Angiographic validation of eigenvolume to measure left ventricular size

Area of Science:

• Cardiovascular physiology
• Biomedical engineering
• Diagnostic imaging

Background:

• Radiopaque markers enable tracking myocardial motion and calculating relative left ventricular volume (eigenvolume).
• Previous in vitro validation using balloons in excised dog hearts showed a non-zero intercept, partially supporting the eigenvolume theory.
• Eigenvolume is hypothesized to be directly proportional to true left ventricular cavity volume.

Purpose of the Study:

• To compare eigenvolume with left ventricular volume measured by biplane angiography in intact beating hearts.
• To validate the accuracy of eigenvolume as a measure of left ventricular volume in vivo.
• To assess the immediate effects of angiography on left ventricular volumes.

Main Methods:

• Implantation of radiopaque markers in the left ventricle of five dogs.
• Measurement of left ventricular volume using biplane angiography.
• Hemodynamic interventions including atropine, phenylephrine, nitroprusside, volume loading, and propranolol.
• Comparison of calculated eigenvolumes with angiographically determined left ventricular volumes.

Main Results:

• A high correlation (r = 0.958 ± 0.029 SD) was observed between eigenvolumes and left ventricular volumes.
• The intercept between eigenvolume and angiographically measured left ventricular volume was not significantly different from zero, aligning with theoretical predictions.
• Angiography-induced left ventricular volume loading resulted in a modest 6% increase in end-diastolic and end-systolic eigenvolumes without altering stroke volume or pressures.

Conclusions:

• Eigenvolume accurately reflects true left ventricular volume in vivo, strengthening the eigenvolume theory.
• The in vivo validation overcomes limitations of previous in vitro studies.
• Angiography itself has a minor, transient effect on left ventricular volumes, suggesting a mild negative inotropic effect.