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Papers by Alejandro Navarro
Revista Española de Cardiología, 2006
Pacing and Clinical Electrophysiology, 2003
CHORRO, F.J., ET AL.: Significance of the Morphological Patterns of Electrograms Recorded During ... more CHORRO, F.J., ET AL.: Significance of the Morphological Patterns of Electrograms Recorded During Ventricular Fibrillation: An Experimental Study. Mapping techniques are used to study the significance of the morphological patterns of the electrograms (EGMs) obtained during VF in an experimental model. In 24 isolated rabbit heart preparations recordings were made of activation during VF using a multiple electrode (121 unipolar electrodes) positioned on the lateral wall of the left ventricle. Three types of activation maps were selected: (A) with functional block of an activation front; (B) with epicardial breakthrough; and (C) with a single broad wavefront without block lines. The EGMs were classified as negative (Q), positivenegative with a predominance of the negative (rS) or positive wave (Rs), and positive (R). In 60 type A maps the morphology in the zone limiting the block line corresponded to an R wave in 55 (92%) cases and to Rs in 5 (8%) cases. In 67 type B maps, the EGM in the earliest activation zone most often showed Q wave morphology (48 [72%] cases), followed by rS (18 [27%] cases), and Rs morphology (1 [1%] case); in no case was R wave morphology seen. Finally, in 78 type C maps the morphology corresponded to a Q wave in 15 (19%) cases, rS in 38 (49%), Rs in 24 (31%), and R in a 1 (1%) case. The differences between the three types of maps were significant (P < 0.0001). Q wave EGM sensitivity for indicating the existence of an epicardial breakthrough pattern was 72%, with a specificity of 89%, and positive and negative predictive values of 76% and 87%, respectively. R wave EGM sensitivity for indicating the existence of conduction block was 92%, with a specificity of 99%, and positive and negative predictive values of 98% and 97%, respectively. R wave morphology is highly sensitive and specific for indicating conduction block. EGM recordings with initial positivity predominance are infrequent in the earliest activation zones of epicardial breakthrough during VF. The recording of the EGM with Q wave morphology indicates centrifugal activation from the explored zone.
International Journal of Cardiology, 2001
ST-segment elevation on Q-leads after an acute myocardial infarction is related to a greater infa... more ST-segment elevation on Q-leads after an acute myocardial infarction is related to a greater infarct size. The meaning of a further exercise-induced ST-segment elevation in these patients has not been analyzed. Thirty-six patients with ST-segment elevation on Q-leads were studied after a first acute myocardial infarction. Exercise testing and cardiac catheterization were performed at the first week. Left ventricular volumes (ml/m(2)); the extent of abnormal wall motion (AWM: chords); contractile reserve (AWM improvement with low dose dobutamine) and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 20 patients; systolic recovery (AWM improvement), left ventricular volumes and coronary patency were again evaluated. Patients with exercise-induced ST-segment elevation in two or more Q-leads (n=21) showed lesser contractile reserve (6+/-6 vs. 12+/-7 chords, P=0.01) than patients without exercise-induced ST-segment elevation (n=13). AWM (F=8.1) and absence of exercise-induced ST-segment elevation (F=9.5; positive predictive value: 80%; negative predictive value: 68%) were the only independent predictors of contractile reserve. Nevertheless, this electrocardiographic sign was not related to left ventricular volumes, coronary patency or systolic function and it did not predicted late systolic recovery. In patients with baseline ST-segment elevation on Q-leads an exercise-induced ST-segment elevation is independently related to a lesser contractile reserve but not to the evolution of volumes or regional dysfunction during the first 6 months post-infarction. Therefore, the clinical value of this sign seems to be limited to the non-invasive detection of myocardial viability during the early post-infarction phase.
International Journal of Cardiology, 2001
We analysed QT dispersion within the first 6 months postinfarction, its relationship with the mai... more We analysed QT dispersion within the first 6 months postinfarction, its relationship with the main established risk stratifiers and its clinical value. In 55 patients with a first Q-wave myocardial infarction the 12-lead electrocardiogram was scanned and digitised for analysis of QT dispersion (QT maximum-QT minimum) at first day (72 [61-96] ms), first week (69 [47-90] ms), first month (67 [46-88] ms) and sixth month (47 [40-74] ms; P<0.0001 vs. first day). Cardiac catheterization was performed at first week and at sixth month; QT dispersion was not related to ejection fraction, left ventricular volumes, infarct related artery status or contractile reserve (improvement of the infarcted area with low-dose dobutamine); no relation was found between QT dispersion decrease from first week to sixth month with regional systolic function improvement. Finally, during a mean follow-up period of 35+/-22 months QT dispersion was not independently related to clinical events. QT dispersion decreases progressively during the first months after myocardial infarction. These changes should be taken into account to define cut-off values of clinical interest in this phase. This variable does not seem related to the classic prognosis predictors. In a nonselected postinfarction population it has a low clinical value.
IEEE Transactions on Power Systems, 2009
This paper is the first of two and presents a planning methodology for low-voltage distribution n... more This paper is the first of two and presents a planning methodology for low-voltage distribution networks. Combined optimization of transformers and associated networks is performed, considering the street layout which connects the different consumers. In this first part, micro-optimization, the planning zone is divided into small zones, mini-zones, which are optimized independently. A repetitive procedure is used in order to locate transformers using clustering techniques. Optimum capacity, customers to be satisfied, the optimum network to be used and losses associated to this network are determined for each location. The methodology is applied over an area of 12.9 km 2 with nearly 20 215 consumers. In the second paper, two macro-optimization methodologies are discussed based on the planning results for each mini-zone, one based on the Voronoi polygons in order to improve load grouping into mini-zones and the other based on the combination of neighboring networks into a single transformer by means of a Tabu search. Finally, the methodology is applied to a zone with a surface of 2118 km 2 and approximately 1 300 000 customers.
Revista Española de Cardiología, 2006
Pacing and Clinical Electrophysiology, 2003
CHORRO, F.J., ET AL.: Significance of the Morphological Patterns of Electrograms Recorded During ... more CHORRO, F.J., ET AL.: Significance of the Morphological Patterns of Electrograms Recorded During Ventricular Fibrillation: An Experimental Study. Mapping techniques are used to study the significance of the morphological patterns of the electrograms (EGMs) obtained during VF in an experimental model. In 24 isolated rabbit heart preparations recordings were made of activation during VF using a multiple electrode (121 unipolar electrodes) positioned on the lateral wall of the left ventricle. Three types of activation maps were selected: (A) with functional block of an activation front; (B) with epicardial breakthrough; and (C) with a single broad wavefront without block lines. The EGMs were classified as negative (Q), positivenegative with a predominance of the negative (rS) or positive wave (Rs), and positive (R). In 60 type A maps the morphology in the zone limiting the block line corresponded to an R wave in 55 (92%) cases and to Rs in 5 (8%) cases. In 67 type B maps, the EGM in the earliest activation zone most often showed Q wave morphology (48 [72%] cases), followed by rS (18 [27%] cases), and Rs morphology (1 [1%] case); in no case was R wave morphology seen. Finally, in 78 type C maps the morphology corresponded to a Q wave in 15 (19%) cases, rS in 38 (49%), Rs in 24 (31%), and R in a 1 (1%) case. The differences between the three types of maps were significant (P < 0.0001). Q wave EGM sensitivity for indicating the existence of an epicardial breakthrough pattern was 72%, with a specificity of 89%, and positive and negative predictive values of 76% and 87%, respectively. R wave EGM sensitivity for indicating the existence of conduction block was 92%, with a specificity of 99%, and positive and negative predictive values of 98% and 97%, respectively. R wave morphology is highly sensitive and specific for indicating conduction block. EGM recordings with initial positivity predominance are infrequent in the earliest activation zones of epicardial breakthrough during VF. The recording of the EGM with Q wave morphology indicates centrifugal activation from the explored zone.
International Journal of Cardiology, 2001
ST-segment elevation on Q-leads after an acute myocardial infarction is related to a greater infa... more ST-segment elevation on Q-leads after an acute myocardial infarction is related to a greater infarct size. The meaning of a further exercise-induced ST-segment elevation in these patients has not been analyzed. Thirty-six patients with ST-segment elevation on Q-leads were studied after a first acute myocardial infarction. Exercise testing and cardiac catheterization were performed at the first week. Left ventricular volumes (ml/m(2)); the extent of abnormal wall motion (AWM: chords); contractile reserve (AWM improvement with low dose dobutamine) and coronary patency in the culprit artery were analyzed. Cardiac catheterization was repeated at the sixth month in 20 patients; systolic recovery (AWM improvement), left ventricular volumes and coronary patency were again evaluated. Patients with exercise-induced ST-segment elevation in two or more Q-leads (n=21) showed lesser contractile reserve (6+/-6 vs. 12+/-7 chords, P=0.01) than patients without exercise-induced ST-segment elevation (n=13). AWM (F=8.1) and absence of exercise-induced ST-segment elevation (F=9.5; positive predictive value: 80%; negative predictive value: 68%) were the only independent predictors of contractile reserve. Nevertheless, this electrocardiographic sign was not related to left ventricular volumes, coronary patency or systolic function and it did not predicted late systolic recovery. In patients with baseline ST-segment elevation on Q-leads an exercise-induced ST-segment elevation is independently related to a lesser contractile reserve but not to the evolution of volumes or regional dysfunction during the first 6 months post-infarction. Therefore, the clinical value of this sign seems to be limited to the non-invasive detection of myocardial viability during the early post-infarction phase.
International Journal of Cardiology, 2001
We analysed QT dispersion within the first 6 months postinfarction, its relationship with the mai... more We analysed QT dispersion within the first 6 months postinfarction, its relationship with the main established risk stratifiers and its clinical value. In 55 patients with a first Q-wave myocardial infarction the 12-lead electrocardiogram was scanned and digitised for analysis of QT dispersion (QT maximum-QT minimum) at first day (72 [61-96] ms), first week (69 [47-90] ms), first month (67 [46-88] ms) and sixth month (47 [40-74] ms; P<0.0001 vs. first day). Cardiac catheterization was performed at first week and at sixth month; QT dispersion was not related to ejection fraction, left ventricular volumes, infarct related artery status or contractile reserve (improvement of the infarcted area with low-dose dobutamine); no relation was found between QT dispersion decrease from first week to sixth month with regional systolic function improvement. Finally, during a mean follow-up period of 35+/-22 months QT dispersion was not independently related to clinical events. QT dispersion decreases progressively during the first months after myocardial infarction. These changes should be taken into account to define cut-off values of clinical interest in this phase. This variable does not seem related to the classic prognosis predictors. In a nonselected postinfarction population it has a low clinical value.
IEEE Transactions on Power Systems, 2009
This paper is the first of two and presents a planning methodology for low-voltage distribution n... more This paper is the first of two and presents a planning methodology for low-voltage distribution networks. Combined optimization of transformers and associated networks is performed, considering the street layout which connects the different consumers. In this first part, micro-optimization, the planning zone is divided into small zones, mini-zones, which are optimized independently. A repetitive procedure is used in order to locate transformers using clustering techniques. Optimum capacity, customers to be satisfied, the optimum network to be used and losses associated to this network are determined for each location. The methodology is applied over an area of 12.9 km 2 with nearly 20 215 consumers. In the second paper, two macro-optimization methodologies are discussed based on the planning results for each mini-zone, one based on the Voronoi polygons in order to improve load grouping into mini-zones and the other based on the combination of neighboring networks into a single transformer by means of a Tabu search. Finally, the methodology is applied to a zone with a surface of 2118 km 2 and approximately 1 300 000 customers.