I Am A Male, 64 Yrs Of Age. I Have

I am a male, 64 yrs of age. I have long had a normal at-rest heart rate of 52-56BPM. My blood pressure normally ranges in the high 140s-mid 150s over low to mid 80s. (I had experienced a period of hypertensionsome years ago, but now take only 5mg lisinopril/day. I exercise regularly, eat a healthy diet consisting of fresh fruit, grains, vegetables, fish, chicken, some pasta or rice.

I recently noticed that my pulse occasionally pauses, or that I feel a slight flutter in the area just to the left of my sternum. I have never felt light-headed, or felt pain, dizziness, nausea. No headaches.

Can you provide some possible causes?