Influence of altered loading conditions on left atrial appendage function in vivo

T left atrial (LA) appendage contracts both actively and passively throughout the cardiac cycles.1,2 Previous clinical and experimental data have shown that function of this structure depends on various factors including age,3 heart rate,1 and loading conditions.4–6 Moreover, it is reported that the LA appendage plays a pivotal role in maintaining normal cardiac status.7–9 No clinical studies have examined the influence of altered loading conditions on LA appendage function based on serial clinical, hemodynamic, and echocardiographic observations. In the present study, we performed right-sided cardiac catheterization, and transthoracic and transesophageal echocardiography in patients with left ventricular systolic dysfunction before and after treatment of heart failure, and examined the impact of altered loading conditions on LA appendage function, which related to hemodynamic and other echocardiographic indexes. • • • This study consisted of 10 patients (8 men; mean age 64 6 7 [SD] years, range 54 to 76) who were admitted to our institution presenting with symptoms related to overt heart failure. There were 7 patients with healed myocardial infarcts with depressed left ventricular systolic function and 3 patients with idiopathic dilated cardiomyopathy. Patients with atrial fibrillation and those with severe mitral regurgitation (grade III or IV) defined by color Doppler imaging were excluded. On admission, all patients had a mean pulmonary capillary wedge pressure $15 mm Hg. Treatment of heart failure was begun using digitalis, diuretics, angiotensin-converting enzyme inhibitors, positive inotropic agents, or a combination of these. This resulted in both symptomatic (functional class I or II) and hemodynamic (mean pulmonary capillary wedge pressure ,12 mm Hg) improvement. The mean period requiring improvement in heart failure was 106 6 (SD) days, range 3 to 20. Before beginning echocardiography, informed consent was obtained from all patients. With use of software provided in the echocardiographic machine (Toshiba SSH-140A [Toshiba Medical Co., Tokyo, Japan] [8 patients] and HewlettPackard SONOS 2500 [Andover, Massachusetts] [2 patients]), left ventricular end-diastolic and end-systolic volumes and ejection fraction were calculated from the apical 2-chamber views by the area-length method. LA volumes were measured at the onset of atrial systole (P wave of the electrocardiogram) and at the time of mitral valve closure (minimal) from the apical 2and 4-chamber views, and LA ejection fraction was calculated according to the area-length method.10 During LA volume measurement, LA areas at onset of atrial systole and mitral valve closure (minimal area) were also obtained. Immediately after the transthoracic method, transesophageal examinations were performed using 5-MHz multiplane transducers (model PEF-510MA, Toshiba Medical Co. [8 patients] and 21364A, Hewlett-Packard Co. [2 patients]). The echocardiographic probe was inserted into the esophagus under local pharyngeal anesthesia with the patient in the left lateral decubitus position. The LA appendage was visualized in the longitudinal view, and LA appendage flows were recorded with the pulsed Doppler method by placing the sample volume within 1 cm of the appendage outlet.4,5 LA appendage emptying and filling velocities during early and late ventricular diastole, respectively, were measured. In the same view, the LA appendage areas and percent area fraction were measured.4 Mitral flow velocities were obtained in the transverse view with the pulsed Doppler sample volume placed at the tips of the mitral leaflets. The early filling (E) and atrial filling (A) velocities and their ratio were determined. Pulmonary venous flow velocities were obtained with the sample volume placed 1 to 2 cm into the left upper pulmonary vein.4,5,11 Peak velocities of the atrial reversal, and those of the systolic and diastolic forward flow waves in the pulmonary vein were measured. For all measurements of Doppler variables, 3 consecutive beats were analyzed and averaged. A balloon-tipped pulmonary artery catheter was inserted into the right internal jugular vein and advanced to the pulmonary artery, where mean pulmonary capillary wedge pressure was recorded at end-expiration with the reference level at midchest and the value used as an index of the mean LA pressure. Values are expressed as mean 6 SD. Changes in hemodynamic and echocardiographic variables were assessed by paired t test. Unpaired t test was used to compare selected continuous variables. Univariate and stepwise multivariate analyses were performed to examine the possible relation of the late appendage emptying velocity, a representative of appendage function, to other echocardiographic From The Third Division, Department of Internal Medicine, Osaka Medical College, Takatsuki, Osaka, Japan. Dr. Suwa’s address is: Third Division, Department of Internal Medicine, Osaka Medical College, 2-7, Daigaku-cho, Takatsuki City, Osaka, 569-8686, Japan. Manuscript received October 10, 1997; revised manuscript received and accepted December 29, 1997.