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A 52-years old man with a previous pericardiotomy for idiopathic constrictive pericarditis underwent catheter ablation for drug-resistant atrial tachycardia (AT). The mechanism of the AT was considered as reentry because of resetting response and the entrainment phenomenon during AT. We introduced a 64-electrode basket catheter into the superior vena cava (SVC) during AT to obtain precise mapping. A fractionated potential preceding local atrial electrogram was recorded in the SVC. The earliest activation site of the potential was located at the anterior aspect of the SVC, 2 cm above the SVC-right atrium junction determined fluoroscopically. The fractionated potential at this site preceded the onset of the P wave by 115 msec. Radiofrequency catheter ablation at this site eliminated the tachycardia. At 6 months follow-up, the patient is free of AT. Reentrant AT involving the SVC is a candidate of RF ablation. Multielectrode basket catheter is useful for a detailed mapping of the SVC.

Dynamic viscoelasticity of α,ω-dihydroxyl polybutadiene/p-xylene system is studied through gelation process by end-crosslinking reaction with crosslinker which has three isocyanate groups. The gel point is determined as the reaction time t=t c 1 at which the storage and the loss shear moduli, G'(ω) and G(ω), become both proportional to ω over the whole ω range measured, where ω is the angular frequency and n is a critical exponent at the gel point. The relative extent of chemical reaction p(t) is estimated from a decrease in the absorption peak of the isocyanate residue by FT-IR measurement to estimate precisely e=(p(t)-p|/p c 1 the relative distance from the gel point (p=p c ). Effects of polymer concentration C on the increase of zero shear viscosity η o before the gel point and on the increase of equilibrium modulus G eq after the gel point are examined in terms of critical exponents of k and z for power laws, η o ∼ e -k and G eq ∼ e z , respectively. The exponents n and z are found to take universal values of n=0.67±0.02, and z= 2.5 ± 0.1 independent of C in the lower concentration of C