An optical device to measure the dynamics of apex rotation of the left ventricle

Abstract

Systolic counterclockwise rotation of the left ventricular apex with respect to the base has been defined as left ventricular (LV) twist or torsion. If rotation of the base during systole is small, we hypothesized that the dynamics of twist can be well characterized through the measurement of apical rotation alone. A device was designed to measure apical rotation in a simpler, more direct fashion, providing continuous high-fidelity dynamic measurements. The device consists of a light source, a position-sensitive diode, and a small rotating mirror that is coupled to the apex of the heart by a wire. As the wire rotates, apical rotation (measured in degrees) can be calculated from the position of the deflected light beam. The timing of apical rotation was compared with simultaneous recordings of electrocardiogram, LV pressure, and LV diameter measurements. An initial clockwise rotation (untwist) of 4 +/- 2 degrees (SD) occurred during isovolumic contraction followed by counterclockwise rotation (twisting) through ejection, reaching maximum apical rotation of -15 degrees just before the end of systole. Rapid untwisting during isovolumic relaxation was shown with near-complete dissipation of twist by the first one-third of the diastolic filling period. Caval occlusion caused a downward and leftward shift of the pressure-apical rotation loops, and more twist/untwist was seen to occur during the respective isovolumic contraction and relaxation periods. We conclude that this device provides precise timing and definition of rapid changes during isovolumic contraction and relaxation, confirms results obtained by more laborious methods, and provides an easy method to measure the dynamics of apical rotation continuously during interventions such as load changes.

Increased left ventricular twist, untwisting rates, and suction maintain global diastolic function during passive heat stress in humans

“…The maintenance of early diastolic blood and tissue velocities, as well as circumferential and diastolic strain rates, given the significant volume unloading suggests that the ventricular contribution to early diastolic function is augmented with passive heating. Our results therefore suggest that the increased LV untwisting rate, which is strongly associated with increased recoil and LV suction (9,12,19,24,25,30), is responsible for maintaining early diastolic function, counteracting the effects of the reduction in left atrial volume and, likely, filling pressures.…”

“…recoil is regarded as an important contributor to LV suction (12,19,24,25,30), with the greatest portion of LV pressure decay occurring during the isovolumic relaxation period. We propose that, despite a marked reduction in left atrial volume with HS, augmented LV untwisting is responsible for maintaining the forces that drive early filling in the present experiment, as observed via the maintained filling velocities, tissue velocities, and strain rates.…”

Left Ventricular Torsion in Patients With Secundum Atrial Septal Defect

“…Some studies have indicated that the basal LV rotation is minimal and not important, 13,20 but in patients with aortic stenosis, a reduced magnitude of the basal rotation compared with normal hearts has been observed. 23,33 Furthermore, in patients with chronic heart failure, an improvement in LVEF was associated with an increase in basal rotation, but not at the apex, after 6 months of medical therapy, 24 indicating that the basal rotation may be clinically relevant.…”

“…[8][9][10] Recently, assessment of LV rotation has become an important approach for quantifying LV function. [11][12][13][14][15][16][17][18][19][20][21][22][23][24] However, to the best of our knowledge there are no data available to date on the impact of RV volume overload on LV twist in patients with ASD. The recent development of 2-dimensional (D) ultrasound speckle tracking imaging (STI) has allowed LV torsional deformation to be evaluated noninvasively with validation against sonomicrometry and tagged magnetic resonance imaging (MRI).…”

Left Ventricular Form and Function Revisited: Applied Translational Science to Cardiovascular Ultrasound Imaging

“…During isovolumic contraction, predominant shortening of the subendocardial fibers and stretching of the subepicardial fibers result in a brief clockwise rotation of the apex (right-handed helix rotation directed along subendocardial fiber direction) (41,48,49) (Fig. 4A).…”