Turbulent blood flow in the ascending aorta of humans with normal and diseased aortic valves

Range gated echo-Doppler velocity and turbulence mapping in patients with valvular aortic stenosis

Flow beyond a stenotic aortic valve (AS) is dynamically complex. Numerous hydraulic studies have demonstrated that at least four well-known major flow areas occur distal to a stenotic valve. These include a jet, an area alongside the jet (the parajet), an area of flow disturbance, and an area in which disturbed flow again becomes laminar downstream. Of these, only the flow disturbance area has markedly turbulent flow, although some turbulence can be at times detected in the area beside the jet. The purpose of this investigation was to test a technique of patient examination that might allow a range-gated pulsed Doppler to detect each of these known areas in the aorta (Ao) of valvular AS patients. A method for mapping flow in the lumen of the Ao root and ascending Ao is detailed. The transverse Ao arch was studied in the standard manner. With this mapping method, 14 patients with AS were studied. We were able to identify the jet in 13 of 14 as a high velocity, narrow-width signal in the Ao root. The parajet area was characterized by no detectable or low flow in 12 of 14, but two patients had late systolic flow disturbance in the parajet area. All patients had a strong flow disturbance detected; 3 of 14 were first detected in the Ao root and the remainder were first detected higher in the ascending Ao. The area of relaminarization was not addressed in this study. This investigation demonstrates that a proper interpretation of range-gated pulsed Doppler recordings from areas distal to AS requires knowledge of flow dynamics beyond an obstruction and a methodical range-gated pulsed Doppler examination technique.

Bioengineering aspects of heart valve replacement

Biomedical engineering inputs have been important in the design, development and testing of substitute heart valves as well as in the pre- and post-operative management of patients with cardiac valve disease. This paper is a review of heart valve replacement whose goal is the enhancement of future bioengineering contributions. We review the approach to the patient with valvular heart disease, and the sources of early and late postoperative pathology with emphasis on complications of the prostheses used. Major significant problem areas relate to the noninvasive evaluation of cardiovascular function (both before and after surgery), device design, hemodynamics, and the need for thromboresistant and durable materials.

Invasive and noninvasive phonocardiography and orifice-view aortography in the diagnosis of left ventricular outflow obstruction

Phonocardiography and orifice-view aortography for the detection of valvular and subvalvular stenosis is reviewed. Intracardiac phonocardiography may be useful in detecting a left ventricular outflow tract obstruction, and in distinguishing it from other conditions that can produce an apparent pressure gradient during cardiac catheterization. The frequency analysis of heart sounds on noninvasive phonocardiograms may be useful in identifying subclinical aortic stenosis. Orifice-view aortography can show the anatomy of deformed aortic valves and is useful in measuring the orifice area. In patients with heavily calcified valves, plain orifice-view roentgenograms may enable one to assess the valve area. Therefore the use of these techniques in selected patients may help establish a definitive diagnosis.

Intracardiac phonocardiography in experimental left ventricular cavity obliteration: potential clinical applicability for the distinction of obliterating left ventricle from hypertrophic obstructive cardiomyopathy

Intracardiac sound was measured in six dogs, four with left ventricular cavity obliteration induced by isoproterenol, and two with catheter entrapment. In left ventricular cavity obliteration, no murmur occurred within the left ventricle. Whenever a systolic murmur occurred, it was distal to the aortic valve. In entrapment, no murmur occurred within the left ventricle or distal to the aortic valve. Previous studies in patients with hypertrophic obstructive cardiomyopathy showed that the systolic murmur was of greatest intensity within the left ventricular outflow tract. Therefore, intracardiac phonocardiography may assist in differentiating these conditions which produce an intraventricular pressure gradient.

Effect of turbulent blood flow on systolic pressure contour in the ventricles and great vessels: significance related to anacrotic and bisferious pulses

The effect of turbulent blood flow on the contour of systolic pressure in the left and right ventricles and great vessels was investigated in 64 patients undergoing diagnostic cardiac catheterization. Intracardiac pressure and sound were recorded using a catheter-tip micromanometer. Measurements were made in normal subjects and patients with a variety of disorders including aortic stenosis, hypertrophic obstructive cardiomyopathy, coarctation of the aorta and atrial septal defect. Observations showed a consistent association of the intracardiac murmur, which is indicative of turbulence, with a transient reduction of the centrally recorded systolic pressure. The resultant abnormal systolic pressure contour can be explained on the basis of fluid dynamic considerations related to turbulence.

Non-invasive diagnosis and assessment of aortic valve disease and evaluation of aortic prosthesis function using echo pulsed Doppler velocimetry

Non-invasive recording of aortic blood flow velocity patterns in the ascending aorta and in the arch of the aorta was performed in 12 normal subjects, 38 patients with confirmed aortic valve disease, and 13 patients with aortic prostheses using pulse echo Doppler velocity recordings. In normal subjects, the velocity recordings correlated well with those obtained by other authors using invasive procedures. In patients with aortic valve disease, specific abnormalities of the velocity curves were found to correlate well both with the type of lesion (stenosis or regurgitation) and its severity on a three-point scale. Both sensitivity and specificity were found to range between 80 and 94 per cent. A less accurate grading of severity was obtained from patients with aortic regurgitation by the detection of turbulence in the left ventricular outflow tract than from the appearance of the aortic velocity curves. In the studies of patients with aortic prostheses, anomalies of the velocity pattern could be found in the ascending aorta in 53 per cent but no abnormalities of timing was found. In spite of some technical limitations, pulse echo Doppler velocity recordings provide a new non-invasive, reliable, and reproducible approach in assessing the presence and severity of aortic lesions and demonstrating flow abnormalities produced by prostheses.

Mid-systolic closure of the aortic valve in hypertrophic obstructive cardiomyopathy: a pressure-related phenomenon induced by turbulent blood flow

The purpose of this study was to determine whether mid-systolic closure and opening of the aortic valve in patients with hypertrophic obstructive cardiomyopathy (HOCM) may reflect dynamic changes of pressure induced by turbulent blood flow in the aorta and left ventricular outflow tract. Five patients with HOCM who had echocardiographic evidence of mid-systolic closure of the aortic valve and two patients with HOCM who did not have transient mid-systolic closure of the aortic valve were studied. In patients in whom mid-systolic closure was present, a transient mid-systolic drop of pressure was present in the left ventricular outflow tract, distal to the dynamic intraventricular obstruction, 17 +/- 3 mm Hg (mean +/- SEM) and in the root of the aorta, 16 +/- 4 mm Hg. In these patients the mid-systolic drop of pressure was consistently associated with a high-intensity intracardiac murmur indicative of turbulence. In the two patients in whom mid-systolic closure of the aortic valve was absent, the transient mid-systolic drop of pressure during systole was minimal (average, 3 mm Hg). The transient mid-systolic drop of pressure distal to the intraventricular obstruction can be explained on the basis of decreased pressure energy of the blood due to turbulence. Since total energy is conserved, increased kinetic energy due to turbulence occurs at the expense of a loss in pressure energy. The transient mid-systolic reduction of pressure in the turbulent zone during systole may cause a pressure differential across the open valvular leaflets resulting in a transient closure of the aortic valve.

Intracardiac sound as a diagnostic adjunct in subaortic stenosis

The purpose of this investigation is to demonstrate the potential diagnostic value of intracardiac sound recordings in patients with subaortic stenosis. Intracardiac pressure and sound were measured in 10 patients with various types of subaortic obstructions using a catheter-tip micromanometer. Seven patients had idiopathic hypertrophic subaortic stenosis (IHSS), 2 had a subvalvular membrane, and 1 had a subvalvular tunnel. Within the left ventricular cavity, at the site of maximal systolic left ventricular pressure, either there was no systolic murmur, or the murmur was of low intensity. However, within the outflow tract of the left ventricle, distal to the site of intraventricular obstruction, a prominent systolic murmur was detected in all patients. This murmur was of higher intensity than the one measured distal to the aortic valve. In one patient, in whom no subvalvular obstruction was present, but in whom entrapment of the tip of the catheter occurred, no murmur was detected in the left ventricle even though a subvalvular pressure gradient was observed. Therefore it appears that a systolic murmur recorded with maximal intensity in the outflow tract of the left ventricle may be of substantial help in distinguishing between an artifactual intraventricular pressure gradient, and one that results from intraventricular obstruction.

Aortic origin of innocent murmurs

Intraarterial sound was measured just distal to the aortic and pulmonary valves of 10 subjects with no apparent valve disease. Six patients had no audible murmur; four had grade 1 to 2 innocent murmurs. At rest, during normal sinus rhythm, the intensity of intraarterial sound was greater above the aortic than above the pulmonary valve (0.41+/-0.14 versus 0.02+/-0.01 ergs/sec per cm2 [mean+/-standard error of the mean]) (P less than 0.02). In all patients with an audible murmur, the murmur was of greater amplitude within the aorta than within the pulmonary artery. The two patients with a grade 1 murmur had a murmur near the aortic valve and no murmur near the pulmonary valve. To examine the effects of increased flow, the six patients with inaudible murmurs were studied during the first beat immediately after a premature ventricular contraction. The intensity of intraarterial sound after premature contractions in these six patients was 1.41+/-0.38 ergs/sec per cm2 above the aortic valve and 0.10+/-0.04 above the pulmonary valve (P less than 0.01). The intensity of murmurs in the aorta during postextrasystolic beats was in the range that occurs with grade 1 to 2 murmurs, whereas murmurs within the pulmonary artery were in the range of inaudible murmurs. Comparable observations were made in dogs in which instantaneous flow was also measured. These observations suggest that innocent murmurs are produced at the aortic rather than the pulmonary valve, possibly because of the greater compliance of the pulmonary artery, which may have a damping effect upon turbulence.

Continuing disease process of calcific aortic stenosis. Role of microthrombi and turbulent flow

Microthrombi with evidence of organization were observed in 10 of 19 calcified and stenotic aortic valves (53 percent). The organization that results from such thrombi may contribute to the deformity of the valve. Repetitive deposits of microthrombi, followed by organization and calcification, would explain the continuous process of stenosis in previously deformed aortic valves. The formation of such thrombi may be initiated by turbulent flow and other fluid dynamic factors.