Cardiac hypertrophy is a long term side effect from the use of clenbuterol as this has been documented in life long asthmatics and COPD patients who are on daily doses of the drug. (It's a bronco dilator.) The most dangerous event from short term use would be a hemorrhagic stroke (AKA aneurysm. It's what killed Bruce Lee) or torn aorta from acute, severe high blood pressures of well over 220 diastolic & 120 systolic, tachycardia (pulse over 100 BPM) and atrial fibrillation, that's when your atrium doesn't beat properly and blood just drains into your ventricles instead of pumps (It's not a good thing) and ventricle fibrillation. V Fib is when you're ventricle goes into a quiver rather than a contraction as a result blood doesn't pump back into systemic circulation and you're dead before the EMT's get the truck started. Chronic, untreated high blood pressure is notorious as a chief cause of these types of events and clen and effedra are notorious for causing severe high blood pressures. As with most drugs of this nature if you're young and it doesn't shoot your blood pressure through the stratosphere you're probably safe. (That's probably as in not definitely) but if you're 40 and older, these drugs shouldn't even be a consideration. 40 to 60 YOA are the highest risk years for a heart attack with the risk for stroke increasing at the age of 50. So if you want to play with clen when you're 25, okay. If you want to when you're 45. Russian roulette baby. - charge nurse on a cardiac ICU floor at a major health care facility (Not to be mentioned)