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Left Ventricular Untwisting Is an Important Determinant of Early Diastolic Function

Andrew T. Burns, MB, BS (Hons), BMedSci, MD^_*,_*, Andre La Gerche, MB, BS^_*, David L. Prior, MBBS, PhD^_*,, Andrew I. MacIsaac, MBBS, MD^_*,

^_* Cardiac Investigation Unit, St. Vincent's Hospital Melbourne, Victoria, Australia
University of Melbourne Department of Medicine, St. Vincent's Hospital Melbourne, Victoria, Australia

^_* Reprint requests and correspondence: Dr. Andrew T. Burns, Cardiac Investigation Unit, St. Vincent's Hospital, Melbourne, PO Box 2900, Fitzroy, Victoria, Australia, 3065 (Email: andrew.burns{at}svhm.org.au).

Objectives: We sought to establish the relationship between invasive measures of diastolic function and untwisting parameters measured with speckle tracking imaging.

Background: Left ventricular (LV) diastolic function is determined by early diastolic relaxation (which creates suction gradients for LV filling) and myocardial stiffness. Assessment of LV torsion has shown that untwisting begins before aortic valve closure and, in animals, might be an important component of normal diastolic filling. Studies in human subjects using indirect indexes derived from right heart catheterization have suggested a relationship between and measures of untwisting, but the relationship between directly measured diastolic function indexes with micromanometer catheters and untwisting parameters has not been established in human subjects.

Methods: Simultaneous Millar micromanometer LV pressure and echocardiographic assessment was performed on 18 patients (10 male, mean age 66 years) with normal systolic function and a spectrum of diastolic function. Invasive rate of the rise of LV pressure, dp/dt minimum and were recorded as measures of active relaxation, and the LV minimum diastolic pressure was recorded as an index of diastolic suction. The LV stiffness constant and functional chamber stiffness were estimated from hybrid pressure-volume loops. Echocardiographic speckle tracking imaging was used to quantify torsion.

Results: As relaxation was impaired, (prolonged ) untwisting was delayed (r = 0.35, p < 0.01). There were nonsignificant associations between reduced untwisting and longer values of and lower dp/dt minimum. Reduction in the extent of untwisting before mitral valve opening was associated with increased LV minimum diastolic pressure (r = –0.30, p < 0.034). No relation was observed between the LV stiffness constant (β: r = 0.11, p = NS) or the functional LV chamber stiffness (b: r = 0.11, p = NS) and untwisting.

Conclusions: Untwisting parameters are related to invasive indexes of LV relaxation and suction but not to LV stiffness. These data suggest that untwisting is an important component of early diastolic LV filling but not later diastolic events.

Key Words: diastole • echocardiography • speckle tracking imaging • torsion • untwisting

Abbreviations and Acronyms   dp/dt = rate of the rise of left ventricular pressure   GTN = glyceryl trinitrate   IVRT = isovolumic relaxation time   LA = left atrial   LV = left ventricle/ventricular   MVO = mitral valve opening   STI = speckle tracking imaging

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