Ian G. McDonald

The shape and movements of the human left ventricle during systole. A study by cineangiography and by cineradiography of epicardial markers.

Abstract The shape of the left ventricular cavity and the movements of the mitral valve, aorta and coronary arteries were studied in cineangiograms obtained from normal subjects and patients with coronary arterial disease, mitral stenosis or atrial septal defect. Movements of the left ventricular epicardial surface were studied by postoperative cineradiography of radiopaque markers previously attached during closed mitral valvotomy. The pre-ejection and ejection phases of systole were identified from the simultaneously recorded phonocardiogram, apex cardiogram, indirect carotid pulse pressure tracing and electrocardiogram. The left ventricular epicardial surface contracted in an approximately symmetrical fashion with slight rotational movements about the long axis most marked at the beginning and end of systole, but contraction of the left ventricular cavity appeared less symmetrical because of the systolic increase in wall thickness, approximation of trabeculae and movements of the mitral valve. During pre-ejection, the left ventricular cavity narrowed anteroposteriorly, the descent of the base began and a slight anticlockwise rotation of the epicardial surface was accompanied by a slight thrust of the apex toward the chest wall. During ejection, narrowing of the left ventricular cavity and the descent of the base continued, and a slight clockwise rotation and retraction of the apex occurred in late systole. The symmetry of left ventricular contraction may be due to the similarity of contractility and afterload of individual myocardial fibers, and the slight rotational movements may be a result of sequential activation of the left ventricular myocardium from endocardial to epicardial surface.

Echocardiographic Demonstration of Abnormal Motion of the Interventricular Septum in Left Bundle Branch Block

A characteristic abnormality of motion of the interventricular septum was recorded by echocardiography in 17 of 18 patients with left bundle branch block. Early and abrupt contraction of the septum occurs during the pre-ejection period before the delayed commencement of contraction of the posterior wall of the left ventricle. This abnormality can be explained by asynchronous contraction of the left ventricle with early activation and contraction of the septum but delay in activation and contraction of the left ventricular free wall due to a block in the left bundle branch or its peripheral branches.

Doin’ the twist: new tools for an old concept of myocardial function

It has been known for some time that the heart rotates during the cardiac cycle in concert with radial and longitudinal motion. With advances in imaging technology, it has been appreciated that the apex and base of the heart rotate in different directions, resulting in a twisting or torsional motion. A new echocardiographic technique, “speckle tracking imaging”, permits accurate quantification of this motion. Torsion as well as the timing and magnitude of the rate of torsion (torsional velocity) may provide important new insights into cardiac physiology and disease.

A comparison of the relative value of noninvasive techniques—echocardiography, systolic time intervals, and apexcardiography—in the diagnosis of primary myocardial disease☆

Abstract In 25 patients with primary myocardial disease, left ventricular myocardial function was assessed by echocardiography, systolic time intervals (PEPLVET ratio), and apexcardiography (ALV ratio, systolic contour). Discrimination of patients with primary myocardial disease from a control group of normal subjects was good for both echocardiography and systolic time intervals; best discrimination was obtained by combining data from both of these methods while discrimination by the apexcardiogram or chest roentgenogram was not as clear. Fractional shortening, the echocardiographic index of myocardial shortening per unit length, and the PEPLVET ratio provide a quantitative assessment of myocardial function which reflects alteration of the myocardial foce-velocity relationship by myocardial disease. Data from the apexcardiogram are less quantitative, but add useful information on the presence of left ventricular hypertrophy or failure. Echocardiography is technically the most difficult of the three tests to perform, but failure to obtain useful information for technical or other reasons occurs most frequently for apexcardiography. All three techniques can be conveniently combined to provide an excellent noninvasive clinical assessment of myocardial function.

Contraction of the hypertrophied left ventricle in man studied by cineradiography of epicardial markers

Abstract The shape of the hypertrophied left ventricle during contraction and the shortening of epicardial dimensions were studied by postoperative cineradiographic studies of opaque markers placed at the time of aortic valve replacement in 10 patients with severe isolated aortic valve disease. The control group comprised 8 patients with a nonhypertrophied left ventricle who were treated successfully for pure mitral stenosis by closed mitral valvotomy. The extent of shortening during systole of epicardial chords across the left ventricular base and longitudinally from base to apex anteriorly and inferiorly were, respectively, 15.8, 14.3 and 16.1 percent (mean 15.4 percent) in the control group and 10.3, 7.1 and 5.4 percent (mean 7.6 percent) in patients with left ventricular hypertrophy. Thus, myocardial shortening was reduced generally in the patients with hypertrophy, but base to apex lengths were more affected and individual chords showed the most abnormal patterns of shortening during systole. In 2 patients with aortic regurgitation of recent onset, these abnormalities were less severe. Furthermore, the patterns of abnormal contraction remained unchanged in 4 patients studied serially over periods of 6 months to 2 years postoperatively despite electrocardiographic evidence of some resolution of left ventricular hypertrophy. It was therefore concluded that impaired myocardial function and an abnormal pattern of left ventricular contraction accompany severe left ventricular hypertrophy in aortic valve disease and improvement develops slowly or not at all after removal of the abnormal load.

Quantification of Mitral Regurgitation by Integrated Doppler Backscatter Power

OBJECTIVES We attempted to determine whether continuous wave Doppler backscatter power could be used to quantify mitral regurgitation. BACKGROUND The power of a Doppler backscatter signal is proportional to the number of scatterers insonated and, hence, to the moving volume of blood. The relative power of the continuous wave Doppler signals from mitral inflow and aortic outflow is therefore proportional to the relative volumes of blood in motion. METHODS Computer postprocessing was used to derive the relative power of the Doppler backscatter signal from the intensity of the pixels within the spectral display of anterograde aortic and mitral flow. The power ratio was used to calculate the regurgitant fraction in 20 patients (mean age 61.4 years) with mitral regurgitation. This Doppler regurgitant fraction was compared with that derived from angiographic left ventricular volume and thermodilution cardiac output. In addition, 12 normal control subjects were studied by the Doppler method. RESULTS Mean (+/- SD) catheterization regurgitant fraction was 0.50 +/- 0.26, and mean Doppler regurgitant fraction was 0.47 +/- 0.25 (r = 0.89). The limits of agreement between the two methods by Bland-Altman analysis were -0.21 + 0.27. In normal control subjects with an expected regurgitant fraction of close to zero, mean Doppler regurgitant fraction was 0.03 +/- 0.05. CONCLUSIONS Doppler backscatter power from mitral and aortic inflow provides a new and accurate method for quantifying mitral regurgitation.

Early rate of resolution of major pulmonary embolism. A study of angiographic and haemodynamic changes occurring in the first 24 to 48 hours.

Nine patients with major pulmonary embolism who were free of serious cardiopulmonary disease were studied by pulmonary angiocardiography with measurement ofpulmonary arterial pressure and cardiac output. The pulmonary angiogram was initially performed 20-0 hours (range 5 to 48 hours) after the first symptoms of the most recent episode of embolism and then repeated after 26A5 hours (range I7 to 48 hours) of heparin therapy. Six patients showed no change, 2 slight improvement, and I deterioration. The reductions in the average values of both the totalpulmonary resistance and the mean pulmonary arterial pressure were slight. It was concluded that little resolution of major pulmonary embolism occurs during the first 24 to 48 hours of heparin therapy.

Acute major pulmonary embolism as a cause of exaggerated respiratory blood pressure variation and pulsus paradoxus.

Respiratory variations in systemic blood pressure were analysed in I5 patients with major pulmonary embolism. Exaggeration of systolic blood pressure fluctuation was common and occasionally severe enough to produce obvious pulsus paradoxus. The cause was usually increased pulse pressure variation, presumably attributable to corresponding changes in left ventricular stroke volume. Of possible causes considered, the most likely were left ventricular compression due to acute right ventricular dilatation or depletion of pulmonary venous volume augmenting inspiratory pooling of blood.

The assessment of diagnostic imaging technologies: a policy perspective.

Diagnostic imaging technologies are essential in health care but have high costs and poorly defined benefits. Formulation and implementation of policy on their procurement and use is made difficult by the complexity of the diagnostic process, and the limitations of available data and assessment methodology. Informed policy decisions will need to be based on a synthesis of imperfect data from a variety of perspectives, and supplemented by effective dissemination and feedback of information. A list of attributes for consideration in the policy formulation process is presented.

Cardiac disease construction on the borderland

The diagnosis of possible heart disease in the well patient has undergone remarkable shifts over the past century. The traditional medical view places strong emphasis on the contribution of technological data to the diagnosis of disease. In the case of serious heart disease, cardiac diagnostic technologies can play a defining role but, more often in the clinical context, patients are assessed for heart disease which is minor. The question is whether disease is present at all. In this borderland between health and disease, the interpretation of technological data is inherently uncertain. The diagnosis then depends more heavily on the social utility of particular disease categories. Shifts in diagnostic categorisation are not therefore attributable solely to more extensive forms of cardiac imaging but are socially constructed in an interactive context which involves the technology, the medical profession and the wider social structures which exist at the time of diagnosis. Claims of technological certainty create a social space within which the medical profession generates disease categories. These shifting disease categories may serve the needs of patients but may also be influenced by those of other players.