Validation of Peripheral Pressure Volume Loops and Ultrasound-derived "Cardiac Power" by Comparison With Invasive Left Ventricular Pressure Volume Loops

Extensive animal work by Suga et al. in the 1980s clearly demonstrate a relationship between
left ventricular pressure volume area (PVA) and myocardial consumption of oxygen (MVO2).

PVA can be measured by combining radial artery pressures with ultrasound-derived estimates
of aortic blood flow. Because the aorta and peripheral artery compartments are separated
from the left ventricle by the aortic valve, the peripheral arterial pressures cannot
perfectly approximate left ventricular pressures. However, because the majority of
variation in the pressure volume loops is made up of changes in height and width (changes in
the left ventricular end-diastolic curve are, by contrast, relatively small), both of which
can be readily detected by changes in the peripheral arterial blood pressure tracing, this
loss of information may be clinically insignificant.

USCOM, has developed a portable suprasternal Doppler probe (model 1A) capable of estimating
left ventricular stroke volume; a unique feature of this device is its ability to utilize
both stroke volume, heart rate, and mean arterial pressure in an attempt to measure cardiac
power. This device has not been validated against invasive estimates of cardiac power.

Knowledge of MVO2 would be a useful clinical variable but is not widely available. The
ability to non-invasively estimate MVO2 intraoperatively would give anesthesiologists the
ability to measure the effect of hemodynamic interventions on myocardial consumption of
oxygen and, when combined with stroke volume, estimate myocardial efficiency.
Non-invasively estimates of MVO2 may also allow cardiologists a novel means of assessing the
myocardium of patients with cardiovascular disease.

Inclusion Criteria:

- Adult (18 or older)

- Undergoing left heart catheterization

Exclusion Criteria:

- Unable to visualize ascending aorta using ultrasound