ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Conduction time from the region of the sinus node to the region of the atrioventricular (A-V) node was studied during open heart surgery in 13 patients with an endocardial cushion type atrial septal defect, eight patients with a secundum type atrial septal defect, one patient with a sinus venosus type atrial septal defect, and eight patients with an intact atrial septum. Internodal conduction time was prolonged by an average of 37 msec (range 15-69 msec) in patients with an endocardial cushion defect when compared with the other three groups of patients. However, when the atria were paced from the A-V nodal region, the resulting P-R intervals in patients with an endocardial cushion defect were similar to those of patients in the other three groups, a fact that indicates normal A-V nodal-His-Purkinje conduction in patients with an endocardial cushion defect. It was therefore concluded that the prolonged P-R interval which patients with an endocardial cushion defect often manifest is due simply to prolonged internodal conduction time. Further, we have suggested that the data from this study support the concept that specialized atrial internodal pathways play an important role in conduction between the sinus and A-V nodes.

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

The atrioventricular (A-V) conduction time in patients with secundum ASD who had left-to-right shunts of 40-65% of their pulmonary flow was evaluated utilizing intracardiac electrograms. The A-V conduction time was divided into three components: (1) P-A interval, from the onset of the P wave to the time of excitation of muscle in the vicinity of the A-V node, (2) A-H interval, from the time of excitation of low right atrial muscle to that of the His bundle, and (3) H-V interval, from the time of the His bundle deflection to the onset of ventricular activation. The mean P-R interval of the ASD group (154 msec) was significantly longer (P< 0.01) than that of the control group (135 msec). The internodal conduction time (mean P-A interval) of the ASD group (52.2 msec) was significantly longer (P< 0.001) than that of the control group (29.1 msec). The A-H and H-V intervals of the two groups were not significantly different. Both the increased size of the atrium and the increased distance for internodal conduction produced by the defect itself can account for the prolonged internodal conduction time.

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

His bundle electrocardiography in a patient with a digitalis-induced bidirectional tachycardia revealed absence of His spike preceding earliest onset of ventricular activation during the bidirectional tachycardia. However, His potential preceded ventricular activation of normal complexes at a constant H-V interval of 35 msec. The presence of fusion QRS complexes, capture QRS complexes, the analysis of cycle lengths, and response to carotid sinus massage all favor a ventricular origin for this tachycardia in the patient presented.

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Permanent pervenous atrial synchronized ventricular pacing was successfully accomplished in three patients. Atrial sensing was obtained from an electrode positioned in the coronary vein. Atrial electrograms with P waves greater than 1.5 mv were present in all three cases. Ventricular stimulation was accomplished through a separate electrode placed in the right ventricular apex. The left cephalic vein admitted both catheters, and the two electrodes were connected to an implantable P wave synchronized unit. The beneficial hemodynamic effects of atrial synchronized ventricular pacing were clinically evident. This new pervenous technique provides an optimal method of synchronized pacing in patients with heart block, intact sinoatrial activity and significantly compromised cardiac function.

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Wenckebach periods of alternate beats (AW) can be described as a 2:1 atrioventricular (A-V) block in which the conducted P waves show progressive prolongation of the P-R interval of the Wenckebach type. However, while classical Wenckebach periods terminate with a single blocked P wave, AW necessarily ends with (or begins from) two consecutive blocked P waves. Five clinical cases and several experimental examples of AW are reported. Recovery curves of A-V conduction were constructed, and it was demonstrated that AW is related to a marked prolongation of both the absolute and relative refractory periods. All the cases were associated with intraventricular block. In addition, recording of His bundle potentials in one case, histological study of the conduction system in another, and the experimental observations, support the view that AW tends to occur below the A-V node, in one of the main ventricular conducting fascicles. Four of the five patients developed complete heart block and Adams-Stokes seizures.

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Systolic time intervals were performed on 49 male subjects. Twenty-eight subjects were inactive with respect to a continuing exercise program and were classified as a sedentary group. Twenty-one subjects were physically active and were classified as an active group. The active group was composed of 12 members who were moderately active and nine members of a college track team. Using analysis of covariance no significant difference was found in the total duration of electromechanical systole (QS2), left ventricular ejection time (LVET), or the preejection period (PEP) between the moderately active subgroup and the members of the track team. However, a highly significant difference was found between the sedentary and the active group in the QS2and PEP. The LVET was not significantly different.The results of this study appear to be consistent with the hypothesis that an increase in intrinsic myocardial performance is associated with physical conditioning. In addition, it is suggested that published equations for the QS2interval and the PEP may be applicable only to sedentary individuals.

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

Study of left ventricular pressure-volume relations in man has been limited by technical problems associated with left ventricular angiography. A new approach to this problem using simultaneous recording of left ventricular pressure and left ventricular volume (determined by echocardiography) was applied in 21 patients. Pressure-volume plots, constructed from pressure and volume values sampled at 20 or 40 msec intervals, had characteristic shapes for the states studied: normal, pressure overload, volume overload, and myocardial disease. These curves closely resembled pressure-volume plots previously determined by others from quantitative angiography.The area inscribed by these plots was integrated to calculate left ventricular stroke work. Left ventricular stroke work index (gram-meters/m2) was in the range previously reported for the various states; normal-41 ± 12, pressure overload-102 ± 14, volume overload-136 ± 36, myocardial disease-65 ± 19. Inspection of the pressure-volume plots allowed assessment of valvular regurgitation by the characteristic deformation of the loop during “isovolumic’ contraction and relaxation. Study of diastolic filling allowed qualitative assessment of left ventricular compliance. Patients with pressure overload had stiffer ventricles, with high diastolic pressure at lower volume, than normal or volume overload patients.In summary, a new method is described for the beat-to-beat analysis of left ventricular pressure-volume relations in man.

ISSN:0009-7322    

出版商:OVID    

年代:1973

数据来源: OVID