Limit on stably trapped particle fluxes determined theoretically and compared with data from Explorer satellites

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Limit on stably trapped particle fluxes

Background The leading cause of death in patients hospitalized for acute myocardial infarction is cardiogenic shock. We conducted a randomized trial to evaluate early revascularization in patients with cardiogenic shock. Methods Patients with shock due to left ventricular failure complicating myocardial infarction were randomly assigned to emergency revascularization (152 patients) or initial medical stabilization (150 patients). Revascularization was accomplished by either coronary-artery bypass grafting or angioplasty. Intraaortic balloon counterpulsation was performed in 86 percent of the patients in both groups. The primary end point was mortality from all causes at 30 days. Six-month survival was a secondary end point. Results The mean (+/-SD) age of the patients was 66+/-10 years, 32 percent were women, and 55 percent had been transferred from other hospitals. The median time to the onset of shock was 5.6 hours after infarction, and most infarcts were anterior in location. Ninety-seven percent of the patients assigned to revascularization underwent early coronary angiography, and 87 percent underwent revascularization; only 2.7 percent of the patients assigned to medical therapy crossed over to early revascularization without clinical indication. Overall mortality at 30 days did not differ significantly between the revascularization and medical-therapy groups (46.7 percent and 56.0 percent, respectively; difference, -9.3 percent; 95 percent confidence interval for the difference, -20.5 to 1.9 percent; P = 0.11). Six-month mortality was lower in the revascularization group than in the medical-therapy group (50.3 percent vs. 63.1 percent, P=0.027). Conclusions In patients with cardiogenic shock, emergency revascularization did not significantly reduce overall mortality at 30 days. However, after six months there was a significant survival benefit. Early revascularization should be strongly considered for patients with acute myocardial infarction complicated by cardiogenic shock. (N Engl J Med 1999;341:625-34.) (C) 1999, Massachusetts Medical Society.

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Early Revascularization in Acute Myocardial Infarction Complicated by Cardiogenic Shock

1999 update: ACC/AHA guidelines for the management of patients with acute myocardial infarction: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Management of Acute Myocardial Infarction)

The cardiotoxic effects of adriamycin were studied in 399 patients treated for far-advanced carcimma. Forty-five patients (11%) exhibited transient electrocardiographs changes. Eleven others developed severe congestive heart failure. Eight of these latter patients died within 3 weeks of the onset of the cardiac decompensation. The diffuse nature of this myocardiopathy was suggested by: 1. a conspicuous decrease in the QRS voltage on the electrocardiograms; 2. rapidly occurring cardiac dilatation and ventricular failure, and 3. refractoriness to inoiropic drugs and mechanical ventricular assistance. Postmortem examination of the hearts in two cases showed a striking decrease in the number of cardiac: muscle cells present, degeneration of the remaining myocardial cells, loss o contractile substance, mitochondrial swelling, and intramitochondrial dense inclusion bodies. Congestive heart failure occurred only once in the 366 patients who were treated with less than 550 mg/m2 of adriamycin (0.27%), but there were 10 cases of cardiac failure in the 33 patients who received more than 550 mg/m2 of this drug (30%). Therefore, until more direct means are established to prevent adriamycin-induced congestive heart failure, it is suggested that the total dose of adriamycin should be limited to less than 550 mg/m2 to permit safer use of this efficacious cancer chemotherapeutic agent.

A clinicopathologic analysis of adriamycin cardiotoxicity

Gifts and exchanges

In the Volmer theory, sub‐critical droplets (embryos), with vapor pressure greater than their surroundings, nevertheless, grow statistically, because they exist in sufficiently greater numbers than neighboring larger droplets. Thus the formation of nuclei against the thermodynamic barrier presupposes the presence of very large numbers of embryos of all sizes.An approximate lower bound for the time (nucleation time) required for the formation of this system of embryos can be calculated readily by (1) neglecting the thermodynamic barrier which impedes their formation; (2) assuming that when droplets contain a certain supercritical number, Γ, of molecules they grow very rapidly because their vapor pressure is considerably lower than their surroundings; (3) assuming that the formation of the embryo system begins when the vapor first becomes saturated. The equation for the rate of formation of embryos then reduces to the heat conduction equation yielding a simple solution. The lower bound sought is found to be...

Nucleation in Very Rapid Vapor Expansions

The AVCO balloon pump has been employed in treating 40 patients with cardiogenic shock from acute myocardial infarction (CS-MI). All patients were given a trial of medical therapy with hemodynamic monitoring. The time from the development of shock to institution of intraaortic balloon pumping (IABP) was less than 24 hours in all but nine patients. Prior to IABP the mean hemodynamic values were: cardiac index (CI) 1.7 liters/min/m2; mean arterial pressure (MAP) 66 mm Hg; pulmonary artery wedge pressure (PAW) 22 mm Hg. After 24-48 hours of IABP the CI and MAP had increased 0.8 liters/min/m2 and 8 mm Hg, respectively, and the PAW had decreased 4.8 mm Hg. During IABP the shock syndrome was reversed in 31 patients. Four of 25 patients treated with IABP alone survived to be discharged, but two have died from subsequent infarctions. Because of the persistent high mortality, 15 patients judged unable to survive off IABP have undergone emergency surgical procedures with IABP continuing during preoperative angiogra...

Clinical and Hemodynamic Results of Intraaortic Balloon Pumping and Surgery for Cardiogenic Shock

Shock tube techniques for the production of shock waves up to Mach number 20 have been developed and reported previously by Resler, Lin, and Kantrowitz, J. Appl. Phys. 23, 1390 (1952). These techniques can produce high temperature gas with accurately known enthalpy (e.g., in argon 25 percent ionization has been produced following an incident shock). Spectroscopic studies of high temperature argon produced this way by Petscheck, Rose, Glick, Kane, and Kantrowitz, ``Spectroscopic studies of highly ionized argon produced by shock waves,'' J. Appl. Phys. 26, 83 (1955), showed that equilibrium ionization can be reached in the time available in these experiments (of the order of 100 microseconds). This paper reports a study of the electrical conductivity of high temperature argon produced by shock waves.At low degrees of ionization (less than 10−3 for argon), the diffusivity of electrons and thus the gas conductivity is determined by the cross section for electron‐atom collisions which has been measured by mobility and by scattering techniques. At high degrees of ionization (larger than 10−3 for argon) the diffusion of electrons is primarily limited by long range Coulomb interaction with positive ions and thus is independent of the chemical nature of the gas. Theoretical treatments of this case have been given by Chapman and Cowling, Cowling, and by Spitzer and Harm. At intermediate degrees of ionization additive effects of both of these resistivity mechanisms would be expected.Preliminary measurements with electrodes indicated large surface resistances. These effects were avoided by the development of an electrodeless technique in which the moving ionized gas deflected a magnetic field. Resultant voltages induced in a search coil were related to the conductivity distribution in the gas following the shock wave. At temperatures greater than 8000–10 000°K (depending on the gas density) the gas conductivity quickly reached a maximum value (up to 80 mhos/cm). The maximum conductivity obtained at these high temperatures agreed within 10 percent with theoretical expectations. It also agreed well with measurement of electrical resistivity in the cesium discharge by F. L. Mohler, Bur. Standards J. Research 21, 873 (1938). At lower temperatures the oscillograms indicated that the conductivity was still rising at the end of the hot region. Under these conditions maximum conductivities reached were much lower than the theoretical values. The ionization rate obtained varied considerably with the gas density.At the highest temperatures the conductivity declined quickly from the maximum value and the rate of decline could be correlated with the expected cooling due to recombination radiation. Indications of a high conductivity associated with luminous shock fronts were obtained.

Electrical Conductivity of Highly Ionized Argon Produced by Shock Waves

Experimental augmentation of coronary flow by retardation of the arterial pressure pulse.

Converging shock waves offer interesting possibilities of attaining very high temperatures and pressures. A theoretical treatment by G. Guderley which we have confirmed and extended by the method of characteristics indicated that the strength of a strong converging cylindrical or spherical shock varies inversely with a power (0.396 for γ=1.4) of the surface area of the wave, thus becoming very great close to the center of convergence. The experimental production of high temperatures and pressures by means of these converging shocks depends on their ``stability'' of form. A converging wave is said to be stable if it approaches perfect cylindrical or spherical shape, thus damping out random disturbances as it propagates. The experimental work of L. G. Smith on Mach reflection is applied to show that these converging waves are stable for the shock range (M≤2.4) covered by his experiments. Smith's work and the theoretical work of Lighthill indicate that the stability decreases greatly at high Mach numbers.The simplest experimental method of achieving a cylindrical converging shock is by the use of a shock tube with a converging channel. This, however, results in the hottest region of the gas being in close thermal contact with the cold walls. An axially symmetric shock tube has been designed and constructed which produces a complete converging cylindrical shock rather than just a sector and in which the region of convergence is comparatively well isolated thermally from the walls. It has been found possible to converge a moderate strength shock wave (M=1.7) sufficiently to produce considerable luminosity at the center of convergence. Schlieren photographs are presented showing various phases of the formation and stability of these converging waves.

Arthur Kantrowitz

Papers

Nucleation in Very Rapid Vapor Expansions

Clinical and Hemodynamic Results of Intraaortic Balloon Pumping and Surgery for Cardiogenic Shock

Electrical Conductivity of Highly Ionized Argon Produced by Shock Waves

Experimental augmentation of coronary flow by retardation of the arterial pressure pulse.

The Production and Stability of Converging Shock Waves