ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Computerized arrhythmia monitors recognize only a few of the significant arrhythmias and generally fail to detect arrhythmias of supraventricular origin. This is because conventional surface leads, which are sufficient for QRS recognition, are highly inadequate for automated P-wave detection. A new twolead system, which includes a swallowable capsule-electrode for esophageal monitoring of atrial activity, is used in an on-line arrhythmia monitor. Three interval measurements (AA, AR and RR) and a QRS shape measurement provide the foundation for a detailed interpretation of each beat. Building on the single-beat analysis, a contextual diagnostic algorithm then recognizes and reports on-line the following arrhythmias: couplets, bigeminy, trigeminy, ventricular tachycardia, supraventricular tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia with retrograde conduction to the atria, first-degree block, second-degree block, Wenckebach periodicity, advanced block, third-degree block and sinus bradycardia.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

In this study, we describe the findings in 18 young patients (age range 4 days to 24 years, mean 16.6 years) who had ventricular tachycardia and/or ventricular fibrillation and were followed for 4-70 months (mean 22.4 months). Patients had a variety of problems associated with their arrhythmia, including mitral valve prolapse, cardiomyopathy, myocarditis, prolonged QT syndrome and hypokalemia. Six patients had no clinically recognizable cardiac abnormality. The ventricular tachycardia showed a left bundle branch block contour in 10 of 17 patients, right bundle branch block in four, was multiform in two and had an indeterminate contour in one. Sustained ventricular tachycardia was initiated and terminated reproducibly by atrial and ventricular stimulation in three of seven patients who did not have spontaneous episodes of ventricular tachycardia during the electrophysiologic study. In one other patient, short bursts of ventricular tachycardia were induced. Patients who had ventricular fibrillation, those who died, and those who are still symptomatic with poorly controlled ventricular arrhythmias had significant heart disease. In one patient, a ventricular tachyarrhythmia that had required more than 100 electrical cardioversions spontaneously disappeared after requiring I year of antiarrhythmic therapy.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The role of ventricular ectopic beats (VEBs) in identifying patients who die of cardiac cause in the posthospital phase of myocardial infarction was evaluated in 940 patients who survived an acute coronary event. Six-hour Holter ECG recordings were obtained before hospital discharge, and VEBs were classified as complex (bigeminal, multiform, repetitive or R on T), simple (one or more VEBs that did not have complex patterns), or not present. Patients were followed 1-60 months (average 36 months) and cardiac mortality was categorized as sudden (⩾ I hour) or nonsudden (> I hour) among 98 witnessed cardiac deaths. Complex VEBs were associated with a significantly increased cardiac death rate, but did not discriminate between sudden and nonsudden death. Simple VEBs were associated with a 3-year cardiac mortality rate intermediate between those with complex and those with no VEBs. The relationship between complex VEBs and cardiac mortality was independent of 10 relevant clinical variables.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Preliminary studies have suggested that QRS-amplitude changes due to exercise-induced alterations in ventricular volume and function can improve the diagnostic value of the exercise test. To evaluate this, electrocardiographic data and equilibrium radionuclide angiographic images were recorded simultaneously in 18 normal subjects and 60 coronary artery disease patients at rest and during supine bicycle exercise. In 24 of the 60 coronary artery disease patients, left ventricular volumes were also calculated. The measured QRS amplitudes were the R waves in V5, X, Y and Z, the Q wave in Z and the sum of amplitudes of R waves in X and Y and the Q wave in Z (2iR). The mean left ventricular ejection fraction increased significantly from rest to peak exercise in the normal subjects; however, the mean left ventricular ejection fraction and mean volumes did not change significantly in the coronary patients. There was no significant difference in the mean QRS-amplitude changes during exercise between the coronary artery disease patients and the normal subjects in any of the measured leads. The sensitivity and specificity of exercise-induced QRS-amplitude changes for coronary disease were lower than ST-segment changes. For ST-segment changes, the sensitivity was 57% and specificity was 100%; the best sensitivity and specificity for QRS amplitude occurred in RZ, 48% and 67%, respectively. When ejection fraction was related to 2R at rest and peak exercise for both normal subjects and coronary patients the correlations were fair (0.50, 0.51 respectively); however, the correlation between the magnitude of 2R and ejection fraction change from rest to peak exercise was poor and did not improve with any other measured QRS amplitudes or by separating normal subjects from coronary patients with and without previous myocardial infarction. There were also poor correlations between end-diastolic and endsystolic volumes to QRS amplitudes at rest, peak exercise and their magnitude of change from rest to peak exercise. Thus, R-wave amplitude changes during exercise testing have little diagnostic value and are not related to exercise-induced changes in left ventricular function or volumes.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The prevalence and cineangiographic correlates of exercise-induced inversion of U waves were studied in 248 patients. Exercise-induced U-wave inversion was observed in 36 patients (15%), of whom 35 had > 75% stenosis in one or more of the major coronary arteries. The proximal left anterior descending or left main coronary artery was involved in 33 of these patients, including 24 patients with no electrocardiographic evidence of anterior myocardial infarction. Exercise-induced U-wave inversion was observed in the absence of an abnormal ST-segment response in eight of the 166 patients (4.8%) with coronary artery disease, and five of these patients had a normal resting 12-lead ECG. Only one of the 82 patients (1.2%) without significant coronary artery disease demonstrated exercise-induced U-wave inversion, and this patient had a primary cardiomyopathy. We conclude that exercise-induced inversion of the U-wave is highly predictive of significant coronary artery disease and, more specifically, of disease of the proximal left anterior descending coronary arter.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We evaluated the ability of ST-segment analysis during submaximal exercise tolerance testing (85% predicted age-adjusted heart rate) to diagnose the presence of significant coronary artery stenosis (2 75% cross sectional area narrowing) in a group of 85 men and 92 women with chest pain syndromes and no previously documented myocardial infarctions. Disease prevalence by selective coronary angiography was 36% for men and 33% for women (NS). Predictive value of a positive exercise test (PV(+ET)) as defined by 1 mm ST-segment depression 0.08 second after the J point was significantly higher for men than for women (77% vs 47%,P< 0.05). Predictive value of a negative test (PV(-ET)) was not significantly different for men (81%) and women (78%). Analysis of the 66 men and 66 women not taking digitalis preparations again showed that PV(+ET) was significantly higher for men than for women (90% vs 45%,P< 0.01).Multivariate analysis showed that patients with angiographically significant coronary disease had significantly lower attained heart rates and shorter exercise duration than those without significant stenosis, independent of ST-segment responses. A discriminant function using ST-segment response, attained heart rate and a sex-dependent ST-segment response factor was developed. Duration of exercise was not an independent predictor by our analysis. This function improved the PV(+ET) and PV(-ET) for the total group and for the women; for men, the PV(-ET) improved, while the PV(+ET) fell slightly. This function has not yet been used prospectively.In patients with chest pain and no previously documented myocardial infarction, men have a significantly higher PV (+ ET) than women, which cannot be accounted for simply by a difference in disease prevalence (i.e., Bayes' theorem).

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Forty asymptomatic male patients at low risk for cardiovascular disease completed maximal treadmill testing. Electrocardiograms from leads CC5, CM5, V5, Yh and Z were recorded across multiple pretest, exercise and recovery conditions. ECG waveforms were subsequently digitized, averaged and processed to provide Q-, R-, S- and T-wave amplitudes, ST-segment means and slopes, and QS- and RTinterval durations. Average R-wave amplitude increased during early exercise and then dramatically decreased to maximum effort. Average S-wave amplitude became greater as exercise progressed. Average J junction was slightly positive before exercise, became negative during exercise (except lead Z) and returned to zero after exercise. The ST-segment slope increased dramatically with progressive exercise. The response of T-wave amplitude, RT and QS intervals are also described.Separately, 22 asymptomatic male subjects each completed two maximal treadmill tests 2 weeks apart. ECG data acquisition and processing were similar to those noted above. Pooled, within-subject estimates of variability were computed for the ECG leads, ECG measurements and protocol conditions. These variability estimates are useful for interpreting ECG responses to exercise testing.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The reproducibility of clinical and hemodynamic events during two successive pacing periods separated by a 20-minute interval was evaluated in 33 patients with stable angina pectoris. Continuous pacing with stepwise increase in pacing rate was assessed in 19 patients and discontinuous pacing in which pacing was temporarily interrupted at each rate was evaluated in the other 14 patients.During continuous pacing, the group values for pacing rates that induced angina, the pacing time to angina, ST-segment depression, rate-pressure product, cardiac output and left ventricular end-diastolic pressure (LVEDP) were similar during the two pacing periods, but postpacing LVEDP was lower after the second pacing period (P< 0.05). During the second pacing period, angina could not be reproduced at the same pacing rates in four patients and postpacing LVEDP varied by 5 mm Hg or more in 10 of the 19 patients.During discontinuous pacing, the group mean values for pacing rates that induced angina and the pacing time to angina were higher (P< 0.05), and cardiac output lower (P< 0.05) during the second pacing period, while rate-pressure product, ST-segment depression, and LVEDP were similar during the two pacing periods. During the second pacing study, angina could not be induced at the same pacing rates in six patients and the postpacing LVEDP varied by 5 mm Hg or more in three of the 14 patients.The results show that continuous pacing is preferable to discontinuous pacing. With continuous pacing, the group values for the clinical and many of the hemodynamic parameters were reproducible. We recommend the demonstration of the reproducibility of events during pacing in studies in which the effects of therapeutic interventions are being assessed, especially in a small number of patients.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID