Effect of Heart Rate, Exercise, and Nitroglycerin on the Cardiac Dynamics in Complete Heart Block.

THE PRESENCE of complete heart block offers a good opportunity to study cardiovascular functions, since one of the major variables of cardiac activity, i.e., heart rate, is maintained constant.113 In addition, if a cardiac pacemaker is implanted in a heart for treatment of complete heart block,14-20 total control of the cardiac rate is achieved, thereby providing an excellent opportunity for studying cardiovascular hemodvnamics under a variety of fixed rates. The present study was unidertaken (1) to attempt to establish the most appropriate heart rate for permanent pacing; (2) to ascertain the hemodynamic consequences of complete heart block at a fixed slow heart rate, and the effect of increasing heart rate; (3) to determine the effects of exercise and nitroglycerin on the cardiac dynamics at various fixed heart rates. A patient with complete heart block resulting from coronary artery disease was studied.