Management of the heart rate during coronary artery bypass grafting on the beating heart: newly devised methods of decreasing heart rate--a preliminary report-.
BACKGROUND
To develop new methods for achieving bradycardia, we studied the feasibility of producing transient, reversible bradycardia with atrial stimulation and cooling of the sinoatrial node.


METHODS
In an animal study, the atrium was stimulated electrically during the refractory period of the atrioventricular node. Alternatively, an area of the sinoatrial node was cooled regionally. The two methods were also performed in combination. In a clinical study, atrial stimulation was applied in seven consecutive patients who underwent coronary artery bypass grafting (CABG).


RESULTS
In the animal study, atrial stimulation was effective only when 2 mg/kg of diltiazem was administered. Such atrial stimulation decreased heart rate (beats/minute) from 95.8+/-16.9 to 64.2+/-20.0 (the average reduction from the control value 66.1+/-10.3%). Cooling the sinoatrial node decreased heart rate, and was effective with or without administration of diltiazem. Heart rate was decreased from 156.6 31.7 to 110.7+/-21.7 (average reduction from control value 71.3+/-9.2%) before using diltiazem and from 102.0+/-11.9 to 63.5+/-13.9 (average reduction from control value 62.0+/-10.4%) after administration of diltiazem. By combining the two methods, heart rate was decreased from 102.0+/-12.3 to 44.6+/-9.1 (average reduction from control value 43.5+/-6.3%). In our clinical study, the atrial stimulation method was effective.


CONCLUSIONS
Atrial stimulation or regional cooling of the sinoatrial node slowed the heart rate. By combining the two methods, the heart rate was slowed to 40. Clinically, atrial stimulation was effective in CABG patients.
Kuniyoshi
Y
Y
Second Department of Surgery, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara-cho, Okinawa 903-0215, Japan.
Koja
K
K
Miyagi
K
K
Mistuyoshi
S
S
Uezu
T
T
Arakaki
K
K
Yamashiro
S
S
Mabuni
K
K
Haneji
S
S
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002121:Calcium Channel Blockers / Q000008:administration & dosage; D001026:Coronary Artery Bypass / Q000379:methods*; D003327:Coronary Disease / Q000503:physiopathology / Q000601:surgery*; D004110:Diltiazem / Q000008:administration & dosage; D004285:Dogs; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006324:Heart Arrest, Induced / Q000379:methods*; D006339:Heart Rate; D006801:Humans; D008297:Male; D009200:Myocardial Contraction; D012849:Sinoatrial Node
D002121:Calcium Channel Blockers; D004110:Diltiazem