Yes. Periods of anxiety and being scared allow the sympathetic nervous system to override the parasympathetic system. The subsequent release of catecholamines such as adrenaline cause your heart rate and strength of contraction to increase, in order to supply your muscles with more oxygen and glucose. Your heart therefore gets a workout, just as it would if you went on the treadmill. Your blood pressure increases, as does your breathing rate and depth. These are all good effects. As such, regular "workouts" cause your cardiovascular system to increase in effectiveness, so that even at rest, your heart is beating strongly and so easily supplies muscles/organs etc with their requirements. The reason why stress is nowadays blamed for a lot of health problems is because prolonged stress leads to prolonged sympathetic activity, leading to prolonged high blood pressure. Therefore, even at rest, the heart has to work much harder just to get the blood moving against the pressure gradient. Therefore, when you need your heart to work even harder, such as a quick bout of increased exertion (e.g. running after a bus), it cannot cope and you can get angina or worse. So, in summary, yes, being scared is good for your heart because it gives it a little exercise. It's a bit like a sports car. If you take it out regularly for a spin, it runs smoothly and you get good performance. If you don't use it regularly, then parts start to seize up and degrade. When it then comes to use it for a long journey, you're likely to end up by the roadside with a steaming pile of junk.