Beyond physical exam and laboratory parameters, serial monitoring of weight or data from implantable devices has been used to facilitate remote HF management.  The most common physiologic parameter that we use to monitor HF patients is daily measurements of weight, and most HF longitudinal management programs instruct patients to monitor their weights on a daily basis to track potential changes in fluid status.  (I often give my patients guidance about contacting the HF clinic if their weight exceeds a gain of 2 lb in 2 days or 5 lb in a week.)  The challenge is that the sensitivity of that kind of weight change for anticipating a HF hospitalization, and the specificity of weight change for predicting HF events, is much lower than we would like.

In general, if we look at changes in body weight in anticipation of a HF hospitalization, many patients are admitted to hospital with little or no change in weight, and when there is a change in weight it is often minute, maybe 2–3 lb, not as dramatic as one might expect. If we correlate changes in body weight with changes in filling pressure, using data from implantable hemodynamic monitors, we see that often there are dramatic swings in pressure that anticipate HF events but are not reflected in day-to-day changes in body weight.  So, while weight measurements are not irrelevant to HF management, they are often not a terribly sensitive sign of HF decompensation.^[6-8]  When weight changes do happen, they often happen so proximate to HF events that intervening to prevent a hospitalization is not possible.