Altered left ventricular mechanics in patients with valvular aortic stenosis and coarction of the aorta: effects on systolic performance and late outcome

Left Ventricular Mass Change After Anthracycline Chemotherapy

BACKGROUND

Myocardial atrophy and left ventricular (LV) mass reductions are associated with fatigue and exercise intolerance. The relationships between the receipt of anthracycline-based chemotherapy (Anth-bC) and changes in LV mass and heart failure (HF) symptomatology are unknown, as is their relationship to LV ejection fraction (LVEF), a widely used measurement performed in surveillance strategies designed to avert symptomatic HF associated with cancer treatment.

METHODS AND RESULTS

We performed blinded, serial assessments of body weight, LVEF and mass, LV-arterial coupling, aortic stiffness, and Minnesota Living with Heart Failure Questionnaire measures before and 6 months after initiating Anth-bC (n=61) and non-Anth-bC (n=15), and in 24 cancer-free controls using paired t and χ² tests and multivariable linear models. Participants averaged 51±12 years, and 70% were women. Cancer diagnoses included breast cancer (53%), hematologic malignancy (42%), and soft tissue sarcoma (5%). We observed a 5% decline in both LVEF (P<0.0001) and LV mass (P=0.03) in the setting of increased aortic stiffness and disrupted ventricular-arterial coupling in those receiving Anth-bC but not other groups (P=0.11-0.92). A worsening of the Minnesota Living with Heart Failure Questionnaire score in Anth-bC recipients was associated with myocardial mass declines (r=-0.27; P<0.01) but not with LVEF declines (r=0.11; P=0.45). Moreover, this finding was independent of LVEF changes and body weight.

CONCLUSIONS

Early after Anth-bC, LV mass reductions associate with worsening HF symptomatology independent of LVEF. These data suggest an alternative mechanism whereby anthracyclines may contribute to HF symptomatology and raise the possibility that surveillance strategies during Anth-bC should also assess LV mass.

Regional right ventricular remodeling and function in children with idiopathic pulmonary arterial hypertension vs those with pulmonary valve stenosis: Insights into mechanics of right ventricular dysfunction

BACKGROUND

Right ventricular (RV) pressure overload in the context of pulmonary stenosis (PS) has a much better prognosis than in the context of idiopathic pulmonary arterial hypertension (iPAH), which may be related to differences in global and regional RV remodeling and systolic function. We compared RV mechanics in children with PS to those with iPAH, aiming to identify mechanisms and markers of RV dysfunction.

METHODS

Eighteen controls, 18 iPAH and 16 PS patients were retrospectively studied. Age, BSA, and sex distribution were comparable. Two-dimensional echocardiography, blood flow and tissue Doppler, and longitudinal RV deformation were analyzed. ANCOVA-including RV systolic pressure (RVSP) and length as covariates-was used to compare patient groups.

RESULTS

RV systolic pressure was higher in iPAH vs PS (96.8±25.4 vs 75.4±18.9 mm Hg, P=.011). Compared to controls, PS patients showed mild dilation (P<.01) and decreased longitudinal deformation (P<.001) at the RV apex. Compared to both PS and controls, iPAH patients showed marked spherical RV dilation (P<.001), reduced global, RV free wall and septal longitudinal deformation (iPAH -22.07%±4.35% vs controls -28.18%±1.69%; -9.98%±4.30% vs -17.45%±2.52%; P<.001) and RV postsystolic shortening (P<.001). RV transverse shortening (radial performance) was increased in PS (31.75%±10.35%; P<.001) but reduced in iPAH (-1.62%±11.11% vs controls 12.00%±7.74%; P<.001).

CONCLUSION

Children with iPAH demonstrate adverse global and regional RV remodeling and mechanics compared to those with PS. Mechanisms of RV systolic dysfunction in iPAH include decreased longitudinal deformation, decreased or absent transverse shortening, and postsystolic shortening. These markers may be useful to identify children at risk of RV failure.

Adverse ventricular-ventricular interactions in right ventricular pressure load: Insights from pediatric pulmonary hypertension versus pulmonary stenosis

Right ventricular (RV) pressure overload has a vastly different clinical course in children with idiopathic pulmonary arterial hypertension (iPAH) than in children with pulmonary stenosis (PS). While RV function is well recognized as a key prognostic factor in iPAH, adverse ventricular–ventricular interactions and LV dysfunction are less well characterized and the pathophysiology is incompletely understood. We compared ventricular–ventricular interactions as hypothesized drivers of biventricular dysfunction in pediatric iPAH versus PS. Eighteen iPAH, 16 PS patients and 18 age‐ and size‐matched controls were retrospectively studied. Cardiac cycle events were measured by M‐mode and Doppler echocardiography. Measurements were compared between groups using ANOVA with post hoc Dunnet's or ANCOVA including RV systolic pressure (RVSP; iPAH 96.8 ± 25.4 mmHg vs. PS 75.4 ± 18.9 mmHg; P = 0.011) as a covariate. RV‐free wall thickening was prolonged in iPAH versus PS, extending beyond pulmonary valve closure (638 ± 76 msec vs. 562 ± 76 msec vs. 473 ± 59 msec controls). LV and RV isovolumetric relaxation were prolonged in iPAH (P < 0.001; LV 102.8 ± 24.1 msec vs. 63.1 ± 13.7 msec; RV 95 [61–165] vs. 28 [0–43]), associated with adverse septal kinetics; characterized by rightward displacement in early systole and leftward displacement in late RV systole (i.e., early LV diastole). Early LV diastolic filling was decreased in iPAH (73 ± 15.9 vs. PS 87.4 ± 14.4 vs. controls 95.8 ± 12.5 cm/sec; P = 0.004). Prolonged RVFW thickening, prolonged RVFW isovolumetric times, and profound septal dyskinesia are associated with interventricular mechanical discoordination and decreased early LV filling in pediatric iPAH much more than PS. These adverse mechanics affect systolic and diastolic biventricular efficiency in iPAH and may form the basis for worse clinical outcomes. We used clinically derived data to study the pathophysiology of ventricular–ventricular interactions in right ventricular pressure overload, demonstrating distinct differences between pediatric pulmonary arterial hypertension (iPAH) and pulmonary stenosis (PS). Altered timing of right ventricular free wall contraction and profound septal dyskinesia are associated with interventricular mechanical discoordination and decreased early LV filling in iPAH much more than PS. These adverse mechanics affect systolic and diastolic biventricular efficiency, independent of right ventricular systolic pressure.

Function of the Left and Right Ventricles and the Interactions Between Them

OBJECTIVES

There has been a recent increase in our understanding of mechanisms whereby the two sides of the heart interact and modulate each other that may be particularly relevant to patients in the ICU. For this review, our objectives are to examine the function of the left ventricle, consider some of the ways in which the function of the right ventricle differs from that of the left, and examine the effects of the left ventricle on the function of the right and vice versa.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSIONS

There are fundamental differences between the function of the left and right ventricles, which relate to a significant extent to differences in their respective arterial loads. Although traditionally it has been usual to consider the function of the left and right ventricle in isolation, it is now recognized that this approach is flawed and as a result there is an increasing appreciation of the continual cross talk between the two sides of the heart in both the normal and diseased states. A more rational approach to the use of standard therapies frequently used in the cardiac ICU will come from a better understanding of these important fundamental concepts, and novel therapeutic concepts are already emerging from new data regarding biventricular interactions.

Ventricular mechanics in patients with aortic valve disease: longitudinal, radial, and circumferential components

BACKGROUND

Reduced long-axis shortening despite enhanced global function has been reported in aortic stenosis. We sought to improve the understanding of this phenomenon using multi-dimensional strain analysis in conjunction with the evaluation of left ventricular rotation and twist - ventricular torsion - using tissue Doppler techniques.

METHODS

A total of 57 patients with variable severity of aortic stenosis, aortic regurgitation, or mixed aortic valve disease, subdivided into six groups, were studied. Ventricular morphology was assessed using long-axis/short-axis and mass/volume ratios, afterload using end-systolic meridional wall stress, and global performance using ejection fraction. The circumferential and longitudinal strain was measured from two-dimensional images, and left ventricular rotation and twist were estimated as the difference in rotation between the base and apex of the ventricle.

RESULTS

Aortic stenosis was associated with higher mass/volume, ejection fraction, circumferential strain and left ventricular rotation and twist, significantly lower end-systolic wall stress, and a trend towards lower longitudinal strain compared with normal. Myocardial mechanics in aortic regurgitation were normal despite ventricular dilation. Mixed aortic valve disease showed findings similar to aortic stenosis. Left ventricular rotation and twist correlated with midwall circumferential strain (r = 0.62 and p < 0.0001), endocardial circumferential strain (r = 0.61 and p < 0.0001), and end-systolic wall stress (r = 0.48 and p < 0.0001), but not with longitudinal strain (r = 0.18 and p > 0.05).

CONCLUSIONS

Myocardial mechanics are normal in patients with aortic regurgitation, independent of abnormalities in cardiac geometry. Conversely, in aortic stenosis and mixed aortic valve disease, significant alterations in the patterns of fibre shortening are found. The effects of stenosis on cardiac function seem to dominate the effect of ventricular remodelling.

Trends in pediatric imaging: ultrasound

For the last three decades, two-dimensional (2D) echocardiography and Doppler echocardiography have been the primary imaging modalities for the diagnosis and management of heart disease in infants, children, and adolescents. These methods are non-invasive, highly sensitive, and cost-effective, and widely available, making them very useful in clinical work. During this period, the anatomic and hemodynamic abnormalities associated with different congenital and acquired pediatric heart diseases have been well outlined by echocardiography. Recent advances in computer technology, signal processing, and transducer design have allowed the capabilities of pediatric echocardiography to be expanded beyond qualitative 2D imaging and blood flow Doppler analysis. New modalities such as three-dimensional echocardiography, tissue Doppler imaging and speckle tracking echocardiography have been used to evaluate parameters such as ventricular volume, myocardial velocity, regional strain, and strain rate, providing new insight into cardiovascular morphology and ventricular systolic and diastolic function. Accordingly, a comprehensive and sophisticated quantification of ventricular function is now part of most echocardiography protocols. Use of measurements adjusted for body size and age is common practice today. These developments have further strengthened the position of echocardiography in pediatric cardiology.

Cardiac function in congenital adrenal hyperplasia: a pattern of reversible cardiomyopathy

OBJECTIVE

To evaluate cardiac function in infants with congenital adrenal hyperplasia (CAH) before and after corticosteroid replacement therapy.

STUDY DESIGN

This prospective, case-control study included 9 infants with CAH. Cardiac function was assessed by echocardiography at presentation and after corticosteroid replacement therapy. Six term infants underwent 2 echocardiograms each and served as the control group. Data on fractional shortening (FS), rate-corrected velocity of circumferential fiber shortening (Vcf), wall stress, tissue Doppler indices, myocardial performance index, left ventricular mass, and Vcf/wall stress were obtained.

RESULTS

The infants with CAH exhibited myocardial dysfunction at baseline and lower systolic blood pressure (SBP) compared with the control group. FS, a measure of systolic contractility, differed significantly from before to after corticosteroid treatment (mean, 32.3%±4.7% pretreatment, 39.9%±5.0% posttreatment). Vcf, a preload-independent measure of cardiac contractility, also differed significantly before and after treatment (mean, 1.23±0.16 circumferences/second pretreatment, 1.45±0.22 circumferences/second posttreatment). SBP was also lower (mean, 84±9.3 mmHg) and improved with treatment (mean, 95±4.8 mmHg). The control group demonstrated no statistically significant changes in FS, Vcf, or SBP. There was a change in left ventricular mass in the control group between the 2 studies.

CONCLUSION

Newborns with CAH have evidence for cardiac dysfunction at baseline that reverses with corticosteroid replacement therapy. These data suggest that corticosteroids play a direct role in modulating cardiac function in the newborn.

Assessment of severity in aortic stenosis-incremental value of endocardial function parameters compared with standard indexes

Several studies have reported that patients (pts) with severe aortic stenosis and similar pressure gradients or even similar aortic valve areas may have quite different symptomatic status and clinical outcomes suggesting that other factors might have a significant impact on the pathophysiology of this disease. Our purpose was to assess the severity of subendocardial wall dysfunction in symptomatic and asymptomatic pts with aortic stenosis using tissue Doppler imaging (TDI), strain rate imaging (SRI) and cyclic variation of integrated backscatter (IB). We studied 68 pts with aortic valvar stenosis and 46 subjects with no signs of heart disease. SRI/IB indexes were calculated in the apical four chambers views at endocardial level. Early diastolic endocardial strain rate showed the best correlation with transvalvar pressure gradients and valve areas. Compared with controls, symptomatic pts showed a more marked decrease in endocardial strain, strain rate and cyclic variation of IB. Receiver operating characteristic (ROC) curves suggested that the thresholds offering an adequate compromise between sensitivity and specificity for the prediction of symptoms were >/=60 mm Hg for the pressure gradient, less than 0.60 cm(2)/m(2) for aortic valve area, less than 20% for strain, less than 2.0 s(-1) for strain rate and less than 3.0 dB for cyclic variation. The combination of pressure gradient, aortic valve area and SRI/IB parameters resulted in an improvement of the overall performance for predicting the symptomatic state. Thus, SRI/IB parameters have an incremental value in differentiating symptomatic and asymptomatic pts with aortic stenosis compared with conventional hemodynamic parameters.

Echocardiography in congenital heart disease: usefulness, limits and new techniques

Echocardiography represents the non-invasive tool most commonly used in pediatric cardiology. Indeed, it enables the definition of both the morphological and functional findings in congenital heart disease (CHD), as completely as possible in almost all the cases. In comparison with adult subjects, the echocardiographic evaluation in pediatric patients requires a different approach, providing information on the heart position in the thorax, the atrial situs viscerum, the vein-atrial and the atrio-ventricular connections, the relationship between the ventricles, the ventriculo-arterial connection and the relationship of the great arteries (segmental analysis). In addition, the echocardiographic study should include a non-invasive study of ventricular function, as mandatory to warrant an optimal pre- and postoperative management in patients with CHD. The indices most commonly utilized to assess ventricular mechanics are the 'pump indices' (i.e. ejection fraction or fractional shortening). Unfortunately, they may lead to invalid data, because of their dependence on loading conditions and heart rate. As a consequence, echocardiographic indices should be used (i.e. fiber shortening or rate-corrected velocity of circumferential fiber shortening-end systolic stress relationship), which better reflect the intrinsic myocardial contractility. More recently, evidence is mounting that new echocardiographic techniques (i.e. Doppler myocardial imaging, strain/strain rate and backscatter) may offer new insights in terms of regional functional and textural findings of the myocardium. However, long-term follow-up studies will be necessary to better define their real impact in the clinical setting.

Anthracycline-induced cardiotoxicity in children with cancer: strategies for prevention and management

The fact that anthracyclines are cardiotoxic seriously narrows their therapeutic index in cancer therapy. The cardiotoxic risk increases with the cumulative dose and may lead to congestive heart failure (CHF) and dilated cardiomyopathy in adults and in children. The prevention of anthracycline-induced cardiotoxicity is particularly important in children who can be expected to survive for decades after being cured of their malignancy. Attempts to reduce anthracycline cardiotoxicity have been directed towards: (i) decreasing myocardial concentrations of anthracyclines and their metabolites by dose limitation and schedule modification; (ii) developing less cardio-toxic analogs; and (iii) concurrently administering cardioprotective agents to attenuate the effects of anthracyclines on the heart. As regards schedule modification, avoidance of anthracycline peak levels may reduce the pathologic and clinical cardiotoxicity, although this has not always been observed. The analogs of doxorubicin, such as idarubicin and epirubicin, have similar cardiotoxicity to that of doxorubicin when given in amounts of equivalent myelotoxicity. Liposomal anthracyclines are a new class of agents that may permit more specific organ targeting, thereby producing less systemic and cardiac toxicity, but more studies are required to assess the advantages, if any, of these preparations over classical anthracyclines. The cardioprotective agent, dexrazoxane, an iron chelator, is highly effective and provides short-term cardioprotection to most patients receiving even the most intensive doxorubicin-containing regimens. Its long-term benefits remain to be determined. In addition, data remain insufficient to make specific recommendations regarding current use of dexrazoxane in children. It is thought that subtle abnormalities, related to anthracycline treatment in childhood, can develop into more permanent myocardial disease resulting in cardiomyopathy, which may progress to CHF. As regards the therapy of patients with anthracycline cardiotoxicity, two different situations have, therefore, to be considered: (i) if the patient presents with cardiac abnormalities, such as a reduction in fractional shortening at echocardiogram, without cardiac symptoms; and (ii) if the patient has CHF. In the presence of CHF, recovery with digitalis-diuretic therapy alone seldom occurs, and in patients who have refractory hemodynamic decompensation, heart transplantation is indicated. In patients with CHF, therapy with ACE inhibitors induces improvement in left ventricular structure and function, but this improvement is transient. Randomized clinical trials are, therefore, necessary to determine the effects of ACE inhibitors in mild-to-moderate left ventricular dysfunction. The beneficial effects of beta-adrenoceptor antagonists (beta-blockers) on cardiac function in heart failure due to anthracyclines seem comparable with those observed in other forms of heart failure with systolic dysfunction. Many drugs are available to treat children with CHF due to anthracycline treatment, but they are only palliative.

Chronic progressive cardiac dysfunction years after doxorubicin therapy for childhood acute lymphoblastic leukemia

PURPOSE

Cross-sectional studies show that cardiac abnormalities are common in long-term survivors of doxorubicin-treated childhood malignancies. Longitudinal data, however, are rare.

METHODS

Serial echocardiograms (N = 499) were obtained from 115 doxorubicin-treated long-term survivors of childhood acute lymphoblastic leukemia (median age at diagnosis, 4.8 years; median follow-up after completion of doxorubicin, 11.8 years). Results were expressed as z scores to indicate the number of standard deviations (SDs) above (+) or below (-) the normal predicted value. Median individual and cumulative doxorubicin doses were 30 mg/m2 per dose and 352 mg/m2, respectively.

RESULTS

Left ventricular fractional shortening was significantly reduced after doxorubicin therapy, and the reduction was related to cumulative dose. z scores for fractional shortening transiently improved before falling to -2.76 more than 12 years after diagnosis. Reduced fractional shortening was related to impaired contractility and increasing afterload, consequences of a progressive reduction of ventricular mass, and wall thickness relative to body-surface area. Left ventricular contractility fell significantly over time and was depressed at last follow-up in patients receiving more than 300 mg/m2 of doxorubicin. Systolic and diastolic blood pressures were below normal more than 9 years after diagnosis. Even patients receiving lower cumulative doxorubicin doses experienced reduced mass and dimension. Fractional shortening and dimension at the end of therapy predicted these parameters 11.8 years later.

CONCLUSION

Cardiac abnormalities were persistent and progressive after doxorubicin therapy. Inadequate ventricular mass with chronic afterload excess was associated with progressive contractile deficit and possibly reduced cardiac output and restrictive cardiomyopathy. The deficits were worst after highest cumulative doses of doxorubicin, but appeared even after low doses.

Enalapril to prevent cardiac function decline in long-term survivors of pediatric cancer exposed to anthracyclines

PURPOSE

To determine whether an angiotensin-converting enzyme (ACE) inhibitor, enalapril, prevents cardiac function deterioration (defined using maximal cardiac index [MCI] on exercise testing or increase in left ventricular end-systolic wall stress [LVESWS]) in long-term survivors of pediatric cancer.

PATIENTS AND METHODS

This was a randomized, double-blind, controlled clinical trial comparing enalapril to placebo in 135 long-term survivors of pediatric cancer who had at least one cardiac abnormality identified at any time after anthracycline exposure.

RESULTS

There was no difference in the rate of change in MCI per year between enalapril and placebo groups (0.30 v 0.18 L/min/m(2); P =.55). However, during the first year of treatment, the rate of change in LVESWS was greater in the enalapril group than in the placebo group (-8.59 v 1.85 g/cm(2); P =.033) and this difference was maintained over the study period, resulting in a 9% reduction in estimated LVESWS by year 5 in the enalapril group. Six of seven patients removed from random assignment to treatment because of cardiac deterioration were initially treated with placebo (P =.11), and one has died as a result of heart failure. Side effects from enalapril included dizziness or hypotension (22% v 3% in the placebo group; P =.0003) and fatigue (10% v 0%; P =.013).

CONCLUSION

Enalapril treatment did not influence exercise performance, but did reduce LVESWS in the first year; this reduction was maintained over the study period. Any theoretical benefits of LVESWS reduction in this anthracycline-exposed population must be weighed against potential side effects from ACE inhibitors when making treatment decisions.

Aortic stenosis

Valvular aortic stenosis in pediatric age group is mostly congenital in origin. The aortic valve may be unicuspid, bicuspid, tricuspid or rarely quadricuspid. Left ventricle undergoes concentric hypertrophy secondary to obstruction to its outflow tract. In neonatal aortic stenosis, left ventricle may be hypoplastic. The pathophysiology and clinical presentation vary with the age of onset and severity of obstruction. Echocardiography and Doppler are indispensible for the diagnosis of aortic stenosis and its severity. Cardiac catheterization is not necessary for the diagnosis, however it is performed as a part of balloon aortic valvuloplasty in severe cases. Balloon valvuloplasty is an effective alternative to surgery in pediatric age group. Some of these patients require surgical valve repair or replacement on follow-up. Neonates and young infants with critical aortic stenosis present with cardiogenic shock and need aggressive treatment with prostaglandin E1 infusion along with inotropic support. In experienced hands, balloon valvuloplasty is a safe procedure in neonates and infants with critical stenosis. Patients with mild and moderate aortic stenosis may be left on medical follow-up.

Wall stress misrepresents afterload in children and young adults with abnormal left ventricular geometry

Wall stress, although commonly used as an index of afterload, fails to take into account forces generated within the wall of the left ventricle (LV) that oppose systolic fiber shortening. Wall stress may, therefore, misrepresent fiber stress, the force resisting fiber shortening, particularly in the presence of an abnormal LV thickness-to-dimension ratio (h/D). M-mode LV echocardiograms were obtained from 207 patients with a wide range of values for LV mass and/or h/D. Diagnoses were valvar aortic stenosis, coarctation repair, anthracycline treated, and severe aortic and/or mitral regurgitation. End-systolic wall stress (WS(es)) and fiber stress (FS(es)) were expressed as age-corrected Z scores relative to a normal population. The difference between WS(es) and FS(es) was extreme when h/D was elevated or reduced [WS(es) Z score - FS(es) Z score = 0.14 x (h/D)(-1.47) - 2.13; r = 0.78, P < 0.001], with WS(es) underestimating FS(es) when h/D was increased and overestimating FS(es) when h/D was decreased. Analyses of myocardial mechanics based on wall stress have limited validity in patients with abnormal ventricular geometry.

Echocardiographic prediction of clinical outcome in medically treated patients with aortic stenosis

BACKGROUND

The onset of symptoms is crucial in the natural history of severe aortic stenosis. In contrast, the impact of the degree of valve obstruction and left ventricular dysfunction on clinical outcome in terms of progression of symptoms and mortality is undefined.

METHODS AND RESULTS

Between April 1989 and June 1996, 108 patients (75% male, aged 68.7 +/- 10.3 years) with pure and isolated aortic stenosis of at least moderate degree had a complete Doppler echocardiography. Left ventricular end-diastolic and end-systolic diameters, thickness of ventricular septum, mass and ejection fraction, and maximal instantaneous aortic gradient were measured. Patients were followed up through March 1999. Sixty-five patients who underwent aortic valve replacement were censored at the time of surgery. The end point was considered to be death or symptomatic progression (onset of new symptoms or worsening of symptoms). At the time of diagnosis 64 (59%) were in New York Heart Association (NYHA) class I-II and 44 (41%) in NYHA class III-IV. After a mean follow-up of 46 +/- 21 months 6 patients died and 45 had worsening of symptoms. Univariate predictors of clinical outcome (death and worsening of symptoms) included left ventricular end-diastolic diameter (hazard ratio 1.03, P =.08), left ventricular end-systolic diameter (HR 1.04, P =.012), and left ventricular septum thickness (HR 1.14, P =.009) but not the degree of aortic obstruction. Multivariate predictors of clinical outcome were left ventricular septum thickness (P =.016) and left ventricular end-systolic diameter (P =.008).

CONCLUSION

In patients with various degrees of aortic stenosis the rate of clinical outcome is predicted by left ventricular function and septum thickness. Therefore both the left ventricular and aortic valve gradients should be taken into account when choosing the timing of intervention.

Effect of myocardial hypertrophy on systolic and diastolic function in children: insights from the force-frequency and relaxation-frequency relationships

OBJECTIVE

The objective of this study was to evaluate the effect of myocardial hypertrophy on systolic and diastolic properties of the left ventricle in children.

BACKGROUND

In children with myocardial hypertrophy, ejection phase indices are invariably increased. However, indices of force-generation, e.g., end-systolic elastance and invasive indices of diastolic properties, have been studied infrequently in children with myocardial hypertrophy.

METHODS

We studied 10 children with congenital aortic stenosis or coarctation of aorta and nine control patients. Systolic properties were assessed from shortening fraction, end-systolic fiber elastance (Ef(es)) measured at resting heart rates, and force-frequency relationship measured at heart rates increasing from 110 to 160 beats per minute. Diastolic properties were assessed from time constant of relaxation (tau) at matched heart rates, chamber stiffness constant, myocardial stiffness constant, and relaxation-frequency relationship measured at gradually increasing heart rates.

RESULTS

Ef(es) remained unchanged by myocardial hypertrophy, however, tau was prolonged (tauL: 27.3+/-2.3 vs. 21.8+/-2.2 ms, p < 0.001; and tauD: 43.2+/-3.1 vs. 34.3+/-3.3 ms, p < 0.001). Both chamber and myocardial stiffness constants remained unchanged. Incremental increases in heart rate produced incremental improvement in both contraction and relaxation. Slopes of force-frequency and relaxation-frequency relationships remained unchanged in the experimental group. However, the relaxation-frequency relationship manifested a parallel shift upward.

CONCLUSIONS

In conscious, sedated children with myocardial hypertrophy, systolic function assessed by an index of force generation remains unchanged. However, relaxation is prolonged but passive diastolic properties remain unaffected. The combined effect of hypertrophy and heart rate does not alter the force-frequency and relaxation-frequency relationships.

Evaluation of ventricular and arterial hemodynamics in anesthetized closed-chest mice

Transgenic and knock-out mice with cardiovascular phenotypes have created the need for methods to measure murine arterial and ventricular mechanics. The aims of this study were (1) to develop a method for the assessment of wall stress (sigma es)-rate corrected velocity of fiber shortening (Vcfc) relation and (2) to assess the feasibility of quantifying global arterial function in normal mice. This method can thus serve as a reference for future studies in genetically altered mice by establishing normal values for comparison. Ten anesthetized closed-chest mice were studied with targeted M-mode echocardiography of the left ventricle recorded simultaneously with high-fidelity aortic pressures. Data were acquired at baseline and during infusions of methoxamine and isoproterenol. Tracings were digitized to obtain end-systolic wall stress (sigma es) and rate-corrected velocity of fiber shortening (Vcfc) relationships and plots of systolic meridional wall stress. Instantaneous aortic pressures and continuous wave aortic Doppler velocities were digitized to study arterial hemodynamics. The Vcfc-sigma es relationship was inverse and linear in all mice studied with a median value of r2 = 0.94. Isoproterenol resulted in an upward shift from the baseline contractility line obtained with methoxamine (mean shift = 2.0 +/- 0.3 circ/sec). Relative to baseline the integral of wall stress decreased with isoproterenol and increased with methoxamine. Methoxamine increased mean arterial pressure and total vascular resistance and decreased heart rate, cardiac output, and arterial compliance. Isoproterenol decreased total vascular resistance and increased cardiac output. Stress-shortening relationships, systolic wall stress, and evaluation of vascular function can be obtained in a closed-chest mouse model.

Function of the transplanted heart: unique physiology and therapeutic implications

Orthotopic heart transplantation has become an established treatment for selected patients with refractory heart failure. Long-term survival rates are superior to those resulting from other forms of therapy for that patient population. In addition, an improved quality of life has been reported by many patients. However, despite these encouraging results, the transplanted heart does not provide the recipient with normal cardiac function. Cardiac physiology after heart transplantation is unique. Resting hemodynamics differ significantly, acutely and chronically, from those seen in healthy subjects. In addition, neural mechanisms undergo changes as a result of surgical denervation. Afferent control mechanisms and efferent responses both are altered, leading to important clinical abnormalities. Examples include altered cardiovascular responses to exercise, altered cardiac electrophysiology, and altered responses to cardiac pharmacologic agents. An improved understanding of the changes in cardiac physiology, which occur after heart transplant, may allow the care of these patients to be optimized.

Mechanics of left ventricular systolic and diastolic function in physiologic hypertrophy of the athlete's heart

As a result of a number of factors, there is tremendous diversity in the pattern of cardiac mechanics encountered in athletes. Nevertheless, several trends can be identified, and several conclusions are possible. Hypertrophy of a mild to moderate degree and out of proportion to body size is a common finding. Some athletes experience ventricular dilation with appropriate hypertrophy and preservation of the ventricular mass-to-volume ratio, whereas others manifest concentric hypertrophy with an increased mass-to-volume ratio. The functional changes that are encountered appear to be secondary to the structural alterations, and there is no evidence of altered myocardial systolic or diastolic properties. Some athletes with hypertrophy have reduced wall stress when they are evaluated at rest, and velocity of shortening is augmented because of the reduced afterload. As a result of adaptation to a high-output state, some athletes appear preload reduced when evaluated at rest. Although velocity of shortening is not affected by preload status, fractional shortening is inversely related to preload. The magnitude of systolic shortening is therefore the net result of altered preload and afterload and cannot be understood without assessing both of these parameters. When the various determinants of systolic shortening are included, contractility appears to be normal. There have been several reports of depressed contractility immediately after extreme exertion. Although the mechanism remains uncertain, several intriguing possibilities have been proposed.

Influence of post-surgery time after cardiac transplantation on exercise responses

Influence of post-surgery time after cardiac transplantation on exercise responses. Med. Sci. Sports Exerc., Vol. 28, No. 2, pp. 171-175, 1996. To test the hypothesis that exercise response changes with time after cardiac transplantation, we investigated the cardiorespiratory responses of nine orthotopic heart transplant patients (52.4 +/- 2 yr) during graded exercise tests (30 W.3 min-1) done at 1, 3, 6, 9 and 12 months post-surgery. At peak exercise, 1) oxygen uptake per kg of body weight (VO2), minute ventilation (VE) and oxygen pulse (O2 pulse) did not change significantly between 1 and 12 months postsurgery; 2) transplanted heart rate (HRt) and delta heart rate (peak exercise heart rate--resting heart rate) increased significantly over time (P < 0.01; P < 0.05) with a marked increase between 1 and 3 months (P < 0.05); and (3) a significant negative correlation existed between O2 pulse and HRt (r = -0.36, P < 0.05), whereas no correlation was found between delta heart rate and delta VO2 (peak exercise VO2- resting VO2, l.min-1). During submaximal exercise, HRt increased significantly over time (P < 0.001); VO2, VE, and O2 pulse showed no significant change; and the VO2-HRt relationship shifted toward higher values of HRt. We conclude that, in the absence of formal physical training, the exercise response of denervated transplanted heart increases in relation to post-surgery time but does not affect oxygen uptake at submaximal and peak levels of exercise.

Effect of donor-recipient size mismatch on left ventricular remodeling after pediatric orthotopic heart transplantation

Left ventricular (LV) hypertrophy has been reported after orthotopic heart transplantation. This study was designed to determine the pattern of LV remodeling in the first year after pediatric orthotopic heart transplantation and to elucidate the mechanism responsible for changes in LV dimensions. Serial echocardiograms of 20 children who underwent cardiac transplantation were analyzed off-line, and the following LV parameters were measured and indexed to body surface area (BSA): short-axis diameters, posterior wall thickness, length, mass, and volume in systole and diastole. Mass/volume and short-axis diameter/length ratios and ejection fraction were calculated. In 5 patients, the donor's echocardiogram was also available for analysis. The patient's systemic blood pressure at the time of the echocardiogram, ischemic time of the donor heart, number of rejection episodes, biopsy scores, and body size of the donor and patient were recorded. Patients were assigned to 2 groups based on their donor-recipient weight ratio:group 1, < or = 1.2 (n = 9); and group 2, > 1.2 (n = 11). In group 1, LV mass index remained within normal limits throughout the study period. In group 2, mass index was significantly increased 2 weeks after transplantation (72 +/- 24 vs 133 +/- 37 g/BSA1.5, p = 0.0008). LV volume, geometry, ejection fraction, systemic blood pressure, and number of rejection episodes did not differ significantly between groups. The excess LV mass index in group 2 regressed significantly during the first year after transplantation from 133 +/- 37 to 93 +/- 17 g/BSA1.5 (p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Status of the left ventricle after arterial switch operation for transposition of the great arteries. Hemodynamic and echocardiographic evaluation

BACKGROUND

The potential for improved preservation of systemic ventricular function represents an important reason for the increasing popularity of the arterial switch operation. In support of this expectation, prior studies in patients early after arterial switch operation have found normal ventricular contractility and function. This study was conducted to extend those observations to up to 10 years of follow-up and to directly examine the effects of a coexisting ventricular septal defect or short-term preparatory banding of the pulmonary artery before the arterial switch operation.

METHODS

Patients operated on from 1983 through 1991 were included. Echocardiographic and catheterization data were collected as part of a prospective evaluation of outcome in all patients who undergo the arterial switch operation at Boston Children's Hospital, with inclusion of data from the most recent catheterization only. Echocardiograms performed at least 6 months after the operation were included, with assessment of both the most recent status as well as serial trends. Whenever possible, echocardiographic evaluation included data necessary to perform analysis of ventricular mechanics including indices of afterload, preload, and contractility. Comparison was made to normal values and between subgroups defined on the basis of an arterial switch operation with or without ventricular septal defect and those who had a rapid two-stage arterial switch operation.

RESULTS

Invasive measures of left and right ventricular filling pressures, cardiac index, and pulmonary vascular resistance did not differ among the three groups. Overall, echocardiographic left ventricular end-diastolic dimension, wall thickness, mass, afterload (end-systolic wall stress), function (fractional shortening and rate-corrected velocity of fiber shortening), contractility (stress-velocity and stress-shortening relations), and preload were normal, and none of these variables was different between the groups with and without a ventricular septal defect. Serial evaluation indicated a slight but significant trend toward ventricular dilatation, perhaps related to a relatively high incidence of at least mild aortic regurgitation (30%). In contrast, in the rapid two-stage group the echocardiographic indices of left ventricular function (fractional shortening and velocity of fiber shortening) and contractility (stress-velocity and stress-shortening relations) were found to be mildly but significantly reduced compared with normal subjects and with the other arterial switch operation groups. Over the duration of follow-up encompassed by this study, no tendency toward progressive depression of function was seen.

CONCLUSIONS

As the length of observation after the arterial switch operation continues to increase, left ventricular size, mass, functional status, and contractility continues to be normal, with no evidence of time-related deterioration of function. As previously reported, the rapid two-stage arterial switch operation does represent a higher risk for mild impairment of myocardial mechanics.

Limitations of fractional shortening as an index of contractility in pediatric patients infected with human immunodeficiency virus

Left ventricular fractional shortening (FS) is dependent on left ventricular preload and afterload, as well as contractility. Contractility may therefore not be accurately described by FS, especially in infants and children infected with human immunodeficiency virus (HIV), who tend to have abnormal left ventricular preload and afterload. We therefore examined the magnitude and clinical impact of the discrepancy between FS and contractility by assessment of 177 echocardiograms from 76 HIV-infected pediatric patients (median age, 1.9 years). The studies included simultaneous measurements of left ventricular FS, contractility, preload, and afterload. The correlation between contractility and FS was modest (r = 0.70; p < 0.001), and was weaker in children less than 2 years of age (r = 0.52) than in older children (r = 0.84). FS incorrectly predicted contractility in 46% of the studies; 43% with depressed FS (< 28%) had either normal (17/42) or enhanced (1/42) contractility. For 67% of echocardiograms, FS and contractility differed by > 1 SD, and for 36% the difference was > 2 SD. These differences remained after adjustment of FS for age or body surface area. Afterload was abnormal in 42% and preload in 21% of all echocardiograms. High preload predicted that FS would overestimate contractility (p = 0.002); high afterload predicted that FS would underestimate contractility (p < 0.001). The discrepancy between FS and contractility was larger among children who were younger, had more advanced HIV disease, or were not sedated during echocardiography. One third of children with congestive symptoms had normal contractility and depressed FS; the discrepancy was primarily due to loading conditions. We conclude that the high incidence of abnormal loading conditions in HIV-infected infants and children limits the usefulness of load-dependent FS for assessing contractility. Measurements of loading conditions and load-independent indexes, which more directly reflect contractility, allow a more accurate determination of myocardial status and may lead to better clinical management.

Left ventricular contractile state in preterm infants: relation between wall stress and velocity of circumferential fiber shortening

Fetal and newborn lambs' hearts have limited capacity to adapt to increased afterload. In human preterm infants, however, this limited left ventricular pump function has not been investigated. To determine the normal left ventricular resting contractile state in preterm infants, we studied the relation of end-systolic wall stress to the rate-corrected velocity of circumferential fiber shortening (VCF) in 11 preterm infants of gestational ages 28 to 36 weeks. We performed the first (7 to 14 days of postnatal age) and the second (29 to 39 days of postnatal age) examinations. There was a significant inverse linear correlation between wall stress and VCF in the first and the second examinations (r = -0.616 and r = -0.715, respectively). Both regression lines had slopes that were steeper than those previously reported for older age groups. The preterm infants had high VCF values (mean 1.05 and 1.09 cir/sec, respectively) and low-wall stress values (mean 36.0 and 36.9 gm/cm2, respectively) in the first and the second examinations. We therefore suggest that the preterm infants have a high resting contractile state, but left ventricular performance may deteriorate in the face of increased afterload.

Non-invasive estimates of aortic root pressures: external subclavian arterial pulse tracing calibrated by oscillometrically determined brachial arterial pressures

This investigation assessed the ability of a non-invasive method to reproduce aortic root pressure waveform and pressures. An external pulse tracing of the subclavian artery was obtained simultaneously with direct aortic root pressures during routine left heart catheterization in 26 patients (aged 39-74 years) with various cardiovascular disorders. Indirect brachial arterial peak-systolic and nadir-diastolic pressures were obtained with oscillometry. The direct and indirect peak-systolic and nadir-diastolic pressures, were separately used to calibrate the pulse tracing. Adequate pulse tracing was obtained in 19 patients (73%). The waveforms agreed well with cross-correlation coefficients for systole and diastole of 0.98. The difference between the pulse trace and the direct pressure curve, when the first was calibrated with the peak-systolic and nadir-diastolic pressures of the latter on average was less than 1 mmHg for systole and diastole. At end-systole the mean difference was 5 mmHg. Oscillometric brachial arterial peak-systolic pressures were (mean +/- SD) 3 +/- 7 mmHg below the corresponding direct measurements, while diastolic pressures were 8 +/- 4 mmHg above. The difference between the pulse trace and the direct pressure curve, when the pulse trace was calibrated with oscillometric pressures, was at end-systole 6 +/- 6 mmHg and for mean arterial pressures 5 +/- 4 mmHg. Thus, the external subclavian arterial pulse tracing provides a non-invasive, clinically feasible access to the aortic root pressure waveform. With optimal calibration, good estimates of aortic root pressures throughout systole and diastole can be obtained, while end-systolic pressure tends to be slightly overestimated.

Developmental modulation of myocardial mechanics: age- and growth-related alterations in afterload and contractility

Somatic growth is associated with alterations in myocardial mechanics in children with heart disease and in most animal models of congenital heart disease. However, the effect of age and body size on myocardial contractility and loading conditions in normal infants and children is not known. Therefore, 256 normal children aged 7 days to 19 years (34% less than 3 years old) were evaluated with noninvasive indexes of left ventricular contractility and loading conditions. Two-dimensional and M-mode echocardiographic recordings of the left ventricle were obtained with a phonocardiogram, indirect pulse tracing and blood pressure recordings. Left ventricular dimensions, wall thickness and pressure measurements obtained from these data were used to calculate peak and end-systolic circumferential and meridional wall stress and mean and integrated meridional wall stress. Velocity of shortening adjusted for heart rate was compared with end-systolic stress to assess contractility independently of loading status. The subjects were stratified for gender and each of the derived variables was related to age and body surface area. Ventricular shape, assessed as the major/minor axis ratio, and the circumferential/meridional stress ratio were found to be invariant with growth. The ratio of posterior wall thickness to minor axis dimension did not change with age, despite the normal age-related increase in blood pressure. The increase in pressure despite unvarying ventricular shape and wall thickness/dimension ratio resulted in a substantial increase in wall stress that was most dramatic during the first few years of life. In association with the increase in afterload, systolic function decreased with age. However, the age-related decrease in the velocity of shortening was greater than that expected from the increase in afterload alone, indicating a higher level of contractility in infants and children during the first years of life than in older subjects. The process of normal growth and development, similar to that in children with heart disease, is associated with a rapid decrease in the trophic response to hemodynamic loads, resulting in an age-associated increase in wall stress. There is a similar but somewhat more rapid decrease in contractility, with the highest values seen in the youngest patients.

Maximal voluntary exercise variables in children with postoperative coarctation of the aorta

Thirty-one children with postoperative coarctation of the aorta underwent maximal graded bicycle ergometry using an electronically braked ergometer and the James protocol; 18 also underwent expiratory gas measurement using a mass spectrometer. Twenty-two age- and gender-matched normal subjects were used as a control group. The mean age at operation was 41 months and the mean age at evaluation was 134 months (mean follow-up interval 93 months). The original surgical repair was subclavian flap repair in 8 patients, end to end anastomosis in 21, patch aortoplasty in 1 patient and tubular graft in 1. Patients exercised until exhaustion and maximal exercise variables were obtained. The maximal voluntary peak heart rate was 183 beats/min (94.6% of predicted value), indicating excellent effort. Mean power was 111% of predicted value and, when measured, maximal oxygen consumption was 89% of predicted value with an anaerobic threshold at 63 +/- 3.5% of exercise time. The observed work variables were not different from values in the control group and were not affected by the type of repair. The mean peak systolic blood pressure was 152 +/- 7.6 mm Hg versus 147 +/- 5.7 mm Hg in the control group (p = NS). Patients who had associated intracardiac lesions had significantly lower maximal oxygen consumption (85 +/- 3% vs. 98 +/- 4% of predicted value). The results suggest that adequate cardiopulmonary function, normal or above average work capacity and normal exercise systolic blood pressure can be obtained in children with satisfactory repair of coarctation of the aorta performed before school age.

Effect of digoxin on contractility and symptoms in infants with a large ventricular septal defect

The effect of digoxin on contractility and symptoms in infants with a large ventricular septal defect (VSD) is controversial. Nineteen infants with symptoms of congestive heart failure due to a VSD were studied with load-independent indexes during 4 study periods: (1) before any medication; (2) while on chronic diuretics; (3) while on both diuretics and digoxin; and (4) while on diuretics alone, to determine if digoxin: (a) increases "contractility" when added to diuretic therapy; and (b) improves symptoms. Symptoms, signs (heart and respiratory rates, and weight gain), shortening fraction, preload (left ventricular end-diastolic dimension), afterload (left ventricular end-systolic wall stress) and contractility were measured at each period. The difference between the measured and predicted velocities of circumferential fiber shortening for the measured left ventricular end-systolic wall stress served as an index of contractility. Eighteen infants also underwent catheterization. Mean pulmonary-to-systemic blood flow ratio was 3:1. When digoxin was added to diuretics, contractility index was significantly greater than in control subjects (0.13 +/- 0.15 vs 0.0 +/- 0.12 circ/s, p = 0.04). When patients were again on diuretics alone (after discontinuation of digoxin), contractility index was no longer different. Symptoms and signs were not significantly improved by either diuretics or digoxin. It is concluded that in infants with a large left-to-right VSD shunt and receiving digoxin and diuretics, contractility index was significantly greater than in control subjects. However, neither diuretics alone nor in combination with digoxin improved symptoms significantly.

Effects of percutaneous mitral valvuloplasty on left ventricular mass and volume

The response of left ventricular (LV) geometry to altered loading conditions after mitral valvuloplasty has been incompletely described. Therefore, 15 patients with rheumatic mitral stenosis were studied using quantitative 2-dimensional echocardiography a mean of 1 +/- 2 months before and 11 +/- 5 months after percutaneous balloon mitral valvuloplasty. Mitral valve area (Gorlin) increased in all patients, from 1.0 +/- 0.3 to 1.9 +/- 0.5 cm2 (p less than 0.01). Mitral regurgitation (1+/4+) developed in 3 patients, and increased by 1 grade in 1 patient as a consequence of mitral valvuloplasty. After valvuloplasty, there were significant increases in LV end-diastolic volume (69 +/- 22 to 82 +/- 26 ml, p less than 0.01), stroke volume (34 +/- 13 to 46 +/- 19 ml, p less than 0.05) and mass (181 +/- 46 to 200 +/- 42 ml, p less than 0.005). LV end-systolic volume and ejection fraction did not change significantly. LV mass-to-volume ratio was unchanged (5.6 +/- 1.5 to 5.8 +/- 1.4 g/ml, p = not significant). Quantitatively similar results were obtained when these changes were indexed to body surface area. Thus, successful mitral valvuloplasty was associated with significant increases in LV end-diastolic volume and mass. These findings suggest that increased preload may be a stimulus to myocardial growth.

Left ventricular mass in childhood dilated cardiomyopathy: a possible predictor for selection of patients for cardiac transplantation

To determine the relationship of left ventricular hypertrophy (as assessed by mass) to symptoms and cardiac function in chronic childhood dilated cardiomyopathy, 17 long-term survivors (12 asymptomatic, 5 symptomatic) were studied at a median follow-up of 6.25 years (1.25 to 16.8 years). Left ventricular mass, dimension, wall stress, and contractility (relationship between velocity of circumferential fiber shortening and end-systolic wall stress) were assessed by echocardiography. These data were compared to measurements at the onset of disease. At follow-up, mass decreased significantly from the onset in the asymptomatic patients but remained elevated in the symptomatic patients (101 +/- 35 gm/m2 to 54 +/- 12 gm/m2, p = 0.001; 122 +/- 55 gm/m2 to 198 +/- 115 gm/m2, p = 0.23, respectively). Shortening fraction and contractility were both significantly lower in the symptomatic group compared with the asymptomatic group at follow-up (shortening fraction = 21 +/- 7% vs 29 +/- 5%, p = 0.02; contractility = -0.24 +/- 0.14 circ/sec vs -0.05 +/- 0.11 circ/sec, p = 0.01). Follow-up wall stress was slightly higher in symptomatic patients compared with asymptomatic patients. Three symptomatic patients had progressive hypertrophy and either died or required transplantation. Higher left ventricular mass is associated with the presence of symptoms, depressed contractility, and slightly higher wall stress. Persistence or progression of hypertrophy may be a poor prognostic sign in survivors of childhood dilated cardiomyopathy. Measurement of mass may be useful to indicate the necessity for closer follow-up to select patients for cardiac transplantation before hemodynamic decompensation.

Relation of symptoms to contractility and defect size in infants with ventricular septal defect

Forty-two infants with a ventricular septal defect (VSD) (21 asymptomatic and 21 symptomatic) were compared with 17 control infants to determine if symptoms of congestive heart failure (i.e., tachypnea/poor growth) were due to depressed contractility or defect size, or both. Echocardiographic indexes of defect size, left ventricular performance (shortening fraction), preload (left ventricular end-diastolic dimension), afterload (left ventricular end-systolic wall stress) and contractility (the relation between velocity of circumferential fiber shortening and wall stress) were measured. Clinical assessment included measurement of weight and respiratory rate. Pulmonary and systemic blood flow were assessed in 17 symptomatic and 3 asymptomatic patients by cardiac catheterization. Although there was no significant difference in age, the symptomatic group had significantly lower weight (5.5 +/- 2.9 vs 7.3 +/- 2.3 kg, p less than 0.05) and a higher respiratory rate (53 +/- 14 vs 43 +/- 6 breaths/min, p less than 0.05), compared with control subjects. The mean pulmonary to systemic blood flow ratio in the symptomatic group was 2.9:1. Preload indexed for body surface area was significantly higher in the groups with a VSD compared with control subjects (asymptomatic, 8.5 +/- 1.7 cm/m2; symptomatic, 9.1 +/- 1.7 cm/m2; control subjects, 6.8 +/- 1.1 cm/m2; p less than 0.05). Shortening fraction, afterload and contractility were not significantly different among all groups. A defect size greater than 0.5 cm (or defect size indexed for body surface area greater than 1.8 cm/m2) was predictive of the presence of symptoms. It is concluded that contractility is normal in infants with a VSD. Symptoms may be related to pulmonary congestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Late cardiac effects of doxorubicin therapy for acute lymphoblastic leukemia in childhood

BACKGROUND

Cardiotoxicity is a recognized complication of doxorubicin therapy, but the long-term effects of doxorubicin are not well documented. We therefore assessed the cardiac status of 115 children who had been treated for acute lymphoblastic leukemia with doxorubicin 1 to 15 years earlier in whom the disease was in continuous remission.

METHODS

Eighteen patients received one dose of doxorubicin (45 mg per square meter of body-surface area), and 97 received multiple doses totaling 228 to 550 mg per square meter (median, 360). The median interval between the end of treatment and the cardiac evaluation was 6.4 years. Our evaluation consisted of a history, 24-hour ambulatory electrocardiographic recording, exercise testing, and echocardiography.

RESULTS

Fifty-seven percent of the patients had abnormalities of left ventricular afterload (measured as end-systolic wall stress) or contractility (measured as the stress-velocity index). The cumulative dose of doxorubicin was the most significant predictor of abnormal cardiac function (P less than 0.002). Seventeen percent of patients who received one dose of doxorubicin had slightly elevated age-adjusted afterload, and none had decreased contractility. In contrast, 65 percent of patients who received at least 228 mg of doxorubicin per square meter had increased afterload (59 percent of patients), decreased contractility (23 percent), or both. Increased afterload was due to reduced ventricular wall thickness, not to hypertension or ventricular dilatation. In multivariate analyses restricted to patients who received at least 228 mg of doxorubicin per square meter, the only significant predictive factors were a higher cumulative dose (P = 0.01), which predicted decreased contractility, and an age of less than four years at treatment (P = 0.003), which predicted increased afterload. Afterload increased progressively in 24 of 34 patients evaluated serially (71 percent). Reported symptoms correlated poorly with indexes of exercise tolerance or ventricular function. Eleven patients had congestive heart failure within one year of treatment with doxorubicin; five of them had recurrent heart failure 3.7 to 10.3 years after completing doxorubicin treatment, and two required heart transplantation. No patient had late heart failure as a new event.

CONCLUSIONS

Doxorubicin therapy in childhood impairs myocardial growth in a dose-related fashion and results in a progressive increase in left ventricular afterload sometimes accompanied by reduced contractility. We hypothesize that the loss of myocytes during doxorubicin therapy in childhood might result in inadequate left ventricular mass and clinically important heart disease in later years.

Changes in cardiac function during extracorporeal membrane oxygenation for persistent pulmonary hypertension in the newborn infant

The effects of extracorporeal membrane oxygenation (ECMO) on cardiac function and its determinants (preload, afterload, contractility, and heart rate) are largely unknown, although some evidence exists that function may decrease. To determine whether cardiac function decreases and what changes in the determinants take place during and after ECMO, we observed 26 newborn infants with persistent pulmonary hypertension. Serial echocardiograms were performed before ECMO, during maximum cardiopulmonary bypass, and after ECMO. Cardiac function was assessed by using standard echographic ejection phase indices (shortening fraction and cardiac output). Heart rate, preload (left ventricular end-diastolic dimension and area), afterload (left ventricular end-systolic wall stress), and contractility (relationship between velocity of circumferential fiber shortening and wall stress) were also measured. Ejection phase indices significantly decreased during ECMO (shortening fraction 33% to 25%, cardiac output 205 to 113 ml/kg/min; p less than 0.05) and returned to normal after ECMO (shortening fraction 26% to 34%, cardiac output 107 to 240 ml/kg/per minute; p less than 0.05). Heart rate also significantly decreased during ECMO (158 to 118 beats/min; p less than 0.05). Preload significantly increased after ECMO (left ventricular end-diastolic dimension 1.4 to 1.6 cm, left ventricular end-diastolic area 1.9 to 2.2 cm2; p less than 0.05). There were no significant changes in contractility and afterload during any study period. We conclude that, although left ventricular ejection phase indices and heart rate decreased during ECMO, these changes were transient and resolved when bypass was terminated. Contractility and afterload did not appear affected by bypass.

Mitral valve prolapse and occult aortic coarctation

A 22 year old man developed symptoms of left ventricular failure secondary to atrial fibrillation and congenital mitral regurgitation. After operation for mitral valve repair he was unable to be successfully weaned from cardiopulmonary bypass and this was ascribed to poor left ventricular function. He therefore underwent emergency cardiac transplantation but again was unable to be weaned from bypass. At post-mortem examination a previously undiagnosed aortic coarctation was revealed. The presentation of occult aortic coarctation is discussed, and its association with congenital mitral valve abnormalities reviewed.

Normal values for noninvasive estimation of left ventricular contractile state and afterload in children

The outcome and suitability for therapeutic interventions in children with congenital heart disease depend frequently on left ventricular function. Congenital heart disease is characterized by changes in loading conditions, making it difficult to assess ventricular contractility using conventional load-dependent indexes. Two-dimensional and M-mode echocardiography and arterial blood pressure were used to study left ventricular morphometrics and contractility in 44 normal children, aged 2 to 12 years. Left ventricular end-systolic and end-diastolic length, diameter, wall thickness, volume and mass all showed linear increases with body surface area (p less than 0.001 in all). Shortening and ejection fractions, velocity of circumferential fiber shortening, morphometric ratios and endocardial meridional and circumferential stress (mean 46 and 115 g/cm2, respectively) all remained constant. A load-independent measure of the normal resting left ventricular contractile state was determined by relating the rate-corrected velocity of circumferential fiber shortening to end-systolic endocardial meridional and circumferential stress; there was an inverse linear correlation (r = -0.641 and -0.557 respectively, p less than 0.001). These data provide a quantitative basis for assessment of myocardial hypertrophy, afterload and contractile state in childhood.

Preoperative left ventricular wall stress, ejection fraction, and aortic valve gradient as prognostic indicators in aortic valve stenosis

Patients with aortic valve stenosis (AS) and left ventricular (LV) dysfunction may dramatically improve after aortic valve replacement, but operative risk is high. In an earlier study, all patients with low preoperative wall stress and low ejection fraction, or with low aortic valve gradient, died or had persistent heart failure after operation. Because wall stress is difficult to calculate, we reassessed its effect and the effect of other preoperative characteristics on outcome in 66 consecutive catheterization patients with predominant aortic stenosis referred for valve replacement. Despite ejection fraction that was inordinately low compared with afterloading wall stress in nine patients, seven patients improved with surgery. All three patients with ejection fraction less than 20% improved after surgery. Two of three patients with mean aortic valve gradients of less than 30 mm Hg improved. Mortality was 33% in patients with mean gradient less than 30 mm Hg and 19% with mean gradient less than 50 mm Hg. In the 54 patients with calculated aortic valve areas of less than or equal to 0.8 cm2, 1 (2%) had continuing heart failure, while 6 of 12 (50%, P less than .01) patients with aortic valve areas of 0.9-1.2 cm2 had continued symptoms of or died of heart failure. Patients who died or failed to improve after operation were older (71 +/- 9 years) than those who improved (65 +/- 9 years, P = .02). We conclude that wall stress calculations do not predict which patients with aortic stenosis will benefit from aortic valve replacement and that poor left ventricular function and low mean aortic valve gradient do not absolutely preclude operation. On the other hand, low gradient, non-critical valve area, and advanced age are all relative contraindications to aortic valve replacement in aortic stenosis.

Supernormal ejection performance is isolated to the ipsilateral congenitally pressure-overloaded ventricle

Congenital left ventricular pressure overload is associated with "excessive" hypertrophy that leads to subnormal afterload (wall stress), permitting enhanced ventricular ejection performance. Whether congenital right ventricular pressure overload is associated with a similar phenomenon is uncertain. It is also unknown whether supranormal ejection performance affects only the overloaded ventricle or is a general process affecting both ventricles. Conflicting data exist about whether the hypertrophic process associated with pressure overload is induced primarily by local loading conditions or by neuroendocrine influences. If the former postulate is true, the hypertrophic response should be confined to the overloaded ventricle; if the latter is true, one might predict that both ventricles would be affected by a less specific response to circulating catecholamines. To help resolve these issues, both right and left ventricular performance was examined in seven patients with isolated congenital pulmonary stenosis (average pulmonary pressure gradient 78 +/- 13 mm Hg), six patients with isolated congenital aortic stenosis (average gradient 80 +/- 10 mm Hg) and six normal subjects. Right ventricular ejection fraction was increased in patients with pulmonary stenosis (61 +/- 2%) compared with the value in normal subjects (53 +/- 2%, p less than 0.01) and in patients with aortic stenosis (50 +/- 3%, p = 0.007). Left ventricular ejection fraction was increased in patients with congenital aortic stenosis (84 +/- 4%) compared with the value in normal subjects (70 +/- 4%, p less than 0.01) and in patients with congenital pulmonary stenosis (65 +/- 2%, p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of isolated right ventricular outflow obstruction on left ventricular function in infants

Resting left ventricular (LV) function was evaluated in 29 infants with isolated right ventricular (RV) outflow obstruction. Age-corrected cardiac index was significantly inversely correlated with the degree of obstruction (r = 0.59, p = 0.0001). Right ventricular hypertension resulted in septal displacement and altered LV geometry. The magnitude of RV outflow obstruction related closely to the degree of LV distortion. Septal displacement toward the LV free wall was associated with lower values for cardiac index, indexed LV end-diastolic volume, ejection fraction, ratio of early to atrial LV diastolic inflow and with a higher RV ejection fraction. The LV end-diastolic volume index and the ratio of early to atrial LV diastolic inflow correlated with the degree of obstruction and amount of septal displacement. Four infants evaluated during the development of supravalvar pulmonary stenosis demonstrated decreasing cardiac index during development of obstruction and significant increase in cardiac index after surgical relief. These findings indicate that significant RV outflow obstruction in infants is associated with a reversible alteration in LV function related to abnormal LV geometry and impaired LV diastolic filling.

Noninvasive estimation of the left ventricular pressure waveform throughout ejection in young patients with aortic stenosis

Validation of a totally noninvasive method for estimating instantaneous left ventricular pressure and constructing a pressure waveform throughout ejection in patients with aortic stenosis is reported. In 20 patients (aged 8.75 +/- 10 years) with congenital aortic stenosis (measured peak left ventricular pressure 120 to 260 mm Hg; transvalvular gradient 18 to 165 mm Hg), transaortic valve continuous wave Doppler ultrasound, indirect carotid pulse tracing, peripheral blood pressure and measured left ventricular pressure were recorded simultaneously at cardiac catheterization. Data were entered into a microcomputer using a digitizing tablet and the instantaneous Doppler gradient was calculated and added to instantaneous aortic pressure, derived from the time-corrected and calibrated carotid pulse tracing, to estimate instantaneous left ventricular pressure. Estimated left ventricular pressure waveforms reproduced measured left ventricular pressure closely. The mean error at peak left ventricular pressure was 0.2 +/- 4.8 mm Hg (r = 0.98, p = 0.001). The average error throughout ejection was 0.9 +/- 5.1 mm Hg. The error of estimated pressure was not related to age or the severity of aortic stenosis. The Doppler peak instantaneous gradient was observed to correlate closely (r = 0.97, p = 0.001) with peak to peak gradient. With this technique, the left ventricular pressure waveform throughout ejection can be accurately estimated noninvasively in patients with aortic stenosis. This methodology enables determination of mean, total and instantaneous systolic left ventricular pressure.

Dynamic exercise echocardiography in children with congenital heart disease affecting the left heart

Thirty-five children (male 22, female 13) with congenital heart disease resulting in volume and pressure overload of the left ventricle were investigated echocardiographically during supine bicycle exercise. The children had to follow a test-protocol with increasing workload. Left ventricular function parameters were measured from M-mode-echocardiography, electrocardiography and phonocardiograms before, during and after exercise and were expressed as fractional shortening (FS), velocity of circumferential fiber shortening (VcF) and the frequency corrected parameters: FScorr. = FS X 100/HR and VcFcorr. = VcF X 100/HR (HR = heart rate). The data of this group of children under study were compared to those obtained from 140 healthy children examined under similar conditions. In children with pressure overload, values for fractional shortening, velocity of circumferential fiber shortening and the frequency corrected parameters were significantly higher than in normals throughout exercise testing. In some children with moderate to severe aortic stenosis or coarctation the frequency corrected parameters showed a decrease at higher exercise levels instead of an increase as seen in the majority of cases. In these cases cardiac output was increased by an abnormal rise in heart rate. This was considered as a diminished left ventricular reserve. After aortic valve replacement in two cases with aortic stenosis, parameters of left ventricular function were still elevated at rest and during exercise testing. In two children with hypertrophic cardiomyopathy the almost maximally elevated rest values did not change during exercise. In children with mild volume overload (small ventricular septal defect or aortic incompetence) the left ventricular function parameters were within the normal range or slightly below.

Physiologic hypertrophy: effects on left ventricular systolic mechanics in athletes

Physiologic hypertrophy resulting from intense athletic participation has been reported to result in normal, reduced and augmented overall left ventricular performance. Rather than representing true differences in left ventricular contractility, these data may reflect the variable degree of ventricular dilation and increased wall thickness that occur with different types of exercise. As such, the resultant altered loading conditions may diminish the ability of the usual indexes of left ventricular function to accurately assess the left ventricular contractile state. Therefore, three groups of elite athletes with distinct patterns of myocardial hypertrophy were investigated utilizing recently developed load-independent contractility indexes. Age-matched control subjects (n = 33) were compared with 11 swimmers, 11 long-distance runners and 11 power lifters. Rest echocardiogram, phonocardiogram and calibrated carotid pulse tracing were used to calculate left ventricular dimensions, wall thickness, mass, fractional shortening, velocity of shortening and mean, peak and end-systolic wall stresses and the stress-time and minute stress-time integrals. Compared with control subjects, all athletes had increased left ventricular mass, even when values were normalized for body surface area. Runners had a dilated left ventricular and normal wall thickness, swimmers had a mildly dilated ventricle with increased wall thickness and power lifters had normal cavity size with markedly increased wall thickness. Peak systolic wall stress was normal in runners and swimmers and reduced in power lifters, whereas end-systolic stress was low in swimmers and power lifters and normal in runners. The minute stress-time integral, a measure of myocardial oxygen consumption, was normal in runners and swimmers but was significantly reduced in lifters.(ABSTRACT TRUNCATED AT 250 WORDS)