The Association of a classical left bundle Branch Block Contraction Pattern by vendor-independent strain echocardiography and outcome after cardiac resynchronization therapy

Background: The association of a Classical left bundle branch block (LBBB) contraction pattern and better outcome after cardiac resynchronization therapy (CRT) has only been studied using vendor-specific software for echocardiographic speckle-tracked longitudinal strain analysis. The purpose of this study was to assess whether a Classical LBBB contraction pattern on longitudinal strain analysis using vendor-independent software is associated with clinical outcome in CRT recipients with LBBB. Methods: This was a retrospective cohort study including CRT recipients with LBBB, heart failure, and left ventricular (LV) ejection fraction ≤35%. Speckle-tracked echocardiographic longitudinal strain analysis was performed retrospectively on echocardiograms using vendor-independent software. The presence of a Classical LBBB contraction pattern was determined by consensus of two readers. The primary end point was a composite of time to death, heart transplantation or LV assist device implantation. Secondary outcome was ≥15% reduction in LV end-systolic volume. Intra- and inter-reader agreement of the longitudinal strain contraction pattern was assessed by calculating Cohen's κ. Results: Of 283 included patients, 113 (40%) were women, mean age was 66 ± 11 years, and 136 (48%) had ischemic heart disease. A Classical LBBB contraction pattern was present in 196 (69%). The unadjusted hazard ratio for reaching the primary end point was 1.93 (95% confidence interval, 1.36-2.76, p &lt; 0.001) when comparing patients without to patients with a Classical LBBB contraction pattern. Adjusted for ischemic heart disease and QRS duration &lt; 150 milliseconds the hazard ratio was 1.65 (95% confidence interval, 1.12-2.43, p = 0.01). Of the 123 (43%) patients with a follow-up echocardiogram, 64 of 85 (75%) of patients with a Classical LBBB contraction pattern compared to 13 of 38 (34%) without, had ≥15% reduction in LV end-systolic volume (p &lt; 0.001). Cohen's κ were 0.86 (95% confidence interval, 0.71-1.00) and 0.42 (95% confidence interval, 0.30-0.54) for intra- and inter-reader agreement, respectively. Conclusion: Using vendor-independent strain software, a Classical LBBB contraction pattern is associated with better outcome in CRT recipients with LBBB, but inter-reader agreement for the classification of contraction pattern is only moderate.</p

Cyclo-oxygenase-2 mediated prostaglandin release regulates blood flow in connective tissue during mechanical loading in humans

Mechanical loading is known to increase connective tissue blood flow of human tendons and to cause local release of vasodilatory substances. The present study investigated the importance of prostaglandins (PG) formed by cyclo-oxygenase isoforms (COX-1 and 2) for the exercise-related increase in blood flow in connective tissue. Healthy individuals (n = 24, age: 23–31 years) underwent 30 min of intermittent, isometric, plantarflexion with both calf muscles either without (n = 6, Control, C) or with blockade of PG formation, either COX-2 specific (n = 10, Celecoxib 2 × 100 mg day(−1) for 3 days prior to the experiment) or COX unspecific (n = 8, indomethacin 100 mg (12 and 1 h pre-experiment) and acetyl salicylic acid 500 mg day(−1) for 3 days pre-experiment). Prostaglandin E(2) (PGE(2)) concentration was determined by microdialysis and blood flow by (133)Xe washout. In C, interstitial PGE(2) rose from (0.8 ± 0.2 (rest) to 1.4 ± 0.5 ng ml(−1) (exercise), P < 0.05), whereas during unspecific COX inhibition, tissue PGE(2) was completely inhibited at rest and during exercise. COX-2 specific blockade did not inhibit tissue PGE(2) at rest, but totally abolished the exercise induced increase. Blood flow was similar in the three groups at rest (P > 0.05), whereas the increase in flow with exercise was reduced by 35 and 43 % with COX-2 specific blockade (3.2 ± 0.7 to 6.1 ± 1.5 ml (100 g tissue)(−1) min(−1) or COX unspecific blockade (3.0 ± 0.8 to 7.6 ± 1.6), respectively, compared to C (2.7 ± 0.8 to 10.2 ± 2.0)(P < 0.05). The findings indicate that COX-2 specific mechanisms are responsible for the exercise-induced increase in prostaglandin synthesis, and that increase in tissue prostaglandin plays an important role for blood flow in peritendinous connective tissue during physical loading in vivo

Measurement properties and performance of an eight-minute submaximal treadmill test in patients with juvenile idiopathic arthritis: a controlled study

Background Poor cardiorespiratory fitness is previously reported in patients with juvenile idiopathic arthritis (JIA) measured both by maximal and submaximal exercise tests, but a submaximal exercise test with acceptable measurement properties is currently lacking for both clinical and research purposes in this patient population. The objectives of this study were to evaluate the measurement properties and performance of a submaximal treadmill test in patients with JIA, and to compare the results with those obtained in controls. Methods Fifty-nine patients (50 girls), aged 10–16 years, with oligo- (n = 30) and polyarticular (n = 29) JIA, and 59 age- and sex-matched controls performed an eight-minute submaximal treadmill test for estimating peak oxygen uptake (VO2peak) followed by a maximal treadmill test measuring VO2peak directly. During the submaximal treadmill test, the study participants walked with no inclination at a speed between 3.2–7.2 km/h for four minutes, and then continued to walk at the same speed for four minutes with five % inclination. VO2peak was directly measured during a continuous graded exercise test on treadmill until exhaustion. Thirty-seven patients participated in the evaluation of the reliability. Criterion validity and reliability were evaluated with interclass correlation coefficient (ICC); measurement errors by Bland-Altman plot, standard error of measurement and smallest detectable change. Results In patients with JIA, the ICC (95% CI) for criterion validity was acceptable at group level 0.71 (0.51, 0.82), but not at individual level. The test-retest reliability and inter-rater reliability were acceptable at individual (0.84 (0.71, 0.91) and 0.92 (0.83, 0.96), respectively) and group levels (0.91 (0.83, 0.96) and 0.96 (0.91, 0.98), respectively). The measurement errors (for test-retest reliability/inter-rater reliability) were large. Bland-Altman plots showed no systematic differences, but a large variability for both the validity and reliability. The performance of and estimated VO2peak from the submaximal test were not associated with disease variables and were comparable between patients and controls. Conclusion The submaximal treadmill test is valid for use in patients with JIA on group level, but not on individual level. The reliability is acceptable. Due to large measurement errors, the submaximal treadmill test is not optimal for use in daily clinical practice to estimate VO2peak in individual patients