Chemo is very tough medicine. If you read through the literature an oncologist should give you, the potential side effects are alarming. Many don't happen. But chemo can have an effect on the heart, as can herceptin. It's also true that many people may not be aware of latent weaknesses or potential trouble spots before a cancer diagnosis. My bone density for example was very good, but did I know before staring femara? Not a clue. My arrythmia is probably partly attributable to chemo, but not exclusively. Because a bout of tachycardia was pretty obvious before a chemo treatment, it was quickly picked up and my heart health (mostly good) is known and monitored. A thorough check after active treatment may be a good idea for all of us, even though more tests may be the last thing we want.
