Prinsze F J, Bouman L N
Department of Physiology, University of Amsterdam, Academic Medical Centre, The Netherlands.
Cardiovasc Res. 1991 Jul;25(7):546-57. doi: 10.1093/cvr/25.7.546.
The aim was to investigate the mechanism of the intrinsic sinus node recovery time.
The effect of 2 min periods of 20% and 50% overdrive on the electrical activity of fibres in the sinoatrial node was studied in isolated atria of rabbits under complete autonomic blockade (atropine 3 x 10(-6) M and propranolol 3 x 10(-7) M).
Rabbits (New Zealand white) of either sex up to 3 kg weight were used.
The first returning cycle after overdrive is prolonged not only by the time needed for retrograde plus antegrade conduction but also by a delay in impulse formation (overdrive suppression). During pacing, action potential duration, amplitude, maximum diastolic potential (only in primary pacemaker fibres), and diastolic depolarisation rate were all decreased. Action potential duration, amplitude and maximum diastolic potential returned to control value during the first cycle following a period of overdrive, but diastolic depolarisation remained depressed during many consecutive cycles. In primary pacemaker fibres, diastolic depolarisation appeared to be depressed throughout diastole. In latent pacemaker fibres diastolic depolarisation was depressed only in the second part of the diastole.
Sinus node recovery time has two components: (1) a conduction component of both retrograde and antegrade conduction, and (2) a depression of the automaticity (= overdrive suppression), which is only due to a slowing of diastolic depolarisation.
旨在探究固有窦房结恢复时间的机制。
在完全自主神经阻滞（阿托品3×10⁻⁶ M和普萘洛尔3×10⁻⁷ M）下，研究20%和50%超速驱动2分钟对兔离体心房窦房结纤维电活动的影响。
使用体重达3千克的雌雄新西兰白兔。
超速驱动后的首个复极周期延长，这不仅是由于逆行和前向传导所需时间，还由于冲动形成延迟（超速抑制）。起搏期间，动作电位持续时间、幅度、最大舒张电位（仅在初级起搏纤维中）和舒张期去极化速率均降低。在超速驱动一段时间后的首个周期内，动作电位持续时间、幅度和最大舒张电位恢复至对照值，但舒张期去极化在多个连续周期内仍受抑制。在初级起搏纤维中，舒张期去极化在整个舒张期似乎均受抑制。在潜在起搏纤维中，舒张期去极化仅在舒张期的后半部分受抑制。
窦房结恢复时间有两个组成部分：（1）逆行和前向传导的传导部分，以及（2）自律性的抑制（=超速抑制），这仅归因于舒张期去极化减慢。
