Efimov I R, Huang D T, Rendt J M, Salama G
Department of Cell Biology and Physiology, University of Pittsburgh, School of Medicine, PA 15261.
Circulation. 1994 Sep;90(3):1469-80. doi: 10.1161/01.cir.90.3.1469.
Heterogeneities of repolarization (R) across the myocardium have been invoked to explain most reentrant arrhythmias. The measurement of refractory periods (RPs) has been widely used to assess R, but conventional electrode and extrastimulus mapping techniques have not provided reliable maps of RPs.
Guinea pig hearts were stained with a voltage-sensitive dye to measure fluorescence (F) action potentials (APs) from 124 sites with a photodiode array. AP duration (APD) was defined as the time between depolarization (dF/dt)max and R time points (ie, the time when AP returns to baseline or some percent thereof). However, R time points are difficult to determine because AP downstrokes are often encumbered by drifting baselines and motion artifacts, which make this definition ambiguous. In optical and microelectrode recordings, the second derivative of AP downstrokes is shown to contain an easily detected, unique local maximum. The correlation between the position of this maximum (d2F/dt2)max and R has been tested during altered AP characteristics induced by changes in cycle length, ischemia, and hypoxia. Under these various modifications of the AP, the time points of (d2F/dt2)max fell at 97.0 +/- 2.1% of recovery to baseline. Extrastimulus techniques applied to (1) isolated myocytes, (2) intact hearts, and (3) mathematical simulations indicated that (d2V/dt2)max coincided with the effective RPs of APs. The coincidence of RPs and (d2V/dt2)max was valid within 5 milliseconds, for resting potentials of -75 to -90 mV and extrastimuli three times threshold voltage.
Thus, optical APs and (d2F/dt2)max can be used to map activation, R, and RPs with AP recordings from a single heartbeat.
心肌复极（R）的异质性被认为是大多数折返性心律失常的原因。不应期（RP）的测量已被广泛用于评估R，但传统的电极和额外刺激标测技术尚未提供可靠的RP图。
用电压敏感染料对豚鼠心脏进行染色，通过光电二极管阵列测量124个位点的荧光（F）动作电位（AP）。动作电位时程（APD）定义为去极化（dF/dt）最大值与R时间点之间的时间（即AP回到基线或其某个百分比的时间）。然而，R时间点很难确定，因为AP下降支常受基线漂移和运动伪迹影响，这使得该定义不明确。在光学和微电极记录中，AP下降支的二阶导数显示包含一个易于检测的独特局部最大值。在周期长度、缺血和缺氧改变引起的AP特征改变期间，测试了该最大值（d2F/dt2）最大值的位置与R之间的相关性。在这些AP的各种改变下，（d2F/dt2）最大值的时间点落在恢复到基线的97.0±2.1%处。应用于（1）分离的心肌细胞、（2）完整心脏和（3）数学模拟的额外刺激技术表明，（d2V/dt2）最大值与AP的有效RP一致。对于-75至-90 mV的静息电位和三倍阈值电压的额外刺激，RP与（d2V/dt2）最大值在5毫秒内一致。
因此，光学AP和（d2F/dt2）最大值可用于通过单次心跳的AP记录来标测激活、R和RP。
