My resting heart rate is about 70-73 beats a minute which is about average. My fitness isn't that great I have to admit. I've recently lost some weight although I am overweight although I have lost some weight (15lbs) since december.
I have never had any problems in walking before and the little bit of walking I did do wasn't a part of any fitness regime. I used to go to the gym for hours on end at a time until last year when I gained a lot of weight (69lbs) through bad eating habits.
i have previously been very underweight (82lbs) in 2007, then gained 69lbs last year and became overweight which could possibly be a reason for my poor physical condition.
Of course - go see your doctor!
You didn't make any mention if this was a new exercise regimen, if you are overweight or out of shape, your age, etc, so it's hard to know if 161 is high for you. For me, anything short of jogging on a treadmill, even for an hour (did it yesterday), it's hard for me to get my heart rate over 120-130. And I'm not in any spectacular shape. So compared to that, yeah, 161 sounds really high for a very slow walk.
But all of that is really conjecture until you've been to a doctor who can assess your situation.
Good luck!
You didn't tell us what you normal rest heart rate is. You description of you physical activity level that resulted in a HR of 161 is also insufficient to reach any conclusions. There are no statements regarding your general physical condition (sounds poor) or if you were able to walk in the past without such HR and breathlessness.
But, from what you have said I would say yes, see you primary care physician soon. s/he may refer you to a cardiologist, but in any case ask for an electrocardiogram as part of your physical check.
Have you had a general physical exam recently? If yes, that gives your doctor a base-line for consideration of your current condition.