Spatial Resolution of Pacemapping and Activation Mapping in Patients with Idiopathic Right Ventricular Outflow Tract Tachycardia

BACKGROUND

The purpose of this study was to compare the spatial resolution of activation mapping and pacemapping in patients undergoing ablation of idiopathic ventricular tachycardia (VT) arising from the right ventricular outflow tract (RVOT). A direct comparison of the two techniques has not been undertaken.

METHODS AND RESULTS

Electroanatomical activation maps of the RVOT were obtained during VT in 15 patients. Pacemaps were obtained from multiple sites, tagged on the activation map, and scored according the degree of concordance between the paced QRS configuration and that of VT. The site of successful ablation was considered the VT site of origin. Initial endocardial activation away from the site of origin was rapid; the mean area of myocardium activated within the first 10 msec (early activation area, EAA) was 3.0 +/- 1.6 cm(2) (range: 1.3-6.4 cm(2)). Best pacemap scores were always obtained adjacent to the site of origin. Pacemap concordance, and the probability of an exact pacemap match significantly decreased with increasing distance of the pacing site from the site of origin (P < 0.01). All patients had more than one pacing site yielding a best pacemap score. The greatest distance between such sites in an individual patient ranged from 11 to 26 mm (mean: 18 +/- 5 mm), and was strongly correlated with the size of the EAA (r = 0.77, P < 0.001).

CONCLUSIONS

Pacemapping and activation mapping provide similar localizing information. The spatial resolution of each technique is modest, varies between patients, and may be optimized by three-dimensional data display.

Implications and Outcome of Permanent Coronary Sinus Lead Extraction and Reimplantation

OBJECTIVE

We examined the implications and outcome of coronary sinus (CS) lead removal including the feasibility of laser use within the CS.

BACKGROUND

Cardiac anatomy and lead interactions are more complex with the advent of biventricular pacemakers and atrial cardioverters requiring permanent lead/shocking coil placement in the coronary sinus and its branches.

METHODS

Fifty-five permanent cardiac leads were extracted during 2003 in 28 consecutive patients. Our study population included a 10/55 (18%) subset (all males; age 73 +/- 6 years; EF = 0.24 +/- 0.09) that underwent CS (1/10) or vein branch (9/10) lead extraction. Leads were extracted with an excimer laser sheath (n = 4) or by direct traction (n = 6). Median times between implantation and lead removal were 9.5 months (range 5-59) in the laser group and 3 months (range 3-4) in the direct traction group. Indication for extraction was infection (n = 4), dislodgement (n = 3), diaphragm stimulation (n = 2), and elevated threshold (n = 1). The CS was divided into distal, mid, and proximal segments by venogram.

RESULTS

Entry of the laser sheath into the CS was necessary in three of four laser patients. The two distal CS laser cases (left lateral CS coil and anterior-lateral left ventricular (LV) lead) required both 14- and 12-Fr sheaths, separately. The proximal CS laser case (posterior-lateral LV lead) required a 12 Fr sheath. The remaining laser patient required a 12-Fr sheath to pass to the mid SVC. There were no procedural complications as a result of CS lead extraction. Reimplantation of a CS lead was attempted in 7/10 patients at a median of 4 days (range 1-300). CS venograms were available for review in patients before initial implantation (6/10) and after extraction (7/10). The postextraction venograms demonstrated complete occlusion of the vein from which the lead was extracted, and its distal branches, which were unusable in 5/10 (50%). The vein occlusions were present in patients with indwelling leads for greater than 3 months and were independent of extraction method.

CONCLUSIONS

Laser lead extraction in the coronary sinus appears feasible in carefully selected cases with mandatory indications. However, special intraoperative monitoring and echocardiographic imaging with surgical backup ready is strongly recommended. Target vein selection may be limited for the purpose of reimplantation when leads are indwelling for greater than 3 months.

Hypersensitive carotid sinus syndrome due to neurofibromatosis-1 and manifested by repeated episodes of syncope

A 28-year-old patient with neurofibromatosis-1 presented with syncope. The exam demonstrated a mass adjacent and inferior to the right occiput that extended to the posterior lateral right-sided neck. Initial invasive and noninvasive testing was negative. Imaging of her head and neck demonstrated a large neurofibroma enveloping her right carotid sinus without vessel occlusion or evidence of malignancy. An event recorder documented asystole. A pacemaker was implanted to avoid the surgical morbidity of removing the neck mass. The patient has since been free of syncope. We believe neurofibromatosis-1 should be included in the differential of syncope.

Influence of age and gender on the mechanism of supraventricular tachycardia

OBJECTIVES

The objective of this study was to determine the impact of age and gender on the mechanism of paroxysmal supraventricular tachycardia (PSVT).

BACKGROUND

Previous studies have indicated that PSVT mechanism may be influenced by age and gender, but contemporary data are limited.

METHODS

In 1,754 patients undergoing catheter ablation of 1,856 PSVTs between 1991 and 2003, the mechanism was classified as atrioventricular reentrant tachycardia (AVRT), atrioventricular nodal reentrant tachycardia (AVNRT), or atrial tachycardia (AT). Patients with inappropriate sinus tachycardia, atrial flutter, atrial fibrillation, and age <5 years were excluded.

RESULTS

The mean age was 45 +/- 19 years (range 5-96), and the majority were women (62%). Overall, AVNRT was the predominant mechanism (n = 1,042 [56%]), followed by AVRT (n = 500 [27%]) and AT (n = 315 [17%]). There was a strong relationship between age and PSVT mechanism; the proportion of AVRT in both sexes decreased with age, whereas AVNRT and AT increased (PM < .001 by ANOVA). The majority of patients with AVRT were men (273/500 [54.6%]), whereas the majority of patients with AVNRT and AT were women (727/1,042 [70%] and 195/315 [62%], respectively). The distribution of PSVT mechanism was significantly influenced by gender (P < .001). In women, 63% had AVNRT, 20% had AVRT, and 17.0% had AT. In men, 45% had AVNRT, 39% had AVRT, and 17% had AT. AVNRT replaced AVRT as the dominant PSVT mechanism at age 40 in men and at age 10 in women.

CONCLUSIONS

The mechanism of PSVT in patients presenting for ablation is significantly influenced by both age and gender.

Time dependence of mortality risk and defibrillator benefit after myocardial infarction

BACKGROUND

Prophylactic implantable defibrillators (ICDs) improve survival in patients with impaired ventricular function after myocardial infarction (MI), but it is uncertain whether mortality risk and survival benefit depend on the elapsed time from MI.

METHODS AND RESULTS

The Multicenter Automatic Defibrillator Implantation Trial II examined the impact of ICDs on survival in post-MI patients with ejection fractions < or =30%. In 1159 patients, mean time from most recent MI to enrollment was 81+/-78 months. Patients were randomized to an ICD (n=699) or conventional care (n=460) in a 3:2 ratio. Mortality rates (deaths per 100 person-years of follow-up) in both treatment groups were analyzed by time from MI divided into quartiles (<18, 18 to 59, 60 to 119, and > or =120 months). In conventional care patients, these rates increased as time from MI increased (7.8%, 8.4%, 11.6%, 14.0%; P=0.03). Mortality rates in ICD patients were consistently lower in each quartile and showed minimal increase over time (7.2%, 4.9%, 8.2%, 9.0%; P=0.19). Covariate-adjusted hazard ratios for risk of death associated with ICD therapy were 0.97 (95% CI, 0.51 to 1.81; P=0.92) for recent MI (<18 months) and 0.55 (95% CI, 0.39 to 0.78; P=0.001) for remote MI (> or =18 months).

CONCLUSIONS

Mortality risk in patients with ejection fractions < or =30% increases as a function of time from MI. The survival benefit associated with ICDs appears to be greater for remote MI and remains substantial for up to > or =15 years after MI.

Effect of radiofrequency current on previously implanted pacemaker and defibrillator ventricular lead systems

We compared the response of endocardial lead systems to radiofrequency (RF) current delivered during atrio-ventricular junction ablation (AVJA) for atrial fibrillation with uncontrolled ventricular rate in 107 patients. The mean age was 67 +/- 11 years and the mean ejection fraction 42 +/- 15%. Patients were divided into 3 groups based on the type of ventricular lead present at the time of ablation: a previously implanted defibrillator lead (group 3, n = 13), a previously implanted pacemaker lead (group 2, n = 46) or a temporary lead (group 1, n = 48), which was subsequently followed by a permanent lead implantation. During AVJA, a median of 5 RF applications (44 +/- 8 W) were given via 4-5-mm electrodes. All but 1 patient had right-sided lesions, while 6 patients also had left sided lesions. Ventricular pacing thresholds were evaluated immediately pre- and post-ablation at 24 hours and at 1 to 3 months. Increases in ventricular pacing voltage thresholds were noted in all 3 groups over time, with the greatest mean increase in group 3 patients: [table: see text]. A greater than 2-fold increase in pacing thresholds was observed only with previously implanted leads, usually within the first 48 hours. It occurred significantly more often in patients with group 3 (6/13 [46%]) compared to group 2 (6/46 [13%], odds ratio 7.6, P = 0.006). A progressive rise in pacing threshold required lead revision in 2/13 group 3 patients (15%) and 2/46 group 2 patients (4%). While RF current has only minor effects on pacing threshold in most patients with previously implanted ventricular lead systems, clinically important alterations requiring device reprogramming or lead revision may occur. Group 3 are significantly more vulnerable to RF current, though the mechanisms are unclear. Group 1 during AVJA, followed by permanent lead implantation appears advisable. Pts with a previously implanted group 3 who require AVJA should be monitored closely.

A novel sample holder allowing atomic force microscopy on transmission electron microscopy specimen grids: repetitive, direct correlation between AFM and TEM images

A novel sample holder that allows atomic force microscopy (AFM) to be performed on transmission electron microscope (TEM) grids is described. Consequently, AFM and TEM images were repeatedly obtained on exactly the same sample area. For both techniques, a thin carbon film was used as the imaging substrate. Although these techniques have been previously used in conjunction, AFM and TEM images on exactly the same area have not been repeatedly obtained for any system. Correlation of AFM and TEM images is useful for work where the three-dimensional topographical information provided by the AFM could be used to better interpret the two-dimensional images provided by the TEM and vice versa. To demonstrate the applicability of such correlation, new results pertaining to a fibrillar collagen system are summarized.

Arthroscopic suture tying: A comparison of knot types and suture materials

PURPOSE

The purpose of this study was to determine the structural properties of 3 arthroscopically tied knots using 2 different suture materials: the French knot, the Duncan loop knot, and the original Revo knot.

TYPE OF STUDY

Cohort analytic study.

METHODS

The sutures used were No. 1 PDS II, an absorbent monofilament, and No. 1 Ethibond (Ethicon, Somerville, NJ), a braided nonabsorbent material. The resulting 6 suture-knot combinations were individually tested to failure in both open- and closed-loop configurations.

RESULTS

The French knot showed the greatest strength compared with the Duncan loop and the Revo knot with both No. 1 Ethibond and No. 1 PDS II sutures (P <.05). The No. 1 Ethibond exhibited higher initial stiffness than the No. 1 PDS II for all 3 knot types (P <.05). Results were similar for both open and closed-loop configurations. Also, the French knot failed predominantly by suture breakage instead of knot slippage for both suture materials.

CONCLUSIONS

The results of this study suggest that, among the suture and knot combinations investigated in this study, the arthroscopic repair of musculoskeletal injuries should be performed using the French knot and No. 1 Ethibond suture.

Time and cost analysis of repacking medications in unit-of-use containers

OBJECTIVES

To evaluate the effects of repacking drugs in unit-of-use containers in community pharmacies. The purpose of this study was to examine whether unit-of-use repacking reduces routine mechanical "counting and pouring" to allow more time for pharmaceutical care.

DESIGN

Simulation pilot study to evaluate the differences between the existing and proposed systems. Based on the literature, four variables--optimum pack size, time savings, packaging costs, and shelving requirements--were selected for evaluation. Historical prescription data from a chain were used in determining the sample drugs and their optimum pack sizes. Workflow analysis and time study were used to estimate the time savings. Manufacturer bottles, repack bottles, and shelves were measured to determine the impact of using unit-of-use containers on storage requirements.

SETTING

Three community pharmacies in a major drugstore chain in Cincinnati, Ohio.

RESULTS

The 25 fastest-moving solid oral dosage forms, representing 21.6% of all drugs dispensed by the chain, were selected as the sample drugs for the study. The workflow analysis and time study revealed that 0.79 minutes could be saved per prescription if repacked drugs were used. There was an increased cost of approximately $0.05 for every repack bottle used in place of a prescription vial. It was calculated that repacking in unit-of-use containers would increase storage requirements in the pharmacy by 2.5 times if current inventory levels were maintained.

CONCLUSION

Repacking drugs in unit-of-use containers is potentially an inexpensive method to increase usable time in the pharmacy that does not require an increase in personnel or the purchase of additional technology at the store level.

Atypical atrial flutter originating in the right atrial free wall

BACKGROUND

Data from experimental models of atrial flutter indicate that macro-reentrant circuits may be confined by anatomic and functional barriers remote from the tricuspid annulus-eustachian ridge atrial isthmus. Data characterizing the various forms of atypical atrial flutter in humans are limited.

METHODS AND RESULTS

In 6 of 160 consecutive patients referred for ablation of counterclockwise and/or clockwise typical atrial flutter, an additional atypical atrial flutter was mapped to the right atrial free wall. Five patients had no prior cardiac surgery. Incisional atrial tachycardia was excluded in the remaining patient. High-density electroanatomic maps of the reentrant circuit were obtained in 3 patients. Radiofrequency energy application from a discrete midlateral right atrial central line of conduction block to the inferior vena cava terminated and prevented the reinduction of atypical atrial flutter in each patient. Atrial flutter has not recurred in any patient (follow-up, 18+/-17 months; range, 3 to 40 months).

CONCLUSIONS

Atrial flutter can arise in the right atrial free wall. This form of atypical atrial flutter could account for spontaneous or inducible atrial flutter observed in patients referred for ablation and is eliminated with linear ablation directed at the inferolateral right atrium.

Retrograde fast pathway ablation for atrioventricular nodal reentry associated with markedly prolonged PR intervals

Three patients with typical atrioventricular nodal reentrant tachycardia (AVNRT) and markedly prolonged PR intervals (>300 ms) without dual pathway physiology at baseline or during isoproterenol infusion underwent successful fast pathway ablation and remained asymptomatic without recurrent AVNRT, atrioventricular block, or symptomatic bradycardia for a mean of 19 months. In patients with recurrent AVNRT and markedly prolonged PR intervals, selective ablation of the retrograde fast pathway can eliminate AVNRT without further impairment of anterograde atrioventricular nodal function.

Endemic blastomycosis in Mississippi: epidemiological and clinical studies

In order to clarify the epidemiology and clinical spectrum of endemic blastomycosis, we reviewed the charts of 326 culture and/or histologically proven cases of blastomycosis in Mississippi from 1979 to 1988. Cases were dispersed throughout the state, but counties in central and south-central Mississippi reported 63% of all blastomycosis cases. The average annual incidence rate was 1.3 cases per 100,000 population. The majority of cases were in men (male to female ratio 1.7:1), and most patients were aged in their third through seventh decades (82%). Outdoor occupations were noted for only 28.9% of cases. Cases occurred throughout the year with no significant seasonal peak. Although 55% saw a physician within 7 days of onset of illness, 29% presented after 1 month. Despite early presentation, diagnosis was often delayed for more than 1 month (43.3%). Single organs were involved in 82.8% of cases. For all cases, organ systems involved included lungs (91.4%), skin (18.1%), bone (4.3%), genitourinary system (1.8%), and central nervous system (1.2%). The presence of skin or bone disease was associated with multiorgan involvement. Thirty-three patients died (11.5%), 6 of whom received no therapy. Patients who died were significantly older than those who survived. A successful outcome without relapse was noted in 86.5% of amphotericin B-treated patients and in 81.7% of ketoconazole-treated patients. The relapse rate for ketoconazole-treated patients was higher than for amphotericin B-treated patients (14% and 3.9% respectively).

Re-engineering a pharmacy work system and layout to facilitate patient counseling

The development and evaluation of a new work system and facility design for a chain of community pharmacies are described. A new work system was developed to optimize utilization of pharmacist and technician time and allow the pharmacy to increase patient counseling without adding personnel. In the new system, pharmacists would review prescriptions, check technicians' work, and dispense prescriptions, counseling patients as needed; technicians would enter prescriptions into the pharmacy computer and fill them. The existing work system and design were evaluated in June and July of 1992 by observing, classifying, and recording activities of pharmacy personnel three days per week at six pharmacies in the chain. Pharmacy designs that would work with the new work system were created by a university design class after consultation with representatives of the pharmacy chain and the university's college of pharmacy. The pharmacy chain selected one design, and a detailed floor plan and specifications were created. To test how the new design and system would work at each of the six test pharmacies, a computer simulation program was developed and verified by using the data collected on the existing pharmacy operations. Computer simulation showed that, with the new design and system, increasing patient counseling would increase patient waiting time slightly but would not require additional personnel. The layout and work system in a chain of community pharmacies were redesigned to facilitate patient counseling and make the best use of employee time.

A modified free gracilis flap in the rat

We present in this paper the use of a combined neurovascularized flap of gracilis muscle and inguinal skin in the rat with the femoral vessels and obturator nerve serving as the pedicles. The epigastric, saphenous, and muscular branch vessels arising from the femoral vessels were preserved, and a portion of adductor magnus muscle was included in the flap to protect the delicate muscle vessels at their origins. The inguinal skin and muscle flap both had independent blood supplies, thus separate assessment of muscle and skin rejection was possible in the single transplanted "packet." The muscle flap with the reconnected motor nerve regained contractile ability upon nerve stimulation within 30 days after the iso-transplantation. The results suggest that the modified gracilis myocutaneous flap provides an ideal model for transplantation research.

Listerial infections in patients with systemic lupus erythematosus

Infection with Listeria monocytogenes is known to occur more frequently in immunosuppressed patients, including those receiving high-dose prednisone or cytotoxic therapy for collagen vascular disease. We reviewed three cases of listeriosis and systemic lupus erythematosus (SLE) seen at our institution, in addition to five cases reported in the English literature. Seven of the eight patients had non-CNS listerial infections. All patients but one had associated risk factors of either renal failure or pregnancy. From our review, we found that listeriosis is uncommon in SLE, and patients without renal failure or pregnancy do not seem to be at increased risk for listeriosis. Although most patients were treated with high-dose prednisone, with or without cytotoxic drugs, the role of immunosuppression by these drugs as a risk factor for listeriosis remained unclear.

[Preliminary study of cartilage repair with autologous periosteum and fibrin adhesive system]

The potential surgical transplantation with autogenous periosteal grafts and Fibrin Adhesive System (FAS) was attempted in a rabbit model. The grafts were taken from the tibia, transplanted and fixed with FAS to artificial full-thickness (0.4 x 0.3 cm) defect on the femoral condyle. Histologic and ultrastructural findings revealed chondrocyte regeneration in the control, grafted, and graft/FAS treated group at week 6; however, chondrogenesis of the reparative tissue was best demonstrated in the graft/FAS group. At week 12, the interface between the reparative tissue and the surrounding tissue was invisible in the FAS/graft group, as compared with the well-defined interface in the grafted group and the control. The results strongly suggest that FAS-treated periosteal transplant is a potential model for the repair of articular cartilage defects. Although the results are preliminary, all seem promising in the clinical aspects.

Development of self-recognition in chimpanzees (Pan troglodytes)

Chimpanzees (Pan troglodytes) demonstrate the ability to recognize themselves in mirrors, yet investigations of the development of self-recognition in chimpanzees are sparse. Twelve young chimpanzees, grouped by age, were given mirror exposure and tested for self-recognition and contingent movement. All 6 juveniles, 4 and 5 years old, exhibited mirror-guided, mark-directed behavior and clear evidence of self-recognition. In contrast, among the infants, only the oldest group of 2 1/2-year-olds exhibited clear evidence of self-recognition. All chimpanzees exhibited both self-directed behaviors and contingent movements. These results suggest that self-recognition occurs at a slightly older age in chimpanzees than in human infants. In humans, self-recognition is linked with other cognitive abilities. The results conform to the general pattern that great apes exhibit many cognitive skills comparable to those of 2-year-old humans.

Initiation of transcription by T7 RNA polymerase as its natural promoters

A kinetic assay has been developed to measure the strength of natural T7 promoters. By determining the rate of appearance of initiation products in the presence of constant concentrations of T7 RNA polymerase, an incomplete mixture of ribonucleoside triphosphates, and increasing promoter concentrations, a maximum rate of product formation (Vmax) and a promoter concentration giving half of the maximal activity ([P]Vmax/2) can be determined for any cloned T7 promoter. On supercoiled plasmids, it was found that the [P]Vmax/2 measured for the six promoters phi 1.1B, phi 1.3, phi 3.8, phi 6.5, phi 10, and phi 13 ranged from 3.4 +/- 1.1 to 12.0 +/- 2.4 nM while the Vmax values showed no significant trends. On plasmids that had been linearized by cleavage at a single site with a restriction endonuclease, the cloned T7 promoters assayed fell into two broad classes that appear to be characterized by the T7 class II and III promoters. Generally, the class II promoters required higher promoter concentrations to produce half of the maximum rates of initiation ([P]Vmax/2 values) than the class III promoters. The [P]Vmax/2 values for the class II promoters ranged from 20 +/- 2.7 to 23 +/- 3.6 nM, while the [P]Vmax/2 values for the class III promoters phi 10 and phi 13 were 13 +/- 1.6 nM and 7.8 +/- 1.4 nM. The one exception is the class III promoter phi 6.5 whose [P] Vmax/2 (17 +/- 5 nM) falls between the [P]Vmax/2 values of the class II promoters and the strong class III promoters. The Vmax values measured on linear templates are variable, but it appears that phi 10 is more active than the other five promoters.

Vascularized autogenous canine coccygeal bone transfer

Based on cadaver studies in dogs, the 8th, 9th, or 10th canine coccygeal vertebra with overlying skin was designed for free vascularized bone transfer. In six dogs the coccygeal osteocutaneous flap was transferred to fill a defect of the tibia, anastomosing the median caudal artery and one of the two caudal veins to the tibial vessels. The overlying skin provided a reliable monitoring system for the transferred tissue. The behavior of the vascularized coccygeal vertebrae was then evaluated with radiographic and histologic examination and compared with control vertebrae transferred without reconnection of the blood vessels. The results revealed that the canine coccygeal bone graft is a reliable vascularized osteocutaneous flap, which can be applied either in clinical veterinary surgery or in orthopedic microsurgical research.