Anomalous "VVI" Pacing of a Dual Chamber Pacemaker When Programmed in DDI(R) Mode

We describe the case of a dual chamber rate responsive pacemaker (Relay, model 294-03, Intermedics, Angleton, TX, USA) implanted in a 68-year-old male for sick sinus syndrome, which was not working properly when programmed in the DDIR mode, thus determining occasionally a sort of "VVI" pacing. However, the pacemaker performed well when programmed in the DDDR mode. We discovered that this was not a malfunction of a single device but rather a general behavior of this family of Intermedics dual chamber pacemakers (also not rate responsive), caused by a software problem.     

LOCAL MICROWAVE HYPERTHERMIA AND INTRAVESICAL CHEMOTHERAPY AS BLADDER SPARING TREATMENT FOR SELECT MULTIFOCAL AND UNRESECTABLE SUPERFICIAL BLADDER TUMORS

Purpose

The role of a combined regimen of local hyperthermia and topical chemotherapy in patients with multifocal and recurrent superficial bladder tumors not curable by transurethral resection was evaluated in a neodjuvant organ sparing clinical study.

Materials and Methods

A total of 19 patients with multifocal, superficial grades 1 to 3 bladder tumors that recurred after intravesical chemoprophylaxis or immunoprophylaxis underwent local combined administration of microwave induced hyperthermia and intravesical chemotherapy as a debulking approach. Due to extensive superficial involvement of the bladder walls complete transurethral resection of all tumors seemed technically unfeasible in all cases and radical cystectomy was considered the treatment of choice. Endovesical hyperthermia at 42.5 to 46C was delivered using the SB-TS 101 system,* based on a microwave transurethral applicator that irradiates the bladder filled with a circulating solution of mitomycin C. Patients underwent 8 weekly 1-hour sessions on an outpatient basis without anesthesia. When possible, after treatment patients underwent transurethral resection of residual tumors and all suspicious areas.*Boston Scientific Corp., Natick, Massachusetts.

Results

After treatment transurethral resection appeared to be feasible and curative in 16 patients (84%). Histological study revealed complete and partial responses in 9 (47%) and 7 (37%) cases, respectively. Due to extensive residual tumors radical cystectomy was performed in 3 patients (16%). At a median 33-month followup 8 superficial transitional tumor recurrences were documented and easily eradicated by transurethral resection or laser therapy in patients in whom the bladder had been saved.

Conclusions

Microwave induced hyperthermia combined with intravesical mitomycin C seems to be a feasible, safe and elective approach for conservative treatment of multifocal and recurrent superficial bladder tumors when other treatment strategies have failed.     

Persistent production of platelet thromboxane A2 in patients chronically treated with aspirin

BACKGROUND: Patients treated with aspirin may have a reduced sensitivity to its antiplatelet effect. The mechanism accounting for such a reduced sensitivity might involve an impaired interaction of aspirin with cyclooxygenase-1 (COX)-1. OBJECTIVE: We sought to investigate whether platelets from patients under chronic treatment with aspirin still produce TxA2 and whether there is any relationship between the eventual persistent TxA2 formation and platelet aggregation. Finally, whether platelet-derived TxA2 can be inhibited by in vitro addition of aspirin. METHODS: Collagen-induced platelet aggregation and thromboxane-A2 (TxA2) were measured in 196 patients treated with aspirin (100-330 mg day(-1)) because of previous vascular events or presence of risk factors of atherosclerosis. RESULTS: Collagen-induced TxA2 production of the entire cohort was 128.7 +/- 21.6 pg 10(-8) cells, and was significantly correlated with platelet aggregation (Spearman's correlation coefficient = 0.44; P < 0.0001). Patients in the highest quartile of TxA2 showed higher platelet response to collagen (P < 0.0001) when compared with those in the lowest quartile. In a subgroup of 96 patients, platelets were treated in vitro with a TxA2 receptor antagonist (13-azaprostanoic acid) or aspirin before stimulation with collagen. 13-APA acid significantly inhibited platelet aggregation. Aspirin reduced (-72.9%) TxA2 production in patients with TxA2 values above the median but it was ineffective in those with TxA2 values below the median. CONCLUSION: In some patients chronically treated with aspirin platelet production of TxA2 may persist and account for enhanced platelet aggregation. Incomplete inhibition of COX-1 seems to be implicated in persistent TxA2 production.     

Variations in Human Atrial Flutter Cycle Length Induced by Ventricular Beats: Evidence of a Reentrant Circuit with a Partially Excitable Gap

Variations in Atrial Flutter Cycle Length. Introduction : The purpose of this investigation was to study the mechanisms responsible for small variations in atrial flutter cycle lengths. Methods and Results : In a study group of 11 patients with common atrial flutter, atrial electrograms were recorded from an intraesophageal lead together with a surface lead (V₁). Upon the onset of the QRS complex, atrial flutter intervals consistently increased by an average of 1.8% (SD± 0.9; P <0.01) and subsequently decreased by 2.1% (SD ± 0.8; P <0.01) before returning to the average flutter rate. Carotid sinus massage, which temporally prevented ventricular activation, markedly reduced the variations in atrial flutter intervals. Ventricular pacing at different rates clearly demonstrated that the pattern in atrial flutter intervals was coupled to the moment of ventricular contraction. The hypothesis was formulated that these periodic variations in atrial flutter intervals following a ventricular contraction were caused by the influence of stretch of the atrial myocardium on the conduction properties of a circulating impulse in the atrium. The secondary decrease in flutter rate could be explained if a partial excitable gap is assumed between head and tail of the circus movement. This hypothesis was tested in a simulation study, which revealed that the alternation in intervals as found in patients could only be reproduced if the excitable gap in the circus movement was partially excitable. Conclusion : In conclusion, the analysis of variations in atrial flutter cycle lengths points to a mechanism of circus movement with a partially excitable gap in common atrial flutter.     

A promoter mutation, C → T at position -92, leading to silent /3-thalassaemia

Summary. This study describes the clinical phenotype of the C?→? T mutation at position – 92 of the β-globin gene. Excluding two cases with HbA2 levels within the range of the /3-thalassaemia carrier state, heterozygotes for this mutation showed normal or borderline red blood cells count, Hb levels, MCV, MCH and HbA2 values, and unbalanced globin chain synthesis. Compound heterozygotes for the - 92 C → T mutation and a β° thalassaemia mutation (β°39) (two cases) or severe β-thalassaemia (p⁺ IVSII nt 745) (two cases) developed thalassaemia intermedia. According to these characteristics, the –92 promoter mutation should be added to the list of silent β-thalassaemias.     

Δ‐CHr improves the identification of anemic syndromes and the evaluation of hemoglobin synthesis

Reticulocyte hemoglobin content (CHr) is considered an index of iron status, helpful in the differential diagnosis of microcytoses. Its potential can be enhanced by comparing CHr dynamic reference values (CHr‐e: expected CHr), which are proportional to the MCVr variations occurring in micro‐ or macrocytosis, with measured CHr values. We demonstrate that the difference between measured CHr and CHr‐e (ΔCHr) is helpful to differentiate the anemic syndromes and, in particular, β‐talassemia vs. presumable sideropenia. ΔCHr can also indicate when to interrupt iron supplementation. ΔCHr allows an insight into the erythropoiesis of thalassemic and sideropenic subjects, pointing out the reduced hemoglobin production and ineffective erythroid activity in these conditions.     

Failures of common measures of agreement in medicine and the need for a better tool: Feinstein's paradoxes and the dual vision method

The main objective of the present report is to show failures in binary cases of the kappa, Yule and phi approaches when used for measuring agreement beyond chance. These methods were designed for studying the statistical concept of agreement, and for this reason they may fail when used in clinical situations. To solve these problems, or paradoxes, a new method for studying agreement is used—the dual vision procedure. The capacity of the new method to solve the paradoxes that other approaches cannot solve is demonstrated. The study of agreement is used to decide whether one clinical method can replace another one. An incorrect replacement could be dangerous for the patient. These failures caused by kappa, Yule or phi assessment are illustrated by using the clinical concept of agreement.