Assessment of papillary muscle function in the intact heart.

Abstract

A technique is described to localize the anterolateral papillary muscle and to assess its performance in vivo. Using this technique, we measured sequentially the pressure generated within the anterolateral papillary muscle and its changes in length during the cardiac cycle in eight open-chest anesthetized dogs. Pressure within the anterolateral papillary muscle was THE PAPILLARY MUSCLE has been largely used as a convenient sample of myocardium for the assessment of the mechanical and biochemical properties of the heart. 1 2However, limited and conflicting descriptions have been given of the normal function of the papillary muscle in the intact heart.3-' Measurements with straingauge arches applied directly to the surface of the papillary muscle showed that tension within the papillary muscle developed well after the rise of intraventricular pressure.7 On the other hand, tension in a single chorda tendinae was reported to parallel left ventricular isovolumic pressure development.8 On the basis of cineangiograms of metal clips on the mitral valve, some investigators concluded that the papillary muscle contracts isometrically.3 Others, who evaluated metal clips sewn on the surface of the papillary muscle, found a 22.8% shortening during systole.4The availability of miniature probes that produce minimal alterations at the site of measurement has made it possible to assess, in vivo, not only the intra- mural pressure generated within the papillary muscle but also its changes in length. The purpose of this investigation was to describe a technique for the assessment of the performance of the papillary muscle in vivo by measuring the pressure within the papillary muscle and its changes in length throughout the cardiac cycle. MethodsLocalization of the anterolateral papillary muscle. The anterolateral papillary muscle was localized in the intact heart by means of a modified Millar micromanometer needle probe.9 In 12 open-chest dogs (not included in this report), while the pressure sensor was pushed across the anterior cardiac wall to measure intramyocardial pressure at various depths, a pressure was recorded that was twice or more that of left ventricular pressure. Careful dissection in these dogs consistently showed that the pressure sensor was located within the anterolateral papillary muscle. On the basis of these observations, we used the pressure probe as a tool to localize the anterolateral papillary muscle in the intact heart.The pressure transducer was inserted perpendicular to the epicardium, 1.5 to 2 cm deep into the anterolateral wall of the left ventricle, in the area between the first diagonal branch of the left anterior descending coronary artery and the first marginal branch of the left circumflex coronary artery, halfway between the atrioventricular ring and the apex. Intramyocardial pressure was continuously measured during the insertion and compared with left ventricular pressure. When the systolic intramyocardial pressure was at least twice that of left ventricular intracavitary systolic pr...

Papillary Muscles Do Not Attach Directly to the Solid Heart Wall

“…In addition, a slight delay after initiation of contraction by the ventricular wall before contraction by the PMs, as has been observed experimentally in some studies, might enable the AV valve leaflets to close more freely before tension builds up in the PMs. 9 The small additional conduction time required for the activation wave front to reach the PMs, imposed by a somewhat more circuitous path through the trabeculae rather than directly from the wall, could provide such a short delay.…”

Assessment of Atrioventricular Valve Anatomy and Function in Congenital Heart Diseases Using Three-Dimensional Echocardiography

“…To cope with the force on the leaflets, the papillary muscles generate tension and shorten during systole so as not to cause prolapse of the leaflets. The contraction and shortening of papillary muscle occurs as follows: isometric contraction of the papillary muscle coincides with isovolumic contraction of the ventricle, and the shortening of the papillary muscle begins at the early ejection phase and continues throughout the ejection phase and also during the isovolumic relaxation phase [30]. Although the contraction of the papillary muscle is important for normal AVV function, the position of the papillary muscles has been elucidated as an even more crucial factor for AVV function through enthusiastic investigations of functional mitral regurgitation in adults after myocardial infarction.…”