Fiber orientation across the left ventricular myocardial wall has been studied. Specimens were obtained from 18 dog hearts rapidly fixed in situ in systole, in diastole, and in dilated diastole. Fiber orientation was determined across the free wall at eight sites from a T-shaped specimen by measurements with light microscopy in serial paraffin sections. Results indicate: (1) The wall has a well-ordered distribution of fiber angles varying from about 60° (from the circumferential direction) at the inner surface to about -60° on the outer surface. The greatest change in angle with respect to wall thickness occurs at the two surfaces (endocardial and epicardial). (2) Fiber angles did not change significantly during the transition from diastole to systole, despite a 28% increase in wall thickness (except in the papillary muscle root region). (3) The proportion of fibers lying in the sector of fiber angles oriented circumferentially (0±22.5°) to those oriented longitudinally (67.5 to 90° and -67.5 to -90°) is approximately 10:1. This ratio increases toward the base and diminishes toward the apex of the left ventricle. (4) All fiber angles in the lateral wall of hearts in systole increased through the wall by approximately 7° near the base and 19° near the apex relative to their counterparts in diastole, indicating bending or torsion of the left ventricle during contraction.

Fiber Orientation in the Canine Left Ventricle during Diastole and Systole

Atherosclerosis is the most common cause of chronic arterial occlusive disease of the lower extremities. The arterial narrowing or obstruction that occurs as a result of the atherosclerotic process reduces blood flow to the lower limb during exercise or at rest. A spectrum of symptoms results, the severity of which depends on the extent of the involvement and the available collateral circulation. Thus, symptoms may range from intermittent claudication to pain at rest. Intermittent claudication denotes pain that develops in the affected limb with exercise and is relieved with rest. This pain usually occurs distal to the arterial narrowing or obstruction. Since the superficial femoral and popliteal arteries are the vessels most commonly affected by the atherosclerotic process, the pain of intermittent claudication is most often localized to the calf. The distal aorta and its bifurcation into the two iliac arteries are the next most frequent sites of involvement. Narrowing of these arteries may produce pain in the buttocks or the thighs as well as the legs.

Epidemiological studies indicate that up to 5% of men and 2.5% of women 60 years of age or older have symptoms of intermittent claudication.1 2 The prevalence is at least threefold higher when sensitive noninvasive tests are used to make the diagnosis of arterial insufficiency in asymptomatic and symptomatic individuals.3 The symptoms of chronic arterial insufficiency of the lower extremities progress rather slowly over time. Thus, after 5 to 10 years, more than 70% of patients report either no change or improvement in their symptoms, while 20% to 30% have progressive symptoms and require intervention, and less than 10% need amputation.4 5 Despite the relatively benign prognosis for the affected limb, however, symptoms of intermittent claudication should be viewed as a sign of systemic atherosclerosis. This explains why, compared with …

Diagnosis and Treatment of Chronic Arterial Insufficiency of the Lower Extremities: A Critical Review

Doppler ultrasound has now developed to the point where the rate of flow of blood in a given vessel can be measured with appropriate instrumentation. The theoretical basis of Doppler flow measurement is reviewed in this paper, with particular emphasis on the potential and actual sources of error. Three distinct approaches are identified, and the strengths and weaknesses of each discussed. The separate errors involved in estimating the vessel cross-sectional area, the angle of approach, and the Doppler shift are analyzed, together with the question of the uniformity of scattering from the blood. In vivo and in vitro tests of the accuracy obtained using a number of Doppler flow measuring instruments are then reviewed. It is concluded that the Doppler methods are capable of good absolute accuracy when suitably designed equipment is used in appropriate situations, with systematic errors of 6% of less. There are, however, considerable random errors, attributable primarily to errors in measuring the cross-sectional area and the angle of approach. Repeating the measurement of flow several times and averaging the results can reduce these random errors to an acceptable level.

Measurement of blood flow by ultrasound: accuracy and sources of error.

We used a pulsed Doppler technique to examine the flow velocity pattern in the right ventricular outflow tract in 33 adults. In the patients with normal pulmonary artery pressure (mean pressure less than 20 mm Hg, 16 patients), ejection flow reached a peak level at midsystole (137 +/- 24 msec, mean +/- SD), producing a domelike contour of the flow velocity pattern during systole. In contrast, the flow velocity pattern in patients with pulmonary hypertension (mean pressure greater than or equal to 20 mm Hg, 17 patients) was demonstrated to accelerate rapidly and to reach a peak level sooner (97 +/- 20 msec, p less than .01); in 10 of the pulmonary hypertensive patients a secondary slower rise in flow velocity was observed during a deceleration, resulting in the midsystolic notching. The time to peak flow (acceleration time, AcT) and right ventricular ejection time (RVET) were measured from the flow velocity pattern. Either AcT or AcT/RVET decreased with increase in mean pulmonary artery pressure, and a very high correlation (r = -.90) was found between AcT/RVET and log10 (mean pulmonary artery pressure). The use of this technique permitted the noninvasive estimation of the pulmonary artery pressure.

Noninvasive evaluation of pulmonary hypertension by a pulsed Doppler technique.

We describe initial results which show “live” ultrasound echography data visualized within a pregnant human subject. The visualization is achieved by using a small video camera mounted in front of a conventional head-mounted display worn by an observer. The camera’s video images are composite with computer-generated ones that contain one or more 2D ultrasound images properly transformed to the observer’s current viewing position. As the observer walks around the subject. the ultrasound images appear stationary in 3-space within the subject. This kind of enhancement of the observer’s vision may have many other applications, e.g., image guided surgical procedures and on location 3D interactive architecture preview. CR Categories: 1.3.7 [Three-Dimensional Graphics and Realism] Virtual Reality, 1,3.I [Hardware architecture]: Three-dimensional displays, 1.3.6 [Methodology and Techniques]: Interaction techniques, J.3 ILife and Medical Sciences]: Medical information systems. Additional

Merging virtual objects with the real world: seeing ultrasound imagery within the patient

During the early stages of ventricular systole, myocardial tension develops very rapidly, ventricular pressure rises steeply to exceed arterial pressure, and momentum is then rapidly imparted to the blood flowing out of the ventricles. The acceleration of blood out of the ventricles is an expression of the force being applied by the contracting myocardium, and the peak flow velocity can be regarded as the product of the net force applied over the time from the onset of ejection to the peak. The product of force and time is designated by a well-established physical term: impulse (I=Ft). Thus, "initial ventricular impulse" appears to be an appropriately descriptive term for the dynamic properties of ventricular ejection. Direct and continuous records of acceleration, the outflow rate of blood, and the rates of change of ventricular and arterial pressure demonstrate that ejection of blood from both ventricles (particularly the left) is more like striking a piston with a mallet than like squeezing blood out o...

Initial ventricular impulse. a potential key to cardiac evaluation.

Ultrasonic B-mode displays are produced by a new diagnostic scanner that yields dynamic Doppler information from blood flow in addition to both static and dynamic echo information from stationary and more slowly moving tissues. The effect is produced by combining the flow imaging capability of a multigate pulse-Doppler flow detector with a fast rotational pulse-echo B-mode scanner. The duplex system was designed for performing ultrasonic echo-Doppler arteriography where the location and geometry of the interface between occlusive atherosclerotic tissue and blood is of prime concern. Initial results on normal arteries in vivo are illustrated. Spatial alignment of echo and Doppler images is obtained by using the same transducer and scanning mechanism for both. However, clinical trials on patients with verified occlusive arterial disease indicated a two-transducer system would be more desirable. It is concluded that superposition of images of both tissue and blood decreases the uncertainties inherent in the display of either image alone.

Ultrasonic Duplex Echo-Doppler Scanner

A range-gated pulsed Doppler flowmeter has recently been developed that measures the average velocity of blood flow within a small tear-drop shaped (4 mm by 2 mm) sample volume. Unlike the continuous wave Doppler, the distance from the transducer face to the sampling site can be continuously varied by a range adjustment knob. Twenty patients with cardiac murmurs were evaluated in a noninvasive laboratory by brief cardiac physical examination, abbreviated phonocardiogram, complete echocardiogram, and localization of the murmurs by Doppler echocardiography. The localization depends on the detection of turbulent flow or jets at the sampling site. The murmurs included the diastolic rumble of mitral stenosis, mitral regurgitation, the murmur of left ventricular outflow tract obstruction, aortic stenosis, aortic insufficiency, diastolic rumble of tricuspid stenosis, augmented right ventricular filling sound in atrial septal defects, pulmonic stenosis, pulmonic insufficiency, and high velocity flow through the obstruction in ccarctation of the aorta.

Doppler echocardiography. The localization of cardiac murmurs.

https://www.amjmed.com/article/0002-9343(77)90119-X/pdf

Pulsed doppler echocardiography: Principles and applications

A pulsed ultransonic flowmeter has been developed specifically for the simultaneous measurement of blood flow through various major blood vessels in the intact unanesthetized animal. The flow section is a small (1-3 cm) lucite cylinder which is clamped about the blood vessel. Piezoelectric crystals are mounted on the flow section so that bursts of 3-mc sound may be transmitted alternately upstream and downstream. The flowmeter develops a voltage which is proportional to the difference in the upstream and downstream transit times of the sound. This voltage is recorded continuously and calibrated in terms of flow. Under optimal conditions, the output voltage is a linear and accurate representation of volume flow within ±5 per cent, independent of the velocity profile. The flowmeter responds to a step variation in flow within 0.01 second. The maximum noise and baseline drift is equivalent to a flow velocity variation of less than 1 cm/second measured over a 4-hour period.

Donald W. Baker

Papers

Initial ventricular impulse. a potential key to cardiac evaluation.

Ultrasonic Duplex Echo-Doppler Scanner

Doppler echocardiography. The localization of cardiac murmurs.

Pulsed doppler echocardiography: Principles and applications

A Pulsed Ultrasonic Flowmeter