Relationships among owner consideration of euthanasia, caregiver burden, and treatment satisfaction in canine osteoarthritis.

Although diagnosis of osteoarthritis (OA) has been recently linked to euthanasia in dogs, no prior work has examined the roles of caregiver burden or treatment satisfaction in this relationship. We expected that there would be an indirect effect of caregiver burden on the association between consideration of euthanasia and clinical signs of OA, but that this effect would be influenced by owner satisfaction. Cross-sectional online evaluations were completed by 277 owners of dogs with OA recruited through social media. Canine OA-related pain and functional impairment, owner consideration of euthanasia, caregiver burden, and satisfaction were examined. Relationships among OA-related pain and functional impairment, owner consideration of euthanasia, caregiver burden, and satisfaction were statistically significant (P 0.01 for all). Cross-sectional mediation analysis demonstrated a statistically significant indirect effect of caregiver burden on the relationship between consideration of euthanasia and OA-related clinical signs (bias-corrected 95% confidence interval [BC 95% CI], 0.001-0.009), which was significantly moderated by owner satisfaction (BC 95% CI, -0.003 to -0.0002). Findings align with prior work connecting canine OA to euthanasia. The current study extends past research to demonstrate that caregiver burden in the owner may be partially responsible for this relationship. The moderating role of owner satisfaction suggests that optimizing owner impressions of treatment and the veterinary team could attenuate these relationships, potentially decreasing the likelihood of premature euthanasia for dogs with OA.

Reducing occupational distress in veterinary medicine personnel with acceptance and commitment training: a pilot study.

AIMS: To determine whether an educational programme targeting the reaction of veterinary personnel to difficult client interactions reduced burden transfer, stress and burnout in veterinary staff. METHODS: Employees of three small-animal veterinary hospitals in the south-western United States of America were recruited and randomised to intervention (educational programme; n = 16) or control (no intervention; n = 18) groups. Participants of this randomised, parallel arms trial completed pre-programme assessment including the Burden Transfer Inventory (BTI), Perceived Stress Scale, and Copenhagen Burnout Inventory. Assessment was followed by two, group-format educational sessions, based on acceptance and commitment training, tailored to reducing reactivity to difficult veterinary client interactions (intervention group only). After training was completed, both groups were assessed using the same measures and the intervention participants provided use and acceptability ratings. RESULTS: Intervention participants rated the programme as useful and appropriate, and reported that programme techniques were used a median of 43 (min 9, max 68) times during the 2 weeks prior to retesting. Relative to pre-programme scores, median post-programme scores for reaction (subscore of BTI) to difficult client interactions decreased in the intervention group (33 vs. 54; p = 0.047), but not in the control group (51 vs. 59; p = 0.210). Changes in median scores for stress and burnout from pre- to post-programme were non-significant for both groups. CONCLUSIONS: This pilot and feasibility trial showed high rates of acceptability and use by participants, as well as promising reductions in burden transfer. A larger scale clinical trial with follow-up at extended time points is needed to more fully examine the efficacy of this novel programme. CLINICAL RELEVANCE: Preliminary findings suggest this programme may be a useful approach to reducing occupational distress for individuals working in veterinary practice.

Predicting caregiver burden in general veterinary clients: Contribution of companion animal clinical signs and problem behaviors.

Caregiver burden, found in many clients with a chronically or terminally ill companion animal, has been linked to poorer psychosocial function in the client and greater utilization of non-billable veterinary services. To reduce client caregiver burden, its determinants must first be identified. This study examined if companion animal clinical signs and problem behaviors predict veterinary client burden within broader client- and patient-based risk factor models. Data were collected in two phases. Phase 1 included 238 companion animal owners, including those with a sick companion animal (n=119) and matched healthy controls (n=119) recruited online. Phase 2 was comprised of 602 small animal general veterinary hospital clients (n=95 with a sick dog or cat). Participants completed cross-sectional online assessments of caregiver burden, psychosocial resources (social support, active coping, self-mastery), and an item pool of companion animal clinical signs and problem behaviors. Several signs/behaviors correlated with burden, most prominently: weakness, appearing sad/depressed or anxious, appearing to have pain/discomfort, change in personality, frequent urination, and excessive sleeping/lethargy. Within patient-based risk factors, caregiver burden was predicted by frequency of the companion animal's signs/behaviors (P<.01). Within client-based factors, potentially modifiable factors of client reaction to the animal's signs/behaviors (P=.01), and client sense of control (P<.04) predicted burden. Understanding burden may enhance veterinarian-client communication, and is important due to potential downstream effects of client burden, such as higher workload for the veterinarian. Supporting the client's sense of control may help alleviate burden when amelioration of the companion animal's presentation is not feasible.

Genetic variants in SOD2, MPO, and NQO1, and risk of ovarian cancer.

OBJECTIVE: One way in which parity and use of oral contraceptives may protect against ovarian cancer is by preventing inflammation and oxidative stress associated with ovulation. Since the genes superoxide dismutase (SOD2), myeloperoxidase (MPO), and NAD(P)H:quinone oxidoreductase 1 (NQO1) are involved in inflammation and oxidative stress, we investigated whether variants of these genes are associated with risk of ovarian cancer. METHODS: In a hospital-based case-control study, we compared 125 cases and 193 controls with respect to prevalence of (1) the T-->C (val-->ala) substitution at the -9 position in the signal sequence of SOD2; (2) the G-->A substitution at the -463 position in the promoter region of MPO; and (3) the C-->T (pro-->ser) change in exon 6 of NQO1. Genotyping was done using PCR and gel electrophoresis for MPO and NQO1 and using MALDI-TOF mass spectrometry for SOD2. RESULTS: For SOD2, women with the TC (val/ala) or CC (ala/ala) genotypes were at increased risk [odds ratio (OR) 2.1, 95% confidence interval (CI) 1.1-4.0]. Results for MPO and NQO1 were in the hypothesized directions but were not statistically significant. For MPO, there was a small inverse association among women with GA or AA genotypes (OR = 0.72, 95% CI 0.43-1.2). For NQO1, the TT (ser/ser) genotype was associated with somewhat increased risk (OR = 2.3, 95% CI 0.69-7.6). CONCLUSIONS: While these results need to be confirmed in other studies, they point to a possible role for genes involved in oxidative stress in the development of ovarian cancer.

Life-threatening ventricular arrhythmias due to transient or correctable causes: high risk for death in follow-up.

OBJECTIVES: This study evaluated the prognosis of patients resuscitated from ventricular tachycardia (VT) or ventricular fibrillation (VF) with a transient or correctable cause suspected as the cause of the VT/VF. BACKGROUND: Patients resuscitated from VT/VF in whom a transient or correctable cause has been identified are thought to be at low risk for recurrence and often receive no primary treatment for their arrhythmias. METHODS: In the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with a potentially transient or correctable cause of VT/VF were not eligible for randomization. The mortality of these patients was compared with the mortality of patients with a known high risk of recurrence of VT/VF in the AVID registry. RESULTS: Compared with patients having high risk VT/VF, those with a transient or correctable cause for their presenting VT/VF were younger and had a higher left ventricular ejection fraction. These patients were more often treated with revascularization as the primary therapy, more commonly received a beta-blocker, less often required therapy for congestive heart failure and less commonly received either an antiarrhythmic drug or an implantable cardioverter defibrillator. Nevertheless, subsequent mortality of patients with a transient or correctable cause of VT/VF was no different or perhaps even worse than that of the primary VT/VF population. CONCLUSIONS: Patients identified with a transient or correctable cause for their VT/VF remain at high risk for death. Further research is needed to define truly reversible causes of VT/VF. Meanwhile, these patients may require more aggressive evaluation, treatment and follow-up than is currently practiced.

Effects of pituitary adenylate cyclase-activating polypeptide on canine atrial electrophysiology.

We hypothesized that pituitary adenylate cyclase-activating polypeptide (PACAP) activates intracardiac postganglionic parasympathetic nerves and has a different effect than cervical vagal stimulation. We measured effective refractory period (ERP) and conduction velocity at four atrial sites [high right atrium (HRA), low right atrium (LRA), high left atrium (HLA), and low left atrium (LLA)] and minimum atrial fibrillation (AF) cycle length at 12 atrial sites during cervical vagal stimulation and after PACAP in 26 autonomically decentralized, open-chest, anesthetized dogs. PACAP shortened ERP to a similar extent at all four sites (HRA, 58 +/- 2.0 ms; LRA, 60 +/- 6.3 ms; HLA, 68 +/- 11.5 ms; and LLA, 60 +/- 8.3 ms). Low- and high-intensity vagal stimulation shortened ERP at the HRA, but not in the other atrial sites (low-intensity stimulation: HRA, 64 +/- 4.0 ms; LRA, 126 +/- 5.1 ms; HLA, 110 +/- 9.5 ms; and LLA, 102 +/- 11.5 ms; high-intensity stimulation: HRA, 58 +/- 4.2 ms; and HLA, 101 +/- 4.0 ms). Conduction velocity was not altered by any intervention. Minimum AF cycle length after PACAP was similar in both atria but was shorter in the right atrium than in the left atrium during vagal stimulation. After atropine administration, no interventions changed ERP. These results suggest that PACAP shortens atrial refractoriness uniformly in both atria through activation of intrinsic cardiac nerves, not all of which are activated by cervical vagal stimulation.

Atrial fibrillation: a risk factor for increased mortality--an AVID registry analysis.

Emerging evidence suggests that atrial fibrillation is not a benign arrhythmia. It is associated with increased risk of death. The magnitude of association is controversial and potential causes remain unknown. Patients in the registry of the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial form the basis for this report. Baseline variables, in particular the presence or absence of a history of atrial fibrillation/flutter, were examined in relation to survival. Multivariate Cox regression was used to adjust for differences in important baseline co-variables using 27 pre-selected variables. There were 3762 subjects who were followed for an average of 773+/-420 days; 1459 (39 %) qualified with ventricular fibrillation and 2303 (61 %) with ventricular tachycardia. A history of atrial fibrillation/flutter was present in 24.4 percent. There were many differences in baseline variables between those with and those without a history of atrial fibrillation/flutter. After adjustment for baseline differences, a history of atrial fibrillation/flutter remained a significant independent predictor of mortality, (relative risk=1.20; 95 % confidence intervals=1.03-1.40; p=0.020). Antiarrhythmic drug use, other than amiodarone or sotalol, was also a significant independent predictor of mortality (relative risk 1.34; 95 % confidence intervals 1.07-1.69, p=0.011. Atrial fibrillation/flutter is a significant independent risk factor for increased mortality in patients presenting with ventricular tachyarrhythmias. This risk may have been overestimated in previous studies that could not adjust for the proarrhythmic effects of antiarrhythmic drugs other than amiodarone or sotalol.

Endocardial stimulation of efferent parasympathetic nerves to the atrioventricular node in humans: optimal stimulation sites and the effects of digoxin.

UNLABELLED: The purposes of this study were to identify optimal sites of stimulation of efferent parasympathetic nerve fibers to the human atrioventricular node via an endocardial catheter and to investigate the interaction between digoxin and vagal activation at the end organ. METHODS: The ventricular rate was measured during atrial fibrillation, prior to and during parasympathetic nerve stimulation, in 8 patients taking digoxin and in 10 controls. High frequency electrical stimuli were delivered via an hexapolar or quadripolar electrode catheter, placed at the posteroseptal right atrium near the atrioventricular node (n=18 patients) or in the coronary sinus (n=12 of 18 patients). In 4 patients, stimulation was repeated after intravenous administration of 1 to 2 mg of atropine. RESULTS: Nerve stimulation prolonged the R-R interval in all patients. Stimulation close to the posteroseptal right atrium led to maximal atrioventricular nodal slowing. The mean R-R intervals at baseline and during parasympathetic nerve stimulation (60 mA) from the posteroseptal right atrium and the proximal coronary sinus were 581+/-79 ms, 2440+/-466, and 900+/-228 ms respectively (p=0.0001). The response to nerve stimulation was greater in patients taking digoxin than in patients not taking the drug (p=0.02). Junctional rhythm occurred during nerve stimulation in 8/8 patients taking digoxin and 0/10 not taking the drug (p=0.0001). The response to stimulation was eliminated after atropine (p=0.01). CONCLUSIONS: Parasympathetic nerves to the atrioventricular node were stimulated from the proximal coronary sinus as well as the posteroseptal right atrium. Stimulation at the posteroseptal right atrium resulted in the greatest response, and digoxin enhanced this response. The augmented response suggests that an interaction may exist between parasympathetic stimulation and digoxin at the end organ.

Patients at lower risk of arrhythmia recurrence: a subgroup in whom implantable defibrillators may not offer benefit. Antiarrhythmics Versus Implantable Defibrillator (AVID) Trial Investigators.

OBJECTIVES: The goal of this study was to identify subgroups of arrhythmia patients who do not benefit from use of the implantable cardiac defibrillator (ICD). BACKGROUND: Treatment of serious ventricular arrhythmias has evolved toward more common use of the ICD. Since estimates of the cost per year of life saved by ICD therapy vary from $25,000 to perhaps $125,000, it is important to identify patient subgroups that do not benefit from the ICD. METHODS: Data for 491 ICD patients enrolled in the Antiarrhythmics Versus Implantable Defibrillators Study were used to create a hazards model relating baseline factors to time to first recurrent arrhythmia. The model was used to predict the hazard for recurrent arrhythmia among all trial patients. A priori cut points provided lower and higher recurrent arrhythmia risk strata. For each stratum the incremental years of life due to ICD versus antiarrhythmic drug therapy were calculated. RESULTS: Factors that predicted recurrent arrhythmia were: ventricular tachycardia as the index arrhythmia, history of cerebrovascular disease, lower left ventricular ejection fraction, a history of any tachyarrhythmia before the index event and the absence of revascularization after the index event. Survival times (over a follow-up of three years) were identical in each arm of the lowest risk sextile (survival advantage 0.03 +/- 0.12 [se] years), while the survival advantage for patients above the first sextile was 0.27 +/- 0.07 (se) years (two-sided p = 0.05). CONCLUSIONS: Patients presenting with an isolated episode of ventricular fibrillation in the absence of cerebrovascular disease or history of prior arrhythmia who have undergone revascularization or who have moderately preserved left ventricular function (left ventricular ejection fraction > 0.27) are not likely to benefit from ICD therapy compared with amiodarone therapy.

Impact of a guideline-based disease management team on outcomes of hospitalized patients with congestive heart failure.

BACKGROUND: Congestive heart failure is the most common reason for hospitalization in the United States, and guidelines to improve the quality of care for patients with congestive heart failure have been developed. However, adherence is typically low. We hypothesized that a guideline-based care management team would result in greater quality and efficiency of care than guidelines alone. METHODS: A faculty cardiologist and nurse care manager at an academic medical center reviewed each patient's data and made guideline-based recommendations. Hospital length of stay, total costs, and use of recommended guidelines were compared between 173 patients before team implementation but with available guidelines, 283 care-managed patients, and 126 concurrent non-care-managed patients. RESULTS: Care-managed patients achieved higher rates of use of angiotensin-converting enzyme inhibitor than baseline or non-care-managed patients (95%, 60%, and 75%, respectively; P<.001), as well as increased adherence to guidelines for daily weight monitoring and assessment of left ventricular function. Hospital length of stay was lower (median, 3, 4, and 5 days, respectively; P<.001) as were costs of hospitalization (median, $2934, $3209, and $4830, respectively; P<.01). These differences persisted after adjustment for severity of illness. CONCLUSIONS: When compared with dissemination of guidelines alone, an active care management approach was associated with significant improvements in quality and efficiency of care for hospitalized patients with congestive heart failure.

How to manage atrial fibrillation: an update on recent clinical trials.

The latter half of the 1990s was a time of extraordinary progress in the understanding and management of atrial fibrillation (AF). Evidence that "AF begets AF" has generated considerable interest regarding the mechanisms responsible for this phenomenon and has sparked the development of new concepts in both pharmacologic and nonpharmacologic therapy. The recognition that, in some patients, AF is initiated and possibly maintained by atrial tachycardia originating in the pulmonary veins has challenged accepted notions regarding the mechanisms responsible for arrhythmia. New antiarrhythmic drugs, devices, ablation techniques, and pacing techniques have been developed and tested. Strategies for the use of existing therapies have been evaluated, and new indications for existing therapies are under consideration. This article reviews several studies published in 1999 and 2000 that addressed the mechanisms and the management of AF.

Efficacy and safety of moricizine in the maintenance of sinus rhythm in patients with recurrent atrial fibrillation.

Maintenance of sinus rhythm is the primary goal of antiarrhythmic drug therapy for recurrent atrial fibrillation (AF). However, concern about proarrhythmic and negative inotropic effects has led to increasing reluctance to administer antiarrhythmic agents for this non-life-threatening arrhythmia. Moricizine is well tolerated in a wide variety of patients, and therefore, may be a safe and effective agent for treating AF. We retrospectively assessed the efficacy and safety of moricizine (mean dose 609 +/- 9 mg/day) in 85 consecutive patients with recurrent AF (2.6 +/- 0.5 years duration, 1.6 +/- 1 failed antiarrhythmic drugs). Structural heart disease was present in 69 (81%), but no recent myocardial infarct (< or =90 days) was present; mean left atrial size was 46 +/- 1 mm, and mean left ventricular ejection fraction was 0.51 +/- 0.01. Moricizine was discontinued because of unsuccessful direct-current cardioversion (n = 5) or clinically unacceptable side effects (n = 6); 6 patients developed transient side effects not requiring discontinuation. Of the 74 patients continuing therapy, 68% remained in sinus rhythm after 6 months, and 59% after 12 months. During a follow-up (21 +/- 2 months), there were neither deaths nor adverse effects requiring discontinuation of therapy. Thus, moricizine was effective, safe, and well tolerated in our patient cohort with AF.

Mechanism for pituitary adenylate cyclase-activating polypeptide-induced atrial fibrillation.

INTRODUCTION: Pituitary adenylate cyclase-activating polypeptide (PACAP), which activates intracardiac postganglionic parasympathetic nerves, has a greater profibrillatory effect than vagal stimulation. However, the mechanism responsible for this is unclear. METHODS AND RESULTS: We examined the effective refractory period (ERP), conduction time, and incidence of atrial fibrillation (AF) induced by a single premature extrastimulus at four atrial sites as well as the AF cycle length at 65 atrial sites in 12 autonomically decentralized, open chest, anesthetized dogs. These parameters were measured in the control condition, during cervical vagal stimulation, and after PACAP administration. PACAP shortened the ERP to a similar extent at all four sites. Vagal stimulation shortened the ERP primarily at the high right atrium, but not at the other three sites. Global dispersion of ERP and variation in the AF cycle length (P < 0.01) were less after PACAP than during vagal stimulation. A premature extrastimulus induced AF more frequently after PACAP than during vagal stimulation (P < 0.001). The ERP at the pacing site was shorter when AF was induced than when it was not induced regardless of the intervention and the pacing site. Conduction time following premature beats that induced AF was shorter after PACAP than during vagal stimulation (P < 0.01). CONCLUSION: Global ERP shortening contributes to the greater profibrillatory effect of PACAP. In addition, the decreased conduction time following premature beats may be associated with AF induction in this model.

Design and implementation of an inpatient disease management program.

OBJECTIVE: To describe the development and implementation of an inpatient disease management program. STUDY DESIGN: Prospective observational study. PATIENTS AND METHODS: On the basis of opportunities for improving quality or efficiency of inpatient and emergency department care, 4 diagnoses, including congestive heart failure (CHF), gastrointestinal hemorrhage, community-acquired pneumonia and sickle-cell crisis were selected for implementation of a disease management program. For each diagnosis, a task force assembled a disease management team led by a "physician champion" and nurse care manager and identified opportunities for improvement through medical literature review and interviews with caregivers. A limited number of disease-specific guidelines and corresponding interventions were selected with consensus of the team and disseminated to caregivers. Physician and nurse team leaders were actively involved in patient care to facilitate adherence to guidelines. RESULTS: For quarter 2 to 4 of 1997, there were improvements in angiotensin-converting enzyme inhibitor use, daily weight compliance, assessment of left ventricular function, hospital costs, and length of stay for care-managed patients with CHF. Differences in utilization-related outcomes persisted even after adjustment for severity of illness. For the other 3 diagnoses, the observational period was shorter (quarter 4 only), and hence preliminary data showed similar hospital costs and length of stay for care-managed and noncare-managed patients. CONCLUSIONS: An interdisciplinary approach to inpatient disease management resulted in substantial improvements in both quality and efficiency of care for patients with CHF. Additional data are needed to determine the program's impact on outcomes of other targeted diagnoses.

Importance of atrial flutter isthmus in postoperative intra-atrial reentrant tachycardia.

BACKGROUND: In survivors of congenital heart surgery, intra-atrial reentrant tachycardia (IART) often develops. Previous reports have emphasized the atriotomy scar as the central barrier around which a reentrant circuit may rotate but have not systematically evaluated the atrial flutter isthmus in such patients. We sought to determine the role of the atrial flutter isthmus in supporting IART in a group of postoperative patients with congenital heart disease. METHODS AND RESULTS: Nineteen postoperative patients with IART underwent electrophysiological studies with entrainment mapping of the atrial flutter isthmus for determining postpacing intervals. Radiofrequency ablation was performed at the identified isthmus in an effort to create a complete line of block. Twenty-one IARTs were identified in 19 patients, with a mean tachycardia cycle length of 293+/-73 ms. The atrial flutter isthmus was part of the circuit in 15 of 21 (71. 4%). In the remaining 6 of 21, the ablation target zone was at sites near atrial incisions or suture lines. Ablation was successful in 19 of 21 (90.4%) IARTs and in 14 of 15 (93.3%) cases at the atrial flutter isthmus. CONCLUSIONS: In most of our postoperative patients, the atrial flutter isthmus was part of the reentrant circuit. The fact that the atrial flutter isthmus is vulnerable to ablation suggests that whenever IART occurs late after repair of a congenital heart defect, the atrial flutter isthmus should be evaluated. These data support the theory that some form of conduction block between the vena cava is essential for the establishment of a stable substrate for the atrial flutter reentrant circuit.

Attitudes of faculty, housestaff, and medical students toward clinical practice guidelines.

PURPOSE: To examine attitudes of faculty, housestaff, and medical students toward clinical practice guidelines. METHOD: In a 1997 cross-sectional survey, a two-part, 26-item, self-administered questionnaire was mailed to all faculty, housestaff, and medical students in the department of internal medicine at Case Western Reserve University School of Medicine. The questionnaire asked for demographic information and attitudes toward clinical guidelines. RESULTS: Of 379 persons surveyed, 254 (67%) returned usable questionnaires: 56% of the medical students, 70% of the housestaff, and 73% of the full-time faculty. Medical students reported learning about guidelines predominantly during clerkships in internal medicine (71%) and pediatrics (68%). Overall, the respondents agreed most strongly that guidelines are "useful for the care of common problems," and least strongly that guidelines are "difficult to apply to individual patients" and "reduce physician options in patient care." Faculty were more likely to consider guidelines a "good educational tool" and less likely than were medical students and housestaff to agree that they promote "cookbook medicine." Of 11 influences on clinical decision making, the three groups together rated practice guidelines eighth or ninth. The use of guidelines for academic investigations was rated most appropriate, overall. In terms of their appropriateness, faculty consistently rated the use of guidelines more favorably except for use in malpractice suits. CONCLUSION: Faculty, housestaff, and medical students have significantly different perceptions of and attitudes toward clinical practice guidelines. Further studies are needed to explain the reasons for these differences. Considerable education and involvement must occur at all levels for practice guidelines to be successfully implemented and understood.

Persistent T-wave changes after radiofrequency catheter ablation of an accessory connection (Wolff-parkinson-white syndrome) are caused by "cardiac memory".

BACKGROUND: The purpose of this study was to determine the incidence and origin of T-wave changes after ablation of an accessory atrioventricular connection (AC), which could either be a sign of damage to the coronary circulation or a result of persistent abnormal repolarization secondary to previously abnormal ventricular activation ("cardiac memory"). METHODS AND RESULTS: Ninety of 107 consecutive patients (33 women and 57 men, mean age 36 +/- 5 years) undergoing successful catheter ablation of an AC were studied. Patients with bundle branch block or more than 1 AC were excluded. Sixty-four patients had manifest preexcitation (group 1) and 26 had a concealed AC (group 2). Immediately after loss of preexcitation, 38 (59%) patients with a manifest AC showed T-wave abnormalities. In contrast, none of the patients with a concealed AC had T-wave abnormalities after ablation (P <.05). The T-wave changes (1) did not correlate with the number or duration of energy applications or with markers of tissue injury; (2) correlated with the location of the AC and the degree of preexcitation, respectively; and (3) completely resolved over a period of weeks to months. None of the patients had recurrence of preexcitation or tachycardia during a mean follow-up of 16 +/- 7 months. CONCLUSIONS: T-wave changes after ablation are most likely caused by "cardiac memory" and are not a sign of myocardial or coronary injury.

Characterization of sinoatrial parasympathetic innervation in humans.

INTRODUCTION: The response to sinoatrial parasympathetic nerve stimulation (shortened atrial refractoriness) was used to determine the atrial distribution of these nerve fibers in humans. We hypothesized that, in humans, parasympathetic nerves that innervate the sinoatrial node also innervate the right atrium and that the greatest density of innervation is near the sinoatrial nodal fat pad. METHODS AND RESULTS: Temporary epicardial wire electrodes were sutured in pairs in the sinoatrial nodal fat pad, high right atrium, and right ventricle by direct visualization during coronary artery bypass surgery in nine patients. Appropriate electrode placement was confirmed by electrically stimulating the fat pad in the operating room to prolong sinus cycle length by 50%. Experiments were performed in the electrophysiology laboratory 1 to 5 days after surgery. Programmed atrial stimulation was performed via an endocardial electrode catheter advanced to the right atrium. The catheter tip electrode was moved in 1-cm concentric zones around the epicardial wires by fluoroscopic guidance. Atrial refractoriness was determined in the presence and absence of sinoatrial parasympathetic nerve stimulation at each catheter site. In 8 of 9 patients, parasympathetic nerve stimulation reproducibly prolonged sinus cycle length by 50%. There was no effect on AV nodal conduction (no prolongation of PR interval) and no change in AV nodal refractoriness. Atrial effective refractory periods reproducibly shortened in response to parasympathetic nerve stimulation in 1-cm zones up to 3 cm surrounding the fat pad, by a mean (+/- SEM) of 26.6+/-4.3 msec (zone 1), 11.4+/-1.8 msec (zone 2), and 10.0+/-2.5 msec (zone 3), respectively (P = 0.0001). At distances > 3 cm from the fat pad, the effective refractory period did not shorten. CONCLUSION: Stimulation of parasympathetic nerves that innervate the sinoatrial node shortened atrial refractoriness in humans.