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Noninvasive cardiac output monitoring during exercise stress test
M Nanna1, D T Kawanishi, C R McKay
1Department of Medicine, LAC-USC Medical Center, University of Southern California School of Medicine 90033.
Insights
Continuous wave Doppler accurately estimates cardiac output during exercise in patients with coronary artery disease. This non-invasive method shows reduced cardiac output increase in patients compared to healthy controls.
Area of Science:
- Cardiology
- Medical Technology
Background:
- Assessing cardiac output during exercise is crucial for understanding cardiovascular function.
- Traditional methods for measuring cardiac output can be invasive or complex.
Purpose of the Study:
- To evaluate the accuracy and utility of a computerized continuous wave Doppler instrument for monitoring cardiac output during symptom-limited supine bicycle exercise.
- To compare exercise capacity and cardiac output response between patients with coronary artery disease and healthy controls.
Main Methods:
- Continuous wave Doppler was used to measure cardiac output in 41 individuals during exercise.
- Participants included 21 patients with coronary artery disease (group 1) and 12 age-matched asymptomatic controls (group 2).
- Doppler-derived cardiac output was validated against thermodilution in a subset of patients.
Main Results:
- The Doppler technique showed good correlation with thermodilution for cardiac output measurement (r=0.86).
- Patients with coronary artery disease exhibited a significantly lower increase in cardiac output (34%) compared to controls (103%) during exercise.
- Coronary artery disease patients also had shorter exercise duration and lower double product.
Conclusions:
- Continuous wave Doppler provides reasonably accurate cardiac output estimates at rest and during moderate exercise.
- This non-invasive Doppler technique may be a valuable tool for assessing cardiovascular response during exercise in selected clinical scenarios.
- The study highlights impaired cardiac output augmentation during exercise in coronary artery disease patients.
Abstract:
A computerized continuous wave Doppler instrument was used to monitor changes in cardiac output during symptom limited supine bicycle exercise in 41 individuals. Eight (19%) had technically unsatisfactory Doppler signals. Of the remaining 33 patients, 21 had clinical and 18 had angiographic evidence of coronary artery disease (group 1) and 12 age-matched asymptomatic subjects served as controls (group 2). In eight group 1 patients, cardiac output determined simultaneously by Doppler and thermodilution technique correlated well at rest and peak exercise (Y = 1.71x + 0.69, SEE = 0.57, r = 0.86, P less than 0.001). During exercise, group 1 patients increased their cardiac output from 5.2 +/- 1 to 6.9 +/- 1.4 (mean +/- SD), group 2 subjects increased their cardiac output from 5.5 +/- 1.3 to 10.9 +/- 2. Group 1 patients, when compared to group 2 control subjects, had a lesser increase in cardiac output (34% versus 103%, P less than 0.05), a shorter duration of exercise (6.1 versus 9.7 mins, P less than 0.05) and a lower double product (172 +/- 18 versus 211 +/- 27, P less than 0.05). This new Doppler technique provides reasonably accurate estimates of cardiac output at rest and on moderate exercise in selected patients. In selected clinical situations, it may be a valuable addition to other measurements that are usually determined during exercise.