Heterogeneity of Red Blood Cell Velocity in Skeletal Muscle Decreases with Increased Flow

Objective: Effective material exchange between blood and tissue depends on the heterogeneity of microvascular flow. The objective was to address inconsistencies between intravital studies regarding this dependency. We tested the hypothesis that heterogeneity of red blood cell velocity (V_RBC) in capillary beds varies with the strength of metabolic stimulus and with capillary bed geometry. Methods: We used videomicroscopy to measure V_RBC in a bed of 10–24 capillaries at the surface of extensor digitorum longus (EDL) muscle in anesthetized rats. The coefficient of variation (CV = standard deviation/mean; an index of spatial heterogeneity) was computed in the same bed before and after (i) 1, 2, 4, or 8 Hz supramaximal muscle contraction or (ii) adenosine superfusion (10^?7–10^?3 M). Beds with or without arteriolar—venular capillary shunts were used. Results: Although control V_RBC differed between beds (shunt: 232 μm/s; no shunt: 130 μm/s), the percentage increases in postcontraction V_RBC did not (range: 111–326%). In both beds, control CV varied greatly (overall range: 28–117%) and 2–8 Hz muscle contractions reduced CV significantly by 25%. Similar results were obtained for adenosine. In confirmatory experiments using the rat cremaster muscle, contractions (4 Hz) and adenosine (10^?4 M) also reduced CV. Based on all data, CV = 63–0.022 V_RBC (r = 0.82, P < 0.001). Conclusions: The heterogeneity of V_RBC decreased with metabolic stress, regardless of capillary bed geometry. We propose that both the large variability in control CV and the relatively shallow dependence of CV on velocity could be responsible for the present inconsistencies between intravital studies.     

Demonstration of the Feasibility of Implantation of a Skeletal Muscle Pulse Generator for Fecal Incontinence in a Patient with an Implanted Unipolar DDD Pacemaker

Electromagnetic fields and myopotentials from skeletal muscle may interfere with the function of a cardiac pacemaker. A 65-year-old woman with a unipolar DDD cardiac pacemaker underwent dynamic graciloplasty (transposition of the gracilis muscle around the anal canal and subsequent implantation of a bipolar pulse generator to stimulate the gracilis muscle), for the treatment of fecal incontinence. This gracilis pulse generator is turned "off" with an external magnet to allow defecation. Appropriate functioning of these two pulse generators (the cardiac pacemaker and the gracilis pulse generator) was tested during implantation of the gracilis pulse generator and afterwards. It was demonstrated that the combination could be used safely in this patient.     

High sensitivity cardiac troponin T and interleukin‐6 predict adverse cardiovascular events and mortality in anticoagulated patients with atrial fibrillation

Summary. There are limited data on the prognostic role of biomarkers in anticoagulated patients with atrial fibrillation (AF). We evaluated the prognostic value of high sensitivity TnT (hsTnT) and high‐sensitivity interleukin‐6 (hsIL6) in a large cohort of AF patients taking oral anticoagulant therapy (OAC) as both biomarkers have been associated with adverse cardiovascular events. Methods: We studied 930 patients (51% male; median age 76) with permanent/ paroxysmal AF who were stabilized (for at least 6 months) on OAC (INRs 2.0–3.0). Plasma hsTnT and hsIL6 levels were quantified by electrochemiluminescense immunoassay at baseline. Patients were followed‐up for up to 2 years, and adverse events (thrombotic and vascular events, mortality and major bleeding) were recorded. Results: At follow‐up, 96 patients (3.97%/year) died whilst 107 had an adverse cardiovascular event (3.14%/year). On multivariate analysis, high hsTnT and high hsIL6 remained significantly associated with prognosis even after adjusting for CHADS₂ score: HR 2.21 (1.46–3.35, P < 0.001) for high hsTnT and 1.97 (1.29–3.02, P = 0.002) for high hsIL6, for adverse cardiovascular events. For all‐cause mortality, the HRs were 1.79 (1.13–2.83, P = 0.013) and 2.48 (1.60–3.85, P < 0.001), respectively. The integrated discrimination index (IDI) values of clinical scores (CHADS₂ and CHA₂DS₂‐VASc) were improved by the addition of hsTnT and/or hsIL6 (all P < 0.05). Conclusion: In a large ‘real world’ cohort of anticoagulated AF patients, both hsTnT and hsIL6 levels provided prognostic information that was complementary to clinical risk scores for prediction of long‐term cardiovascular events and death, suggesting that these biomarkers may potentially be used to refine clinical risk stratification in AF.     

Fetal volume blood flow and umbilical artery flow velocity waveform analysis: a comparison

Summary. The estimation of fetal umbilical vein and aortic volume blood flow was compared with umbilical artery flow velocity-time waveform analysis in 42 pregnancies. The volume blood flow measurements were made with a combined linear array B-mode and pulsed Doppler ultrasound system. The umbilical artery flow velocity-time waveform analysis was made with either pulsed or continuous wave 2 MH_zDoppler ultrasound and the systolic/diastolic (A/B) ratio was used as an index of flow resistance. There was no difference when continuous wave was compared to pulsed Doppler ultrasound as a method of recording flow velocity waveforms. Analysis of the umbilical artery flow velocity-time waveform was more sensitive (100%-50%) than the measurement of umbilical vein volume blood flow (ml/kg/min) in the detection of the small-for-gestational age (SGA) fetus. The predictive value of a positive test was higher (71%-45%) while specificity was similar (88%-81%). Descending aortic volume flow was reduced in only one SGA fetus. The increase in umbilical placental downstream resistance (high systolic/ diastolic ratio) was associated with a reduction in the percentage of fetal aortic blood flow directed to the umbilical placental circulation.     

Merits of Various Antipacemaker Circus Movement Tachycardia Features

Pacemaker circus movement tachycardia (PCMT) was a significant problem in first generations of DDD pacemakers. Programmability of the atrial refractory period proved to he an elective tool to prevent PCMT except in patients with very long ventriculoatrial (V-A) conduction intervals, because a long atrial refractory period severely limits the maximum tracking rate. In these patients, extension of the atrial refractory period after a VPB, bipolar atrial sensing, adaptation of atrial refractory period to atrial rate, and VPB synchronous atrial stimulation helped limit the incidence of PCMT. Rate smoothing and fallback behavior have given rise to other forms of PCMT. Once initiated, PCMT can be terminated by a single P wave or by means of an appropriately timed atrial stimulus. Recognition by means of continued upper rate pacing may not be helpful in patients with a long V-A conduction interval because their PCMT rate will be low, thus requiring a low upper rate to trigger. Therefore, (1) absolute prevention of PCMT has not yet been achieved, but PCMT is no longer a significant problem in DDD pacing; (2) recognition of PCMT should not be related to the ventricular upper rate limit.     

Feto-Maternal Circulatory Changes Related to Placenta Morphology in Diabetes Mellitus

Combined real-time Doppler ultrasound blood flow measurements were carried out in 20 diabetic pregnant women in the third trimester. The placenta morphology was examined with emphasis on maturation, centrocotyledon hemorrhage, villous edema, and ischemia, ischemic villitis, infarction, perivillous fibrin deposition, thrombosis, and inflammatory changes of membranes and fetal placental vessels. Ten out of 17 cases with placenta pathology had normal blood flow measurements. Centrocotyledon hemorrhage (n = 8) was associated with a higher pulsatility index in the fetal aorta and development of fetal distress and obstetric intervention in labor. The higher number of hemorrhages, the greater the risk of intervention. The pulsatility index was normal in the umbilical artery. The uterine artery pulsatility index showed no correlation to the hemorrhages. Ischemic villitis and infarction were not found in any placenta, suggesting that there were no cases of advanced placental dysfunction. Placental immaturity, found in 11 cases, was not associated with any flow anomalies. Centrocotyledon hemorrhage seemed to be the earliest morphological abnormality affecting blood flow in the feto-maternal circulation in diabetic pregnancy. Centrocotyledon hemorrhage might be the first sign of placental microflow disturbance, possibly affecting fetal oxygenation, but not the total placental vascular bed resistance.     

ADENOMYOEPITHELIOMA OF THE BREAST

Adenomyoepithelioma is a rare disorder characterised by simultaneous proliferation of ductal epithelium and myoepithelial cells. It is more common in salivary glands or skin, and only rarely found in breast tissue. Adenomyoepithelioma of the breast was first described in 1970 by Hamperl.¹ Since then, approximately 55 cases have been described in the literature; the largest review, by Tavassoli in 1991, reported 27 of these cases.² Because of the small number of cases reported, the natural history of adenomyoepithelioma of the breast remains uncertain. We report a further case which was treated by local excision, and follow-up for two years has revealed no evidence of local recurrence or metastatic spread.     

Programming a Long Paced Atrioventricular Interval May Be Risky in DDDR Pacing

In patients with intermittent AV block and dual chamber pacemakers, a long paced AV interval of 200 msec or more can be selected to prolong pulse generator life (by avoiding the ventricular pace output) and to enable a more physiological and hemodynamically superior activation sequence. This case report describes the potential risks of programming a long paced AV interval in a patient with a DDDR pacemaker. T wave pacing, as described here, can occur if the conducted QRS complex is not sensed because it occurs during the ventricular blanking period (delivery of the atrial stimulus). This can be initiated by the mechanisms that induce apparent and actual P wave undersensing of the conducted QRS complex. In this case report apparent P wave undersensing and subsequent T wave pacing with ventricular capture (in a patient with intermittent AV block) occurred frequently during an exercise test done in the DDDR mode with a paced AV interval of 200 msec, according to the clinical evaluation protocol.