José Antonio García Rodríguez

Role of Programmed Electrical Stimulation of the Heart in Risk Stratification Post‐Myocardial Infarction

Programmed electrical stimulation (PES) of the heart was evaluated as a method of identifying patients at risk of sudden death post‐myocardial infarction (post‐MI). Eighty‐four patients (mean age, 56 ± 10 years) underwent PES 6 to 8 weeks post‐MI. PES was performed at the right ventricular apex at twice diastolic threshold. Prior to stimulation patients were studied with exercise stress testing, 24‐hour Holter monitoring and radionuclide ejection fraction. The patients were placed into two groups, according to their responses to electrical stimulation. Group 1: 65 patients in whom no arrhythmias were induced or who had repetitive responses that lasted Jess than six cycles; Group 2:19 patients in whom ventricular tachycardia was induced. At the end of follow‐up (20 ± 9 months) six patients from Group 1 had died. Complex ventricular ectopy and ventricular tachycardia were more frequently detected on Holter in Group 2 (9/19) than in Group 1 (14/65) (p < 0.03). The results of exercise testing and radionuclide ejection fraction did not correlate with the response to PES. However all but one of the patients who died had a left ventricular ejection fraction (LVEEJ under 40% and four out of six patients had ventricular tachycardia on Holter monitor. We draw the conclusion that PES did not contribute to the identification of high‐risk patients post‐MI, as none of the 19 patients in whom ventricular tachycardia was induced died during follow‐up. In addition, high‐risk patients were characterized by poor ventricular function and complex ventricular arrhythmias on Holter recording.

Monte-Carlo technique for uncertainty evaluation of gauge block calibration using laser interferometry

Gauge block calibration for dimensional metrology standards are made by means of laser interferometry procedures and uncertainty is typically calculated using the recommendations of the Guide to the Expression of Uncertainty in Measurement (GUM). This method does not appear very useful for complicated and non-linear model equations as occurs in gauge block interferometry. Under this context, a Monte Carlo method is applied to evaluate the uncertainty of the model function. Input distributions are generated taking into account the value of the physical magnitudes, type of probability distribution and standard uncertainty value. These values are particularized for the room conditions and instruments used in the Metrology Laboratory of Galicia (LOMG), Spain. Obtained results show that the output data fit correctly to a normal distribution (Central Limit Theorems hypothesis can be assumed) and show the potentiality of applying Monte Carlo methods to the uncertainty evaluation in gauge block interferometry.