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Correlation of repolarization of ventricular monophasic action potential with ECG in the murine heart

2002; American Physical Society; Volume: 283; Issue: 1 Linguagem: Inglês

10.1152/ajpheart.01091.2001

1522-1539

Stephan B. Danik, Cándido Cabo, Christine Chiello, Sacha Kang, Andrew L. Wit, James Coromilas,

Neuroscience and Neuropharmacology Research

Transgenic mice have become important experimental models in the investigation of mechanisms causing cardiac arrhythmias because of the ability to create strains with alterations in repolarizing membrane currents. It is important to relate alterations in membrane currents in cells to their phenotypic expression on the electrocardiogram (ECG). The murine ECG, however, has unusual characteristics that make interpretation of the phenotypic expression of changes in ventricular repolarization uncertain. The major deflection representing the QRS (referred to as “ a”) is often followed by a secondary slower deflection (“ b”) and sometimes a subtle third deflection (“ c”). To determine whether the second or third deflections or both represent ventricular repolarization, we recorded the ventricular monophasic action potential (MAP) in open-chest mice and correlated repolarization with the ECG. There was no significant correlation by linear regression, between action potential duration to 50% or 90% repolarization (APD 50 or APD 90 ), respectively, of the MAP and either the interval from onset of Q to onset of b (Qb interval) or onset of c (Qc interval). Administration of 4-aminopyridine (4-AP) significantly prolonged APD 50 and APD 90 and the Qb interval, indicating that this deflection on the ECG represents part of ventricular repolarization. After 4-AP, the c wave disappeared, also suggesting that it represents a component of ventricular repolarization. Although it appears that both the b and c waves that follow the Q wave on the ECG represent ventricular repolarization, neither correlates exactly with APD 90 of the MAP. Therefore, an accurate measurement of complete repolarization of the murine ventricle cannot be obtained from the surface ECG.