Mean Velocity Of Fiber Shortening Research Articles

Relative contribution of afterload and interstitial tissue fibrosis to pre-operative longitudinal and circumferential function in patients with severe aortic stenosis

Previous studies have shown that, in patients with severe aortic stenosis (SAS), global longitudinal strain (GLS), as assessed by speckle tracking echocardiography (STE), is often reduced. The present study aimed to understand the mechanisms underlying this reduction by using stress-shortening relationships. Ninety-nine patients with isolated SAS (36% men, 69 ± 11 years) and 75 healthy volunteers (HV) underwent resting 2D-echo and STE to measure GLS, global circumferential strain (GCS), rate-corrected mean velocity of fiber shortening (Vcfc), and end-systolic wall stress (ESWS). Stress-GLS, GCS or Vcfc relationships were constructed using the HV data and fitted to a linear regression. The relative position of individual SAS patients on these relationships was calculated and used as a load-independent index of myocardial contractility (unloaded GLS,GCS or Vcfc). At the time of surgery, myocardial biopsy was obtained to quantify interstitial fibrosis. GLS and Vcfc were lower in SAS than HV (−17 ± 3 vs. −20 ± 2%, P < 0.001; and 1.1 ± 0.3 vs. 1.3 ± 0.3 cm/s, P < 0.001). In contrast, GCS was similar in both groups (−29.04 ± 4.7% and −29.6 ± 4.3%, P = 0.40). In HV, GLS was less afterload-dependent than Vcfc and GCS. In SAS, unloaded GLS, GCS and Vcfc were lower than 2 standard deviations of HV in respectively 40%, 18% and 35% of patients. Using multivariate analysis, unloaded GLS, GCS and Vcf correlated significantly ( P < 0.05) with interstitial fibrosis and LV mass. Moreover, if divided by tertiles of fibrosis (< 2.3%, 2.3–5.4%, > 5.4%), a real gradient is draw between the groups. The more fibrosis they have, the worse the longitudinal and circumferential functions are altered for a given afterload ( Fig. 1 ). In HV, longitudinal function is less afterload-dependent than circumferential function. In SAS, reduced longitudinal or circumferential function is a marker of interstitial fibrosis and LV remodeling.

Myocardial lipid accumulation in patients with pressure-overloaded heart and metabolic syndrome

We evaluated the role of sterol-regulatory element binding protein (SREBP)-1c/peroxisome proliferator activated receptor-gamma (PPARgamma) pathway on heart lipotoxicity in patients with metabolic syndrome (MS) and aortic stenosis (AS). Echocardiographic parameters of heart function and structural alterations of LV specimens were studied in patients with (n = 56) and without (n = 61) MS undergoing aortic valve replacement. Tissues were stained with hematoxylin-eosin (H and E) and oil red O for evidence of intramyocyte lipid accumulation. The specimens were also analyzed with PCR, Western blot, and immunohistochemical analysis for SREBP-1c and PPARgamma. Ejection fraction (EF) was lower in MS compared with patients without MS (P < 0.001); no difference was found in aortic orifice surface among the groups. H and E and oil red O staining of specimens from MS patients revealed several myocytes with intracellular accumulation of lipid, whereas these alterations were not detected in biopsies from patients without MS. Patients without MS have low levels and weak immunostaining of SREBP-1c and PPARgamma in heart specimens. In contrast, strong immunostaining and higher levels of SREBP-1c and PPARgamma were seen in biopsies from the MS patients. Moreover, we evidenced a significative correlation between both SREBP-1c and PPARgamma and EF and intramyocyte lipid accumulation (P < 0.001). SREBP-1c may contribute to heart dysfunction by promoting lipid accumulation within myocytes in MS patients with AS; SREBP-1c may do it by increasing the levels of PPARgamma protein.

A stress echocardiography study of cardiac function during progressive exercise in pediatric oncology patients treated with anthracyclines

Anthracycline-treated patients (AP) are at risk for cardiac dysfunction years after treatment. Cardiac function has not been evaluated during exercise in AP. The purpose of this study was to assess exercise tolerance, left ventricular (LV) function, and hemodynamics during progressive exercise. We studied 47 AP (cumulative dose: 36-504 mg/m(2)) who were in complete remission and 12 healthy controls (CON). AP were further grouped by cumulative dose (LOW <or= 260 mg/m(2); HIGH >or= 260 mg/m(2)) and resting echocardiographic function. All subjects performed 3-min incremental stages on a semi-recumbent cycle ergometer until volitional fatigue. Using echocardiography and Doppler, LV dimensions, posterior wall thickness (LVPWs), peak aortic velocity (PAoV), shortening fraction (SF), rate-corrected mean velocity of fiber shortening (MVCFc), wall stress at peak systole (sigmaPS), stroke volume index (SVI), and cardiac index (CI) were determined. Measurements were performed at rest, during each stage of exercise, and in recovery. AP did less work than CON (P < 0.050). CON and LOW had similar resting function, while HIGH had a lower SF and MVCFc (P < 0.050) and a higher sigmaPS (P < 0.001). Resting SVI and CI were also lower in HIGH. At peak exercise, MVCFc and sigmaPS remained different in HIGH, and both AP groups had a lower SF, SVI, and CI (P < 0.001). AP had an abnormal SVI response to exercise. AP showed a smaller initial increase in SVI that was not maintained throughout exercise. AP have reduced exercise tolerance. There also appears to be a dose-related effect on myocardial contractility and SVI. These findings may help to guide treatment.

Minor segmental dyssynergy reflects extensive myocardial damage and global left ventricle dysfunction in chronic Chagas disease

The majority of patients with Chagas disease (ChD) remain for 10 to 30 years or even for life in the indeterminate form (IF) of this disease. They have positive-specific serology tests for ChD, but no symptoms or physical signs, and normal findings for electrocardiograms (ECGs) and heart, esophagus, and colon radiographs. To investigate whether patients in this phase of disease have any impairment of left ventricular (LV) systolic performance, we assessed their contractility index by the slope of the LV end-systolic pressure-dimension (Pes-Des) relation. We studied 35 patients with ChD (14 IF, 11 digestive form [DF], 10 cardiac form [CF]) and 13 healthy subjects. Patients with the CF had only minor cardiac involvement (bundle-branch block, normal LV ejection fraction). All patients had normal baseline global LV systolic function on 2-dimensional echocardiography, but minor segmental wall motion abnormalities were observed in 3 DF, 3 IF, and 2 CF patients. At rest and during intravenous phenylephrine infusion, we measured LV dimensions by echocardiography, and LV end-systolic pressure was estimated by a calibrated carotid pulse tracing. We also measured percent fractional shortening (%ΔD) and the rate-corrected mean velocity of fiber shortening (Vcfc). Mean values (± SD) of %ΔD and Vcfc were not significantly different from those exhibited by healthy control subjects in any of the ChD groups at rest (except for CF) or at peak stress using phenylephrine. The Pes-Des slope was similarly and significantly reduced in all ChD patients (IF: 50.7 ± 25; DF: 52.3 ± 24; CF: 60.8 ± 22 mm Hg/cm) compared with normal subjects (89 ± 17 mm Hg/cm). The Pes-Des slope was even more depressed (39.6 ± 10 mm Hg/cm) in ChD patients who had minor segmental wall motion abnormalities (SWMAs) on the baseline 2-dimensional echocardiograph in comparison with the slightly reduced values found in patients with CF who had isolated conduction abnormalities on the ECG (71.8 ± 10 mm Hg/cm). Although %ΔD and Vcfc, even at peak afterload, do not differentiate ChD patients from normal controls, the Pes-Des slope is significantly impaired in IF, DF, and CF patients. The remarkably lower Pes-Des slope value documented in ChD patients exhibiting only minor LVWMAs suggests a more extensive myocardial damage in this group of patients, indicating that they should be considered as exhibiting symptoms of the CF version of the disease. (J Am Soc Echocardiogr 2002;15:610-16.)

Cardiorespiratory exercise capacity and its relation to a new doppler index in children previously treated with anthracycline

The purpose of this study was to assess the exercise capacity of patients treated with anthracycline and to evaluate the relation between the exercise capacity and a new Doppler index. The study patients consisted of 70 subjects: 41 healthy subjects and 29 who had been treated with various cumulative doses of anthracycline (range 45 to 873 mg per body surface area). The following conventional echocardiographic parameters were measured: rate-corrected mean velocity of fiber shortening (mVcfc), end-systolic wall stress (ESS), stress-velocity index, and early and late diastolic mitral inflow velocities and their ratio. A new Doppler index, the Tei index, was calculated as the sum of isovolumic contraction time and isovolumic relaxation time divided by the ejection time. Peak oxygen uptake (pVo2) and anaerobic threshold (AT) were measured during an upright bicycle exercise test. The pVo2 and AT in the patient group were significantly lower than those in the control group (pVo2: 22.0 ± 3.7 versus 28.5 ± 7.1 mL/min/kg; AT: 12.7 ± 1.9 versus 17.3 ± 4.3 mL/min/kg, respectively; P <.01). There were no significant differences in the mVcfc, ESS, stress-velocity index, E wave, A wave, or E/A wave ratio between the two groups. However, the mean Tei index of the patients was significantly greater than that of the controls (0.41 ± 0.11 versus 0.33 ± 0.04, P <.01). The pVo2 and AT decreased significantly with an increase in the Tei index (r = −0.64 and −0.60, respectively; P <.01). A weak positive correlation was found between the AT and E/A wave ratio (r = 0.54, P <.05). However, no significant correlations were seen between the exercise parameters and the mVcfc, ESS, stress velocity index, or transmitral velocities. Our findings suggest that cardiopulmonary exercise testing revealed an inverse correlation between exercise capacity and the Tei index. (J Am Soc Echocardiogr 2001;14:256-63.)

Serial echocardiographic and Doppler evaluation of left ventricular systolic performance and diastolic filling in premature infants.

To examine the effects of somatic growth on left ventricular systolic and diastolic functions in premature infants, we performed serial two-dimensional, M-mode and Doppler echocardiograms of 18 premature infants in the early neonatal period (mean of 14 days) and on the day when they were discharged from the hospital (mean of 94 days). The relation between rate-corrected mean velocity of fiber shortening and end-systolic wall stress relation was used as a load-independent estimate of contractility. Diastolic function was assessed by transmitral Doppler filling velocity patterns. The end-systolic wall stress was significantly lower in the first examination than in the second examination (38+/-8 vs. 46+/-10 g/cm2, P < 0.005). However, there was no significant difference in the rate-corrected velocity of fiber shortening between the two examinations. An inverse linear relation between the end-systolic wall stress and the rate-corrected mean velocity of fiber shortening was found in each examination. The slopes of these two regression lines showed no significant difference, suggesting that the left ventricular contractility is on the same level during this study period. The transmitral Doppler flow velocity patterns markedly altered between the two observations. The peak E wave, peak A wave, peak E/A ratio, flow velocity time integral of E/A wave, the first third filling fraction, and the normalized peak filling rate to stroke volume increased significantly during the study period (78+/-14 vs. 31+/-9 cm/s, 61+/-12 vs. 33+/-7 cm/s, 1.29+/-0.18 vs. 0.93+/-0.19, 1.75+/-0.58 vs. 1.17+/-0.24, 0.42+/-0.07 vs. 0.37+/-0.05, and 9.48+/-1.71 vs. 7.30+/-0.96/s, respectively, P < 0.001), suggesting a relative shift of Doppler filling into the early diastole. We demonstrated that the age- and growth-related alterations in the transmitral Doppler filling patterns occurred dramatically without changes in contractility during the first 3 months after birth. This diastolic filling change may be related to the age-related maturation in the left ventricular diastolic properties.

Physiologic response to dobutamine infusion during cardiac stress testing of dogs

Abstract Objective To evaluate response of various cardiovascular variables after administration of incremental doses of dobutamine in healthy conscious dogs, using standardized dobutamine stress echocardiography (DSE). Animals 8 healthy dogs. Procedure A DSE was performed twice on each dog within 24 hours. Dobutamine was infused at a rate of 12.5 to 42.5 μg/kg/min, using incremental increases of 10 μg/kg/min. Doppler sphygmomanometry, electrocardiography, and echocardiography were performed. Left ventricular size, global ventricular performance, and left ventricular systolic myocardial function were measured by means of echocardiography. Results At the highest dosage, dobutamine induced an increase of 20 ± 3% and 109 ± 12% in systolic blood pressure and cardiac index, respectively. The latter was associated with a significant increase in heart rate and stroke index. Fractional shortening of the left ventricle, fractional thickening of the left ventricular free wall and interventricular septum, ejection fraction, and mean velocity of fiber shortening had a progressive and significant increase during dobutamine infusion. Preejection period and left ventricular ejection time had a progressive and significative decrease during the stress test. Conclusions The technique used was feasable, safe, and repeatable in healthy conscious dogs. Control values were determined. Clinical Relevance Data for these healthy dogs might be useful for comparison with results obtained from dogs with known or suspected cardiovascular disease. (Am J Vet Res 1998;59:1160-1165)

Maturational changes in left ventricular contractile state

It has been suggested from animal and human studies that age-related alterations in left ventricular contractility occur. However, there is little information about growth-related changes in left ventricular performance from preterm infants to older children.In 22 preterm infants, 23 fullterm infants, and 35 children, left ventricular contractility was evaluated by two-dimensional and M-mode echocardiography. The rate-corrected mean velocity of fiber shortening (mVcfc)-end-systolic wall stress (ESS) relation was used as an index of contractility. There were significant inverse linear correlations between ESS and mVcfc in the three groups (all P<0.01). The slopes and y-intercepts of the regression lines of mVcfc-ESS relation were both significantly greater in the premature infants (mVcfc=−0.0133 ESS+1.62) and neonates (mVcfc=−0.0107 ESS +1.55) than those in the children (mVcfc=−0.0047+1.29). However, there were no significant differences between the premature and fullterm infants. Thus, these findings suggest that the contractility and afterload sensitivity of the left ventricle in the premature infants may be similar to those in the fullterm infants. In addition, our serial study in the premature infants showed that the ESS increased significantly with growth while the mVcfc did not change, suggesting that the left ventricular performance in the premature infants during early life was preserved in the setting of a lower afterload.

Peak systolic stress-rate-corrected mean velocity of fiber shortening in preterm and fullterm infants.

The relation of rate-corrected mean velocity of fiber shortening (mVcfc)-end-systolic wall stress (ESS) is a load-independent index of left ventricular contractility, but involves simultaneous M-mode echocardiography, carotid or axillary pulse tracing and blood pressure determination, which may be impractical in younger infants. We examined whether the relation of the peak systolic wall stress (PSS)-mVcfc could be used as a simpler method of assessing left ventricular contractility in preterm and fullterm infants. In 45 preterm and fullterm infants, mVcfc, ESS, and PSS were determined using echocardiography, axillary pulse tracing and blood pressure measurement. Five patients with left ventricular dysfunction or low cardiac output state were also studied. The relation of PSS and ESS was PSS=5.19+1.04 ESS (r=0.98, p<0.01). The slope of mVcfc=1.58-0.012 ESS (r=-0.78, p<0.01) was nearly identical to that of mVcfc=1.60-0.011 PSS (r=-0.75, p<0.01), with no difference in the regression coefficients. The relationship of PSS and ESS in 5 patients was very close and the slope of the regression line was nearly identical to that of 45 infants. The relation of mVcfc PSS correlates well with the relation using ESS and can be used as a simple method of assessing left ventricular contractility.

Effects of low-dose dobutamine on left ventricular diastolic filling in children.

To investigate the effects of dobutamine on the Doppler transmitral flow pattern in children with normal left ventricular function, Doppler echocardiography was used to measure the transmitral flow in 14 healthy children before and during infusion of dobutamine (5 micrograms/kg per minute). Cardiac output was measured by the thermodilution method, and stroke volume was calculated as the cardiac output divided by the heart rate. Dobutamine increased the peak velocity and flow velocity-time integral of early diastolic filling without changing those of atrial contraction and normalized peak velocity of early diastolic filling, suggesting an increase in left ventricular relaxation. Dobutamine increased the stroke volume and rate-corrected mean velocity of fiber shortening with reduced end-systolic wall stress, indicating an increase in left ventricular contractility. The percentage of increase in the flow velocity-time integral of early diastolic filling during dobutamine infusion tended to correlate with the increase in stroke volume (r = 0.67, p < 0.05) and with the decrease in end-systolic wall stress (r = -0.61, p < 0.05). Our results suggest that low-dose dobutamine increases left ventricular relaxation with enhanced systolic function. The observed decreased endsystolic wall stress might have caused enhanced relaxation characteristics with dobutamine.

Short- and long-term variability of echocardiographic stress-velocity indexes of cardiac function in a pediatric population

This study determined the short- and long-term variability of stress-velocity relationships at end systole and peak systole. A prospective study during the short term (0 to 15 and 0 to 30 minutes) and long term (0 to 1 and 0 to 12 months) was performed calculating variability by the limits of agreement method. The study was performed in a tertiary-care pediatric echocardiographic laboratory. Twenty-five normal children underwent repeat testing as described. Standard blood pressure, carotid pulse tracing, and M-echocardiography of the left ventricle was performed at the intervals described. The rate-corrected mean velocity of fiber shortening (MVCF C), echocardiographic stress at end systole (SES), and echocardiographic stress at peak systole (SPS) were calculated for all recordings. The slopes of MVCF C-SES and MVCF C-SPS were determined by regression and plotted. With these slopes, the second and third stress values were normalized to the first stress value for the short and long term. The differences in normalized MVCF C and MVCF C (ΔMVCF C) for 15 to 0 minutes, 30 to 0 months, 1 to 0 month, and 12 to 1 month were obtained for both SES and SPS, and 95% limits of agreement were estimated. The mean ΔMVCF C for SES and SPS for the short and long term were not different from 0 or each other, indicating no bias. The 95% limits of agreement of ΔMVCF Cs (i.e., variability for SES at 15 to 0 minutes, 30 to 0 minutes, 1 to 0 months, and 12 to 0 month) were ±0.18, ±0.24, ±0.34, and ±0.27, respectively, and for SPS ±0.18, ±0.24, ±0.33, and ±0.28. Variability showed an increasing trend with time but was significant only from 15 to 0 minutes and 1 to 0 month ( p = 0.006). This study has established short- and long-term variability in the stress-velocity relationship that is essential for monitoring acute and chronic changes in ventricular contractility in an individual patient.

Left Ventricular Ejection Time and End-Systolic Pressure Revisited

Left Ventricular Ejection Time and End-Systolic Pressure Revisited

Preserved left ventricular systolic and diastolic function in normoalbuminuric insulin-dependent diabetic patients with glomerular hyperfiltration

This study was conducted to test the hypothesis that normotensive, normoalbuminuric IDDM patients with glomerular hyperfiltration may present functional or structural cardiac abnormalities. Eleven normoalbuminuric and normotensive IDDM patients with normal glomerular filtration rate and 11 patients with hyperfiltration were compared with a group of 17 age and sex matched controls. Glomerular filtration rate was measured by the 51Cr-EDTA technique and hyperfiltration was defined as a glomerular filtration rate higher than 134 ml/min/1.73 m 2. Phonocardiogram, M-mode and pulsed Doppler two-dimensional echocardiograms were performed to evaluate resting left ventricular dimensions, systolic and diastolic function. Left ventricular dimensions, fractional shortening, mean velocity of fiber shortening, early and late diastolic peak filling velocity, deceleration time, mitral flow velocity integral, and isovolumic relaxation time were similar (ANOVA P > 0.05) in normal controls, diabetic patients with normal glomerular filtration rate, and diabetic patients with hyperfiltration. In conclusion, the results of our controlled observations indicate that normoalbuminuric and normotensive IDDM patients who have normal glomerular filtration rate or hyperfiltration have no Doppler-echocardiographic evidence of functional and structural abnormalities.

Systolic and diastolic function in tricuspid valve atresia before the fontan operation

Systolic and diastolic function were assessed at preoperative cardiac catheterization in 6 patients with classic tricuspid atresia and were compared with those in control subjects. All patients had systemic-to-pulmonary shunts. Left ventricular end-systolic and end-diastolic volumes and masses were significantly larger in the patient group; stroke volume and the ratio of volume to mass were also higher, but not significantly. Mean end diastolic, peak systolic and end-systolic pressures were similar. Mean stress at end-systole and peak systole were significantly higher in the patient group. Operant chamber stiffness tended to be lower than normal, but was not statistically significant, and myocardial stiffness was normal for the patient group also. Indexes of systolic function were compared. The rate-corrected mean velocity of fiber shortening in the patient group was tower and its relation with stress at end-systole was variable with 4 abnormal patients. The ratio of stress at end-systole/end-systolic volume was significantly lower in patients. The duration of hospital stay did not correlate with end-diastolic volume or any parameter. Thus, this study found abnormalities of load-dependent and independent indexes of systolic function with normal diastolic function in young preoperative patients with tricuspid atresia.

Rate-corrected mean velocity of fiber shortening-stress at peak systole as a load-independent measure of contractility

The relation of mean velocity of fiber shortening-stress at end-systole is a good load-independent index of left ventricular contractility, but involves simultaneous M-mode echocardiography, carotid tracing and blood pressure determination, which may be impractical in children. As stress at peak systole and end-systole are closely related, this study examined whether the relation of mean velocity of fiber shortening-stress at peak systole could be used as a simpler method of assessing left ventricular contractility in a normal population of children. In addition, the cross-sectional normal range for a pediatric population was obtained. In 25 normal children aged 4 to 17 years (mean age 11), rate-corrected mean velocity of fiber shortening (MVCF c), stress at peak systole (σPS), and end-systolic stress (σES) were determined using echocardiography, carotid pulse tracing and blood pressure measurement. Six patients with cardiomyopathy (mean age 8 years) were also studied. The relation of stress at peak systole and end-systolic stress was σPS = 1.004 σES + 12.0 (r = 0.91, SEE = 4.98; p < 0.001) for the normal group, and σPS = 1.083 σES + 7.7 (r = 0.99, SEE = 4.07; p < .001) for the cardiomyopathic group. This slope of the regression line was slightly higher and the difference was statistically significant. The slope of MVCF c = 0.0066 σPS + 1.55 (SEE = 0.131, r = −0.52) was nearly identical to that of MVCF c = 0.0065 σES + 1.46, (SEE = 0.135, r = −0.46), with no difference in the regression coefficients. Individual measurements for the cardiomyopathic group fell on similar parts of the graph whether stress at peak systole or end-systole was used for the ordinate of the plot with MVCF c. Thus, in the absence of outflow obstruction, the relation of MVCF c-stress at peak systole correlates well with the relation using stress at end-systole and can be used to assess left ventricular contractility.

Prolonged exercise induces left ventricular dysfunction in healthy subjects

To determine the effects of a moderately prolonged exercise on left ventricular systolic performance, 23 healthy male subjects, aged 18 to 51 yr (mean 37 yr) were studied. The subjects exercised first on a treadmill (brief exercise) and completed, on a separate day, a 20-km run. M-mode, two-dimensional, and Doppler echocardiography, as well as calibrated carotid pulse tracings, were obtained at rest and immediately on completion of both brief and prolonged exercise. Left ventricular systolic function was assessed by end-systolic stress-shortening relationships. Heart rate increased similarly after brief and prolonged exercise (+30%). Mean arterial pressure decreased from 99 +/- 7 to 92 +/- 8 mmHg (P less than 0.001) after prolonged exercise, but it remained unchanged after brief exercise. Left ventricular end-diastolic volume was decreased after prolonged exercise (130 +/- 23 vs. 147 +/- 18 ml at rest, P less than 0.01). Both ejection fraction and rate-adjusted mean velocity of fiber shortening decreased after prolonged exercise [from 67 +/- 5 to 60 +/- 6% (P less than 0.001) and from 1.12 +/- 0.2 to 0.91 +/- 0.2 cm/s (P less than 0.001), respectively] despite a lower circumferential end-systolic wall stress (133 +/- 23 vs. 152 +/- 20 g/cm2). The relationship between ejection fraction (or mean velocity of fiber shortening adjusted for heart rate) and end-systolic wall stress was displaced downward on race finish (P less than 0.05). These changes were independent of the changes in left ventricular end-diastolic volume and hence those in preload. The data suggest that moderately prolonged exercise may result in depressed left ventricular performance in healthy normal subjects.

Separation between vasodilation and positive inotropism by assessment of myocardial energetics in patients with dilated cardiomyopathy

Phosphodiesterase inhibitors have vasodilating and positive inotropic properties, and these compounds may have energy saving effects due to vasodilation and energy consuming effects due to inotropism. In order to differentiate between the effects, it is necessary to relate myocardial oxygen consumption to its hemodynamic determinants. Myocardial oxygen consumption per beat was related to the following parameters: dp/dtmax, mean velocity of fiber shortening, pressure-volume work, peak developed wall stress, and stress-time integral. The best linear relationship was found between myocardial oxygen consumption per beat and the corresponding stress-time integral (r = 0.71; p less than 0.001) in patients with idiopathic dilative cardiomyopathy. Using i.v. nitroprusside as a pure vasodilator, myocardial oxygen consumption per beat and stress-time integral decreased along this established relationship. In contrast, the phosphodiesterase inhibitor enoximone given intravenously decreased the stress-time integral significantly more than the myocardial oxygen consumption per beat. We conclude from these data that phosphodiesterase inhibitors possess vasodilating properties which reduce the myocardial oxygen demand. In addition, they do have positive inotropic effects which increase the myocardial oxygen demand. Myocardial oxygen consumption always reflects the sum of both effects. The balance between the energy saving and the energy consuming effects may determine the efficacy of phosphodiesterase inhibitors, especially in the long-term treatment of chronic heart failure.

Comparison of Preoperative Left Ventricular Function With Postoperative Left Ventricular Response to Exercise in Patients With Chronic Aortic Regurgitation and Aortic Stenosis

The relation between preoperative left ventricular (LV) systolic function at rest and postoperative LV response to exercise was assessed in 13 patients with aortic regurgitation (AR) and nine patients with aortic stenosis (AS). Preoperative end-systolic volume index (ESVI) and ejection fraction (EF) determined by LV angiography were compared with postoperative exercise-induced changes of LV fractional shortening (delta %FS) and mean velocity of fiber shortening (delta mVcf) assessed by echocardiography. Preoperative EF and ESVI in 13 patients with AR correlated well with postoperative delta %FS and delta mVcf. Similarly, preoperative EF and ESVI in nine patients with AS correlated well with postoperative delta %FS and delta mVcf. Our study demonstrated that preoperative LV systolic function in AR and AS patients closely reflected postoperative LV response to exercise. Preoperative smaller ESVI will be warranted to expect a favorably good postoperative LV response to exercise.

Physiologic mechanisms governing hemodynamic responses to positive inotropic therapy in patients with dilated cardiomyopathy.

Clinical trials in patients with dilated cardiomyopathy (DCM) have shown a wide disparity in the hemodynamic responses to positive inotropic therapy. In addition, the response of the failing left ventricle to positive inotropic agents reflects the net interaction of multiple factors, including the magnitude of contractile abnormality and compensatory mechanisms. In the current study, left ventricular geometry, loading conditions, and contractile state were assessed in 13 patients with nonischemic DCM with the use of simultaneous high-fidelity pressure measurements and echocardiographic recordings. Comparisons were made with echocardiographic and calibrated carotid pulse data acquired in nine age-matched normal subjects. The patients with DCM were divided according to the left ventricular end-diastolic wall thickness-to-dimension ratio into groups with "appropriate" hypertrophy (i.e., less than or equal to 2 SDs from mean normal; n = 5; group 1) and "inadequate" hypertrophy (i.e., greater than 2 SDs from mean normal; n = 8; group 2). Age, New York Heart Association functional class, left ventricular wall mass index, and left ventricular end-diastolic pressure and dimension were similar for the DCM groups. Baseline left ventricular afterload (defined as circumferential end-systolic wall stress, sigma es) was 168% and 203% greater than normal in groups 1 and 2, respectively. The administration of the beta-adrenoceptor agonist dobutamine decreased left ventricular afterload by 12% in the normal subjects and by 10% in group 1 patients, while augmenting afterload by 5% in group 2 patients. The latter response occurred despite a 17% fall in systemic vascular resistance. Overall left ventricular performance, as assessed by the rate-corrected mean velocity of fiber shortening (Vcfc), was related to left ventricular afterload (i.e., sigma es). The resultant sigma es -Vcfc relationship, a sensitive measure of left ventricular contractility, was determined over a wide range of afterload conditions generated by methoxamine (normal subjects) or nitroprusside (DCM). Baseline left ventricular contractile state was 61% of normal for group 1 and 44% of normal for group 2. The contractile response to dobutamine infusion was 52% of normal for group 1 and only 22% of normal for group 2. Thus, positive inotropic therapy with dobutamine in patients with DCM is limited by (1) an attenuated contractile response and (2) elevated left ventricular afterload, which may be augmented further during its administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term Effects of Parathyroidectomy on Cardiac and Autonomic Nervous System Functions in Haemodialysis Patients

Ten patients receiving regular haemodialysis therapy who underwent parathyroidectomy for secondary hyperparathyroidism were investigated to evaluate the effects of parathyroid hormone on left ventricular and autonomic nervous system functions. The study which included M-mode echocardiography and autonomic nervous system tests (hormonal and cardiovascular response to the postural test, cold pressor test, handgrip test, diving reflex test and Valsalva manoeuvre) were performed prior to parathyroidectomy, and 5-8 months after, on a nondialysis day. The cardiovascular response and plasma noradrenaline changes to postural test remained unchanged following parathyroidectomy. The resting heart rate decreased from 73.1 +/- 2.4 to 66.4 +/- 2.3 beats/min (P less than 0.05) but mean blood pressure did not change post-parathyroidectomy. Mean blood pressure and heart rate changes during the cold pressor test, handgrip test, diving test and Valsalva manoeuvre were unaffected by parathyroidectomy. End-diastolic and end-systolic dimensions, fractional fibre shortening, mean velocity of fibre shortening and the ratio of the pre-ejection period to the left ventricular ejection time were normal prior to parathyroidectomy and remained unchanged following it. This study suggests that the reduction in parathyroid hormone concentrations obtained by parathyroidectomy does not significantly modify heart function and autonomic nervous system activity in the long term.