Wall stress measured before and after ventriculectomy

Background. Opinions are divided about the long-term effect of volume-reduc tion surgery as described by R. Batista. The concept of volume-reduction su rgery (VRS) refers to Laplace's law assuming that any given reduction in ve ntricular diameter reduces wall stress by a calculable extent. However, we doubted this approach as it does not take into account intricacies in the v entricular wall structure. Methods. In 17 patients we measured the tension within the myocardial meshw ork by inserting needle force probes into up to five sites of the left vent ricular anterior and diaphragmatic wall before and after resection of the i nterpapillary segment. The latter was investigated for its connective tissu e content. Results. In 66 measuring sites local mesh-tension dropped a mean 40 +/- 22% . In eight other sites however, mesh-tension increased a mean 38 +/- 19%. H istology from the resected segments (mean weight 58.2 +/- 22.9 g) showed an inhomogeneous repartition and alignment of connective tissue. The mean col lagen content (hydroxyproline) was 31.7 +/- 21% ranging from 19 to 59%. Conclusion. Disparities in wall stress seem to be related to disparities in the content and alignment of collagen in a tangential and/or oblique trans mural direction A predominantly radial alignment jeopardizes systolic freed om of motion because it hinders systolic wall thickening. Tangential collag en alignment hampers diastolic ventricular compliance. A dense spatial coll agen network impairs systolic and diastolic function. The impact of connect ive tissue on any individual heart must be assessed preoperatively by follo wing a dosed ventricular loading and unloading protocol. The heart's potenc y to shrink and its ability to increase wall thickness during systole serve s as a strong patient selection criteria to predict the outcome of VRS.