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Biomedical subjects

L L Stevens

Publications and source records attributed to L L Stevens.

8 recordsLinked to original sources
PubMed1989

Emergency catheter ablation of refractory ventricular tachycardia.

Catheter ablation, in extreme cases, can be used successfully as emergency therapy for VT in the CCU. In the hands of a physician experienced in electrophysiologic procedures, catheter ablation may prove to be an alternative to surgical or pharmacologic therapy in acutely ill patients with refractory ventricular arrhythmias.

Aged↗
PubMed1988

Effect of conduction defects on the signal-averaged electrocardiographic determination of late potentials.

To determine the effect of cardiac conduction defects on the signal-averaged electrocardiogram (ECG) and on its ability to noninvasively identify patients predisposed to ventricular tachycardia (VT), standard 12-lead ECGs and signal-averaged ECGs were obtained in 213 patients with normal conduction and 186 patients with various conduction defects. Sustained VT was induced by programmed stimulation or occurred spontaneously in 122 patients. Two-way analysis of variance showed that conduction defects and VT were associated with changes in 3 signal-averaged ECG parameters: duration of the filtered QRS, duration of the terminal QRS under 40 microV and the mean amplitude of the terminal 40 ms of the QRS. Stepwise multiple logistic regression identified 3 variables that distinguished the patient with VT with a sensitivity of 62%, a specificity of 63% and a positive predictive accuracy of 63%. These 3 variables, listed in order of importance, were conduction defect score, duration of the filtered QRS and mean amplitude of the terminal 40 ms of the QRS. These data indicate that conduction defects have systematic effects on signal-averaged ECG parameters independent of those seen in patients predisposed to VT. These effects mandate the adjustment of the definitions of late potentials in the presence of conduction defects.

Adult↗
PubMed1988

Effects of electrophysiologic studies resulting in electrical countershock or burst pacing on left ventricular systolic and diastolic function.

To determine the acute effects of electrophysiologic study on left ventricular systolic and diastolic function in patients requiring termination of induced tachyarrhythmias by either electrical countershock or burst pacing, we examined 16 patients (11 men and five women), aged 43 to 78 years (mean 58 +/- 13), undergoing programmed electrical stimulation. Indices of systolic and diastolic left ventricular function were measured by M-mode echocardiography before and within 1 minute after termination of 22 episodes of induced tachyarrhythmias by defibrillation (n = 16) and burst pacing (n = 6). The left ventricular septal and posterior endocardial surfaces were digitized immediately below the mitral valve leaflets, and indices of systolic and diastolic function were calculated. The results showed a significant impairment in both systolic and diastolic function after termination of tachyarrhythmias by defibrillation, as seen by a decrease in the shortening fraction (23.7 +/- 7.6% to 19.8 +/- 7.8%; p less than 0.005) and a decline in the peak rate of increase in left ventricular diameter during diastole called dD/dtmax (87.4 +/- 36.1 mm/sec to 71.5 +/- 28.9 mm/sec; p less than 0.01), respectively. In addition, indices of systolic and diastolic function measured at baseline were predictive of impairment in diastolic function, as seen by modest but highly significant correlations between the absolute change in dD/dtmax after defibrillation versus the peak velocity of fiber shortening (r = -0.69; p less than 0.005) and dD/dtmax (r = -0.60; p less than 0.02) measured at baseline. Left ventricular function after termination of tachyarrhythmias by burst pacing was not significantly altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Independent value of signal-averaged electrocardiography and left ventricular function in identifying patients with sustained ventricular tachycardia with coronary artery disease.

To determine if the signal-averaged electrocardiographic detection of late potentials is an independent marker of sustained ventricular tachycardia (VT) in patients with documented chronic coronary artery disease (CAD), 57 patients underwent signal-averaged electrocardiography. Mean ejection fraction was 47 +/- 13% in the 14 patients with sustained VT and 56 +/- 19% in the 43 patients without VT (difference not significant). The sensitivity, specificity and accuracy of late potentials for detecting patients with VT were 64% (9 of 14), 79% (34 of 43), and 75% (43 of 57), respectively. Univariate analysis and stepwise logistic regression of angiographic and electrocardiographic variables identified late potentials as an independent marker of the patient with sustained VT. The odds ratio for late potentials to detect patients with prior sustained VT was 2.6. Six-month follow-up revealed a cardiac mortality rate of 11% and an arrhythmia event rate of 22% in patients with late potentials vs a cardiac mortality rate of 3% and an arrhythmia event rate of 13% in patients without late potentials. Thus, signal-averaged electrocardiographic detection of late potentials is useful in identifying patients with prior sustained VT independent of left ventricular function.

Adult↗