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Biomedical subjects

Jean T Barbey

Publications and source records attributed to Jean T Barbey.

4 recordsLinked to original sources
PubMed2006

The impact of posture on cardiac repolarization: more than heart rate?

INTRODUCTION: The effect of standing on heart rate and QT is well known but its impact on QTc is less clear. METHODS: Serial supine and standing 12-lead ECGs (seven pairs each day) were recorded from 54 healthy volunteers each day of a three-day period. ECGs were captured digitally and over-read by a cardiologist. RESULTS: A statistically significant shortening of RR (216 ms), QT (40 ms), and decreases in QTc-F (Fridericia) and QTc-LR (Framingham) were demonstrated on standing (8.3 and 6.9 ms, respectively). In contrast, QTc-B (Bazett's) significantly increased by 9.6 ms. Two subject-individualized correction methods were derived using each subject's supine measurements. Both showed significant decreases in QTc of approximately 13-14 ms upon standing. Using the bin analysis method, comparisons between positions using 25 ms interval RR bins revealed significant QT shortening of up to 15 ms upon standing. CONCLUSION: We have demonstrated a postural effect on cardiac repolarization independent of heart rate using two individualized correction methods, as well as QTc-F and QTc-LR, and the bin method. Characterization of postural differences in QT/QTc (other than QTc-B) may provide a safe and inexpensive physiological control to validate the ECG methodology used in clinical trials to assess potential drug-induced QT interval changes.

Electrocardiography↗
PubMed2003

Effect of arsenic trioxide on QT interval in patients with advanced malignancies.

PURPOSE: Arsenic trioxide is an effective treatment for patients with acute promyelocytic leukemia (APL) who have relapsed from or are refractory to all-trans-retinoic acid and anthracycline chemotherapy. Since arsenic can prolong the QT interval and lead to torsade de pointes, a life-threatening ventricular arrhythmia, this retrospective analysis was conducted to determine the degree of QT prolongation in patients treated with arsenic trioxide. PATIENTS AND METHODS: Clinical data and serial ECGs from 99 patients with advanced malignancies who received 170 courses of arsenic trioxide in either a phase I or phase II investigational study were reviewed. RESULTS: Prolonged QT intervals developed in 38 patients (26 patients had intervals >/= 500 milliseconds). Compared with baseline, the heart rate-corrected (QTc) interval was prolonged by 30 to 60 milliseconds in 36.6% of treatment courses, and by more than 60 milliseconds in 35.4% of patients. The degree of prolongation was higher in men than in women during the first course of therapy, and in patients with hypokalemia. In patients receiving multiple courses, QTc intervals returned to pretreatment levels before the second course, signifying that arsenic trioxide does not permanently prolong the QTc interval. One hypokalemic, arsenic trioxide-treated patient with relapsed APL developed asymptomatic torsade de pointes, which resolved spontaneously and did not recur after electrolyte replacement. There were no sudden or arrhythmia-related deaths. CONCLUSION: This analysis shows that arsenic trioxide can prolong the QTc interval. However, with appropriate ECG monitoring and management of electrolytes and concomitant medications, arsenic trioxide can be safely administered in patients with relapsed APL.

Adolescent↗
PubMed2002

Spontaneous adverse event reports of serious ventricular arrhythmias, QT prolongation, syncope, and sudden death in patients treated with cisapride.

CONTEXT: Adverse cardiac events, typically long QT syndrome, have been reported in patients treated with the gastrointestinal prokinetic agent cisapride. OBJECTIVE: To analyze cases of cisapride-associated long QT syndrome and ascertain the degree of confidence in the diagnosis of long QT syndrome and the presence of risk factors. DESIGN: Review of all cases reported to the manufacturer, health authorities, or in the medical literature as of October 1999. METHODS: Before review, specific definitions and a classification scheme were agreed upon. Each case was classified by confidence in the long QT syndrome diagnosis and the presence of recognized risk factors (cofactors) or other medical conditions that were listed as contraindications in the June 1998 United States labeling (labeled conditions). RESULTS: Of 574 cases reviewed, 391 cases of long QT syndrome or isolated QT prolongation were confirmed. Most of these were classified as long QT syndrome with high (145, 37%) or medium (92, 23.5%) confidence in the diagnosis. Recognized cofactors were present in 262 (67%) cases. The proportion of cases with recognized cofactors rose with confidence in the diagnosis (P < 0.001) from 42.2% in the low-confidence group to 68.5% and 82.1% in the medium- and high-confidence groups, respectively. Conversely, the proportion of cases with other labeled conditions decreased with confidence in the diagnosis, from 33.3% for low confidence to 13% and 8.3% for medium and high confidence, respectively. Analysis of cases and prescribing data showed reporting rates decreased in studied months in 1999 compared with the average study period. CONCLUSION: In most cases with high or medium confidence in the diagnosis of cisapride-associated long QT syndrome, recognized cofactors for long QT syndrome were present. The risk of cisapride-related long QT syndrome may be minimized by avoiding cofactors.

Arrhythmias, Cardiac↗