When being assessed for MMJ, my cardiac arrythmias were taken into account. I'm very prone to cardiac arrythmia (Brugada Syndrome), and THC _is_ causally associated with cardiac arrythmia. It's generally a problem with either naive users or heroic doses though. In turn, cardiac arrythmias in general increase the risk of stroke. Due to my general propensity for death, my medical team looked long and hard at this.

There seems to be little or no evidence of long-term cannabis usage increasing cardiac mortality beyond that of smoking (inhaling particulates and random aromatics). The improvement in my sleeping (yeah, I know, rem sleep blah blah, I get more than 2 hours sleep at a time now) reduces my cardiac risk along with the health benefits of being generally less stressed.