The atrioventricular delay of cardiac resynchronization can be optimized hemodynamically during exercise and predicted from resting measurements

BACKGROUND: Atrioventricular (AV) optimization of cardiac resynchronization therapy (CRT) is typically calculated at rest. However, patients often become symptomatic during exercise. OBJECTIVE: In this study, we use acute noninvasive hemodynamics to optimize the AV delay of CRT during exercise and investigate whether this exercise optimum can be predicted from a three-phase resting model. METHODS: In 20 patients with CRT, we adjusted the sensed AV delay while the patient exercised on a treadmill up to a heart rate of 100 bpm to identify the hemodynamically optimal value. Separately, at rest, by pacing with three different configurations and calculating the sensed-paced difference, we calculated an "expected" value for the exercise optimum. RESULTS: It was possible to perform AV delay optimization while a patient exercised. The resting three-phase model correlated well with the actual exercise optimal AV delay (r = 0.85, mean difference +/- standard deviation [SD] = 3.7 +/- 17 ms). Simply using measurements made at rest during atrial-sensed pacing showed a poorer correlation with exercise (r = 0.64, mean difference +/- SD = 2.2 +/- 24 ms). The three-phase resting model allows improved exercise hemodynamics to be achieved. Programming according to the three-phase resting model yields an exercise blood pressure of only 0.5 mmHg (+/-1.4 mmHg; P = NS) less than the true exercise optimum, whereas programming the resting sensed optimum yields an exercise blood pressure of 1.4 mmHg (+/-2.2 mmHg, P = .02) less than the true optimum. CONCLUSIONS: Using acute noninvasive hemodynamics and a protocol of alternations, it is possible to optimize the AV delay of cardiac resynchronization devices even while a patient exercises. In clinical practice, the exercise optimum AV delay could be determined from three phases of resting measurements, without performing exercise.     

Expression of intercellular adhesion molecule 1 (ICAM-1, CD54) in colonic epithelial cells.

The expression of intercellular adhesion molecule-1 (ICAM-1, CD54) was examined in 16 surgically removed colonic tumours and two colonic carcinoma cell lines. Immunohistochemistry showed a varying percentage of ICAM-1 positive colonic carcinoma cells in 9/16 tissue specimens, while normal colonic tissue (apart from a slight reactivity of endothelial cells) was not stained. The presence of the ICAM-1 molecule on the cell surface and the expression of ICAM-1 mRNA were investigated for two colonic carcinoma cell lines. It was possible to enhance the expression of ICAM-1 considerably by incubating the cells in the presence of inflammatory cytokines in HT-29 and CaCo-2 cells. The responsiveness to either interferon alpha (IFN-alpha), tumour necrosis factor alpha (TNF-alpha), or interleukin 1 beta (IL-1 beta) treatment was different in each cell line. Interestingly, ICAM-1 is shed by colonic carcinoma cells because soluble sICAM-1 was detected in the cell culture supernatants. In comparison with normal serum samples, the mean value of sICAM-1 in 63 samples of patients with colonic carcinoma and in 20 cases of active inflammatory bowel disease is raised about twofold. It remains to be clarified what part both forms of ICAM-1 play in the course of colonic cancer, ulcerative colitis, and Crohn's disease.     

Distinct impacts of heart rate and right atrial‐pacing on left atrial mechanical activation and optimal AV delay in CRT

1 Background

Controversy exists regarding how atrial activation mode and heart rate affect optimal atrioventricular (AV) delay in cardiac resynchronization therapy. We studied these questions using high‐reproducibility hemodynamic and echocardiographic measurements.

2 Methods

Twenty patients were hemodynamically optimized using noninvasive beat‐to‐beat blood pressure at rest (62 ± 11 beats/min), during exercise (80 ± 6 beats/min), and at three atrially paced rates: 5, 25, and 45 beats/min above rest, denoted as A_paced,r+5, A_paced,r+25, and A_paced,r+45, respectively. Left atrial myocardial motion and transmitral flow were timed echocardiographically.

3 Results

During atrial sensing, raising heart rate shortened optimal AV delay by 25 ± 6 ms (P < 0.001). During atrial pacing, raising heart rate from A_paced,r+5 to A_paced,r+25 shortened it by 16 ± 6 ms; A_paced,r+45 shortened it 17 ± 6 ms further (P < 0.001). In comparison to atrial‐sensed activation, atrial pacing lengthened optimal AV delay by 76 ± 6 ms (P < 0.0001) at rest, and at ～20 beats/min faster, by 85 ± 7 ms (P < 0.0001), 9 ± 4 ms more (P  =  0.017). Mechanically, atrial pacing delayed left atrial contraction by 63 ± 5 ms at rest and by 73 ± 5 ms (i.e., by 10 ± 5 ms more, P < 0.05) at ～20 beats/min faster. Raising atrial rate by exercise advanced left atrial contraction by 7 ± 2 ms (P  =  0.001). Raising it by atrial pacing did not (P  =  0.2).

4 Conclusions

Hemodynamic optimal AV delay shortens with elevation of heart rate. It lengthens on switching from atrial‐sensed to atrial‐paced at the same rate, and echocardiography shows this sensed‐paced difference in optima results from a sensed‐paced difference in atrial electromechanical delay. The reason for the widening of the sensed‐paced difference in AV optimum may be physiological stimuli (e.g., adrenergic drive) advancing left atrial contraction during exercise but not with fast atrial pacing.     

Indian Asian men have less peripheral arterial disease than European men for equivalent levels of coronary disease

OBJECTIVES: Indian Asians have high rates of heart disease and stroke, but risks of peripheral arterial disease appear to be low. This paradox, and reasons for it, have not been explored. We compared ethnic differences in peripheral arterial disease for a given level of coronary disease. METHODS: We studied 83 European and 84 Indian Asian men with a range of coronary disease. Extent of coronary atheroma was quantified by coronary artery calcification score on multislice CT. Femoral intima-media thickness (IMT) was measured by ultrasound. RESULTS: Femoral IMT was 1.58, 2.06, 2.12, and 2.69 mm in Europeans, and 0.61, 1.41, 1.81 and 2.29 in Indian Asians by increasing categories of coronary atheroma (p=0.003 for ethnic difference, adjusted for age and lumen diameter). Adjustment for smoking and systolic blood pressure, the only risk factors adversely distributed in Europeans, only partly accounted for this ethnic difference (p=0.05). Other risk factors, including lipids, obesity, insulin and glycaemic status, more adversely distributed in Indian Asians, could not account for ethnic differences. Prevalence of abnormal ankle brachial index and lower limb atherosclerotic plaque was also greater in Europeans. CONCLUSIONS: For a given level of coronary disease, Indian Asians have less lower limb atherosclerosis than Europeans, unexplained by established risk factors. Further study of these populations would help tease out relative contributions of risk factors to atherosclerosis in different vessel beds.     

MSCT与微CT在体成像中的对照研究

目的：通过与组织学的对照研究，探讨MSCT和一种新型的μCT系统对评价恶性脑肿瘤体积的诊断准确性。方法：14只小鼠通过立体定向术植入GFP标记的98F一胶质瘤细胞。植入术后第10天所有小鼠行双倍剂量对比增强μCT和MSCT检查。将2种检查方法测量的肿瘤体积与组织病理学结果进行对照分析。     

Retinopathy of prematurity in South Africans at a tertiary hospital: a prospective study

BACKGROUND AND OBJECTIVES: World Health Organization's vision 20/20 programme has recognized retinopathy of prematurity (ROP) as an important cause of childhood blindness in industrialized and middle-income countries. While ROP is virtually nonexistent in many African countries, ROP is seen in urban areas where facilities for neonatal care exist. The aim of this study is to establish the frequency of ROP in a cohort of patients screened for ROP and to establish if current screening criteria apply to our patients. PATIENTS AND METHODS: Infants with birth weight (BW) of 1500 g or less and/or gestational age of 32 weeks or less were screened for ROP over a 2(1/2)-year period by a single examiner. RESULTS: ROP was observed in 84 of 514 (16.3%) of infants included for analysis. Threshold disease (tROP) was noted in 1.6% of the total cohort although 41/84 babies with ROP were lost prior to regression or progression to tROP. Of the 43/84 adequately followed up, eight (18.6%) developed tROP. An estimated frequency of tROP was more likely to be 2.9%. There was no tROP noted in babies of BW greater than 1250 g. Gestational age was an unreliable risk parameter in our population. CONCLUSION: The projected occurrence rate of tROP is similar to that found in black population in the Multicentre Cryotherapy for ROP Trial. Our data suggest that the screening criterion based on BW can safely be lowered to 1250 g in our population.