejection velocity (V[pe] Doppler echocardiography) in 80 to 100 consecutive cardiac cycles. V(pe) was plotted against RR1 for beats with a short RR2 and for beats with a long RR2. Such function-interval plots indicate a direct relation between V(pe) and RR1 (for RR1 = 500 to 1,000 ms). In lone AF, the slope (linear fit) of V(pe) versus RR1 was similar for short and long RR2 (slopes = 46 and 50 s[-1]). V(pe), calculated from best linear fit and a common RR1, was consistently higher when RR2 was short than when it was long. At an RR1 = 750 ms, V(pe) (% of max) was 87 +/- 6% when RR2 was short versus 76 +/- 6% when RR2 was long, p <0.05. Results were similar in patients with coronary artery disease and the observed interval-dependent potentiation of contractile state was preserved in patients with a low ejection fraction. By comparing V(pe) at a common RR1, the effects of time-dependent changes in LV preload and afterload are minimized if not abolished. Thus, differences in V(pe) reflect differences in contractile state caused by variations in RR2. Data confirm interval-dependent alterations in contractile state that are likely an expression of the force-frequency relation. Studies of LV function in AF should incorporate a consideration of cycle length-dependent changes in LV contractile state.
在心房颤动（AF）中，左心室（LV）收缩功能的逐搏变化是由充盈（前负荷）、主动脉压力（后负荷）以及心室变力性或收缩状态的变化引起的。已知这些因素受前一个舒张期或RR间期（RR1）的影响，但前前RR间期（RR2）变化对收缩状态的独立影响尚不明确。通过在80至100个连续心动周期中测量LV峰值射血速度（V[pe]，采用多普勒超声心动图），对10例孤立性AF患者和8例冠状动脉疾病患者的这一方面进行了研究。针对RR2短的搏动和RR2长的搏动，将V(pe)与RR1绘制在一起。这种功能-间期图表明V(pe)与RR1之间存在直接关系（RR1 = 500至1000毫秒）。在孤立性AF中，RR2短和RR2长时，V(pe)与RR1的斜率（线性拟合）相似（斜率分别为46和50 s[-1]）。根据最佳线性拟合和共同的RR1计算得出的V(pe)，当RR2短时始终高于RR2长时。在RR1 = 750毫秒时，RR2短时V(pe)（最大值的百分比）为87±6%，RR2长时为76±6%，p<0.05。冠状动脉疾病患者的结果相似，且在射血分数低的患者中观察到的收缩状态的间期依赖性增强得以保留。通过比较共同RR1时的V(pe)，LV前负荷和后负荷随时间变化的影响即使未消除也会降至最低。因此，V(pe)的差异反映了RR2变化引起的收缩状态差异。数据证实了收缩状态的间期依赖性改变，这可能是力-频率关系的一种表现。对AF中LV功能的研究应考虑LV收缩状态的周期长度依赖性变化。
