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[Noninvasive determination of stroke volume with impulse Doppler echocardiography: comparison with the Fick method]
Insights
Pulsed Doppler echocardiography accurately determines cardiac output by measuring blood flow velocity in the aorta. This non-invasive method shows strong correlation with the Fick principle, offering a reliable alternative for cardiac output assessment.
Area of Science:
- Cardiovascular Physiology
- Diagnostic Ultrasound
- Medical Instrumentation
Background:
- Accurate cardiac output measurement is crucial for managing cardiovascular diseases.
- The Fick principle is a standard but invasive method for determining cardiac output.
- Non-invasive alternatives are sought to improve patient safety and ease of use.
Purpose of the Study:
- To evaluate the accuracy of a novel pulsed Doppler echocardiographic system for cardiac output determination.
- To compare Doppler-derived cardiac output (CO-D) with measurements obtained via the Fick principle (CO-F).
Main Methods:
- Pulsed Doppler echocardiography was used in 14 patients with various cardiac conditions.
- Cardiac output was calculated by integrating blood flow velocity in the ascending aorta and multiplying by aortic cross-sectional area and heart rate.
- Simultaneous measurements using the Fick principle served as the reference standard.
Main Results:
- A statistically significant linear correlation was found between CO-D and CO-F (r = 0.85).
- The equation for the correlation was CO-D = 0.92 CO-F + 0.48, with mean values of 3.89 L/min (Doppler) and 3.68 L/min (Fick).
- Correlation improved in patients with sinus rhythm (r = 0.93).
Conclusions:
- Pulsed Doppler echocardiography provides an accurate and reliable method for determining cardiac output.
- This non-invasive technique is suitable for patients without aortic stenosis.
- The developed Doppler instrument demonstrates clinical utility in cardiovascular assessment.
Abstract:
Pulsed Doppler echocardiographic studies were performed in 14 patients (eleven with mitral valve disease, two with coronary artery disease, one with aortic and mitral valve replacement) for determination of cardiac output and the results compared with those obtained from simultaneous measurements carried out according to the Fick principle. Determination of cardiac output and stroke volume was achieved with a pulsed Doppler instrument specifically designed in our laboratory (repetition frequency 10 kHz, maximal penetrance 7.7 cm, ultrasonic beam diameter 3 cm at a distance of 5 cm from the transducer). Doppler measurements of the instantaneous blood flow velocity in the ascending aorta were obtained with the transducer in a suprasternal position. Through integration of the mean spatial velocity over an entire cardiac cycle, the distance traversed by the blood during one heart beat was obtained and then multiplied by the echocardiographically-determined cross-section area of the aorta and the heart rate to yield the cardiac output. There was a statistically-significant linear correlation between the cardiac output determined by Doppler (CO-D) and Fick (CO-F): CO-D = 0.92 CO-F X 0.48, r = 0.85, n = 14. The mean values for the two methods were 3.89 and 3.68 1/min, respectively. The correlation between the two methods improved if only those patients with sinus rhythm were taken into consideration (CO-D = 1.05 CO-F - 0.21, r = 0.93, n = 11). The results show that the pulsed Doppler method used enables accurate determination of cardiac output. The method can be carried out in all patients without aortic stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)