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Impedance cardiography (BioZ)

Definition

BioZ provides a non-invasive measurement of the function of the heart and blood vessels, including:

  • Cardiac output: The blood volume pumped by the heart with each cycle.
  • Systemic vascular resistance: The resistance to blood flow offered by blood vessels.
  • Fluid status: The total amount of fluids in the body.

Blood pressure is determined by the balance between two factors:

  • The volume of blood pumped by the heart per minute, or the cardiac output.
  • The ability of the blood vessels to dilate to accommodate the needs of your body, or systemic vascular resistance.

Alternative names

BioZ

Why the test is performed

By measuring and monitoring the cardiac output, as well as systemic vascular resistance with BioZ, treatment of hypertension can be precisely individualized.

This is particularly useful in the treatment of:

  • Resistant hypertension: In a study done by the Mayo Clinic, using BioZ helped attain good blood pressure control in 60% more patients than in patients treated by conventional measures.
  • Intolerance to blood pressure medications: It has been shown that using BioZ over anti-hypertensive agents results in faster blood pressure control with fewer medications.
  • Fluid overload: BioZ gives us a measure of the fluid content and the cardiac output. This gives us the ability to optimize cardiac function and carefully measure the effect of diuretic therapy. 

Risks

Previously, determining heart function involved pulmonary artery catheterization, where a small catheter is advanced from an artery in the groin all the way to the heart and pulmonary vessels. This is an invasive test which has rare but serious complications and is expensive and complex. BioZ is completely safe, non-invasive and does not have any serious risks or adverse consequences.

How the test is performed

The test takes approximately 5-10 minutes to perform and is painless. Four BioZ sensors are placed on the patient's neck and chest and a very small electrical signal is transmitted through the chest. The signal is then analyzed and provides physicians with data that includes the amount of blood the heart pumps each minute, the resistance it has to work against and the amount of fluid in the chest. 

After the test

When the patient returns, these measurements are transferred to a computer where they can be easily viewed and documented in a report. 

Outlook (Prognosis)

This test can be used to predict which medications will work best to control their blood pressure.

References/Citations

  1. Taler SJ. Individualizing antihypertensive combination therapies: clinical and hemodynamic considerations. Curr Hypertens Rep. 2014 Jul;16(7):451. doi: 10.1007/s11906-014-0451-y. Review. PubMed PMID: 24806735; PubMed Central PMCID: PMC4138599.
  2. Siedlecka J, Siedlecki P, Bortkiewicz A. Impedance cardiography - Old method, new opportunities. Part I. Clinical applications. Int J Occup Med Environ Health. 2015;28(1):27-33. doi: 10.13075/ijomeh.1896.00451. Review. PubMed PMID: 26159944.
  3. Krzesiński P, Gielerak G, Stańczyk A, Piotrowicz K, Uziębło-Życzkowska B, Banak M, Kurpaska M, Michalczyk Ł, Jurek A, Wolszczak K, Galas A, Wójcik A, Skrobowski A. The effect of hemodynamically-guided hypotensive therapy in one-year observation - randomized, prospective and controlled trial (FINEPATH study). Cardiol J. 2016 Feb 15. doi: 10.5603/CJ.a2016.0009. [Epub ahead of print] PubMed PMID: 26876066.
  4. Krzesiński P, Gielerak G, Stańczyk A, Piotrowicz K, Skrobowski A. Who benefits more from hemodynamically guided hypotensive therapy? The experience from two randomized, prospective and controlled trials. Ther Adv Cardiovasc Dis. 2016 Feb;10(1):21-9. doi: 10.1177/1753944715618593. Epub 2015 Dec 2. PubMed PMID: 26634615.