Tuesday, August 31, 2010

Impedance cardiography guided treatment of hypertension

Impedance cardiography (ICG) guided treatment was superior in getting patients to blood pressure goals in this meta-analysis:

Results: Significant benefit was found in both RCTs for ICG-guided BP treatment. The combined odds ratio for the two trials was 2.41 (95% CI = 1.44-4.05, p = 0.0008), in favor of ICG treatment, meaning that it was more than twice as likely to achieve BP success when using ICG than if ICG was not used. Success attainment of goal BP of less than 140/90 mmHg was 67% in the ICG-guided arms of the combined randomized trials. Overall success in the single-arm prospective trials of ICG-guided BP treatment was a similar 68%.

This little noticed paper interests me for a couple of reasons. First, it's one of several papers to come out in just a short time (see yesterday's post on renin profiling) on individualized treatment of hypertension. In hypertension as in many other fields the pendulum appears to be swinging back from one-size-fits-all to pathophysiologic rationale as a guide to treatment.

Second, I became very interested in ICG when I started attending this course in 1981 where I was exposed to the work of the late Robert S. Eliot. ICG was one of the methods Eliot, in collaboration with James C. Buell, MD, used to study the hemodynamic effects of emotional stress. Hemodynamic profiling of hypertension via ICG was a spin-off from this research.

Then in the mid 90s interest in ICG guided antihypertensive therapy fizzled out. ICG was not sexy enough and there was little commercial interest in its development. As the EBM movement gained traction pathophysiologic rationale was frowned upon and one-size-fits-all became the guiding principle. But now that we're on the cusp of a new era of individualized medicine ICG guided treatment may be poised for comeback.

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