Hemodynamics of experimental acute aortic insufficiency; with observations on modifications resulting from ballvalue prostheses

Beneficial effect of atrial pacing in severe acute aortic regurgitation and role of M-mode echocardiography in determining the optimal pacing interval

The effect of atrial pacing on cardiac performance was assessed in 11 men (aged 20 to 64 years) with recent-onset severe aortic regurgitation (AR), all of whom had diastolic closure of the mitral valve on the echocardiogram. Thermodilution cardiac outputs were determined, and aortic, left ventricular and pulmonary arterial wedge pressures recorded. Once baseline recordings were completed, the pacing rate was increased by increments of 10 beats/min (70, 80, 90...) to a maximal rate of 140 beats/min. The optimal pacing interval, obtained from hemodynamic data, was defined as that at which the lowest filling pressure was associated with the highest cardiac index. This was then compared with a pacing interval derived from the R wave of the electrocardiogram to the diastolic mitral closing point on the M-mode echocardiogram. Such an interval would shorten diastole without affecting forward mitral flow. Atrial pacing improved the overall hemodynamic state in all patients; the most favorable hemodynamics were achieved at heart rates between 110 and 130 beats/min (mean: 120 +/- 8). At the optimal rate, left ventricular end-diastolic pressure decreased from 46 +/- 7 to 23 +/- 12 mm Hg (p less than 0.001), and the pulmonary arterial wedge pressure from 28 +/- 8 to 16 +/- 7 mm Hg (p less than 0.001), while the cardiac index increased from 2.34 +/- 0.46 to 2.63 +/- 0.49 liters/min/m2 (p less than 0.01). The mean difference between the optimal pacing interval determined from the hemodynamic data and the interval derived from the echocardiogram was 18 +/- 21 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

A temporary catheter-tip aortic valve: hemodynamic effects on experimental acute aortic insufficiency

A catheter-mounted polyurethane cusp was designed to act as a temporary prosthetic aortic valve in the ascending aorta. Acute aortic insufficiency was created in 15 dogs by transventricular tearing of the two aortic valve leaflets with a wire hook. Hemodynamic variables were measured during aortic insufficiency and with the prosthetic valve in place. Comparison of the values showed that the prosthesis functioned as a competent aortic valve. Aortic diastolic pressure increased by 62 +/- 42%, pulse pressure was lowered by 44 +/- 9%, and left ventricular end-diastolic pressure decreased by 45 +/- 18%. Neither cardiac output, coronary blood flow, nor peak systolic pressure was significantly altered. The observed hemodynamic improvement and the simplicity of the design and application suggest that the prosthetic aortic valve may be applicable in the temporary treatment of decompensated aortic insufficiency.

Echocardiographic evaluation of the hemodynamic effects of chronic aortic insufficiency with observations on left ventricular performance

Twelve patients with aortic insufficiency (AI) were investigated by echocardiographic methods using reflected ultrasound. No patients with associated mitral valvular disease were included. Estimates of each patient's aortic valvular total flow (Q At ) as computed from left ventricular cavity minor-axis dimension changes at end-diastole (D d ) and end-systole (D s ) were compared with their respective mitral valvular flows (Q M ) as estimated from the opening velocity of the anterior mitral leaflet. The arithmetic difference of the two valvular flows permitted calculation of the aortic regurgitant flow (Q Ar ) as Q At -Q M =Q Ar . In this series of patients Q At varied from 5.2 to 12.9 liters/min, Q M from 3.3 to 7.3 liters/min, Q Ar from 1.1 to 6.5 liters/min, ejection fraction (EF) from 0.37 to 0.60 and regurgitant fraction (Q Ar /Q At ) from 0.15 to 0.58. A statistically significant difference of Q At and Q M was not evident in a series of 20 patients without AI.

Left ventricular performance in the patients with AI was estimated by echocardiographic methods by measuring the amplitude of systolic excursion of the left ventricular midwall (PWE), the mean velocity of posterior wall motion (mean PWV), and computation of the mean velocity of circumferential fiber shortening (V CF ) for the left ventricular myocardium.

The data presented appear to provide a simple noninvasive method for serial observations of the hemodynamic consequences of AI and the eventual alteration of myocardial performance in such patients.

Direct determinations of aortic blood flow in patients with aortic regurgitation. Effects of alterations in heart rate, increased ventricular preload or afterload, and isoproterenol

Instantaneous ascending aortic blood flow and left ventricular and central aortic pressure were determined at the time of operation in nine patients with severe aortic regurgitation. In six, the heart rate was controlled and increased by electrical stimulation between 50 and 170 beats/min. The relative duration of diastole decreased, and that of systole increased at faster heart rates. The mean systolic ejection rate fell, and regurgitant flow rates remained relatively constant. Thus, the per cent regurgitation was not reduced at faster rates. Following isoproterenol administration, the faster heart rate lengthened the relative duration of systole, abbreviated that of diastole, and increased the systolic ejection rate. Net result was an increased total forward flow and a reduced per cent regurgitation, but when the heart rate was held constant, the total forward stroke volume was ejected more rapidly, but the total forward and regurgitant flows per beat and per minute, and consequently the per cent regurgitation did not change. Assessments of left venticular function also were made in two patients.