[Show abstract][Hide abstract]ABSTRACT: In this study, the influence of the time-varying mean heart rate (HR) and respiratory frequency in the ability of HR variability (HRV) indices to diagnose coronary artery disease has been studied. The autonomic nervous system activity has been assessed using a methodology that comprises correction of the HRV signal by the time-varying mean HR and redefinition of the classical high-frequency band to include respiratory frequencies above 0.4 Hz. The obtained clinical indices discriminate patients with coronary artery disease from patients with Framingham risk index lower than 5% with a moderate accuracy of 76%, which is lower than the reported in literature for HRV indices. We claim that time-varying mean HR and respiratory frequency, if not taken into account, introduce apparent improvement of diagnostic performance of HRV indices, adding information nonrelated to the autonomic nervous system activity, which is not what HRV is supposed to measure.
Full-text available · Article · Mar 2011 · Journal of electrocardiology
[Show abstract][Hide abstract]ABSTRACT: This paper introduces a new clinical distortion index able to measure the decrease in diagnostic content in compressed echocardiograms. It is calculated using cardiologists' answers to a clinical testbed composed of two types of tests: one blind and the other semi-blind. This index may be used to compare clinical performance among video codecs from a clinical perspective. It can also be used to classify compression rates into useful and useless ranges, thus providing recommendations for echocardiogram compression. A study carried out in order to illustrate its use with Xvid video codec is also presented. The results obtained showed that, for 2D and M modes, the transmission rate should be at least 768 kbit s(-1) and for color Doppler mode and pulsed/continuous Doppler, 256 kbit s(-1).
[Show abstract][Hide abstract]ABSTRACT: In this paper a new wireless decision-support system for haemodialysis patients using heart rate variability (HRV) is presented. The telemedicine system provides connectivity to three participant sites: the general practitioner or nurse at the point of care in the dialysis unit, the remote information and processing server and the cardiologist. At the clinical point of care, the nurse acquires the electrocardiogram (ECG) by using a tailored mobile telecardiology system as well as other relevant physiological information during the clinical procedure, and sends it to the information server. The received information is stored in a secure file server, linked to the patient database and the ECG signal is automatically analyzed by using advanced signal processing tools in the processing server, where a complete clinical results report is generated. The cardiologist can then be linked by means of a web browser to the information server to analyze these results for further clinical diagnosis support. The system has been applied to study HRV in patients undergoing haemodialysis. The clinical report consisted of trends for time- and frequency-domain HRV indexes and other supplementary information automatically calculated, which show the response of the electrical activity of the heart to the dialysis process and that can be helpful for the follow-up of these patients. The telecardiology framework has been successfully evaluated both by the patients and the hospital personnel showing a high compliance with the system. The design and implementation of the telecardiology system have followed the most recent advances in web technologies, biomedical information and storage standards and signal processing techniques. The presented system can be used as a telemedicine tool for clinical diagnosis support and could also be used in other clinical settings.
Full-text available · Article · Jan 2008 · Computer Methods and Programs in Biomedicine
[Show abstract][Hide abstract]ABSTRACT: This paper presents a new approach for ECG compression: to set a variable compression threshold to a value equal to the estimated noise in the ECG block. This approach presents several advantages. On the one hand, it solves the problem of where to place the compression threshold so as to obtain a compressed ECG signal preserving all its diagnostic properties. On the other hand, it provides a flexible threshold that is adapted block to block in order to remove noise from the block at the same time it considerably reduces the data to be stored or transmitted, depending on the application where the compression approach is being used. The new approach has been clinically tested using two kind of MOS tests: blind and semi-blind. Clinical evaluation using records from MIT-BIH Arrhythmia database carried out by three expert cardiologists has shown that the compressed signals produced with this compression approach preserves all their clinical diagnostic properties, being rated as very good, the maximum possible score.
Article · Feb 2007 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
[Show abstract][Hide abstract]ABSTRACT: The use of a tele-echocardiography system requires the use of lossy compression in order to reduce the transmission rates. That's the reason because guaranteeing clinical quality is a highly desired goal. In this paper we introduce two types of tests designed to obtain cardiologists' opinion and translate them to a clinical index. After that, we use this index to establish the recommendable transmission rate when using Xvid video codec in a tele-echocardiography system. Results show that the recommended rate depends on the echocardiography mode: 384 kbps for 2D and M mode, 256 kbps for color Doppler mode and 128 kbps for pulse and continuous Doppler mode.
[Show abstract][Hide abstract]ABSTRACT: Guaranteeing reconstruction quality in ECG lossy compression is essential to obtain signals useful from a clinical point of view. In this paper we discuss the advantages and drawbacks of using two very well known mathematical error measures (PRD and RMS) in order to guarantee quality in threshold wavelet compression codecs that work segmenting the signal into blocks. We use two different error indices to analyze the results: mathematical (RMS global error) and clinical (MOS error). Although mathematical results conclude that guaranteeing RMS is better than PRD, clinical results have shown that the election is subordinated to the signal specific morphology.
Article · Feb 2006 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
[Show abstract][Hide abstract]ABSTRACT: A telecardiology framework for research and clinical decision support is presented. The telemedicine framework provides with connection to three participant sites: the physician at the point-of-care, the remote information centre and the specialized cardiologist. At the point of care, a physician acquires the ECG and other relevant information during the clinical intervention and sends it to the information server. Every ECG file received is stored in the file server, linked to the patient database and processed by the MATLAB-based tools in the processing server, which automatically generates a results report and informs the cardiologist of this fact. The system has been applied in the study of HRV in patients undergoing haemodialysis. In this particular case, the report consists of trends of time-domain and frequency-domain HRV indexes along dialysis and other supplementary information. The framework has been evaluated by patients and hospital personnel, who valued very positively the system. The designed framework has been shown as an efficient and helpful tool for clinical diagnosis support.
[Show abstract][Hide abstract]ABSTRACT: Aspirin is valuable for preventing vascular events, but information about ulcer frequency is necessary to inform risk-benefit decisions in individual patients.
To determine ulcer prevalence and incidence in a population representative of those given aspirin therapy and evaluate risk predictors.
Patients taking aspirin 75-325 mg daily were recruited from four countries. Exclusions included use of gastroprotectant drugs or other non-steroidal anti-inflammatory drugs. We measured point prevalence of endoscopic ulcers, after quantitating dyspeptic symptoms. Incidence was assessed 3 months later in those eligible to continue (no baseline ulcer or reason for gastroprotectants).
In 187 patients, ulcer prevalence was 11% [95% confidence interval (CI) 6.3-15.1%]. Only 20% had dyspeptic symptoms, not significantly different from patients without ulcer. Ulcer incidence in 113 patients followed for 3 months was 7% (95% CI 2.4-11.8%). Helicobacter pylori infection increased the risk of a duodenal ulcer [odds ratio (OR) 18.5, 95% CI 2.3-149.4], as did age >70 for ulcers in stomach and duodenum combined (OR 3.3, 95% CI 1.3-8.7).
Gastroduodenal ulcers are found in one in 10 patients taking low-dose aspirin, and most are asymptomatic; this needs considering when discussing risks/benefits with patients. Risk factors include older age and H. pylori (for duodenal ulcer).
Full-text available · Article · Dec 2005 · Alimentary Pharmacology & Therapeutics
[Show abstract][Hide abstract]ABSTRACT: Resumen cardiaco (HR) y las frecuencias centrales de dichas bandas. La coherencia media entre la frecuencia central de la banda HFext (0.15 Hz-HR/2) y la frecuencia respiratoria es de 0.64 en los voluntarios, de 0.47 en los sanos y de 0.44 en los isquémicos, y entre la frecuencia central de la banda HFext y el HR de 0.94 en los voluntarios, de 0.92 en los sanos y de 0.83 en los isquémicos, mostrándose un comportamiento diferente según el grupo.
[Show abstract][Hide abstract]ABSTRACT: Observation on heart rate (HR) and heart rate variability (HRV) trends in exercise ECGs lead us to hypothesize that some correlation exists between the evolution of HR and the dominant HRV frequency, which may differ in ischemic and healthy subjects. The ECGs recordings from stress test trials were collected and clustered into four groups: ischemic (positive coronary angiography), non-ischemic, volunteers and healthy (non-ischemic patients with 10 year predicted risk of CAD < 5%, according to the Framingham index). A new index based on the coherence between HR and dominant frequency of the time-frequency HRV was proposed in this work to add diagnostic information to exercise testing, obtaining statistically significant differences (p<10<sup>-5</sup>) between ischemic and rest of the groups.
[Show abstract][Hide abstract]ABSTRACT: Several indexes have been reported to improve the accuracy of exercise test electrocardiogram (ECG) analysis in the diagnosis of coronary artery disease (CAD), compared with the classical ST depression criterion. Some of them combine repolarisation measurements with heart rate (HR) information (such as the so-called ST/HR hysteresis); others are obtained from the depolarisation period (such as the Athens QRS score); finally, there are heart rate variability (HRV) indexes that account for the nervous system activity. The aim of this study was to identify the best exercise ECG indexes for CAD diagnosis. First, a method to automatically estimate repolarisation and depolarisation indexes in the presence of noise during a stress test was developed. The method is divided into three stages: first, a preprocessing step, where QRS detection, filtering and baseline beat rejection are applied to the raw ECG, prior to a weighted averaging; secondly, a post-processing step in which potentially noisy averaged beats are identified and discarded based on their noise variance; finally, the measurement step, in which ECG indexes are computed from the averaged beats. Then, a multivariate discriminant analysis was applied to classify patients referred for the exercise test into two groups: ischaemic (positive coronary angiography) and low-risk (Framingham risk index < 5%). HR-corrected repolarisation indexes improved the sensitivity (SE) and specificity (SP) of the classical exercise test (SE = 90%, SP = 79% against SE = 65%, SP = 66%). Depolarisation indexes also achieved an improvement over ST depression measurements (SE = 78%, SP = 81%). HRV indexes obtained the best classification results in our study population (SE = 94%, SP = 92%) by means of the very high-frequency power (VHF) (0.4-1 Hz) at stress peak.
Full-text available · Article · Sep 2003 · Medical & Biological Engineering & Computing
[Show abstract][Hide abstract]ABSTRACT: To evaluate the risk of upper gastrointestinal bleeding associated with non-aspirin cardiovascular drug therapy, common analgesics and individual nonsteroidal anti-inflammatory drugs (NSAIDs).
The case group was made up of 1122 consecutive patients admitted with bleeding from a peptic lesion. The 2231 control subjects consisted of 1109 patients hospitalized for other reasons and 1122 outpatients from the same geographical area. The relative risk was calculated by unconditional logistic regression after adjusting for confounding factors.
The use of the antiplatelet agent triflusal, and other commonly used cardiovascular drugs, such as beta-receptor blockers and calcium channel blockers, was not associated with increased risk of upper gastrointestinal bleeding. The use of angiotensin-converting enzyme inhibitors reduced the risk of bleeding by 30% (odds ratio 0.7; 95% confidence interval 0.5-0.96). Use of ketorolac (odds ratio 59.4; 95% confidence interval 7.7-454) and piroxicam (odds ratio 19.6; 95% confidence interval 9.3-35.3) carried the highest risk. Use of paracetamol and tramadol was not associated with increased risk of bleeding, but the non-narcotic agent metamizol was associated with a small increase in risk of upper gastrointestinal bleeding (odds ratio 2.6; 95% confidence interval 1.3-5.2).
The use of the antiplatelet agent triflusal and other cardiovascular drugs apart from low-dose aspirin was not associated with gastrointestinal bleeding. The use of either NSAIDs or aspirin increased the risk of gastrointestinal bleeding but, among the analgesics, only metamizol induced a small increase in the risk of gastrointestinal bleeding.
Article · Mar 2003 · European Journal of Gastroenterology & Hepatology
[Show abstract][Hide abstract]ABSTRACT: Most patients with vascular-occlusive diseases benefit from low-dose aspirin (75-325 mg/day). However, they have an increased risk of upper gastrointestinal bleeding (UGIB).
To analyse the incidence and factors influencing the occurrence of UGIB in patients taking low-dose aspirin for the prevention of cardiovascular diseases outside clinical trials.
We studied 903 consecutive patients discharged on low-dose aspirin from the Cardiology Department of a general hospital. Data were collected from medical charts and structured telephone interviews.
Forty-one patients (4.5%) presented with UGIB requiring hospitalization during follow-up (45 +/- 22 months). The incidence of UGIB was uniform during follow-up (1.2 UGIB per 100 patient years). Multivariate analysis showed that a history of peptic ulcer or UGIB [risk ratio: 3.1, 95% CI: (1.5-6.5)] and aspirin dose (per 100 mg/day) [1.8 (1.5-2.9)] was associated with higher risk of UGIB. On the other hand, antisecretory [0.22 (0.07-0.75)] and nitrovasodilator drugs [0.73 (0.55-0.96)] were associated with a decreased risk.
Cardiovascular patients on long-term low-dose aspirin have a stable risk of major UGIB, which is higher than published controlled clinical trials. Antisecretory and nitrovasodilator drugs protect from UGIB, whereas previous peptic ulcer or UGIB and higher doses of aspirin increase the risk.
Article · Dec 2002 · Alimentary Pharmacology & Therapeutics
[Show abstract][Hide abstract]ABSTRACT: In stress test ECG analysis, the so-called ST/HR hysteresis has recently been suggested to improve coronary artery disease (CAD) diagnosis. This parameter is estimated from the ST versus HR diagram including exercise and recovery phases. Unluckily, ST measurements are adversely affected by noise during the test. In this study we propose a method to automatically estimate the ST/HR hysteresis, incorporating multiple stage noise attenuation. The method is based on averaging and rejection of noisy beats. Evaluation is done on simulated exercise test recordings, constructed from real ECG averaged beats adding actual noise from stress test records. Results on a total of 216 different records, with RMS noise levels ranging from 114 to 979 μV, give a reduction in estimation error in the ST/HR diagram of 77.98% (from 168 to 37 μV) in mean and of 76.38% (from 271 to 63 μV) in standard deviation. This method may be considered as a suitable and robust tool for reliable ST/HR hysteresis estimation.
[Show abstract][Hide abstract]ABSTRACT: To evaluate the role of Helicobacter pylori infection and other clinical factors in the risk of upper gastrointestinal bleeding in patients taking low-dose aspirin.
A case-control study was carried out of consecutive current users of low-dose aspirin admitted because of upper gastrointestinal bleeding. Within a cohort of 695 patients with upper gastrointestinal bleeding, 98 patients had taken low-dose aspirin and no other non-steroidal anti-inflammatory drug. Controls were 147 low-dose aspirin users without upper gastrointestinal bleeding of similar age, sex and extent of aspirin use as cases. H. pylori infection was determined by CagA/VacA serology and 13C-urea breath test in all cases and controls. Adjusted odds ratios (OR) are provided.
H. pylori infection was identified as an independent risk factor of upper gastrointestinal bleeding in this population (OR, 4.7; 95% confidence interval (95% CI), 2.0-10.9), but the presence of CagA-positive serology was not. Other risk factors identified were a previous ulcer history (OR, 15.2; 95% CI, 3.8-60.1), alcohol use (OR, 4.2; 95% CI, 1.7-10.4) and use of calcium channel blockers (OR, 2.54; 95% CI, 1.25-5.14). Antisecretory therapy (OR, 0.1; 95% CI, 0.02-0.3) and nitrovasodilators (OR, 0.2; 95% CI, 0.1-0.6) decreased the risk of bleeding.
H. pylori infection is a risk factor for upper gastrointestinal bleeding in low-dose aspirin users, which might have therapeutic implications in high-risk patients.
Full-text available · Article · May 2002 · Alimentary Pharmacology & Therapeutics
[Show abstract][Hide abstract]ABSTRACT: In this work we have analyzed changes in the heart rate variability (HRV) during exercise test comparing them with the ST deviation criteria to improve the diagnostic value of the exercise test. Coronary angiography was considered as gold standard to establish the classification of patients in two groups (ischemic and non-ischemic). ST deviations and HRV indexes were automatically measured and used as independent factors in discriminant analysis to find those more useful to classify both groups. Several approaches were performed starting with different sets of variables. Results showed that by using only the ST indexes it is possible to correctly classify 76% of patients. The inclusion of HRV indexes improves the exactness up to 84%. The very high frequency (0.4 to 1 Hz) at the stress peak has shown to have diagnostic value. Adding the age and the maximum heart rate the exactness goes up to 87.4% (sens. 85.5%, spec. 89.1%), close to that obtained by exercise echocardiography or exercise nuclear imaging.
[Show abstract][Hide abstract]ABSTRACT: In this work, we compared ECG clinical ischemia indexes from
ventricular depolarization, repolarization and heart rate variability
(HRV) measurements during exercise tests. ST segment deviations,
ST/heart-rate hysteresis, Q-, Rand S-wave amplitudes, QRS duration and
HRV indexes were automatically measured. Coronary angiography was used
as the gold standard to include patients in the ischemic group.
Multivariate discriminant analysis was applied to classify the patients.
Results based on classical ST indexes correctly classified 58% of
patients. When depolarization, repolarization and HRV indexes were
jointly considered, the exactness improved to 91% (sensitivity=94%,
specificity=89%). These results are close to those obtained by exercise
echocardiography or exercise nuclear imaging