Left Atrial Reservoir Volume Research Articles

Atrial Dysfunction in Significant Atrial Functional Mitral Regurgitation: Phenotypes and Prognostic Implications.

Atrial functional mitral regurgitation (AFMR) is associated with increased morbidity and mortality. Left atrial (LA) size and function in AFMR are poorly characterized. We aimed to assess LA function by reservoir strain (LASr) and estimated reservoir work (LAWr) and their impact on outcome in AFMR. Consecutive patients at our institution between 2001 and 2019 and with significant (moderate or greater) AFMR were examined. LAWr was estimated as LASr×LA reservoir volume, and patients were grouped by median LASr and LAWr. Outcomes were all-cause death or heart failure hospitalizations. Five hundred fifteen AFMR patients were followed up for 5 (1-17) years. Patients had previously documented atrial fibrillation (AF; 37%), heart failure with preserved ejection fraction (HFpEF) without AF (24%), or both (HFpEF+AF, 39%). LA volume was largest in AF, while LA function parameters were most impaired in the combined HFpEF+AF group. During follow-up, patients with low LASr or LAWr had higher risk of death (P<0.001) and heart failure hospitalization (P<0.05). In Cox regression analyses, low LASr and LAWr, but not LA volume or left ventricular function, were associated with a higher risk of death (LASr: hazard ratio, 2.3 [95% CI, 1.6-3.5]; LAWr: hazard ratio, 3.4 [95% CI, 2.4-4.9]; both P<0.001) after adjustment for clinical and echocardiographic confounders. Low LASr and LAWr were strongest associated with death in HFpEF and HFpEF+AF. LA reservoir function but not LA size is a robust predictor of outcome in significant AFMR. This provides mechanistic insights into the interplay of functional versus geometric LA changes in AFMR.

The Role of Advanced Echocardiographic Parameters of the Left Atrial Function in the Incidence of Cryptogenic Ischemic Stroke: A Review.

Stroke is one of the primary causes of morbidity and mortality worldwide, including a large proportion of cryptogenic strokes. Long-term electrocardiographic monitoring is beneficial in prospective studies for detecting atrial fibrillation in patients with cryptogenic stroke. This review aimed to evaluate the advanced echocardiographic parameters and their roles in assessing left atrial (LA) function in the incidence of cryptogenic and ischemic strokes. Main resources, including PubMed, Scopus, and ISI Web of Science databases, were evaluated for articles published in English from 2010 until May 2021. LA echocardiographic parameters such as LA strain and strain rate, isovolumetric relaxation time (IVRT), the mean left atrial volume index (LAVI), LA reservoir volume, systole strain rate (SSR) of left atrial appendage, and lack of LA function response to maximal exercise as measured by the LA ejection fraction during rest and exercise could be considered for assessing the risk of cryptogenic strokes and ischemic strokes. The results indicated that increased LA volumes and reduced LA strain rate were correlated with cryptogenic stroke. Advanced parameters of LA function, measured by speckle tracking echocardiography, such as strain and strain rate values in different parts of the cardiac cycle, in addition to standard measures of LA function such as LA ejection fraction and LAVI, will define an excellent understanding regarding LA myopathy and risk assessment of cryptogenic stroke, independent of considering conventional cardiovascular risk factors.

Abstract 11216: Greater Prognostic Value of Left Atrial Mechanics Compared to Left Atrial Volume in Atrial Functional Mitral Regurgitation

Introduction: Atrial functional mitral regurgitation (AFMR) is associated with increased mortality and morbidity. Optimal management however remains unclear. Mechanism of AFMR is linked to left atrial remodeling yet left atrial (LA) size and function are still poorly characterized. Objectives: To assess LA size and function by reservoir strain (LASr) and reservoir work (LAWr) and their impact on outcome in AFMR. Methods: Consecutive patients examined at our institution between 2001-2019 and with AFMR of at least moderate MR degree were examined. LAWr was estimated as LASr x LA reservoir volume, and patients were grouped by median LASr or LAWr. Outcomes were all-cause death or heart failure hospitalizations. Results: 515 patients with moderate or greater AFMR were followed for a median of 5 [range 1-17] years. All patients had previously documented atrial fibrillation (AF) (38%), heart failure with preserved ejection fraction (HFpEF) without AF (24%), or both (HFpEF+AF, 38%). LA volume was largest in AF patients and smallest in HFpEF while LA function parameters were greater in HFpEF and AF compared to the combined HFpEF+AF group (Fig. A,B).During follow-up, patients with low LASr or LAWr had higher risk of death (p &lt;0.001, Fig. C) and heart failure hospitalizations (p&lt;0.05). In Cox regression analyses, low LASr and LAWr, but not LA volume and left ventricular function, were associated with a higher risk of death (LASr: HR 2.3 (95% CI 1.6-3.5); LAWr HR 3.4 (95% CI 2.4-4.7), both p&lt;0.001) after adjustment for clinical and echocardiographic confounders. Conclusion: LA reservoir function but not LA size is a robust predictor of outcome in AFMR with moderate or greater MR. This provides mechanistic insights into the interplay of functional parameters versus LA geometric changes in AFMR.

Dynamic changes of left atrial function during supine ergometry: evidence for interplay with left ventricular function and dynamic changes of pulmonary pressure

Abstract Introduction Despite the pivotal role of left atrial (LA) function in a variety of cardiac pathologies, it has been studied mainly at rest. Aim Aim of the study was to assess the effect of semisupine exercise ergometry (Ex) on LA function, by volumetric and strain parameters and to interrogate relationships with left ventricular (LV) function and noninvasive hemodynamics. Patients and methods Eighty-two patients (female 26, age: mean/SD 61/15) referred for Ex were studied. The following parameters were estimated by 2 D echo: LV systolic (LVvolsyst) and diastolic (LVvoldiast) volume, ejection fraction (LVEF), stroke volume (LVsv), LA minimum (LAvolmin) and maximal volume (LAvolmax), LA emptying fraction [LAEF), LA reservoir volume (LAvolres = LAvolmax − LAvolmin), LA reservoir fraction (LAresFR = LAvolres/LVsv), LA conduit volume (LAcondvol = LVsv − LAvolres) and LA conduit fraction (LAcondFR = LAcondvol/LVsv). LV strain (LVSR) and LA strain (LASR) were estimated by 2D analysis. Peak tricuspid gradient (TRpg) was also estimated. Parameters were measured at rest R and Ex and the respective % changes (%d) were calculated. Results SBE performance was efficient with a % achieved target heart rate 73/9 and workload Watts 96/21. Systolic blood pressure increased from 139/53 to 179/31. Parameters with significant change during Ex are in the table (all p&amp;lt;0.001). LVSRr and LVEFr were both related inversely with LAvolresR (r=−0.39/p=0.001 and r=−0.24/p=0.05) and LAresFRr (r=−0.34/p=0.001 and r=−0.25/p=0.04). LVEFr was related inversely with LAcondRFr r=−0.24/p=0.04). LVSR was related inversely with LAvolresEx (r=−0.43/p=0.001). LVSREx was related inversely with LAvolresR (r=−0.24/p=0.04) and LAcondRFr (r=−0.25/p=0.04). The %dLVSR was related inversely with LAEFr (r=−0.25/p=0.04). The %dLVEF was related inversely with LAresFREx (r=−0.27/p=0.03) and LAcondRFr (r=−0.27/p=0.03). The % increase in TRpg during SBE was positively related with LAresFREx r=0.30/p=0.04 and inversely with LAcondFREx (r=−0.30/p=0.04) (Figure 1). Conclusion SBE induces LA dynamic changes in a spectrum of volumetric and strain indices. Dynamic changes of LV are related with reservoir and conduit LA function. LA reservoir and conduit function during SBE are related with the induced dynamic changes of pulmonary pressure, thus further supporting the clinical relevance of the respective evaluation. Funding Acknowledgement Type of funding sources: None.

Importance of left ventricular contraction for left atrial reservoir function.

The determinants of left atrial (LA) reservoir function have not been clarified. To elucidate the effect of left ventricular (LV) contraction on LA reservoir volume (ΔVLA), volume change due to mitral annular downward motion and aortic root anterior motion, which are related to LV contraction during systole, was calculated in 72 consecutive subjects [42 patients without any cardiac disease (control group), 13 patients with heart failure with reduced ejection fraction (HFrEF group) and 17 with preserved ejection fraction (HFpEF group)]. LA volume was calculated using the modified Simpson's method of bi-plane 2-D echocardiograms. ΔVLA was the difference between the maximum and minimum LA volumes. LA volume change according to mitral annular motion (ΔVMA) and aortic root motion (ΔVAR) were calculated by assuming an oval frustum and dented wedge, respectively. In the normal control group, ΔVAR + ΔVMA was 11.7ml on average, correlating to ΔVLA (r = 0.55, p < 0.01), and the contribution rate to LA reservoir volume ((ΔVAR + ΔVMA)/ΔVLA) was 56% on average. In both, the HFrEF and HFpEF groups, ΔVAR, ΔVMA, and the contribution rate were significantly smaller than those in normal control group. Stroke volume correlated to ΔVAR and ΔVMA. The larger the maximum LA volume was, the smaller the contribution rate was. The smaller the rate was, the higher the systolic pulmonary artery pressure was. Both mitral annular motion and aortic root anterior motion, which are related to ventricular contraction, are important for the LA reservoir volume recruitment.

Exercise physiology of the left atrium: quantity and timing of contribution to cardiac output.

Although the phases of left atrial (LA) function at rest have been studied, the physiological response of the LA to exercise is undefined. This study defines the exercise behavior of the normal left atrium by quantitating its volumetric response to graded effort. Healthy subjects (n = 131) were enrolled from the Health eHeart cohort. Echocardiograms were obtained at baseline and during ramped supine bicycle exercise. Left ventricular volume index, stroke volume index (LVSVI), left atrial end-systolic volume index (LAESVI), left atrial end-diastolic volume index (LAEDVI), and left atrial emptying fraction (LAEF), reservoir fraction, and conduit fraction were analyzed. The LVSVI increased with low exercise but did not increase further with peak exercise; cardiac output increased through the agency of heart rate. The LAESVI and LAEDVI decreased and the LAEF increased with exercise. As a result, the LA reservoir volume index was static throughout exercise. The reservoir fraction decreased from 46% at rest to 40% with low exercise (P < 0.001) in association with increased LVSVI and remained similar at peak exercise. The conduit volume index increased from 20 mL/m2 at rest to 24 mL/m2 at low exercise and stayed the same at peak exercise. Similarly, the conduit fraction increased from 54% at rest to 60% at low exercise (P < 0.001) and did not change further with peak exercise. Although atrial function increased with exercise, the major contribution to the augmentation of LV stroke volume is LA conduit fraction, a marker of active ventricular relaxation. Furthermore, the major determinant of raising cardiac output during high-level exercise is heart rate.NEW & NOTEWORTHY Diseases of the left atrium (LA) are major sources of disability (e.g., strokes and fatigue), but its exercise physiology has been unstudied. Such knowledge may allow early recognition of disease and suggest therapies. We show that in normal subjects, low-level exercise decreases LA volume and increases its ejection fraction. However, these changes offset each other volumetrically, and the contribution to LV filling from a full to an empty LA (reservoir function) is static. Higher levels of exercise do not change LA reservoir contribution. Blood flowing directly from the pulmonary vein to LV (conduit flow) impelled by augmented LV active relaxation (suction) is the major source of a modest increase in LV stroke volume. The major source of increased cardiac output with exercise is heart rate. During all stages of exercise, the LA works hard but only to keep up. We believe that our findings provide an additional set of benchmarks through which to quantitate LA pathology and gauge its progression.

Associations of left atrial volumes and Doppler filling indices with left atrial function in acute myocardial infarction.

SummaryRecent findings suggest that left atrial (LA) function is more strongly related to adverse prognosis than LA volumes. We aimed to evaluate the associations between LA volumes and Doppler filling indices with LA function. Echocardiographic LA volumes (LAVs), mitral valve early (MV‐E) and late (MV‐A) peak flow velocities, and mitral atrioventricular plane tissue‐Doppler early (TD‐e′) and late (TD‐a′) peak velocities were obtained in 320 patients with acute myocardial infarction (AMI) free from atrial fibrillation and more than moderate valvular disease. LA function was estimated as the LA emptying fraction (LAEF), that is 100× (LAVmax‐LAVmin)/LAVmax. LA reservoir volume was calculated as LAVmax‐LAVmin and LA transit volume as LV stroke volume‐reservoir volume. In restricted cubic spline regression analyses with multivariable adjustment, a reduced LAEF was strongly associated with smaller reservoir volume, larger transit volume, LAVmax, LAVpreA and especially LAVmin. MV‐E linearly increased with a lower LAEF, whereas MV‐A decreased but only below LAEF levels of approximately 45%. The resulting E/A ratio showed a sudden increase in LAEF levels below ~45%. Lower TD‐a′ was linearly associated with a lower LAEF. In conclusion, a reduced atrial function was associated with smaller LA reservoir volume, larger LA transit volume, lower TD‐a′, a non‐linear decrease in MV‐A and a non‐linear increase in E/A. Our findings are likely a reflection of the adaptation to sustain LV filling volume and counteracting a rise in pulmonary venous pressure in face of an enhanced LV end‐diastolic pressure.

Evaluation of left atrial function in patients with severe preeclampsia by full-volume imaging technology

Objective To evaluate the left atrial(LA) function in patients with severe preeclampsia(SPE) by full-volume imaging technology. Methods Forty-two patients of SPE were randomly chosen as SPE group, 34 healthy pregnant women were selected as the control group. LA related function parameters including LA maximum volume(LAVmax), LA minimum volume(LAVmin), LA pre-atrium contraction volume(LAVpre), LA reservoir volume(LARV), LA passive emptying volume(LAPEV), LA contraction volume(LACV), LA expansion index(LAEI), LA passive emptying fraction(LAPEF), LA passive emptying fraction(LAAEF) were separately required by biplane area-length method and full-volume imaging technology in antepartum and postpartum. Results Compared with control group before delivery, the parameters of SPE group before delivery such as LAVmax, LAVmin, LAVpre were higher, LAEI, LAPEF, LAAEF indexed to body surface area(BSA) were lower(all P 0.05). Compared with SPE group before delivery, the parameters of SPE group after delivery such as LAVmax, LAVmin, LAVpre were lower, LAEI, LAPEF, LAAEF indexed to BSA were higher(all P 0.05). Conclusions Full-volume imaging technology can quantitatively evaluate the LA function. LA reservoir function, conduit function and booster pump function are reduced in SPE before delivery, LA rereservoir function, conduit function and booster pump function are basically recovery in SPE after delivery. Key words: Echocardiography; Pre-eclampsia; Atrial function, left; Full-volume imaging technology

Association of left atrial phasic volumes with systemic arterial stiffness and ankle-brachial index in hypertensive patients.

Left atrial (LA) phasic volumes consist of reservoir, conduit and booster pump volumes. Arterial stiffness is linked to lower systemic arterial compliance (SAC) contributing to cardiac afterload. Arterial stiffness may be a modulator of LA phasic volumes. Echocardiography was performed in 161 hypertensive patients and in 50 normotensive subjects in order to assess biplane LA volumes (maximum, before atrial contraction, minimum), early and late diastolic mitral annular velocity (e' and a'), and LV stroke volume. LA emptying volumes (total, passive, active) were calculated from these LA volumes. Blood pressures were measured using an automated oscillometric device simultaneously at the four limbs for evaluating pulse pressure (PP) and ankle-brachial index (ABI). SAC was estimated by the ratio of LV stroke volume indexed by body surface area (BSA) divided by PP. All three LA volumes, LA total volume and LA active emptying volume were greater in hypertensive patients than in normotensive subjects. A multiple linear regression analysis indicated that LA passive emptying volume (reservoir=early diastole)/BSA correlated positively with ABI after being adjusted for age, gender, BSA, LV mass, max LA volume, e' and SAC in hypertensive patients. LA active emptying volume (booster=late diastole)/BSA correlated positively with SAC after being adjusted for age, gender, BSA, LV mass, LA volume before atrial contraction, a' and ABI. LA reservoir volume was associated with ABI, and LA booster volume was related to systemic arterial stiffness in hypertensive patients, suggesting the LA-arterial coupling in this clinical setting.

The impact of 6 weeks of atrial fibrillation on left atrial and ventricular structure and function

ObjectiveThe impact of prolonged episodes of atrial fibrillation on atrial and ventricular function has been incompletely characterized. The purpose of this study was to investigate the influence of atrial fibrillation on left atrial and ventricular function in a rapid paced porcine model of atrial fibrillation. MethodsA control group of pigs (group 1, n = 8) underwent left atrial and left ventricular conductance catheter studies and fibrosis analysis. A second group (group 2, n = 8) received a baseline cardiac magnetic resonance imaging to characterize left atrial and left ventricular function. The atria were rapidly paced into atrial fibrillation for 6 weeks followed by cardioversion and cardiac magnetic resonance imaging. ResultsAfter 6 weeks of atrial fibrillation, left atrial contractility defined by atrial end-systolic pressure-volume relationship slope was significantly lower in group 2 than in group 1 (1.1 ± 0.5 vs 1.7 ± 1.0; P = .041), whereas compliance from the end-diastolic pressure-volume relationship was unchanged (1.5 ± 0.9 vs 1.6 ± 1.3; P = .733). Compared with baseline, atrial fibrillation resulted in a significantly higher contribution of left atrial reservoir volume to stroke volume (32% vs 17%; P = .005) and lower left atrial booster pump volume contribution to stroke volume (19% vs 28%; P = .029). Atrial fibrillation also significantly increased maximum left atrial volume (206 ± 41 mL vs 90 ± 21 mL; P < .001). Left atrial fibrosis in group 2 was significantly higher than in group 1. Atrial fibrillation decreased left ventricular ejection fraction (29% ± 9% vs 58 ± 8%; P < .001), but left ventricular stroke volume was unchanged. ConclusionsIn a chronic model of atrial fibrillation, the left atrium demonstrated significant structural remodeling and decreased contractility. These data suggest that early intervention in patients with persistent atrial fibrillation might mitigate against adverse atrial and ventricular structural remodeling.

Assessment of left atrial appendage function during sinus rhythm in patients with obstructive sleep apnea.

Objective:Obstructive sleep apnea (OSA) is associated with thromboembolic events. Compromised left atrial appendage (LAA) function due to left ventricular (LV) performance abnormality, often present in patients with OSA, may play an important role. The purpose of this study is to evaluate LV and LAA mechanical functions during sinus rhythm (SR) in patients with OSA.Methods:LV and LAA functions were assessed in 43 OSA patients and compared with that of 20 control patients in SR. Tissue Doppler velocities of the LAA apex and emptying velocities (EV) of LAA were obtained on parasternal short-axis view.Results:The baseline clinical characteristics were similar except for AHI (apnea-hypopnea index), minimal SaO2, mean SaO2, hypertension, and body-surface area. Most of the LV echocardiographic parameters significantly deteriorated in OSA patients in comparison with those in the control group. LAA EV, LAA systolic relaxation velocity (SM), LAA early-diastolic velocity (EM), LAA contraction velocity (AM), left atrial (LA) minimum volume index, LA ejection fraction, LA conduit volume index, and LA reservoir volume index were lower in OSA patients compared with those in the control group (p<0.05). LAA AM was negatively correlated with AHI and the ratio of peak early diastolic flow velocity (E) to early-diastolic (E’) and positively correlated with LA conduit volume (p<0.05). Multiple predictors for LAA AM were AHI, presence of diastolic dysfunction, and E/E’ values (p<0.05).Conclusion:LAA mechanical function is significantly depressed in patients with OSA and SR. LAA dysfunction may predispose these patients to thromboembolic events. The evaluation of LAA mechanical function by tissue Doppler study using transthoracic echocardiography (TTE) may become an alternative for routine work-up in OSA patients.

Assessing the left atrial phasic volume and function with dual-source CT: comparison with 3T MRI

We wanted to assess the performance of dual-source CT (DSCT) for evaluating the left atrial volume and function and we compared this performance to that of the standard reference technique,cardiac cine MR (CMR). Fifty-one patients who were referred for CT coronary angiography were included in the study. Two were subsequently excluded for having un-analyzable MR images at the onset of left atrial contraction. For the remaining 49 patients, the DSCT data sets and FIESTA (fast imaging employing steady-state acquisition) cines of the vertical long axis covering the left atrium and the short axis covering the left ventricle were obtained on the same day. All the images were analyzed to obtain the maximal left atrial volume (LAVmax), the minimal left atrial volume (LAVmin), the left atrial volume just before left atrium contraction (LAVp), the left atrial reservoir volume (LARV), the left atrial ejection fraction (LAEF), the left atrial passive emptying volume (LAPV), the left atrial active emptying volume(LAAV), the left atrial conduit volume (LACV), the left ventricular end-diastolic volume (LVEDV), the left ventricular end-systolic volume (LVESV) and the left ventricular stroke volume (LVSV) by using 3D semi-segmentation software and Report Card 2.0 software, respectively, for the DSCT and CMR. All the parameters were normalized to the body surface area. Intermodality agreement was tested through linear regression and Bland-Altman analyses.Repeated measurements were performed to determine the interobserver variability. The DSCT measurements resulted in good correlation (r > 0.75) compared with those of CMR. However, DSCT slightly,but insignificantly overestimated the indexed LAVmax, LAVmin, LAVp, LARV, LAPV, LAAV and LACV, as reflected by biases of 1.2, 0.9, 1.1, 0.3, 0.1,0.2 and 0.4 ml/m(2), respectively. The LAEF was minimally, but insignificantly underestimated as reflected by a bias of -0.6% (P = ns). The variability of the DSCT measurements was lower than that of the CMR values. DSCT provides highly reliable and reproducible measurements of the left atrial phasic volume and function in patients who are referred for coronary CT imaging.

Effects of volume loading on pulmonary venous flow pattern in dogs with normal left ventricular function.

The effects of altered loading conditions on the pattern of pulmonary venous flow are poorly understood. The authors investigated such effects, therefore, by using volume loading in 6 open-chest dogs. The pulmonary venous flow volume rate curve was obtained with a transit-time ultrasonic flowmeter at a fixed heart rate. Measurements were performed in the control and several states during the intravenous infusion of dextran. The influences of volume loading on hemodynamic and pulmonary venous flow variables were compared between the control state and three interventional states in which mean left atrial pressure was approximately 1, 2, and 3 mm Hg above the control value. The systolic flow volume (SI), which corresponds to left atrial reservoir volume, significantly increased, but the early diastolic flow volume (DI), which corresponds to left atrial conduit volume, did not show significant change with volume loading. The flow volume during left atrial contraction significantly increased with volume loading. The flow volume during one cardiac cycle (PVF) significantly increased with volume loading. Approximately 73% of increased PVF was distributed to the systolic flow. The rest was distributed to the early diastolic flow (14%) and to the flow during left atrial contraction (12%). The change in the ratio of SI/DI significantly and positively correlated with the change in mean left atrial pressure (r = 0.87, P < 0.001). These findings indicate that increased pulmonary venous flow induced by volume loading in dogs with normal left ventricular function is mainly distributed to the left atrial reservoir volume.

Altered left atrial compliance after atrial appendectomy. Influence on left atrial and ventricular filling.

Previous studies have shown regional differences in atrial distensibility. We studied 12 open-chest dogs to test the hypothesis that left atrial compliance is decreased after removal of the left atrial appendage and to determine the effect of altered atrial compliance on atrial reservoir and conduit function. Sonomicrometer crystal pairs were used to measure the long- and short-axis diameters of the left atrium over a wide range of intracardiac pressures and volumes obtained by intravenous hetastarch infusion both before and after suture ligation of the left atrial appendage (appendectomy). Pulmonary venous flow was measured with an ultrasonic flowmeter, and transmitral flow velocities were measured with transesophageal Doppler echocardiography. After appendectomy, the diastolic pressure-volume relation was shifted upward and to the left in six of seven dogs. The mean dynamic stiffness constant of the left atrial diastolic pressure-volume relation was significantly greater after appendectomy than before (0.20 +/- 0.11 [mean +/- SD] versus 0.14 +/- 0.08 ml-1, p < 0.01); the mean y intercept was slightly, but significantly, less after appendectomy (0.6 +/- 0.3 versus 1.3 +/- 0.6 mm Hg, p < 0.05). The left atrial reservoir volume (maximum minus minimum left atrial volume) was significantly less after appendectomy at matched left atrial pressures. The systolic to diastolic flow integral ratio of pulmonary venous flow (JFTI/KFTI), an index of the relative reservoir to conduit functions of the left atrium, increased significantly with volume infusion only before appendectomy; at matched left atrial pressure, JFTI/KFTI was significantly less afterwards.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased left atrial chamber stiffness in hypertrophic cardiomyopathy.

To investigate left atrial chamber stiffness and its influence on left atrial and left ventricular functions in hypertrophic cardiomyopathy. Prospective study. Department of internal medicine in a university teaching hospital. Five control subjects, six patients with essential hypertension, and 11 patients with hypertrophic cardiomyopathy. Measurement of left atrial pressure by a tip micromanometer and of real-time left atrial volume from left atrial cineangiograms. Left atrial stiffness constant determined by fitting the ascending limb of the v loop of the left atrial pressure-volume relation to an exponential curve. The mean (SD) left atrial chamber stiffness constant was significantly larger in patients with hypertrophic cardiomyopathy than in controls (0.063 (0.018) v 0.041 (0.006), p < 0.05) and was correlated with left ventricular wall thickness (r = 0.560, p < 0.01). Left atrial reservoir volume (left atrial emptying volume before atrial contraction) was significantly smaller in patients with hypertrophic cardiomyopathy than in the controls (7.3 (2.1) v 12.5 (4.4) ml/m2, p < 0.01) and was inversely correlated with the left atrial chamber stiffness constant (r = -0.598, p < 0.01). The cardiac index was inversely correlated with the left atrial chamber stiffness constant (r = -0.542, p < 0.01). Left atrial chamber stiffness was increased in patients with hypertrophic cardiomyopathy and this affected the left atrial reservoir function. This may in turn have affected cardiac output.