I had a heart attack in Sept 2012 while in the swiming pool. After a successful stent placement (LDA), I resumed my swimming . I average 4 miles/week since Jan 2013. I kept my heart rate within the suggested Max (135 beat/ minutes). I am 59 years old, currently take Metoprolol, Avatorstatin and Metformin. My recent blood test had shown everything is in the normal range. Question: There are days that I wanted to push my body a bit harder (swimm faster) . Is it wise ? It is quite boring to do the same thing everyday at the same intensity. If possible, how much harder can I go ? Since the only way for me to quantify my effort is by measuring my heart rate ( I have a device that monitor my pulse rate while swimming), would 145 beats/minute acceptable and safe ? Swimming is my only form of excercise as my knees do not allow me to run or walk for a long period. Thank you