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🌱 來自: Huppert’s Notes
Cardiac Electrophysiology🚧 施工中
Cardiac Electrophysiology
• Cardiac electrical conduction system: Sinoatrial (SA) node (1° pacemaker) → Atrioventricular (AV) node (stalls conduction; can also act as a backup pacemaker with rate of 40–60 bpm) → Bundle of His → Right/left bundle → Purkinje fibers → Ventricle
• Pacemaker cells (SA/AV node cells) auto matically create electrical impu lses that trigger myocyte cells (atrial/ventricular cells)
- Pacemaker action potential is described using three phases (Phases 0, 3, and 4). It is automatic and initated by a slow inward Ca2+ current. The maximum diastolic potential (analogous to resting membrane potential) iŝ-55 mV (Figure 1.2)
FIGURE 1.2: Cardiac pacemaker cell action potential.
- Myocyte action potential is described using five phases (Phases 0–4). It is automatic and triggered by a fast inward Na+ current. The resting membrane potential is -90 mV, determined by K+ conductance and equilibrium potential (Figure 1.3)
FIGURE 1.3: Cardiac myocyte action potential.
TABLE 1.1 • Hemodynamic Calculations Used Clinically