question: I'm 23 and have been experiencing tachycardia, often with shortness of breath, in the evenings and at night. There is no trigger with attacks occurring at rest. I initially put it down to anxiety but I've been 100% stress-free for weeks and yet the attacks have been consistent. My resting heart rate is about 68, and over 100 during attacks. I have no health problems, take no meds and avoid caffiene. What could possibly be the cause?