Archive for the ‘Cardiology’ Category

Transvenous Reservoir Catheter Mimicking Right Atrial Mass Lesion

Feb 28, 2015 Author: Walter Mcneil | Filed under: Cardiology

Mass lesions of the right atrium are usually detected by two-dimensional echocardiography. These are tumors, primary or metastatic, thrombi, vegetations, foreign bodies, such as pacemaker wires or obvious indwelling transvenous catheters. Artifacts produced by using high echocar-diographic gain settings, diaphramatic hernia, and ruptured sinus of Valsalva aneurysm may also mimic right atrial mass. We would like to add to the above list reservoir catheters (Mediport, Hickman, Omaya) in the superior vena cava and right atrium. These catheters are not easily detected because the implant sites are not obvious, and furthermore, they are not attached to external intravenous device. (more…)

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  • Can Maximal Cardiopulmonary Capacity be Recognized by a Plateau in Oxygen Uptake: ConclusionThe ramp treadmill protocol employed in the present study may offer several advantages for cardiopulmonary assessment. It has been suggested that an optimal test duration, determined by individualized work increments that yield the highest oxygen uptake, is approximately ten minutes in duration. Redwood and coworkers demonstrated that tests which use large work increments in patients with angina resulted in reductions in exercise capacity and poor reliability for studying the effects of therapy. Standardized protocols that are commonly used clinically employ large and/or unequal work increments resulting in a nonlinear relation between oxygen uptake and work rate. A number of investigators have therefore described the importance of adapting the exercise test to the subject and purpose of the test. Thus, the ability to individualize ramp rates to reproduce exercise capacity, a given myocardial oxygen demand, the onset of angina, or other symptoms when evaluating interventions is provocative. A simple computer prograin was developed for the present study, from which ramp rates were individualized resulting in good reproducibility and a test duration of approximately 9.1 ±1 minute. (more…)

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  • An important observation made from the present data was the variability in the slope of the change in oxygen uptake throughout progressive exercise, despite a constant, consistent change in external work and the use of large, averaged samples. A slope, in the present context, is defined as the change in oxygen uptake for a given sample associated with a unit change in external work. Thus, a slope not different from zero at peak exercise suggests that oxygen uptake was not increasing concomitantly with external work. The degree of variability observed would appear to preclude the determination of a plateau by common definitions. It should also be noted that a plateau was not a consistent finding with repeated testing, even though maximal heart rate, perceived exertion, and maximal gas exchange parameters did not differ between days. The variability demonstrated during each test and the lack of consistency of the slopes on different days suggests that the occurrence of a plateau may be random. Reading here (more…)

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  • Can Maximal Cardiopulmonary Capacity be Recognized by a Plateau in Oxygen Uptake: ResultsDifferences between measurements made on day 1 and day 2 of heart rate, gas exchange, and perceptual responses are presented in Table 1. The slope of the change in oxygen uptake for subject 1 on day 1 and day 2 are illustrated in Figures 2 and 3, respectively. The mean maximal oxygen uptake of the subjects was 50.0 ± 11.7 ml/kg/min on day 1 and 49.6 ± 11 ml/ kg/min on day 2. This difference was not significant (NS). Accordingly, treadmill time was not different between day 1 (9.0 ± 1.4 minutes) and day 2 (9.3 ± 1.2 minutes). The mean maximal perceived exertion was 19.8 ±0.4 and 20 ±0 on days 1 and 2, respectively (NS), and the mean maximal respiratory exchange ratios were 1.30±0.10 and 1.24±0.12 on days 1 and 2, respectively (NS). These values are consistent with maximal effort on both days. (more…)

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  • Five healthy male subjects and one healthy female subject (mean [ ± SD] age, 33 ± 6 years) participated in the study. None was taking any medication or had any remarkable medical history. All had at least average fitness; the mean (± SD) maximal oxygen uptake was 50.0 ± 12 ml Vkg/min. further
    Exercise Testing
    Maximal exercise tests were performed using a ramp treadmill protocol, ie> using a constant, continuous change in external work. Initially, an exercise test was performed to familiarize subjects with the procedure and to determine maximal oxygen uptake. Using this information, treadmill ramp rates were individualized to attain a test duration of approximately ten minutes. The same ramp rate, time of day, and laboratory conditions were employed for a given subject on day 2, and tests were performed a mean of 15 ±8 days apart. Ramp rates ranged between 1.2 and 7.0 ml Oj/kg/min, with a mean of 4.0 ±2 ml (Vkg/min, expressed as change in external work. The software and hardware used to perform these tests were developed by the Burdick Corporation (Milton, Wis). Exercise was continued to volitional fatigue and subjects were encouraged to give a maximal effort. The Borg 6 to 20 scale was used to quantify effort. (more…)

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  • Can Maximal Cardiopulmonary Capacity be Recognized by a Plateau in Oxygen Uptake?Technologic advances have greatly improved the precision with which gas exchange measurements are used to evaluate the physiologic response to exercise testing. These advances, however, have raised a number of uncertainties concerning the interpretation of data. For example, disagreement exists regarding the recognition of maximal cardiorespiratory limits. It is often assumed that this limit has been attained when oxygen uptake no longer increases concomitantly with increasing work (oxygen uptake plateau). However, automated systems that have become common allow variations in data sampling that can greatly affect the interpretation of maximal exercise. this (more…)

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  • DISCUSSION (part 3)

    The benefit of the combined effects of class I and class III properties was first discussed by Hondeghem and Snyders . Conduction velocity and ERP determine the maximal tachycardia rate of a reentry arrhythmia. Although action potential duration is an important parameter of the ERP, the availability of the sodium currents is also a major concern. Recovery from sodium channel block occurs primarily at negative potentials and, therefore, starts mainly after repolarization. Hence, its contribution to lengthening of refractoriness is added to that resulting from prolongation of the action potential duration.


    The effects of D-sotalol on the spontaneous sinus rate have been attributed not to calcium antagonistic efficacy, but to prolongation of the pacemaker cell action potential duration . The more marked negative chronotropic action of tedisamil would suggest that there was an additional effect on the calcium-dependent pacemaker currents, but an only minor influence on AV nodal refractoriness did not support this. A lack of effects on the calcium currents was also described by Dukes and Morad and by Adaikan et al . The slight effects of sotalol and tedisamil on the AV node may therefore only be explainable by a minor prolongation of the action potential in the AV node region. One remarkable difference between tedisamil and D-sotalol is the prolongation of His bundle and intraventricular conduction and the marked prolongation of atrial myocardial refractoriness by high concentrations of tedisamil. These findings indicate a direct effect of tedisamil on the sodium currents of the myocardium, which is in agreement with the data of Dukes and Morad and of Abraham et al . A further difference between the drugs was found to be a significantly higher prolongation of the JT interval by tedisamil, indicating a more potent effect on the potassium channels. (more…)



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