Leaflet Closure Research Articles

Effects of Age, Water Stress, and 1-Aminocyclopropane-1-carboxylic Acid on Leaflet Movement in Albizzia julibrissin

The movement patterns of Albizzia julibrissin leaflets transferred from light to darkness differ for leaflets of different age: the older the leaflet, the slower and less completely it closes. Water stress, which enhances ethylene synthesis in other plants, and 1-aminocyclopropane-1-carboxylic acid (ACC), precursor of ethylene, both mimic the effect of aging by reducing the rate and extent of dark-induced closure. Brief far-red compared to red irradiation before darkness does not appear to alter the closure of young leaflets, but far-red preirradiation retards the closure of middle-aged and old leaflets floating on water, and middle-aged leaflets treated with ACC. A change in some membrane property and/or cell wall lignification are suggested as possible explanations for the alteration of leaflet movement.

Noninvasive in vivo and in vitro study of the St. Jude mitral valve prosthesis: Evaluation using two dimensional and M mode echocardiography, phonocardiography and cinefluoroscopy

Fifteen patients with clinically normal function of a St. Jude mitral valve prosthesis were studied with two dimensional and M mode echocardiography, Cinefluoroscopy and phonocardiography 8 to 292 days after valve replacement. The valve was readily imaged from the left sternal edge and cardiac apex in all patients. On two dimensional echocardiography from the long axis and four chamber views, minimal end-diastolic and endsystolic distances between the interventricular septum and prosthetic valve were 18 ± 5 mm and 13 ± 3 mm, respectively (mean ± standard deviation). On M mode echocardiography both leaflets were imaged throughout the cardiac cycle from the left sternal edge and their motion relative to the valve ring and to one another was easily evaluated. The apical transducer position permits quantitative assessment of individual leaflet motion. Maximal individual diastolic leaflet excursion was 8.7 ± 1 mm and the velocity of leaflet opening and closure was 364 ±103 and 678 ±115 mm/s, respectively. Asynchronous early closure of the posterior leaflet was observed during long cardiac cycles in six of seven patients with atrial fibrillation; the seventh patient had a rapid ventricular response and no long cardiac cycles. Diastolic fluttering of one or both leaflets was also seen during atrial fibrillation after rotation of the patient from the supine to the left lateral decubitus position. Three of the six patients with asynchronous leaflet closure underwent Cinefluoroscopy, and similar leaflet behavior was documented in all. An atrial systolic wave was inscribed in the valve echogram in six of eight patients with sinus rhythm. Phonocardiography recorded prosthetic valve opening and closing sounds occurring 60 ± 20 ms after aortic closure and 61 ± 12 ms after the QRS complex, respectively. The prosthetic valve opening and closure sound amplitude ratio was 0.11 ± 0.06. A clear plexiglass water bath phantom was fitted to a pulse duplicator and constructed so as to permit in vitro simulation of valve echograms under a variety of conditions. With this method, it was possible to reproduce or approximate all images obtained in patients from both echocardiographic transducer positions.

Vanadate inhibition of phytochrome effects on leaflet movement in Albizzia julibrissin

A previous report revealed that the transport inhibitor sodium vanadate interferes with the rhythmic closure of Albizzia julibrissin leaflets during an extended dark period. Vanadate (0.5–1.0 mM) also prevents phytochrome conversion from affecting the movements, acting selectively on leaflets whose phytochrome is in the P fr form. Leaflet closure following transfer from white light to darkness is inhibited to a similar extent by vanadate or by brief far-red pre-irradiation, while leaflet opening during an extended dark period is promoted by vanadate or by brief far-red irradiation, although the kinetics of movement under the latter two conditions differ from each other. Sodium monophosphate, by contrast, promotes the closure of leaflets transferred directly from white light to darkness, but it does not affect the closure of far-red pre-irradiated leaflets, or the rhythmic opening of either far-red irradiated or non-irradiated leaflets. It is not known whether vanadate inhibits a primary action of P fr or a later reaction in the chain of events that link leaflet movement to phytochrome conversion.

Incomplete mitral leaflet closure in patients with papillary muscle dysfunction.

Clinical acceptance of an association between papillary muscle dysfunction and mitral regurgitation is widespread, despite the lack of objective support. To evaluate a possible association, we performed echocardiographic examinations on 22 patients with prior myocardial infarction and clinical evidence of papillary muscle dysfunction, 40 patients with prior myocardial infarction and no clinical evidence of papillary muscle dysfunction, and 20 normal subjects. There was a unique pattern of incomplete mitral leaflet closure in a high percentage (91%) of infarct patients with mitral regurgitation. In these patients, one or both leaflets were effectively arrested within the cavity of the left ventricle during ventricular systole. Dyskinetic wall motion in the region immediately surrounding one of the papillary muscles was present in 23 of 24 patients (96%) with demonstrated incomplete closure. This study provides the first objective evidence that de novo mitral regurgitation in patients with prior myocardial infarction is due to dyskinesis involving the left ventricular myocardium beneath one of the papillary muscles, producing increased tension on the mitral leaflets and preventing normal closure.

Role of the papillary muscle in opening and closure of the mitral valve.

Dimensional changes of the left ventricular anterolateral papillary muscle of six open-chest dogs were measured continuously throughout the cardiac cycle in order to evaluate the role of the papillary muscle in opening and closing of the mitral valve. Dimensional changes were measured with ultrasonic dimension gauges. Maximal shortening and maximal elongation of the papillary muscle followed maximal shortening and elongation of a segment of the free wall of the left ventricle by 65 +/- 6 (SE) ms. Maximal elongation of the papillary muscle occurred 25 +/- 2 ms after the onset of ejection. Maximal shortening of the papillary muscle occurred 68 +/- 5 ms after the aortic incisura and 10 +/- 2 ms after the crossover of left ventricular and left atrial pressure. The papillary muscle shortened 14 +/- 4%. The percentage of papillary muscle shortening that occurred after the aortic incisura was 39 +/- 7%, and the percentage of shortening that occurred after the crossover of left ventricular and left atrial pressure was 3 +/- 1%. The observed shortening of the papillary muscle throughout left ventricular isovolumic relaxation suggests that the papillary muscle may have a role in opening the mitral valve. Conversely, elongation of the papillary muscle in the late portion of diastole appears necessary to permit proper closure of the mitral valve leaflets.

Intraoperative Assessment of the Mitral Valve Following Reconstructive Procedures

A technique facilitating intraoperative assessment of the degree of mitral insufficiency during and after mitral reconstructive procedures has been developed. A multiholed left ventricular vent catheter is advanced across the aortic valve, thereby creating aortic insufficiency, filling the left ventricle with blood at aortic perfusion pressure, and approximating the leaflets of the mitral valve in the closed position. If present, mitral insufficiency can be estimated by the size of the regurgitant jet. In addition to assessing valve function following open mitral valvotomy, the method has also been helpful in managing leaks around the prosthetic valve, in assessing the closure of cleft mitral valve leaflets associated with ostium primum atrial septal defects, in confirming the completeness of closure, and in detecting obscure ventricular septal defects.

Echocardiography of the aortic root

The anterior and posterior walls of the aortic root are recognized as a pair of parallel linear signals which move anteriorly in systole and posteriorly in diastole. Valve cusps appear as thin lines which move briskly toward the periphery of the aortic lumen in systole and coapt in the middle in diastole producing a box-like configuration. Cusp calcification results in the appearance of multiple, linear echoes within the aortic root. Mild aortic stenosis is characterized by lightly calcified leaflets whereas heavy calcification, which completely obscures cusp motion, signifies severe stenosis. Aortic aneurysms produce significant enlargement of the aortic root image; marked widening of the aortic walls indicates the presence of aortic root dissection, but there are important limitations and pitfalls in the diagnosis of this condition. A markedly eccentric diastolic cusp position within the aortic lumen resulting in asymmetric images of the leaflets in systole is the hallmark of a bicuspid aortic valve. An abrupt premature closure of the valve leaflets in early systole is typical of subaortic membranous stenosis. In tetralogy of Fallot the aortic root is dilated and overrides the ventricular septum.

ANALYSIS OF THE TEMPORAL SEQUENCE OF LEFT VENTRICULAR SYSTOLE IN NORMAL CHILDREN BY ECHOCARDIOGRAPHY

Little data are available regarding measurements of the active state of left ventricular (LV) segmental contraction. Thus we performed echograms (E) in 40 normal school children, to establish and relate normal values for the period of LV systole, as assessed by a variety of E parameters. Duration of contraction of posterior LV wall (LVWSF) and Septum (SSP) was measured from the onset of movement to the point of maximal systolic anterior or posterior excursion respectively. Mitral valve coaptation (MSP) was computed as the duration between closure and opening of the mitral leaflets, as was aortic ejection period (ASP) from seperation to reclosure of the aortic leaflets. Systolic periods measured in milliseconds were: (mean and standard error of mean) LVWSP 281.1 ± 2.8, SSP 261.7 ± 2.6, MSP 316.3 ± 4.4 and ASP 269.5 ± 3.2. Further maximal excursion and systolic thickening of S and LVU were simultaneous. A marked difference between MSP and ASP (48.9±3.5, p <0.001) represented isovolumic LV contraction and relaxation. Thus E may be utilized to analyze isovolumic LV systole. It appears that S systolic excursion may be completed and LVW systolic motion may continue after aortic ejection finishes. The difference between S and LVW systolic period suggests that the active state of contraction of LVW is greater than that of S, and is more important to LV contraction in normal children. (Sponsor: Eli Gold)

Investigation of the theory and mechanism of the origin of the second heart sound.

To investigate further the origin of the second heart sound we studied human subjects, dogs, and a model in vitro of the cardiovascular system. Intra-arterial sound, pressure, and, where possible, flow and high speed cine (2,000 frames/sec) were utilized. The closure sound of the semilunar valves was of higher amplitude in be ventricles than in their respective arterial cavities. The direction of inscription of the main components of intra-arterial sound were opposite in direction to the components of intraventricular sound. Notches, representative of pressure increments, were noted on the ventricular pressure tracings and were coincident with the components of sound. The amplitude of the closure sound varied with diastolic pressure, but remained unchanged with augmentation of forward and retrograde aortic flow. Cines showed second sound to begin after complete valvular closure, and average leaflet closure rate was constant regardless of pressure. Hence, the semilunar valves, when closed, act as an elastic membrane and, when set into motion, generate compression and expansion of the blood, producing transient pressure changes indicative of sound. The magnitude of the initial stretch is related to the differential pressure between the arterial and ventricular chambers. Sound transients which follow the major components of the second sound appear to be caused by the continuing stretch and recoil of the leaflets. Clinically unexplained findings such as the reduced or absent second sound in calcific aortic stenosis and its paradoxical presence in congenital aortic stenosis may be explained by those observations.

Motion of both mitral valve leaflets: a cineroentgenographic study in intact dogs.

Motion and position of both mitral leaflets were studied in five normal dogs 1-11 wk after radiopaque markers were sutured on the valve cusps and on the mitral annulus. Cinefluorograms and cineangiograms (100-120 frames/s) of left atrium and left ventricle were used to study cusp motion and intraventricular flow patterns, and to detect mitral regurgitation during sinus rhythm (42-184 beats/min) and during isolated atrial or ventricular contractions. Time-motion of both leaflets was similar throughout diastole with the exception of delayed posterior cusp opening. Peak opening and closing speeds, opening and closing times, and time of complete closure, measured from the Q wave of the ECG, were not significantly affected by the variations in heart rate. Diastolic leaflet closure began immediately after opening, while the ventricular cavity was small, and was caused by flow eddies behind the cusps. Isolated ventricular contractions closed the valve leaflets completely and symmetric valve closure was ensured by the different rates of leaflet edge approximation. In contrast, atrial closure was slow, partial, and of very short duration.

The first heart sound in complete heart block. Phono-echocardiographic correlations.

Eight subjects with complete atrioventricular heart block were studied with simultaneous echocardiography and phonocardiography to investigate the role of the mitral and tricuspid valves in the genesis of the first heart sound (S 1 ). Mitral valve motion was studied in all cases and tricuspid patterns in three. At P-R intervals less than 0.20 sec, mitral leaflet closure was completed by ventricular systole. Below P-R values of 0.20 sec there was an inverse relationship between P-R and S 1 amplitude. With P-R between 0.20 and 0.50 sec atrial systole closed the mitral valve without recordable sound. Beyond P-R intervals of 0.50 sec there was reopening of the mitral valve and secondary closure initiated by ventricular systole which was coincident with S 1 . The extent of mitral leaflet separation at the onset of ventricular systole correlated with S 1 amplitude. Pre-ejection period was not related to S 1 intensity. Over a wide range of P-R intervals in two subjects with a split S 1 , tricuspid valve closure was simultaneous with the second S 1 component. It was concluded that atrioventricular valve closure is a necessary event in the production of S 1 and that at least in some individuals tricuspid valve closure is related to its second high frequency component.

Echocardiographic manifestations of discrete subaortic stenosis

The echocardiographic manifestations of discrete membranous subaortic stenosis are described in three cases. The diagnosis was confirmed by cardiac catheterization in all and at operation in two. The characteristic finding in these patients was abnormal movement of the aortic valve leaflets. The leaflets opened rapidly with the onset of systole, then exhibited abrupt premature closure shortly after ventricular ejection. The valve remained partially closed throughout the remainder of systole. This premature leaflet closure Is believed to be caused by obstruction to aortic valve flow produced by the band-like fibrous subaortic tissue. The valve leaflets also exhibited a gross fluttering motion possibly caused by a jet stream effect of the turbulent blood hitting the leaflets. In the two patients treated surgically, postoperative echograms continued to show premature leaflet closure but the degree of closure was decreased. The echocardlogram of one patient had the characteristic systolic anterior bulge of the mitral valve observed in muscular subaortic stenosis or idiopathic hypertrophic subaortic stenosis. Our data suggest that the following echocardiographic findings are suggestive if not specific for discrete subaortic stenosis: aortic valve closure early in systole, persistent valve closure throughout the remainder of systole, coarse fluttering of the leaflets, and absence of asymmetric septal hypertrophy.

Echocardiographic Assessment of Idiopathic Hypertrophic Subaortic Stenosis

Echocardiography provides a reliable, sensitive and practical noninvasive means for the accurate diagnosis of idiopathic hypertrophic subaortic stenosis (IHSS) and the sequential assessment of severity of left ventricular outflow obstruction in the management of this condition. The principal echocardiographic features of IHSS have been demonstrated to include: (1) anterior displacement of the anterior mitral valve in midejection; (2) asymmetric ventricular septal hypertrophy; (3) anterior position of the mitral valve at the onset of systole; (4) forward systolic movement of the posterior mitral leaflet; (5) reduced rate of anterior mitral valve closure in diastole; and (6) partial closure of the aortic leaflets in midejection. The characteristic abnormalities of anterior systolic leaflet motion observed on mitral valve echogram and the response of the leaflet to provocative maneuvers and surgical treatment strongly support the importance of the role of obstruction in IHSS and the apposition of the anterior mitral leaflet, with the hypertrophied ventricular septum as the site of subaortic stenosis.

The relationship of the jugular “C” wave to changing diastolic intervals

To determine the relationship of the jugular C wave to changing cycle length, jugular pulse and right atrial pressure recordings were examined on a group of patients with various types of heart disease and atrial fibrillation. The total height of the jugular C wave was noted to be enhanced by short cycles and diminished with longer cycles. This finding is confirmed with intra-atrial pressure recordings. It is suggested that the jugular C wave is related to tricuspid leaflet excursion and closure; in that with a short diastolic interval the leaflets are widely separated at the onset of systole and have a relatively large closure excursion. These findings are not consistent with the hypothesis of arterial origin of the C wave since the arterial pulse would be expected to increase with longer cycles.

PHYTOCHROME CONTROLLED NYCTINASTY IN ALBIZZIA JULIBRISSIN. II. POTASSIUM FLUX AS A BASIS FOR LEAFLET MOVEMENT

Excised Albizzia leaflet pairs exposed to red (R) light close within 30–90 min after transfer to darkness. Interruption of darkness by far‐red (FR) light at any time after R inhibits closure within ca. 10 min. Similarly, irradiation with R at any time after prior FR promotes closure within ca. 10 min, and the increased rate of closure is independent of the time lapse between the FR and R irradiations. Closure in the dark is inhibited by NaN3 and DNP (5 X 10–4 m), by anaerobic conditions and by externally applied salts of monovalent cations, especially K; it is also temperature sensitive. Pulvinule cells are very high in K. Electron microprobe analysis of cryostated, lyophilized pulvinules reveals that during closure, K is lost from ventral cells and enters dorsal cells. FR before darkness inhibits the former but not the latter process. Thus, K flux appears to control the changes in volume of the pulvinule cells that control leaflet movement. While leaflet closure normally requires a dark period, salts of organic acids such as sodium acetate, propionate, and butyrate cause closure in the light.

PHYTOCHROME CONTROLLED NYCTINASTY IN ALBIZZIA JULIBRISSIN. I. ANATOMY AND FINE STRUCTURE OF THE PULVINULE

Under appropriate experimental conditions, phytochrome controls leaflet closure in Albizzia by regulating differential turgor changes in motor cells of the pulvinule. Closure occurs when subepidermal dorsal cells expand and ventral cells become compressed; reopening involves the reverse changes. The internal cells surrounding the vascular core remain relatively unchanged during leaflet movement. Fine structural studies revealed several unusual features of the motor cells including: (1) fibrils oriented parallel to one another in the cytoplasmic matrix; (2) numerous spherosomes that appear to coalesce and enlarge to form vacuoles; and (3) a multivacuolate condition.

Mitral stenosis

Dr. Gilbert H. Mudge: Mitral stenosis is one of the most common and most important results of rheumatic fever. Although a comprehensive discussion of the problem must include the cause and prevention of the underlying disease, this clinic has focused attention on the hemodynamic aspects of stenosis as a basis for considering the newer methods of surgical therapy. The action of the valve itself has been studied by direct visualization in experimental animals. This ingenious technic has permitted accurate description of the behavior of the valve throughout the cardiac cycle. Closure of the valve consists of two components: first, a muscular contraction of the ring which greatly reduces the aperture, and second, closure of the valve leaflets. The special significance of the large aortic leaflet is discussed. The hemodynamic sequelae of mitral stenosis are described in an attempt to correlate the functional abnormalities with important clinical features such as dyspnea, hemoptysis and arrhythmias. Cardiac function has been studied under different conditions of exercise, heart rate and cardiac rhythm; it can be analyzed in terms of at least three major factors, the valvular deformity, changes in the pulmonary vascular bed and the myocardial reserve of both sides of the heart. The importance of the muscular component is illustrated by the hemodynamic changes resulting from digitalization and from acute myocarditis. Physiologic effects of stenosis and insufficiency are so complex that it is often difficult to correlate symptoms with function. Since the success of surgical correction eventually depends on such a correlation, it is important to continue to follow patients by precise physiologic methods. The indications and contraindications for the surgical correction of mitral stenosis are considered, with recognition of both the tentative nature of present data as well as the benign nature of the lesion in the vast majority of patients. Rheumatic activity must be considered a major contraindication to surgery. The technical aspects of commissurotomy are discussed in relation to the structure and function of both the normal and diseased valve leaflets. Since acute mitral insufficiency is very poorly tolerated, the modern operation for correcting stenosis has been so devised that the baffle action of the large aortic leaflet is preserved, thus producing a “selective” mitral insufficiency. Problems of pre- and postoperative management are discussed, as are the acute circulatory changes which occur during the surgical procedure. Results of commissurotomy appear promising although longer periods of follow-up are needed for final evaluation.