Exercise Testing and Indirect Assessment of Myocardial Oxygen Consumption in Evaluation of Angina Pectoris

Abstract

Exercise testing is an important means of evaluating the patient with angina pectoris, providing objective data not available from conventional clinical assessment. In utilizing exercise to determine functional impairment in angina, it is essential to distinguish between external stress, or the load on the skeletal muscles, and internal or cardiac stress. Evaluation of external exercise capacity alone is limited as a measure of cardiac performance since the relationship between external function and cardiac performance is not necessarily direct. A readily applicable approach to determination of cardaic capacity in angina is afforded by indirect assessment of myocardial oxygen consumption (MVO₂). This is achieved through derived indexes utilizing heart rate and blood pressure, two major determinants of MVO₂, in the form of the product of heart rate and systolic blood pressure. Although this approach does not encompass all the major determinants of MVO₂, changes in the heart rate-blood pressure product bear a close correlation to alterations in directly measured MVO₂. Within limits and employed with caution, indirect assessment of MVO₂ is useful in elucidating mechanisms of action of extracardiac and intrinsic myocardial factors in the provocation and therapy of angina pectoris.

Systolic pulmonary artery pressure and heart rate are main determinants of oxygen consumption in the right ventricular myocardium of patients with idiopathic pulmonary arterial hypertension

“…7 In addition, Katz and Feinberg also observed a relationship between the RPP and LV MVO 2 . 8 Since then, these observations have been validated in healthy subjects 4,6 as well as in patients with left heart disease, 25,26 both HR and systolic pressure appear to be weaker than for LV studies. The weaker correlation could have a methodological cause, e.g.…”

Acute Antianginal Effect of Tiapamil

“…The maximal PRP remained unchanged in spite of increased ET. These findings tend to indicate a stationary MVO2 and, thus, an unchanged total myocardial oxygen supply [17,18] after tiapamil. The fact that, with a constant maximal PRP where exercise was limited by AP without medication, none or fewer episodes of AP occurred after tiapamil, indicates that a lower oxygen demand and/or an increment in regional oxygen supply to the ischemic myocardium was induced by this agent.…”

“…Coronary insufficiency reflects an imbal ance between myocardial oxygen supply and demand [17], AP always occurs when an individual critical value for myocardial oxy gen consumption (MVO2) is achieved [17,18]. As MVO2 is not easily measured direct ly, the PRP is commonly used as an indirect index [18,19].…”

“…As MVO2 is not easily measured direct ly, the PRP is commonly used as an indirect index [18,19]. PRP correlates reasonably well with MVO2 and is reproducible for a given patient [17.…”

“…The peak work load was expressed in watts and. if performed for less than 120 s. was assessed by interpolation between the two last work loads [16], For the estimation of myo cardial oxygen consumption, the pressure-rate product (heart rate X systolic blood pressure X I0"2) was cal culated [17][18][19]. Exercise ECG with horizontal or de scending S-T depression of more than 0.1 mV and 80 ms duration or longer was considered abnormal.…”