Comp iance of left atrium with and w thout left atrium appendage CORNELIUS A. DAVIS III, JUDITH C. REMBERT, AND JOSEPH C. GREENFIELD, JR. Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham 27710; and Cardiology Section, Medical Service, and Research Service, Veterans Administration Medical Center, Durham, North Carolina 27705
DAVIS III, CORNELIUS A., JUDITH C. REMBERT, AND JOSEPH C. GREENFIELD, JR. Compliance of left atrium with and without left atrium appendage. Am. J. Physiol. 259 (Heart Circ. Physiol. 28): H1006-H1008, 1990.-Compliance of the left atria1 chamber was estimated with and without the appendage intact in six isolated canine left atria. Pressure-volume determinations were measured over a range of 5-30 mmHg for the whole left atrium and were repeated with the appendage excluded. The slope of the pressure vs. normalized volume data for the left atrium without the appendage (10.45 t 0.87) was significantly greater (P < 0.01) than with the appendage intact (4.10 t 0.72). These data suggest that the left atria1 appendage is more compliant than the remaining left atrium. Assuming that this relationship remains in vivo, the left atria1 appendage may play an augmented role in maintaining hemodynamic function when filling pressures are elevated.
atria1 natriuretic
factor; atria1 function;
atria1 pressure-volume
of the cardiac atria has been investigated for centuries including the pioneering observations of William Harvey in 1628, “. . . blood enters the ventricles . . . by the beat of the auricles,” and “. . . they (the auricles) are filled as reservoirs” (8). The current understanding that the atria function as a reservoir of blood during ventricular systole, a passive conduit of blood during early ventricular diastole, and a contractile chamber during later ventricular diastole has been studied extensively (2, 6, 7, 15, 17). Investigations into the compliance of the atria have revealed an important relation to the atria1 function (1, 10, 19). Suga (19) utilizing an analog model noted that increasing the left atria1 compliance led to several desirable effects on cardiac hemodynamics, which culminated in an increase in cardiac output. Kihara et al. (10) noted that with induction of mitral regurgitation in dogs, the left atria adapted by becoming more compliant, by increasing reservoir function, and by enhancing active atria1 contraction. Other investigators have examined the compliance of the whole left atrium in both the normal and pathological states, but the possible differences in compliance of regions within the atria heretofore have not been evaluated. The left atria1 appendage is anatomically quite different from the rest of the atrium and hence may play a different hemodynamic role. This investigation was designed to measure the compliance of the left atrium with and without the appendage intact over a variety of filling pressures.
THE FUNCTION
METHODS
Complete studies were carried out in six isolated left atria obtained from adult mongrel dogs (19-27 kg) of both sexes. Anesthesia was induced with a 2% solution of thiamylal sodium (40 mg/kg) administered intravenously. The dogs were intubated, and respiration was maintained with a positive pressure Harvard respirator (NSH-34RH, model 615). All succeeding procedures were performed as expeditiously as was possible so that the pressure-volume data could be measured in as physiological a preparation as possible. A left thoracotomy through the fourth intercostal space was performed and the left pulmonary vein trunks were isolated and ligated. The animal was killed by rapid exsanguination, and the heart and lungs were removed en bloc. After the right ventricle and the left ventricular apex were trimmed away, the left atrium was isolated. The mitral valve was approached via the ventricular surface and the leaflets were sutured together forming a watertight seal with strips of pledget material and a continuous running suture of either 4-O or 6-O silk. Two polyvinyl chloride catheters utilized for pressure measurement and saline infusion were introduced into the left atrium along the atrioventricular groove and secured to be watertight. The remaining pulmonary vein trunks were ligated, and the atrium was filled with saline allowing all the air to escape from one vein before ligation. The lungs were removed, and the atrium was suspended inverted by the remaining ventricular free wall in a calibrated chamber containing normal saline into which the atrium was immersed. One catheter was connected to a Statham P23 Db pressure transducer. Pressures were recorded with a HewlettPackard 7758A direct-writing oscillograph. The atrium was inflated progressively in 5-mmHg increments through the remaining catheter with Evans blue-colored saline to ensure that an adequate seal had been obtained. The first series of inflations were made with the intact atrium, the second with the appendage clamped at its base using a flatjaw pinchcock, and finally a repetition of the first series was made to assure stability of the system. Data collection was initiated at an intraatria1 pressure of -2-5 mmHg and terminated after a pressure of -30 mmHg was obtained. Zero pressure was assumed to be at the midatrial level. The change in volume of the chamber was measured directly after each incremental infusion. The atrium was deemed to be adequately watertight if a pressure of 15 mmHg could be
H1006
Downloaded from www.physiology.org/journal/ajpheart by ${individualUser.givenNames} ${individualUser.surname} (163.015.154.053) on August 23, 2018. Copyright © 1990 American Physiological Society. All rights reserved.
LEFT
ATRIAL
maintained for >12 s with a
DAVIS III, CORNELIUS A., JUDITH C. REMBERT, AND JOSEPH C. GREENFIELD, JR. Compliance of left atrium with and without left atrium appendage. Am. J. Physiol. 259 (Heart Circ. Physiol. 28): H1006-H1008, 1990.-Compliance of the left atria1 chamber was estimated with and without the appendage intact in six isolated canine left atria. Pressure-volume determinations were measured over a range of 5-30 mmHg for the whole left atrium and were repeated with the appendage excluded. The slope of the pressure vs. normalized volume data for the left atrium without the appendage (10.45 t 0.87) was significantly greater (P < 0.01) than with the appendage intact (4.10 t 0.72). These data suggest that the left atria1 appendage is more compliant than the remaining left atrium. Assuming that this relationship remains in vivo, the left atria1 appendage may play an augmented role in maintaining hemodynamic function when filling pressures are elevated.
atria1 natriuretic
factor; atria1 function;
atria1 pressure-volume
of the cardiac atria has been investigated for centuries including the pioneering observations of William Harvey in 1628, “. . . blood enters the ventricles . . . by the beat of the auricles,” and “. . . they (the auricles) are filled as reservoirs” (8). The current understanding that the atria function as a reservoir of blood during ventricular systole, a passive conduit of blood during early ventricular diastole, and a contractile chamber during later ventricular diastole has been studied extensively (2, 6, 7, 15, 17). Investigations into the compliance of the atria have revealed an important relation to the atria1 function (1, 10, 19). Suga (19) utilizing an analog model noted that increasing the left atria1 compliance led to several desirable effects on cardiac hemodynamics, which culminated in an increase in cardiac output. Kihara et al. (10) noted that with induction of mitral regurgitation in dogs, the left atria adapted by becoming more compliant, by increasing reservoir function, and by enhancing active atria1 contraction. Other investigators have examined the compliance of the whole left atrium in both the normal and pathological states, but the possible differences in compliance of regions within the atria heretofore have not been evaluated. The left atria1 appendage is anatomically quite different from the rest of the atrium and hence may play a different hemodynamic role. This investigation was designed to measure the compliance of the left atrium with and without the appendage intact over a variety of filling pressures.
THE FUNCTION
METHODS
Complete studies were carried out in six isolated left atria obtained from adult mongrel dogs (19-27 kg) of both sexes. Anesthesia was induced with a 2% solution of thiamylal sodium (40 mg/kg) administered intravenously. The dogs were intubated, and respiration was maintained with a positive pressure Harvard respirator (NSH-34RH, model 615). All succeeding procedures were performed as expeditiously as was possible so that the pressure-volume data could be measured in as physiological a preparation as possible. A left thoracotomy through the fourth intercostal space was performed and the left pulmonary vein trunks were isolated and ligated. The animal was killed by rapid exsanguination, and the heart and lungs were removed en bloc. After the right ventricle and the left ventricular apex were trimmed away, the left atrium was isolated. The mitral valve was approached via the ventricular surface and the leaflets were sutured together forming a watertight seal with strips of pledget material and a continuous running suture of either 4-O or 6-O silk. Two polyvinyl chloride catheters utilized for pressure measurement and saline infusion were introduced into the left atrium along the atrioventricular groove and secured to be watertight. The remaining pulmonary vein trunks were ligated, and the atrium was filled with saline allowing all the air to escape from one vein before ligation. The lungs were removed, and the atrium was suspended inverted by the remaining ventricular free wall in a calibrated chamber containing normal saline into which the atrium was immersed. One catheter was connected to a Statham P23 Db pressure transducer. Pressures were recorded with a HewlettPackard 7758A direct-writing oscillograph. The atrium was inflated progressively in 5-mmHg increments through the remaining catheter with Evans blue-colored saline to ensure that an adequate seal had been obtained. The first series of inflations were made with the intact atrium, the second with the appendage clamped at its base using a flatjaw pinchcock, and finally a repetition of the first series was made to assure stability of the system. Data collection was initiated at an intraatria1 pressure of -2-5 mmHg and terminated after a pressure of -30 mmHg was obtained. Zero pressure was assumed to be at the midatrial level. The change in volume of the chamber was measured directly after each incremental infusion. The atrium was deemed to be adequately watertight if a pressure of 15 mmHg could be
H1006
Downloaded from www.physiology.org/journal/ajpheart by ${individualUser.givenNames} ${individualUser.surname} (163.015.154.053) on August 23, 2018. Copyright © 1990 American Physiological Society. All rights reserved.
LEFT
ATRIAL
maintained for >12 s with a
