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Biomedical subjects

P A Tibbits

Publications and source records attributed to P A Tibbits.

7 recordsLinked to original sources
PubMed1987

Serial acquisition of data to predict one-year mortality rate after acute myocardial infarction.

Eight hundred sixty-six patients with acute myocardial infarction (AMI) were enrolled in a prospective study to determine optimal predictors of long-term prognosis. During 12-month (mean) follow-up there were 65 cardiac deaths and 21 nonfatal repeat AMIs. Twenty-nine variables (from the history, physical examination, serum chemistries, ambulatory monitor, radionuclide ventriculogram and exercise test) were arranged into in 5 sequential groups according to the time at which results became available during hospitalization. Multivariate analysis (logistic regression) and receiver-operator characteristic curves were used to assess improvement in prediction of mortality or repeat AMI by addition of each group of variables. The first group of independent predictors included rales, left bundle branch block and symptom status at 1 month before admission. Addition of information from ambulatory monitoring or serum chemistry did not improve prediction. Radionuclide ejection fraction made a statistically significant, independent contribution to mortality prediction. Of the final group the only exercise test variable that contributed independently to prediction was whether the patients took the test. However, receiver-operator characteristic curves showed that improvement in sensitivity and specificity by addition of information from the radionuclide scan and exercise test was clinically insignificant. Our results imply that costly tests after AMI should be reserved for specific indications and not applied universally for prognosis. Although these tests were highly predictive individually, each test generally added little to preexisting prognostic information.

Follow-Up Studies↗
PubMed1985

Right ventricular ejection fraction measured by first-pass intravenous krypton-81m: reproducibility and comparison with technetium-99m.

Study of the effects of various diseases and therapeutic manipulation of pulmonary vascular resistance on the right ventricle has been restricted by methodologic limitations. The radioactive gas in solution, krypton-81m was used to study the right ventricle and the technique was compared with a technetium-99m method. In 22 subjects, first-pass krypton-81m right ventricular ejection fraction, acquired both in list mode and electrocardiogram-gated frame mode, correlated well (r = 0.81 and 0.86, respectively, p less than 0.01) with that determined by technetium-99m first-pass studies over a broad range of ventricular function. The reproducibility of the technique was excellent (r = 0.84 and 0.95 for each acquisition mode, respectively). Krypton-81m first-pass studies provide accurate and reproducible estimates of right ventricular function. Use of krypton allows multiple measurements, with or without perturbations, over a short period of time.

Heart Ventricles↗
PubMed1983

Clinical and electrophysiologic assessment of oral flecainide acetate for recurrent ventricular tachycardia: evidence for exacerbation of electrical instability.

Four patients with recurrent, symptomatic ventricular tachycardia (VT) refractory to conventional antiarrhythmic agents were given flecainide acetate to control arrhythmias. Ventricular stimulation studies were performed in all patients before and 1 to 2 weeks after initiation of oral flecainide therapy. Before flecainide, all patients had easily inducible VT that was morphologically identical to their spontaneously occurring arrhythmia. Flecainide increased the mean PR interval (from 0.17 to 0.23 second), mean QRS duration (from 0.08 to 0.12 second) and mean ventricular effective refractory period (from 235 to 270 ms). Mean corrected QT interval did not change (0.51 second). In 2 patients, VT could not be induced during follow-up stimulation studies. One patient has been treated successfully for 10 months, with no clinically apparent episodes of VT. One patient had recurrent nonsustained VT and was withdrawn from the study as a treatment failure after 6 months of therapy. Two patients had inducible, polymorphous VT that degenerated into ventricular fibrillation that required 2 countershocks before the successful restoration of sinus rhythm. One of these patients had VT stimulation by atrial pacing at a cycle length of 320 ms in the postflecainide electrophysiologic study. VT was not inducible by atrial pacing during this patient's preflecainide study. Thus, sustained oral flecainide administration may precipitate serious electrical instability in susceptible patients, and ventricular stimulation studies and other clinical variables may be useful in selecting patients with recurrent VT who may benefit or may be endangered by oral flecainide therapy.

Administration, Oral↗