Wu Tsu-Juey, Lin Shien-Fong, Weiss James N, Ting Chih-Tai, Chen Peng-Sheng
Division of Cardiology, Department of Medicine, Taichung Veterans General Hospital and Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine, Taipei, Taiwan.
Circulation. 2002 Oct 1;106(14):1859-66. doi: 10.1161/01.cir.0000031334.49170.fb.
The combined effects of excitability and action potential duration (APD) restitution on wavefront dynamics remain unclear.
We used optical mapping techniques to study Langendorff-perfused rabbit hearts. In protocol IA (n=10), D600 at increasing concentrations was infused during ventricular fibrillation (VF). With concentration increased to 0.5 mg/L, fast VF (dominant frequency, 19.1+/-1.8 Hz) was consistently converted to ventricular tachycardia (VT). However, increasing D600 further to 2.5 or 5.0 mg/L converted VT to slow VF (11.9+/-2.3 Hz, P=0.0011). In an additional 4 hearts (protocol IB), tetrodotoxin converted a preexisting VT to slow VF (11.0+/-1.4 Hz). Optical maps show wandering wavelets in fast VF, organized reentry in VT, and spatiotemporal periodicity in slow VF. In protocol II, we determined APD and conduction time(-1) (CT(-1)) restitutions during D600 infusion. CT(-1) was used as an estimate of excitability. At 0.1 mg/L, APD and CT(-1) restitutions were steep and flat, respectively. APD restitution became flattened when D600 increased to 0.5 mg/L, converting fast VF to VT. Further increasing D600 to 2.5 or 5.0 mg/L steepened CT(-1) restitution and widened the range of S(1) pacing cycle lengths over which CT(-1) decreased, converting VT to slow VF.
Two types of VF exist in isolated rabbit hearts. Fast (type I) VF is associated with a steep APD restitution, a flat CT(-1) restitution, and wandering wavelets. Slow (type II) VF is associated with a flat APD restitution, a steep CT(-1) restitution, and spatiotemporal periodicity. Both excitability and APD restitution are important in VF maintenance.
兴奋性和动作电位时程（APD）恢复对波前动力学的联合作用仍不清楚。
我们使用光学标测技术研究离体灌注的兔心脏。在方案IA（n = 10）中，在心室颤动（VF）期间输注浓度递增的地尔硫䓬（D600）。当浓度增加至0.5 mg/L时，快速VF（主导频率，19.1±1.8 Hz）持续转变为室性心动过速（VT）。然而，将D600进一步增加至2.5或5.0 mg/L会使VT转变为缓慢VF（11.9±2.3 Hz，P = 0.0011）。在另外4个心脏（方案IB）中，河豚毒素将预先存在的VT转变为缓慢VF（11.0±1.4 Hz）。光学标测显示快速VF中有游走小波，VT中有组织折返，缓慢VF中有时空周期性。在方案II中，我们在输注D600期间测定了APD和传导时间倒数（CT⁻¹）恢复情况。CT⁻¹用作兴奋性的估计值。在0.1 mg/L时，APD恢复陡峭而CT⁻¹恢复平坦。当D600增加至0.5 mg/L时，APD恢复变平坦，快速VF转变为VT。将D600进一步增加至2.5或5.0 mg/L会使CT⁻¹恢复变陡峭，并拓宽CT⁻¹降低时的S1起搏周期长度范围，将VT转变为缓慢VF。
离体兔心脏中存在两种类型的VF。快速（I型）VF与陡峭的APD恢复、平坦的CT⁻¹恢复及游走小波相关。缓慢（II型）VF与平坦的APD恢复、陡峭的CT⁻¹恢复及时空周期性相关。兴奋性和APD恢复在VF维持中均很重要。
