Mechanism of pulmonary venous pressure and flow waves
Department of Applied Mechanics, Thermodynamics and Fluid Dynamics, The Norwegian University of Science and Technology, Trondheim.Heart and Vessels (Impact Factor: 2.07). 02/1999; 14(2):67-71. DOI: 10.1007/BF02481745
The pulmonary venous systolic flow wave has been attributed both to left heart phenomena, such as left atrial relaxation and descent of the mitral annulus, and to propagation of the pulmonary artery pressure pulse through the pulmonary bed from the right ventricle. In this study we hypothesized that all waves in the pulmonary veins originate in the left heart, and that the gross wave features observed in measurements can be explained simply by wave propagation and reflection. A mathematical model of the pulmonary vein was developed; the pulmonary vein was modeled as a lossless transmission line and the pulmonary bed by a three-element lumped parameter model accounting for viscous losses, compliance, and inertia. We assumed that all pulsations originate in the left atrium (LA), the pressure in the pulmonary bed being constant. The model was validated using pulmonary vein pressure and flow recorded 1 cm proximal to the junction of the vein with the left atrium during aortocoronary bypass surgery. For a pressure drop of 6 mmHg across the pulmonary bed, we found a transit time from the left atrium to the pulmonary bed of tau approximately 150ms, a compliance of the pulmonary bed of C approximately 0.4 ml/mmHg, and an inertance of the pulmonary bed of 1.1 mmHgs2/ml. The pulse wave velocity of the pulmonary vein was estimated to be c approximately 1m/s. Waves, however, travel both towards the left atrium and towards the pulmonary bed. Waves traveling towards the left atrium are attributed to the reflections caused by the mismatch of impedance of line (pulmonary vein) and load (pulmonary bed). Wave intensity analysis was used to identify a period in systole of net wave propagation towards the left atrium for both measurements and model. The linear separation technique was used to split the pressure into one component traveling from the left atrium to the pulmonary bed and a reflected component propagating from the pulmonary bed to the left atrium. The peak of the reflected pressure wave corresponded well with the positive peak in wave intensity in systole. We conclude that the gross features of the pressure and flow waves in the pulmonary vein can be explained in the following manner: the waves originate in the LA and travel towards the pulmonary bed, where reflections give rise to waves traveling back to the LA. Although the gross features of the measured pressure were captured well by the model predicted pressure, there was still some discrepancy between the two. Thus, other factors initiating or influencing waves traveling towards the LA cannot be excluded.
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ABSTRACT: Left ventricular diastolic dysfunction is associated with slowing of LV relaxation and a decrease in LV chamber compliance. This impairment of function leads to changes in filling velocities as measured by pulsed wave Doppler echocardiography in the pulmonary veins and across the mitral valve, and in intraventricular flow propagation velocity as measured by color M-mode Doppler. This paper explores some of the physiology of LV filling in a clinical context.Heart Failure Reviews 11/2000; 5(4):291-299. DOI:10.1023/A:1026531511226 · 3.79 Impact Factor
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ABSTRACT: A large number of patients suspected of having congestive heart failure have normal left ventricular systolic function and may, therefore, have primary diastolic heart failure. This diagnosis, however, should not be made unless there is also objective evidence of diastolic dysfunction, ie, signs of abnormal left ventricular relaxation and/or diastolic distensibility. The most useful noninvasive diagnostic approaches are the measurement of transmitral and pulmonary venous flow velocities by pulsed wave Doppler, and mitral annulus velocities by tissue Doppler echocardiography. In some patients, the assessment of intraventricular flow propagation by colour M-mode Doppler echocardiography provides additional information. Diastolic heart failure is most often due to coronary artery disease and/or hypertension; therefore, other noninvasive or invasive tests are needed to define the etiology of myocardial dysfunction. However, in the few patients who have constrictive pericarditis, the Doppler echocardiographic assessment of diastolic filling provides the most important clues to the etiology of the disease. Doppler echocardiographic assessment of left ventricular filling may also be used to obtain semiquantitative estimates of left ventricular diastolic pressure. Furthermore, left ventricular filling patterns, in particular, the deceleration time of early transmitral filling, are powerful predictors of patient prognosis. It is probably not cost effective to perform a comprehensive assessment of diastolic filling in every patient undergoing an echocardiographic examination. However, in selected patients, the assessment of diastolic filling provides information that is important for patient management.The Canadian journal of cardiology 12/2001; 17(11):1167-76. · 3.71 Impact Factor
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ABSTRACT: To determine whether the waveform in the left portal branch is reciprocal to the waveform found in the ductus venosus and umbilical vein due to difference in pulse direction compared to flow. Ten fetuses (gestational age, 18-33 weeks), six with intrauterine growth restriction, three with non-immune hydrops and one with sacrococcygeal teratoma, were examined using ultrasound imaging and pulsed Doppler. Techniques were adjusted to record simultaneously the waveform from neighboring sections of the veins, relate wave components to each other and determine degree of pulsatility. The corresponding vessel diameters were determined. ANOVA with t-test or Wilcoxon signed rank test was used to compare paired measurements. Pulsation in the left portal branch was noted in all fetuses. The pulsatility index was higher than in the umbilical vein (P = 0.005) and the diameter smaller (P = 0.001). In the left portal branch the atrial contraction wave appeared as a velocity peak while there was a nadir during ventricular systole. Simultaneous recordings showed that the waveform was reciprocal to that found in the ductus venosus and umbilical vein. In three cases an augmented pulsatility represented a pendulation of blood in the left portal branch with time-averaged velocity near zero. The velocity waveform recorded in the left portal vein is an inverse image of that in the ductus venosus, proving that pulse wave and blood flow run in the same direction in the left portal vein. Low compliance (i.e. small diameter) is probably a main reason for the high incidence of pulsation in this vein. Time-averaged velocity near zero recorded in three fetuses indicates that this area acts also as a watershed.Ultrasound in Obstetrics and Gynecology 05/2003; 21(4):359-64. DOI:10.1002/uog.78 · 3.85 Impact Factor
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