How does progressive elevation of heart rate by atrial pacing affect coronary hemodynamics in patients with coronary artery disease compared to those with normal coronary arteries?
Patients with coronary artery disease can exhibit normal coronary blood flow and resistance responses to increased metabolic demand up until the point of coronary insufficiency and angina.
Coronary sinus blood flow was studied by the continuous thermodilution method in 13 subjects with normal coronary arteries and 14 patients with coronary artery disease during progressive elevation of the heart rate by atrial pacing. In 11 patients of the coronary group angina pectoris developed during pacing. In subjects with normal coronary arteries the coronary sinus blood flow rose proportionately (1.71 ± 0.19 ml/beat) and the coronary resistance decreased proportionately (0.06 ± 0.01 See Equation in PDF File beats) to the rise in heart rate. Similar changes in coronary sinus blood flow and coronary resistance were found in the pain-free pacing periods in patients with coronary artery disease (1.79 ± 0.21 ml/beat and 0.07 ± 0.01 see Equation in pdf file/10 beats, respectively). However, in the periods in which anginal pain was induced the changes in both flow and resistance were significantly lower than in either the noncoronary group or in the pain-free periods in the coronary group (0.66 ± 0.16 ml/beat and 0.00 ± 0.01See Equation in PDF File/10 beats, respectively). The study shows that the coronary blood flow in patients with coronary artery disease not only can be normal at rest, but the coronary bed as a whole can respond to increased metabolic demand by normal increases in flow and normal decreases in resistance up to the point at which coronary insufficiency develops.
Yoshida et al. (Wed,) studied this question.