@vjs003 I've had a long history of tachycardia- SVT, occurred rarely when I was younger but got more frequent and longer as I got into my 50's ( I'm 79 now). I was started on metoprolol after a long bout of SVT with a heart rate of around 200 took me to the ER where they slowed it down with an adenosine IV, continued with digoxin over the next 12 hours to get the heart rate back to normal. I continued with the metoprolol which did a great job of controlling the tachycardia for the next 17-18 years or so, if there was bradycardia I wasn't aware of it then and we never picked it up during doc's visits. After that was when the bradycardia ( heart rates in the 40's) set in, intermittent and asymptomatic at first, but it got worse and was symptomatic over the next couple years, and I started having more breakthroughs of tachycardia as well.
My cardiologist increased the metoprolol to 150 mg/day to control the tachycardia, but as one might figure that also contributed to the bradycardia. I was referred to the electrophysiologist, who diagnosed me with sick sinus syndrome ( tachy-brady type). They were talking pacemaker, but first wanted to see if my getting off metoprolol might correct the bradycardia, so that is when I weaned off the metoprolol as described in my last post. I still needed a medication to control the tachycardia, so diltiazem was substituted for the metoprolol, in the hopes that this drug could control the tachy without the side effects of bradycardia. The diltiazem did virtually nothing for the tachy, and I still had the bradycardia, so that's when we opted for a pacemaker.
I don't know if the EP would have just tried to keep me on higher doses of diltiazem to try and control the tachy after the pacemaker was placed, but I begged him to let me start taking the metoprolol again- even a low dose of it along with the diltiazem, and he agreed. I took 50 mg metoprolol with 180 mg diltiazem ER for a year or two after the pacemaker implant. After that, my cardiologist ( the EP had left the practice and I was transferred back to my old cardiologist) increased the metoprolol, first to 100 mg/day, then 150 mg/day after my remote monitoring pacemaker reports showed an increase in tachy/arrhythmia episodes, some of which were A-fib. He discontinued the diltiazem ( he hates diltiazem, don't know why) so now I take the 150 mg/day of the metoprolol, which for the most part keeps my heart rate under control. I still get some breakthroughs of both SVT and A-fib, but mostly they are short lived and not every day. He's instructed me that in the event of a longer episode of A-fib, or SVT, to take an extra 50 mg of metoprolol, they really don't want to increase my regular dosage more than the 150 mg/day I already take.
My calcium and magnesium levels are fine- the calcium is checked twice a year with routine labs, and magnesium occasionally, but it's been fine too.
I'd have to say that at least in my case, metoprolol has been my go-to drug to control the SVT, and the A-fib as well- no side effects that I can determine, and I feel better when I take it. I think one of the reasons it works for me is that I also have high blood pressure ( well controlled now) so the metoprolol doesn't drop my blood pressure too low as it does many people with normal, or low blood pressure. The metoprolol probably did at least contribute over time to my bradycardia over time, not the direct cause but it likely uncovered an underlying problem with the sick sinus syndrome that I already had- this according to the two EP's and the cardiologist I've seen over the years.
That's me- as they say, others' mileage may vary, in regards to metoprolol!