A novel method for the prediction of focal wavefront origins in cardiac arrhythmias
Graphical abstract
Introduction
Cardiac arrhythmias are common and cause a substantial burden of symptoms and morbidity, and catheter ablation has become a commonly utilized treatment [1].
Three-dimensional electroanatomic mapping (EAM) was developed to aid in the mapping and ablation of complex arrhythmias. EAM is performed using a computer system that records serial measurements of local cardiac activation relative to a fixed fiducial point, and the location of those measurements in space [2]. With a sufficient number of measurements, a three-dimensional reproduction of the chamber anatomy can be produced, upon which activation data can be plotted. Information obtained about the magnitude of the voltage recorded at each site may provide information about potential arrhythmia substrate.
In this method, the creation of a usable map requires 1) a fiducial electrogram (EGM) with a stable location and morphology 2) a sampled EGM that has a discreet activation for unambiguous annotation 3) persistence of the arrhythmia with a stable cycle length and 4) time to create a map of sufficient resolution.
While this approach works for many patients, a substantial number may have multiple and/or transient arrhythmias that do not lend themselves easily to conventional mapping. Other patients may have abnormal substrate with EGMs that may be diffuse and low-voltage (Fig. 1), hampering the accurate annotation of local activation time.
We sought to develop a new method of mapping arrhythmias that might overcome some of these limitations. We postulated that the origin of focal arrhythmia wavefronts could be mathematically extrapolated based on the relative timing of recorded EGMs during arrhythmia, the distance between them, and a measurement of conduction velocity (CV). In this report, we describe the derivation of the extrapolation formula and its accuracy in a retrospective feasibility study.
Section snippets
Derivation of prediction formula
The derivation of the prediction formula is as follows. Consider two recording bipoles (A and B) located in a cardiac chamber during an arrhythmia of focal origin (Fig. 2). The relative EGM activation recorded at A and B will depend on the location of the wavefront origin (O) with respect to the two bipoles. In Fig. 2A, A and B measure simultaneous activation. This situation could be seen if the origin if the tachycardia was located directly between, equidistant above, or equidistant below A
Results
Twelve tachycardias were studied in 12 patients. Patient and rhythm characteristics are given in Table 1. Wavefront activation initiated in the atrium in 5 patients and in the ventricles in 7 patients. Three patients had orthodromic reciprocating tachycardias utilizing accessory pathways. Although these arrhythmias are reentrant, these patients were included because activation from the perspective of the chamber mapped proceeds from a focal origin located at the site of the accessory pathway.
Discussion
We propose a novel method of mapping arrhythmia wavefront origins that uses a limited number of easily obtained measurements and was successfully implemented in an initial feasibility study.
This method overcomes some of the limitations of conventional mapping. Stability of neither the fiducial point morphology nor the arrhythmia cycle length is required. Prediction curves may be generated in a limited period of time, allowing for the mapping of short-lived or unstable rhythms. While
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Conflicts of interest
None of the authors report any relevant conflict of interest related to the work submitted.
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Present Address: Columbia University College of Physicians and Surgeons 622 W 168th Street, New York, NY 10032.