Fixed-apex mitral annular descent correlates better with left ventricular systolic function than does free-apex left ventricular long-axis shortening

A novel whole "Joint-in-Motion" device reveals a permissive effect of high glucose levels and mechanical stress on joint destruction

OBJECTIVE

Osteoarthritis (OA) has recently been suggested to be associated with diabetes. However, this association often disappears when accounting for body mass index (BMI), suggesting that mechanical stress may be a confounding factor. We investigated the combined influence of glucose level and loading stress on OA progression using a novel whole joint-in-motion (JM) culture system.

DESIGN

Whole mouse knee joints were placed in an enclosed chamber with culture media and actuated to recapitulate leg movement, with a dynamic stress regimen of 0.5 Hz, 8 h/day for 7 days. These joints were treated with varying levels of glucose and controlled for osmolarity and diffusion. Joint movement and joint space were examined by X-ray fluoroscopy and microCT. Cartilage matrix levels were quantified by blinded Mankin scoring and immunohistochemistry.

RESULTS

Culturing in the JM device facilitated proper leg extension and flexion movements, and adequate mass transport for analyzing the effect of glucose on cartilage. Treatment with higher levels of glucose either via media supplementation or intra-articular injection caused a significant decrease in levels of glycosaminoglycan (GAG) and an increase in aggrecan neoepitope in articular cartilage, but only under dynamic stress. Additionally, collagen II level was slightly reduced by high glucose levels.

CONCLUSIONS

High levels of glucose and dynamic stress have permissive effects on articular cartilage GAG loss and aggrecan degradation, implicating that mechanical stress confounds the association of diabetes with OA. The JM device supports novel investigation of mechanical stress on the integrity of an intact living mouse joint to provide insights into OA pathogenesis.

"Frozen Apex" Repair of a Dilated Cardiomyopathy

We try to make surgical ventricular restoration simpler and more adjustable to safely enhance ventricular function. In eight patients with DiDonato type III dilated cardiomyopathy, we applied a few short-axis purse-string sutures to the endocardial side of the left ventricular apex ("Frozen-Apex" restoration) to make a smaller, cone-shaped apex, based on the concept that the left ventricular apex is important in its existence, but not in its function. The procedure took less than 15 minutes in all the patients. There was no hospital or late death with the follow-up of 549 ± 389 days. Mid-late postoperatively, New York Heart Association functional class changed from 3.5 ± 0.8 (preoperative) to 1.6 ± 0.6 (P = 0.000 vs preoperative), left ventricular diastolic diameter from 64 ± 16 to 61 ± 15 mm, systolic diameter from 57 ± 15 to 50 ± 17mm (P = 0.070), ejection fraction from 27 ± 10 to 40 ± 16% (P = 0.014). Diastolic function as assessed by the ratio of the early to late ventricular filling velocities, the ratio of mitral annular early diastolic velocity to early mitral inflow velocity, and estimated right ventricular pressure remained at the similar level to preoperative one. The new ventricular restoration was associated with better systolic left ventricular function without deteriorating diastolic one. It may improve the outcome of the treatment of selected patients with dilated cardiomyopathy.

Reduction of left ventricular longitudinal global and segmental systolic functions in patients with hypertrophic cardiomyopathy: Study of two-dimensional tissue motion annular displacement

The early detection of abnormal left ventricular systolic functions in patients with hypertrophic cardiomyopathy (HCM) remains a challenge. The aim of this study was to identify a novel method for the assessment of left ventricular systolic function in patients with HCM. A total of 65 patients with HCM were included in this study. The patients were divided into obstructive HCM (HOCM; 16 cases) and non-obstructive HCM (NOHCM; 49 cases) groups. The healthy control group comprised 48 participants. Two-dimensional (2D) speckle-tracking technology was used to measure the left ventricular global and segmental longitudinal strains and mitral annular displacement (MADs). Compared with healthy control group, the six segmental strains and the global strain of the left ventricle (LS_global) increased while six segmental MADs and MAD_global of the mitral annulus decreased in the HOCM and NOHCM groups (P<0.05). In addition, the six segmental MADs of the mitral annulus were significantly negatively correlated with the six segmental strains of the left ventricle (r=−0.744 to −0.647, P<0.001). MAD_global was significantly negatively correlated with LS_global (r=−0.857, P<0.001). The tissue motion annular displacement (TMAD) at the midpoint was significantly negatively correlated with LS_global (r=−0.871, P<0.001). The 2D TMAD technique of measuring MAD was feasible and practically approachable for rapidly evaluating the left ventricular longitudinal global and segmental systolic functions of patients with HCM.

Contribution of mitral annular dynamics to LV diastolic filling with alteration in preload and inotropic state

Mitral annular (MA) excursion during diastole encompasses a volume that is part of total left ventricular (LV) filling volume (LVFV). Altered excursion or area variation of the MA due to changes in preload or inotropic state could affect LV filling. We hypothesized that changes in LV preload and inotropic state would not alter the contribution of MA dynamics to LVFV. Six sheep underwent marker implantation in the LV wall and around the MA. After 7–10 days, biplane fluoroscopy was used to obtain three-dimensional marker dynamics from sedated, closed-chest animals during control conditions, inotropic augmentation with calcium (Ca), preload reduction with nitroprusside (N), and vena caval occlusion (VCO). The contribution of MA dynamics to total LVFV was assessed using volume estimates based on multiple tetrahedra defined by the three-dimensional marker positions. Neither the absolute nor the relative contribution of MA dynamics to LVFV changed with Ca or N, although MA area decreased (Ca, P < 0.01; and N, P < 0.05) and excursion increased (Ca, P < 0.01). During VCO, the absolute contribution of MA dynamics to LVFV decreased ( P < 0.001), based on a reduction in both area ( P < 0.001) and excursion ( P < 0.01), but the relative contribution to LVFV increased from 18 ± 4 to 45 ± 13% ( P < 0.001). Thus MA dynamics contribute substantially to LV diastolic filling. Although MA excursion and mean area change with moderate preload reduction and inotropic augmentation, the contribution of MA dynamics to total LVFV is constant with sizeable magnitude. With marked preload reduction (VCO), the contribution of MA dynamics to LVFV becomes even more important.

Atrioventricular plane displacement is the major contributor to left ventricular pumping in healthy adults, athletes, and patients with dilated cardiomyopathy

Previous studies using echocardiography in healthy subjects have reported conflicting data regarding the percentage of the stroke volume (SV) of the left ventricle (LV) resulting from longitudinal and radial function, respectively. Therefore, the aim was to quantify the percentage of SV explained by longitudinal atrioventricular plane displacement (AVPD) in controls, athletes, and patients with decreased LV function due to dilated cardiomyopathy (DCM). Twelve healthy subjects, 12 elite triathletes, and 12 patients with DCM and ejection fraction below 30% were examined by cine magnetic resonance imaging. AVPD and SV were measured in long- and short-axis images, respectively. The percentage of the SV explained by longitudinal function (SVAVPD%) was calculated as the mean epicardial area of the largest short-axis slices in end diastole multiplied by the AVPD and divided by the SV. SV was higher in athletes [140 ± 4 ml (mean ± SE), P = 0.009] and lower in patients (72 ± 7 ml, P < 0.001) when compared with controls (116 ± 6 ml). AVPD was similar in athletes (17 ± 1 mm, P = 0.45) and lower in patients (7 ± 1 mm, P < 0.001) when compared with controls (16 ± 0 mm). SVAVPD%was similar both in athletes (57 ± 2%, P = 0.51) and in patients (67 ± 4%, P = 0.24) when compared with controls (60 ± 2%). In conclusion, longitudinal AVPD is the primary contributor to LV pumping and accounts for ∼60% of the SV. Although AVPD is less than half in patients with DCM when compared with controls and athletes, the contribution of AVPD to LV function is maintained, which can be explained by the larger short-axis area in DCM.