Nesiritide for the treatment of pulmonary hypertension and cor pulmonale in an infant.

Nesiritide is a synthetic form of B-type natriuretic peptide. It is approved for the treatment of acute exacerbations of congestive heart failure in hospitalized adult patients. It is currently under investigation for use in other settings and other patient populations. This article describes administration of nesiritide to an infant patient with severe pulmonary hypertension and cor pulmonale. No adverse reactions occurred during administration of the drug. Specifically, there was no hypertension, vomiting, arrhythmia, or changes in renal function. No changes in renal function occurred in the months subsequent to treatment. This case report illustrates that nesiritide can be safely administered to critically ill infants with pulmonary hypertension and cor pulmonale. Our patient experienced a decrease in pulmonary pressure and improved clinical condition during and after the infusion. However, further study is required to fully evaluate the safety and efficacy of nesiritide for these patients.

Observation of inverse ion-cyclotron damping induced by parallel-velocity shear.

The generation of broadband multiharmonic spectra of electrostatic ion-cyclotron waves is demonstrated in a magnetized laboratory plasma in which shear in the magnetic-field-aligned (parallel) ion flow and a relative parallel electron drift are present. Shear correlates with an increased number of harmonics and a decreased electron drift speed. Wave and particle measurements indicate that cyclotron damping is reduced and even becomes negative. The fluctuations in the time domain are spiky, similar to electric-field fluctuations observed both in Earth's auroral zone and in numerical simulations.

Experimental verification of the shear-modified ion-acoustic instability.

The predicted shear-induced shift of the wave phase velocity, the essence of the shear-modified ion-acoustic (SMIA) instability mechanism that reduces ion Landau damping for otherwise damped ion-acoustic waves [V. Gavrishchaka et al., 80, 728 (1998)], is verified with direct measurements in a strongly magnetized laboratory plasma. The SMIA growth rate is shown to increase with increasing shear, as predicted. SMIA wave propagation is shown to be possible at both small and large angles to the magnetic field, consistent with space observations of ion-acoustic-like waves.

Effectiveness of coronary care units in small community hospitals.

A prospective study was undertaken from 1969 to 1974 to evaluate a program establishing coronary care units in small community hospitals. Crude mortality rates from acute myocardial infarction in these small hospitals were 14.5%, slightly higher but not statistically different from concurrently collected data in three larger comparision hospitals (11.5%). Mutivariate discriminate analysis of clinical characteristics was used to calculate a risk score for each patient admitted. Observed deaths exceeded expected deaths (134 versus 119) (P greater than 0.30) in small hospitals but observed deaths were less than expected (55 versus 77)(P less than 0.05) in comparison hospitals. Mortality was significantly greater in those units admitting fewer than 60 patients with infarctions yearly (20.9%) than in those admitting more than 60 (10.7%) (P less than 0.001). These data suggest that coronary care units in small community hospitals can provide adequate coronary care, but their level of performance drops when fewer than 60 patients with infarctions are admitted yearly.

Quinidine syncope. A report of successful treatment with bretylium tosylate.

Quinidine syncope is an unpredictable side effect of quinidine administrateion which has a mortality rate of 11.5 per cent when managed with conventional drugs and direct-current countershock. In 2 patients with quindine syncope, the arrhythmias were effectively controlled within 30 minutes following the slow infusion of 150 mg. of bretylium tosylate. This control is contrasted with 2 cases managed in the conventional manner. Bretylium tosylate is a quaternary amine with unique antifibrillatory properties and appears to have a significant role in the management of these arrhylmias.

Cellular basis for reversal of hyperkalemic electrocardiographic changes by sodium.

We examined the hypothesis that reversal of hyponatremic hyperkalemic electrocardiographic changes through the infusion of saline solutions was due to the action of sodium ion in increasing the action potential rising velocity which is depressed when the cell is exposed to increasing concentrations of potassium. Using standard microelectrode techniques, the rising velocity of canine ventricular cells was shown to increase by 21%, whereas conduction time between two microelectrodes decreased 17% when the sodium concentration of the perfusate was increased from 120 to 163 mM in 2.7 mM potassium solution. When these cells were exposed to identical increases in sodium concentration in a 7.7-mM potassium solution, rising velocity increased 55% (P less than 0.005), whereas interelectrode conduction time decreased 33% (P less than 0.05). Similar changes were noted in experiments on human ventricular cells. These experimental findings are consistent with the hypothesis stated above.

Genesis of high frequency notching of QRS complexes in an in vivo cardiac model.

High frequency notching of the QRS complex is associated with transmural infarction, cardiomyopathies, and ventricular hypertrophy from any cause. The mechanism producing notching is unknown; but the presence of a discrete anatomic lesion is not an essential feature. The hypothesis that notching was produced by activation across, rather than along, myocardial fibers was investigated by stimulation at 12 points around a clock electrode attached to the epicardium while mapping isoschronous lines in the area activated. All fibers at the subendocardial layer beneath the clock electrode were ligated by a pursestring suture. Propagation direction, as measured by isoschronous maps, produced more notched QRS compleses when the path was across, rather than paralled with, the myocardial fibers. Using grouped data and a 5 times 6 table, notches versus the angle formed between fiber direction and orientation of the direction of travel were shown to be related (P less than 0.001). The hypothesis that cross-fiber activation enhances notching was confirmed. retrograde activation did not increase notching nor did ligation of subendocardial fibers.