Biventricular Volumes Research Articles

Circulation: Clinical Summaries

<i>Circulation:</i> Clinical Summaries

Assessment Of Cardiac Inflammation And Injury Following Prolonged Exercise Using Cardiovascular Magnetic Resonance (CMR) Imaging

PURPOSE: Myocardial inflammation may be a potential mechanism for the release of troponin and NTproBNP following a Marathon. CMR has not been previously used to detect and quantify myocardial inflammation and fibrosis pre- and post-Marathon. METHODS: CMR was performed in 18 athletes 24hrs pre and 6 hours post a Marathon run. Each scan was performed on a 1.5T Siemens Avanto scanner using a 4 channel body array coil. Myocardial structure and function was assessed using breath hold SSFP cine imaging in long and short axis views. The presence of myocardial inflammation and oedema was assessed using STIR imaging and a 3-4 minute spin echo sequence immediately post 0.1mmol intravenous gadolinium-DTPA to assess relative gadolinium enhancement. Inversion recovery segmented-FLASH imaging with TI adjusted to null normal myocardium to highlight regions of fibrosis was used to image delayed enhancement. Each participant had bloods drawn for TnI, NT-proBNP, and CRP at baseline, immediately post and 6 hours after the run. Each CMR scan was analyzed for wall thickness per segment, volumes and function, myocardial oedema. Delayed enhancement images were analysed using Medis software. RESULTS: Biventricular volumes, stroke volume, ejection fraction, and mass were unchanged pre and 6 hrs post marathon. The majority of subjects were found to have a rise in BTproBNP levels immediately and 6 hours after the race as well as elevations in TnI above the level of cut off for myocardial infarction (P=0.001). There were no focal regions of visual signal increase on the STIR images in any of the 18 subjects. Global myocardial oedema was predefined using a cut off ratio of 1.9 comparing SI of myocardium to skeletal muscle on STIR imaging, and a relative 45% increase in the SI myocardium/skeletal muscle immediately post intravenous gadolinium on relative gadolinium enhancement imaging (rGE). No subject reached these cut off values. None had any visual myocardial fibrosis on late enhancement imaging or using automated software. CONCLUSIONS: Serum markers of myocardial cell damage post ultra endurance exercise are not associated with CMR detectable levels of myocardial oedema, inflammation or scarring, suggesting lower degrees of myocardial damage than in patients with acute myocardial infarction, inspite of similar levels of troponin elevation.

Feasibility and reproducibility of biventricular volumetric assessment of cardiac function during exercise using real‐time radial k‐t SENSE magnetic resonance imaging

To assess the feasibility and reproducibility of real-time radial k-t sensitivity encoding (SENSE) magnetic resonance imaging (MRI) for biventricular volumetric assessment during exercise. In all, 12 healthy young adults underwent MRI at rest and during supine exercise at three different workload intensities. Biventricular volumes and function were assessed with 1) a radial k-t SENSE real-time sequence and 2) a scanner vendor supplied (standard) real-time sequence. Global image quality, motion fidelity, and agreement in right ventricular (RV) and left ventricular (LV) stroke volume (SV) as a surrogate measure for accuracy were assessed. Exercise MR was repeated within 1 month for assessment of reproducibility. Imaging scores were superior for radial real-time k-t SENSE images (P < 0.001). Agreement in RV and LV SV during exercise was better with radial k-t real-time (SD of difference +/-3.43 vs. +/-8.97 mL; P < 0.001). Agreement in cardiac output (CO) in the same subject at two different imaging sessions was better for radial k-t SENSE. This was significant for the CO calculated for the RV (SD of difference +/-0.6 vs. +/-0.95 L/min; P = 0.01) and LV (+/-0.45 vs. +/-0.92 L/min; P < 0.001). Radial k-t SENSE real-time imaging represents a feasible and reproducible imaging technique for biventricular assessment during exercise.

Normal biventricular function, volumes, and mass in children aged 8 to 17 years

To assess normal values for biventricular function, volumes, and mass with current cardiovascular magnetic resonance (CMR) imaging sequences in children. Included in the study were 60 healthy children aged 8-17 years. A short axis set of contiguous slices was acquired with CMR imaging employing steady-state free precession. Biventricular end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and mass were determined. Uni- and multivariate linear regression analyses were performed to study the interrelation of age, gender, and body surface area (BSA) on biventricular volumes and mass. The coefficient of variation was calculated for intra- and interobserver variability. EF did not differ between boys and girls (mean LV-EF 69+/-(SD) 5%, mean RV-EF 65+/-5%). BSA had good (EDV, mass) and modest (ESV) correlation with biventricular measurements. Gender appeared a significant modifier of these relations, whereas age had no independent contribution. The intra- and interobserver coefficient of variation was in the range 2.1%-13.9% for biventricular EDV, ESV, and mass. This study reveals gender-specific normative data for biventricular function, volumes, and mass in children age 8-17 years that can be used as reference data in the follow-up of pediatric cardiac patients.

Intra-observer and interobserver variability of biventricular function, volumes and mass in patients with congenital heart disease measured by CMR imaging

Cardiovascular magnetic resonance (CMR) imaging provides highly accurate measurements of biventricular volumes and mass and is frequently used in the follow-up of patients with acquired and congenital heart disease (CHD). Data on reproducibility are limited in patients with CHD, while measurements should be reproducible, since CMR imaging has a main contribution to decision making and timing of (re)interventions. The aim of this study was to assess intra-observer and interobserver variability of biventricular function, volumes and mass in a heterogeneous group of patients with CHD using CMR imaging. Thirty-five patients with CHD (7-62 years) were included in this study. A short axis set was acquired using a steady-state free precession pulse sequence. Intra-observer and interobserver variability was assessed for left ventricular (LV) and right ventricular (RV) volumes, function and mass by calculating the coefficient of variability. Intra-observer variability was between 2.9 and 6.8% and interobserver variability was between 3.9 and 10.2%. Overall, variations were smallest for biventricular end-diastolic volume and highest for biventricular end-systolic volume. Intra-observer and interobserver variability of biventricular parameters assessed by CMR imaging is good for a heterogeneous group of patients with CHD. CMR imaging is an accurate and reproducible method and should allow adequate assessment of changes in ventricular size and global ventricular function.

Ventrículos comuns por Comunicação Interventricular (CIV) de 52 mm de extensão

Eleven-year-old boy undergoing pulmonary banding at the age of one month due to heart failure. He had normal physical growth, good exercise tolerance and normal arterial saturation. On physical examination, grade 3/6 systolic murmur at the LSB. On ECG, biventricular volume overload, and on chest X-ray, close to normal cardiac silhouette with slightly increased pulmonary vascularity. Atrioventricular and ventriculoarterial concordance with ventricles of similar size and large 52-mm discontinuity of the interventricular septum up to the apex (common ventricle). Surgical ventricular separation implies a high risk of residual defect, in addition to contractile dysfunction. Maintenance of the expectant medical management was chosen.

Comparison of Methods to Measure Heart Size Using Noncontrast-Enhanced Computed Tomography

Left ventricular (LV) mass is a useful independent predictor of cardiovascular events. We sought to develop a new correlate of LV mass using noncontrast-enhanced cardiac computed tomography (NCE-CCT). We assessed 22 different ventricular measurements made with NCE-CCT in 60 participants in the Multi-Ethnic Study of Atherosclerosis. The primary outcome was the correlation between the NCE-CCT measurements and magnetic resonance imaging (MRI)-derived LV mass. Correlation coefficients (r) for the 22 NCE-CCT techniques in comparison to MRI-derived LV mass ranged from 0.12 to 0.80, with 14 of the 22 techniques having r > 0.7. The highest correlation was achieved using the modified Simpson Rule method to determine the biventricular volume (r = 0.80; P < 0.001). Interrater reliability was good, with intraclass correlation coefficients of 0.84 to 0.90 for the best (r > 0.75) NCE-CCT methods. Noncontrast-enhanced cardiac computed tomography measurements of both biventricular volume and LV volume correlated well with MRI-derived LV mass in a population free of clinical cardiovascular disease.

Reproducibility of MRI measurements of right ventricular size and function in patients with normal and dilated ventricles

To determine the inter- and intraobserver reproducibility of cardiac magnetic resonance (CMR)-derived measurements of right ventricular (RV) mass, volume, and function in patients with normal and dilated ventricles. CMR studies of 60 patients in three groups were studied: a normal RV group (N = 20) and two groups with RV dilation-atrial septal defect (ASD) (N = 20) and repaired tetralogy of Fallot (TOF) (N = 20). Two independent observers analyzed each study on two separate occasions. Inter- and intraobserver reproducibility of biventricular mass, volume, ejection fraction (EF), and stroke volume (SV) measurements were calculated. High intraclass correlation coefficients (ICC) were found for interobserver (ICC = 0.94-0.99) and intraobserver (ICC = 0.96-0.99) comparisons of RV and left ventricular (LV) mass, volume, and SV measurements. RV and LV EF measurements were less reproducible (ICC = 0.79-0.87). RV mass measurements were significantly less correlated than the respective LV measurements. Small but statistically significant differences in correlation were noted in RV measurements across groups. Except for RV mass, inter- and intraobserver reproducibility of RV size and function measurements is high and generally comparable to that in the LV in patients with both normal and dilated RV.

Cardiac Status after Childhood Growth Hormone Treatment of Turner Syndrome

In Turner syndrome (TS), GH treatment is well established. Data on cardiac status after discontinuation of treatment are scarce. This study aimed to assess biventricular size and function in TS at least 6 months after discontinuation of GH treatment. TS patients and healthy women prospectively underwent cardiac magnetic resonance imaging. Ventricular two-dimensional tomographic cine data were acquired to obtain biventricular volume, mass, and ejection fraction. Atrioventricular valve flow measurements were performed using a two-dimensional flow-sensitized sequence. Flow velocity curves were calculated and indices of biventricular diastolic filling were derived. Thirty-one patients [mean (sd) age 20 (2) yr, body surface area 1.75 (0.15) m(2), 5 (2) yr after GH discontinuation] and 23 normal control women [age 21 (2) yr, body surface area 1.80 (0.13) m(2)] were included. Compared with controls, patients had smaller mean end-diastolic volumes [right ventricle (RV), 84 (11) ml/m(2) vs. 79 (10), P = 0.02; left ventricle (LV), 81 (10) vs. 72 (9), P < 0.001], end-systolic volumes [RV 38 (7) ml/m(2) vs. 36 (6), P = 0.04; LV 34 (5) vs. 29 (4), P < 0.001], and stroke volumes [RV 46 (6) ml/m(2) vs. 43 (6), P = 0.03; LV, 47 (7) vs. 44 (4), P = 0.02]. Patients had a higher mean heart rate [79 (13) beats/min vs. 71 (10), P < 0.05]. Biventricular ejection fraction, mass, cardiac output, and diastolic filling pattern were comparable. After discontinuation of GH treatment TS patients showed no myocardial hypertrophy and well-preserved biventricular function. Ventricular volumes were smaller in Turner patients, compared with controls, whereas mean heart rate was higher. These last observations may be part of the natural development in TS and not linked to GH treatment, which at this point we consider safe.

Right ventricular restrictive physiology in repaired tetralogy of Fallot is associated with smaller respiratory variability

Background Long-term outcomes of patients with repaired tetralogy of Fallot (TOF) are known to be related with right ventricular (RV) volume overload, severity of pulmonary insufficiency (PI) and the type of outflow repair. Right ventricular restrictive physiology (RVRP) has also been reported to interfere with several factors influencing the late result in repaired TOF patients. However, the mechanism and physiology of this unique myocardial property in the chronically overloaded right ventricle are not yet clearly understood. Methods We investigated 43 patients after repair of TOF to assess the relationships among biventricular diastolic function, volume characteristics, and influence of respiratory effort. The patients were classified into 3 groups; 15 patients with RVRP and significant PI (RP group, 35%), 19 without RVRP in the presence of significant PI (NR + PI group, 44%), and 9 without RP or significant PI (NR − PI group, 21%). Doppler spectrals obtained by echocardiography from systemic and pulmonary veins, main pulmonary artery (MPA), and both ventricular inlets, and biventricular diastolic function were compared according to the respiratory cycle. Results The RP group revealed higher pulmonary venous systolic/diastolic flow ratio (S/D ratio) and the NR + PI group showed larger velocity-time integral (VTI) ratio of total regurgitant/antegrade flow at the MPA and more respiratory variability in the systemic vein. Conclusion RP is associated with less volume overload of the RV and smaller respiratory variability is also associated with the restrictive RV. The diastolic function and volume status of the RV may influence the diastolic properties of the left heart.

Routine breath-hold gradient echo MRI-derived right ventricular mass, volumes and function: accuracy, reproducibility and coherence study

Right ventricular (RV) dysfunction is a predictor of poor outcome in patients with heart disease. Conventional imaging modalities fail to assess RV volumes accurately. We sought to assess the accuracy and reproducibility of routine breath-hold gradient echo magnetic resonance imaging (MRI)-derived RV mass, volumes and function. We assessed: (1) The accuracy of in vivo MRI-derived RV mass in comparison to the RV weight in 9 minipigs. (2) Intra- and inter-observer reproducibility of RV mass, end-diastolic (EDV) and end-systolic (ESV) volumes and ejection fraction (EF) in 15 normal volunteers and 10 patients with heart disease. (3) Inter-study reproducibility of the former parameters in 25 coronary artery disease patients. (4) The correlation between right and left ventricular stroke volumes in the total population. Strong statistically significant correlations were found between: (1) MRI-derived RV mass and RV weight (r = 0.98, bias = 2.5 g), (2) Intra-observer measurements of RV mass (r = 0.96, bias = 0.5 g), EDV (r = 0.99, bias = -1.5 ml), ESV (r = 0.98, bias = 0.1 ml) and EF (r = 0.92, bias = -1.4%), (3) Inter-observer measurements of RV mass (r = 0.95, bias = 1.1 g), EDV (r = 0.98, bias = -1.1 ml), ESV (r = 0.98, bias = 1.2 ml) and EF (r = 0.87, bias = -1.9%), (4) Inter-study measurements of RV mass (r = 0.91, bias = -0.1 g), EDV (r = 0.96, bias = 3.8 ml), ESV (r = 0.98, bias = 0.3 ml) and EF (r = 0.90, bias = 0.9%), (5) MRI-derived right and left ventricular stroke volumes (r = 0.87). The assessment of the RV mass, volumes and function by routine breath-hold gradient echo MRI is accurate and highly reproducible. The correlation between left and RV MRI-derived stroke volumes indicates excellent coherence of simultaneous bi-ventricular volume measurements.

Assessment of biventricular remodeling by magnetic resonance imaging after successful primary stenting for acute myocardial infarction

Inferior acute myocardial infarction (AMI) is associated with a better outcome compared with anterior AMI, even in the presence of comparable infarct size. Whether left ventricular remodeling, a major predictor of poor outcome, and right ventricular (RV) remodeling depend on the site of an AMI remains unknown. Biventricular volumes were assessed by magnetic resonance imaging 7 ± 2 days and 3.4 ± 0.3 months after successful primary stenting in 51 consecutive patients with inferior or anterior AMI. This study documents RV involvement and biventricular reverse remodeling in patients with inferior AMI in the absence of RV infarction, as opposed to those with anterior AMI who show progressive biventricular remodeling.

Secretion of A-type and B-type natriuretic peptides into the bloodstream and pericardial space in children with congenital heart disease

Objective To determine the secretion of A-type and B-type natriuretic peptides into the bloodstream and pericardial space in children with congenital heart disease. Methods Plasma and pericardial fluid samples were obtained from 77 patients undergoing total correction for congenital heart disease. All patients underwent detailed right-sided and left-sided cardiac catheterization preoperatively. Results A-type natriuretic peptide levels in pericardial fluid were lower than those in plasma (33.0 ± 23.1 versus 39.8 ± 33.6 pg/mL, P < .05), and B-type natriuretic peptide levels in pericardial fluid showed marked elevations compared with those in plasma (231.9 ± 305.6 versus 19.8 ± 29.3 pg/mL, P < .0001). The A-type and B-type natriuretic peptide levels in plasma correlated with those in pericardial fluid ( R = .522, P < .0001; R = .595, P < .0001). For A-type and B-type natriuretic peptide levels in plasma, the relation with biventricular volume had the highest correlation ( R = .669, P < .0001; R = .652, P < .0001). The patients with a pulmonary-to-systemic flow ratio greater than 2 (n = 19) had high levels of natriuretic peptides not only in plasma (58.3 ± 43.2, 40.5 ± 49.4 pg/mL, P < .05) but also in pericardial fluid (44.4 ± 31.5, 287.2 ± 198.5 pg/mL, P < .05), and higher correlation between A-type and B-type natriuretic peptide plasma levels and left ventricular volume ( R = .913, P < .0001; R = .787, P < .0001). Conclusions B-type natriuretic peptide is secreted not only into the bloodstream but also into the pericardial space in children with congenital heart disease. Natriuretic peptide levels in plasma correlated well with biventricular volume. The left ventricle was considered to be the main source of secreted natriuretic peptides in the patients with a pulmonary-to-systemic flow ratio greater than 2.

Biventricular response to supine physical exercise in young adults assessed with ultrafast magnetic resonance imaging

Simultaneous assessment of left ventricular (LV) and right ventricular (RV) response to exercise is limited with the current imaging modalities. Magnetic resonance imaging (MRI) techniques are now under development that allow near real-time evaluation of biventricular function under physical stress. This approach may open new avenues to study heart function in response to exercise in health and disease. The aim of this study was to evaluate biventricular response to supine physical exercise using ultrafast MRI. Biventricular volumes and function were examined in 16 healthy volunteers (mean age 18 ± 2 years) using an ultrafast MRI sequence at rest and during an exercise protocol on a MRI compatible bicycle ergometer. Exercise level was individualized at the workload corresponding to 60% of the maximal oxygen uptake. All subjects completed the exercise MRI examination, allowing functional evaluation. Stroke volume of both ventricles increased from rest to exercise (left ventricle, 89 ± 14 ml vs 102 ± 19 ml, p <0.05; right ventricle, 88 ± 14 ml vs 101 ± 16 ml, p <0.05). Ejection fraction also increased in both ventricles from rest to exercise (left ventricle, 63 ± 6% vs 74 ± 6%, p <0.05; right ventricle, 61 ± 6% vs 70 ± 6%, p <0.05). End-systolic volume of the left and right ventricles decreased from rest to exercise (left ventricle, −33 ± 12%, p <0.05; right ventricle, −25 ± 12%, p <0.05), whereas LV and RV end-diastolic volumes remained unchanged. The results fit well with current concepts of cardiac physiology, and therefore we conclude that ergometer-induced exercise MRI is a valid approach to assess physiologic changes in LV and RV function simultaneously.

Assessment of Right Ventricular and Right Atrial Systolic and Diastolic Performance Using Automated Border Detection.

Noninvasive assessment of right ventricular (RV) function is important clinically, but current techniques have limitations. Acoustic quantification (AQ) is an automated endocardial border detection technique that allows continuous determination of RV and right atrial (RA) area waveforms and may be useful for the assessment of RA and RV systolic and diastolic performance. Fifty patients (10 normal, 40 with RV pathology) were studied. Signal-averaged RA and RV AQ area waveforms were obtained and analyzed to compute parameters of diastolic and systolic function. All groups demonstrated significant diastolic dysfunction on the RA AQ waveform as manifested by a reduced percentage of passive atrial emptying and increased dependence on active atrial emptying. Abnormalities of diastolic performance were noted in all subgroups on RV AQ analysis as evidenced by a reduction in the percentage of ventricular filling occurring during early diastole and an increased contribution from active atrial contraction. This study demonstrates the feasibility of using automated analysis of signal-averaged RA and RV area waveforms for the evaluation of RV systolic and diastolic performance. This technique identified significant systolic and diastolic dysfunction in four groups of commonly seen right heart pathologies including biventricular heart failure, pulmonary hypertension, pressure and volume overloaded RVs, and biventricular hypertrophy.

Reproducibility of right and left ventricular volume measurements by electron-beam CT in patients with congestive heart failure.

The applicability and reproducibility of electron-beam computed tomography (EBCT) was tested to define left and right ventricular volumes in patients with congestive heart failure in a clinical setting. Ten patients (mean age 64 +/- 11 years) with dilated hearts and stable congestive heart failure (functional class III-IV) were studied. After determination of the individual circulation time, two serial short axis polytomographic EBCT studies were performed within a mean interval of 14.8 +/- 10 days. Following intravenous contrast administration, biventricular end-diastolic volumes (LVEDV, RVEDV), end-systolic volumes (LVESV, RVESV), and left ventricular muscle mass (LVMM) were determined using previously developed techniques. Adequate contrast opacification in both ventricular cavities was obtained in all patients at baseline and at follow-up. Values were 323.4 +/- 99.3 (mean +/- SD) and 332.6 +/- 105.4 ml for LVEDV, 249.3 +/- 75.6 and 250.5 +/- 79.3 ml for LVESV, 236.8 +/- 56.2 and 251.2 +/- 72.7 ml for RVEDV, 179.8 +/- 76.4 and 188.3 +/- 64.0 ml for RVESV, and 207.7 +/- 70.6 and 204.9 +/- 81.9 g for LVMM (p = NS, respectively, paired t-test). Linear regression analysis correlating biventricular volumes and left ventricular muscle mass measurements in the serial scans yielded r-values in the range of 0.89 to 0.95 and a small SEE. The SE of the mean differences between left and right ventricular ejection fraction measurements was 1 point, respectively. EBCT studies of ventricular volumes in patients with dilated hearts and congestive heart failure are highly reproducible and offer the potential for serial assessment of these patients in whom quantitation of ventricular volumes has been shown to be of prognostic value.

Temporal evaluation of left ventricular remodeling and function in rats with chronic volume overload.

The left ventricle (LV) significantly dilates and hypertrophies in response to chronic volume overload. However, the temporal responses in LV mass, volume, and systolic/diastolic function secondary to chronic volume overload induced by an infrarenal arteriovenous (A-V) fistula in rats have not been well characterized. To this end, LV end-diastolic pressure, size, and function (i.e., isovolumetric pressure-volume relationships in the blood-perfused isolated heart) were assessed at 1, 2, 3, 5, and 8 wk post-A-V fistula and compared with age-matched control animals. Progressive hypertrophy (192% at 8 wk), ventricular dilatation (172% at 8 wk), and a decrease in ventricular stiffness (257% at 8 wk) occurred in the fistula groups. LV end-diastolic pressure increased from a control value of 4.2 +/- 3.1 mmHg to a peak value of 15.7 +/- 3.6 mmHg after 3 wk of volume overload. A subsequent decline in LVEDP to 11.0 +/- 6.0 mmHg together with further LV dilation (169%) corresponded to a significant decrease in LV stiffness (222%) at 5 wk post-A-V fistula. Myocardial contractility, as assessed by the isovolumetric pressure-volume relationship, was significantly reduced in all A-V fistula groups; however, the compensatory remodeling induced by 8 wk of chronic biventricular volume overload tended to preserve systolic function.

Biventricular systolic function and mass studied with MR imaging in children with pulmonary regurgitation after repair for tetralogy of Fallot.

To study biventricular systolic function and mass of the heart in young patients with residual pulmonary regurgitation who had undergone surgical correction of tetralogy of Fallot. Transverse gradient-echo magnetic resonance (MR) images covering both ventricles were obtained in 19 patients who had undergone corrective surgery for tetralogy of Fallot at the age of 1.5 years +/- 1 and in 12 age-matched control subjects. In addition, MR velocity maps of the pulmonary artery were obtained. Biventricular volumes, ejection fraction and myocardial mass, and pulmonary flow volumes were measured. Exercise tests were performed in 17 patients. The right ventricular ejection fraction was lower (P < .001) and the right ventricular mass was higher (P < .0005) in patients than in control subjects; the left ventricular ejection fraction was lower (P < .0005) in patients and correlated statistically significantly with pulmonary regurgitation (r = -.68; P < .005). Exercise performance inversely correlated with pulmonary regurgitation (tau = -0.5; P = .01). In children who undergo early surgical repair of tetralogy of Fallot, residual pulmonary regurgitation correlates with biventricular systolic dysfunction and diminished exercise capacity. Despite successful surgical correction, right ventricular hypertrophy may persist.

Serial changes in left and right ventricular systolic and diastolic dynamics during the first year after an index left ventricular Q wave myocardial infarction

This study quantified serially biventricular emptying and filling after infarction and related these to changes in volume, muscle mass, wall stress and contractility. There are limited data on serial changes in ventricular dynamics after infarction. Forty patients had serial electron beam computed tomographic examinations during the first year after index Q wave infarction (21 anterior, 19 inferior), and global biventricular volumes, peak rates of emptying and filling and left ventricular muscle masses were quantified. Mean mid-left ventricular end-systolic wall stresses, rate-corrected velocities of circumferential shortening and two indexes of left ventricular contractility--the end-systolic wall stress/volume ratio and the end-systolic wall stress/rate-corrected velocity of circumferential shortening relation--were estimated in each instance. Patients with anterior infarction had an increase in biventricular chamber volume of 15% to 35% by 1 year. Global biventricular peak rates of emptying and filling were decreased by 20% to 30% from hospital discharge to 6 weeks but thereafter remained unchanged. Despite a significant increase in mean wall stresses, the end-systolic wall stress/volume ratio remained unchanged during the year. The rate-corrected velocities of circumferential shortening declined serially after anterior infarction but did so in proportion to the increase in mean wall stresses, consistent with no net change in left ventricular contractility. Patients with inferior infarction showed a trend toward similar changes, but the magnitudes did not reach significance. Left (and right) ventricular global peak rates of emptying and filling during the first year after infarction can be altered in the absence of additional ischemic injury but are more consistent with responses to changes in left ventricular afterload than changes in intrinsic ventricular performance or contractility. Serial changes in left ventricular afterload after infarction are largely due to progressive chamber enlargement and limited development of compensatory hypertrophy during the first year. Intrinsic global left ventricular contractile performance was not altered by postinfarction cardiac remodeling in the patients examined.

Physiology of cardiac tamponade and paradoxical pulse in conscious dogs.

The physiological mechanism of paradoxical pulse in cardiac tamponade remains controversial. In eight conscious dogs with intact pericardia, ultrasonic dimension transducers assessed biventricular geometry and volumes, while micromanometers measured right ventricular (RV), left ventricular (LV), pleural, and pericardial pressures. With normal inspiration, peak LV pressure fell by 7.7 +/- 1.3 mmHg at control and by 20.3 +/- 3.7 mmHg during tamponade (P < 0.001), consistent with the development of paradoxical pulse. At peak inspiration during tamponade, RV filling increased, the interventricular septum shifted leftward, transeptal pressure became negative, and LV septal arc length (l theta) became smaller than its respective unpreloaded value at maximal vena caval occlusion (l(o)). Analysis of stroke work (SW)-end-diastolic volume (EDV) and end-systolic pressure-volume coordinates at peak inspiration during tamponade revealed that end-systolic pressure was 19.1 +/- 10.2 mmHg below the baseline end-systolic pressure-volume curve (P < 0.01), and SW was 24.2 +/- 8.8% below the baseline SW-EDV curve (P < 0.01), indicating transient inspiratory LV dysfunction. It is proposed that inspiratory leftward interventricular septal shifting at low LV EDV during tamponade completely unloads the septum (l theta < l o), eliminates the septal contribution to global LV SW, results in transient inspiratory LV dysfunction, and contributes to the phenomenon of paradoxical pulse.