Biomedical subjects
R Yee
Publications and source records attributed to R Yee.
Atrial pacing periablation for prevention of paroxysmal atrial fibrillation.
BACKGROUND: This study tested the hypothesis that rate-adaptive atrial pacing would prevent paroxysmal atrial fibrillation (PAF) in patients with frequent PAF in the absence of symptomatic bradycardia. METHODS AND RESULTS: Patients (n=97) with antiarrhythmic drug-refractory PAF received a Medtronic Thera DR pacemaker 3 months before planned AV node ablation. Patients were randomized to no pacing (n=48) or to atrial rate-adaptive pacing (n=49). After a 2-week stabilization period, patients were followed up for an additional 10 weeks. The time to first recurrence of sustained PAF, the interval between successive episodes of PAF, and the frequency of PAF were compared between the 2 groups in intention-to-treat analysis. Time to first episode of sustained PAF was similar in the no-pacing (4.2 days; 95% CI, 1.8 to 9.5) and the atrial-pacing (1.9 days; 95% CI, 0.8 to 4.6; P=NS) groups. PAF burden was lower in the no-pacing (0.24 h/d; 95% CI, 0.10 to 0.56) than in the atrial-pacing (0.67 h/d; 95% CI, 0.30 to 1.52; P=0.08) group. Paired crossover analysis in 11 patients revealed that time to first PAF was shorter during atrial pacing (1.6 days; 95% CI, 0.6 to 4.9) than with no pacing (6.0 days; 95% CI, 2.4 to 15.0; P=0.13), and PAF burden was greater during atrial pacing (1.00 h/d; 95% CI, 0.35 to 2.91) than with no pacing (0.32 h/d; 95% CI, 0.09 to 1.13; P<0.016). CONCLUSIONS: Atrial rate-adaptive pacing does not prevent PAF over the short term in patients with antiarrhythmic drug-resistant PAF without symptomatic bradycardia.
Use of an extended monitoring strategy in patients with problematic syncope. Reveal Investigators.
BACKGROUND: The conventional investigation of patients who present with syncope involves short-term ECG monitoring or provocative testing with head-up tilt and electrophysiological testing. A symptom-rhythm correlation is often difficult to obtain during spontaneous syncope because of its sporadic, infrequent, and unpredictable nature. METHODS AND RESULTS: We used a prolonged monitoring strategy to determine the cause of syncope in 85 patients (age, 59+/-18 years; 44 men) with recurrent undiagnosed syncope with an implantable loop recorder capable of cardiac monitoring for up to 18 months. During a mean of 10.5+/-4.0 months of follow-up, symptoms recurred in 58 patients (68%) 71+/-79 days (2.3+/-2.6 months) after implantable loop recorder insertion. An arrhythmia was detected in 42% of patients who recorded a rhythm during recurrent symptoms, with bradycardia present in 18 and tachycardia in 3. Five of the 18 bradycardic patients and 2 additional sinus rhythm patients received a clinical diagnosis of neurally mediated syncope. Patients who experienced presyncope were much less likely to record an arrhythmia during symptoms compared with recurrence of syncope (24% versus 70%, P=0.0005). There were no adverse events associated with recurrent symptoms, and there were no sudden deaths. Inability to freeze after an event occurred in 8 patients, and pocket infection occurred in 3. CONCLUSIONS: The strategy of prolonged monitoring is effective and safe in patients with problematic syncope.
The high cost of syncope: cost implications of a new insertable loop recorder in the investigation of recurrent syncope.
BACKGROUND: Patients with recurrent syncope frequently undergo extensive investigations that consume significant health care resources. Recent advances in long-term monitoring techniques have enhanced diagnostic yield in patients with infrequent symptoms. There is little information on the relative cost-effective profile of the investigative tools used in patients with syncope. METHODS: Two methods to determine health care costs in patients with syncope were used. In the first, health care resource utilization was determined in 24 patients with recurrent unexplained syncope and negative investigations who underwent insertion of the implantable loop recorder (ILR) during a pilot study of the feasibility of the device. The costs of investigations before, during, and after ILR implantation in each patient were calculated on the basis of median charges for an index investigation and a regression analysis of 1018 US Medicare hospital claims for syncope from 1993. Charges were converted to costs using a cost-to-charge ratio of 0.64. The second method was based on estimated costs per diagnosis and published diagnostic yields of 6 commonly applied tests in patients with syncope. A cohort simulation using theoretic models of 100 patients undergoing investigation for syncope was created to compare the diagnostic yield and cost per diagnosis of various diagnostic cascades. RESULTS: In the pilot study, the cost of investigation of syncope in the 2 years before ILR insertion was $7584 per patient. After the ILR was inserted, a diagnosis was obtained in 21 of 24 patients (diagnostic yield 88%). The cost of therapy was $2452, followed by a reduction in cost of care to $596 over 30 +/- 10 months of follow-up. In the second method, the diagnostic yield of individual tests ranged from 3% for echocardiography to 88% for the ILR. The cost per diagnosis obtained ranged from $529 for the external loop recorder to $73,260 for electrophysiologic testing in patients without structural heart disease. An approach to syncope similar to that of the ILR pilot study resulted in a cost per diagnosis of $3193 and a diagnostic yield of 98%. Performance of echocardiography in half of the patients and electrophysiologic testing only in the presence of structural heart disease reduced the cost to $2494 and retained a diagnostic yield of 98%. CONCLUSIONS: The cost of investigation of syncope is high. The ILR may reduce health care resource utilization by providing a diagnosis permitting definitive therapy. The cost per diagnosis profile of current diagnostic tests commonly used in patients with syncope is highly variable. A cost-effective approach to diagnosing this disorder can retain a high diagnostic yield with a reduction in resource utilization compared with a conventional approach.
A comparison of patient comfort during cataract surgery with topical anesthesia versus topical anesthesia and intracameral lidocaine.
OBJECTIVE: To determine whether intraocular lidocaine increases patient comfort during cataract surgery while under topical anesthesia. DESIGN: Prospective, randomized, double-masked, placebo-controlled clinical trial. PARTICIPANTS: Both men and women between 45 and 85 years of age who were scheduled for elective cataract surgery while under topical anesthesia participated. Sixty-eight patients were randomized to each group. INTERVENTION: Patients were randomized to receive either topical anesthesia plus intracameral 1% preservative-free lidocaine or intracameral balanced salt solution. MAIN OUTCOME MEASURES: Patient assessment of pain during delivery of the anesthesia, surgery, and after surgery using a visual analog pain scale was measured. Patients also recorded the degree to which they were bothered by tissue manipulation and the microscope light. Surgeon assessments of operative conditions, patient cooperation, and intraoperative complications were recorded. The attending anesthesiologist recorded any required supplemental intravenous sedation and any increase in pulse or increase in blood pressure. RESULTS: There was no significant difference in patient-reported pain scores for delivery of anesthesia (P = 0.902), surgery (P = 0.170), or after surgery (P = 0.680). Patients in the lidocaine group reported being less bothered by tissue manipulation (P = 0.021). The surgeon assessment showed more patient cooperation in the lidocaine group (P = 0.043). CONCLUSIONS: Both topical anesthesia alone and topical anesthesia plus intracameral lidocaine provide good operative conditions for the surgeon and comfortable surgical circumstances for the patient. Injection of intraocular lidocaine increases patient cooperation and decreases the degree to which patients are bothered by tissue manipulation, two outcomes that justify its use.
Sevoflurane has no effect on sinoatrial node function or on normal atrioventricular and accessory pathway conduction in Wolff-Parkinson-White syndrome during alfentanil/midazolam anesthesia.
BACKGROUND: The effects of sevoflurane on the electrophysiologic properties of the human heart are unknown. This study evaluated the effects of sevoflurane on the electrophysiologic properties of the normal atrioventricular conduction system, and on the accessory pathways in patients with Wolff-Parkinson-White syndrome, to determine its suitability as an anesthetic agent for patients undergoing ablative procedures. METHODS: Fifteen patients with Wolff-Parkinson-White syndrome undergoing elective radiofrequency catheter ablation were studied. Anesthesia was induced with alfentanil (20-50 microg/kg) and midazolam (0.15 mg/kg), and vecuronium (20 mg) and maintained with alfentanil (0.5 to 2 microg x kg(-1) x min(-1)) and midazolam (1 or 2 mg every 10-15 min, as required). An electrophysiologic study measured the effective refractory period of the right atrium, atrioventricular node, and accessory pathway; the shortest conducted cycle length of the atrioventricular node and accessory pathway during atrial pacing; the effective refractory period of the right ventricle and accessory pathway; and the shortest retrograde conducted cycle length of the accessory pathway during ventricular pacing. Parameters of sinoatrial node function included sinus node recovery time, corrected sinus node recovery time, and sinoatrial conduction time. Intraatrial conduction time and the atrial-His interval were also measured. Characteristics of induced reciprocating tachycardia, including cycle length, atrial-His, His-ventricular, and ventriculoatrial intervals, also were measured. Sevoflurane was administered to achieve an end-tidal concentration of 2% (1 minimum alveolar concentration), and the study measurements were repeated. RESULTS: Sevoflurane had no effect on the electrophysiologic parameters of conduction in the normal atrioventricular conduction system or accessory pathway, or during reciprocating tachycardia. However, sevoflurane caused a statistically significant reduction in the sinoatrial conduction time and atrial-His interval but these changes were not clinically important. All accessory pathways were successfully identified and ablated. CONCLUSIONS: Sevoflurane had no effect on the electrophysiologic nature of the normal atrioventricular or accessory pathway and no clinically important effect on sinoatrial node activity. It is therefore a suitable anesthetic agent for patients undergoing ablative procedures.
Appropriate use of the implantable cardioverter defibrillator: a Canadian perspective. Canadian Working Group on Cardiac Pacing.
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Acute testing of the rate-smoothed pacing algorithm for ventricular rate stabilization.
We evaluated the capability of a new pacemaker-based rate-smoothing algorithm (RSA) to reduce the irregular ventricular response of AF. RSA prevents sudden decreases in rate using a modified physiological band and flywheel feature. Twelve patients (51 +/- 21 years) with hemodynamically tolerated AF of 4 months to 20 years duration were studied. Atrial and ventricular leads were connected to the external pacemaker device in the electrophysiology laboratory. Consecutive RR intervals during AF were measured at baseline and after ventricular pacing with RSA ON. Ventricular pacing with the rate smoothing algorithm reduced maximum RR intervals (1,207 +/- 299 vs 855 +/- 148 ms, P = 0.0005), with no significant change in the minimum RR interval (401 +/- 55 vs 393 +/- 74 ms, P = 0.292). A small shortening of the mean RR interval (634 +/- 153 vs 594 +/- 135 ms, P = 0.007) was seen with no change in the median RR interval (609 +/- 153 vs 595 +/- 143 ms, P = 0.388). There was a 43% reduction in RR standard deviation (145 +/- 52 vs 82 +/- 28, P = 0.0005), 49% reduction in mean absolute RR interval difference (MAD) (152 +/- 64 vs 77 +/- 34, P = 0.0005) and MAD/mean RR ratio (0.23 +/- 0.05 vs 0.13 +/- 0.04, P = 0.0005). We conclude that rate-smoothed pacing effectively reduces RR variability of AF in the acute setting.
A cost effective approach to the investigation of syncope: relative merit of different diagnostic strategies.
OBJECTIVE: To compare the cost effectiveness of a conventional diagnostic work-up with that of several different diagnostic cascades for the investigation of undifferentiated syncope. DESIGN: A MEDLINE search established a weighted estimate of diagnostic yield for several diagnostic investigations. 'High-end' and 'low-end' cost estimates were calculated for these investigations based on figures from four representative Canadian tertiary care centres in four different provinces. Several diagnostic models were applied to a hypothetical cohort of 100 patients with undifferentiated syncope. RESULTS: The conventional diagnostic cascade resulted in a diagnosis in 85% of patients, at a cost per diagnosis of $467 to $959. The optimal model increased the diagnostic yield to 98.9%, at a cost of $460 to $1043 per diagnosed patient. CONCLUSION: A combination of new technology and selective use of investigations has the potential to raise diagnostic yield without appreciably increasing cost per diagnosis.
Tumor-associated antigen TA-90 immune complex assay predicts subclinical metastasis and survival for patients with early stage melanoma.
BACKGROUND: TA-90 is a tumor-associated antigen first identified in the urine and sera of patients with metastatic melanoma. In the early stages of disease, TA-90 is present in circulating immune complexes (ICs) that may be detected with an antigen specific enzyme-linked immunosorbent assay (ELISA). In this study, the authors evaluated the efficacy of the TA-90 IC assay in detecting subclinical metastasis of early stage melanoma and predicting the survival of patients with this disease. METHODS: Archival sera were collected preoperatively from 114 patients who underwent wide excision with or without regional lymphadenectomy in the treatment of clinical Stage I melanoma. Sera were analyzed for TA-90 IC in a blinded fashion, and results were correlated with the patient's clinical course as determined by database and chart review. Subclinical metastases were considered present at the time of surgery if the lymphadenectomy specimen was pathologically positive and/or the patient subsequently developed recurrence. RESULTS: The TA-90 IC assay predicted subclinical metastasis in 43 of 56 patients (P < 0.0001), with 14 false-positive and 13 false-negative results. Sensitivity and specificity for the detection of occult metastasis were 77% and 76%, respectively. Positive and negative predictive values were 75% and 77%, respectively. Fifteen of 18 tumor positive regional lymph node basins (83%) and 34 of 46 recurrences (74%) were accurately predicted when considered independently (P < 0.004). Preoperative TA-90 IC status was also highly correlated with survival: 5-year overall and disease free survival rates were 63% and 46%, respectively, for the TA-90 IC positive group, compared with 88% and 82%, respectively, for the TA-90 IC negative group (P=0.0001). A multivariate analysis with standard prognostic variables identified preoperative TA-90 IC status as a strong, independent prognostic factor for both overall and disease free survival. CONCLUSIONS: To the authors' knowledge, TA-90 is the first tumor marker that accurately predicts subclinical metastatic disease and survival for patients with early stage melanoma. For this reason, the TA-90 IC assay has the potential to improve dramatically the prognostic evaluation of patients with this disease. Its role in postoperative risk stratification and early detection of recurrence is being evaluated in a prospective study.
Final results from a pilot study with an implantable loop recorder to determine the etiology of syncope in patients with negative noninvasive and invasive testing.
Twenty-four patients with recurrent unexplained syncope and negative tilt and electrophysiologic testing underwent implantation of the implantable loop recorder, with recurrence of syncope in 21 patients 5.1+/-4.8 months after device implantation. Eighteen of the 21 had a treatable diagnosis, with arrhythmias in 11. Treatment resulted in resolution of syncope in most patients during long-term follow-up.
Positron emission tomography plus serum TA90 immune complex assay for detection of occult metastatic melanoma.
BACKGROUND: Whole-body positron emission tomography (PET) using 18F-fluorodeoxyglucose is very sensitive for detection of metastatic melanoma. We previously reported the accuracy of a serum TA90 enzyme-linked immunosorbent assay (ELISA) in predicting the recurrence of early-stage melanoma. This serum ELISA measures a circulating immune complex composed of TA90 a tumor-associated 90-kD glycoprotein antigen, and its IgG antibody. We hypothesized that using PET examination in conjunction with our serum TA90 ELISA would increase the detection of occult melanoma lesions. STUDY DESIGN: From November 1, 1993 to December 31, 1995, 87 patients underwent PET examination followed within 6 weeks by serum TA90 ELISA. All patients had undergone complete resection of local, regional, or distant metastatic melanoma and had no clinical evidence of disease at the time of PET examination. Each patient had complete followup for 12 months after PET examination. The clinical course was determined by chart review of clinical and radiographic findings. RESULTS: Of the 25 patients who experienced recurrence of disease within 6 months of followup, 22 (88%) had a positive result on one or both tests. Of the 52 patients with a negative result on both tests, 49 (94%) remained disease-free at 6 months of followup. Of the 14 patients who developed distant metastases within 6 months after PET examination, 13 (93%) had a positive PET examination and/or a positive TA90 ELISA. CONCLUSIONS: The TA90 ELISA correlated well with PET examination for detection of metastatic melanoma. The high sensitivity of PET examination plus TA90 ELISA suggests that this combination may have a role in the surveillance of patients at high risk of developing metastatic melanoma.
Benzocaine-induced methemoglobinemia--two case reports related to transesophageal echocardiography premedication.
Benzocaine-induced methemoglobinemia is a potentially life-threatening complication. We report two cases of methemoglobinemia due to topical benzocaine spray used as premedication for transesophageal echocardiography. A high index of suspicion is needed for this readily treatable condition.
The use of topical cyclosporin A in ocular graft-versus-host-disease.
Ocular manifestations of GVHD include keratoconjunctivitis sicca, cicatricial lagophthalmos, sterile conjunctivitis, persistent corneal epithelial defects, corneal ulcers and corneal melting. Conventional initial therapy such as lubrication and topical steroids is directed to treat decreased tear production and ocular surface abnormalities. The purpose of this study was to illustrate the possible benefit of topical cyclosporin A 1% (CsA) as an adjunct in managing ocular surface abnormalities in five cases of GVHD refractory to conventional therapy. Five clinical case reports of chronic GVHD patients in whom conventional therapy was inadequate to stop the progression from its initial presentation are described. Patient presentation varied in severity on a spectrum of mild to moderate diffuse punctate epithelial erosions to sterile necrotizing corneal melts. Although systemic therapy for GVHD consisting of systemic immunosuppressants (ie cyclosporin A and corticosteroids) was given to these patients, this therapy was insufficient in managing the ocular manifestations of the disease. Topical CsA was added to the treatment regimen and the progression of the ocular disease was recorded. The addition of topical CsA 1% probably helped in controlling the epithelial keratitis and melting process in our reported cases and we conclude that topical CsA may be an appropriate modality in managing ocular surface abnormalities in patients with ocular GVHD after conventional treatments have been tried. However, a further randomized clinical prospective study is needed to evaluate the efficacy of topical CsA in managing these problems in GVHD patients.
Pushing the ablation frontier in atrioventricular node reentrant tachycardia.
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Oral pilocarpine for symptomatic relief of keratoconjunctivitis sicca in patients with Sjögren's syndrome. The MGI PHARMA Sjögren's Syndrome Study Group.
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Correlation of waiting time with adverse events in patients admitted for nonelective permanent pacemaker implantation.
OBJECTIVE: To determine the effect of a dedicated permanent pacemaker implantation procedure room on waiting time and waiting time-related morbidity. DESIGN: Retrospective chart review. SETTING: Two tertiary care teaching hospitals in southern Ontario; one with a dedicated procedure room (centre B) and one without (centre A). PATIENTS: Two hundred and fourteen consecutive patients who required permanent pacing urgently or emergently. METHODS: Charts were examined retrospectively at centre A (131 patients) and centre B (83 patients) to determine the waiting time for and the number of preoperative adverse events in nonelective permanent pacemaker implantation. RESULTS: Patients in centre A waited a mean of 4.5 +/- 3.0 days while patients in centre B waited a mean of 1.9 +/- 1.6 days (P = 0.0001). Centre A patients experienced a total of 57 adverse events that were likely or possibly related to the waiting period, while patients at centre B experienced eight such events (P < 0.0001). Thirty-three per cent of the centre A patients experienced at least one adverse event, while 8% of centre B patients experienced at least one adverse event (P < 0.00001). Of the centre A patients who waited for more than six days (26 patients), 58% had at least one adverse event, compared with 26% of those who waited less than six days (105 patients, P = 0.0009). CONCLUSIONS: Delays in implanting nonelective permanent pacemakers are strongly associated with an increase in adverse events. Measures to shorten the waiting time are likely to result in a reduction in morbidity in conjunction with a beneficial impact on health care resource utilization.
Cardiac pacing in Canada in 1998: working towards optimal pacing therapy. Canadian Working Group on Cardiac Pacing.
The Canadian Working Group on Cardiac Pacing (CWGCP) was formed in 1996 with the primary goal of promoting optimal pacing therapy in Canada. In 1997, the CWGCP conducted a survey of pacing practices across Canada. Ninety-two of 125 implanting programs (74%) responded. Implant rates vary by province--from 39 per 100,00 population in Ontario to 63 per 100,000 population in Nova Scotia and Prince Edward Island. Variations in regional implant rates persist even after correcting for the age of the population. Physiological pacing was used for 35% of all implants in Canada in 1996/97. There were marked differences across Canada in the mode of pacing selected. In western Canada, 39.5% of pacing systems implanted were physiological compared with 18.2% in Atlantic Canada and 29% in Quebec. There were also differences in follow-up practices. Approximately 40% of centres follow patients with single chamber pacemakers annually, whereas most other centres still follow these patients every six months. Economic constraints, the size of pacing programs and the involvement of committed pacing physicians are factors that may influence the regional differences in cardiac pacing across Canada.