Alternating Wenckebach Periods and Allied Arrhythmias

Alternating Wenckebach periods (AWPs)are episodes of 2:1 block during which Ihe PR, AH, or AV intervals of the conducted beats gradually increase until a greater degree of block ensues. Most episodes occur at the AVnode, but some have aiso been reported in other structures. AWPs are usually attributed to multilevel block due to transverse (horizontal)dissociation. This assumption was initially based on a method in which the solutions to difficult electrocardiographic rhythms were arrived at by analysis and deduction based on the knowledge existing at that particular time. Subsequently, it was reinforced by information extrapolated from intracardiac recordings performed in patients with documented multilevel block in separate anatomical structures (atria, AV node, and His bundle), as well as from microelectrode studies and computer simulations. Although AWPs are frequently observed in clinical tracings, those occurring at the AV node are best categorized during incremental atrial stimulation because then they occupy a specific point in the wide spectrum of tachycardia dependent AV nodal conduction disturbances. In fact, the A:H ratios occurring in the episodes where the degree of block increases can be represented by “universal” mathematical formulas. However, in the clinical setting, drugs affecting the electrophysiology of the node can alter the pacing induced symmetry by producing additional differential effects on the various levels. The latter still requires further elucidation

A COMPARISON OF INTERNAL MAMMARY ARTERY AND SAPHENOUS-VEIN GRAFTS AFTER CORONARY-ARTERY BYPASS-SURGERY - NO DIFFERENCE IN 1-YEAR OCCLUSION RATES AND CLINICAL OUTCOME

Background Superior patency rates for internal mammary artery (IMA) grafts compared with vein coronary bypass grafts have been demonstrated by retrospective studies. This difference may have been affected by selection bias of patients and coronary arteries for IMA grafting. Methods and Results To estimate the difference between IMA and vein grafts, we analyzed graft patency data of 912 patients who entered a randomized clinical drug trial. In this trial, 494 patients received both IMA and vein grafts (group 1) and 418 only vein grafts (group 2). Occlusion rates of IMA grafts and IMA plus vein grafts in group 1 were compared with those of vein grafts in group 2. Multivariate analysis was used to compare occlusion rates of IMA and vein grafts while other variables related to graft patency were controlled for. In addition, 1-year clinical outcome was assessed by the incidence of myocardial infarction, thrombosis, major bleeding, and death. Occlusion rates of distal anastomoses in group 1 versus group 2 were 5.4% (IMA grafts) versus 12.7% (vein grafts) (P Conclusions The observed difference in 1-year occlusion rates between IMA and vein grafts can be explained by a maldistribution of graft characteristics by selection of coronary arteries for IMA grafting rather than being ascribed to graft material. One-year clinical outcome is not improved by IMA grafting

A COMPARISON OF INTERNAL MAMMARY ARTERY AND SAPHENOUS-VEIN GRAFTS AFTER CORONARY-ARTERY BYPASS-SURGERY - NO DIFFERENCE IN 1-YEAR OCCLUSION RATES AND CLINICAL OUTCOME

Background Superior patency rates for internal mammary artery (IMA) grafts compared with vein coronary bypass grafts have been demonstrated by retrospective studies. This difference may have been affected by selection bias of patients and coronary arteries for IMA grafting. Methods and Results To estimate the difference between IMA and vein grafts, we analyzed graft patency data of 912 patients who entered a randomized clinical drug trial. In this trial, 494 patients received both IMA and vein grafts (group 1) and 418 only vein grafts (group 2). Occlusion rates of IMA grafts and IMA plus vein grafts in group 1 were compared with those of vein grafts in group 2. Multivariate analysis was used to compare occlusion rates of IMA and vein grafts while other variables related to graft patency were controlled for. In addition, 1-year clinical outcome was assessed by the incidence of myocardial infarction, thrombosis, major bleeding, and death. Occlusion rates of distal anastomoses in group 1 versus group 2 were 5.4% (IMA grafts) versus 12.7% (vein grafts) (P Conclusions The observed difference in 1-year occlusion rates between IMA and vein grafts can be explained by a maldistribution of graft characteristics by selection of coronary arteries for IMA grafting rather than being ascribed to graft material. One-year clinical outcome is not improved by IMA grafting