[A basic study on bradycardiac dysrhythmias following atrial surgery].

Various dysrhythmias often developing atrial surgery can be lethal, although the precise mechanism remains unknown. An experimental study was conducted to elucidate the influence of internodal tract injury and sinoatrial node (SAN) artery blockade on bradycardiac arrhythmias, using 40 adult mongrel dogs. Changes in rhythm, SAN tissue flow rate, SAN function and His bundle electrocardiogram were evaluated in those with complete division of the internodal tract (INT) and/or artery blockade under cardiopulmonary bypass. The results were as follows: 1) Junctional rhythm (JR) or ectopic atrial rhythm (ER) occurred in 87.5% of those subjected to anterior INT (AINT) division+SAN artery blockade, whereas such arrhythmias developed in none of those with division of any single INT alone, and appeared in only 18% of those with SAN artery blockade alone; 2) The SAN tissue flow rate was reduced to 29 +/- 17% of the control level by AINT division+SAN artery blockade, while it was reduced to only 91 +/- 16%, 84 +/- 12% and 90 +/- 18% by division of AINT, MINT and PINT, respectively, and 55 +/- 16% by SAN artery blockade (The former was significantly lower than the latter two (p < 0.01)); 3) None of those with the SAN tissue flow rate of less than 10 Laser Doppler Flowmeter unit (LDF unit) by laser Doppler flowmeter output were capable of maintaining sinus rhythm (SR) with its minimum requirement that was assumed to be more than 10 LDF unit; 4) Immediately before shifting to JR, corrected sinus recovery time (CSRT) was elongated, indicating a hypofunction of the SAN; 5) The A-H interval was more significantly prolonged by AINT division than by either of the other two divisions (p < 0.01). Division of the AINT brought about prolongation of the A-H interval, and AINT division+SAN artery blockade caused a marked SAN hypofunction. It was inferred that preservation of both the AINT and the SAN artery should be of vital importance in preventing surgical bradycardiac arrhythmias.