Showing papers on "Cardiac cycle published in 1975"

Nontraumatic determination of left ventricular ejection fraction by radionuclide angiocardiography.

Abstract: Previous reports have suggested that left ventricular ejection fraction can be assessed by recording the passage of peripherally administered radioactive bolus through the heart. The accuracy and validity of this technique were examined in 20 patients undergoing diagnostic cardiac catheterization. 99m-Tc-human serum albumin was injected via a central venous catheter into the superior vena cava and precordial activity recorded with a gamma scintillation camera interfaced to a small digital computer. A computer program was designed to generate time-activity curves from the left ventricular blood pool and to calculate left ventricular ejection fractions from the cyclic fluctuations of the left ventricular time-activity curve which correspond to left ventricular volume changes during each cardiac cycle. The results correlated well with those obtained by biplane cineangiocardiography (r equals 0.94) and indicated that the technique should allow accurate and reproducible determination of left ventricular ejection fraction. The findings, however, demonstrated that the time-activity curve must be generated from a region-of-interest which fits the left ventricular blood pool precisely and must be corrected for contributions arising from noncardiac background structures. This nontraumatic and potentially noninvasive technique appears particularly useful for serial evaluation of the acutely ill patient and for follow-up studies in nonhospitalized patients.

Measurement of right and left ventricular systolic time intervals by echocardiography.

Abstract: One of the noninvasive methods of evaluating left ventricular performance is the measurement of left ventricular systolic time intervals (LVSTI). However, noninvasive measurement of right ventricular systole by this technique has been unreliable because of the inability to accurately time the onset of right ventricular ejection. Excellent correlation of LVSTI measured from the carotid pulse and those determined from the echocardiogram was demonstrated in 15 patients. STI of the right ventricle (RVSTI) were measured in a similar fashion from the pulmonary valve echo in 11 normal children. Right ventricular ejection time (RVET) was longer than left ventricular injection time (LVET). Right ventricular pre-ejection period and RPEP was shorter than left ventricular pre-ejection period (LPEP). In 15 children with transposition of the great arteries (TGA) the situation was reversed. RVET was shortened and RPEP was prolonged as the right ventricle contracted against systemic resistance; whereas, the LVET lengthened and LPEP shortened with ejection into a low pressure pulmonary circuit. Our studies in a total of 41 patients indicate the accurate, noninvasive measurement of right, as well as left, ventricular STI can be obtained with the use of echocardiography.

Observations on patients with primary ventricular fibrillation complicating acute myocardial infarction.

Abstract: In order to evaluate the events preceding primary ventricular fibrillation (PVF), continuous tape recording was performed in 262 patients consecutively admitted to the hospital within six hours of infarction in whom antiarrhythmic therapy was withheld. Warning arrhythmias (defined as ventricular ectopic beats occurring with a frequency of more than five beats per minute, in runs, falling in the vulnerable phase of the cardiac cycle or being multiformed) were registered in an equal percentage in patients who did or did not develop PVF. Immediately prior to PVF seven patients showed sinus tachycardia, 10 a sinus rate ranging from 60 to 100 beats per minute and two bradycardia due to complete atrioventricular block. The ventricular ectopic beat initiating PVF had a late coupling interval (QR'/QT larger than or equal to 0.85) in 11 patients and a left bundle branch block configuration as frequent as a right bundle branch block. Conclusions: 1) Warning arrhythmias are not considered good criteria for instituti...

Dynamic determinants of letf ventricular diastolic pressure-volume relations in man.

Abstract: Left ventricular (LV) diastolic pressure (P), volume (V), and rate of change of volume (dV/dt) were determined at 16.7 msec intervals in 17 patients (simultaneous micromanometer and single plane volume angiography). Four patients had mitral stenosis with atrial fibrillation and 13 patients (three normal, two congestive cardiomyophathy, three LV hypertrophy, and five coronary artery disease) were in normal sinus rhythm. Maximum early diastolic filling rates (max dV/dt) in the normal and cardiomyopathy patients were similar and ranged from 269 to 370 cc/m-2/sec; in coronary artery disease and LV hypertrophy, max dV/dt ranged from 197 to 290 cc/m-2/sec and 213 to 255 cc/m-2/sec respectively; in mitral stenosis, max dV/dt ranged from 215 to 270 cc/m-2 sec. The peak filling rate during atrial systole ranged form 60 to 240 cc/m-2/sec in the 13 patients with sinus rhythm. The instantaneous diastolic P-V data were fit by an exponential equation (P = be-kV) and the P-V relation throughout diastole was represented by the best fit line. The rate constant (k) in the equation was highest in the patient with IHSS and lowest in those with large dilated hearts. In mitral stenosis with atrial fibrillation the fit of the equation to the P-V data appeared better than in the patients with normal sinus rhythm. Peak ventricular filling rate during atrial systole varied directly with LV volume distensibility at the onset of atrial systole (r = 0.64). Data suggest that dynamic mechanical properties of the LV influence the diastolic P-V relations and that pressure "deviations" (deltaP) from the best fit line during atrial systole may be related to viscous drag. In a given ventricle the velocity dependence of deltaP appears to be modified by the volume distensibility of the ventricle. Variable rates of filling may preclude the assumption of an exponential relation between P and V throughout diastole and therefore may limit estimates of diastolic distensibility or compliance which rely on such an assumption.

Measurement of peak rates of left ventricular wall movement in man. Comparison of echocardiography with angiography.

Abstract: Estimates of peak systolic and diastolic rates of left ventricular wall movement were made in 23 patients by echocardiography and angiocardiography. Echocardiographic measurements were calculated as the rate of change of the transverse left ventricular dimension, derived continuously throughout the cardiac cycle. These were compared with similar plots of transverse left ventricular diameter, in the same patients, derived from digitized cineangiograms taken within 10 minutes of echocardiograms. The results indicate close correlation between the two methods, and suggest that either can be used to measure peak rates of left ventricular wall movements in patients with heart disease.

Uniformity of transmural perfusion in anesthetized dogs with maximally dilated coronary circulations.

Abstract: In 14 beating hearts, coronary blood flow was measured electromagnetically in either the left circumflex or the left anterior descending coronary artery, and regional myocardial blood flow was computed from tissue uptake of 7-10^ radioactive microspheres. Metabolic dilation of the coronary circulation was induced by occluding the coronary artery for 10 or 90 seconds, and pharmacologic dilation was induced by infusing papaverine into the artery. In seven dogs, differently labeled microspheres were administered (1) before coronary artery occlusion, (2) at the peak reactive hyperemic response to a 10-second coronary artery occlusion, and (3) early in the rising phase of the hyperemic response following a 90-second coronary artery occlusion. Myocardial blood flow was distributed uniformly across the left ventricular free wall before occlusion and at peak hyperemia after the 10-second occlusion, but early in the hyperemic response to the 90-second occlusion coronary blood flow preferentially perfused subepicardial tissue. In another group of seven dogs, microspheres were administered (1) before coronary artery occlusion, (2) at the peak hyperemic flow after a 90-second occlusion, and (3) at the peak flow during local intracoronary infusion of papaverine. The left ventricular free wall was uniformly perfused under each condition. However, in 12 vented, fibrillating hearts with coronary circulations dilated maximally by perfusion with venous blood containing either papaverine or adenosine, left ventricular blood flow was preferentially directed to the subendocardium (endocardial-epicardial ratio averaged 1.37 ± 0.08 [SE]). We conclude that the coronary circulation of the normally functioning canine heart can dilate maximally without causing relative subendocardial ischemia because of a gradient of vascularity that favors the subendocardium and compensates for systolic flow limitation in that region. • Coronary blood flow is uniformly distributed across the left ventricular free wall of the normally perfused heart of the anesthetized dog (1-3), in spite of the observation that blood entering the left coronary circulation during the systolic phase of the cardiac cycle perfuses primarily the epicardial tissue (4). This nonuniform distribution of systolic flow is believed to be due to the transmural gradient of pressure generated by ventricular contraction (4). It would appear, therefore, that to perfuse the ventricular wall uniformly, diastolic coronary blood flow should be preferentially directed to the subendocardial area. Moir and DeBra (5) have postulated that autoregulatory adjustments in vascular tone are responsible for maintaining adequate subendocardial perfusion. If such an autoregulation is the only mechanism involved in adjusting blood flow to regional requirements, dilation of the coronary vasculature would result in

Echographic assessment of atrial transport, mitral movement, and ventricular performance following electroversion of supraventricular arrhythmias.

Abstract: Controversy attends the extent and temporal sequence of improvements in hemodynamic function resulting from the return of atrial contraction following cardioversion of supraventricular arrhythmias. Thus, mitral, left atrial (LA) and left ventricular (LV) echograms were obtained before and one hour after conversion of supraventricular arrhythmias to normal sinus rhythm by direct current countershock in patients with chronic coronary disease or cardiomyopathies without valvular dysfunction. The duration of the rhythm disturbance varied from one day to five years in 22 patients and was indeterminate in 13. Atrial systole immediately produced prominent mitral "A" waves with anterior valve excursion of 7.5 mm (range 3 to 12) in 33 of the 35 patients (94%). The two patients with atrial electromechanical dissociation reverted to atrial fibrillation within one week. Cardioversion caused a decline in LA diameter (3.5 to 3.2 cm, P less than .001) and a rise in LV end-diastolic dimension (5.2 to 5.5 cm, P less than .001) while LV end-systolic dimension was unchanged (4.2 cm). Thereby stroke volume rose. Heart rate fell an average of 16 beats/min. Depressed cardiac output was improved + 0.84 L/min/m-2. Thus, in the majority of patients with acute or chronic supraventricular arrhythmias without mitral valve disease, cardioversion promptly restores effective atrial contraction, decreases LA size, and results in substantial hemodynamic benefit.

The echocardiogram of the anterior leaflet of the mitral valve. Correlation with hemodynamic and cineroentgenographic studies in dogs.

Abstract: The echocardiogram of the anterior leaflet of the mitral valve (ECHO) was compared to hemodynamic and cineroentgenographic data to evaluate its accuracy in timing mitral valve (MV) opening and closure, and to validate it as an indicator of MV motion. The ECHO, high speed cineroentgenography at 250 frames/sec, and/or measurement of intracardiac pressures allowed accurate timing of the events of MV motion in dogs on right heart bypass. The intersection of left ventricular and left atrial pressures in early diastole preceded the onset of rapid anterior motion of ECHO (D' point) by 17 to 33 plus or minus 7.6 msec; r equals 0.98. The onset of left ventricular systole occurred before the termination of final rapid posterior motion of the ECHO in end diastole (Co point) by 25 plus or minus 10 msec; r equals 0.96. Radiopaque clips were attached to the free edges of both leaflets of the MV. Cineroentgenographically determined plots of clip distance from the ultrasound transducer were morphologically similar to the simultaneously recorded ECHO. A delay of 23 plus or minus 3 (0 to 40) msec was observed in the ECHO peaks of diastolic anterior excursion compared to clip motion. Contrast medium advances beyond the free edges of MV leaflets mixing with left ventricular blood 43 plus or minus 3 msec after initial separation. These cineroentgenographic studies elucidate nonuniformity of leaflet motion responsible for ECHO delays. Thus, ECHO D' and Co correlate well with hemodynamic indicators of MV opening and closure. However, ECHO motion, although qualitatively similar, is unpredictably delayed compared to cineroentgenography of clips on the MV free edge. Since the ECHO correlates well with hemodynamic indices of MV opening and closure, this noninvasive technique can be used as a reference in the timing of intracardiac events and in the determination of systolic and diastolic time intervals.

The echocardiographic determination of mitral valve opening and closure. Correlation with hemodynamic studies in man.

Abstract: The ability of the echocardiogram to define mitral valve opening and closure was assessed by simultaneously recording the echocardiogram of the anterior leaflet (ECHO) with intracardiac pressures, aortic second sound, and ECG on 38 occasions in 14 patients undergoing cardiac catheterization. Hemodynamic opening and closure were defined by intersection of the pulmonary wedge and left ventricular pressures and the onset of left ventricular systole. The onset of the most rapid anterior motion (D9) in early diastole and termination of the last rapid posterior movement in end diastole (Co) were used as echocardiographic markers of mitral valve opening and closure. Intervals measured included: the isovolumic relaxation period (IRP) from A2 to either hemodynamic (IRPH) or echocardiographic (IRPE) opening; the Q to closure interval (QCI) from the Q wave to either hemodynamic (QCIH) or echocardiographic (QCIE) closure; and diastolic filling period (DFP), either hemodynamic (DFPH) or echocardiographic (DFPE). The following significant (P less than .01) regression equations resulted: IRPE equals (.97) IRPH plus 30 (sem plus or minus 8 msec) r equals .89; QCIE equals (.68) QCIH plus 37 (sem plus or minus 7 msec) r equals .71; DEPE equals (.98) DFPH plus 10 (sem plus or minus 18 msec) r equals .98. Thus hemodynamic markers of opening and closure systematically precede echocardiographic markers of opening (D9) and closure (Co) and the diastolic filling periods are equal within 10 msec. It is concluded that the echocardiogram of the anterior leaflet is a reliable indicator of hemodynamic markers of opening and closure of the mitral valve in man and is useful in the noninvasive determination of certain systolic and diastolic time intervals.

Motion of the tricuspid valve annulus in anesthetized intact dogs.

Abstract: Phasic variations in the size, position, and geometry of the tricuspid valve annulus during the cardiac cycle were studied in five normal anethetized dogs 2-6 weeks after 8-11 lead beads had been sutured on the endocardial surface of the valve ring during cardiopulmonary bypass. Field-by-field measurements from biplane videoangiograms were used to assess changes in valve ring size and shape during control hemodynamic conditions and during increased heart rates. In addition, the percutaneous production of a complete atrioventricular block in two dogs enabled us to observe the effect of isolated atrial contractions on the valve annulus. During normal sinus rhythm, progressive narrowing of the annulus during atrial and ventricular contractions reduced its area by 20-39% of the maximal valve circumference during diastole; approximately two-thirds of the total ring narrowing was associated with atrial systole. These findings suggest that one of the functions of atrial contraction is the reduction in size of the atrioventricular valve orifices prior to the onset of ventricular systole.

Premature pulmonic valve opening following sinus of Valsalva aneurysm rupture into the right atrium.

Abstract: Echocardiographic features of a patient with sinus of Valsalva aneurysm rupture into the right atrium are described. The aneurysm presented as a dense echo-producing mass in the right atrium which descended into the tricuspid orifice during diastole and withdrew back into the atrium during ventricular systole. Pulmonic valve exho motion demonstrated early diastolic pulmonic valve opening indicating an early right ventricular diastolic pressure rise exceeding simultaneous pulmonary artery pressure. Since the aorta is the only source of early diastolic pressure in excess of pulmonary artery pressure available to the right heart, this finding of early diastolic pulmonic valve opening indicated the presence of a fistula between the aorta and right heart. Other interesting echocardiographic features of this case are also presented.

Echocardiographic differentiation of infundibular from valvular pulmonary stenosis.

Abstract: Echocardiographic tracings of the pulmonary valve were examined in 24 normal subjects, 16 patients with valvular pulmonary stenosis and 3 patients with infundibular pulmonary stenosis. In normal subjects, atrial contraction produced a slight posterior opening motion of the pulmonary valve leaflet (a wave). This presystolic opening motion (a wave) varied with respiration, and maximal a wave depth recorded during quiet inspiration (Amax) averaged 3.7 plus or minus 1.2 (standard error of the mean) mm (range 2 to 7 mm). In the 10 cases with moderate or severe valvular pulmonary stenosis, increased force of right atrial contraction and elevated right ventricular end-diastolic pressure resulted in an increased posterior or opening motion of the pulmonary valve leaflet, and Amax averaged 9.6 plus or minus 2.0 mm (range 8 to 13 mm, P less than 0.001 versus normal). When both anterior and posterior leaflets were recorded, presystolic opening or doming of the valve was observed. In six cases of mild valvular pulmonary stenosis, Amax averaged 4 plus or minus 2.5 mm (not significant). In patients with infundibular pulmonary stenosis, marked chaotic systolic fluttering of the valve leaflet, which lies in the turbulent stream of blood distal to the obstruction, was recorded. This finding was never seen with valvular pulmonary stenosis. In two cases of mild infundibular pulmonary stenosis, the amplitude of presystolic opening motion was within the normal range of 3 and 7 mm. In one case of severe infundibular pulmonary stenosis, no presystolic opening motion was recorded, thus suggesting that the small pressure changes produced by atrial systole failed to reach the valve leaflets. Echocardiography, therefore, should be of use in differentiating valvular from infundibular pulmonary stenosis.

Shunt dynamics in experimental atrial septal defects.

Abstract: Inorder to study the hemodynamic variables involving the magnitude, direction, and timing of phasic shunt flow, both the interatrial pressure gradient and blood flow along with other pertinent hemodynamic variables were measured instantaneously across a surgically created atrial septal defect (ASD) in seven awake dogs. Atrial and ventricular pacing and infusion of phenylephrine and isoproterenol were used to alter hemodynamic conditions. The wave form of phasic ASD flow was similar both in configuration and timing to the interatrial pressure gradient. During the cardiac cycle, both left-to-right (L-R) and right-to-left (R-L) shunting occurred: atrial contraction augmented L-R flow; the onset of ventricular contraction was associated with R-L flow; during the latter part of ventricular contraction, flow returned to L-R with the maximum L-R shunting occurring in early diastole. Tachycardia, infusion of phenylephrine and isoproterenol did not alter the phasic flow pattern. Both spontaneous and positive pressure respiration decreased net L-R shunting.

Hemodynamic features of prolapsing and nonprolapsing left atrial myxoma.

Abstract: In the course of the evaluation of five patients with left atrial myxoma, it was noted that the movement of the myxoma was related to specific changes in left atrial hemodynamics. Prolapsing tumors, Type I, move from the left ventricle to the left atrium in early systole and from the left atrium to the left ventricle in early diastole, thereby causing prominent c and v waves accompanied by a rapid y descent. Nonprolapsing tumors, Type II, remain in the left atrium during the entire cardiac cycle, impeding flow across the mitral valve. In these latter cases, the y descent is slow and indistinguishable from that caused by mitral valvular stenosis. The cineangiocardiograms and echocardiograms corroborate these two types of hemodynamic observations. The particular value of direct echocardiographic examination of the left atrium prior to cardiac catheterization was evident in two of the three patients with nonprolapsing tumors. Since the hemodynamic pattern of nonprolapsing left atrial myxoma resembles that of mitral valvular stenosis, it is stressed that echocardiography should have an important place in precatheterization assessment of patients with mitral valve disease. If left atrial myxoma is suspected clinically or on the basis of echocardiographic findings, regardless of the pressure curve contours, transseptal cardiac catheterization should be avoided and the left atrium visualized by pulmonary angiography levophase.

Dynamic ventriculography and the role of the ejection fraction.

Abstract: Cardiac function is best evaluated in two different states since function may be normal at rest and abnormalities may become evident only when a load or stress is applied to the cardiovascular system. Such an intervention is exercise, typically used to provoke changes in the electrocardiogram or phonocardiogram, particularly when these are normal at rest. Similarly, hemodynamics have been studied in the cardiac catheterization laboratory at rest and during exercise. 1,2 These studies have concerned changes in pressures and flow, but not in the function of the heart as a pump, primarily because of the limitations of technique for quantifying the displacement capabilities of the beating heart. The advent of ventriculography allowed changes in wall motion and ventricular volume to be evaluated throughout the cardiac cycle. Most recently, the pumping action of the left ventricle has been analyzed, not only at rest but during a second state designed to test the reserve capacity of the heart in a manner similar to that of the earlier studies of pressure and flow. Dynamic ventriculography is the term that best characterizes this type of investigation.

Mechanical effects of heart contraction on coronary flow.

Abstract: The mechanical effects of heart contraction on coronary flow were studied in the dog heart by implanting vessels in the subendocardial and subepicardial layers of the left ventricular wall and perfusing them independetly of the aortic pressure. At a perfusion pressure of 4 kPa (30 mm Hg), with spontaneous aortic pressure and heart rate, subendocardial flow was 40% less than subepicardial flow. Increasing the aortic pressure or the heart rate produced a comparatively larger decrease of the subendocardial flow. The results suggest that these changes are due to variations of the period of systolic time during which the vessels remain close.

Transvenous Atrial Synchronized Pacing

Abstract: One of the great advances in cardiology over the past decade has been the development of a variety of means of pacing the heart electrically For the most part, electrical pacing has been applied to the ventricles for the treatment of symptomatic complete heart block There are occasions, however, when pacemaker therapy is indicated in patients with intact atrioventricular (AV) conduction Although ventricular pacing has been generally used for these purposes, the presence of normal AV-conduction permits stimulation of the heart from the atrium, thus taking advantage of the beneficial effect on cardiac performance and the well-documented augmentation of cardiac output obtained when a coordinated atrial systole just precedes ventricular contraction

[Diagnostic criteria of idiopathic hypertrophic subaortic stenosis in the echocardiogram(author's transl)].

Abstract: Idiopathic hypertrophic subaortic stenosis (IHSS) is morphologically characterized by ventricular septal hypertrophy. It is asymmetrical because there is no corresponding hypertrophy of the posterior wall of the ventricle. The proportion between septal thickness and posterior wall thickness is more than 1.2. In addition, the anterior mitral leaflet moves towards the ventricular septum during the ventricular systole. Finally, the aortic cusps may close prematurely, even during ventricular systole, if there is a marked outflow-tract obstruction. The thickness of the septum and posterior wall, as well as the movement of the mitral and the aortic valves, can be easily registered by the echocardiograph. IHSS is, therefore, more easily diagnosed by this non-invasive method than by any other method. The echocardiogram demonstrates (1) asymmetrical septal hypertrophy, (2) anterior movement of the anterior and frequently also the posterior mitral leaflet in midsystole, (3) partial or complete closure of the aortic valve in mid-systole, (4) relatively small end-diastolic and systolic diameters of the left ventricle, (5) delayed early-systolic closure movement of the anterior mitral leaflet in the sense of a functional mitral stenosis, (6) decreased systolic septal movement.

Interaction of aortic and carotid sinus baroreceptors: effect of activation times.

Abstract: Changes in pulse-wave velocity were simulated by changing the relative timing between aortic and carotid sinus barorecptor activity in anesthetized rabbits and dogs. In the rabbit, electrical stimulation was used to vary the timing; in the dog, it was also varied by perfusing the carotid sinuses with externally generated pressure pulses that could be triggered in any portion of the cardiac cycle. Changing the relative delay between aortic and carotid sinsus nerve stimulation did not result in variations of blood pressure or heart rate in the rabbit. Varing the time of electrical stimulation of the carotid sinus nerve caused at most 5 mmHg change of blood pressure in the dog. Delay-related heart-rate changes could be usually observed only when the stimulus consisted of short, high-intensity bursts. When the carotid sinus was externally perfused with pulses of pressure, only one out of five dogs showed delay-related variations in blood pressure (3mmHg) and heart rate (6 beats/min). It is concluded that variations in pulse-wave velocity are unlikely to play a significant role in acute cardiovascular control.

[Camera-cinematography of the heart (author's transl)].

Abstract: By "camera-cinematography" of the heart, we mean an isotope method which permits detailed observation of cardiac mechanics without the use of a catheter. All that is necessary is an intravenous injection of 10 to 15 mCi 99mTc human serum albumen followed after ten minutes by a five to ten minute period of observation with a scintilation camera. At this time the isotope has become distributed in the blood. Variations in the precordial impulses correspond with intra-cardiac changes of blood volume during a cardiac cycle. Analysis of the R-wave provides adequate information of cyclical volume changes in limited portions of the heart. This is achieved by a monitor with a pseudo-3-dimensional display; contraction and relaxation of the myocardium can be shown for any chosen longitudinal or horizontal diameter of the heart. Our programme allows simultaneous presentation of the movement of any point on the myocardium as a time-activity curve. The method is recommended as an addition to chest radiography, heart screening or cardiac kymography before carrying out cardiac catheterisation.

Videodensitometric determination of left ventricular ejection and filling characteristics.

Abstract: Left ventricular ejection fraction and values proportional to mitral and aortic flow were measured throughout the cardiac cycle by videodensitometric analysis of left ventricular roentgen angiograms. The technique was used simultaneously with measurement of the dimensions of the ventricle to provide absolute values for comparison. Sensitivity of the technique was tested by the ability to detect the atrial contribution to mitral flow and left ventricular chamber volume. Roentgen videodensitometry has the advantages that much information can be extracted from videoangiograms in real-time (on-line, if need be), it requires relatively low concentration of contrast medium, and it is self-calibrating.

Delay and block of cardiac impulse caused by enhanced phase-4 depolarization in the His-Purkinje system.

Abstract: The underlying mechanism of bradycardia-dependent bundle-branch and paroxysmal atrioventricular block appears to be enhancement of phase-4 depolarization in a branch or in a natural or acquired monofascicular pathway. Clinical records of these forms of impaired conduction occurring in the bundle-branches, with either longer or shorter cardiac cycle lengths, are presented and analysed. These also include the combination of Mobitz typw I atrioventricular block with variable degrees of bundle-branch block, as a representative example of narrow ventricular escape beats firing in the zone where prominent diastolic depolarization is present.

Pulmonary Vein Flow in Mitral Valve Disease

Abstract: Pulmonary vein blood flow in mitral valve disease was studied peroperatively in 10 patients undergoing valve replacement. Flow was recorded using a Nycotron electromagnetic flowmeter with a cuff type probe on the right upper pulmonary vein. Pressures in the left atrium and ventricle were recorded simultaneously. the recordings were made both before cannulation for extracorporeal circulation and after mitral valve replacement. the flow curves had a pulsatile pattern and reflected the pressure events in the left atrium. Forward flow reached maximum during ventricular diastole and was reversed during ventricular systole. Maximum retrograde flow coincided with a peak of the left atrial v-wave. With a few exceptions, there was good agreement between the degree of pulmonary vein retrograde flow and grade of mitral insufficiency at left ventricular angiography. After valve replacement, no retrograde pulmonary vein flow was observed. in the majority of patients the v-wave in the left atrium was markedly reduced b...

Economical Dynamic Cardiac Imaging

Abstract: To date, echocardiography has been confined to A-raode and M-mode recordings. While these display formats have been extremely useful and provided much clinical information, there is a need for two-dimensional, anatomical cardiac imaging with the capability of demonstrating motion. This need has resulted in a sharp increase in development work in many different institutions.

In Vivo Tests

Abstract: In addition to an analysis of error sources and their influence on the accuracy of the result as will be given in Chapter XI, in vivoexpetiments are necessary. Besides the overall testing of the system, especially of the time programming by microcomputer, the effects of the geometric model fit and the interindividual variability have to be established in the real situation. During “steady state” of the circulation under controlled circumstances--especially with a constantly paced rhythm--thermodilution gives a measure for the cardiac output (from which the stroke volume can be derived by dividing through the heart rate) with a coefficient of variation of 4.3% (VAN DER WERF,1965). During this procedure, an electromagnetic flow meter can be calibrated, so that the unknown aortic lumen, haematocrit and other factors may be accounted for. In this way, stroke volume may also be established with varying heart rate. Although the blood flow into the coronary arteries escapes measurement--and this error may be estimated to be about 3% of mean flow--in determining stroke volume it may be neglected because the maximum coronary flow occurs well after the end of the ventricular systole.

Results of a Comparative Study with Adalat: Phonomechano-Cardiograms in Normal Persons and Patients with Coronary Heart Disease

Abstract: The duration of the phases of the left ventricular systole depends intrinsically on the condition of the myocardium and its contractile synergy as varied by means of the preload, afterload and heart rate (HR) (Fig. 1) [5, 7–9, 11, 15, 18, 21, 23, 26–29, 32, 43, 53, 55, 61, 66, 72, 73, 75–80, 82, 83, 85, 86].