RESUMO
The stroboscopic visibility measure (SVM) is a method used to quantify the stroboscopic effect visibility in general illumination application. SVM has been defined previously based on a limited number of frequencies and participants. To validate and extend SVM, five perception experiments are presented, measuring the visibility threshold of light waveforms modulated at several frequencies, conducted in two different labs. A power function is fitted through the aggregated results to develop a stroboscopic effect contrast threshold function for a "standard observer," which can be used to normalize SVM. An additional experiment shows the dependency on illumination level, extending the validity of SVM to other applications.
RESUMO
BACKGROUND: Factors predicting the maintenance of sinus rhythm (SR) after cardioversion of atrial fibrillation (AF) have not been well defined. Little is known about the impact of the recovery of the left atrial mechanical function (RLAMF) on AF recurrences. AIM: To identify the clinical and echocardiographic predictors of AF recurrences after cardioversion. METHODS: Of 112 consecutive patients (39 females, 73 males, mean age 62.1+/-10.6 years) with AF who underwent successful electrical or pharmacological cardioversion, 50 maintained SR during 6 month follow-up whereas the remaining 62 had a recurrence of AF. Clinical examination and 2D Doppler echocardiography were performed. From the Doppler mitral flow, RLAMF was evaluated 1, 7, and 21 days after cardioversion. RESULTS: Patients with or without AF recurrence did not differ with respect to age, gender, aetiology, duration of AF, LA size and ejection fraction. In the univariate analysis the lack of RLAMF detected 1 day after cardioversion (relative risk - RR=1.15, p<0.01), functional NYHA class II or III (RR=1.86, p<0.005) and a history of AF episodes (RR=2.02, p
