Dears,
if I use a hybrid approach to run my algorithm , this hybrid approach combine distributed memory system using MPI library over 4 identical nodes and shared memory using OMP directives , can I consider this is a heterogeneous Parallel computing ???

Partially, this depends on how you define parallel heterogeneous computing. Generally, the heterogeneous bit implies some element of heterogeneous hardware, traditionally instruction set architecture. For some definitions, network heterogeneity is included, as is heterogeneity in software, such as operating system. Either way, if you are using four identical nodes and the only 'heterogeneous' thing involved is using/mixing MPI and OMP, I would tend to say that this is not considered heterogeneous computing, at least not according to any of the standard definitions.