Spectral Analysis of Blood Pressure Variability in Atrial Fibrillation

Abstract Atrial fibrillation (AF) is a common arrhythmia characterized by desynchronization of atrial electrical activity causing a consequent irregular ventricular response. Blood pressure (BP) fluctuates in a complex mode composed of both short-term and long-term variability. In AF, the beat-to-beat variation of BP is increased because of variations in filling time and in contractility. However, a few studies have analysed short-term BP variations in AF being the interest mainly addressed to 24-hour variations. Aim of this study was to describe BP variability spectrum during AF in short-term recordings. Fifteen patients, referred for electrical cardioversion, with persistent AF were included in the study. An harmonic LF component was observable in all patients' BP spectra, even during AF, i.e., in presence of a very irregular RR series. Introduction Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice and it is characterized by an irregular atrial depolarization that causes an irregular but not completely random ventricular rhythm as well In AF, the beat-to-beat variation of blood pressure (BP) is increased because of variations in filling time and in contractility. Only a few studies Aim of the present study was to describe BP variability spectrum during AF in short-term recordings in patients with persistent AF. Methods Study protocol Fifteen patients (9 male, mean age 67 ± 7 years) with persistent AF (median duration 3 months; range 1-12 months) were included in the study. Three orthogonal leads, a periodic reference arterial pressure measurement and a continuous beat-to-beat noninvasive recordings of arterial pressure were obtained with a Task Force Monitor (CNSystem; Austria) recording system. Surface ECG and BP signals were recorded for about 10 minutes before electrical cardioversion. The sampling frequency was 1 kHz for the ECG signal and 100 Hz for the continuous arterial pressure recording. Electrical cardioversion was performed in fasting state during deep sedation with intravenous propofol (1-2 mg/Kg). Biphasic DC shock (Life Pack 12 defibrillator, Medtronic Inc., Minneapolis, USA) was delivered with rising energies when needed, starting from 100 J (single shock in almost all cases). Series extraction An automatic QRS detection algorithm was used to locate R waves on the ECG and an interactive graphic interface allowed the operator to visually identify and correct missed/misdetected beats. During AF, the search for the systolic values cannot be performed looking for the maximum after the R wave, a

Identification of atrial fibrillation episodes using a camera as contactless sensor

Identification of paroxysmal atrial fibrillation (AF) can be difficult and undiagnosed AF patients are at high risk of cardioembolic stroke or other complications associated with AF. The aim of this study is to analyze the video photoplethysmografic (vPPG) signal obtained from a videocamera to explore the possibility of discriminating AF from normal sinus rhythm (NSR) and other arrhythmias (ARR). We acquired 24 3-min long face-videos (8 for each rhythm) using an industrial camera. After preprocessing, vPPG signal was extracted using zero-phase component analysis. Diastolic minima were detected and inter-diastolic series obtained. The signals were characterized by time domain indexes, the sample entropy (SampEn); and the shape similarity index (ShapeSim). The time domain indexes and ShapeSim are significantly different when comparing the group of patients with AF or ARR to subjects in NSR. SampEn is significantly higher in AF than in NSR and ARR. From the shape analysis, it can be noted that waves in NSR are more similar than in AF. These preliminary results show the capability of different indexes to capture differences among AF, ARR and NSR. Further studies will help in assessing the performance of the vPPG signal to screen general population

Analysis of T-Wave Alternans in ambulatory recordings using the ADTWA index

Implantable cardioverter defibrillators (ICD) are the most effective way of preventing sudden cardiac death (SCD). However, the implantation of an ICD is an invasive procedure with associated risks and a high cost. Therefore, it is necessary to determine non-invasive risk markers that identify patients at a higher risk of suffering malignant arrhytmias. One of the most promising non-invasive indices is T-wave alternans (TWA). This work assesses T-wave alternans using the Amplitude of Dominant T-Wave Alternans (ADTWA), that is derived from the dominant T wave associated to a number of consecutive beats. Data from 650 patients with heart failure enrolled in the MUSIC study were analyzed. ADTWA have higher values increasing heart rate. ADTWA was also significantly higher in SCD patients than in survivors (survivors vs. SCD: 6.60\ub11.98 vs. 7.55\ub12.53, p=0.01). ADTWA seems a promising index to identify patients with heart failure at higher risk of SCD