When we think of resistance training we primarily think of muscle strength with a cardiovascular response. Where as endurance training is primarily cardiovascular strength with muscle strength response.
The bigger picture we need to look at is training the heart as a WHOLE.
Resistance Training (RT) and High Intensity Interval Training (HIIT) increases the heart rate and strengthens one part of the heart (the left ventricle mainly). Leaving the rest of the heart without proper stimulus to adapt.
In order to combat this problem we need to include cardiovascular strength training at a moderate aerobic range (70-85% of MHR) to increase the vascular network, to allow a greater delivery of blood to the heart itself and increase stroke volume.
Thus creating a strength network as a whole.