PubMed Health⌕ Search

Biomedical subjects

Ricardo Morales

Publications and source records attributed to Ricardo Morales.

11 recordsLinked to original sources
PubMed2006

High resistance of atrioventricular node to cryoablation: a great safety margin targeting perinodal arrhythmic substrates.

BACKGROUND: Findings from animal studies and small series of patients support the greater safety of cryoenergy over radiofrequency in the ablation of arrhythmic substrates near the AV node. OBJECTIVES: The purpose of this study was to systematically evaluate the electrophysiologic effects of successive cryoenergy applications to the human AV node in order to better define the safety margin of cryothermal ablation. METHODS: In 15 patients referred for AV nodal ablation, 94 cryomapping and 105 cryoablation applications were delivered through a 6-mm-tip cryothermal ablation catheter (Freezor Xtra, CryoCath) at predefined sites of the triangle of Koch. RESULTS: Temporary effects on AV conduction were observed in 18 (19%) cryomapping and 38 (36%) cryoablation applications. Persistent effects were observed in 9 (9%) cryoablation applications. Persistent effects were associated with cryoablation at the superior third of the triangle of Koch (P = .05), nadir tip temperature < or = -79 degrees C (P = .007), and effect onset time < or =15 seconds (P = .03). Temperature and effect onset time remained statistically significant after multivariate adjustment (P = .01 and .02, respectively). Overall, persistent complete AV block was achieved with cryoenergy in only one patient. In two additional patients, AV conduction remained modified. In the remaining patients, persistent complete AV block was achieved with radiofrequency (median one application per patient). CONCLUSION: The low rate of persistent AV conduction impairment observed with attempts to cryoablate the AV node supports a great safety margin of perinodal cryothermal ablation.

Aged↗
PubMed2006

Thermal chemistry of 1-methyl-1-cyclopentene and methylene cyclopentane on Pt(111) surfaces: evidence for double-bond isomerization.

The thermal chemistry of 1-methyl-1-cyclopentene (1MCp(=)) and methylene cyclopentane (MeCp) was investigated on clean and hydrogen- and deuterium-predosed Pt(111) single-crystal surfaces by temperature-programmed desorption and reflection-absorption infrared spectroscopy. It was found that MeCp isomerizes easily to 1MCp(=) but that the reverse reaction does not occur, at least under our experimental conditions. The MeCp to 1MCp(=) isomerization is aided by the presence of coadsorbed hydrogen, and occurs through the formation of a common 1-methyl-1-cyclopentyl (1MCp-Pt) surface intermediate; that intermediate then undergoes beta-hydride elimination selectively at the ring position to form the 1MCp(=) product. In addition to this isomerization, both 1MCp(=) and MeCp also dehydrogenate on the Pt(111) surface to form a methylcyclopentadiene species, at 325 and 350 K, respectively. A small amount of benzene desorption is detected above 500 K with both reactants, indicative of a ring enlargement reaction. No evidence for the activation of any of the allylic hydrogens was obtained in either molecule.

Journal Article↗
PubMed2006

[Inducibility of atrial arrhythmias after adenosine and isoproterenol infusion in patients referred for atrial fibrillation ablation].

INTRODUCTION AND OBJECTIVES: The identification and ablation of atrial ectopic foci could complement the conventional empirical pulmonary vein approach and may increase the success rate of atrial fibrillation ablation. Although both adenosine and isoproterenol infusion have been reported to induce ectopics, no clear findings on their use during ablation have been published. Our aim was to investigate the utility of these two pharmacologic maneuvers in patients referred for atrial fibrillation ablation. METHODS: The effects of adenosine infusion, isoproterenol infusion, or both were evaluated in 53 patients with refractory atrial fibrillation referred for ablation. Patients were in sinus rhythm during evaluation. RESULTS: Administration of adenosine or isoproterenol induced atrial arrhythmias in 46 patients (87%). Arrhythmia inducibility was similar in those with paroxysmal and those with persistent atrial fibrillation (87% and 86%, respectively). Atrial ectopics alone were induced in 31 patients (65%), atrial tachycardia in four (8%), and atrial fibrillation in 13 (27%). In 10 patients (19%), ectopic foci were located outside the pulmonary veins and subsequently underwent ablation. In 32 of the 46 patients with inducible arrhythmias, only the induced ectopic foci were ablated (mean 1.4 [0.6] targets per patient). The long-term success rate of first procedures was 66%. CONCLUSION: Adenosine and isoproterenol infusion induced atrial ectopics in most patients with drug-refractory atrial fibrillation while they were in sinus rhythm. In almost 20%, the ectopic foci were located outside the pulmonary veins. The effectiveness of induced ectopic-guided ablation observed in our patient series supports the clinical utility of this approach.

Adenosine↗
PubMed2005

[National consensus for management of community acquired pneumonia in adults].

Community acquired pneumonia (CAP) is an acute respiratory infection that affects pulmonary parenchyma, and is caused by community acquired microorganisms. In Chile, pneumonia represents the main cause of death due to infectious diseases and is the third specific cause of mortality in adults. In 1999, an experts committee in representation of "Sociedad Chilena de Enfermedades Respiratorias", presented the first National Guidelines for the Treatment of Adult Community Acquired Pneumonia, mainly based in foreign experience and documents, and adapted it to our National Health System Organization. During the last decade, impressive epidemiological and technological changes have occurred, making the update of guidelines for treatment of NAC by several international scientific societies, necessary. These changes include: new respiratory pathogens that are being identified in CAP and affect adult patients (Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumophila); the increasing senescent adult population that carries multiple co-morbidities; the emergence of antimicrobial resistance among respiratory pathogens associated to massive antibiotic prescription; the development by the pharmaceutical industry of new drugs that are effective for pneumonia treatment (macrolides, ketolides and respiratory fluorquinolones); and the development of new diagnostic techniques for detection of antigens, antibodies, and bacterial DNA by molecular biology, useful in respiratory infections. Based on these antecedents, an Advisory Committee of "Sociedad Chilena de Enfermedades Respiratorias" and "Sociedad Chilena de Infectología" has reviewed the national and international evidence about CAP management in adults in order to update clinical recommendations for our country.

Acute Disease↗
PubMed2005

Errors in pulmonary vein identification and ostia location in the absence of pulmonary vein imaging.

BACKGROUND: A key point in atrial fibrillation (AF) ablation is the ability to identify the pulmonary vein (PVs) and locate their ostia. OBJECTIVES: The purpose of this study was to assess the error margin of PV identification and ostia location in the absence of previous PV imaging. METHODS: This study was performed in patients referred for catheter ablation of AF. PVs were reconstructed before ablation using the CARTO system. The operator tagged the superior and inferior edges of the PV ostia before and after examining the corresponding PV angiograms. The distances between the tagged PV ostia were measured using CARTO software. RESULTS: A total of 105 location estimations of 54 PVs were analyzed. The location of PV ostia without angiography deviated from the angiographic PV ostia by a median of 13 mm (95% confidence interval = 11-14 mm; P < .0001). In 84 of the 105 estimations (80%), wrong tagging was performed inside the PV. A multiple logistic regression revealed that, at sites displaying PV potentials, the left atrial potential amplitude was an independent predictor of location at the angiographic PV ostium (odds ratio 24 [95% confidence interval = 3.7-227] per 1-mV increase). Receiver operator characteristic analysis set the optimal cutoff level at 0.7 mV. Use of this criterion improved the accuracy of PV ostium location by 4 mm (95% confidence interval = 1-6 mm; P = .005). CONCLUSION: Attempts at PV identification and ostia location in the absence of previous PV imaging are subject to a broad error margin.

Adult↗
PubMed2004

Basic assessment of paced activation sequence mapping: implications for practical use.

Some experiences support the use of atrial paced activation sequence mapping, but there is no systematic study assessing its spatial resolution, reproducibility, and influence of pacing parameters. The aim of this study was to evaluate these issues by using a 24-pole catheter positioned at the atrial aspect of the tricuspid and mitral annuli in 15 patients. Bipolar pacing was performed at two sites (right and left atria), 2 cycle lengths (300 and 500 ms) and two outputs (twice and tenfold the late diastolic threshold voltage for 2-ms pulses). The elapsed time between the atrial activation at the two dipoles adjacent to the pacing dipole (activation time [AT]) was measured during each pacing sequence. Changes in cycle length did not modify the AT. The increase in voltage slightly modified the AT (maximum -2 ms at the RA; 95% CI -3 to -1 ms) due to a greater shortening of the conduction time to the dipole located next to the anode. The 95% limits of the intraobserver and interobserver agreements in the AT measurement were -2 to 3 ms and -3 to 3 ms, respectively. The spatial resolution was studied in ten patients by measuring the AT during pacing from each dipole of a 20-pole catheter with a 1-3-1 mm interelectrode distance. The mean AT change was 10 +/- 4 ms per 6 mm of pacing site displacement (95% CI 8-11 ms, range 2.5-20 ms). In conclusion, paced atrial activation sequence analysis is reproducible, accurate, and relatively independent of pacing parameters.

Cardiac Pacing, Artificial↗
PubMed2004

[Intravenous enalapril does not prevent tachycardia-induced acute atrial electrical remodeling].

INTRODUCTION AND OBJECTIVES: Recent clinical studies suggest a potential antiarrhythmic role of angiotensin-converting enzyme inhibitors in preventing atrial fibrillation. Studies in an animal model suggested that these drugs may prevent sustained atrial fibrillation by avoiding the occurrence of detrimental atrial electrical remodeling secondary to temporary episodes of fibrillation or atrial tachycardia. We sought to determine whether intravenous enalaprilat, administered at doses habitually used in clinical practice, prevented pacing-induced acute atrial remodeling. PATIENTS AND METHOD: We analyzed 16 patients with no structural heart disease referred for electrophysiologic study due to supraventricular tachycardia. During the control period, right and left atrial effective refractory periods (ERP) were determined before and after a 10-minute period of rapid atrial pacing (250 ms) to quantitatively assess pacing-induced shortening of the ERP. After full recovery, a bolus dose of enalaprilat (0.015 mg/kg) was infused and the measurement and stimulation procedure repeated to quantify remodeling after enalaprilat administration. RESULTS: In the control period, rapid pacing induced a significant 14% reduction (P<.01) in right atrial ERP and an 8% decrease (P<.01) in left atrial ERP as compared to baseline values. In the enalaprilat period, rapid pacing significantly reduced ERP by 15% in the right chamber (P<.01) and 7% in the left chamber (P<.01). There was no significant difference in the extent or time course of ERP shortening between the control and enalaprilat periods. The number of unintentionally induced atrial fibrillation episodes did not differ significantly between the two periods. CONCLUSIONS: Intravenous enalapril does not avoid the occurrence of pacing-induced acute electrical atrial remodeling, modify its time course, or impede the induction of atrial fibrillation.

Adult↗
PubMed2004

[Learning process for transseptal puncture guided by intracardiac echocardiography].

We prospectively analyzed the learning process for transseptal catheterization guided by intracardiac echocardiography, in 50 patients who underwent radiofrequency ablation for left atrial arrhythmias. In 20 patients the intracardiac echocardiography catheter was positioned in the right atrium to visualize the fossa ovalis and the tenting of the fossa caused by the Brockenbrough needle. In the other 30 patients, the intracardiac echocardiography catheter was positioned so that it impinged upon the fossa ovalis, and the needle was advanced alongside the intracardiac echocardiography catheter under fluoroscopic guidance in two orthogonal projections. In all but one patient, transseptal catheterization was performed successfully on the first attempt. The learning process for transseptal puncture guided by intracardiac echocardiography was uncomplicated, resulting in a procedure that is safe and effective. The intervention is simplified by positioning the echocardiography catheter at the fossa ovalis and using this as a reference point for fluoroscopic monitoring of the progress of the Brockenbrough needle.

Cardiac Catheterization↗
PubMed2004

[Risk stratification and prevention of sudden death in patients with heart failure].

Patients with heart failure can die of progressive refractory heart failure or sudden cardiac death. This article reviews the major clinical predictors of sudden death in patients with heart failure due to left ventricular systolic dysfunction. Although earlier studies have identified many independent univariate predictors of reduced survival in these patients, the positive predictive value of most of them is low. Cardioverter defibrillator implantation has been shown to be the most effective therapy in patients resuscitated after cardiac arrest caused by ventricular fibrillation or poorly tolerated ventricular tachycardia. Low left ventricular ejection fraction, low New York Heart Association functional class, unsustained ventricular tachycardia and inducibility of ventricular arrhythmia in electrophysiological studies may also identify high-risk patients who are candidates for cardioverter defibrillator implantation. The role of amiodarone in preventing sudden death in high-risk patients with heart failure seems to be small. Further studies are needed to improve risk stratification criteria to select patients with heart failure who are candidates for cardioverter defibrillator implantation.

Clinical Trials as Topic↗
PubMed1997

Transesophageal Doppler Analysis of Coronary Sinus Flow A New Method to Assess the Severity of Tricuspid Regurgitation.

BACKGROUND: Severe mitral regurgitation induces reversal of flow in the pulmonary veins. We hypothesized that severe tricuspid regurgitation may disrupt normal coronary sinus flow. The purpose of this study was to analyze the Doppler flow pattern of the coronary sinus and to determine its value in the assessment of the severity of tricuspid regurgitation. METHODS: The coronary sinus flow was analyzed in 70 consecutive patients with some degree of tricuspid regurgitation (27 mild, 14 moderate, and 29 severe) and in 35 patients without tricuspid regurgitation. The coronary sinus flow was obtained by pulsed-Doppler transesophageal echocardiography in a transverse plane, which showed its drainage into the right atrium. RESULTS: The number of patients with adequate studies of the coronary sinus tended to increase with the severity of the tricuspid regurgitation. In patients without or with only mild tricuspid regurgitation the coronary sinus Doppler flow pattern was formed by two negative waves, a late systolic wave and another diastolic one with higher velocity and longer duration. The systolic wave became reversed in 21 (96%) of the patients with severe tricuspid regurgitation. The sensitivity, specificity, and diagnostic accuracy of the presence of a reversed systolic wave in the coronary sinus for the diagnosis of severe tricuspid regurgitation was 95%, 82%, and 80%, respectively. CONCLUSIONS: Significant tricuspid regurgitation modifies the coronary sinus flow pattern as assessed by transesophageal echocardiography. The presence of a reversed systolic flow in the coronary sinus appears to be a reliable new sign with good sensitivity, specificity, and diagnostic accuracy for the diagnosis of severe tricuspid regurgitation.

Journal Article↗