Left ventricular dynamic geometry and diastolic mechanics in a model of chronic XXXX and right ventricular pressure overload.

@entity235 @entity26 @entity848
Left ventricular (LV) mechanics and dynamic geometry were studied in eight @entity235 1 to 151 days after creation of a model of @entity848 and increased right ventricular (RV) pressure. In each @entity235 , an 8 mm conduit was interposed between the main pulmonary artery and left atrium; the pulmonary artery was then banded distal to this shunt. Ultrasonic dimension transducers were subsequently implanted for the measurement of LV equatorial minor axis and wall thickness. Catheter-tipped micromanometers were used to measure LV and pleural pressures; RV pressure was measured with a fluid-filled catheter and an external transducer. Eight control animals were similarly instrumented. At the time of study, the cyanotic @entity235 had significantly decreased arterial @entity26 saturations (66% +/- 7% versus controls: 96% +/- 5%), significantly elevated peak RV pressures, (55 +/- 7 mm Hg versus controls: 30 +/- 5 mm Hg) and significantly elevated ratios of RV to LV mass (0.52 +/- 0.05 versus controls: 0.36 +/- 0.05). Diastolic pressure-dimension curves were generated and time constant for LV relaxation were calculated for each animal. The diastolic curves obtained from the cyanotic @entity235 were not significantly different from those of the control animals, and LV relaxation was not prolonged in the cyanotic @entity235 . In the three @entity235 that were cyanotic for 4 months or longer, there was a profound abnormality in the geometric pattern of LV contraction, manifested by asynchronous shortening of the anteroposterior equatorial minor axis. In two of these three @entity235 , inotropic reserves were assessed by means of postextrasystolic potentiation and were found to be normal. The results of this study indicate that short-term mild @entity848 and RV pressure overload do not alter diastolic compliance nor prolong relaxation of the LV. LV dynamic geometry may become abnormal after 4 months, with preservation of global LV inotropic reserves.
