Dissociation and complexation of the fluoroquinolone antimicrobials--an update.
Explore the source record for details and available documents.
Anti-Infective Agents↗
Biomedical subjects
D L Ross
Publications and source records attributed to D L Ross.
Simultaneous 60-electrode mapping of ventricular tachycardia using percutaneous catheters.
OBJECTIVES: We developed a new approach for mapping ventricular tachycardia at electrophysiologic study using simultaneous recordings from up to 60 catheter electrodes. BACKGROUND: Good results for surgical or catheter ablation of ventricular tachycardia are limited by the ability to detect and completely map all of the underlying arrhythmogenic areas. Currently, catheter mapping of all configurations of ventricular tachycardia is impossible or unsatisfactory in at least 60% of patients because of poorly tolerated rapid rates, nonsustained ventricular tachycardia or multiple configurations. METHODS: Twenty-four patients with recurrent ventricular tachycardia refractory to antiarrhythmic drugs were studied using up to six percutaneous decapolar catheters introduced into the ventricles. Left ventricular maps of ventricular tachycardia were achieved by two to three transseptal catheters, two to three transaortic catheters, a coronary sinus catheter and right ventricular catheters. Simultaneous endocardial maps of either right or left ventricles were possible with a resolution of approximately 1 to 2 cm. Up to 60 electrograms were digitized and recorded simultaneously using a custom-computerized mapping system. RESULTS: Successful maps of 73 ventricular tachycardia configurations were obtained in 22 patients. The mapping procedure failed in two patients because of inability to catheterize the left ventricle in one and inability to induce monomorphic ventricular tachycardia in the other. The mean (+/- SD) ventricular tachycardia cycle length was 285 +/- 53 ms (range 215 to 470). A total of 39 separate arrhythmogenic areas (median 1, interquartile [25% to 75%] range 1 to 3/patient) were detected, of which 21 (54%) were in the left ventricular free wall, 17 (44%) were in the ventricular septum, and 1 (2%) was in the right ventricular outflow tract. Ten patients (45%) had at least two arrhythmogenic areas. Thirteen patients subsequently underwent operation. All but one of the arrhythmogenic areas found at surgical mapping had been identified at preoperative catheter mapping. Complications of the preoperative mapping procedure occurred in four patients, with complete resolution in three and minor long-term sequelae in the other. CONCLUSIONS: This technique permits detailed catheter mapping of all types of monomorphic ventricular tachycardias, including those leading to hemodynamic collapse, and should enable better choice and direction of surgical or catheter ablation.
Adult↗
Surgical procedure for the cure of atrioventricular junctional ("AV node") reentrant tachycardia: anatomic and electrophysiologic effects of dissection of the anterior atrionodal connections in a canine model.
OBJECTIVES: This study was undertaken to examine the electrophysiologic and anatomic effects of a surgical procedure that cures the anterior (common) type of atrioventricular (AV) junctional reentrant tachycardia. BACKGROUND: The procedure was designed to interrupt the reentrant circuit at the point of earliest atrial activation during AV junctional reentrant tachycardia, the anterior atrionodal connections. METHODS: Atrioventricular node function and the sequence of electrical excitation of Koch's triangle were examined in 18 dogs. Excitation of Koch's triangle was mapped using a 60-channel mapping system. Surgical dissection was performed in 10 dogs and a sham procedure in 8. After 28 to 35 days, AV node function and the atrial excitation pattern were reassessed. The AV junction was examined using light microscopy. RESULTS: Some degree of AV node damage was visible in all dogs in the dissection group, but it was minor in 40% of cases. The anterior part of the AV node was disconnected from the anterior atrionodal connections in all cases. Anterograde AV node function was mildly impaired. The median AH interval was increased (62 vs. 76 ms [interquartile ranges 48 to 72 and 64 to 104, respectively], p = 0.05), and the AV Wenckebach cycle length was increased (210 vs. 245 ms [interquartile ranges 200 to 230 and 210 to 260, respectively], p = 0.02). The degree of impairment of conduction was directly proportional to the length of dissection (p < 0.05) but not to the degree of damage to the AV node. Ventriculoatrial (VA) conduction was destroyed in 50% of dogs undergoing dissection but in none of those with a sham operation (p < 0.04). The AV node remained responsive to autonomic blocking drugs, and atrial mapping during ventricular pacing revealed that the site of exit from the AV node had been altered. CONCLUSIONS: The atrionodal connections closest to the His bundle are the preferred route of conduction through the AV node during normal AV or VA conduction. Destruction of these connections modifies AV node conduction. The surgical procedure selectively interrupts these connections, and this interruption is likely to be the mechanism of cure.
Animals↗
Comparison of number of extrastimuli versus change in basic cycle length for induction of ventricular tachycardia by programmed ventricular stimulation.
OBJECTIVES: The purpose of this study was to examine the effects of varying basic cycle lengths in a programmed stimulation protocol if up to seven extrastimuli were available at each basic cycle length. BACKGROUND: There is no uniformly accepted protocol for induction of ventricular tachycardia. Most protocols limit the number of extrastimuli to two or three but use several basic cycle lengths. METHODS: Twenty-eight patients with coronary artery disease and documented spontaneous sustained ventricular tachycardia or ventricular fibrillation were studied. In the absence of antiarrhythmic drugs, each patient underwent three inductions of ventricular tachycardia/ventricular fibrillation using sinus rhythm or right ventricular pacing at 600 or 400 ms as the basic cycle length. Up to seven extrastimuli were allowed at each basic cycle length. RESULTS: The maximal yield of clinical tachycardia (96%) was identical for each basic cycle length and was achieved using a maximum of seven, five and four extrastimuli for sinus rhythm and 600 and 400 ms, respectively. A basic cycle length of 400 ms required fewer extrastimuli (2.4 +/- 0.7) to induce ventricular tachycardia/ventricular fibrillation than did 600 ms (2.7 +/- 1.1, p = 0.014) or sinus rhythm (3.4 +/- 1.2, p < 0.001). There was no significant difference in the cycle lengths of the induced ventricular tachycardia, incidence of induced ventricular fibrillation or requirement for direct current countershock. CONCLUSIONS: The use of an adequate number of extrastimuli obviates the need for multiple basic cycle lengths for induction of ventricular tachycardia and does not increase induction of unwanted ventricular fibrillation. If only one basic cycle length is used, the ease of inducibility can be quantified in terms of the number of extrastimuli required. Fewer extrastimuli were required for induction of ventricular tachycardia if a basic cycle length of 400 ms was used. These data favor the use of ventricular pacing at a basic cycle length of 400 ms with up to at least four extrastimuli as the standard stimulation protocol for induction of ventricular tachycardia.
Adult↗
Cardiac electrophysiologic effects of midazolam combined with fentanyl.
Midazolam and fentanyl together produce better sedation, analgesia and amnesia than do either drug alone, but the electrophysiologic effects of the combination are unknown. Twenty patients undergoing electrophysiologic studies for clinical reasons were studied. Blood pressure, heart rate, respiratory rate, oxygen saturation, and standard variables related to atrioventricular and ventriculoatrial conduction, dual pathways, accessory pathway conduction, sinus node function, and the inducibility of tachycardia were examined before and after intravenous injections of midazolam (0.07 +/- 0.03 mg/kg) combined with fentanyl (0.8 +/- 0.4 micrograms/kg). There were no significant changes in the electrophysiologic variables or ease of inducibility of tachycardia. The drugs were well tolerated; they produced minor and clinically unimportant reductions in mean blood pressure (99 +/- 13 to 89 +/- 16 mm Hg; p < 0.001) and respiratory rate (18 +/- 4 to 16 +/- 3 breaths/min; p = 0.05). Excellent sedation was achieved. Major amnesia was reported by 95% of patients. In conclusion, midazolam combined with fentanyl provides safe and effective sedation for electrophysiologic studies without significantly affecting electrophysiologic variables or the inducibility of tachyarrhythmias.
Adult↗
Effect of ventriculotomy on postinfarction ventricular tachycardia in a canine model.
The antiarrhythmic efficacy of ventriculotomy without further resection or ablation was evaluated in 15 dogs with reliably inducible ventricular tachycardia after experimental myocardial infarction. The dogs were placed on cardiopulmonary bypass and assigned to one of two treatment groups: (1) cardiopulmonary bypass only (control) - 5 dogs, (2) ventriculotomy through the infarct scar - 10 dogs. The effects on induction of ventricular tachycardia were evaluated 2 and 4 weeks postoperatively and infarct histology was examined at the termination of the experiment. All of the control dogs maintained inducible ventricular tachycardia postoperatively. In contrast, ventriculotomy abolished arrhythmia induction in 6 of 10 dogs (p < 0.05). Ventriculotomy resulted in destruction of the surviving subepicardial myocardium overlying the infarct, which is a feature of arrhythmogenic areas in this model of postinfarction ventricular tachycardia. In conclusion, inducibility of ventricular tachycardia in this canine model of myocardial infarction is unaffected by thoracotomy and cardiopulmonary bypass, and is therefore well suited to investigation of surgical antiarrhythmic interventions. Ventriculotomy results in subepicardial scarring and is significantly antiarrhythmic. This effect should be taken into account when evaluating any adjunctive procedure in this model.
Animals↗
Characterization of the complexation of fluoroquinolone antimicrobials with metal ions by nuclear magnetic resonance spectroscopy.
The complexation of the fluoroquinolone antimicrobials is important because it has been implicated in reduced oral bioavailability and reduced antimicrobial activity when the drugs are co-administered with antacids or multi-vitamin preparations containing iron. The complexation of two model compounds, lomefloxacin and norflaxacin was studied using NMR. With aluminum ions, exchange between free and bound drug molecules was slow on the NMR time-scale. Two complexes, proposed to have stoichiometries of 2:1 and 3:1 (drug:metal) based on peak widths and variable temperature studies, were observed. The crystal structure of lomefloxacin, which shows intermolecular self association previously reported to be crucial to the drug's mode of action, is also reported. Because the metal ion complexes could not be crystallized, the crystal structure of uncomplexed lomefloxacin together with the NMR data on the aluminum complexes were used in the molecular modelling of the lomefloxacin-aluminum complexes.
Anti-Infective Agents↗
Radiofrequency catheter ablation for supraventricular tachycardias.
Explore the source record for details and available documents.
Catheter Ablation↗
"AV nodal" reentry: Part II: AV nodal, AV junctional, or atrionodal reentry?
The classical model of "atrioventricular (AV) nodal" reentrant tachycardia suggests that the reentrant circuit is entirely within the compact AV node and that AV nodal tissue is present proximal and distal to the circuit. Recent evidence from mapping studies and from examination of the effects of curative procedures, however, suggests that the upper end of the circuit uses perinodal atrial or transitional tissue. Moreover, the anatomical substrate of dual "AV nodal" pathways is likely to be the multiple connections between compact AV node and atrium rather than discrete intranodal pathways. The antegrade slow pathway appears to be situated at the posteroinferior approaches to the AV node in the region between the coronary sinus orifice and the tricuspid annulus. The retrograde fast pathway appears to be situated in the anterior atrionodal connections at the apex of Koch's triangle, close to the His bundle. The lower turnaround point of the circuit is likely to be within the AV node.
Animals↗
Signal-averaged electrocardiogram. Improved identification of patients with ventricular tachycardia using a 28-lead optimal array.
BACKGROUND: Although the signal-averaged ECG (SAECG) is currently the best noninvasive test to identify patients with ventricular tachycardia (VT) following myocardial infarction (MI), it is still a relatively insensitive test. Body surface mapping has improved the sensitivity of ECG in detecting various cardiac diseases. This study applied body surface mapping to the SAECG in the form of a clinically practical, 28-lead optimal array and compared its sensitivity and specificity with those of an orthogonal array. METHODS AND RESULTS: Two hundred twenty-three patients with previous MI (82 with inducible VT) underwent SAECG using 28 surface electrodes from which were obtained a three-lead orthogonal array and a 28-lead optimal array (optimal). From the orthogonal array, two QRS durations (QRSd) were obtained using the combined vector magnitude method (CVM) and the earliest onset to latest offset of the three individually filtered leads (individual). From the optimal array, 28 QRSd were obtained, each defined as the duration from the earliest onset of any of the 28 leads to the offset of each individually filtered lead. QRSd > 120 msec in > or = 3 leads was considered abnormal. For CVM and individual, QRSd of > 120 msec were considered abnormal. While the specificity of each method was comparable (84%, 86%, and 84% for CVM, individual, and optimal, respectively), the sensitivity of optimal (70%) was significantly greater than the sensitivity of CVM (54%) (p = 0.001) or individual (59%) (p = 0.004). The magnitude of improvement in sensitivity, 16% and 15%, respectively, was equal for anterior (n = 120) and inferior (n = 103) infarctions. CONCLUSIONS: Body surface mapping using the 28-lead optimal array significantly improved the sensitivity of the SAECG without loss of specificity. The increased sensitivity was of equal magnitude for inferior and anterior infarctions. The superiority and practicality of the 28-lead optimal array make it worth pursuing as an option for further refinement in SAECG:
Aged↗
High resolution mapping of Koch's triangle using sixty electrodes in humans with atrioventricular junctional (AV nodal) reentrant tachycardia.
BACKGROUND: Recent evidence suggests that atrioventricular junctional reentrant tachycardia (AVJRT) uses a reentrant circuit that involves the atrioventricular (AV) node, the atrionodal connections, and perinodal atrial tissue. Electrogram morphology has been used to target the delivery of radiofrequency energy to the site of the "slow pathway," a component of this reentrant circuit. The aim of this study was to localize precisely the sites of atrionodal connections involved in AVJRT and to examine atrial electrogram morphologies and their spatial distribution over Koch's triangle. METHODS AND RESULTS: Electrical activation of Koch's triangle and the proximal coronary sinus was examined in 13 patients using a 60-point plaque electrode and computerized mapping system. Recordings were made during sinus rhythm (n = 12), left atrial pacing (n = 8), ventricular pacing (n = 12), and AVJRT (n = 12). During sinus rhythm electrical activation approached Koch's triangle and the AV node from the direction of the anterior limbus, activating the anterior part of the triangle before the posterior part. A zone of slow conduction during sinus rhythm was found within Koch's triangle in 64% of patients. The pattern of atrial activation in Koch's triangle during anterograde fast pathway conduction was similar to that seen during anterograde slow pathway conduction. Retrograde fast pathway conduction during ventricular pacing and during anterior (typical) AVJRT caused earliest atrial activation at the apex of Koch's triangle near the AV node-His bundle junction. In individual patients the site of earliest atrial activation was similar for both anterior AVJRT and retrograde fast pathway conduction during ventricular pacing. Retrograde slow pathway conduction during ventricular pacing and during posterior (uncommon or atypical) AVJRT caused earliest atrial activation posterior to the AV node near the orifice of the coronary sinus. This posterior or "slow pathway" exit site was 15 +/- 4 mm from the His bundle. In individual patients the site of earliest atrial activation was similar for both posterior AVJRT and retrograde slow pathway conduction during ventricular pacing. In one patient anterograde and retrograde conduction occurred via separate slow pathways during AVJRT: Complex atrial electrograms with two or more components were observed near the coronary sinus orifice and in the posterior part of Koch's triangle in all cases. These were categorized as either low or high frequency potentials according to the rapidity of the second component of the electrogram. Low frequency potentials were present at the site of earliest atrial excitation during retrograde slow pathway conduction in 5 of 5 cases (100%) and high frequency potentials in 4 of 5 cases (80%). However, both slow and high frequency potentials could be found at sites up to 16 mm from the site of earliest atrial excitation. CONCLUSIONS: At least two distinct groups of atrionodal connections exist. The site of earliest atrial activation during anterior AVJRT is similar to that of fast pathway conduction during ventricular pacing. This site is close to the His bundle-AV node junction. The site of earliest atrial activation during posterior AVJRT is similar to that of slow pathway conduction during ventricular pacing. This site is near the coronary sinus orifice, approximately 15 mm from the His bundle. The anterograde slow pathway appears to be different from the retrograde slow pathway in some patients. Double atrial electrograms are an imprecise guide to the site of earliest atrial excitation during retrograde slow pathway conduction.
Adolescent↗
Dimensions of the triangle of Koch in humans.
Explore the source record for details and available documents.
Atrioventricular Node↗
Lack of effect of midazolam on inducibility of arrhythmias at electrophysiologic study.
Midazolam has several advantages over diazepam as a sedative agent in electrophysiologic studies, but its electrophysiologic effects in humans are unknown. Therefore, its effects were studied in 20 patients undergoing electrophysiologic studies. Electrophysiologic variables were measured before and after administration of intravenous midazolam (5 mg). There were no significant changes in the electrophysiologic variables, apart from a minor decrease in sinus cycle length (711 +/- 124 vs 647 +/- 91 ms; p = 0.005). Ease of inducibility of reentrant tachycardia was not significantly altered by midazolam, and tachycardia remained inducible in all patients. The drug was well-tolerated with no significant side effects, apart from a minor reduction (mean 18 mm Hg) in blood pressure (p less than 0.001). Good amnesic effect was achieved in 16 patients, and most patients preferred it to oral diazepam for sedation during the procedure. It is concluded that midazolam can be used safely in patients undergoing electrophysiologic studies without significantly interfering with electrophysiologic variables or the inducibility of reentrant tachycardias.
Adolescent↗
Accuracy of various methods of localization of the orifice of the coronary sinus at electrophysiologic study.
The coronary sinus (CS) orifice is an important reference point for determining electrode and, thereby, accessory pathway location at electrophysiologic study. The reliability of fluoroscopic landmarks used to identify the CS orifice is not known. This study compared the accuracy of several fluoroscopic landmarks for identifying the CS orifice with the location defined by radiopaque contrast injection of the CS. Forty patients were studied. Radiographic markers of the CS orifice that were examined included: (1) the point at which the CS catheter prolapsed during advancement, (2) the point of maximum convexity of the CS catheter when a superior vena caval approach was used, (3) the right side of the ventricular septum, and (4) the relation to the underlying vertebrae. The least-significant difference method of multiple comparisons was used for statistical analysis. The point at which the CS catheter prolapsed was the most accurate noncontrast method for determining the location of the CS orifice (p less than 0.05), but was possible without the use of excessive force in only 48% of patients. The point of catheter prolapse was a median of 1 mm (range 0 to 11) from the true location of the os. Errors with other examined landmarks ranged up to 3 cm. Identification of the CS orifice is best performed by radiopaque contrast injection. The point of prolapse during catheter advancement in the CS is an accurate alternative when contrast injection is not feasible. Other noncontrast fluoroscopic landmarks are less reliable and are best avoided.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Electrophysiologic studies in patients with unexplained syncope.
This study examined the role of electrophysiologic study in the evaluation of patients with unexplained syncope. The incidence of abnormalities (conduction disease, supraventricular tachycardia, ventricular tachycardia) was compared in patient groups with and without heart disease, and the effect of treatment of these abnormalities on recurrence of syncope was examined. Electrophysiologic study was performed in 111 consecutive patients with syncope, with antiarrhythmic medications being discontinued 1 week prior to study. There was no mortality associated with the procedure and only 9 patients (8%) had complications (groin haematoma, atrial fibrillation or brady-arrhythmias persisting after the procedure). Abnormalities were detected in 31 of 73 patients with heart disease (42%) but in only 6 of 38 patients with no heart disease (16%, P less than 0.01). During follow-up, syncope recurred in 2 of 37 patients (5%) treated because of abnormal findings, compared with a recurrence rate of 24% (18 of 74 patients) in the untreated group (P less than 0.05). Probability of remaining free from syncope at 2 years was 0.94 in the treated group and 0.72 in the untreated group (P less than 0.05). Mortality during follow-up was confined to the heart disease group with 5 of 30 treated patients in this group dying (17%) compared with 3 of 43 untreated patients (7%, P = not significant). Syncope patients with heart disease were thus more likely to have a diagnostically useful study than patients with normal hearts. Treatment directed at correction of abnormalities detected at electrophysiologic study reduced recurrence of syncope but did not significantly affect mortality. Syncope did not appear to be a prelude for sudden death in patients with normal hearts. Electrophysiologic study had no mortality and low morbidity.
Adolescent↗
Outpatient electrophysiological studies.
Explore the source record for details and available documents.
Ambulatory Care↗
Dimensions of the human posterior septal space and coronary sinus.
Accurate anatomic localization of accessory pathways during preoperative electrophysiologic study and during operative mapping depends on a knowledge of the dimensions of the posterior septal space and the left free wall. These dimensions were therefore studied in 48 human cadaver hearts. Mean distance from the coronary sinus orifice to the left margin of the posterior septal space was 2.3 +/- 0.4 cm and mean length of the left free wall was 5.0 +/- 1.0 cm. The posterior septal space at the level of the valve anuli extended a mean of 3.4 +/- 0.5 cm around the epicardium. The width of the posterior septum measured in the coronary sinus was related to heart weight and a combination of body weight and patient age (p less than 0.05). The probability of an accessory pathway being located in the left free wall or the posterior septum during catheter mapping was calculated for various distances from the coronary sinus orifice for adults of different ages and body weights. In adults, accessory pathways located in the proximal 1.5 cm of the coronary sinus are almost always in the posterior septum. Those located between 1.5 and 3 cm from the coronary sinus orifice may be in either the left free wall or the posterior septum, and those located greater than 3 cm from the coronary sinus orifice are almost invariably in the left free wall.
Adolescent↗
Routine programmed electrical stimulation in survivors of acute myocardial infarction for prediction of spontaneous ventricular tachyarrhythmias during follow-up: results, optimal stimulation protocol and cost-effective screening.
Of 3,286 consecutive patients treated for acute myocardial infarction, electrophysiologic testing was performed in 1,209 survivors (37%) free of significant complications at the time of hospital discharge to determine their risk of spontaneous ventricular tachyarrhythmias during follow-up. Sustained monomorphic ventricular tachycardia was inducible by programmed electrical stimulation in 75 (6.2%). Antiarrhythmic therapy was not routinely prescribed regardless of the test results. During the 1st year of follow-up, 14 infarct survivors (19%) with inducible ventricular tachycardia experienced spontaneous ventricular tachycardia or fibrillation in the absence of new ischemia compared with 34 (2.9%) of those without inducible ventricular tachycardia (p less than 0.0005). During the extended follow-up period (median 28 months) of those with inducible ventricular tachycardia, 19 (25%) had a spontaneous electrical event; 37% of these first events were fatal. These results suggest that the most cost-effective strategy for predicting arrhythmia will be obtained by restricting electrophysiologic testing to infarct survivors whose left ventricular ejection fraction is less than 40% and using a stimulation protocol containing four extrastimuli. Electrophysiologic testing is the single best predictor of spontaneous ventricular tachyarrhythmias during follow-up in infarct survivors. The majority (94%) with a negative test benefit from the more reliable reassurance that all is well, whereas the 25% risk of electrical events in those with inducible ventricular tachycardia justifies a prospective trial of effective prophylactic antiarrhythmic interventions.
Anti-Arrhythmia Agents↗