Study objectives: To compare the oxygen pulse curve (O2P-C) as measured during cardiopulmonary exercise testing (CPET) with left ventricular (LV) ejection fraction (LVEF) rest-exercise response as measured by multigated equilibrium 99mTc radionuclide cineangiography (MUGA) in patients with different degrees of ischemic heart disease (IHD).
Patients: Forty-six patients (39 men and 7 women; mean ± 1 SD age, 59.2 ± 11 years) with IHD, with no hypertrophic, valvular, or pericardial disease.
Methods: A supine bicycle ergometer with increments of 25 W every 2 min was used for MUGA, and an electronically braked cycle ergometer was used for upright symptoms-limited CPET. Exercise was increased by 10 to 20 W/min until the target heart rate (HR) was reached (similar peak HR for both studies).
Measurements and results: The O2P-C was scored on a 10-point scale as follows: type A, normal curve (10 points); type B, normal-shaped curve with low values (8 points); type C, low and flat curve (5 points); type D, descending curve (3 points). Findings for the MUGA study were classified into four groups by the degree of ischemic response: group 1 (control), normal diastolic function (n = 10), LVEF > 55%, LVEF during exercise minus LVEF at rest [ΔLVEF] ≥ 5%; group 2, mild ischemia (n = 10), LVEF > 55%, < 0 ΔLVEF < 5%, diastolic dysfunction at exercise (prominent “A” waves); group 3, LV dysfunction (n = 9), LVEF ≤ 35% at rest; and group 4, significant ischemia (n = 17), LVEF > 55%, ΔLVEF < 0, diastolic dysfunction. A highly significant relationship between the O2P-C score and the MUGA grouping was observed by Fisher’s Exact Test and Pearson’s linear regression line (p < 0.001; R = − 0.89).
Conclusions: Exercise-responded O2P-C might serve as a good noninvasive, physiologically based, parameter to distinguish between IHD patients with normal and impaired LV function.