Quantitation of day to day variability in mode of induction of ventricular tachyarrhythmias by programmed stimulation.

Spontaneous day to day variability in the mode of induction of ventricular tachycardia at programmed stimulation in the drug-free state has been described but not quantitated. To quantitate this variability, this study employed a new protocol of programmed stimulation in which the number of extrastimuli required for tachycardia induction was the only major stimulation variable. This protocol was applied to 18 consecutive patients with previously documented sustained ventricular tachyarrhythmia due to coronary artery disease. One to seven extrastimuli were available for arrhythmia induction if required. Each patient underwent programmed stimulation in the absence of antiarrhythmic drugs on 3 separate days with a mean interval of 5 +/- 2.7 days between studies. A sustained ventricular tachyarrhythmia was inducible in all studies with less than or equal to 4 extrastimuli; the mean number of extrastimuli required was 2.4 +/- 0.8. Day to day variability in the number of extrastimuli required for tachycardia induction was observed in the majority of patients (72%). Eleven patients (61%) varied by one extrastimulus over the three control studies, and two patients (11%) varied by two extrastimuli. At analysis of variance, the 95% confidence interval for the degree of day to day variability was +/- 1 extrastimulus from the mean number required in the three studies. Multiple configurations of induced ventricular tachycardia were frequently observed at repeat studies and occurred in 15 patients (83%). In conclusion, spontaneous day to day variability in mode of induction of ventricular tachycardia in the absence of drugs is common.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of repetition of extrastimuli on sensitivity and reproducibility of mode of induction of ventricular tachycardia by programmed stimulation.

This study examined the effect of repeating the delivery of a programmed extrastimulus that previously failed to induce ventricular tachycardia, without the usual practice of concurrently altering other stimulation variables such as pacing site or basic cycle length. The impact of such repetition on both sensitivity and day to day variability in mode of arrhythmia induction was assessed in 24 patients with documented sustained ventricular tachycardia or fibrillation. Programmed stimulation in the absence of drugs was performed in each patient on 3 separate days. In the first 12 patients, each extrastimulus was scanned through diastole to refractoriness four times if no ventricular tachyarrhythmia was induced (longitudinal repetition); in the second 12 patients, each extrastimulus was delivered four times at a particular coupling interval before the interval was decreased in 10 ms steps to a closer coupling interval (lateral repetition). Day to day reproducibility of the mode of arrhythmia induction was compared with reproducibility in a control group of 18 similar patients studied previously on 3 separate days without repetition. A sustained ventricular tachyarrhythmia was inducible in all studies with four or fewer extrastimuli. In the group studied with longitudinal repetition, there was a 25% increased yield of induced ventricular tachycardia due solely to repetition of each extrastimulus scan, and the 95% confidence limit for tachycardia induction with any extrastimulus was achieved by delivering that extrastimulus three times. In the group studied with lateral repetition, there was also an increased yield of induced ventricular tachycardia at any extrastimulus coupling interval achieved by repetitive delivery of that coupling interval.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of immediate versus day to day variability of ventricular tachycardia induction by programmed stimulation.

The use of programmed stimulation to assess long-term oral antiarrhythmic drug efficacy for ventricular tachycardia is complicated by the fact that mode of ventricular tachycardia induction varies from day to day in the absence of drug therapy. The purpose of this prospective study was to assess whether mode of ventricular tachycardia induction is more reproducible within one study than from day to day. Thirty-nine consecutive patients with documented sustained ventricular tachyarrhythmias secondary to coronary artery disease underwent three inductions of ventricular tachycardia at 15 min intervals in the absence of drug therapy. A stimulation protocol in which the only major variable was the number of extrastimuli required for tachycardia induction was used. Subsequent day to day variability in mode of tachycardia induction was also assessed in the same patients at two further drug-free inductions at intervals of 5 +/- 2 days. The number of extrastimuli required for tachycardia induction was significantly more reproducible at the immediate repeat studies than from day to day (69% of patients versus 31%, p less than 0.01). From these data, probability tables were derived that show the likelihood that changes in inducibility at subsequent tachycardia inductions are due to chance. The QRS configuration of induced ventricular tachycardia was also more reproducible at the immediate studies (64% versus 26%, p less than 0.01). Basic electrophysiologic and stimulation variables differed over a significantly wider range from day to day than at the immediate studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure to replicate the Scott et al. finding of reversed ear dominance in the Native American Navajo.

The apparent universality of left hemisphere language specialization in neurologically normal right-handed persons has been questioned by Scott et al. (Neuropsychologia 17, 89-92, 1979). They found that Native American Navajos had a significant left ear advantage on the dichotic C-V task, while Anglo Ss had a right ear advantage. We attempted to replicate this finding with essentially the same task, more Ss and four times as many trials. Results showed a very clear right ear advantage in Navajos. While we had previously questioned the Scott et al. conclusion on the basis of visual laterality test findings, present results directly contradict those of Scott et al.

Language laterality in Navajo reservation children: dichotic test results depend on the language context of the testing.

Language lateralization in 40 Navajo and 20 Anglo fifth graders was assessed via the Dichotic Consonant-Vowel Task (DCVT). One group of Navajo children was tested by an experimenter who spoke only Navajo with them. The other Navajo group and the Anglo group were tested by an experimenter who spoke only English to them. Strong right ear advantages (REAs) were obtained for the Anglo group and for the Navajo group tested by the Navajo-speaking experimenter. The Navajo group tested by the English-speaking experimenter showed minimal, nonsignificant REAs. Previous findings of an absence of REAs in Native American children failed to consider the possibility that this might occur only when the experimenter does not speak the dominant language of the children. Our results are not consistent with the view that Native Americans are more right hemisphere dominant as a function of an "appositional" mode of language and thought.

Morbidity effects on productivity and profitability of stocker cattle grazing in the Southern Plains.

Effects of bovine respiratory disease (BRD) on stocker cattle systems are unknown under extensive rangeland environments. Three experiments were conducted to test the hypothesis that BRD-based morbidity is a major factor affecting the productivity and profitability of stocker cattle grazing Southern Plains rangelands. In Exp. 1 (658 male calves; average BW = 231 kg), 17% of the cattle were treated for BRD <8 d, 6% for 8 to 14 d, and 8% for >14 d. Morbid cattle had lower ADG than did healthy cattle (P < 0.10). Cattle requiring 14 d of pharmaceutical therapy gained less than cattle having <14 d therapy (P < 0.01). In Exp. 2, (279 steers and bulls; average BW = 216 kg), the ADG by steers (0.74 kg x animal(-1) x d(-1)) was greater (P < 0.05) than by bulls castrated after arrival (0.64 kg x animal(-1) x d(-1)). Castration after arrival led to a 13.5% loss in daily gain and a 10.3% loss in season-long gain. More (P < 0.05) bulls castrated after arrival (60%) were morbid compared with steers (28%). In Exp. 3, 633 heifers (average BW = 251 kg) were used to test the effects of morbidity on weight gain and reproduction. Heifers with lower initial weights exhibited increased (P < 0.05) morbidity. Heifers requiring two or more antibiotic treatments gained 0.03 kg/d less (P < 0.10) than did healthy heifers and had lower (P < 0.05) conception rates (66 vs. 81%). Conception rate in twice-treated heifers was 19% less than healthy heifers. Morbid heifers conceived 0.6 mo later (P < 0.05) than healthy heifers. Under the conditions of Exp. 1 and Exp. 2, morbidity decreased net returns 9.7 to 21.3% per animal. Adjusted gross returns per animal in Exp. 3 for replacement heifers were 3 to 7.8% less for morbid heifers.

Haptic identification of rotated letters using the left or right hand.

The present study investigated the effects of the use of the left and right hands on haptic identification of letters which were presented in either a normal (0 degrees rotation), downward (90 degrees clockwise rotation), upside down (180 degrees rotation), or facing upward (270 degrees rotation) position. Each of the 80 right-handed subjects was given five series of randomly ordered presentations of sets of 8 letters of the alphabet. The subjects were asked to feel and then name each letter correctly as quickly but as accurately as possible. Times showed no effect of hand, but significant effects were found for different sets of letters, degree of rotation and a significant decrease in identification time was observed across the five series. Interactions occurred between hand and rotation as well as set and rotation. Errors showed a significant interaction of hand with degree of rotation; the right was superior at 0 degrees but the left was superior at 90 degrees. The results were discussed in terms of hypotheses of hemisphere function, mental rotation, and stimulus familiarity.