Septal geometry in the unloaded living human heart

Echocardiographic Patterns of Abnormal Septal Motion: Beyond Myocardial Ischemia

Abnormal septal motion (ASM), which often is associated with myocardial ischemia, is also observed in other diseases. Owing to the position of the interventricular septum (IVS) in the heart, its movement not only relies on contractile properties but is also affected by the pressure gradient between the 2 ventricles and by the mode of electrical activation. Echocardiography allows the operator to focus on the motion of the IVS, analyzing its characteristics and thereby gaining information about the possible underlying pathophysiological mechanism. In this review, we focused on the main echocardiographic patterns of ASM that are not related to a failure of contractile properties of the septum (i.e., acute coronary syndrome and cardiomyopathies), showing their pathophysiological mechanisms and underlining their diagnostic usefulness in clinical practice.

Diastolic Ventricular Interaction in Heart Failure With Preserved Ejection Fraction

Background

Exercise‐induced pulmonary hypertension is common in heart failure with preserved ejection fraction (HFpEF). We hypothesized that this could result in pericardial constraint and diastolic ventricular interaction in some patients during exercise.

Methods and Results

Contrast stress echocardiography was performed in 30 HFpEF patients, 17 hypertensive controls, and 17 normotensive controls (healthy). Cardiac volumes, and normalized radius of curvature (NRC) of the interventricular septum at end‐diastole and end‐systole, were measured at rest and peak‐exercise, and compared between the groups. The septum was circular at rest in all 3 groups at end‐diastole. At peak‐exercise, end‐systolic NRC increased to 1.47±0.05 (P<0.001) in HFpEF patients, confirming development of pulmonary hypertension. End‐diastolic NRC also increased to 1.54±0.07 (P<0.001) in HFpEF patients, indicating septal flattening, and this correlated significantly with end‐systolic NRC (ρ=0.51, P=0.007). In hypertensive controls and healthy controls, peak‐exercise end‐systolic NRC increased, but this was significantly less than observed in HFpEF patients (HFpEF, P=0.02 versus hypertensive controls; P<0.001 versus healthy). There were also small, non‐significant increases in end‐diastolic NRC in both groups (hypertensive controls, +0.17±0.05, P=0.38; healthy, +0.06±0.03, P=0.93). In HFpEF patients, peak‐exercise end‐diastolic NRC also negatively correlated (r=−0.40, P<0.05) with the change in left ventricular end‐diastolic volume with exercise (ie, the Frank‐Starling mechanism), and a trend was noted towards a negative correlation with change in stroke volume (r=−0.36, P=0.08).

Conclusions

Exercise pulmonary hypertension causes substantial diastolic ventricular interaction on exercise in some patients with HFpEF, and this restriction to left ventricular filling by the right ventricle exacerbates the pre‐existing impaired Frank‐Starling response in these patients.

Hemodynamic forces in the left and right ventricles of the human heart using 4D flow magnetic resonance imaging: Phantom validation, reproducibility, sensitivity to respiratory gating and free analysis software

Purpose

To investigate the accuracy, reproducibility and sensitivity to respiratory gating, field strength and ventricle segmentation of hemodynamic force quantification in the left and right ventricles of the heart (LV and RV) using 4D-flow magnetic resonance imaging (MRI), and to provide free hemodynamic force analysis software.

Materials and methods

A pulsatile flow phantom was imaged using 4D flow MRI and laser-based particle image velocimetry (PIV). Cardiac 4D flow MRI was performed in healthy volunteers at 1.5T (n = 23). Reproducibility was investigated using MR scanners from two different vendors on the same day (n = 8). Subsets of volunteers were also imaged without respiratory gating (n = 17), at 3T on the same day (n = 6), and 1–12 days later on the same scanner (n = 9, median 6 days). Agreement was measured using the intraclass correlation coefficient (ICC).

Results

Phantom validation showed good accuracy for both scanners (Scanner 1: bias -14±9%, y = 0.82x+0.08, R² = 0.96, Scanner 2: bias -12±8%, y = 0.99x-0.08, R² = 1.00). Force reproducibility was strong in the LV (0.09±0.07 vs 0.09±0.07 N, bias 0.00±0.04 N, ICC = 0.87) and RV (0.09±0.06 vs 0.09±0.05 N, bias 0.00±0.03, ICC = 0.83). Strong to very strong agreement was found for scans with and without respiratory gating (LV/RV: ICC = 0.94/0.95), scans on different days (ICC = 0.92/0.87), and 1.5T and 3T scans (ICC = 0.93/0.94).

Conclusion

Software for quantification of hemodynamic forces in 4D-flow MRI was developed, and results show high accuracy and strong to very strong reproducibility for both the LV and RV, supporting its use for research and clinical investigations. The software including source code is released freely for research.

Evidence Supporting the Existence of a Distinct Obese Phenotype of Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure (HF) with preserved ejection fraction (HFpEF) is a heterogeneous syndrome. Phenotyping patients into pathophysiologically homogeneous groups may enable better targeting of treatment. Obesity is common in HFpEF and has many cardiovascular effects, suggesting that it may be a viable candidate for phenotyping. We compared cardiovascular structure, function, and reserve capacity in subjects with obese HFpEF, those with nonobese HFpEF, and control subjects.

METHODS

Subjects with obese HFpEF (body mass index ≥35 kg/m²; n=99), nonobese HFpEF (body mass index <30 kg/m²; n=96), and nonobese control subjects free of HF (n=71) underwent detailed clinical assessment, echocardiography, and invasive hemodynamic exercise testing.

RESULTS

Compared with both subjects with nonobese HFpEF and control subjects, subjects with obese HFpEF displayed increased plasma volume (3907 mL [3563-4333 mL] versus 2772 mL [2555-3133 mL], and 2680 mL [2380-3006 mL]; P<0.0001), more concentric left ventricular remodeling, greater right ventricular dilatation (base, 34±7 versus 31±6 and 30±6 mm, P=0.0005; length, 66±7 versus 61±7 and 61±7 mm, P<0.0001), more right ventricular dysfunction, increased epicardial fat thickness (10±2 versus 7±2 and 6±2 mm; P<0.0001), and greater total epicardial heart volume (945 mL [831-1105 mL] versus 797 mL [643-979 mL] and 632 mL [517-768 mL]; P<0.0001), despite lower N-terminal pro-B-type natriuretic peptide levels. Pulmonary capillary wedge pressure was correlated with body mass and plasma volume in obese HFpEF (r=0.22 and 0.27, both P<0.05) but not in nonobese HFpEF (P≥0.3). The increase in heart volumes in obese HFpEF was associated with greater pericardial restraint and heightened ventricular interdependence, reflected by increased ratio of right- to left-sided heart filling pressures (0.64±0.17 versus 0.56±0.19 and 0.53±0.20; P=0.0004), higher pulmonary venous pressure relative to left ventricular transmural pressure, and greater left ventricular eccentricity index (1.10±0.19 versus 0.99±0.06 and 0.97±0.12; P<0.0001). Interdependence was enhanced as pulmonary artery pressure load increased (P for interaction <0.05). Compared with those with nonobese HFpEF and control subjects, obese patients with HFpEF displayed worse exercise capacity (peak oxygen consumption, 7.7±2.3 versus 10.0±3.4 and12.9±4.0 mL/min·kg; P<0.0001), higher biventricular filling pressures with exercise, and depressed pulmonary artery vasodilator reserve.

CONCLUSIONS

Obesity-related HFpEF is a genuine form of cardiac failure and a clinically relevant phenotype that may require specific treatments.

Regional contribution to ventricular stroke volume is affected on the left side, but not on the right in patients with pulmonary hypertension

To develop more sensitive measures of impaired cardiac function in patients with pulmonary hypertension (PH), since detection of impaired right ventricular (RV) function is important in these patients. With the hypothesis that a change in septal function in patients with PH is associated with altered longitudinal and lateral function of both ventricles, as a compensatory mechanism, we quantified the contributions of these parameters to stroke volume (SV) in both ventricles using cardiac magnetic resonance (CMR). Seventeen patients (10 females) evaluated for PH underwent right heart catheterization (RHC) and CMR. CMR from 33 healthy adults (13 females) were used as controls. Left ventricular (LV) atrioventricular plane displacement (AVPD) and corresponding longitudinal contribution to LVSV was lower in patients (10.8 ± 3.2 mm and 51 ± 12 %) compared to controls (16.6 ± 1.9 mm and 59 ± 9 %, p < 0.0001 and p < 0.01, respectively). This decrease did not differ in patient with ejection fraction (EF) >50 % and <50 % (p = 0.5) and was compensated for by increased LV lateral contribution to LVSV in patients (49 ± 13 % vs. 37 ± 7 %, p = 0.001). Septal motion contributed less to LVSV in patients (5 ± 8 %) compared to controls (8 ± 4 %, p = 0.05). RV AVPD was lower in patients (12.0 ± 3.6 mm vs. 21.8 ± 2.2 mm, p < 0.0001) but longitudinal and lateral contribution to RVSV did not differ between patients (78 ± 17 % and 29 ± 16 %) and controls (79 ± 9 % and 31 ± 6 % p = 0.7 for both) explained by increased RV cross sectional area in patients. LV function is affected in patients with PH despite preserved global LV function. The decreased longitudinal contribution and increased lateral contribution to LVSV was not seen in the RV, contrary to previous findings in patients with volume loaded RVs.

The relationship between longitudinal, lateral, and septal contribution to stroke volume in patients with pulmonary regurgitation and healthy volunteers

Septal systolic motion is towards the left ventricle (LV) in healthy hearts. Patients with pulmonary regurgitation (PR) and right ventricular (RV) volume overload have systolic septal motion toward the RV. This may affect the longitudinal contribution from atrioventricular plane displacement (AVPD) and septal and lateral contribution to stroke volume (SV). The study aimed to quantify these contributions to SV in patients with PR. Cardiac magnetic resonance imaging was used for assessment of cardiac volumes. Patients (n = 30; age 9-59 yr) with PR due to surgically corrected tetralogy of Fallot and 54 healthy controls (age 10-66 yr) were studied. Longitudinal contribution to RVSV was 47 ± 2% (means ± SE) in patients with PR and 79 ± 1% in controls (P < 0.001). Lateral contribution to RVSV and LVSV was 40 ± 1 and 62 ± 2% in patients and 31 ± 1 and 36 ± 1% in controls (P < 0.001 for both). Septal motion contributed to RVSV by 8 ± 1% in patients and by 7 ± 1% to LVSV in controls (P < 0.001). PR patients have decreased longitudinal contribution to RVSV and increased lateral pumping, resulting in larger outer volume changes and septal motion towards the RV. The changes in RV pumping physiology may be explained by RV remodeling resulting in lower systolic inflow of blood into the right atrium in relation to SV. This avoids the development of pendulum volume between the caval veins and right atrium, which would occur in PR patients if longitudinal contribution to SV was preserved. Decreased AVPD suggests that tricuspid annular excursion, a marker of RV function, is less valid in these patients.

VENTRICULAR INTERACTION AND CARDIAC PATHOLOGIES IN A THICK SHELL MODEL OF CARDIAC CHAMBER DEFORMATION

Ventricular interdependence is an important part of heart function, and hence a key mediator of most pathological consequences of its impairment. It can only be explained by accounting for overall chamber deformation as well as cardiac dimensions and nonlinear material properties. Further, clinically useful interpretation of imaging data about pathological alterations in chamber geometry is hampered by lack of understanding of its significance in cardiac function. A model has been developed which describes the ventricles and septum as portions of ellipsoid shells, allowing structural characterization of diastolic ventricular interaction over arbitrary ranges of chamber pressures and volumes as well as intrathoracic pressures. Chamber configuration is derived as a function of pressure gradients by combining shell element equilibrium equations through static boundary conditions applied at the sulcus. Coupling coefficients between state variables are then calculated by letting the system evolve quasistatically through the solution space. The model is used to simulate a number of cardiac pathologies (constrictive pericarditis, restrictive myocarditis, left/right free wall and septal hypertrophy, left dilatative cardiomyopathy) and quantify their effect on ventricular pressure–pressure coupling as well as diastolic pressure–volume relationships. Results match experimental observations where available. The model can aid in interpreting diagnostic data about chamber geometry in a quantitative manner, and the differential effect of cardiac pathologies with otherwise similar phenomenology on ventricular interaction can serve as a discriminating diagnostic criterion.

Racial and ethnic differences in subclinical myocardial function: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Racial/ethnic differences in the incidence and severity of heart failure (HF) are not well understood, but may be related to pre-existing variations in myocardial function.

OBJECTIVE

To examine racial/ethnic differences in regional myocardial function among asymptomatic individuals free of known cardiovascular disease.

DESIGN, SETTING AND PATIENTS

The Multi-Ethnic Study of Atherosclerosis is a prospective, observational study of individuals without baseline cardiovascular disease, representing four major racial/ethnic groups. A total of 1099 study participants underwent cardiac MRI with tissue tagging; for each study, peak systolic strain (Ecc) and strain rate (SRs) were determined in four left ventricular (LV) regions.

MAIN OUTCOME MEASURES

Multiple linear regression was used to analyse the relationship between race/ethnicity and regional strain (Ecc and SRs) while adjusting for cardiovascular risk factors.

RESULTS

Compared with other racial/ethnic groups, Chinese-Americans had the greatest magnitude of Ecc in a majority of LV regions (-19.60±3.78, p<0.05); Chinese-Americans also had the greatest absolute values for SRs in all regions, reflecting higher rate of systolic contraction (-2.01±0.76, p<0.05). Conversely, African-Americans had the lowest Ecc values (-17.50±4.00, p<0.05) in the majority of wall regions while Hispanics demonstrated the lowest rate of contractility in all wall regions (-1.44±0.50, p≤0.001) in comparison with the other racial/ethnic groups. These race-based differences remained significant in the majority of LV wall regions after adjusting for multiple variables, including hypertension and LV mass.

CONCLUSIONS

Important race-based differences in regional LV systolic function in a large cohort of asymptomatic individuals have been demonstrated. Further research is needed to investigate the possible mechanisms related to the race/ethnicity-based variations found in this study.

Pathophysiology of right ventricular failure in pulmonary hypertension

This review focuses on right ventricular anatomy and function and the significance of ventricular interdependence in the response of the right ventricle to an increase in afterload. This is followed by a discussion of the pathophysiology of right ventricular failure in pulmonary arterial hypertension as well as in other clinical syndromes of pulmonary hypertension. Pulmonary hypertension is common in critically ill children and is associated with several conditions. Regardless of the etiology, an increase in right ventricular afterload leads to a number of compensatory changes in cardiovascular physiology. These changes are not altogether intuitive and require an understanding of right ventricular physiology and ventricular interdependence to optimize the care of these patients.

Patterns of the Interventricular Septal Motion Can Predict Conditions of Patients with Pulmonary Hypertension

OBJECTIVES

We sought to investigate the clinical and hemodynamic implications of interventricular septal motion in patients with pulmonary hypertension.

BACKGROUND

In patients with pulmonary hypertension, we have noticed two types of peculiar motions of the interventricular septum by M-mode echocardiography: marked early systolic anterior motion (type A) and marked early diastolic posterior motion (type B).

METHODS

We performed echocardiography on 32 patients (age 42 +/- 13 years) with pulmonary hypertension within 1 week of cardiac catheterization. Type A was found in 14 patients (group A) and type B was found in 18 patients (group B).

RESULTS

There was no difference between two groups in left ventricular eccentricity index at early diastole (2.4 +/- 0.6 vs 2.1 +/- 0.7) and mean pulmonary arterial pressure (54 +/- 10 vs 53 +/- 13 mm Hg). However, New York Heart Association functional class (2.7 +/- 0.4 vs 2.2 +/- 0.3) and serum levels of brain natriuretic peptide (271 +/- 155 vs 74 +/- 55 pg/mL) were significantly higher and cardiac index (1.7 +/- 0.3 vs 2.3 +/- 0.4 L/min/m(2)) was significantly lower in group A (P < .001). Simultaneous recordings of both ventricular pressures showed that right ventricular pressure was higher than left ventricular pressure during whole diastole in group A, but in group B, during only early diastole. By multiple linear regression analysis, type A motion independently predicted low cardiac index.

CONCLUSIONS

Interventricular septal motion could predict patients' conditions. Patients with type A motion were more morbid clinically and hemodynamically than patients with type B motion.

Effect of bundle branch block on cardiac output: a whole heart simulation study

The heart is an electrically controlled fluid pump which operates by mechanical contraction. Whole heart modelling is a computationally daunting task which must incorporate several subsystems: mechanical, electrical, and fluidic. Numerous feedback mechanisms on many levels, and operating at different scales, exist to finely control behaviour. Understanding these interactions is necessary to understand heart operation, as well as pathologies and therapies. A review of the components in such a model is given. The authors then present a framework for their electro-mechano-fluidic whole heart model based on cable methods. The model incorporates atria and ventricles, and has functioning valves with papillary muscles. The effect of altered propagation due to left and right bundle branch block on cardiac output is examined using the cable-based model. Results are compared to clinically observed phenomena. Good agreement was obtained, but tighter coupling of mechanical and electrical events is needed to fully account for behaviour. Cable-based models offer an alternative to continuum models.

Pulmonary Hypertension: Accuracy of Detection with Left Ventricular Septal-to–Free Wall Curvature Ratio Measured at Cardiac MR

PURPOSE

To retrospectively evaluate the accuracy and reproducibility of the cardiac magnetic resonance (MR) imaging-derived left ventricular septal-to-free wall curvature ratio for prediction of the right ventricular systolic pressure (RVSP) in patients clinically known to have or suspected of having pulmonary hypertension (PH), with same-day right-side heart catheterization (RHC) as the reference standard.

MATERIALS AND METHODS

Institutional review board approval was received for this HIPAA-compliant study. Sixty-one patients clinically known or suspected of having PH underwent cardiac MR and RHC on the same day. Interventricular septal curvature (C(IVS)) and left ventricular free wall curvature (C(FW)) measured at end systole were used to derive the curvature ratio (C(IVS)/C(FW)). Effective distending transmural pressure (dP(FW)) and transseptal pressure gradient (dP(IVS)) were assumed to be equivalent, respectively, to the systolic blood pressure (SBP) and the difference between SBP and RVSP. Curvature ratio and SBP were used to noninvasively estimate RVSP. Linear regression analysis was performed to assess the difference between curvature ratio and rate of pressure rise (dP) ratio (dP(IVS)/dP(FW)). The accuracy of the dichotomized curvature ratio in PH detection was analyzed by using receiver operating characteristic (ROC) curves.

RESULTS

PH, defined as RVSP higher than 40 mm Hg, was confirmed with RHC in 46 patients. A direct linear correlation between dP ratio and curvature ratio was observed (r = 0.85, P < .001). Bland-Altman analysis revealed moderate agreement between cardiac MR- and RHC-derived RVSPs (mean difference, -1.1 mm Hg +/- 15.9 [standard deviation]). ROC analysis of the accuracy of the curvature ratio for detection of increased RVSP revealed 87% sensitivity and 100% specificity (area under ROC curve, 0.95; P < .001). Intraobserver (r = 0.97) and interobserver (r = 0.95) curvature ratio measurements were closely correlated.

CONCLUSION

In patients clinically known to have or suspected of having PH, cardiac MR-derived curvature ratio, as compared with RHC measurement, was an accurate and reproducible index for estimation of RVSP.

Real-time cine MRI of ventricular septal motion: a novel approach to assess ventricular coupling

The purpose of this study was to assess the feasibility of magnetic resonance imaging (MRI) to evaluate in real-time, the effects of respiration in ventricular septal motion and configuration in normal volunteers and cardiac patients. Real-time cine MRI studies, using the steady-state free precession (SSFP) technique, were performed in the cardiac short-axis during operator-guided deep inspiration and expiration in normal volunteers (N = 6), and in patients with constrictive pericarditis (CP; N = 6), restrictive cardiomyopathy (RCM; N = 4), chronic cor pulmonale (N = 5), and pericardial effusion. The respiratory effects on septal position and configuration during early ventricular filling were visually assessed. Results were compared with the short-axis breath-hold cine MRI studies, obtained at end-inspiration. In CP patients, onset of inspiration led to a leftward inversion in four of six patients and flattening of the septum in two of six patients during early ventricular filling. Septal abnormalities progressively disappeared during the following heartbeats. A similar pattern was found in one of six patients with pericardial effusion. The above pattern was absent in RCM patients. Although septal flattening during early inspiration was also found in two of six normal volunteers, flattening was minimal compared to that in CP patients. In all cor pulmonale patients, septal flattening or inversion was present, but this was not influenced by respiratory motion. Real-time cine MRI is a promising technique for determining the influence of respiration on septal motion and might be helpful in differentiating between different causes of impaired ventricular filling.

Hypoxia: unique myocardial morphology?

OBJECTIVE

The objective of this study was to investigate the effects of chronic and intermittent hypoxia on myocardial morphology.

METHODS

Rats randomly divided into 3 groups (n = 14 per group) were exposed to room air (Fio(2) = 0.21), chronic hypoxia (Fio(2) = 0.10), and intermittent hypoxia (chronic hypoxia with 1 hour per day of room air) for 2 weeks. Weight, blood gas analysis, hematocrit, hemoglobin, red cells, and right and left ventricular pressures were measured. Hearts excised for morphologic examination were randomly divided into 2 groups (9 per group for gross morphologic measurements and 5 per group for histologic and morphometric analysis). The weight ratio of right to left ventricles plus interventricular septum, myocyte diameter, cross-sectional area, and free wall thickness in right and left ventricles were measured.

RESULTS

Despite the same polycythemia, the right ventricle pressure (P <.05) and ratio of right to left ventricle pressures (P <.02) were higher after chronic hypoxia than intermittent hypoxia. The ratio of heart weight to total body weight and the ratio of right to left ventricles plus interventricular septum was higher (P <.01) in chronic and intermittent hypoxia than in normoxia. Myocyte diameter was not different between the right and left ventricles in normoxia, whereas right ventricle myocytes were larger than left ventricle myocytes in chronic hypoxia (P <.05) and intermittent hypoxia (P <.0005). There was marked dilatation of right ventricle size (P <.001) and marked reduction of left ventricle (P <.001) size in chronic and intermittent hypoxia compared with normoxia. The total ventricular area (right ventricle plus left ventricle area) remained the same in all groups. The wall thickness ratio in chronic hypoxia and intermittent hypoxia was increased (P <.001) compared with normoxia in the right ventricle but not in the left ventricle.

CONCLUSIONS

Intermittent reoxygenation episodes do not induce a lesser ventricular hypertrophic response than observed with chronic hypoxia. The functional myocardial preconditioning consequence of intermittent reoxygenation is not supported by structural differences evident with the available techniques.

Clinically suspected constrictive pericarditis: MR imaging assessment of ventricular septal motion and configuration in patients and healthy subjects

PURPOSE

To assess ventricular septal motion and quantify the septal configuration in patients clinically suspected of having constrictive pericarditis (CP), and to compare these patients with healthy subjects and with patients who have other diastolic heart abnormalities such as restrictive cardiomyopathy (RCM).

MATERIALS AND METHODS

In 41 patients clinically suspected of having CP and 12 healthy subjects, magnetic resonance (MR) imaging yielded information about cardiac morphology and function. On short-axis cine MR images, septal motion was assessed, and the septal and left ventricular free wall (LVFW) radii of curvature were quantified and normalized to end systole. Abnormal diastolic septal motion was expressed in terms of the largest difference in normalized radius between the septum and the LVFW. Analysis of variance was used to identify significant differences in septal shape among subject groups.

RESULTS

Left-sided septal flattening was identified in 17 of the 21 patients with surgically proven CP, in none of the 20 patients without CP, and in none of the healthy subjects. CP without septal flattening was present on the left side (n = 1), on the right side (n = 1), and at the atrioventricular grooves (n = 2). Abnormal septal motion yielded a sensitivity of 81% (17 of 21 patients), specificity of 100% (20 of 20 patients), accuracy of 90% (37 of 41 patients), positive predictive value of 100% (17 of 17 patients), and negative predictive value of 83% (20 of 24 patients) in the detection of CP. The maximal difference in normalized radius of curvature between the septum and the LVFW in the patients with CP was significantly different from that in the patients without CP (P <.001) and that in the healthy subjects (P <.001).

CONCLUSION

Abnormal diastolic septal motion is a frequent phenomenon of CP. If present in patients suspected of having CP, this finding is helpful in distinguishing CP from RCM.

Ventricular septal flattening at end systole falsely predicts right ventricular hypertension in patients with ostium primum atrial septal defects

PURPOSE

To assess the reliability of ventricular septal position in predicting elevated right ventricular pressure (RVP) in patients with ostium primum atrial septal defects (ASD 1).

METHODS

Echocardiograms of 4 groups were retrospectively analyzed: Patients with ASD 1 and low RVP, patients with ASD 1 and high RVP, and 2 age-matched control groups: one with isolated ostium secundum atrial septal defects (ASD 2), and 1 with normal cardiac findings. End-systolic left ventricular sectional diameters along the midmitral diameter (D1) and a diameter orthogonal to it (D2) were measured off-line by a blinded observer. The ratio D2/D1, the eccentricity index (EI), was calculated; a higher index represents greater septal flattening.

RESULTS

The mean EI in the ASD 1 with low RVP group was significantly higher than both the group with ASD 2 and the healthy control group. The mean EI of the ASD 1 group with high RVP was significantly higher than the mean EI of the ASD 1 group with low RVP, although there was a poor correlation between EI and RVP in this group, r = 0.54.

CONCLUSION

The ventricular septum is flatter in the ASD 1 patients with low RVP than in an age-matched control group with ASD 2 and compared with an age-matched control group of healthy subjects, giving a false impression of elevated RVP in the ASD 1 group. Although the mean EI is significantly higher in the ASD 1 group with high RVP than in the group with low RVP, there is a poor correlation between EI and RVP, which limits the reliability of this index.

Major pulmonary embolism: review of a pathophysiologic approach to the golden hour of hemodynamically significant pulmonary embolism

Major pulmonary embolism (PE) results whenever the combination of embolism size and underlying cardiopulmonary status interact to produce hemodynamic instability. Physical findings and standard data crudely estimate the severity of the embolic event in patients without prior cardiopulmonary disease (CPD) but are unreliable indicators in patients with prior CPD. In either case, the presence of shock defines a threefold to sevenfold increase in mortality, with a majority of deaths occurring within 1 h of presentation. A rapid integration of historical information and physical findings with readily available laboratory data and a structured physiologic approach to diagnosis and resuscitation are necessary for optimal therapeutics in this "golden hour." Echocardiography is ideal because it is transportable, and is capable of differentiating shock states and recognizing the characteristic features of PE. Spiral CT scanning is evolving to replace angiography as a confirmatory study in this population. Thrombolytic therapy is acknowledged as the treatment of choice, with embolectomy reserved for those in whom thrombolysis is contraindicated.

A 2D finite element model of the interventricular septum under normal and abnormal loading

The interventricular septum is the structure that separates the left and right ventricles of the heart. Under normal loading conditions, it is concave to the left ventricle, but under abnormal loading the septum flattens and occasionally inverts. In the past, the septum has frequently been modelled as integral to the left ventricle with the effects of pressure from the right ventricle being ignored. Under abnormal loading, the septum has been described as behaving equivalent to a "flapping sail". There has been no consideration of structural behaviour under these conditions. A 2-D plane stress FE model of the septum was used to investigate the difference in structural behaviour of the septum during diastole between normal and abnormal loading. The biaxial stress patterns that develop are distinctively disparate. Under normal loading, the septum behaves much like a thick-walled cylinder subject to internal and external pressure, with the resulting stresses being circumferential tension and radial compression, both varying with radius. These stresses are very low throughout most of diastole. However, under abnormal loading, the septum behaves in an arch-like fashion, with high compressive stresses almost circumferential in direction, combined with radial compression. We conclude that right ventricular pressures cause bending effects in the wall of the heart, and that under abnormal loading, the compressive stresses that develop in the septum may lead to an understanding of certain, previously unexplained, pathological conditions.

Compression of interventricular septum during right ventricular pressure loading

The interventricular septum, which flattens and inverts in conditions such as pulmonary hypertension, is considered by many to be an unstressed membrane, in that its position is assumed to be determined solely by the transseptal pressure gradient. A two-dimensional finite element model was developed to investigate whether compression and bending moments (behavior incompatible with a membrane) exist in the septum during diastole under abnormal loading, i.e., pulmonary artery (PA) constriction. Hemodynamic and echocardiographic data were obtained in six open-chest anesthetized dogs. For both control and PA constriction, the measured left ventricular and right ventricular pressures were applied to a residually stressed mesh. Adjustments were made to the stiffness and end-bending moments until the deformed and loaded residually stressed mesh matched the observed configuration of the septum. During PA constriction, end-bending moments were required to obtain satisfactory matches but not during control. Furthermore, substantial circumferential compressive stresses developed during PA constriction. Such stresses might impede septal blood flow and provoke the unexplained ischemia observed in some conditions characterized by abnormal septal motion.

Quantitative assessment of independent contributions of pericardium and septum to direct ventricular interaction

In the intact animal, it is difficult to discriminate between the independent effects of series and direct ventricular interaction (DI) or the individual contributions of the pericardium and septum to DI. Left ventricular (LV) venous return (LVVR) and right ventricular (RV) end-diastolic pressure (RVEDP) were varied independently in a right-heart bypass model. LV minor-axis diameters were measured, and the product of the two diameters was used as an index of LV volume (LVVI). At each RVEDP (0, 5, 10, and 15 mmHg), increased LVVR caused an increased LVVI. When RVEDP was increased, increased pump output was required to maintain a given LVVI. RV-to-LV pressure gain (DeltaLVEDP/DeltaRVEDP) reflects coupling and DI. With the pericardium closed, the gain was dependent on RVEDP; when RVEDP was increased from 0 to 5 mmHg, the gain was not statistically different from zero, indicating little or no DI. When RVEDP was increased from 10 to 15 mmHg, the gain was not statistically different from 1.0, indicating approximately 1:1 coupling of the ventricles. Opening the pericardium reduced the gain, but significant interaction remained. When the septal contribution was accounted for, the remaining interaction was eliminated. In conclusion, DI substantially affects LVEDP-volume relations. Considerable increases in RV output may be required to counterbalance increased constraint to LV filling. With the pericardium closed, RV-to-LV coupling is minimal when RVEDP is low and increases to 1:1 coupling when RVEDP is high. Opening the pericardium reduces DI, but significant septum-mediated interaction remains.

Echo-Doppler evaluation of left ventricular impairment in chronic cor pulmonale

The effects of acute right ventricular (RV) pressure and volume overloads on left ventricular (LV) filling are well known, while the significance of chronic RV pressure overload on LV function has been less studied. To evaluate the LV impairment, 30 patients with chronic cor pulmonale and pulmonary arterial hypertension secondary to chronic obstructive lung diseases (COLDs) were studied. All patients underwent respiratory tests and arterial blood gas assessment. An echo-Doppler examination was made to measure LV ejection fraction (EF), RV and LV end-diastolic and end-systolic diameters and areas, RV/LV area indexes, LV diastolic and systolic eccentricity indexes, mitral and tricuspid flow patterns, and mitral flow velocity in late and early diastole (A/E) indexes. A right heart catheterization was carried out to determine the resting mean pulmonary arterial pressure (mPAP). The data showed a marked enlargement of RV, compressing the left through a leftward shift of interventricular septum. A linear regression analysis detected a significant correlation between mPAP and the following parameters: RV/LV diastolic and systolic area indexes (r=0.75, p<0.0001; r=0.84, p<0.000, respectively), mitral A/E index (r=0.61, p<0.0005), and LV diastolic and systolic eccentricity indexes (r=0.93, p<0.0001; and r=0.83, p<0.0001). No correlations were found between echo-Doppler data and functional respiratory parameters. From these results, we conclude that chronic RV pressure overload induces LV filling impairment despite a normal systolic phase, due to septal leftward shift. In fact, chronic RV pressure overload distorts early diastolic LV geometry delaying LV filling phase, and the functional diastolic impairment of the LV is closely correlated to pulmonary hypertension levels.

Systolic excursion of the mitral annulus to assess septal function in paradoxic septal motion

To determine whether mitral valve annulus displacement (MVAD) can be used to assess septal contractility in patients with paradoxical septal motion, we assessed four atrioventricular regions (septum, lateral wall, anterior wall, and inferior wall) by MVAD in 80 consecutive patients. The patients were divided into five groups: group 1 (control) (n = 20), normal left ventricular (LV) systolic function; group 2 (n = 15), paradoxical septal motion resulting from left bundle branch block (LBBB) and normal segmental and global LV systolic function; group 3 (n = 19), paradoxical septal motion as a result of cardiac surgery, and normal segmental and global LV systolic function; group 4 (n = 11), paradoxical septal motion resulting from LBBB, dilated cardiomyopathy, and severely depressed LV systolic function; group 5 (n = 15), septal hypokinesis with either normal or mildly depressed global LV systolic function. In groups 1, 2, and 3, 80% to 100% of patients had septal and other regional MVAD > or = 1.0 cm. The average MVAD in group 4 (dilated cardiomyopathy), was significantly decreased ( < or = 0.8 cm) in all four regions (p < 0.01 compared with groups 1, 2, and 3). In group 5 (septal hypokinesis), the septal MVAD was > or = 1.0 cm in only 13% of the patients (p < 0.025 compared with groups 1, 2, and 3). In conclusion, patients with paradoxical septal motion caused by LBBB or cardiac surgery have preserved septal contractility when evaluated by MVAD.

Cross sectional Doppler echocardiography as the initial technique for the diagnosis of acute pulmonary embolism

OBJECTIVE

To determine the value of cross sectional Doppler echocardiography and derived indices of right ventricular pressure and function in the initial diagnosis of pulmonary embolism.

BACKGROUND

Most deaths from acute pulmonary embolism occur because of a delay in diagnosis. Ventilation-perfusion scans are not sufficiently sensitive, whereas angiography is invasive and associated with complications. The use of cross sectional Doppler echocardiography to assess acute changes in right ventricular filling pressure and function, and in pulmonary arterial systolic pressure and its relation to embolism has not been studied in a large population.

METHODS

60 consecutive patients with acute symptoms or haemodynamic instability suggestive of pulmonary embolism were studied. Confirmatory investigations included a ventilation-perfusion scan (36 patients), angiography (18 patients), surgery (5 patients), or necropsy (5 patients).

RESULTS

There was evidence of right ventricular pressure or volume overload in all. This took the form of increased right ventricular end diastolic diameter and leftward bulging of the interventricular septum in diastole (56 patients); tricuspid valve regurgitation (56 patients) with the peak velocity of the regurgitant jet > 2.6 m/s; and a low collapse index for the inferior vena cava of < 40%, indicating raised mean right atrial pressure (in 49 patients). Intracardiac or pulmonary thrombi were visualised in 10 patients. In 14 patients treatment was undertaken on the basis of the echocardiographic signs alone. Four of them (with visible thrombi) recovered: the other 10 died. Lung emboli were demonstrated in 4 of 5 patients in whom necropsy was performed.

CONCLUSIONS

Cross sectional Doppler echocardiography is a sensitive technique for the rapid identification of right ventricular overload in acute pulmonary embolism. It enables further investigations on treatment to be appropriately directed without delay. Resolution of emboli can also be assessed by serial measurement of the described indices.

Ischemia right ventricular dysfunction

For many years ischemic heart disease involving the right ventricle had received little attention. During the last 15 years, the initial works of Cohn, Isner, and others spawned a number of clinical and experimental studies that extended the understanding of the pathophysiology of ischemia in the right ventricle. Most of the work has been done in the setting of acute myocardial infarction, and information is still lacking in other conditions, such as chronic ischemic heart disease and perioperative right ventricular dysfunction. Acute right ventricular infarction rarely occurs in the absence of left ventricular necrosis and in most cases is the extension of an inferior left ventricular infarct. The majority of patients with right ventricular infarction only exhibit subtle signs of ischemic dysfunction. Elevated right atrial pressure is found only in the typical syndrome of elevated venous pressure; low output syndrome can be found only in 20% of the cases, and cardiogenic shock secondary to right ventricular necrosis is found only in 10%. It is also important to note that there is not a clear correlation between the severity of ischemic right ventricular dysfunction and the necrotic area. The discrepancy may be due to ischemia without necrosis of the right ventricular wall (stunned myocardium), but the intact pericardium and the necrosis of the interventricular septum may also play an important role. In the most severe form of ischemic right ventricular dysfunction, the entire right ventricular wall is akinetic. Right atrial, right ventricular, and pulmonary artery pressures become similar in magnitude and shape, and the pulmonary valve is opened during diastole, demonstrating a passive blood flow from the right atrium to the left ventricle through the low resistance pulmonary capillary bed. Volume loading, administration of dopamine or dobutamine, and careful use of vasodilators under hemodynamic monitoring are the therapeutic measures to control the severe forms of acute ischemic right ventricular dysfunction. The use of thrombolytic agents has decreased the incidence of right ventricular dysfunction after acute myocardial infarction. Mortality is high in the severe forms of acute ischemic right ventricular dysfunction, but after discharge from hospital the prognosis is good and right heart failure is unusual, even in those patients with shock during the first days of evolution of the infarct.

Effect of the pericardium on systolic ventricular interdependence in the dog

Systolic ventricular interdependence, whereby changes in left ventricular (LV) ejection alter right ventricular (RV) ejection, has been described. It is unclear, however, whether this interaction is influenced by pericardial volume constraint or by myocardial mechanical coupling. We hypothesized that if mechanical coupling were the primary factor determining systolic ventricular interdependence then it should be unaltered by the presence or absence of an intact pericardium, but affected by changes in LV end-systolic volume. We tested this hypothesis by observing the changes in RV stroke volume (SVrv) and peak systolic pressure (PSPrv) during a single LV isovolumic contraction under conditions of normal or increased (1.3 x normal) RV end-diastolic volume with and without an intact pericardium. In 10 anesthetized, open-chested dogs SVrv was derived from the integrated pulmonary arterial flow probe signal and RV ejection fraction (EFrv) was derived from the thermodilution plateau method and a rapidly responsive thermistor in the pulmonary artery. Right ventricular end-diastolic volume was considered to be the ratio of SVrv to EFrv. Left ventricular isovolumic contraction increased SVrv and PSPrv during all conditions (P < .01). However, PSPrv increased more when the pericardium was intact (P < .05). These data suggest that LV ejection can enhance SVrv and that this interaction is not appreciably altered by volume loading or the presence of an intact pericardium. Pericardial interactions may alter PSPrv but do not affect SVrv.

The importance of pericardial constraint in experimental pulmonary embolism and volume loading

To clarify the magnitude of the contribution of pericardial constraint to the hemodynamic deterioration that is observed during acute pulmonary embolism, hemodynamics and chamber dimensions (sonomicrometry) were measured during pulmonary embolization and subsequent volume loading in six anesthetized and instrumented open-chest, open-pericardium dogs. Embolization markedly increased peak right ventricular systolic pressure (38 +/- 5 mm Hg before embolism to 64 +/- 12 mm Hg after repeated embolization, p less than 0.05). However, right ventricular stroke volume decreased by only an insignificant amount (17 +/- 7 ml to 15 +/- 6 ml, p = not significant). Indices of left ventricular end-diastolic volume (left ventricular area = anteroposterior x septum-to-left ventricle free wall diameters) and stroke work (stroke work = area of the left ventricular pressure-area loop) were also similar before and after repeated embolization. Volume loading after repeated embolization resulted in increased right ventricular stroke volume (15 +/- 6 ml to 20 +/- 4 ml, p = 0.06), left ventricular area (3320 +/- 600 mm2 to 3470 +/- 580 mm2, p less than 0.05) and stroke work (261 +/- 158 mm Hg to 425 +/- 170 mm Hg x mm2, p less than 0.05). These results are in marked contrast to those in a previously reported study in a closed-chest and closed-pericardium model in which there was a decrease in left ventricular preload and systolic function after similar embolization-induced right ventricular pressure loading. Moreover, there was a further decrease in these parameters as a result of volume loading after embolism in the closed pericardium experiments. In conclusion, pericardial constraint contributes to hemodynamic deterioration during both acute right ventricular pressure loading and subsequent volume loading. The hemodynamic response to both interventions in the intact animal is determined not only by the degree of right ventricular dysfunction but also by the degree of direct ventricular interaction.

Doppler echocardiographic demonstration of the differential effects of right ventricular pressure and volume overload on left ventricular geometry and filling

To compare the effects of isolated right ventricular pressure and volume overload on left ventricular diastolic geometry and filling, 11 patients with primary pulmonary hypertension, 11 patients with severe tricuspid regurgitation due to tricuspid valve resection and 11 normal subjects were studied with use of Doppler echocardiographic techniques. Right ventricular systolic overload in primary pulmonary hypertension resulted in substantial leftward ventricular septal shift that was most marked at end-systole and early diastole and decreased substantially by end-diastole. Right ventricular diastolic overload after tricuspid valve resection resulted in maximal leftward ventricular septal shift at end-diastole sparing end-systole and early diastole. The early diastolic distortion of left ventricular geometry associated with right ventricular pressure overload resulted in prolongation of isovolumetric relaxation of the left ventricle (129 +/- 39 ms) and a reduction in early diastolic filling compared with values in normal subjects. Late diastolic distortion of left ventricular geometry associated with right ventricular volume overload had no influence on the duration of left ventricular isovolumetric relaxation (52 +/- 32 ms) but caused a reduction in the atrial systolic contribution to late diastolic filling of the left ventricle compared with values in normal subjects. In patients with right ventricular pressure overload, 52 +/- 16% of left ventricular filling occurred in early diastole compared with 78 +/- 11% in patients with right ventricular volume overload (p less than 0.001). The differential effects of systolic and diastolic right ventricular overload on the pattern of left ventricular filling appear to be related to the timing of leftward ventricular septal displacement.

Alterations in transesophageal pulsed Doppler indexes of filling of the left ventricle after pericardiotomy

The impact of pericardial constraint on patterns of left ventricular filling was measured by transesophageal pulsed Doppler echocardiography in 30 patients undergoing elective nonvalvular cardiac surgery. Peak early left ventricular filling velocity increased from 0.52 +/- 0.11 to 0.56 +/- 0.15 m/s (p less than 0.05) and early left ventricular filling fraction increased from 60 +/- 9% to 65 +/- 9% (p less than 0.005) after pericardiotomy. The study group was retrospectively subdivided into two groups based on the prepericardiotomy mean right atrial pressure, an index of intrapericardial pressure and hence pericardial constraint. In 13 patients with a mean right atrial pressure less than 6 mm Hg, no significant changes in early left ventricular filling were evident after pericardiotomy. In 17 patients with a mean right atrial pressure greater than or equal to 6 mm Hg indicative of a greater degree of pericardial constraint before pericardiotomy, significant increases in peak early filling velocity (0.52 +/- 0.13 to 0.57 +/- 0.19 m/s, p less than 0.05), peak early filling rate (4.29 +/- 0.67 to 4.66 +/- 0.86 stroke volumes/s, p less than 0.05) and early left ventricular filling fraction (57 +/- 7% to 63 +/- 8%, p less than 0.001) were measured after pericardiotomy. Thus, the pericardium does constrain early left ventricular filling and its effects are more pronounced in patients with an elevated right atrial pressure.

Reduced atrial contribution to left ventricular filling in patients with severe tricuspid regurgitation after tricuspid valvulectomy: a Doppler echocardiographic study

Patients undergoing valvulectomy for isolated tricuspid valve endocarditis offer the unique opportunity to study the effects of acquired right ventricular volume overload on left ventricular filling in persons free of pulmonary hypertension and preexisting left heart disease. Eleven patients who had undergone total or partial removal of the tricuspid valve were compared with 11 age-matched control subjects; Doppler echocardiographic techniques were used to quantify changes in left ventricular filling and to relate them to changes in left ventricular and left atrial geometry caused by right ventricular and right atrial distension. The late diastolic fractional transmitral flow velocity integral, a measure of the left atrial contribution to left ventricular filling, was significantly decreased in patients undergoing tricuspid valvulectomy compared with control subjects (0.22 +/- 0.11 versus 0.32 +/- 0.09; p less than 0.04). Severe tricuspid regurgitation in these patients resulted in marked right atrial distension, reversal of the normal interatrial septal curvature and compression of the left atrium such that left atrial area was significantly smaller than in control subjects (5.9 +/- 2.2 versus 8.6 +/- 1.2 cm2/m2; p less than 0.005). Acting as a receiving chamber, the left ventricle was maximally compressed by the volume-overloaded right ventricle in late diastole, coincident with the timing of atrial systole, resulting in a significant increase in the left ventricular eccentricity index compared with that in control subjects (1.35 +/- 0.14 versus 1.03 +/- 0.1; p less than 0.001). Thus, right ventricular volume overload due to severe tricuspid regurgitation results in left heart geometric alterations that decrease left atrial preload, impair left ventricular receiving chamber characteristics and reduce the atrial contribution to total left ventricular filling.

Regional distribution of the cardiac output and renal responses to atrial natriuretic peptide infusion in rabbits with congestive heart failure

1. A biventricular, low-output congestive cardiomyopathy was induced in 19 rabbits by administering adriamycin (16 mg/kg). The effects of alpha-rat atrial natriuretic peptide (ANP) infused at 0.1, 0.2 and 0.4 micrograms/kg per min, were then examined in terms of (i) central haemodynamics (ii) regional blood flow (iii) renal function and (iv) plasma norepinephrine and plasma renin. 2. In this dose range, ANP produced progressive and significant falls in stroke volume, cardiac output and mean arterial pressure, owing to a fall in venous return. The heart rate response to this was blunted. 3. Using radiolabelled microspheres, significant falls in the perfusion of cutaneous, gastrointestinal and musculoskeletal tissues were observed, due to reduced vascular conductances in these beds. These changes were accompanied by activation of the sympathetic nervous system as evidenced by a progressive rise in plasma norepinephrine. A significant increase in plasma renin was only observed with the highest infusion of ANP. 4. Renal blood flow was maintained in the face of a falling mean arterial pressure and cardiac output, but diuretic and natriuretic effects were absent. 5. It was concluded that the dominant influence of ANP infusion in this model of heart failure appeared to be a reduction in cardiac preload with detrimental overall haemodynamic consequences.

Effects of acute intrathoracic pressure changes on left ventricular geometry and filling

Acute changes in intrathoracic pressure (ITP) affect left ventricular (LV) function. It has been suggested that this functional impairment could be the result of an alteration in LV filling caused by a reduction in LV compliance induced by the rearrangement of biventricular geometry that occurs under these conditions. Therefore, to evaluate the effects of an acute increase or decrease in ITP on LV geometry and filling, we used two-dimensional and Doppler echocardiography to study 25 normal volunteers both during the Müller maneuver (acute decrease in ITP induced by a forced inspiration against a closed airway) and during continuous positive airway pressure breathing. During both maneuvers LV geometry was altered as demonstrated by the significant increase in the normalized curvature radius of the interventricular septum and the unchanged curvature radius of the LV free wall. LV filling was altered during both maneuvers as demonstrated by significant decreases in early peak flow velocity, early-to-late peak flow velocity ratio, and early deceleration rate. Thus, during maneuvers that acutely decrease or increase ITP, alterations in LV geometry occur. These acute distortions of LV geometry may be one of the mechanisms responsible for alterations in LV filling.

Acute reduction in functional infarct expansion with late coronary reperfusion: assessment with quantitative two-dimensional echocardiography

Reperfusion performed too late to salvage myocardium decreases chronic infarct expansion in experimental animals. However, the acute effects of delayed reperfusion are not known. Twenty-two dogs underwent 3 (n = 8), 4 (n = 8) or 6 h (n = 6) of circumflex artery occlusion followed by 3 h of reperfusion. Effects of reperfusion on diastolic expansion were assessed in two ways: 1) change in mean radius of curvature of the infarct segment, and 2) change in the ratio of the length of the diameter from the center of the infarct zone to the opposite wall (septal-lateral diameter) to the length of the diameter perpendicular to this (anteroposterior diameter). Effects on systolic expansion were examined with quantitative two-dimensional echocardiographic systolic thickening analysis. Delayed reperfusion produced an immediate decrease in diastolic infarct expansion. The ratio of septal-lateral/anteroposterior diameters, which had increased with occlusion from a preocclusion baseline of 0.98 +/- 0.06 to 1.13 +/- 0.08 (p less than 0.001), decreased with reperfusion to 1.02 +/- 0.07 at 15 min and 1.03 +/- 0.08 at 3 h of reperfusion (p = 0.001). This was due solely to a decrease in the septal-lateral diameter. The radius of curvature of the infarcted segment increased from 2.1 +/- 0.5 cm before reperfusion to 2.74 +/- 0.8 cm at 15 min and 2.6 +/- 0.85 cm at 3 h of reperfusion (p = 0.009). This occurred despite a significant (13.6%) decline in end-diastolic cavity area and is compatible with flattening of the reperfused infarct region. Systolic infarct expansion also improved slightly.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative two-dimensional echocardiography in massive pulmonary embolism: emphasis on ventricular interdependence and leftward septal displacement

In 14 patients requiring aggressive therapy for circulatory failure resulting from massive pulmonary embolism, hemodynamic and two-dimensional echocardiographic data were obtained at bedside (acute phase) and again after circulatory improvement (intermediate phase) and during recovery. The acute stage was characterized by a low cardiac output state despite inotropic support (cardiac index 1.9 +/- 0.6 liters/min per m2) associated with increased right atrial pressure (12.4 +/- 4.2 mm Hg), increased right ventricular end-systolic and end-diastolic area (12.4 +/- 3.4 and 15.4 +/- 4.1 cm2/m2, respectively) and reduced right ventricular fractional area contraction (20.1 +/- 8.6%). Two-dimensional echocardiography also revealed interventricular septal flattening at both end-systole and end-diastole and markedly decreased left ventricular end-diastolic dimensions. Left ventricular fractional area contraction remained normal. Hemodynamic improvement occurred during the intermediate phase as shown by restoration of cardiac index (3.3 +/- 0.6 liters/min per m2), decrease in right atrial pressure (8.3 +/- 4.8 mm Hg), reduction in right ventricular end-systolic area (9.0 +/- 3.6 cm2/m2 at the intermediate stage and 6.1 +/- 1.8 cm2/m2 at recovery) and end-diastolic area (10.5 +/- 3.6 cm2/m2 at the intermediate stage and 8.9 +/- 2.9 cm2/m2 at recovery) and improvement in right ventricular fractional area contraction (31.5 +/- 16.4%). The interventricular septum progressively returned to a more normal configuration at both end-systole and end-diastole, and left ventricular diastolic dimension steadily increased. It is concluded that circulatory failure secondary to massive pulmonary embolism was mediated through a profound decrease in left ventricular preload, resulting from both pulmonary outflow obstruction and reduced left ventricular diastolic compliance.(ABSTRACT TRUNCATED AT 250 WORDS)