Ventricular tachycardia questions

I have ventricular tachycardia...also another arrythmia, supraventricular tachycardia and take Norpace CR 150mg twice a day and toprol xl 50mg twice a day.  I had an ablation which was partially effective in 2001 which allowed me to change medications from Tambacor to the Norpace.  My cardiologist does not want to do another ablation because I had what is called a v-something response and blood pressure went so low had to go into intensive care for a day to keep up the pressure by giving me the chemical  that causes parkinson's.  dopamine?

My ekg shows prolonged QT intervals which I guess is part of the V.T since  that is included in my diagnosis.  Idiopathic long QT sustained ventricular tachycardia.  I had the supraventricular tachycardia since a teenager but just mostly used avoidance, ice,  and deep breathing for most attacks until the V.T. began in 1978 at 39 years old.  Is it normal for my ekg to continue to show these even though I am taking the medications?.  My other cardiologist never mentioned this..I was.only been told recently from a new doctor.

I do sometimes have irregular heartbeats, but generally they show up as pvc's and unless the runs become too long are not considered a health threat.  When runs are too long, I have shortness of breath.  Since I am now 70 years old and  Norpace is not as safe for the elderly, is there more testing that needs to be done or just leave well enough alone?  I recently had the flu and had a lot of problems with irregular heartbeat and shortness of breath while coughing so much.  I took the Septra, then the doxycycline, but am just starting to recover after four weeks.  I was seven weeks getting over a cold/flu and had the same problems  in 2006/2007 so know this is a problem since getting older.

My first medications for the V.T which was misdiagnosed as just tachycardia was tenormin, but with asthma symthoms had to be discontinued in 1992.   The only other medication that I was able to take was Tambacor and I began that in 1992 when finally got the diagnosis of VT.   I have never had a heart attack, but when I need an antibiotic for infections, I am very limited what I can take by taking these medications and I am allergic to penicillin, cephrasporins, levaquin.  That leaves me with doxycycline and cipro as the only two I can take.  Septra is no longer effective since I had to take it long term for bladder problems. And neither is macrodantin same reason.