SHORT-TERM EFFECTS OF RIGHT ATRIAL, RIGHT-VENTRICULAR APICAL, AND ATRIOVENTRICULAR SEQUENTIAL PACING ON MYOCARDIAL OXYGEN-CONSUMPTION AND CARDIAC EFFICIENCY IN PATIENTS WITH CORONARY-ARTERY DISEASE

Objective-To investigate the short-term effects of atrial, atrioventri cular, and ventricular pacing on myocardial oxygen consumption, myocar dial blood flow, and cardiac efficiency in patients with coronary arte ry disease. Design-Prospective study that started at the end of diagno stic coronary angiography in 13 patients and was performed during atri al, atrioventricular, and ventricular pacing for 5 min, in random orde r, at 20 beats/min more than the heart rate of the patient's positive exercise test. A Baim thermodilution catheter in the coronary sinus wa s used to measure myocardial blood flow and oxygen consumption and a p acing electrode at the right ventricular apex and a catheter in the pu lmonary artery were used to estimate cardiac output. Setting-Referral cardiology centre. Patients-13 patients with coronary artery disease ( mean (SD) age 53(5) years). All the patients had a positive exercise t est and most of them (77%) had left anterior descending coronary arter y disease. Results-Mean (SD) cardiac output increased by 0.5(1.6) 1/mi n during atrial pacing, increased by 0.1(1) 1/min during atrioventricu lar pacing, and decreased by 0.8(1.2) 1/min during ventricular pacing (P = 0.01 v atrial pacing, P = 0.03 v atrioventricular pacing). Diasto lic pulmonary pressure increased by 6(4) mm Hg during atrial pacing, b y 8.6(4) mm Hg during ventricular pacing (P = 0.02 v atrial pacing), a nd by 7.5(4.7) mm Hg during atrioventricular pacing. Changes in myocar dial oxygen consumption and cardiac efficiency during the different pa cing modes were similar. Conclusion-Atrial, atrioventricular, and vent ricular pacing had similar shortterm effects on myocardial oxygen cons umption, myocardial blood flow, and cardiac efficiency in patients wit h coronary artery disease. Ventricular pacing, however, did not increa se cardiac output.