Admittance‐based pressure–volume loop measurements in a porcine model of chronic myocardial infarction

• Published in: Experimental physiology 2013-11, Vol.98 (11), p.1565-1575
• Main Authors: van Hout, G. P. J., de Jong, R., Vrijenhoek, J. E. P., Timmers, L., Duckers, H. J., Hoefer, I. E.
• Format: Article
• Language: English
• Subjects: Animals; Echocardiography, Three-Dimensional - methods; Electric Conductivity; Female; Heart - physiopathology; Models, Animal; Myocardial Infarction - diagnostic imaging; Myocardial Infarction - physiopathology; Swine; Ventricular Dysfunction, Left - diagnostic imaging; Ventricular Dysfunction, Left - physiopathology; Ventricular Function, Left - physiology
• ISSN: 0958-0670; 1469-445X
• DOI: 10.1113/expphysiol.2013.074179

New Findings •  What is the central question of this study? Are admittance‐based pressure–volume measurements useful for the assessment of cardiac function in a chronic myocardial infarction model compared with three‐dimensional echocardiography and with classical conductance measurements? •  What is the main finding and its importance? Baseline admittance‐based measurements show good agreement with echocardiography and classical conductance in human‐sized porcine hearts. Myocardial infarction significantly alters ventricular dimensions and pressure–volume loop measurements compared with three‐dimensional echocardiography. The novel admittance system reliably monitors changes in cardiac function after myocardial infarction. The aim of this study was to validate admittance‐based pressure–volume (PV) loop measurements for the assessment of cardiac function in a porcine model of chronic myocardial infarction. The traditional PV loop measurement technique requires hypertonic saline injections for parallel conductance correction prior to signal conversion into volume. Furthermore, it assumes a linear relationship between conductance and volume. More recently, an admittance‐based technique has been developed, which continuously measures parallel conductance and uses a non‐linear equation for volume calculation. This technique has not yet been evaluated in a large‐animal model of myocardial ischaemia. Eleven pigs underwent invasive PV measurements with the admittance system (AS) and the traditional conductance system followed by three‐dimensional echocardiography (3DE). After baseline measurements, pigs were subjected to 90 min left anterior descending coronary artery occlusion, followed by the same measurements at 8 weeks follow‐up. In the healthy heart, the AS showed good agreement with 3DE for left ventricular volumes and a reasonable correlation for ejection fraction (r= 0.756, P= 0.007). At follow‐up, an increase in end‐systolic volume was observed with 3DE (+15.4 ± 14.4 ml, P= 0.005) and the AS (+34.6 ± 36.1 ml, P= 0.010). The ejection fraction measured with 3DE (−13.2 ± 5.2%, P < 0.001) and the AS (−20.3 ± 11.2%, P < 0.001) significantly decreased. We conclude that the AS can be used for quantitative monitoring of changes in cardiac function induced by myocardial infarction and provides comparable results to 3DE, rendering it a useful tool for functional testing in large‐animal cardiac models.