Michael E. Ring

Hemostatic markers in acute stroke.

To assess the time course of thrombosis and fibrinolysis after acute stroke, we measured concentrations of fibrinopeptide A (FpA), B-beta 1-42 peptide (B-beta 1-42), B-beta 15-42 peptide (B-beta 15-42), and crosslinked D-dimer (XDP) in 31 patients at varying times following acute ischemic stroke and in 13 neurologically stable patients with chronic strokes. FpA levels were markedly elevated during the first week after stroke and declined slowly during the first month. Mean FpA levels were not significantly elevated in chronic stroke patients. Mean XDP levels were slightly elevated during the first week and increased during the next 2 weeks after stroke. B-beta 1-42 and B-beta 15-42 levels were not elevated at any time following acute stroke. Our data suggest that fibrin formation greatly exceeds endogenous fibrinolysis during the acute phase of ischemic stroke. Endogenous fibrinolysis develops slowly following stroke. Prolonged elevation of FpA concentration suggests that thrombin activity and fibrin formation continue for up to 4 weeks in some patients with ischemic stroke.

Comparison of catheter ablation using radiofrequency versus direct current energy: Biophysical, electrophysioiogic and pathologic observations☆

The effects of catheter ablation with radiofrequency versus direct current energy were compared in 18 dogs assigned to two groups (of 9 dogs each). Each dog underwent a single ablation at two sites in the left ventricle at energy levels of 100, 200 or 300 J delivered in unipolar configuration to six dogs each. A transient decrease in left ventricular systolic pressure (from 121.3 +/- 24.5 to 94.2 +/- 18.7 mm Hg, p less than 0.01) and wall motion abnormality were noted in dogs with direct current shock. The left ventricular ejection fraction decreased (from 50 +/- 2% to 34 +/- 3%, p less than 0.001) shortly after direct current ablation but improved 4 weeks later to 43 +/- 3%. There were no significant changes in left ventricular pressure, wall motion or ejection fraction in dogs in the radiofrequency ablation group. Sustained ventricular tachycardia (greater than or equal to 30 s) was seen immediately after direct current shock in all dogs, and one dog died of intractable ventricular fibrillation. A 24-h ambulatory electrocardiographic (ECG) monitor obtained immediately after the procedure showed multiple runs of ventricular tachycardia in all dogs exposed to direct current ablation but in only three dogs that underwent radiofrequency ablation. No differences were found in peak creatine kinase, complete blood count with smear and B-beta 15-42 fibrinopeptide levels. Pathologically, direct current-induced lesions were larger (mean length x width x depth 10.9 x 7.5 x 5.2 vs. 4.8 x 4.6 x 4.3 mm) and were poorly circumscribed with inhomogeneous margins of necrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheter ablation of the ventricular septum with radiofrequency energy

The safety and feasibility of performing catheter ablation of the ventricular septum with radiofrequency energy was assessed in a closed-chest canine model. Radiofrequency energy (750 kHz) was delivered in a bipolar manner via the distal electrodes of two quadripolar catheters positioned across the ventricular septum in 10 dogs at two sites. Each site received from 159 to 823 joules of delivered energy over one to three applications. Four additional dogs underwent unipolar radiofrequency ablation with 331 to 767 joules of delivered energy to each septal site. No significant acute or latent arrhythmias were noted. Dogs were killed at 1 day, and at 1, 2, and 4 weeks after the procedure. Out of a possible 40 potential ablation sites on each side of the septum after bipolar ablation, 21 (53%) discrete endocardial lesions were identified, ranging in size from 4 x 3 x 1.5 to 10 x 8 x 4 mm. When 352 joules or more delivered energy was applied per site, lesions were located at 18 of 28 (64%) possible sites. After unipolar radiofrequency ablation, similarly sized lesions were identified at 15 of 16 (94%) ablation sites. Histologic examination demonstrated well-delineated round or ovoid-shaped lesions with microscopic thrombi overlying two lesions. In conclusion, catheter ablation of the ventricular septum with radiofrequency energy appears capable of safely producing discrete areas of necrosis and may provide an alternative to direct current (DC) energy for catheter ablation of ventricular tachycardia originating from the septum.

Clinically significant antiplatelet effects of calcium-channel blockers

719 #{149} J Clin Pharmacol 1986;26:719-720 when the patient was receiving both verapamil and lithium. Removal of the verapamil resulted in a rapid clearing of the symptoms, whereas a rechallenge with verapamil caused an equally rapid reappearance of neurotoxicity. Certainly more research is needed to elucidate the mechanism of action behind this synergism. Until then, care should be taken when combining lithium carbonate and other calcium-channel blockers.

REWARDS TLX: REGISTRY EXPERIENCE AT WASHINGTON HOSPITAL CENTER: TAXUS LIBERTÉ VS XIENCE V

Methods: The study included a US all-comers population treated with either TL or XV stents, at 10 sites. Patients receiving TL (n=595) and XV (n=600) were compared at 1-year post-implantation. The primary endpoint is major adverse cardiac events (MACE), a composite of all-cause death, Q-wave myocardial infarction, and target vessel revascularization. Secondary endpoints include stent thrombosis, target lesion revascularization and cardiac death. There is also a subanalysis comparing diabetics and nondiabetics.