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Biomedical subjects

D L Ross

Publications and source records attributed to D L Ross.

At least 37 records · Page 2Linked to original sources
PubMed1998

Risk to patients from radiation associated with radiofrequency ablation for supraventricular tachycardia.

BACKGROUND: Radiofrequency ablation may be associated with prolonged fluoroscopy times. Previous studies have calculated radiation risks by measuring the radiation dose at a limited number (6) of body sites. This is an inherently inaccurate measure. Our study aimed to quantify more precisely patient-related radiation risks associated with radiofrequency ablation for supraventricular tachycardia. METHODS AND RESULTS: Nine female patients having radiofrequency ablation for supraventricular tachycardia were studied. The radiation dose was determined at 41 body sites in each patient with the use of thermoluminescent dosimeters and was correlated with that measured simultaneously with a Diamentor dose-area product meter. The estimated mean organ doses (mGy) per 60 minutes of fluoroscopy were: lungs 30.8; bone marrow 4.3; left breast 5.1; right breast 3. 5; and thyroid 2.4. From the average organ doses, the estimated mean total lifetime excess risk of a fatal malignancy was 294 per million cases (0.03%) per 60 minutes of fluoroscopy. The risk calculation from the Diamentor dose-area product and thermoluminescent dosimeters were similar, suggesting that radiation dose was measured accurately. The estimated risk of radiation-induced malignancy increased with increasing body mass index (P=0.03). CONCLUSIONS: Prolonged fluoroscopy during radiofrequency ablation may potentially cause a small increase in the lifetime risk of fatal malignancy, with lung malignancy being most likely. This risk is small only with the use of techniques and x-ray equipment optimized to keep radiation as low as possible. The risk is increased in obese patients.

Adult↗
PubMed1998

Lack of benefit of very short basic drive train cycle length or repetition of extrastimulus coupling intervals for induction of ventricular tachycardia.

INTRODUCTION: There are considerable variations of uncertain importance in basic drive train cycle lengths and degree of repetition of extrastimuli used in programmed ventricular stimulation protocols in different laboratories. We compare prospectively three different stimulation protocols to examine the influence of a short basic drive train cycle length and repetition of extrastimuli on induction of ventricular tachycardia. METHODS AND RESULTS: Thirty consecutive patients who had documented ventricular tachycardia or fibrillation based on underlying coronary artery disease underwent programmed ventricular stimulation with each of the three study protocols. Protocol A used a basic drive train cycle length of 400 msec with each extrastimulus coupling interval delivered only once. Protocol B used the same basic drive train cycle length, but with each extrastimulus coupling interval repeated three times before decrementing. Protocol C used 300 msec as the cycle length of basic drive trains without repetition of extrastimuli. Sixty-three percent, 67%, and 63% of the study patients had ventricular tachycardia inducible with protocols A, B, and C, respectively (P = NS). Ventricular fibrillation was induced in 23% of the 30 patients in all three protocols. There were no significant differences in the mean cycle lengths of induced ventricular tachycardia, the number of extrastimuli used, and the coupling interval of the last extrastimulus inducing ventricular tachycardia among the three protocols. CONCLUSION: This study showed no clinical benefit for repetition of extrastimuli that have failed to induce a ventricular tachyarrhythmia during programmed ventricular stimulation. A short basic cycle length of 300 msec was not superior to 400 msec for induction of ventricular tachyarrhythmias. We recommend the use of basic cycle length 400 msec with delivery of each extrastimulus interval only once as the initial protocol for programmed ventricular stimulation.

Aged↗
PubMed1998

Factors associated with excited delirium deaths in police custody.

Increasingly, police respond to confrontations in which the individual demonstrates violent and combative behavior as a result of drug-induced delirium. From medical, legal, and police documents, 61 cases of excited delirium decedents in police custody between 1988 and 1997 are analyzed. In all of the cases, the person fought with and was restrained by police; the person was more likely to die at the scene of the incident or during police transport; and the police were likely to be responding to a disturbance call. In a number of cases, survival time was less than 1 hour. In a majority of cases, acute cocaine toxicity and physical restraint in police custody were contributory to death. The literature is reviewed, analyses of case circumstances are provided, and recommendations for medicolegal investigators and police personnel are discussed.

Cause of Death↗
PubMed1997

Effect of drug load and plate coating on the particle size distribution of a commercial albuterol metered dose inhaler (MDI) determined using the Andersen and Marple-Miller cascade impactors.

PURPOSE: The purpose of this study is to investigate the effect of drug load, the coating of impactor stages, and the design of cascade impactors on albuterol MDIs particle size distribution measurements. The results of the investigation will be used to explain the "loading effect" recently reported. METHODS: Particle size distribution parameters of a commercial albuterol MDI were measured using both Andersen (AI) and Marple-Miller (MMI) Cascade Impactors, where plates were either left uncoated or coated with silicone or glycerin. A previously validated HPLC-EC method was used for the assay of albuterol collected by the impactor and in single spray content determinations. RESULTS: Coating impactor collection plates had an impact on measured MMAD and GSD values for single puff measurements but very little or no effect for the multi puff measurements. Due to particle bounce, the percent of albuterol fine particles deposited in the filter and impactor finer stages (< 1.10 microns in AI and < 1.25 microns in MMI) in uncoated single puff experiments was much higher in comparison to either coated single puff or multi-puff (coated and uncoated) measurements. CONCLUSIONS: Evaluation of drug load and plate coating are necessary to determine whether observed particle size distributions are representative of the generated aerosol or are the result of particle bounce and reentrainment. In order to minimize particle bounce, especially for single puff determinations, it may be useful to apply a thin layer of a sticky coating agent to the surfaces of impactor plates.

Adrenergic beta-Agonists↗
PubMed1997

Efficacy and safety of a new protocol for continuous infusion of midazolam and fentanyl and its effects on patient distress during electrophysiological studies.

Electrophysiological studies are often distressing for patients. We devised a regime of continuous infusion of midazolam and fentanyl during electrophysiological studies without the presence of a specialist anaesthetist. The effects on key hemodynamic and respiratory variables and level of sedation were evaluated in detail in the first 775 patients. The safety of this practice was evaluated in 1,344 consecutive patients. Doses were calculated according to patients' weight and age. A mean total dose of 26 mg of midazolam and 115 mcg of fentanyl were infused. Satisfactory sedation was achieved in 97% of patients. The mean duration of procedure was 188 +/- 90 minutes. Complete amnesia of the procedure was obtained in 87% of patients. Sedation caused clinically insignificant changes in respiratory rate, oxygen saturation, end-tidal CO2 and blood pressure. There were no major complications related to sedation. Upper airway obstruction, usually minor, occurred in 42% and some restlessness in 20% of sedated patients. The assistance of a specialist anesthetist was required in 0.3% of sedated patients for management of restlessness, hypoventilation, or obstructive sleep apnea. The amount of distress experienced by sedated patients (n = 775) was significantly less compared to a previous series of nonsedated patients (n = 775) undergoing electrophysiological studies (P < 0.001). The degree of distress experienced by patients during electrophysiological studies can be reduced significantly by sedation with intravenous midazolam and fentanyl. Continuous infusion is an efficient, safe, and effective way of administering midazolam and fentanyl.

Adolescent↗
PubMed1996

Behavior of late potentials on the body surface during programmed ventricular stimulation.

OBJECTIVES: This study sought to evaluate the behavior of late potentials on the body surface by signal averaging during programmed stimulation and to correlate the findings with the cycle length of induced ventricular tachycardia. BACKGROUND: Clinically relevant late potentials may be concealed within the QRS complex and may be missed by the conventional signal-averaged electrocardiogram (SAECG). In contrast, some late potentials may arise from dead-end pathways or pathways not capable of supporting sustained ventricular tachycardia (VT). It has been shown that durations of late potentials in sinus rhythm correlate poorly with VT cycle length. METHODS: Signal-averaged electrocardiography during sinus rhythm, right ventricular pacing (S1) and introduction of a right ventricular extrastimulus (S2) was performed in 95 patients: 11 patients with a structurally normal heart and no inducible VT (Group I); 44 with a previous myocardial infarction (MI) and no inducible monomorphic VT (Group II); and 40 with a previous MI and inducible monomorphic VT (Group III). RESULTS: The best subset of SAECG variables and the best cut points for each variable to differentiate between patients with and without VT were first established for each rhythm studied. Total duration of the filtered QRS complex (QRSD) was found to be the only independent predictor of inducibility of VT. When late potentials were defined for these criteria (QRSD > OR = 113, > or = 178 and > or = 168 ms for the SAECG during sinus rhythm, S1 and S2, respectively), there was no difference in the incidence of false positive (16% vs. 18%) or false negative (30% vs. 26%) late potentials between sinus rhythm and S1. During S2, there were significantly fewer false positive late potentials (11% vs. 16%) and fewer false negative late potentials (17% vs. 30%) than with sinus rhythm. Compared with sinus rhythm, 31% of the false positive late potentials detected during sinus rhythm were lost, whereas 43% of the false negative late potentials became detectable after S2, resulting in improved sensitivity (83% vs. 70%), specificity (89% vs. 84%) and predictive accuracy (86% vs. 77%, p < 0.05). Among the patients with VT, QRSD during S2 achieved the best correlation with VT cycle length (r = 0.74) and was the only independent predictor of VT cycle length when all SAECG variables were considered. CONCLUSIONS: Late potentials revealed by ventricular extrastimuli but concealed during sinus rhythm may be clinically relevant and may explain some of the false negative late potentials and reduced sensitivity of the conventional SAECG in predicting VT. In contrast, those late potentials that are detected during sinus rhythm but lost after ventricular extrastimuli are often clinically irrelevant and may account for the false positive late potentials and reduced specificity of the conventional SAECG.

Aged↗
PubMed1996

Does sotalol have reverse-use dependence during tachyarrhythmias?

This study assessed the effect of intravenous sotalol on right ventricular effective refractory period at right ventricular pacing rates of 600 and 300 ms cycle length at 3, 6, 9, and approximately 30 minutes after the dose of sotalol. Similar percent increases occurred in the ventricular effective period at the 2 heart rates at all tested times (p >0.2 in each case), and it was concluded that there is no evidence for reverse-use dependence of intravenous sotalol in its effects on right ventricular refractoriness over this range of heart rates.

Aged↗
PubMed1996

Effect of inhalation flow rate on the dosing characteristics of dry powder inhaler (DPI) and metered dose inhaler (MDI) products.

Both the dose delivered from the device and the particle size of the medication are important parameters for inhalation products because they influence the amount of drug that is delivered to the patient's lung. The inspiratory flow rate may vary from dose to dose in a given patient and between patients. The Marple-Miller Cascade Impactor, a new multistage inertial impactor that operates at two flow rates (30 and 60 liters/min) with comparable particle size cut-offs, provides a means to study the effect of inhalation flow rate on the particle size distributions of inhalation products. The medication delivery, mass median aerodynamic diameter (MMAD), and fine particle mass were determined, in a randomized fashion, for albuterol, beclomethasone, budesonide, and terbutaline in both metered dose inhaler (MDI) and dry powder inhaler (DPI) products as a function of flow rate. In all cases, independent of drug or device used, the MDI products had a more reproducible respirable dose than the breath-actuated DPI products tested as a function of inhalation flow rate.

Administration, Inhalation↗
PubMed1995

Localisation of ventricular tachycardia substrates by analysis of the surface QRS recorded during ventricular tachycardia.

BACKGROUND: Analysis of the surface ECG can predict the locations of pacing foci but is of limited value for locating arrhythmogenic substrates causing ventricular tachycardia because of the effects of myocardial infarction, ischaemia, and bundle branch block on ventricular activation. AIM: To determine whether analysis of the initial 60 ms segment of the surface QRS improves the accuracy of the ECG for predicting ventricular tachycardia origin we correlated the locations of 37 arrhythmogenic areas present in 20 patients with the 3D vectors of the ventricular tachycardias generated by each respective area. METHODS: The 3D vector of each ventricular tachycardia morphology was calculated from the integrals of the initial 60 ms of the surface vectorcardiogram and from the entire QRS recorded in each lead of the Frank orthogonal lead vectorcardiogram. Sixty eight-morphologies of ventricular tachycardia were mapped using simultaneous recordings from 60 catheter electrodes. RESULTS: Ventricular tachycardias with 3D vectors directed inferiorly and posteriorly or superiorly and anteriorly were more likely to originate from the septum, P = 0.04, whereas tachycardias directed superiorly and to the right were more likely to originate from the inferior wall and the cardiac apex, P = 0.001. However, the same arrhythmogenic area could generate multiple ventricular tachycardias with different 3D vectors. In addition, ventricular tachycardias with similar 3D vectors were generated by arrhythmogenic areas in the septal, apical and inferior walls. The variances of the mean 3D vectors of ventricular tachycardias originating from each of 12 different cardiac regions were no different when based on the initial 60 ms of the surface QRS than on the entire surface QRS. CONCLUSION: Analysis of the surface ECG provides only an approximate guide to the locations of arrhythmogenic areas generating ventricular tachycardia even when analysis is restricted to the initial forces in the surface QRS. Therefore, detailed mapping is needed to accurately determine the number and location of arrhythmogenic areas.

Bundle-Branch Block↗
PubMed1995

Does the induction of ventricular flutter or fibrillation at electrophysiologic testing after myocardial infarction have any prognostic significance?

This study examines the significance of inducing sustained ventricular fibrillation (VF) or ventricular flutter by programmed stimulation after infarction. Programmed ventricular stimulation was performed for prognostic reasons from the right ventricular apex at twice diastolic threshold using a protocol containing 4 extrastimuli. Of 502 patients tested 11 +/- 4 days after acute infarction, VF was induced in 164 (33%), ventricular flutter in 134 (27%), ventricular tachycardia (VT) in 44 (9%), and no arrhythmia in 160 (32%). All groups were similar in age, sex distribution, and sites of index infarction. Those with inducible VT had a higher incidence of multiple infarctions and a lower mean left ventricular ejection fraction at the time of testing. Without antiarrhythmic drug therapy, 8 patients (18%) with inducible VT experienced spontaneous VT or died instantaneously during the first year of follow-up. By contrast, only 1 (0.6%) patient with inducible VF, 1 (0.7%) with ventricular flutter, and 1 (0.6%) without any inducible arrhythmias experienced similar events in the same period (p < 0.001). By relating the cycle length of the induced monomorphic arrhythmia to later spontaneous electrical events, induced arrhythmias with cycle length as low as 230 ms still identified patients at high risk for spontaneous arrhythmias. Only the induction of sustained monomorphic VT with a cycle length > 230 ms indicates patients with ventricular electrical instability after infarction. The induction of VF or ventricular flutter is a negative test result with no adverse long-term prognostic significance.

Arrhythmias, Cardiac↗
PubMed1995

Rapid intravenous infusion of d-1 sotalol: time to onset of effects on ventricular refractoriness, and safety.

d-1 sotalol is one of the most effective antiarrhythmic agents currently available for ventricular tachyarrhythmias, but the recommended infusion rate of 10-20 min is too slow for rapid pharmacological termination of sustained ventricular tachycardia (VT) or for use during cardiac arrest. The safety of the drug and time lag from its rapid administration to onset of significant effects on ventricular refractoriness is unknown. One hundred and nine patients with a history of spontaneous and inducible sustained ventricular tachyarrhythmias were studied. d-1 sotalol (1.5 mg.kg-1) was infused over 5 min in the first 57 patients (mean age 61 +/- 13 years, mean ejection fraction 37 +/- 15%, range 15-70%). d-1 sotalol was then given over 1 min in the next 52 patients (mean age 61 +/- 12 years, mean ejection fraction 35 +/- 11%, range 18-58%). The time course of change in right ventricular effective refractory period (RVERP) was measured in 15 consecutive patients following the 5 min infusion and in all 52 patients following the bolus injection. Following the 5 min infusion, RVERP increased rapidly from a baseline of 231 +/- 17 ms, reaching a plateau of 268 +/- 23 ms at 10 min. Following the 1 min injection, RVERP increased virtually immediately from a baseline of 237 +/- 25 ms to reach a plateau of 271 +/- 31 ms at 5 min. Two patients (one in each group) developed symptomatic hypotension; both responded to volume replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Radiation exposure to patient and operator during radiofrequency ablation for supraventricular tachycardia.

BACKGROUND: Radiofrequency (RF) ablation has become the primary method of treatment for supraventricular tachycardia and often requires prolonged fluoroscopy times. AIM: To quantitate radiation exposure to patient and operator during RF ablation for supraventricular tachycardia. METHODS: Thermoluminescent dosemeters were used to monitor radiation at seven sites. Positions were: patient's thyroid, left scapula, T9 vertebra, right scapula and L4-L5 vertebra and the operator's thyroid and left hand. Monitoring was performed during 22 procedures. Of the patients studied 10 (45%) had atrioventricular junctional re-entry tachycardia (AVJRT) and 12 (55%) had accessory pathway tachycardia. RESULTS: The median fluoroscopy times (minutes) and inter-quartile ranges were 46 (39-65) for AVJRT, 55 (52-60) for left free wall accessory pathway (LFW), 107 (89-140) for septal and 166 (128-176) for RFW pathways. The mean radiation doses (mGy) to the chest wall were 50 for AVJRT, 47 for LFW, 87 for septal and 151 for RFW pathways. The mean radiation to the chest wall of the patient per case was found to be 3.9 times that reported for diagnostic cardiac catheterisation and 1.5 times that reported for angioplasty. CONCLUSIONS: Radiofrequency ablation is associated with significant irradiation of the patient and operator. All precautions should be taken to decrease this exposure. If eye irradiation is assumed to be equal to that to the thyroid, more than 45 procedures per month by a single operator (using ceiling-suspended lead glass shielding) may result in exceeding the recommended dose limit to the eye.

Adult↗
PubMed1995

Simultaneous mapping of the tricuspid and mitral valve annuli at electrophysiological study.

BACKGROUND: Mapping of the right free wall in patients with accessory pathways is difficult compared with that of the left free wall where the coronary sinus permits stable and accurate location of the electrodes used for endocardial mapping. Furthermore, the sequential roving catheter method is less satisfactory than multiple simultaneous electrode recordings spanning the circumference of the valve annulus. A new method for mapping the tricuspid annulus is described. METHODS: Mapping was performed in nine patients with a suspected right free wall accessory pathway or an atriofascicular connection. The tricuspid annulus was mapped using a specially shaped 1 cm interelectrode 10 pole catheter positioned in the right atrium immediately above the annulus. The coronary sinus was mapped with a 5 mm interelectrode 10 pole catheter and a 2 mm interelectrode 10 pole catheter recorded His bundle activity. Catheter positions were confirmed by multiplane fluoroscopy. Electrograms were digitised and recorded simultaneously using a custom computerised mapping system. The position of the multielectrode catheter around the tricuspid annulus relative to that of the coronary arteries was examined by coronary angiography in three patients. RESULTS: Seven right free wall and two posterior septal accessory pathways, and three atriofascicular connections were detected. Ventricular activation adjacent to both valve annuli was mapped in five patients with pre-excitation. The locations of eight of the nine accessory pathways and the three atriofascicular connections were confirmed at operative mapping. One right free wall accessory pathway in a patient with Ebstein's anomaly was not detected at operative mapping. No additional accessory pathways were found at operative mapping or routine 6 month postoperative electrophysiological study, or during a mean (SD) clinical follow up of 22 (7) months. The tricuspid annulus catheter was located during coronary angiography at a mean (SD) of about 2.5 (0.7) cm above and parallel to the right coronary artery in the right atrioventricular groove. CONCLUSIONS: This new catheter technique permits rapid detailed mapping of atrial and ventricular activation around the tricuspid annulus with a resolution of at least < or = % 1 cm, depending on the number and spacing of electrodes in each catheter. The technique was accurate as judged by mapping at surgery. This method is simple and safe compared with that of others for mapping the right free wall via the right coronary artery. It should facilitate detection and ablation of right free wall accessory pathways and atriofascicular connections.

Adolescent↗
PubMed1994

Double-blind trial of lignocaine versus sotalol for acute termination of spontaneous sustained ventricular tachycardia.

The efficacy of antiarrhythmic drugs for terminating sustained ventricular tachycardia (VT) has been disappointing. Lignocaine is the traditional drug but it is not very effective. Sotalol, one of the most effective drugs in suppressing spontaneous or induced VT, should theoretically be useful in this setting. We have compared lignocaine with sotalol for the acute termination of spontaneous sustained VT not causing cardiac arrest in 33 patients (26 males, 7 females, aged 21-90) whose underlying heart disease was old myocardial infarction (28), acute myocardial infarction (2), dilated cardiomyopathy (1), or idiopathic cardiomyopathy (2). Left-ventricular ejection fraction was 35% (range 18-76%). Patients were randomly allocated in a double-blind fashion to lignocaine 100 mg (n = 17) or sotalol 100 mg (n = 16) given intravenously over 5 min. Those with persistent VT 15 min after onset of administration of the first drug were crossed over to the other drug. Sotalol was significantly more effective than lignocaine whether analysed on an intention-to-treat basis (69% vs 18%; 95% confidence interval for absolute difference of 51% 22-80%, p = 0.003) or by analysis limited to the 31 patients with subsequent electrophysiologically proven VT (69% vs 20%). 1 patient in each group required cardioversion after the first drug. Tachycardia persisted in 14 patients in the lignocaine group and 4 in the sotalol group after 15 min. Tachycardia ceased in 7 (50%) patients who crossed over to sotalol, and in 1 patient who crossed over to lignocaine. There was 1 death in each group after the first drug and 1 death after both drugs. We conclude that sotalol was superior to lignocaine for the acute termination of sustained VT. The incidence of adverse effects was similar for the two drugs.

Adult↗
PubMed1994

Can the electrophysiologic study predict treatment outcome in patients with sustained ventricular tachyarrhythmias unrelated to coronary artery disease?

UNLABELLED: Sustained ventricular tachyarrhythmias unrelated to coronary artery disease are uncommon. Currently there are no clear guidelines to aid selection of the most appropriate treatment strategy. Therefore, factors potentially predictive of arrhythmia recurrence and death and the ability of the electrophysiologic study to predict treatment outcome in patients with spontaneous sustained ventricular tachyarrhythmias unrelated to coronary artery disease were examined in 41 medically treated patients followed for a median of 25 (range 1-76) months. Examined factors were: syncope associated with the spontaneous arrhythmia, the morphology and cycle length of the presenting arrhythmia, underlying ventricular function, cardiac pathology, and the results of drug assessment at electrophysiologic study. Random variability in the ease of arrhythmia induction at electrophysiologic study was measured for the group as a whole and was allowed for in prediction of an effective drug response. The 95% confidence intervals for variability in the ease of repeat arrhythmia induction at the same study were < or = 1 extrastimulus and for variability in the ease of repeat arrhythmia inductions at different studies were < or = 2 extrastimuli. Poisson regression models were used for data analysis. Arrhythmia recurrence was most likely in: (1) patients on treatment not predicted to be anti-arrhythmic at electrophysiologic study; (2) patients whose treatment was not assessable at electrophysiologic study because the arrhythmia was not reliably inducible; (3) patients with impaired ventricular function; and (4) re-entered patients whose arrhythmia had recurred on previously allocated therapy. The risk of arrhythmia recurrence decreased with time from hospital assessment. All five deaths occurred in patients with impaired ventricular function. CONCLUSIONS: drug efficacy should be tested at electrophysiologic study in patients with reproducibly inducible clinical arrhythmias. Treatment not proven to be anti-arrhythmic at electrophysiologic study is usually ineffective. Patients with ventricular dysfunction are at highest risk of death from arrhythmia recurrence and should be considered for an implantable defibrillator, arrhythmia surgery, or heart transplantation if drug treatment is not predicted to be effective or is not assessable at electrophysiologic study.

Adolescent↗
PubMed1994

Posterior ("atypical") atrioventricular junctional reentrant tachycardia.

The aim of this study was to characterize a relatively rare type of atrioventricular (AV) junctional reentrant tachycardia (AVJRT). Posterior AVJRT is a type of AV nodal tachycardia in which the site of earliest atrial activation is posterior to the AV node near the coronary sinus orifice. The mechanism of this tachycardia is not well understood. The characteristics of posterior AVJRT (n = 15) were compared with those of anterior ("common") AVJRT (n = 146) and supraventricular tachycardia using single posterior septal accessory pathways (n = 13). During posterior AVJRT, the AH interval was longer than the retrograde conduction time (His to earliest atrial activity) in 11 cases (73%), indicating that these tachycardias were not fast-slow types of AVJRT. The mean ventriculoatrial (VA) interval in posterior AVJRT (93 +/- 41 ms) was longer than in anterior AVJRT (11 +/- 20 ms; p < 0.005), but was similar to that in tachycardias using accessory pathways (106 +/- 16 ms; p = NS). The site of earliest atrial activation during posterior AVJRT was similar to that in tachycardias using accessory pathways. In all cases of accessory pathway-mediated tachycardia, atrial activation could be advanced by ventricular extrastimuli delivered coincident with the His deflection, but atrial activation was not advanced in any case of posterior AVJRT unless the extrastimulus was delivered > 80 ms before the His deflection. Anterograde conduction was similar in the posterior and anterior AVJRT groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Electrophysiologic and histologic effects of dissection of the connections between the atrium and posterior part of the atrioventricular node.

OBJECTIVES: This study was designed to examine the effects of destroying the posterior approaches to the atrioventricular (AV) node. BACKGROUND: Surgical and catheter ablation procedures have been developed for the cure of AV junctional reentrant tachycardia. Some of these destroy the posterior approaches to the AV node. METHODS: Atrioventricular node function and electrical excitation of Koch's triangle and the proximal coronary sinus were examined in 18 dogs. Dissection of the posterior atrionodal connections was performed in 10 dogs and a sham procedure in 8. After 28 to 35 days, repeat electrophysiologic and mapping studies were performed to assess changes in AV node function and the routes of AV and ventriculoatrial (VA) conduction. The AV junction was then examined with light microscopy. RESULTS: The compact AV node was undamaged in eight cases (80%). In two cases minor fibrosis occurred at the posterior limit of the compact node. The right-sided posterior atrionodal connections lying between the coronary sinus orifice and the tricuspid annulus were replaced by scar tissue in all cases, but the left-sided posterior connections and the anterior connections remained intact. Atrioventricular and VA conduction intervals and refractory periods were not altered. Atrioventricular junctional echoes were present in 10 dogs before and in 7 dogs after dissection (p = 0.06). Posterior (slow pathway) retrograde exists from the AV node were present in seven dogs before and in seven dogs after dissection. However, retrograde atrial excitation was altered in four of these seven dogs, so that the site of exit from the AV node was more leftward than it had been preoperatively. The node remained responsive to autonomic blocking drugs postoperatively. Double atrial electrograms similar to slow pathway potentials were found in all dogs. CONCLUSIONS: This procedure ablates the posterior atrionodal connections but rarely damages the compact AV node. Atrioventricular node function is not impaired and the node is not denervated. The mechanism of cure of AV junctional reentrant tachycardia is probably damage to the perinodal atrium. This suggests that part of the slow AV node pathway may lie outside the compact AV node. Dual AV node exits and double atrial electrograms are present in the normal canine heart.

Animals↗