Bilateral atrial myxomas. Surgical correction after echocardiographic diagnosis

A case is reported of bilateral atrial myxomas diagnosed noninvasivelyby echocardiography and successfully removed. The excised tumormass consisted of a mobile right atrial myxoma prolapsing intothe right ventricle and a less mobile, not prolapsing myxomain the left atrium. The operation was performed entirely onthe basis of echocardiographic findings, which correlated wellwith the operative results. Further investigation by computertomography verified the diagnosis, but added no extra informationof importance for therapy. Diagnostic aspects of the combinedapplication of M-mode and cross-sectional echocardiography withDoppler echocardiography are emphasized. Postoperative follow-upechocardiography showed the complete removal of the myxomasand improvement of cardiac function.     

Electrophysiological Studies on Cardiac Catheter Ablation

Clinical and animal investigations have pointed out that high energy electrical shocks are associated with the development of cardiac arrhythmias and with variable success in permanent ablation. The effects of electrode configuration and location on the size of the recorded electrogram was investigated to help explain variable catheter ablation results. We analyzed the cellular effects of catheter ablation shocks and found depression of resting potential, action potential amplitude, dV/dt and action potential duration. The most severe effects were noted with high current densities in tissues located between the cathode and anode. Damage was worse nearest the cathode. Similar cellular studies were completed using argon laser photoablation. Again, there was a decrease in resting potential, action potential amplitude and dV/dt. Laser energy led to a more focal region of myocardium void of action potentials and the border zone of injury was smaller. We also investigated the effects of lower energy shocks)1 to 10 joule) on cardiac tissues. Using microelectrodes, we observed that the membrane potential can "hang up" at the depolarized levels for varying periods of time and that conduction is altered during this membrane "hang-up" period. The duration and membrane hang-up level correlated with shock intensity and shock duration. Sequential shocks resulted in additive membrane "hang-up". We believe that membrane hang-up may be associated with brief arrhythmias observed following catheter ablation since conduction, refractoriness and excitability are all altered.