Abstract
In order to evaluate hemodynamic predictors of myocardial oxygen consumption (MVO2), 27 normotensive men with angina pectoris were studied at rest and during a steady state at sympton-tolerated maximal exercise (STME). Myocardial blood flow (MBF) was measured by the nitrous oxide method using gas chromatography. MBF increased by 71% from a resting value of 57.4 +/- 10.2 to 98.3 +/- 15.6 ml/100 g LV/min (P less than 0.001) during STME while MVO2 increased by 81% from a resting value of 6.7 +/- 1.3 to 12.1 +/- 2.8 ml O2/100 g LV/min (P less than 0.001). MVO2 correlated well with heart rate (HR) (r = 0.79), with HR x blood pressure (BP) (r = 0.83), and, adding end-diastolic pressure and peak LV dp/dt as independent variables, slightly improved this correlation (r = .86). Including the ejection period (tension-time index) did not improve the correlation (r = 0.80). Thus, HR and HR x BP, both easily measured hemodynamic variables, are good predictors of MVO2 during exercise in normotensive patients with ischemic heart disease. Including variables reflecting the contractile state of the heart and ventricular volume may further improve the predictability.
Highlights
MEASURED PREDICTORS of myocardial blood flow (MBF) are necessary to evaluate objectively functional improvement in patients with ischemic heart disease
The other 26 patients had coronary arteriography: patients 2-4 had coronary arterial obstruction of greater than 70% of one coronary artery, patients 5-9 had greater than 70% obstruction of two coronary arteries, and patients 10-27 had greater than 70% obstruction of three coronary arteries
In 46 consecutive studies N20 measurements made by the gas chromatographic method were nearly the same as measurements made by the manometric method
Summary
MEASURED PREDICTORS of myocardial blood flow (MBF) are necessary to evaluate objectively functional improvement in patients with ischemic heart disease. Symptomatic improvement may occur as a result of a change in life style with little or no ability to increase MBF or to perform more external work. A medical regimen might result in an increase in the ability to perform external work with little or no ability to increase MBF. Direct measurement of exercising MBF requires use of an indicator and catheterization of the coronary sinus (CS) and is not applicable to a large patient population
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