Cardiac conditions. Certain subtypes of troponin (cardiac I and T) are very sensitive and specific indicators of damage to the heart muscle (myocardium). They are measured in the blood to differentiate between unstable angina and myocardial infarction (heart attack) in people with chest pain or acute coronary syndrome.
Virtual reality (VR) typically refers to computer technologies that use virtual reality headsets to generate the realistic images, sounds and other sensations that replicate a real environment or create an imaginary setting. VR also simulates a user's physical presence in this environment.
Re: Deference between VR and Non VR lens. VR stands for vibration reduction and is what Nikon calls it's version of optical image stabilization. Image stabilization basically counters the camera shake you get from holding the camera, making it so you can use slightly faster shutter speeds than without it. Non-VR lenses do not have this feature, but cost less than VR lenses.