Improving methods of chordal sparing mitral valve replacement. Part I: A new, non-distorting isovolumic balloon preparation for the left ventricle with intact mitral subvalvular apparatus

Background and aims of the study: The conventional isovolumic preparation with a single balloon, although employed for many years, distorts the chordae tendineae of the intact mitral apparatus. Material and methods: Anterior balloon (one balloon inserted via a slit in the anterior leaflet) and double balloon (two balloons through slits in both leaflets) methods were developed and compared to the conventional method and natural conditions (LV filled with saline, or 'gold standard') in six ex-vivo, non-beating porcine hearts. Results: LV volumes measured by the double balloon, anterior balloon, and conventional techniques all correlated highly with natural conditions, but the conventional method had a lower correlation coefficient (r = 0.99, 0.98, p < 0.0001 and < 0.001; and 0.92 p < 0.01, respectively at a left ventricular (LV) pressure of 50 mmHg, while r = 1.00, 1.00, both p < 0.0001; and 0.92, p < 0.01, respectively at 70 mmHg). Epicardial echocardiography revealed that the double balloon technique filled the space behind the chordae while maintaining normal chordal geometry, but the anterior balloon alone did not (p < 0.001). Similarly, the conventional method did not fill the LV outflow tract (p < 0.001) and had a mitral annular shift toward the left atrium (p < 0.001). Photography of both leaflets showed that only the double balloon method maintained normal geometry as assessed by leaflet length ratio; the other methods produced distorted geometry I compared to natural filling conditions. Conclusions: With an intact mitral valve, the double balloon method provides more precise LV pressure-volume measurements while preserving the normal geometry of the chordae tendineae and mitral annulus.