Circulation
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Congenital heart lesions may be complicated by pulmonary arterial smooth muscle hyperplasia, hypertrophy, and hypertension. We assessed whether inhaling low levels of nitric oxide (NO), an endothelium-derived relaxing factor, would produce selective pulmonary vasodilation in pediatric patients with congenital heart disease and pulmonary hypertension. We also compared the pulmonary vasodilator potencies of inhaled NO and oxygen in these patients. ⋯ Inhaled NO is a potent and selective pulmonary vasodilator in pediatric patients with congenital heart disease complicated by pulmonary artery hypertension. Inhaling low levels of NO may provide an important and safe means for evaluating the pulmonary vasodilatory capacity of patients with congenital heart disease without producing systemic vasodilation.
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Case Reports
Augmentation of coronary blood flow by intra-aortic balloon pumping in patients after coronary angioplasty.
Controversy exists regarding the ability of intra-aortic balloon pumping to increase coronary blood flow in patients with obstructive coronary artery disease. To assess the effects of intra-aortic balloon pumping on coronary hemodynamics, we measured coronary blood flow velocity with a 0.018-in. Doppler-tipped angioplasty guide wire in 15 patients who received an intra-aortic balloon pump for typical clinical indications. ⋯ These data demonstrate lack of significant flow improvement beyond most critical stenoses with intra-aortic balloon pumping and the unequivocal restoration and intra-aortic balloon pump-mediated augmentation of both proximal and distal coronary blood flow velocities after amelioration of severe coronary obstructions in patients after successful coronary angioplasty.
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Although postprandial hypotension is a common cause of falls and syncope in elderly persons and in patients with autonomic insufficiency, the pathophysiology of this disorder remains unknown. ⋯ 1) In healthy elderly subjects, the maintenance of blood pressure homeostasis after food ingestion is associated with an increase in HR, forearm vascular resistance, cardiac index, and plasma NE. In both young and old, systemic vascular resistance is maintained. 2) Dysautonomic patients with postprandial hypotension fail to maintain systemic vascular resistance after a meal. This impairment in vascular response to meal ingestion may underlie the development of postprandial hypotension. 3) The measurement of mean HR or plasma NE does not adequately characterize autonomic cardiac control. Power spectral analysis suggests an impairment in the postprandial autonomic modulation of HR in healthy elderly and dysautonomic subjects, possibly predisposing to hypotension when vascular compensation is inadequate.
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Comparative Study
Use-dependent prolongation of ventricular tachycardia cycle length by type I antiarrhythmic drugs in humans.
Type I antiarrhythmic drugs block the cardiac sodium channel in a use-dependent fashion. This use-dependent behavior causes increased drug binding and consequently increased sodium channel blockade at faster stimulation rates. Importantly, the kinetics of drug association and dissociation from the sodium channel differ for each type I antiarrhythmic drug. ⋯ Use-dependent prolongation of VT cycle length during treatment with type I antiarrhythmic drugs was observed in humans. This effect was clinically significant during treatment with flecainide (i.e., the use-dependent slowing of the heart rate improved the hemodynamic tolerance of the arrhythmia). Finally, the estimated time constants for the use-dependent prolongation of VT cycle length by the three test drugs are similar to their reported in vitro time constants for use-dependent sodium channel blockade.