摘要:

ABSTRACTPulsed Doppler evaluation of pulmonary venous flow was performed in three groups of patients who had undergone either a Mustard or Senning procedure. Group I consisted of 43 patients in sinus rhythm who had undergone the Mustard procedure 9 months or more before the Doppler examination and 16 who were evaluated immediately after surgery. Group II consisted of 12 patients in sinus rhythm who had undergone the Senning procedure 9 months or more before the Doppler evaluation. Group III consisted of eight patients with mid baffle obstruction of the pulmonary venous atrium and seven with isolated stenosis of the pulmonary vein of which all but one had previously had associated mid baffle obstruction. In those without obstruction, the pulmonary venous flow pattern mirrored the left atrial pressure trace, with peak forward flow occurring during the x and y descent. Obstruction produced a specific high-velocity turbulent pattern, whether at the mid baffle or pulmonary venous level. This technique provides reliable noninvasive information about pulmonary venous flow after the Mustard or Senning procedure.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTLeft-to-right (L-R) shunting across a ventricular septal defect (VSD) often involves a direct VSD-pulmonary arterial component (jet) that surges from the VSD immediately into the pulmonary artery. We used the thermodilution technique in dogs with acute experimental VSD to quantify this component. In dogs with supracristal VSD (n = 7), the direct component represented 76 + 4% (mean ± SE) of the total L-R shunt on average, vs 39 ± 7% (p < .001) of the total in dogs with infracristal VSD and the same level of L-R shunting (n = 6). The direct component can be expected to impose additional hyperkinetic forces on the pulmonary artery since it is driven by the left ventricular pressure. Although not yet clinically proven, we speculate therefore that patients with supracristal VSD may be at greater risk of becoming jeopardized by late-onset pulmonary vascular obstructive disease. Since a part of the total shunt other than the direct component dropped into the right ventricle, the right ventricle bore only 24% of the total shunt in supracristal VSD, but 61% in infracristal VSD. We also found that the amount of direct component was decreased, and therefore another part must have increased, as the pulmonary vascular resistance was artificially raised. As a second speculation, therefore, we suggest that patients with supracristal VSD may have less enlargement of the right ventricle than those with infracristal VSD before pulmonary hypertension develops.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTCommon carotid occlusion in the rat significantly decreases the density of,-adrenergic receptors in preparations of microvessels obtained from ipsilateral and contralateral cerebral cortices. The disruption of nerve pathways connecting the hemispheres (callosal transection) partially reverses the effect of common carotid occlusion on /3-adrenergic receptor density in capillaries of the contralateral cortex. In addition, the destruction of the central noradrenergic system by intraventricular injection of 6-hydroxydopamine abolishes the effect of ischemia on capillary,3-adrenergic receptor function in both hemispheres. The results suggest that /3-adrenergic receptors located on microvessels are partially regulated by neuronal pathways and that focal ischemia induces neurochemical and functional changes in remote areas of the brain.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTWe studied the use of digital angiography for the quantification of regional myocardial perfusion in the dog using selective left coronary arterial injection of radiographic contrast material as a flow dilution indicator. We developed algorithms for generating time-intensity curves from regions of interest over the proximal coronary artery and the myocardium and for densitometric error correction by subtraction of the intensity curve over a small lead blocker before logarithmic transformation. The resultant myocardial time-density curves were analyzed for time from injection to peak concentration (TPC) and for exponential washout rate (k). A linear correlation was found between absolute coronary arterial blood flow and both k (slope = 0.13, r = .85) and 1/TPC (slope = 0.18, r = .85). Reproducibility of TPC and k for repeated studies was 11% and 16%. Induced hyperemia significantly improved the sensitivity to stenosis by increasing the average difference in TPC and k between regions served by normal and stenotic coronary arteries to 65% and 80%, respectively. By combining selective coronary arterial injection with the left lateral x-ray projection it was possible to avoid most overlap of regional perfusion beds in the dog. This study suggests that contrast dilution measurements made during digital coronary angiography provide a means for assessing the hemodynamic significance of stenoses and the efflcacy of therapeutic interventions.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTPressure-volume relationships in the right atrium were examined before and after the creation of acute exerimental tricuspid regurgitation in pigs. A 1.3 kHz multielectrode impedance catheter with a measuring current of 4 mA was used to determine instantaneous right atrial pressure and relative blood volume; right atrial dimension was assessed simultaneously with ultrasonic crystals attached to the atrial walls. Impedance volume waveforms and ultrasonic crystal dimensions closely paralleled each other at baseline and after the induction of tricuspid regurgitation. The normal right atrial pressure-volume plot exhibited a figure-of-eight configuration, with an “a-loop” and a “v-loop” corresponding to the a-wave and v-wave of the right atrial pressure tracing. With severe tricuspid regurgitation, atrial pump function was abolished, and the pressure-volume plot exhibited a single clockwise loop, consistent with complete ventricularization of the right atrium. Intermediate degrees of tricuspid regurgitation preserved the figure-of-eight loop, but the size of both the a-loop and the v-loop were increased, consistent with a Starling-type load imposed on the atrium by the regurgitant blood volume. Increased right ventricular afterload mediated by constriction of the pulmonary artery and infusion of methoxamine reversibly converted the right atrial pressure-volume loop from that of mild to that of severe tricuspid regurgitation. Alternatively, constriction of the inferior vena cava and infusion of nitroprusside changed the right atrial pressure-volume loop from that of a severe pattern of tricuspid regurgitation to a less severe type of pattern. Infusion of dobutamine increased the size of the a-loop relative to the v-loop both at baseline and after induction of tricuspid regurgitation. We conclude that tricuspid regurgitation induces changes in right atrial mechanics that can be detected and quantified with an impedance catheter.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTWe assessed the efficacy of conventional cardiopulmonary resuscitation (CPR) in 2- week-old piglets. We determined intrathoracic vascular pressures, cerebral (CBF) and myocardial blood flows (MBF), and cerebral oxygen uptake during conventional CPR in this infant animal preparation and contrasted these results with those of previous work on adult animals. We further examined the effects of the infusion of epinephrine on these pressures and flows and on cerebral oxygen uptake, which has not been previously evaluated in adult preparations. Conventional CPR was performed on pentobarbital-anesthetized piglets with a 20% sternal displacement with the use of a pneumatic piston compressor. Chest recoil was incomplete, leading to an 18% to 27% reduction in anteroposterior diameter during the relaxation phase. Aortic and right atrial pressures in excess of 80 mm Hg were generated. These pressures are greater than those generally obtained in adult animals with similar percent pulsatile displacements. CBF and MBF were also initially greater than those reported in adult animals undergoing conventional CPR. However, when CPR was prolonged beyond 20 min, aortic pressure fell and CBF and MBF declined to the near-zero levels seen in adult preparations. At 5 min of CPR, CBF and MBF were 24 + 7 and 27 7 ml min- l 100 g - 1 (50% and 17% of the values during cardiac arrest), respectively. With the continuous infusion of epinephrine (4,ug/kg/min) in another group of animals, MBF was significantly greater at 20 min of CPR and CBF and cerebral 02 uptake were greater at 35 min of CPR as a result of higher perfusion pressures. At 5 min of CPR, CBF and MBF were 46 + 9 and 65 + 16 ml.min- 1.00 g-, respectively. CBF and cerebral oxygen uptake were maintained at prearrest levels for 20 min of CPR. Epinephrine did not appear to have an adverse effect on cerebral oxygenation because cerebral 02 extraction was lower in the epinephrine group. In conclusion, we found that the infusion of epinephrine in a piglet preparation of CPR increased MBF, CBF, and cerebral oxygen uptake by selective vasoconstriction of other vascular beds. Compared with adult preparations, conventional CPR in infant piglets generated higher intrathoracic vascular pressures, MBF, and CBF, which may be related to the change in chest shape seen in this infant CPR preparation.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTHigh-energy electrical ablation is a new experimental approach to control arrhythmias. In this study, the cellular electrophysiologic effects of high-energy shocks (5 to 40 J) delivered in vitro to 14 epicardial tissues from 11 dogs were studied in an attempt to understand the nature and extent of injury as well as potential arrhythmogenic mechanisms. In addition, this preparation was used to test the importance of cathode-anode configuration, current density, and fiber orientation in the induction of tissue injury in vitro. Electrophysiologic abnormalities were noted up to 10 mm from the electrode wall, and their extent was determined in part by current density and the cathode-anode orientation. A decrease in resting membrane potential, action potential amplitude, and dV/dT occurred in all tissues after high-energy shocks, which was worst nearest the cathode and of graded severity at increasing distances from the cathode. The most severe effects were noted with high current densities and in tissues located between the cathode and anode. In addition, impaired impulse conduction and abnormal repolarization were documented. Histologic study demonstrated contraction band necrosis immediately after delivery of high-energy shocks. The extent and distribution of the contraction bands was in part dependent on the energy delivered and the cathode-anode configuration. These findings suggest potential mechanisms for arrhythmogenesis and altered regional hemodynamic abnormalities that occur in vivo.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTConcurrent stimulation of the parasympathetic and sympathetic branches of the autonomic nervous system causes a diminished sympathetic response at high levels of vagal activity. This "accentuated antagonism" has been demonstrated for cardiac chronotropic, inotropic, and dromotropic responses. The effect on conduction was demonstrated with tonic stimulation of the vagus nerve. However, normally the vagus nerve fires periodically at certain times in the cardiac cycle. Thus, we have studied whether a similar interaction exists in the modulation of atrioventricular condition when short bursts of vagal stimulation were placed in various portions of the cardiac cycle. Anesthetized open-chest mongrel dogs were instrumented for stimulation of the cervical vagi and stellate ganglia when the heart was paced. We determined the relationship between cardiac cycle length, direction of action potential propagation, and levels of sympathetic and vagal activation and their effects on atrioventricular conduction times. All of the factors investigated, namely levels of vagal and stellate stimulation, pacing intervals, and direction of propagation of action potentials, affected atrioventricular conduction times. Furthermore, the vagal effect was greater at short cardiac cycle lengths. When bursts of vagal stimulation were timed to result in maximal or minimal prolongation of atrioventricular conduction, no significant effects of sympathetic-parasympathetic interaction on atrioventricular conduction times were apparent. However, an analysis of the differences in prolongation of atrioventricular conduction with periodic vagal stimulation revealed that a significant sympathetic-vagal interaction existed for these differences. Thus, autonomic neurotransmitters differentially affect cardiac conduction times depending on time of application of the stimulus.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

ABSTRACTIn experimental animals, the calcium channel-blocking agents lessen the arrhythmogenic, ionic, metabolic, and electrical changes that occur during acute myocardial ischemia. To date, these effects have been studied separately, and the effects of these agents on local activation have not been correlated with ionic or metabolic effects. In open-chest, anesthetized swine, we used bipolar and ion-selective plunge electrodes to simultaneously measure ischemia-induced changes in left ventricular local activation, extracellular K+ ([KIIe), and extracellular pH (pHe) The effects of verapamil (0.2 mg/kg) on these variables were studied during a series of 10 min occlusions of the left anterior descending coronary artery. Compared with control occlusions, verapamil (1) slowed the rise in [K']e at the center of the ischemic zone and at its lateral margin and decreased the peak [K'+] by 0.9 mM at the center (p < .05) and by 0.1 mM at the margin (p = .10); (2) slowed the development of acidosis and decreased the peak level of acidosis beyond that expected solely as a result of serial occlusions by 0.19 pH units at the center (p < .05) and by 0.07 pH units at the margin (p = .10); and (3) slowed the development of local activation delay and often prevented the local activation block that was observed during control occlusions. Effects on local activation became less marked at [K']e levels greater than 9.0 mM, and the effects of verapamil on local activation were not explained solely by its effects on the local rise in [K+]e or fall in pHe. A possible mechanism for this additional effect on local activation is suggested by preliminary results showing a diminution by verapamil of ionic inhomogeneity.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID