Chronic Heart Failure.
Chronic heart failure is by definition a cardiac index of less than 2.4 litres per minute per square metre of body surface area, or 2.4 L/min/m2. The aim of treatment in cardiac failure is to produce a cardiac index greater than 2.4 L/min/m2. We know from the previous pages that cardiac output depends on preload, myocardial contractility, and afterload. The USCOM can guide us in manipulating each of these parameters individually, as well as showing us the overall outcome - the CO and CI. What's more, the USCOM can do this for both the right and the left ventricles independently, allowing us to optimize hemodynamics whichever side of the heart is the limiting factor.
Again, if we consider the management of cardiac failure in primary care and even hospital practice, it is very often done by guesswork. The patient simply describes how they feel since they commenced upon the new medication, be it digoxin, a diuretic, an ACE inhibitor or ?-blocker. From the patient's description of their lifestyle, we try to guess whether their cardiac output has increased as result of our therapy. If we were to treat hypertension without ever measuring the patient's blood pressure we would probably be regarded as being negligent, yet we treat patients with cardiac failure on a daily basis without ever measuring the outcome of our treatment. Sure, echocardiography can give some guidance, but how practical is it to perform echocardiography several times over a couple of months whilst we tailor our therapy to the patient’s needs? Even then, echocardiography doesn’t tell us the one thing we really need to know, the cardiac index.
The USCOM now brings a rational basis to prescribing in chronic cardiac failure. It takes all the guesswork out of the clinical situation. Simply measure the patient’s cardiac index, modify the medication, remeasure the cardiac index. Did the change in medication help? If not then review it again. Hemodynamics is not rocket science.
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Hypertension
