Citations

There is very little data addressing cartilage response to tensile forces, and no literature attempts to correlate compressive with tensile modalities. Our hypothesis was that the cyclic compression and tension modulate chondrocyte matrix proteoglycan synthetic response differently. Porcine chondrocytes cultured to confluence on a flexible membrane were subjected to cyclic compression (Group A: 13 KPa at 1 Hz) or tension (Group C: 10% strain at 1 Hz) for 16 or 32 h; while controls not subjected to any force were kept (Group B). The chondrocytes were then stained with alcian blue and stained areas quantified with confocal microscopy and image processing software. Two-factor ANOVA with post-hoc tests (Scheffe and Bonferroni) statistical analysis were used. Proteoglycan staining covered 46% (range 28%–61%) and 39% (range 26%–49%) of the surface area following 32 and 16 h of compression respectively, 23% (range 15%–49%) for control, and 19% (range 10%–29%) and 16% (range 9%–25%) following 16 and 32 h tension respectively. Proteoglycan content following all compressions was significantly greater than with cyclic tension or control (p < 0.0001). Our data demonstrate that chondrocytes cultured in vitro respond to compression distinctly different from tension and that it is highly sensitive to mechanical loading, with rapid adaptation to its mechanical environment. These results imply that cartilage grown in culture, with the intention of transplantation, may structurally benefit from an environment of cyclic loading at higher frequencies.

Background— Little is known about what treatments patients receive after being diagnosed with stable coronary artery disease or what the comparative outcomes are for routine medical treatment (RMT) versus percutaneous coronary intervention (PCI) with RMT for patients in a setting apart from randomized controlled trials. Methods and Results— Patients with stable coronary artery disease undergoing cardiac catheterization in New York State between 2003 and 2008 were followed up to determine the treatment they received. Patients receiving RMT and patients receiving PCI with RMT were propensity matched through the use of 20 factors that could have a bearing on outcomes. The resulting cohort of 933 matched pairs was used to compare mortality/myocardial infarction (MI), mortality, MI, and subsequent revascularization rates. A total of 89% of all patients underwent PCI with RMT. PCI/RMT patients had significantly lower adverse outcome rates at 4 years for mortality/MI (16.5% versus 21.2%; P =0.003), mortality (10.2% versus 14.5%; P =0.02), MI (8.0% versus 11.3%; P =0.007), and subsequent revascularization (24.1% versus 29.1%; P =0.005). Adjusted RMT versus (PCI with RMT) hazard ratios were 1.49 (95% confidence interval, 1.16–1.93) for mortality/MI and 1.46 (95% confidence interval, 1.08–1.97) for mortality. There were no differences for patients ≤65 years of age or for patients with single-vessel disease. Conclusions— Most patients with stable coronary artery disease in New York undergoing catheterization between 2003 and 2008 received PCI. Patients who received PCI experienced lower mortality, mortality/MI, and revascularization rates. The reasons for this finding need to be better understood, including the possible role of low medication adherence rates that have been found in other studies.

Blood flow and vasodilatory responses are altered by age in a number of vascular beds, including the cerebral circulation. To test the role of prostaglandins as regulators of cerebral vascular function, we examined cerebral vasodilator responses to CO2 (cerebrovascular reactivity) in young (26 ± 5 yr; 6 males/6 females) and older (65 ± 6 yr, 5 males/5 females) healthy humans before and after cyclooxygenase inhibition (using indomethacin). Middle cerebral artery velocity (MCAv) responses to stepped hypercapnia were measured before and 90 min after indomethacin. Changes in MCAv during the recovery from hypercapnia (vasoconstrictor responses) were also evaluated before and after indomethacin. Cerebrovascular reactivity was calculated using linear regression between MCAv and end-tidal CO2. Young adults demonstrated greater MCAv (55 ± 6 vs. 39 ± 5 cm/s: P < 0.05) and MCAv reactivity (1.67 ± 0.20 vs. 1.09 ± 0.19 cm·s−1·mmHg−1; P < 0.05) to hypercapnia compared with older adults ( P < 0.05). In both groups MCAv and MCAv reactivity decreased between control and indomethacin. Furthermore, the age-related differences in these cerebrovascular variables were abolished by indomethacin. During the recovery from hypercapnia, there were no age-related differences in MCAv reactivity; however, indomethacin significantly reduced the MCAv reactivity in both groups. Taken together, these results suggest that cerebral blood flow velocity and cerebrovascular reactivity are attenuated in aging humans, and may be due to a loss of prostaglandin-mediated vasodilation.

Background: Medial elbow injuries are common among baseball pitchers. Easily accessed methods to assess medial elbow stress may be useful in identifying individuals with increased injury risk. Hypothesis: Pitch velocity (PV) is positively associated with higher medial elbow adduction moments. Study Design: Cohort study; Level of evidence, 2. Methods: Participants included 26 uninjured high school pitchers, 15 to 18 years in age. Three-dimensional data and PV were collected as athletes threw 10 fastballs for strikes to a regulation-distance target. Variables of interest were the normalized peak internal elbow adduction moment and peak PV. Linear regression was performed to evaluate the influence of PV on the adduction moment. Results: For the group, mean PV was 71 mph (range, 58-81 mph), and the adduction moment was 0.558 Nm/Ht × mass (range, 0.378-0.723). PV was positively associated with the adduction moment ( P < 0.01, R 2 = 0.373). Conclusions: Talented young pitchers may be more susceptible to elbow injuries as a consequence of a biomechanical coupling between PV and upper extremity joint moments. Clinical Relevance: PV may be measured easily and serve as an indicator of medial elbow stress.

Abstract Aims For patients with refractory atrial fibrillation (AF) undergoing atrioventricular nodal ablation (AVNA), initial single-chamber right ventricular (RV)-only pacing is standard. Given the deleterious effects of chronic RV-only pacing, the impact of an initial biventricular (BiV) pacing strategy post-ablation is of interest. Methods and results We conducted a meta-analysis to determine the effect of BiV vs. RV-only pacing in patients undergoing AVNA for refractory atrial fibrillation. A search of multiple electronic databases identified 921 reports, which included four randomized controlled trials (n = 534). Mean New York Heart Association (NYHA) class was 2.3 and mean left ventricular ejection fraction (LVEF) was 44%. When compared with RV-only pacing, BiV pacing was not associated with reduced mortality [risk ratio 0.85, 95% confidence interval (CI) 0.40–1.82, P = 0.68]. In three studies comprised of patients with left ventricular systolic dysfunction (mean EF 41 ± 3%), BiV pacing demonstrated a non-significant reduction in cardiac mortality (risk ratio 0.59, 95% CI 0.25–1.39; P = 0.23). Compared with RV-only pacing, BiV pacing was associated with significant improvement in symptoms [Minnesota Living with Heart Failure Questionnaire (MLWHFQ) 2.72 points fewer, 95% CI 1.45–3.99] and increased LVEF (+2.6%, 95% CI 1.69–3.44), but no significant change in 6 min walk distance (6MWD) (5.02 ms more, 95% CI −1.56 to 11.59; P = 0.13). Conclusions In patients with refractory AF undergoing AVNA, BiV pacing was not associated with significantly improved survival when compared with RV-only pacing. A modest, but significant improvement in structural and functional response to BiV pacing was observed.