Laplacian electrograms and the interpretation of complex ventricular activation patterns during ventricular fibrillation

Laplacian Electrograms and Ventricular Fibrillation. Introduction: During v entricular fibrillation (VF), interpretation of a local electrogram and det ermination of the local activation moment are hampered by remote activity o r intervening repolarization waves. Successful defibrillation depends on cr itical timing of the shock relative to local activation. We tested the appl icability of Laplacian electrograms for detection of the moment of local ac tivation during VF. Methods and Results: From isolated perfused porcine intact hearts, 247 loca l unipolar electrograms were recorded simultaneously (13 x 19 matrix, inter electrode distance 0.3 mm) from the left ventricular wall during sinus rhyt hm, following pacing or during VF. Activation maps were constructed based o n local unipolar electrograms, and Laplacian electrograms were calculated f rom local electrograms and its eight neighbors. The Laplacian electrogram d isplayed a sharp R/S complex with local activation indicated by the moment of zero crossing without interference from remote activity or repolarizatio n waves. Its amplitude increased with decreasing interelectrode distance. F ollowing epicardial stimulation, Laplacian amplitude was significantly larg er than during a breakthrough pattern. During VF, identical unipolar electr ograms corresponded to Laplacian complexes with different morphology. Colli sion of wavefronts was associated with entirely positive Laplacian waveform s; "focal" appearance of activity was associated with an entirely negative waveform. Activation block in the activation maps was correlated with the a ppearance of sustained episodes of negativity or positivity in the Laplacia n electrogram (depending on the location of the recording site relative to the line of block). Conclusion: Laplacian electrograms allow detection of the moment of local a ctivation without interference from remote activity or repolarization, espe cially during complex arrhythmias. The technique applied to automatic sensi ng devices, such as the internal defibrillator, may optimize defibrillation success.