Thousands of ladies take Tamoxifen around the world with no sides at all. Some cardiologists are giving it to men as well and with good results. If cardiac conduction problems are an issue then it would have been made very clear by now.
I really would not worry about what you have read. If it does happen it is so rare that it isn't even listed as a side in the PDR.
The only good way to keep total serum cholesterol down and especially HDL up while "on" 17 aa roids and especially estrogen inhibitors is to substitute an estrogen in the liver. Both Clomid and nolva act as estrogens in the liver and it is this estrogen that is protective.
Bill Roberts has had good results from using clomid during a cycle for this reason.
If you decide to stay away from Nolvadex and are really concerned with hdl and total cholesterol then do not use ANY 17aa roids or any estrogen inhibitors. Colmid could be your other choice though but clomid and Nolvadex are almost exactly the same.
As you probably already know the following dietary changes can help with the hdl/ldl issue.........avoid trans fatty acids, that is ALL cooking oils except cold pressed olive oil and a little butter. Margine is loaded with trans fats. Eat plenty of omega 6 and especailly omega 3 oils ie: salmon, tuna and oil supplements. Never fry anything with butter or olive oil above 250 degree F.
Avoid saturated fat like the plague(animal fat)
Avoid anything that has partially hydrogenated oil or vegetable oil shortening(trans fats)
Limit total cholesterol intake although saturated fat is way worse.