ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Extracellular action potentials of the A-V node (N), His bundle (H), and right bundle branch (RB) were recorded in subjects with an electrode cardiac catheter which was fluoroscopically positioned across the tricuspid valve. The N potential is a slow diphasic wave occurring between the atrial electrogram (P) and the H potential. It is characterized by slurring or notching on the upstroke. The H potential, as previously described, is a biphasic or triphasic wave of 15 to 20-msec duration. The RB potential is a fast biphasic wave of 10 to 20-msec duration occurring between the H potential and the Q wave. During single atrial pacing and premature atrial stimulation, the A-V conduction delay could be localized to the N-H interval. Evidence suggests that during aberrant ventricular conduction of the right bundle-branch block type the impulse was blocked proximally in the right bundle. During concealed conduction the nonconducted impulse was completely blocked within the A-V node or the N-H interval.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Tritiated digoxin (0.5 mg) was given intravenously to five elderly men (mean age, 77 years) and nine young men (mean age, 27 years). The elderly were not in congestive heart failure. The serum creatinines of the old and young were not different. However, the creatinine clearance averaged 56 ml/min/1.73 m2in the old and 122 ml/min/1.73 m2in the young (P<0.001). Digoxin clearance averaged 53 ml/min/1.73 m2in the old and 83 ml/min/1.73 m2in the young (P<0.001). The blood concentrations of tritiated digoxin were significantly higher in the elderly throughout the study (P<0.05). When blood digoxin concentrations were corrected for body surface area, there was no significant difference between the two groups during the first 24 hr, but thereafter the concentrations in the elderly were higher.The same dose of digoxin resulted in higher blood concentrations and longer blood half-life in the elderly. This is due to the smaller body size and a diminished urinary excretion of digoxin in the elderly.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Sufficient delineation of differences in density is often not achieved by standard x-ray cinematographic technic. As a result, when cineventriculography is used to study the shape and motion of the left ventricle, its free wall is often defined imprecisely, if at all. This problem has been overcome by utilization of a special color-coded, triple-emulsion cine film in place of the usual black and white film. The resulting photographic images permitted analysis of wall dynamics and measurement of wall thickness in different planes of the heart. Thickening of the normal wall during systole averaged between 70 and 106%, but with inconsistent nonuniform regional changes within this range. In the diseased left ventricle with localized areas of paradoxical expansion, markedly reduced if any thickening of the wall occurred during systole.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

We have studied Korotkoff sounds in 10 subjects by recording pressures and sounds simultaneously through a brachial arterial needle at locations both beyond and beneath the inflatable cuff. The Korotkoff sounds coincided with a small dip and ensuing steep rise in pressure immediately beyond the distal edge of the cuff. Sound intensity paralleled not only the rate and the acceleration of this steep ascent, but also the total pressure through which it was maintained. Pressures beneath the midportion of the cuff showed a more pronounced sharp initial negative dip, usually followed by a rapid reversal and steep rise, and the sounds were also recorded here in association with these rapid pressure changes. This study supports the hypothesis that the initial Korotkoff sound is produced by rapid changes of pressure both beneath and distal to the compressing cuff, sufficient in rate to impart sonic vibrations to the vessel wall and surrounding tissues. We have attempted to explain how these rapid pressure changes are produced.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

The sound-pressure correlates of the aortic ejection sound (AES) were studied in six patients without aortic valve disease (group 1) and in nine patients with valvular aortic stenosis (group 2) during diagnostic left heart catheterization. Aortic root sound and pressure events were recorded by a catheter-tip micromanometer simultaneously with the external phonocardiogram, indirect carotid pulse, and electrocardiogram. The AES in group 1 patients was coincident with the onset of pressure rise in the aortic root. This relationship was not altered by drug administration, although variations in the amplitude of the AES occurred. It was concluded that the AES in patients without aortic valvular disease is an exaggerated ejection component of the normal first heart sound, and that it is a root phenomenon related to the forceful ejection of blood into the aorta. The AES in group 2 patients was delayed 24 to 40 msec after the onset of pressure rise in the aortic root, was coincident with the anacrotic notch, and introduced the aortic ejection murmur. Aortic root sound and pressure were recorded simultaneously with aortic valve motion during angiography in two patients utilizing a cine trace system. The AES occurred when the domed valve reached its maximal excursion, and the interval between the onset of aortic pressure rise and the AES was equal to the total time required for the piston-like ascent of the dome. It was concluded that the AES in valvular aortic stenosis is valvular in origin. The amplitude of the valvular AES correlated best with valve mobility on the angiogram, and no correlation existed between its presence and the severity of the valvular stenosis.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

In seven patients with complete A-V block of long duration (five suffering from Adams-Stokes attacks), the cerebral blood flow was found to be significantly decreased and there was also moderate slowing of the electroencephalogram. Artificial pacing increased the heart rate from 39 to 72/min. Postoperative studies showed that in six of the seven cases the cerebral blood flow had increased and that the mean spectral frequency of the EEG had increased. In two patients follow-up studies suggest that the normalization of the EEG and cerebral blood flow may take some time to develop fully. The changes in EEG and cerebral blood flow paralleled the clinical improvement which accompanied the pacemaker therapy in all the patients.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Of 130 patients who received permanent pervenous pacemakers in the last 2 years at the Massachusetts General Hospital, 21 have died; complete postmortem data are available on seven who died 5 days to 18 months after insertion of the pacemaker. No deaths were related to pacemaker malfunction. No patient received routine anticoagulant therapy. The intracardiac portions of all pacemaker electrodes were 30 to 80% endothelialized. In three cases tiny, organized mural thrombi formed on these sheaths, but none appeared to give rise to pulmonary emboli. All pacemaker electrode tips were wedged firmly beneath the trabecular system of the right ventricular apex and elicited varying degrees of local fibrous tissue reaction. Further focal fibrotic attachments occurred in the right atrium and superior vena cava. Although in four cases the electrodes adhered to the chordae tendineae, the long-term presence of an electrode did not appear to compromise tricuspid valve function. Late removal of an electrode may be hazardous because of its firm attachments to the endocardium and tricuspid valve.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

To determine whether the hyperkinetic circulatory response to chronic anemia is obligatory and to assess its strength and potential reversibility, the hemodynamic state at rest was assessed (indicator-dilution method) in 24 patients with chronic anemia before and after certain interventions.A comparison of cardiac output measured before and after treatment established the consistency of the hyperdynamic response to anemia. In the absence of convalescent data, this response might have been overlooked in some anemic patients whose cardiac output fell within the normal range. In the anemic state, cardiac output correlated negatively and significantly with age (r=-0.752). This relationship may account for the apparent absence of the hyperkinetic circulation in elderly, anemic patients.In only the most anemic (hemoglobin, 3.8 g/100 ml) of six patients did inhalation of 100% oxygen lower cardiac output significantly.In four patients, studied in both the supine and sitting posture, orthostatic stress was consistently accompanied by a decrease in central blood volume (7%) and an increase in total systemic resistance (64%), resulting in a reduction of both stroke index (28%) and cardiac index (23%).Administration of methoxamine to seven anemic patients resulted in increases in mean arterial blood pressure (24%) and total systemic resistance (40%) in all and a decrease in cardiac output in all but one patient (mean, 20%).Peripheral vasoconstriction induced by means of orthostatic stress or by a pressor amine thus effected an acute reversal of the high output state in chronic anemia. These observations suggest that redistribution of blood volume and vasodilatation play a dominant role in the hyperkinetic circulatory response to chronic anemia and indicate that this state is labile rather than fixed.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID

摘要:

Experience with a maximal treadmill stress testing procedure which is relatively safe, simple, and reproducible is reported. It has been used in normal persons and cardiac patients with ages ranging from 7 to 83 years. There have been no deaths in our total experience of 4,028 maximal capacity stress tests. Maximal capacity is predicted by the patient's peak predicted pulse rate. Sixty-three per cent of those with ischemic S-T segments did not experience pain of any type.

ISSN:0009-7322    

出版商:OVID    

年代:1969

数据来源: OVID