Exercise applications Flashcards
Describe the major determinants of myocardial oxygen supply and demand.
supply: coronary blood flow, perfusion pressure, vascular resistance, oxygen content. Demand: wall stress (pxr /2h), heart rate, contractility
What is the relationship between myocardial oxygen demand (MVO2) and coronary blood flow and oxygen extraction?
Increase in Coronary Blood Flow is Primary Mechanism to Meet Increased Oxygen Demand. There is a high rate of oxygen extraction at rest with minimal increased oxygen extraction with exercise.
What factors are responsible for decreases in myocardial oxygen supply?
•Hypotension (MAP < 60 mmHg), Decreased Oxygen Content (Anemia, Hypoxia), Decrease Coronary Blood Flow (Fixed Coronary Stenosis, Abnormal Vessel Reactivity)
Factors that Increase Myocardial Oxygen Demand
•Exercise, Fever, Acute Hypertension , Emotional Distress, Cardiac Disease, Enlarged left ventricle, Drugs
What are the clinical consequences of myocardial ischemia?
Angina, electrical abnormalities (ST depression, arrhythmias), mechanical abnormalities ( decreased systolic function, decreased diastolic function, mitral regurg), hemodynamic abnormalities (increased HR, increased BP)
Why can exercise be used to diagnose and risk stratify coronary artery disease?
At rest, need 90% stenosis to cause decrease in Coronary blood flow. With exercise, CBF decreases with stenosis of 70%. Myocardial demand (MVO2) is increased with exercise due to increased systolic BP and increased HR. Results are correlated with symptoms, ECG changes, echo and nuclear scan to look for perfusion defect
What is rate-pressure product and how does it relate to MVO2?
Rate pressure product is an index of myocardial oxygen consumption. Rate pressure product: max HR x max systolic BP. Max systolic BP: CO x systemic vascular resistance
What is the ischemic threshold and how can it be used to determine the severity of ischemia and responses to therapy?
RPP heart rate Threshold at which ST segment depression occurs on graph of rate pressure product vs workload. As workload increases, RPP increases. This is where ischemia occurs b/c oxygen supply is inadequate to meet myocardial oxygen demand. More severe ischemia occurs at a lower RPP
What is the usual effect of exercise training on the ischemic (angina) threshold?
Exercise training decreases % peak VO2 during submaximal exercise
What is cardiopulmonary exercise testing and how does it relate to cardiovascular performance during exercise?
Standard exercise evaluation with ECG, BP and HR OR expired gas analysis (measures VO2 and VCO2), ventilation, derivered parameters. Can be used to assess functional capacity and to determine prognosis in patients with severe systolic heart failurs
How does peak VO2 reflect differences in cardiovascular responses during exercise in patients with LV systolic dysfunction?
Reduced cardiac output in LV systolic dysfunction reduces VO2max
