What Do Shortness Of Breath, Weakness And Rapid Pulse Indicate?

What could the symptoms of shortness of breath, weakness, pulse rapidly rising over 150 on exertion and occasional to frequent night sweats for a 58 yo female mean? She has a history of aortic valve replacement 5 years ago, followed by a pacemaker 1 year ago due to decreased heart rate while sleeping. She was put on midodrine and toprol following placement of the pacemaker but has been off meds past 6 months since loosing insurance coverage.