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Doppler measurement of cardiac output across prosthetic mitral valves
H Dittmann1, W Voelker, K R Karsch
1Medizinische Klinik III, Eberhard-Karls-Universität Tübingen.
Insights
Pulsed Doppler echocardiography can measure cardiac output across mitral valve prostheses, but accuracy varies by valve type. Hancock and St. Jude prostheses provide reliable measurements, unlike Medtronic Hall prostheses, especially for higher flow rates.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Imaging
Background:
- Accurate cardiac output (CO) measurement is crucial for assessing cardiac function.
- Mitral valve prostheses are commonly implanted, necessitating reliable methods for CO assessment.
- Pulsed Doppler echocardiography offers a non-invasive approach to evaluate prosthetic valve function.
Purpose of the Study:
- To evaluate the accuracy of pulsed Doppler echocardiography for measuring cardiac output across different types of normally functioning mitral valve prostheses.
- To compare the performance of Doppler measurements with established methods like thermodilution and left ventricular outflow tract flow measurements.
- To determine if the prosthetic valve type influences the accuracy of Doppler-derived cardiac output.
Main Methods:
- Cardiac output was measured in 46 patients with mitral valve prostheses (St. Jude, Medtronic Hall, Hancock) using pulsed Doppler echocardiography across the prosthesis.
- Simultaneous cardiac output measurements were obtained via thermodilution or Doppler in the left ventricular outflow tract.
- Prosthetic valve area was calculated using the pressure half-time method; CO was derived from time-velocity integrals and valve area.
Main Results:
- Doppler transmitral flow measurements showed significant correlation with thermodilution (r=0.96) and LVOT Doppler (r=0.82).
- The mean percent error for Doppler transmitral flow was 10.8%, underestimating high cardiac output (>6.5 L/min) in 6/7 patients.
- Accuracy was higher for Hancock (SEE=0.473 L/min) and St. Jude (SEE=0.538 L/min) prostheses compared to Medtronic Hall (SEE=0.847 L/min).
Conclusions:
- Pulsed Doppler echocardiography can estimate cardiac output across normally functioning mitral valve prostheses.
- The accuracy of this method is dependent on the specific type of prosthetic valve due to varying flow dynamics.
- Reliable cardiac output measurements are feasible with Hancock and St. Jude prostheses, but limitations exist for Medtronic Hall prostheses, particularly at higher flow rates.
Abstract:
In 46 patients with a normal functioning mitral valve prosthesis (15 St. Jude, 19 Medtronic Hall, 12 Hancock) cardiac output was measured by pulsed Doppler echocardiography across the valve prosthesis. Simultaneously cardiac output was determined by thermodilution or pulsed Doppler echocardiography in the left ventricular outflow tract (2.8 l/min-9.5 l/min). The prosthetic valve area was calculated using the pressure half-time method. Cardiac output was calculated by multiplying time-velocity integrals with the mitral valve area. Cardiac output measurements across the mitral prosthesis correlated significantly with thermodilution (r = 0.96, SEE = 0.400 l/min) and pulsed Doppler echocardiography flow measurements in the left ventricular outflow tract (r = 0.82, SEE = 0.679 l/min). The mean percent error of the Doppler transmitral flow measurement was 10.8%. Doppler transmitral flow underestimated cardiac output valves of more than 6.5 l/min in 6 of 7 patients. Cardiac output measurements across Hancock (SEE = 0.473 l/min) and St. Jude prostheses (SEE = 0.538 l/min) were more accurate than across Medtronic Hall prostheses (SEE = 0.847 l/min). Cardiac output can be calculated by pulsed Doppler echocardiography across normal functioning mitral prostheses. Due to the different flow dynamics the accuracy of cardiac output measurement depends on the prosthetic valve type. Reliable measurements of cardiac output can be performed across Hancock and St. Jude prostheses only. This method is limited in volume flow measurements across Medtronic Hall prostheses.