The cardiac conduction velocity vector (VV) provides insight into the characteristics of the myocardial tissue and can be deployed to treat different heart diseases. The cardiac VV can be estimated by processing the intracardiac electrograms. In this paper, we analyse the VV estimation error of two computationally efficient heuristic estimators: 1-maximum time difference (MTD) and 2-minimum velocity (MinV). In the MTD, the estimated velocity is a vector in the direction of the vector that connects the first to the last catheter's activated electrode, and the magnitude of the VV is estimated as the ratio of the distance between two electrodes to the delay between their ATs. In the MinV, using a similar procedure as the MTD, we assign a VV to each available electrode pair of the catheter, and the VV with the smallest magnitude is selected as the final estimated VV. We derive the average absolute value and average squared absolute value of the VV estimation error of the MTD and MinV methods for a planar wavefront in a two-dimensional case and confirm the accuracy of our analysis by simulating synthetic data.