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The term "linking" has been used specifically to describe the mechanism for perpetuation of functional anterograde bundle branch block: namely, repetitive transseptal retrograde concealed penetration by impulses propagating along the contralateral bundle. We present selected examples that demonstrate that linking-type phenomena actually have a wide spectrum of expression in human macroreentry circuits, particularly those incorporating either the bundle branches and His bundle or the normal pathway and Kent bundle. The examples presented are as follows: (1) Circulation 71, No. 2, 254-265, 1985.

There are few studies on the relationship between socio-economic factors and rheumatic fever (RF) in the populations where the burden of both socio-economic deprivation and RF is still very high. The aim of this study is to assess the association between some socio-economic factors and RF by examining data available from a RF hospital in Bangladesh. We have reviewed the medical records of patients presenting with manifestations suggestive of RF during a 1-year period. From the patients who showed group A beta-haemolytic streptococcal upper respiratory infection (ABHS infection), 44 RF cases defined by the Jones criteria and 86 control subjects, who did not satisfy the criteria, were identified for analysis. The median age was 12 years and 60% were female. RF was significantly associated with low income (odds ratio [OR] 2.37; P = 0.04); poor living conditions: substandard (kacha) house (OR 2.93, P = 0.02); and poor nutritional status: low height for age (OR 2.68, P = 0.02). Multiple logistic regression analysis revealed an increased OR for kacha house (OR 3.18, P = 0.02) but the same estimate for low height for age (OR 2.68; P = 0.04). Our analysis shows that, among the patients presenting to the RF hospital with proven ABHS infection, acute RF is associated with socio-economic deprivation.

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SUMMARY Animal studies have suggested that spontaneous or programmed ventricular beats that occur simultaneously with atrial activation may facilitate atrioventricular (AV) nodal conduction during subsequent atrial impulses. However, this possibility has not been systematically studied in the human heart. In the present study the AV nodal conduction during a programmed atrial premature beat (S2) was analyzed.The S2 was delivered after a series of atrial drive beats (SjSj) of constant duration; this was termed stimulation method I. The results were compared with stimulation method II, which was similar to method I except that a single ventricular beat (Vs) was introduced simultaneously with the last Sl. The longest and shortest possible paced atrial cycle lengths (CLs) were scanned during both methods. Twenty-six patients were studied: 14 with a normal PR and normal intraventricular conduction (NIVC), four with first-degree AV nodal block and NIVC, three with a complete left bundle branch block (LBBB) pattern, three with a complete right bundle branch block (RBBB) pattern, and two with an incomplete RBBB pattern.At the same SlS2 intervals, the AV nodal conduction times (S2112 intervals) were consistently shorter with method II than with method I except in three patients, two with complete RBBB and one with complete LBBB. The magnitude of S2H2 shortening with method II was more pronounced at the shorter basic CLs and shorter SlS2 intervals. During method I, the effective refractory period (ERP) of the AV node was measured in 13 patients, eight with NIVC and five with preexisting bundle branch block. With method II, the ERP of the AV node shortened in all but three patients (one with complete RBBB, one with incomplete RBBB and one with complete LBBB pattern), in whom this variable did not change. The findings suggest that intranodal collison from antegrade and retrograde impulses facilitates AV nodal conduction and shortens the ERP. The magnitude of this change is greater at shorter atrial CLs and is probably related to deeper intranodal penetration of a Vs. The shortening in AV nodal conduction and refractoriness is not noted in patients with bundle branch block when retrograde conduction delay or block in the bundle branches coexists with the antegrade counterpart producing delayed or ineffective input of Vs into the AV node.ATRIOVENTRICULAR (AV) nodal conduction and refractoriness in the antegrade direction have been extensively investigated in both animals and man.'-'0 Although several studies have addressed the effects of programmed ventricular premature stimulation on subsequent AV nodal conduction in animals,9' 11 rarely has such a study been carried out systematically in the human heart. This study was designed to examine the effect of simultaneous AV stimulation on the functional properties of the AV node in man. Patients and MethodsTwenty-six patients ( ously introduced through the femoral and antecubital veins and were positioned under fluoroscopic guidance, in the region of the tricuspid valve to permit...