It is well known that heart rate is a key determinant of ischemia.1 ( Figure 1) Elevated resting heart rate and increase in heart rate due to any triggering factor like stress, in patients with diminished blood flow to the heart as a result of arteriosclerosis, deprives the heart muscle of oxygen. Depending on the severity of atherosclerosis, it can manifest clinically as angina or myocardial infarction. This could lead to insufficient heart muscle function, or even death of heart muscle, resulting in congestive heart failure. Slowing the heart rate reduces the heart’s need for oxygen. Simultaneously, slowing the heart rate also increases the diastolic time, and thus increases the hearts oxygen supply.

HeartRate01

Figure 1. The likelihood of ischemic episodes increases with increasing heart rate

References :

1. Andrews TC, Fenton T, Toyosaki N, et al. Subsets of ambulatory myocardial ischemia based on heart rate activity. Circadian distribution and response to antiischemic medication. The Angina and Silent Ischemia Study Group (ASIS). Circulation. 1993;88:92-100.