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School-based COVID-19 vaccine clinics were more likely to vaccinate children who identified as a racial minority, who lacked a regular source of primary care, and who lacked private insurance compared to those vaccinated in non-school-based community locations.

Spatial vectorcardiograms were obtained in five patients with clinical, enzymatic and electrocardiographic evidence of inferior wall myocardial infarction in which the scalar recordings were suggestive of left posterior hemiblock associated with complete right bundle branch block. The frontal plane vectorcardiogram showed abnormal rightward deviation of the maximal QRS vector which could not be attributed to right ventricular hypertrophy, pulmonary disease, extensive lateral myocardial infarct or an extremely vertical heart. Symptomatic A-V block occurred in all cases. The initial 10, 20 and 30 msec were superiorly oriented in two of the four patients with inferior wall myocardial infarction. Wide Q waves in lead aVF were also present. When inferior wall myocardial infarction coexisted with LPH the presence of normal, or small, q waves suggested that the infarction was not transmural, or that an incomplete left bundle branch block or an anteroseptal infarction were present. A-V conduction disturbances appearing in patients with inferior wall myocardial infarction and bifascicular block were of the Wenckebach or Mobitz type. In the former instance the block was in the A-V node; in the latter case it was below the His bundle. The incidence of left posterior hemiblock can be higher than frequently assumed considering that the current criteria, although highly specific, are not sensitive enough.

The effect of increasing heart rate above control sinus rate was investigated in 136 patients with pulmonary emphysema or rheumatic or congenital heart disease. Bipolar right atrial electrode catheter pacing was utilized to increase the atrial rate. At all atrial pacing rates, significant cardiac output increments are noted compared to the outputs during the control sinus rates. The cardiac indices are generally similar at the various atrial pacing rates.

A simplified method for performing retrograde left heart catheterization is described which utilizes a family of preshaped catheters via brachial artery cut-down. A single closed-tip catheter was the sole catheter utilized to accomplish complete left heart studies including coronarv artery cineangiography, ventriculography and aortography in 50 or our last 100 cases. A second, specially shaped, open-tip catheter was used in an additional 46 cases, and a third in four. The aortic valve could be crossed readily, and ventriculography was accomplished with a minimum of premature ventricular contractions. Coronary arteriography could be performed safely with a closed-tip catheter in the majority of our patients. Left heart study with these catheters caused minimal arterial trauma, a low incidence of complications, and shortened catheterization times.

The effect of increasing heart rate above control sinus rate was studied in 33 normal subjects by right atrial bipolar electrode catheter pacing. At all atrial pacing rates, significant cardiac output increments are noted compared to the outputs during the control sinus rate. Further heart rate elevation produced by electrical pacing fails to elevate cardiac output above the levels noted at the lower atrial pacing rates.

The technique of P-wave synchrony utilizing bipolar atrial and ventricular catheters has been employed to determine the variations in cardiac excitability in different phases of the cardiac cycle. In this study, See Image in the PDF File a bipolar intraatrial catheter is used to detect a P-wave which is then transmitted via a Medtronic paired pulse pacemaker to a bipolar ventricular catheter. The stimuli can therefore be applied to the ventricles at various intervals after the P-wave and at various intervals within the cardiac cycle. When the stimulus is applied to the ventricle, shortly after the P-wave, a Wolff- Parkinson-White syndrome results. When the stimulus is applied to the ventricle, within the absolute refractory period, the stimulus is not effective. When the stimulus is applied to the ventricle, during the latter portions of the T-wave, a ventricular rhythm develops with retrograde P-wave conduction. Variations in the strength of the stimulus, as well as in its timing, were utilized in this study to demonstrate that there are considerable variations in cardiac excitability in different portions of the cardiac cycle. Thus, there is an increase in cardiac excitability in the latter portion of diastole, as opposed to early diastole, since the minimum stimulus strength that results in the onset of ventricular pacing is smaller later in diastole and conversely is larger earlier in diastole.

Lowland rivers regularly flood and create complex inundation patterns where energy and matter are exchanged between landscape patches over a dynamic network of surface‐water connections. Scale‐freeness of networks for phenomena in many disciplines have been studied with mixed results. Here we present the first documented example of a (roughly) scale‐free network of surface‐water connections within a river‐floodplain landscape. We accomplish this by simulating 23 inundation maps across the historical range of flows for the Mission River in Texas. We then analyze the topology of the surface‐water connections between the river and two habitat patch types. Results show that surface‐water connectivity is scale‐free for ≥64% of simulated flows (≥70% for flows with floodplain inundation). Moreover, the dynamic surface‐water connections meet five of the six conceptual criteria of scale‐free networks. Our findings indicate that river‐floodplain landscapes are self‐organizing toward scale‐free surface‐water connections among patches that optimizes energy and matter exchange. Rivers that flow over relatively flat landscapes that are formed by their own sediment deposits flood in a manner where river water escapes the confines of the river channel and spills onto the adjacent floodplain. This flooding connects the river to a variety of habitats on the floodplain with the number of connections changing with the size of the river flow. The scale‐free network conceptual model has been used to represent connections and interactions among phenomena within numerous disciplines that include the geophysical, physical, biological, mathematical, engineering, and social sciences. Here we present the first documented example of a pattern of connections between a river and surrounding habitats induced by flooding that resembles the scale‐free network model. We accomplish this by modeling various river flows for Mission River in Texas using specialized computer programs. We then analyze the pattern of connections induced by flooding using specialized statistical methods and computer codes. Our results indicate that most of our modeled river flows create connections that meet five of the six conceptual criteria for scale‐free networks. This indicates that the parts of the river landscape are organizing themselves in a manner that attempts to optimize exchange of energy and matter. Backwater inundation is a major component in the structure and function of river‐floodplain interactionsSurface‐water connectivity creates a dynamic network with a size, configuration, and function indicative of a scale‐free networkChannel and channel‐like features in the river landscape act as hubs that hold together the structure of surface‐water connectivity

Mutual adjustment between process and form shapes the morphology of alluvial river channels, including channel banks. The tops of banks define the transition between the channel and adjacent floodplain, which corresponds to the level of incipient flooding. Despite the geomorphological and hydrological importance of this transition, few, if any, studies have extensively examined spatial variability in bank elevations and its influence on bankfull stage. This study uses an objective method to explore this variability at two spatial resolutions along three alluvial lowland meandering rivers. Results show that variability in bankfull stage is inherent to all three rivers. The mean variability of bankfull stage about the average downstream gradient in this stage is 10% to 20% of mean bankfull depth. Elevations of channel banks exhibit similar variability, even after accounting for systematic variations in heights of inner and outer banks associated with river meandering. Two‐dimensional hydraulic simulations show that the elevation range of mean variability in bankfull stage overlaps considerably with the elevation range of high curvature on rating curves, confirming that variability in bankfull stage influences the shape of these curves. The simulations verify that breaks in channel banks allow flow to extend onto the floodplain at stages below the average bankfull stage. The findings provide fundamental insight into the variable nature of bankfull conditions along meandering rivers and the role of this variability in channel‐floodplain connectivity. The results also inform river‐restoration efforts that seek to re‐establish the natural configuration of channel banks. A lidar‐based methodology reveals inherent variability in bankfull stage and bank elevations for three meandering river channelsMean variation in bankfull stage is 10% to 20% of the average channel depthThe elevation range of mean variation in bankfull stage corresponds to the zone of high curvature in rating curves

1. The acute hemodynamic effects of oral administration of 300 mg of triamterene are reported in a series of 7 normotensive human subjects. 2. Administration of the agent was associated with a decrease in cardiac output, accompanied by a reduction in central venous pressure, insignificantly diminished left ventricular work, and an increase in peripheral vascular resistance. 3. Coronary blood flow was unchanged and myocardial oxygen consumption maintained at the control level whereas calculated cardiac efficiency was reduced.

<$O_ST_ABS>AUTHORS SYNOPSIS<$C_ST_ABS>A sextapolar catheter electrode for temporary sequential atrioventricular pacing on demand was used in 17 patients. Stimulation was performed as desired provided that the catheter tip was properly placed in the right ventricular apex. This catheter will permit wider use of this modality of pacing in those patients who might benefit from it.

<$O_ST_ABS>AUTHORS SYNOPSIS<$C_ST_ABS>Premature atrial stimulation combined with His bundle and local ventricular electrograms was used in three patients to analyse complex AV conduction patterns resulting from variable degrees of delayed or enhanced propagation within the atria, A-V node, and ventricular specialized conducting system. The St₁-St₂ intervals were plotted against the corresponding responses at the low right atrium (LRA), His bundle, intitial site of ventricular depolarization (V), right ventricular apex (RVA), and posterosuperior wall of left ventricle (LV). The electrophysiological effects of a β-blocking agent, Alprenolol, were studied in two patients. This drug, at a dose of 0·2 mg/kg, increased the effective and functional refractory periods of the atria and AV node. In the presence of bifascicular blocks the effective refractory period of the ventricular specialized conducting system was also lengthened. Different grades of functional bilateral bundle branch block were detected in one case. The amount of delay in each bundle branch block could not be determined from the surface leads alone. A supernormal phase of intra-atrial conduction occurred in one patient. These studies extend the usefulness of intracardiac recordings in understanding otherwise complex electrophysiological phenomena in the human heart.