Mean Left Atrial Research Articles

Evaluation of pulmonary arterial end-diastolic pressure as an indirect estimate of left atrial mean pressure.

Simultaneously recorded values for mean left atrial pressure (LAMP) and end-diastolic pulmonary arterial pressure (PAEDP) were compared in 28 patients with acute or chronic cardiac disease. Atrial pressure was varied by alterations in blood volume or the administration of inotropic agents. One hundred twenty paired values were divided into three groups according to the pulmonary vascular resistance which was calculated on each occasion. Although LAMP and PAEDP were shown to correlate significantly at all levels of pulmonary vascular resistance, worthwhile estimates of LAMP could only be obtained from PAEDP when the pulmonary vascular resistance was normal.

Haemodynamic results of aortic valve replacement with the Kay-Shiley disc valve.

Thirty-nine patients, operated on 8 to 14 months previously with replacement of the aortic valve by a disc valve (Kay-Shiley), were subjected to a postoperative follow-up investigation including right and left heart catheterization. Pre-operatively, aortic stenosis was present in 14 cases, aortic insufficiency in 8, combined stenosis and insufficiency in 15 and an associated mitral stenosis in 2 cases.Physical working capacity (W150) was unchanged, while exercise tolerance (Wmax) was significantly increased after operation (from 460 to 670 kpm/min). Cardiac output in relation to oxygen uptake was lower than normal pre-operatively and was unchanged postoperatively. Left ventricular pressures diminished significantly; the peak systolic pressure decreased from 210 to 157 mmHg at rest and from 241 to 172 mmHg during exercise, and the end-diastolic pressure from 23 to 13 mmHg at rest and from 32 to 19 mmHg during exercise. Left atrial (or PCV) mean pressure decreased from 17 to 10 mmHg at rest and from 31 to 1...

Hemodynamic response to discoid mitral valve replacement.

Hemodynamic studies were performed before and daily for 7 to 10 days after mitral valve replacement with a discoid prosthesis in 15 patients. Left atrial mean pressure fell from a mean of 27.5 mm Hg before surgery to normal levels (mean 11 mm Hg) within 24 hours of surgery. Cardiac index reached normal levels (mean 2.97 L/min/m 2 ) within 48 hours of valve replacement, and remained in the normal range throughout the early postoperative period in 12 of the 15 patients. The association of normal left atrial pressure and cardiac output in response to the increased metabolic demands of the postoperative period has not been reported with caged-ball mitral valve replacement. Pulmonary artery mean pressure and pulmonary vascular resistance showed a sharp decrease toward normal in the early postoperative period. In seven patients with systemic pulmonary hypertension, pulmonary artery mean pressure decreased from 72 mm Hg before surgery to 38 mm Hg at 7 to 10 days. The observed hemodynamic findings in these patients are consistent with experimental evidence that discoid mitral prostheses offer less resistance to blood flow than caged-ball mitral prostheses.

Measurement of cardiac output by thermal dilution in man.

Measurement of cardiac output by thermal dilution in man.

Hemodynamic characteristics of abnormal distribution of pulmonary blood flow in patients with cardiac disorders.

Lung profile scanning using I131 labeled macroaggregated albumin (I131-MAA) was presented as a quantitative estimation of regional pulmonary blood flow. Distribution index in four parts of the lungs (right, left, upper, and lower) was calculated from the area under MAA-pulmogram.Characteristics of the impaired distribution of pulmonary arterial flow in cardiac diseases were elevation of U/L ratio which consisted of decrease of blood flow in the lower zone associated with increase in the upper zone.Increased U/L ratio was more characteristic in the patients with left heart failure than with any other specific diseases. From the correlation with hemodynamic variables obtained by the combined right and transseptal left heart catheterizations, increased U/L ratio was found to correlate significantly with left atrial mean pressure. Left atrial mean pressure below 10mm.Hg did not make U/L ratio elevate. When it exceeded 10mm.Hg U/L ratio was observed to increase linearly in proportion to the increased left atrial mean pressure. These facts are well explained by the interstitial perivascular edema of the dependent zone in the isolated perfused dog lung which was first introduced by West et al. in 1965. This external counting technique using I131-MAA is clinically useful to estimate the severity of various acquired cardiac diseases.

Measurement of pulmonary edema in valvular heart disease.

Pulmonary extravascular fluid volume (PEV) has been estimated by using a double isotope technique in nine normal subjects and 45 patients with valvular heart disease. The method was reproducible, the standard deviation being±15.2 ml/m 2 , or 11.2% of the mean. Groups of patients with aortic and mitral valve disease had significantly higher values of PEV than normal persons; some patients with pulmonary stenosis had subnormal values. There was a relationship between PEV and the severity of dyspnea; all patients with an abnormally high PEV were class II or worse. Of the 18 patients with abnormally high PEV, only seven had radiological evidence of chronic pulmonary edema. PEV was independent of blood flow but was clearly related to the level of pulmonary intravascular pressure. PEV was only significantly elevated if left atrial mean pressure exceeded 12 mm Hg and was invariably raised if it exceeded 25 mm Hg. No relationship of PEV to pulmonary vascular resistance was evident in this study.

Response of pulmonary blood volume to 64 to 114 weeks of intermittent stay at high altitudes

Data on the pulmonary blood volume and related hemodynamic parameters obtained by cardiac catheter studies in 11 healthy volunteers before and after 64 to 114 weeks of intermittent stay at an altitude of 14,500 feet have been presented. The heart rate decreased by 13 per cent, pulmonary flow increased by 60 per cent, and stroke volume increased by 77 per cent. The central and pulmonary blood volumes showed an average increase of 97 and 76 per cent, respectively. Pulmonary arterial and left atrial mean pressure values showed some elevation but remained within the upper limits of our normal values. When the increases in the flow and blood volumes were related to the duration of total and continuous stays at high altitude, better correlation was apparent with the last continuous stay prior to the restudy than with the total stay. Although central blood volume and pulmonary flow increased within 25 weeks and remained increased, with some fluctuation, the increase in the pulmonary blood volume was apparent only after 25 weeks of stay, after which it increased progressively. It is suggested that increased pulmonary flow and pulmonary blood volume but normal pulmonary arterial pressure, as seen here, may represent a form of successful adaptation in temporary residents of high altitude.

The Gradient in Pressure Across the Pulmonary Vascular Bed During Diastole

By means of right and left heart catheterization 70 patients with congenital or acquired heart disease were examined to determine whether or not a gradient in pressure existed between the pulmonary artery and the left ventricle at the end of diastole. In the absence of mitral valvular obstruction in 56 patients there was a statistically significant correlation of pulmonary artery diastolic, left ventricular end-diastolic, and left atrial mean pressures less than 15 mm Hg which was independent of heart rate. Diastolic pressures at identical levels as high as 40 mm Hg were demonstrated in the presence of aortic insufficiency without left ventricular failure, and as high as 47 mm Hg during pulmonary edema in one patient with aortic stenosis and insufficiency. A diastolic gradient in pressure between the pulmonary artery and the left ventricle existed in 14 patients with pulmonary hypertension. These patients all had congenital intracardiac shunts and it may be assumed that they had some obstruction in the pulmonary vascular bed. These findings suggest that within defined limits friction across the pulmonary vascular bed is so small that a state of pressure equilibrium exists at the end of diastole. When the limits are met clinically, the pressures in the pulmonary artery and in the left ventricle at the end of diastole are identical.

The second sound-mitral opening snap (A2-OS) interval during exercise in the evaluation of mitral stenosis.

Cardiac catheterization and phonocardiography data were obtained from patients with mitral stenosis at rest and during exercise. There was a linear relationship between the percentage decrease of the interval from closure of the aortic valve to the mitral valve opening snap (A2-OS) and the percentage increase [see figure in the PDF file] of the left atrial mean pressure from rest to exercise. The duration of the A2-OS interval was an effective indicator of the level of the left atrial mean pressure during exercise. The duration of the A2-OS interval during exercise allowed separation of patients with mild stenosis from those with moderate or severe stenosis but could not be used to distinguish moderate stenosis from severe stenosis.

The Pulmonary Blood Volume in Rheumatic Heart Disease and Its Alteration by Isoproterenol

Pulmonary blood volume was measured in five hemodynamically normal subjects and 37 patients with heart disease. Mean pulmonary blood volume in 25 of these patients with moderate to severe mitral stenosis, alone or complicated by other valvular lesions, was 359 ml. per M.2 (SE = +/-24 ml. per M.2), which was significantly higher than the average value of 230 ml. per M.2 (SE = +/-14 ml. per M.2) in the five normal subjects (p < 0.025). Multiple correlation of pulmonary blood volume with left atrial mean pressure, pulmonary vascular resistance, and stroke volume showed that each of these factors was significantly related to pulmonary blood volume, independently of the others. Increased left atrial pressure or stroke volume was associated with relatively high, and increased pulmonary vascular resistance with relatively low pulmonary blood volume. In seven subjects 10 to 20 mg. of isoproterenol administered sublingually led to a marked increase in pulmonary blood volume and a small decrease in pulmonary vascular resistance. The average increase in pulmonary blood volume was 78 ml. per M.2, or 35 per cent of the control value (SE = +/-15 ml. per M.2), while the average drop in pulmonary vascular resistance was 1.3 R.U.M.2 (SE = +/-0.5 R.U.M.2). Since the change in volume was too large to be accounted for by arteriolar dilatation alone, and there was a simultaneous decrease in pulmonary arterial and left atrial pressures, isoproterenol apparently increased the distensibility of a large but as yet unidentified segment of the pulmonary vascular bed.

Left heart studies in mitral stenosis with special reference to intracardiac phonocardiography

1. 1. A study was made of 33 patients with mitral valve disease by means of left and right heart catheterization, conventional phonocardiography and intracardiac phonocardiography of the right and left heart. The intracardiac phonocardiogram was recorded by the electronic method from the catheter used for recording pressures. Fourteen cases were operated upon, and 2 of them were examined at autopsy. The severity of the diagnosis was confirmed by the surgeon. 2. 2. A minor delay (10 milliseconds) was found in the vibrations of the intracardiac phonocardiogram over those of the external phonocardiogram. These are inherent in the method used. 3. 3. The intracardiac phonocardiogram proved of great utility in identifying the murmurs, their point of origin, their phase and mechanism. Greater amplitude of the third or fourth sound, and of the opening snap, was often found. 4. 4. A comparative study of the intracardiac sounds and pressures revealed that the first sound is delayed over the point of crossing of the ventricular and atrial pressures, and that the opening snap is delayed over the point of crossing of the atrial and ventricular pressures, confirming data already gathered in an experimental study. 5. 5. The first sound of the left side of the heart often followed that of the right side. This was particularly evident in cases with atrial fibrillation after a short diastole, and was true only in severe mitral stenosis. This confirms previous statements by others. 6. 6. Even though a relationship was found between Q-1 and 2-OS, respectively, and both the values of the left atrial mean pressure and the left atrial-left ventricular diastolic gradient, this relation was not as close as stated by previous authors, possibly because their data were based on right heart catheterization alone or catheterization plus surgical findings.

Hemodynamic Effects of a Pressor Amine (Methoxamine) with Predominant Vasoconstrictor Activity

A pressor amine (methoxamine) which produces peripheral vasoconstriction, while lacking a significant, direct, positive inotropic effect upon ventricular heart muscle, has been shown to produce hemodynamic effects that are in distinct contrast to those resulting from the injection or infusion of l -epinephrine and l -norepinephrine in "physiologic" concentrations or of mephentermine sulfate. The latter 3 amines, possessing a positive inotropic action in addition to varying vasoconstrictor effects, decrease right and left atrial mean pressures while increasing femoral and pulmonary arterial pulse and mean pressures, right and left ventricular stroke works and the cardiac index. Methoxamine injection or infusion, in contrast, resulted in linear increases in the calculated total peripheral resistance and left and right atrial mean pressures. There was a simultaneous rise in right and left ventricular stroke works which were maintained until a maximum rise in the mean arterial pressure was reached. The average stroke volume indices were maintained at near control values in both blocked and unblocked animals. The cardiac index of the normal unblocked dogs decreased in proportion to the decrease in heart rate. Following the peak pressor response to methoxamine, a progressive fall in mean femoral arterial pressure occurred resulting from ventricular failure rather than "tachyphylaxis" to the vasoconstrictor activity of methoxamine. This decrease in systemic arterial pressure was accompanied by: (1) a further rise in calculated total peripheral resistance and in right and left atrial mean pressures, and (2) a fall in right and left ventricular stroke work and stroke volume indices and in the cardiac indices.

Physiologic differentation of pulmonic stenosis with and without an intact ventricular septum.

Since May 1957 cardiac catheterization has been carried out in 46 patients with pulmonic stenosis and an intact ventricular septum (pulmonic stenosis) and 42 patients with pulmonic stenosis and a right-to-left shunt through a septal defect (tetralogy of Fallot). Right atrial pressures were usually higher in pulmonic stenosis. Average pulmonary arterial and left atrial mean pressures were similar in the 2 groups, as were the pulmonary blood flows. Although significant differences between right ventricular and systemic arterial systolic pressures may be demonstrated in tetralogy of Fallot, simultaneous right ventricular and left ventricular or aortic systolic pressures were always within a few mm. Hg of each other. The postectopic right ventricular systolic pressure was always at least 10 mm. Hg above its previous level in pulmonic stenosis, whereas in tetralogy of Fallot it almost never exceeded its previous level by more than 10 mm. Hg. All patients with tetralogy of Fallot had flat-topped right ventricular pressure curves, whereas 31 of 46 patients with pulmonic stenosis had triangular right ventricular pressure curves. The phonocardiogram was found to be among the most useful tools in differentiating the 2 groups. Auscultatory phenomena of severe pulmonic stenosis with a widely split second heart sound, late crescendic diamond-shaped systolic murmur, and persistence of this murmur beyond the sound of aortic closure differed strongly from tetralogy of Fallot of equal severity. At cardiac catheterization proof of the presence of a ventricular septal defect may be gained by passing the catheter through it. If this is not done, the presence of a ventricular septal defect may be strongly inferred if the right ventricular pressure curve has almost parallel sides and a flat or rounded top, if the right ventricular systolic pressure is near that in the systemic circulation, and if it does not rise after ectopic beats more than 10 mm. Hg above its previous level. For greater certainty in diagnosis indicator-dilution curves or angiocardiography should be done. The accurate preoperative diagnosis of the presence or absence of a ventricular septal defect is extremely important, for at open-heart operation it is essential not to miss the ventricular septal defect after completely relieving the obstruction to right ventricular outflow; it is just as important not to do unnecessary right ventriculotomies.

Cardiopulmonary effects of pulmonary venous hypertension with special reference to pulmonary lymphatic flow.

Acute elevation of left atrial pressure could be precisely controlled at any desired level up to a mean of 60 mm. Hg in dogs with an intact thorax. The following observations were made in a series of 15 dogs. Right lymphatic duct flow did not increase at acutely elevated left atrial mean pressure below 25 mm. Hg, whereas flow increased 3- to 4-fold at mean pressure above 25 mm. Hg. The total amount of lymph at maximum flow, however, was only 0.3 ml./min. Lymph flow remained elevated for as long as 1 hour after left atrial pressure was restored to normal. Elevation of left atrial pressure did not affect lymph flow in the thoracic duct. Pulmonary edema did not occur readily at left atrial mean pressure elevated only slightly above plasma oncotic pressure. The production of pulmonary edema was observed only after a considerable elevation of left atrial pressure above plasma oncotic pressure was maintained for a period of one half hour or more in an otherwise normal dog. The hematocrit increased significantly after a 10-minute period of high left atrial pressure. Pulmonary vascular resistance decreased sharply as left atrial mean pressure was raised from 0 to 15 mm. Hg. The resistance gradually rose as left atrial pressure was raised to between 15 and 30 mm. Hg. Pulmonary arterial pressure uniformly rose and cardiac output uniformly declined with increasing left atrial pressure. Chronic elevation of left atrial pressure was achieved in 15 dogs. Left atrial mean pressure varied from 10 to 23 mm. Hg. These dogs were followed up to 10 months and the following observations were made. Right lymphatic duct flow did not increase at chronically elevated left atrial mean pressure below 25 mm. Hg. Flow was not studied at higher pressures since we were unable to sustain left atrial mean pressure above 25 mm. Hg in any dog in our chronic group. The animals that were brought to left atrial mean pressure between 30 and 40 mm. Hg and in whom these high levels were presumably maintained were found dead in their cages with pulmonary edema 1 to 2 days after tightening the snare. Many of the usual functional and structural changes often found in lungs of patients with mitral stenosis, except for hemosiderosis, were not observed in our experimental animals although the extent of the supravalvular stenosis produced was marked. Pulmonary arterial pressure rose slightly and cardiac output declined slightly. No change was noted in pulmonary vascular resistance. Ascites and other signs of right sided failure were not encountered.

The changes in right and left heart pressures during exercise and recovery in rheumatic heart disease

The variations in pulmonary artery mean pressure, pulmonary artery pulse pressure, right ventricular end-diastolic and left atrial mean pressures, and the mean diastolic left atrial-left ventricular gradients at rest, and during exercise and recovery have been analyzed. Several distinct patterns of change in these pressures have emerged. The reason for these patterns is not clearly understood. Several possibilities are proposed to explain the observed changes.

The phonocardiogram in mitral valvular disease: A correlation of Q-1 and 2-OS intervals with findings at catheterization of the left side of the heart and at mitral valvuloplasty

The intervals between the QRS of the electrocardiogram and the first heart sound (Q-1) and between the second heart sound and the opening snap (2-OS) have been correlated with operative findings and results of catheterization of the left side of the heart in forty-nine patients with mitral valvular disease. The Q-1 interval was usually prolonged (mean 0.07 seconds, standard deviation 0.01) but there was considerable overlap with the normal range (mean 0.05 seconds, standard deviation 0.02). There was poor correlation of the Q-1 with mitral valve size, left atrial mean pressure or end-diastolic pressure gradient across the mitral valve. An opening snap was demonstrable in thirty-one patients. Absence of an opening snap was usually associated with a heavily calcified immobile valve, with minimal mitral stenosis, or with the presence of predominant mitral regurgitation. There was significant correlation (r — 0.7) between the 2-OS interval and left atrial mean pressure, independent of the mitral valve size. The correlation with the mean diastolic pressure gradient across the mitral valve was considerably less (r — 0.4). The left atrial mean pressure or mean diastolic pressure gradient could not be predicted reliably from the 2-OS interval. Patients with combinations of mitral stenosis and regurgitation and appreciable mitral diastolic pressure gradients, showed Q-1 and 2-OS intervals indistinguishable from patients with pure mitral stenosis and similar pressure gradients. Patients with no diastolic pressure gradients across the mitral valve and, therefore, pure mitral insufficiency, had short Q-1 intervals, usually no opening snap and did not show variation of the Q-1 with the previous cycle length. With rare exceptions the Q-1 interval shortened and the 2-OS interval lengthened following successful mitral valvuloplasty. Usually the patients in whom this did not occur were not helped by surgery. It is concluded that the phonocardiogram may be a useful clinical adjunct in the evaluation of mitral valvular disease, but that its usefulness is limited. It is not a substitute for direct hemodynamic studies in patients who present difficult problems.

The interrelations of the pulmonary arterial and venous wedge pressures.

Pulmonary venous wedge pressure closely reflects the pulmonary arterial mean pressure. Pulmonary arterial wedge pressure is not significantly different from the left atrial mean pressure. Neither the former nor the latter is an approximation of the pulmonary capillary pressure.

Cardiac and pulmonary artery pressure pulses in experimental mitral stenosis

The response of pulmonary artery systolic and diastolic pressure to acute elevation of left atrial mean pressure has been explored in animals with an open chest. The elevation of pressure within the left atrium has been effected by the production of simulated mitral stenosis. Observations were made only in the presence of a well-maintained systemic pressure level and in the absence of observable myocardial ischemia. Under these conditions, pulmonary hypertension was uniformly observed throughout all levels of elevation of left atrial pressure. The individual responses of the pulmonary artery systolic and diastolic pressures have been detailed. The observation has been made that electrocardiographic evidence of severe myocardial hypoxia may develop in the absence of apparent mechanical constriction of the coronary circulation. In the presence of such myocardial hypoxia, decompensation of the right ventricle was observed and pulmonary hypertension was no longer maintained.

Pulmonary “capillary” pressure as an index of left atrial mean pressure in dogs

Pulmonary “capillary” pressure as an index of left atrial mean pressure in dogs