DEAR DR. ROACH: I’m an 88-year-old female who has been diagnosed with ventricular fibrillation (VFib). My cardiac electrophysiologist, who implanted a conventional pacemaker four years ago, has noticed several episodes of VFib (up to 30 seconds, read via a bedside monitor). They recommend replacing the current pacemaker with a combo pacemaker and defibrillator. I wonder about the history/success of this device. — C.R.

ANSWER: Most people have heard about atrial fibrillation (AFib), which is a common, chaotic electrical condition of the top chambers of the heart. Without regular electrical input from the atria to the ventricles, the ventricles beat irregularly, but blood flow from the heart still remains adequate. By contrast, VFib is a chaotic movement of the lower chambers, and the heart does not pump blood during VFib.

Within a short time, 10 to 30 seconds at most, the brain will not have enough oxygen to keep you conscious. Unless VFib is rapidly treated or stops by itself (which is rare, but happened to you), VFib is fatal.

A survivor of VFib definitely benefits from an automatic implantable cardioverter-defibrillator (AICD). Nowadays, they also have the ability to act as a pacemaker; they recognize and immediately provide a shock during episodes of VFib.

AICDs first became available when I was in medical school during the 1980s, but current models are a huge improvement since they are smaller and last longer. The evidence is strong that people at a high risk for a “malignant” arrythmia like VFib live longer with an AICD than those who are only treated with anti-arrhythmic drugs. The rate of sudden cardiac death is reduced by about 50%. You are very lucky and should get this recommended device as soon as possible. They are common and effective.

Don’t ignore thyroxine levels

DEAR DR. ROACH: Last year, my thyroxine (T4) level was abnormally high (12.2 mcg/dL). I ignored it, as it was slightly over the normal range of 4.5-12 mcg/dL. Six months later, it increased to 12.4 mcg/dL. Should I be concerned? My thyroid-stimulating hormone (TSH) level was normal both times. — J.M.

ANSWER: Although many people with abnormal blood results are perfectly healthy, the more abnormal a test result is, the more likely it represents something wrong.

In your case, you are correct that the readings are just outside of the normal range. But because it is persistent, it’s worthwhile to get additional information.

Most importantly, were you having symptoms that made your doctor concerned about whether you might have a thyroid issue? Many people with high levels of thyroxine have excess energy, sweating, weight loss, tremors, anxiety and heat intolerance.

Next, do you have any other tests that might help support or reject the possibility of thyroid disease? In your case, it’s the TSH level. A high TSH level means that your body needs more thyroid hormone, whereas excess production of thyroid hormone from the gland usually leads to a low TSH level. Your TSH level is normal, which is strong evidence that the slightly high T4 level might be typical for you, especially if you don’t have any symptoms.