Effect of left ventricular contractile performance on passive left atrial filling--clinical study using radionuclide angiography

Significant dependency of left atrial strain on left ventricular longitudinal motion

BACKGROUND

The effects of left ventricular longitudinal function on the left atrial strain, including the left atrial reservoir function, have not been adequately quantified.

METHODS

A total of 124 patients who underwent echocardiography were enrolled in this study. Left atrial strain analysis was performed using two-dimensional speckle tracking echocardiography, and the left atrial volume was derived using the modified Simpson's method. The peak left atrial strain (LAS) and left atrial expansion index (LAEI), as indices of left atrial reservoir function, were measured. The global longitudinal strain (GLS) and mitral annular plane systolic excursion (MAPSE), which are indices of contractile motion toward the left ventricular apex, were also measured. The correlation between LAS and candidate determinants, including left ventricular systolic longitudinal function, was evaluated, and multivariate regression analysis was performed.

RESULTS

A significant correlation was found between LAS and left ventricular systolic longitudinal functions, GLS (r = 0.63, p < 0.001), and MAPSE (r = 0.65, p < 0.001). Two models, which were selected by multiple regression analyses for LAS, included GLS or MAPSE as independent determinants. GLS and MAPSE were also the strongest predictors, among other factors.

CONCLUSION

LAS, when determined by evaluating the left atrial reservoir function, was significantly associated with left ventricular function, especially the systolic longitudinal function. Left ventricular function should be considered when assessing left atrial function by LAS.

Importance of left ventricular contraction for left atrial reservoir function

BACKGROUND

The determinants of left atrial (LA) reservoir function have not been clarified.

METHODS

To elucidate the effect of left ventricular (LV) contraction on LA reservoir volume (ΔV_LA), 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. ΔV_LA was the difference between the maximum and minimum LA volumes. LA volume change according to mitral annular motion (ΔV_MA) and aortic root motion (ΔV_AR) were calculated by assuming an oval frustum and dented wedge, respectively.

RESULTS

In the normal control group, ΔV_AR + ΔV_MA was 11.7 ml on average, correlating to ΔV_LA (r = 0.55, p < 0.01), and the contribution rate to LA reservoir volume ((ΔV_AR + ΔV_MA)/ΔV_LA) was 56% on average. In both, the HFrEF and HFpEF groups, ΔV_AR, ΔV_MA, and the contribution rate were significantly smaller than those in normal control group. Stroke volume correlated to ΔV_AR and ΔV_MA. 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.

CONCLUSIONS

Both mitral annular motion and aortic root anterior motion, which are related to ventricular contraction, are important for the LA reservoir volume recruitment.

Hemodynamic function of the right ventricular-pulmonary vascular-left atrial unit: normal responses to exercise in healthy adults

With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment, which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardiopulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms that modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the two-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardiopulmonary differences. Studying the determinants and recognizing the normal limits of PV pressure-flow relations during exercise will improve our understanding of cardiopulmonary mechanisms that facilitate or limit exercise.

Independent parameters of left atrium function in hypertensive heart disease

BACKGROUND

The left atrium reservoir function has an important role in the global cardiac performance and is determined by multiple cardiac and extra-cardiac factors. A new parameter is introduced, the independent strain, which quantifies left atrium reservoir phase deformation during isovolumetric relaxation.

AIMS

Is evaluated whether independent strain can identify intrinsic atrial myocardial damage in hypertension.

MATERIAL AND METHODS

Prospective observational study in which echocardiography was done to 50 hypertensive patients and 80 healthy volunteers. Myocardial deformation was evaluated with two-dimensional speckle tracking and left atrium volumes were calculated whit 3D-echocardiography.

RESULTS

In hypertensive patients, the indexed left atrium volume was greater than in the control group (34 ± 7.8 vs 24 ± 4.9 mL/m² ); strain of pump (-5.7 ± 2.4% vs -17±3.5%) and reservoir phases (34 ± 9% vs 48 ± 10%) were worst. The minimum left atrium volume was higher (26 ± 10 vs 15 ± 8 mL) and left atrium independent strain was lower in hypertensive patients (4.0% vs 6.5%, P = .001). Left atrium independent strain only correlated with minimum left atrium volume (r = -.31, P = .048).

DISCUSSION

The left ventricle longitudinal performance has an important contributing role in the left atrium reservoir function; despite this finding, the independent strain was unrelated to left ventricle longitudinal function.

CONCLUSION

Independent strain can identify atrial myocyte contractile dysfunction in hypertension given the relative absence of hemodynamic loads during this period. Additionally, quantification of left atrium minimum volume suggests indirectly the presence of atrial myocyte contractile dysfunction.

Isolated pulmonary regurgitation causes decreased right ventricular longitudinal function and compensatory increased septal pumping in a porcine model

Aim

Longitudinal ventricular contraction is a parameter of cardiac performance with predictive power. Right ventricular (RV) longitudinal function is impaired in patients with free pulmonary regurgitation (PR) following corrective surgery for Tetralogy of Fallot (TOF). It remains unclear whether this is a consequence of the surgical repair, or whether it is inherent to PR. The aim of this study was to assess the relationship between longitudinal, lateral and septal pumping in a porcine model of isolated PR.

Methods

Piglets were divided into a control (n = 8) group and a treatment (n = 12) group, which received a stent in the pulmonary valve orifice, inducing PR. After 2–3 months, animals were subjected to cardiac magnetic resonance imaging. A subset of animals (n = 6) then underwent percutaneous pulmonary valve replacement (PPVR) with follow‐up 1 month later. Longitudinal, lateral and septal contributions to stroke volume (SV) were quantified by measuring volumetric displacements from end‐diastole to end‐systole in the cardiac short axis and long axis.

Results

PR resulted in a lower longitudinal contribution to RV stroke volume, compared to controls (60.0 ± 2.6% vs. 73.6 ± 3.8%; P = 0.012). Furthermore, a compensatory increase in septal contribution to RVSV was observed (11.0 ± 1.6% vs. −3.1 ± 1.5%; P < 0.0001). The left ventricle (LV) showed counter‐regulation with an increased longitudinal LVSV. Changes in RV longitudinal function were reversed by PPVR.

Conclusion

These findings suggest that PR contributes to decreased RV longitudinal function in the absence of scarring from cardiac surgery. Measurement of longitudinal RVSV may aid risk stratification and timing for interventional correction of PR in TOF patients.

Left Atrial Strain at Different Stages of Myxomatous Mitral Valve Disease in Dogs

Background

Decreased function of the left atrium (LA) is a useful prognostic indicator in dogs with myxomatous mitral valve disease (MMVD). In humans, LA strain is a novel severity indicator of mitral regurgitation, but its clinical utility in dogs has not been confirmed.

Objectives

To examine whether LA strain as evaluated with speckle‐tracking echocardiography is associated with MMVD stage in dogs.

Animals

Fifty‐two client‐owned dogs with MMVD.

Methods

Cross‐sectional study. Dogs were classified as stage B1, B2, C, or D, according to the American College of Veterinary Internal Medicine consensus. Physical examination findings and echocardiographic variables were compared among the groups. To assess the comparative accuracy of echocardiographic variables in identifying dogs with the presence or history congestive heart failure (CHF), receiver operating characteristic curves and multivariate logistic analysis were used.

Results

There were no significant differences in parameters of LA strain between B1 and B2 groups. However, LA longitudinal strain during atrial contraction (ε_A) (median, 19.1%; interquartile range, 15.3–24.3% in B1, 19.6%; 14.1–21.4% in B2, 6.2%; 3.18–11.2% in C/D) and during ventricular systole (ε_S) (32.7%; 28.9–39.2% in B1, 35.6%; 31.7–41.9% in B2, 23.6%; 16.9–26.1% in C/D) were significantly lower in stages C/D than in stages B1 and B2. In multivariate logistic regression analysis, ε_A and peak early diastolic mitral inflow velocity were identified as independent indicators of stage C/D.

Conclusions and Clinical Importance

ε_A was the best predictor of the presence or history of CHF. Further studies are needed to determine the clinical implications of these findings for treatment decisions and prognosis determination.

Changes in ductus venosus flow profile in twin-twin transfusion syndrome: role in risk stratification

OBJECTIVES

To evaluate changes in ductus venosus (DV) waveforms and the timing of these changes in twin-twin transfusion syndrome (TTTS), to relate these to disease severity and to assess the clinical applicability of the suggested measurements in the prediction of TTTS.

METHODS

DV time intervals and velocity-time integrals (VTI) normalized to cardiac cycle and total VTI, respectively, as well as velocity ratios were analyzed in 149 monochorionic diamniotic (MCDA) twin pairs. Pregnancies were assigned to the following groups: uncomplicated MCDA (n = 29); TTTS Stages I+II (n = 50); TTTS Stages III+IV (n = 49); and pre-TTTS (n = 21), of which 14 remained stable and seven progressed to TTTS. Intertwin differences were calculated as larger/recipient minus smaller/donor and related to disease severity. Receiver-operating characteristics curve analysis was used to distinguish TTTS vs uncomplicated MCDA and pre-TTTS progressing to TTTS vs non-progressing pre-TTTS. Intra- and interobserver reliability of measurement of DV parameters were evaluated using intraclass correlation coefficients (ICCs).

RESULTS

No intertwin differences in DV parameters were found in uncomplicated MCDA pregnancies. Diastolic VTIs and filling times were significantly shorter in recipient twins in TTTS cases and in larger pre-TTTS twins in comparison with their cotwins. Time intervals, VTIs and velocity ratios correlated significantly with Quintero stages. An intertwin difference in early filling time (eT) normalized to cardiac cycle, eT (%) ≤ -3.6%, could differentiate TTTS from uncomplicated MCDA pregnancies (82.8% sensitivity; 79.8% specificity) and eT (%) ≤ -2.8% predicted progression to TTTS (73.1% sensitivity; 67.4% specificity).

CONCLUSIONS

DV flow profiles and timing of waveform events are already altered in pre-TTTS and early-stage disease, reflecting abnormal ventricular filling and circulatory imbalance. Intertwin comparison of filling times and VTI may allow prediction of evolving TTTS in MCDA pregnancies. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Left Atrial Function in Patients with Chronic Chagasic Cardiomyopathy

BACKGROUND

Chagas disease is a cause of dilated cardiomyopathy, and information about left atrial (LA) function in this disease still lacks.

OBJECTIVE

To assess the different LA functions (reservoir, conduit and pump functions) and their correlation with the echocardiographic parameters of left ventricular (LV) systolic and diastolic functions.

METHODS

10 control subjects (CG), and patients with Chagas disease as follows: 26 with the indeterminate form (GI); 30 with ECG alterations (GII); and 19 with LV dysfunction (GIII). All patients underwent M-mode and two-dimensional echocardiography, pulsed-wave Doppler and tissue Doppler imaging.

RESULTS

Reservoir function (Total Emptying Fraction: TEF): (p <0.0001), lower in GIII as compared to CG (p = 0.003), GI (p <0.001) and GII (p <0.001). Conduit function (Passive Emptying Fraction: PEF): (p = 0.004), lower in GIII (GIII and CG, p = 0.06; GI and GII, p = 0.06; and GII and GIII, p = 0.07). Pump function (Active Emptying Fraction: AEF): (p = 0.0001), lower in GIII as compared to CG (p = 0.05), GI (p<0.0001) and GII (p = 0.002). There was a negative correlation of E/e' (average) with the reservoir and pump functions (TEF and AEF), and a positive correlation of e' (average) with s' wave (both septal and lateral walls) and the reservoir, conduit and pump LA functions.

CONCLUSION

An impairment of LA functions in Chagas cardiomyopathy was observed.

Compensatory increase of left atrial external work to left ventricular dysfunction caused by afterload increase

Afterload mismatch can cause acute decompensation leading to an occurrence of acute heart failure. We investigated how the left atrium (LA) and left ventricle (LV) react to acute increases in afterload using speckle tracking echocardiography (STE). LA strain and volume were obtained by STE in 10 dogs during banding of descending aorta (AoB). Simultaneously, LA pressure was measured by a micromanometer-tipped catheter. LA peak negative strain during LA contraction, strain change during LA relaxation (early reservoir strain), and that during LA dilatation (late reservoir strain) were obtained from LA longitudinal strain-volume curves. From pressure-strain curves, the areas of A-loop and V-loops were computed as the work during active contraction and relaxation (A-work) and that during passive filling and emptying (V-work). AoB increased LV systolic pressure (105 ± 15 vs. 163 ± 12 mmHg, P < 0.01) and mean LA pressure (3.8 ± 1.2 vs. 7.1 ± 2.0 mmHg, P < 0.01). LV global circumferential strain decreased (−18.8 ± 3.5 vs. −13.2 ± 3.5%, P < 0.01), but LV stroke volume was maintained (8.4 ± 2.3 vs. 9.6 ± 3.6 ml). LA peak negative strain (−2.9 ± 2.3 vs. −9.8 ± 4.0%, P < 0.01) and early reservoir strain (4.5 ± 2.1 vs. 7.7 ± 2.4%, P < 0.05) increased by AoB, but late reservoir strain did not change (8.9 ± 3.4 vs. 6.1 ± 3.4%). A-work significantly increased (3.2 ± 2.0 vs. 19.2 ± 15.1 mmHg %, P < 0.01), whereas V-work did not change (13.3 ± 7.1 vs. 13.1 ± 7.7 mmHg %). In conclusion, LA external work during active contraction and relaxation increased as compensation for LV dysfunction during aortic banding. Atrial dysfunction may lead failure of this mechanism and hemodynamic decompensation.

Left atrial passive emptying function during dobutamine stress MR imaging is a predictor of cardiac events in patients with suspected myocardial ischemia

OBJECTIVES

The aim of this study was to determine the prognostic value of assessing left atrial function during dobutamine stress testing.

BACKGROUND

Left ventricular diastolic dysfunction precedes systolic wall motion abnormalities in the ischemic cascade. Severity of left ventricular diastolic function during cardiac stress is not characterized well by current clinical imaging protocols but may be an important prognostic factor. We hypothesized that abnormal early left atrial emptying measured during dobutamine stress cardiac magnetic resonance will reflect these diastolic changes and may be associated with cardiovascular outcomes.

METHODS

We enrolled 122 consecutive patients referred for dobutamine stress cardiac magnetic resonance for suspected myocardial ischemia. Left atrial volumes were retrospectively measured by the biplane area-length method at left ventricular end-systole (VOL(max)) and before atrial contraction (VOL(bac)). Left atrial passive emptying fraction defined by (VOL(max) - VOL(bac)) × 100%/VOL(max) and the absolute percent increase in left atrial passive emptying fraction during dobutamine stress (ΔLAPEF) were quantified.

RESULTS

Twenty-nine major adverse cardiac events (MACE) occurred during follow-up (median 23 months). By Kaplan-Meier analysis, patients with ΔLAPEF <10.8 (median) experienced higher incidence of MACE than did patients with a ΔLAPEF >10.8 (p = 0.004). By univariable analysis, ΔLAPEF was strongly associated with MACE (unadjusted hazard ratio for every 10% decrease = 1.56, p < 0.005). By multivariable analysis, every 10% decrease in ΔLAPEF carried a 57% increase in MACE, after adjustment to presence of myocardial ischemia and infarction.

CONCLUSIONS

Reduced augmentation of left atrial passive emptying fraction during dobutamine stress demonstrated strong association with MACE. We speculate that reduced left atrial passive emptying reserve during inotropic stress may represent underlying diastolic dysfunction and warrants further investigation.

Left atrial flow propagation velocity: a new approach for assessment of left atrial reservoir function

To assess the feasibility of left atrial flow propagation velocity (LAFPV) measurement and to evaluate the influence of preload alterations on this new parameter of left atrial (LA) reservoir function as compared to conventional echocardiographic indices. 30 healthy volunteers (26 ± 5 years, 20 males) underwent echocardiographic examination at rest, during passive leg lifting and after sublingual administration of nitroglycerine with subsequent Valsalva maneuver. LA reservoir function was assessed by conventional indices including LA expansion index, peak velocity and velocity-time integral of pulmonary venous systolic flow. As well, LAFPV was measured by color M-mode in an apical 4-chamber view as the slope of the transatrial flow wave during LA reservoir phase. LAFPV measurement was feasible in 25 subjects (83%). All conventional parameters of LA reservoir function were significantly altered from resting values by both load-modifying conditions. However, LAPFV was not significantly altered by such maneuvers (228 ± 28 cm s⁻¹ at rest vs. 238 ± 3 cm s⁻¹ during leg lifting, P = NS, vs. 218 ± 38 cm s(-1) after nitroglycerin with Valsalva maneuver, P = NS vs. rest, P < 0.01 vs. leg lifting). LAFPV can be measured in a majority of subjects and represents a new, less load-dependent index of LA reservoir function that may more appropriately reflect LA compliance.

Left atrial stiffness and its implications for cardiac function

Proper atrial function is essential for overall cardiovascular performance, mainly by its four major functions, namely, bioelectrical, hormonal, metabolic and hemodynamic. With regard to the latter, atria modulate ventricular filling by smoothing the transformation of the continuous venous return to the intermittent filling pattern of the ventricles during diastole through three main components: a phase of reservoir mainly during ventricular systole, a conduit phase during ventricular diastole and an active phase in late ventricular diastole. Although the atria assume a dynamic role in ventricular filling progression, atrial function and emptying pattern is, conversely, highly influenced by the ventricular diastolic wall stress, underlying the close connection observed between these chambers. This review focuses essentially on left atrial mechanical role, particularly on the physiological and clinical consequences of disturbed atrial compliance.

Propofol alters left atrial function evaluated with pressure-volume relations in vivo

The effects of IV anesthetics on left atrial (LA) function in vivo are unknown. We tested the hypothesis that propofol alters LA mechanics evaluated with pressure-volume relations in barbiturate-anesthetized dogs (n = 9) instrumented for measurement of aortic, LA, and left ventricular (LV) pressures (micromanometers) and LA volume (epicardial orthogonal sonomicrometers). LA myocardial contractility (E(es)) and dynamic chamber stiffness were assessed with end-systolic and end-reservoir pressure-volume relations, respectively. Relaxation was determined from the slope of LA pressure decline after contraction corrected for peak LA pressure. LA stroke work and reservoir function were assessed by A and V loop area, respectively, from the steady-state pressure-volume diagram. LA-LV coupling was determined by the ratio of E(es) to LV elastance. Dogs received propofol (5, 10, 20, or 40 mg. kg(-1). h(-1)) in a random manner, and LA function was determined after a 15-min equilibration at each dose. Propofol decreased heart rate, mean arterial blood pressure, and the maximal rate of increase of LV pressure. Propofol caused dose-related reductions in E(es), dynamic chamber stiffness, and E(es)/LV elastance. An increase in V loop area and declines in LA stroke work, emptying fraction, and the active LA contribution to LV filling also occurred. Relaxation was unchanged. The results indicate that propofol depresses LA myocardial contractility, reduces dynamic chamber stiffness, maintains reservoir function, and impairs LA-LV coupling but does not alter LA relaxation in vivo.

IMPLICATIONS

Propofol depresses contractile function of left atrial (LA) myocardium, impairs mechanical matching between the LA and the left ventricular (LV), and reduces the active LA contribution to LV filling in vivo. Compensatory decreases in chamber stiffness contribute to relative maintenance of LA reservoir function during the administration of propofol.

Modulation of left atrial function by ventricular filling impairment

Left atrial function is an important determinant of ventricular filling. Assessment of the complex role that the atrial cavity exerts in the ventricular filling process can be made noninvasively. Computing the net instantaneous difference between mitral and pulmonary venous flow is an approach which permits the construction of the left atrial volume curve throughout the cardiac cycle (as well as the left ventricular volume curve during diastole), and to quantify the 3 different functions that the cavity performs. In particular, increasing degrees of ventricular filling impairment are met by mechanical left atrial adaptations which basically rely on the Starling mechanism, with the reservoir/pump complex activated to the limit of the preload reserve of the cavity. At end-stage left ventricular dysfunction, however, the atrial reservoir and the booster pump function decline and conduit takes precedence, suggesting afterload mismatch, impaired atrial compliance and, perhaps, depressed atrial contractility. Increased wall stiffening and reduced elastic recoil induced by chronic atrial distension might explain the additional power of atrial size in stratifying prognostically patients with left ventricular dysfunction.

Left atrial relaxation and left ventricular systolic function determine left atrial reservoir function

BACKGROUND

Determinants of left atrial (LA) reservoir function and its influence on left ventricular (LV) function have not been quantified.

METHODS AND RESULTS

In an open-pericardium, paced (70 and 90 bpm) pig model of LV regional ischemia (left anterior descending coronary constriction), with high-fidelity LV, LA, and RV pressure recordings, we obtained the LA area with 2D automated border detection echocardiography, LA pressure-area loops, and Doppler transmitral flow. We calculated LV tau, LA relaxation (a-x pressure difference divided by time, normalized by a pressure), and stiffness (slope between x and v pressure points of v loop). Determinants of total LA reservoir (maximum-minimum area, cm(2)) were identified by multiple regression analysis. Different mean rates of LA area increase identified 2 consecutive (early rapid and late slow) reservoir phases. During ischemia, LV long-axis shortening (LAS, LV base systolic descent) and LA reservoir area change decreased (7.3+/-0.3 [SEM] versus 5.6+/-0.3 cm(2), P<0.001) and LA stiffness increased (1.6+/-0.3 versus 3.1+/-0.3 mm Hg/cm(2), P=0.009). Early reservoir area change depended on LA mean ejection rate (LA area at ECG P wave minus minimum area divided by time; multiple regression coefficient=0.9; P<0.001) and relaxation (coefficient=4.9 cm(2)xms/s; P<0.001). Late reservoir area change depended on LAS (coefficient=8 cm/s; P<0.001). Total reservoir filling depended on LA stiffness (coefficient=-0.31 cm(4)/mm Hg; P=0. 001) and cardiac output (coefficient=0.001 cm(2)xmin/L; P=0.002). The strongest predictor of cardiac output was LA reservoir filling (coefficient=301 L/minxcm(2); P<0.001). The v loop area was determined by cardiac output, LV ejection time, tau, and early transmitral flow.

CONCLUSIONS

Two (early and late) reservoir phases are determined by LA contraction and relaxation and LV base descent. Acute LV regional ischemia increases LA stiffness and impairs LA reservoir function by reducing LV base descent.