Reduction of Blood Pressure Levels Study Group
To the Editor:
Smith et al1 reported that office blood pressure (BP) was lower in subjects whose antihypertensive therapy was guided by noninvasive hemodynamics (impedance cardiography) than in subjects receiving standard care. The study, thus, documents that measurements by impedance cardiography are clinically useful.
Unfortunately, in the study, there was no measurement of home or ambulatory BP. Because both physicians and patients were aware of the use of hemodynamically guided treatment, expectation bias on the part of both physician and patient could clearly have affected office readings. A measure of home or ambulatory BP was, therefore, absolutely needed, and it is surprising that it was not included in the study design.
This trial should have been the definitive study for the clinical usefulness of impedance cardiography in managing hypertension. Without home or ambulatory monitoring, it cannot be considered definitive.