Effects of Cimetidine on Sinus Node Function and Atrioventricular Conduction in Man

Electrophysiological effects of H2-receptor blockade 200 mg cimetidine IV on sinus node (SN) function and atrioventricular (AV) conduction were evaluated. Tests were performed in 21 people in basal state (group I), and in 14 people (group II) after autonomic blockade (AB) (propranolol 0.2 mg/kg, and atropine 0.04 mg/kg). We analyzed sinus cycle length (SCL), sinus node recovery time (SNRT), corrected sinus node recovery time (CSNRT), and secondary pause (SP) as the longest sinus pause after incremental overdrive pacing, sinoatrial conduction time (Strauss method) (SACT), Wenckebach point (WP), and blood pressure (BP). In group I, cimetidine prolonged SCL (717 ± 98 vs 860 ± 138 msec P < 0.001), SNRT (1161 ± 153 vs 1263 ± 163 msec P < 0.002), SP (943 ± 183 vs 1072 ± 187 msec P < 0.001), SACT (121 ± 20 msec vs 149 ± 21 msec P < 0.002), and lowered rate at which AV nodal Wenckebach point were observed (169 ± 24 vs 160 ± 26 beats/min P < 0.02). The drug did not produce significant change of the CSNRT (439 ± 121 vs 402 ± 107 msec. In group II, after AB cimetidine prolonged SCL (643 ± 79 vs 656 ± 86 msec P < 0.05), SP (686 ± 114 vs 717 ± 109 msec P < 0.05) and lowered WP (170 ± 19 vs 166 ± 19 beats/min P < 0.02) significantly. The effects of cimetidine, after AB on SNRT (894 ± 180 vs 920 ± 164 msec, CSNRT (243 ± 99 vs 255 ± 85 msec), SACT (85 ± 20 msec vs 90 ± 22 msec) were not significant. We conclude that H2-receptor blockade decreases SN automatically, prolongs SACT and AV conduction in man. The study suggests that histamine takes part in regulation of electrophysiological properties of the human heart in vivo.     

The Architecture of the Atrial Musculature Between the Orifice of the Inferior Caval Vein and the Tricuspid Valve: The Anatomy of the Isthmus

Anatomy of Electrophysiologic Isthmus. Introduction : Electrophysiologists recognize a so-called "isthmus" in the right atrium through which passes the reentrant circuit of common atrial flutter. Ablative lesions placed in this narrow channel have proved effective in breaking the circuit. To the best of our knowledge, however, no study has been performed to establish the arrangement and orientation of the atrial myocardial fibers in this crucial area.
Methods and Results : We examined 28 normal heart specimens, identifying a quadrilateral area composed of three morphologic sectors between the inferior caval vein and the tricuspid valve confluent superiorly with the triangle of Koch. Within this quadrilateral, there are constant recesses, or sinuses, inferior and lateral to the orifice of the coronary sinus. The inferior isthmus measured an average of 31 ± 4 mm (range 19 to 40). Gross examination identified marked differences in the atrial wall forming the quadrilateral. A smooth anterior component forming the vestibule of the tricuspid valve was found in all the hearts, but variations in the remaining sectors were seen in ten specimens. The usually membranous posterior sector was noticeably muscular in three specimens, while the middle, trabecular sector was more membranous in five specimens. We demonstrated the orientation of the subendocardial atrial fibers by dissection in 14 specimens, revealing a relatively constant overall pattern in eight specimens and variations in fiber orientation in the remaining specimens.
Conclusion : There are considerable anatomic variations in the atrial wall that comprises the so-called isthmus. The presence of recesses and membranous areas in some hearts and the variations in arrangement of the subendocardial fibers are relevant in improving understanding of conduction in this area.     

Architecture of the Atrial Musculature In and Around the Triangle of Koch:

Atrial Fibers. Introduction : Recent studies suggest that atrial fibers in the approaches to the AV node form part of the dual pathways recognized electrophysiologically in patients with AV nodal reentrant tachycardia (AVNRT). Our aim was to determine, by gross dissection, the arrangement of the superficial musculature in the area of the triangle of Koch In normal hearts and in hearts with documented AVNRT. hoping to ascertain anatomic features that might contribute to the debate.
Methods and Results : We used blunt dissection to study the architecture of the superficial atrial musculature in 16 autopsied hearts from adults who died of noncardiac disease. A well-defined pattern of architecture of muscle fibers was found in the region of the triangle of Koch, showing marked variations in 7 of the 16 specimens. The relationship of these fibers to the histologically specialized AV node was confirmed by histology in three cases. Two hearts from patients with known AVNRT, treated by ablation in one, were examined further histologically. These sections showed that the site of ablation was well distant from the histologically discrete AV node.
Conclusion : The variability in the arrangement of the superficial atrial muscle fibers in the area of the triangle of Koch may be one of the factors influencing the route for impulses entering the AV node. Lesions that ablate nodal reentry are within these atrial fibers rather than the histologically specialized AV node.     

The management of primary fallopian tube carcinoma

Summary. The outcome of 30 patients with primary fallopian tube carcinoma is described. Treatment varied over the 22 year period of accrual and included combinations of surgery, radiotherapy and chemotherapy. There was an apparent increase in stage at treatment with time which was probably related to more precise staging at laparotomy and the greater use of computerized tomography. The median survival for all patients was 28 months and the 5-year survival was 18%. Ten patients received postoperative chemotherapy for residual disease with an overall response rate of 80% and median progression-free and overall survival times of 14 and 21 months respectively. The pattern of relapse was similar to that seen in ovarian carcinoma, with all but one patient having the pelvis or abdomen as the main site of recurrence. Primary fallopian tube carcinoma has a response to treatment and a tumour biology similar to that of ovarian carcinoma. It is recommended that the management of this uncommon malignancy should continue to be along the lines of ovarian carcinoma, with initial treatment by cytoreductive surgery followed by chemotherapy or radiotherapy for residual disease.     

Correction of spurious haematological results using Technicon H*1-derived data

Summary Two groups of patients with alert flags on the Technicon H*1 analyser, indicating erroneous results for haemoglobin and platelet determinations, were identified. These were due to turbidity from a high WBC affecting haemoglobin or small red cells affecting platelet counts. Data generated by the H*1 analyser have been utilized to derive correct Hb and platelet values; for these derivations the haemoglobin utilized the cellular haemoglobin concentration mean and for platelet counts the P COUNT was used. In a prospective study, derived haemoglobin and platelet counts were not significantly different to values obtained by standard haematological techniques. These simplified methods for correcting spurious results have allowed for speedier results and increased laboratory efficiency.     

Prediction of minimal erythema dose with a reflectance melanin meter

The relationship between skin pigmentation and sensitivity to ultraviolet (UV) radiation-induced erythema was investigated in 60 healthy subjects of sun-reactive skin types I-V. Using a portable reflectance spectrometer, skin pigmentation was measured as the melanin index (MI) in all subjects. A solar-simulated array of filtered UVA and UVB-emitting fluorescent lamps was then used to determine the UVB minimal erythema dose (MED) of each subject. MI readings and MED testing were both performed on the subjects mid to upper backs. Using this technique, we found a close correlation between MI and MED. Comparison of the mean MI or MED of subjects with different skin types revealed progressive differences in MI and MED between all five skin types. Erythema doseresponse curves, which provide further information about UV sensitivity, were also calculated for 43 subjects. A significant negative correlation was found between the gradients of these curves and both MI and MED. indicating that paler subjects respond more strongly to increments of UV above the MED than subjects with greater pigmentation. Our results indicate that although traditional, subjective means of predicting UV sensitivity to erythema are not without some value. MED correlates particularly strongly with objective measures of skin pigmentation. We therefore conclude that the reflectance spectrometer can rapidly and accurately predict UVB sensitivity, and should prove clinically useful for planning and optimizing UVB phototherapy.     

Murine alloantigen acquisition by schistosomula of Schistosoma mansoni: Further evidence for the presence of K, D, and I region gene products on the tegumental surface

Previous studies have demonstrated that shistosomula, recovered from the lungs of Schistosoma mansoni -infected mice, acquire H-2K^k and both I^k and I^s gene products. We confirmed and extended those observations by identifying several individual antigenic specificities mapping not only to H-2K^k and I-A^k (Sher, Hall & Vadas 1978), but to H-2D^k, I-E^k, H-2K^b, H-2D^b and I-A^b as well. Private H-2 specificites 23 (H-2K^k) and 32 (H-2D^k) were identified on the tegumental surface of schistosomula isolated from C3H/Crgl mice (H-2^k). Larvae isolated from C57Bl/10Sn (B10) mice (H-2^b) were shown to acquire private specificities 33 and 2, which map to H-2K^b and H-2D^b respectively. I region associated (Ia) antigens coded for by genes mapping in the I-A subregion (Ia. 2 and 3) and I-E subregion (Ia. 7) were also acquired from C3H/Crgl mice. Schistosomula from B10 donors were shown to acquire Ia specificities 3 and 8, which are under I-A subregion control. Evidence that monoclonal antibodies recognize H-2 antigens on the larval surface is also demonstrated.     

Transesophageal Echocardiography for the Prevention of Embolic Complications After Catheter Ablation for Atrial Fibrillation

Background: Thromboembolic complications during left-sided ablations range between 1.5 and 5.4%. Preprocedural TEE has been used to exclude the presence of left atrial thrombi in order to minimize risk. The use of TEE is empiric and it has not been evaluated in contemporary practice.
Methods and Results: A multicenter national survey describing the practice at 11 Canadian teaching hospitals. A total of 2,225 patients underwent elective catheter ablation for symptomatic AF. Transesophageal echocardiography (TEE) was used either routinely or selectively as a preablative strategy in patients. There were 996 patients in a routine preprocedure TEE strategy and 1,190 in a selected TEE strategy; 1 center (n = 39 patients) did not perform TEE. Twelve of 996 (1.2%) in the routine unselected cohort had thrombi identified. TEEs were performed in 200 of 1,190 in the selected cohort; 4 (2.0%) left atrial thrombi were observed; there was no significant difference in the prevalence of thrombi (P = 0.34). A total of 11 embolic events occurred inclusive of all groups. There was no difference in event rates between the 2 strategies (0.6% and 0.4%, P = 0.54). Events were unrelated to AF duration (persistent vs paroxysmal, r = 0.03, N = 2,225, P = 0.9).
Conclusion: The selection criteria employed to perform TEEs did not increase the chance of identifying LA thrombi in a patient cohort with primarily nondilated left atria and paroxysmal AF. The overall thromboembolic event rate was low (0.49%) and was not significantly different between the 2 TEE strategies.