Quantitative Analyses of the Left Ventricle Volume and Cardiac Function in Normal and Infarcted Yucatan Minipigs

Area of Science:

• Cardiovascular Imaging
• Cardiac Anatomy
• Medical Imaging Quantification

Background:

• Accurate left ventricular volume (LVV) and contractility assessment using cardiac magnetic resonance imaging (CMRI) is crucial for disease modeling.
• Enlarged papillary muscles, common in conditions like hypertrophic cardiomyopathy, can decrease the accuracy of standard CMRI measurements in human and animal models.
• Standard CMRI methods may not adequately account for the significant contribution of papillary muscles to overall cardiac mass and volume.

Purpose of the Study:

• To establish the optimal method for left ventricular volume (LVV) quantification using cardiac magnetic resonance imaging (CMRI) in pigs.
• To compare the accuracy of standard versus a detailed LVV measurement technique in Yucatan minipigs.
• To determine the impact of papillary muscle inclusion on LVV and ejection fraction (EF) calculations in CMRI.

Main Methods:

• Left ventricular volume (LVV) was measured in 29 Yucatan minipig hearts using two CMRI techniques: a standard method and a detailed method.
• The standard method involved smooth endocardial contouring, excluding papillary muscles from the ventricular cavity volume.
• The detailed method traced papillary muscles and trabeculations, incorporating them into the ventricular mass calculation for more accurate LVV assessment.

Main Results:

• Papillary muscles constitute approximately 21% of the left ventricular (LV) mass in Yucatan minipigs, impacting CMRI accuracy.
• The detailed CMRI method, including papillary muscles, showed significantly higher ejection fraction (EF) measurements: 11% higher in normal hearts and 19% higher in infarcted hearts compared to the standard method.
• LVV and LV mass measurements were significantly affected by the inclusion or exclusion of papillary muscles (p < 0.001), with the detailed method aligning closely with ex vivo LV mass.

Conclusions:

• The detailed CMRI method, accounting for papillary muscles, provides superior accuracy and interobserver consistency for assessing LV mass and EF in pigs.
• This detailed approach is recommended for more precise cardiac function analysis in pig models, especially those mimicking human cardiac diseases.
• Accurate quantification of LVV and EF using CMRI in preclinical models requires careful consideration and inclusion of cardiac structures like papillary muscles.