Right ventricular function in congenital heart disease: pressure and volume overload lesions

Metabolic maturation during postnatal right ventricular development switches to heart-contraction regulation due to volume overload

BACKGROUND

Metabolic maturation is one of the primary processes of postnatal cardiomyocyte development. How volume overload (VO), a pathological state of the right ventricle (RV) in children with congenital heart disease (CHD) and patients with heart failure, affects cardiomyocyte metabolic maturation is unclear.

METHODS AND RESULTS

A fistula between the abdominal aorta and inferior vena cava on postnatal day 7 (P7) was created in a mouse model to induce a young-aged RV VO. RNA sequencing revealed that the most enriched gene ontology (GO) terms of the upregulated transcriptome had been changed from metabolic maturation to heart contraction by VO. Transmission electron microscopy imaging showed that metabolic maturation marker-mitochondria were converted into the maturation style in the sham group while remaining unchanged in VO group. Calcium imaging showed that the calcium handling ability had slightly increased in the sham group but dramatically increased in the VO group, even with irregular contraction. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the top three enriched KEGG pathways for the upregulated transcriptome during normal RV development were the citrate cycle, cardiac muscle contraction, and protein processing in the endoplasmic reticulum. VO changed those to arrhythmogenic RV cardiomyopathy, dilated cardiomyopathy, and hypertrophic cardiomyopathy.

CONCLUSIONS

Metabolic maturation of postnatal RV development was partly interrupted by VO, and the underlining mechanism was associated with the activation of cardiomyopathy pathways.

Right Ventricular Fiber Structure as a Compensatory Mechanism in Pressure Overload: A Computational Study

Right ventricular failure (RVF) is a lethal condition in diverse pathologies. Pressure overload is the most common etiology of RVF, but our understanding of the tissue structure remodeling and other biomechanical factors involved in RVF is limited. Some remodeling patterns are interpreted as compensatory mechanisms including myocyte hypertrophy, extracellular fibrosis, and changes in fiber orientation. However, the specific implications of these changes, especially in relation to clinically observable measurements, are difficult to investigate experimentally. In this computational study, we hypothesized that, with other variables constant, fiber orientation alteration provides a quantifiable and distinct compensatory mechanism during RV pressure overload (RVPO). Numerical models were constructed using a rabbit model of chronic pressure overload RVF based on intraventricular pressure measurements, CINE magnetic resonance imaging (MRI), and diffusion tensor MRI (DT-MRI). Biventricular simulations were conducted under normotensive and hypertensive boundary conditions using variations in RV wall thickness, tissue stiffness, and fiber orientation to investigate their effect on RV pump function. Our results show that a longitudinally aligned myocardial fiber orientation contributed to an increase in RV ejection fraction (RVEF). This effect was more pronounced in response to pressure overload. Likewise, models with longitudinally aligned fiber orientation required a lesser contractility for maintaining a target RVEF against elevated pressures. In addition to increased wall thickness and material stiffness (diastolic compensation), systolic mechanisms in the forms of myocardial fiber realignment and changes in contractility are likely involved in the overall compensatory responses to pressure overload.

Right Ventricular Outflow Tract Obstruction: Pulmonary Atresia With Intact Ventricular Septum, Pulmonary Stenosis, and Ebstein's Malformation

OBJECTIVES

The objectives of this review are to discuss the anatomy, pathophysiology, clinical course, and current treatment strategies for pulmonary atresia with intact ventricular septum, pulmonary stenosis, and Ebstein's anomaly.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSIONS

Considerable advances have been made in management strategies for these complex congenital heart lesions, which have led to improved outcomes.

Adaptive capacity of the right ventricle: why does it fail?

Only in recent years has the right ventricle (RV) function become appreciated to be equally important to the left ventricle (LV) function to maintain cardiac output. Right ventricular failure is, irrespectively of the etiology, associated with impaired exercise tolerance and poor survival. Since the anatomy and physiology of the RV is distinctly different than that of the LV, its adaptive mechanisms and the pathways involved are different as well. RV hypertrophy is an important mechanism of the RV to preserve cardiac output. This review summarizes the current knowledge on the right ventricle and its response to pathologic situations. We will focus on the adaptive capacity of the right ventricle and the molecular pathways involved, and we will discuss potential therapeutic interventions.

Isovolumic contraction acceleration before and after percutaneous closure of atrial septal defects

Aim

To compare systemic right ventricular function by isovolumic myocardial acceleration before and 6 months after the percutaneous closure of atrial septal defects (ASD).

Material and methods

Patients admitted to our tertiary center for the percutaneous closure of atrial septal defects between January 2010 and August 2012 constituted the study group. Right ventricular function of patients was assessed by tissue Doppler echocardiography before and after surgery. Echocardiographic data in patients were compared to age-matched controls without any cardiac pathology and studied in identical fashion mentioned below.

Results

A total of 44 patients (24 males, 20 females) and 44 age-matched controls (25 males, 19 females) met the eligibility criteria for the study. Right ventricular end-diastolic and end-systolic volume, right ventricular end-diastolic diameter measurements on echocardiogram, and pulmonary artery pressures in both pre- and post-ASD groups were significantly higher than in controls. Tricuspid annular plane systolic excursion and isovolumic myocardial acceleration measurements significantly increased after the percutaneous closure of the defect; however, post-ASD measurements were still significantly lower than the controls.

Conclusions

Atrial septal defect device closure resulted in a significant increase of isovolumic myocardial acceleration measurements. Tissue Doppler analysis of regional myocardial function offers new insight into myocardial compensatory mechanisms for acute and chronic volume overload of both ventricles.

Effect of bosentan therapy on ventricular and atrial function in adults with Eisenmenger syndrome. A prospective, multicenter study using conventional and Speckle tracking echocardiography

BACKGROUND

The effect of bosentan on the ventricular and atrial performance in patients with Eisenmenger syndrome is unclear. In adult patients with Eisenmenger syndrome, we aimed to evaluate the midterm effect of bosentan on physical exercise, ventricular and atrial function, and pulmonary hemodynamics.

METHODS

Forty adult patients before and after 24 weeks bosentan therapy underwent 6 min walk test, two-dimensional speckle tracking echocardiography, plasma NT-proBNP measurement and cardiac catheterization.

RESULTS

After 24 weeks, bosentan therapy an improvement was observed regarding the 6 min walk distance from a median (quartile 1-quartile 3) of 382.5 (312-430) to 450 (390-510) m (p = 0.0001), NT-proBNP from 527.5 (201-1,691.25) to 369 (179-1,246) pg/ml (p = 0.021), right ventricular mean longitudinal systolic strain from 18 (13-22) to 19 (14.5-25) % (p = 0.004), left ventricular mean longitudinal systolic strain from 16 (12-21) to 17 (16-22) % (p = 0.001), right atrial mean peak longitudinal strain from 26 (18-34) to 28 (22-34) % (p = 0.01) and right atrial mean peak contraction strain from 11 (8-16) to 13 (11-16) % (p = 0.005). The invasively obtained Qp:Qs and Rp:Rs did not significantly change under bosentan therapy.

CONCLUSIONS

In adult patients with Eisenmenger syndrome, bosentan therapy improves ventricular and atrial functions resulting in enhancement of physical exercise and reduction in the NT-proBNP level, while the pulmonary vascular resistance does not change substantially.

A cornerstone of heart failure treatment is not effective in experimental right ventricular failure

BACKGROUND

Right ventricular (RV) failure due to increased pressure load causes significant morbidity and mortality in patients with congenital heart diseases and pulmonary arterial hypertension. It is unknown whether renin-angiotensin-aldosterone-system (RAAS) inhibition (the cornerstone of left ventricular failure treatment) is effective in RV failure. We investigated the effects of combination treatment of aldosterone-blocker eplerenone+angiotensin II receptor blocker losartan (Ep/Lo) on RV remodeling and function in a model of RV failure due to increased pressure load.

METHODS AND RESULTS

Rats (n=48) were randomized for pulmonary artery banding (PAB) or sham surgery and for losartan (20 mg/kg/d)+eplerenone (100 mg/kg/d) treatment (Ep/Lo) or vehicle (VEH). RV function was assessed by echocardiography and pressure-volume analysis at 5 and 11 weeks, or at the occurrence of clinical RV failure symptoms necessitating termination. PAB resulted in RV failure in all rats, as defined by reduced cardiac output, RV stroke volume, increased RV end diastolic pressure and liver congestion as well as RV fibrosis, hypertrophy and reduced capillary density. Clinical RV failure necessitated termination in 5/12 PAB-VEH rats. Angiotensin II type 1-receptor expression in the RV was reduced in PAB rats indicating local RAAS activation. Treatment of PAB rats with Ep/Lo significantly lowered arterial pressures, but had no significant effect on RV function, remodeling or survival compared to PAB-VEH rats.

CONCLUSIONS

RAAS inhibition does not beneficially affect experimental RV failure due to chronic pressure load. This is of high clinical relevance, because it indicates that the RV response to RAAS inhibition might fundamentally differ from that of the LV.

Distinct loading conditions reveal various patterns of right ventricular adaptation

Right ventricular (RV) failure due to chronically abnormal loading is a main determinant of outcome in pulmonary hypertension (PH) and congenital heart disease. However, distinct types of RV loading have been associated with different outcomes. To determine whether the adaptive RV response depends on loading type, we compared hemodynamics, exercise, and hypertrophy in models of pressure overload due to pulmonary artery banding (PAB), pressure overload due to PH, combined pressure and volume overload, and isolated volume load. Ninety-four rats were subjected to either PAB, monocrotaline-induced PH (PH), aortocaval shunt (shunt), or combined monocrotaline and aortocaval shunt (PH + shunt). We performed pressure-volume analysis and voluntary exercise measurements at 4 wk. We compared PAB to PH (part I) and PH + shunt to either isolated PH or shunt (part II). In part I, enhanced contractility (end-systolic elastance and preload recruitable stroke work) was present in PH and PAB, but strongest in PAB. Frank-Starling mechanism was active in both PAB and PH. In PAB this was accompanied by diastolic dysfunction (increased end-diastolic elastance, relaxation constant), clinical signs of RV failure, and reduced exercise. These distinct responses were not attributable to differences in hypertrophy. In part II, in PH + shunt the contractility response was blunted compared with PH, which caused pseudonormalization of parameters. Additional volume overload strongly enhanced hypertrophy in PH. We conclude that different types of loading result in distinct patterns of RV adaptation. This is of importance for the approach to patients with chronically increased RV load and for experimental studies in various types of RV failure.

Right ventricular inefficiency in repaired tetralogy of Fallot: proof of concept for energy calculations from cardiac MRI data

Repaired tetralogy of Fallot (rTOF) patients develop right ventricular (RV) dilatation and dysfunction. To prevent their demise, pulmonary valve replacement is necessary, though appropriate timing for it is challenged by a paucity of reliable diagnostic parameters. In this pilot study, we hypothesized that stroke work (SW) and energy calculations would delineate the inefficiency of RV performance in rTOF. RV SW was calculated for both an rTOF and a normal subject by utilizing RV pressure and volume measurements obtained during cardiac catheterization and MRI studies. Energy transfer rate and ratio were computed at the main pulmonary artery (PA). Compared to the normal RV, the rTOF RV had higher operating pressure, lower computed SW (0.078 J vs. 0.115 J for normal), and higher negative energy transfer at the PA (0.044 J vs. 0.002 J for normal). Furthermore, the energy transfer ratio was nearly twice as high for the normal RV (1.06) as for the rTOF RV (0.56). RV SW and energy transfer ratio delineate important operational efficiency differences in blood flow from the RV to the PA between rTOF and normal subjects. Our pilot data suggest that the rTOF RV is significantly less efficient than normal.

Assessment of left ventricular dyssynchrony and function using real-time 3-dimensional echocardiography in patients with congenital right heart disease

BACKGROUND

Patients after repair of congenital right heart disease (CRHD) may exhibit left ventricular (LV) dyssynchrony (LVD). However, the diagnosis of LVD is difficult and its reliability limited because current methods do not assess LVD of the whole LV simultaneously. The aim of the study was to assess LVD according to a novel global systolic dyssynchrony index (SDI) derived from real-time 3-dimensional echocardiography in patients after repaired CRHD.

METHODS

Two-dimensional echocardiography and real-time 3-dimensional echocardiography were performed in 30 patients after CRHD repair and in 30 matched healthy controls. Real-time 3-dimensional echocardiography data sets provided time-volume curves, and 2 global SDIs were derived from the dispersion of time to reach minimal systolic volume according to a 16- or 17-LV segment model.

RESULTS

Both SDIs were significantly elevated in the patient as compared with the control group (P < .001). A cutoff value for both SDIs was calculated and LVD defined as one of the SDIs exceeding cutoff. Left ventricular dyssynchrony was present in 5 (100%) of 5 patients with a LV ejection fraction (EF) <50% and 13 (52%) of 25 patients with preserved LVEF, thus being diagnosed in a total of 18 (60%) of 30 patients. Moreover, patients with LVD showed a significantly higher degree of pulmonary regurgitation (P = .01) with elevated right ventricular volumes and altered septal motion. Stepwise multivariate analysis identified LVEF (P = .005) and the degree of pulmonary regurgitation (P = .02) as independent predictors of LVD.

CONCLUSIONS

Left ventricular dyssynchrony can be detected in about 60% of patients after CRHD repair and is mainly due to significant pulmonary regurgitation resulting in an altered septal motion and systolic LV function.

Pulmonary valve implantation with the new Shelhigh Injectable Stented Pulmonic Valve

BACKGROUND

Pulmonary regurgitation (PR) occurs frequently after tetralogy of Fallot (TOF) repair, impairing long-term prognosis and necessitating reinterventions. Myocardial damage, invasiveness, and the risks of pulmonary valve replacement (PVR) therefore need to be minimized. The new Shelhigh Injectable Stented Pulmonic Valve (Shelhigh Inc, Union, NJ) allows implantation without cardiopulmonary bypass (CPB) under direct control.

METHODS

Twelve symptomatic patients (age, 21.3 +/- 12.5; range, 5.8 to 53.5 years) with severe PR and progressive right ventricular (RV) dilatation with dysfunction received the Shelhigh valve in sizes 21 (n = 1), 25 (n = 4), 27 (n = 3), 29 (n = 2), and 31 mm (n = 2).

RESULTS

Valve insertion was successful and hemodynamic performance excellent in all: peak systolic gradient, 14.5 +/- 4.6 (range, 10 to 20) mm Hg; mean gradient, 6.3 +/- 1.6 (range, 4 to 8) mm Hg. Four patients underwent concomitant procedures on CPB: one reduction plasty of a dilated main pulmonary artery, two tricuspid valve repairs, and one VSD closure. Early recovery was uneventful. There were no reoperations. During a mean follow-up of 5.4 +/- 4.3 months (range, 0.3 to 10.6 months) echocardiography showed good results, with low gradients and recovered RV function in all. All presented in New York Heart Association functional class 1 at the latest follow-up.

CONCLUSIONS

The Shelhigh valve allows easy PVR without CPB up to large valve sizes, with less invasiveness compared with a conventional approach. Further follow-up is needed to assess its durability and long-term performance.

Evaluation of postoperative pulmonary regurgitation after surgical repair of tetralogy of Fallot: comparison between Doppler echocardiography and MR velocity mapping

BACKGROUND

Pulmonary regurgitation is a common finding in patients after correction of tetralogy of Fallot (TOF). Right ventricular impairment and even ventricular arrhythmia have been ascribed to pulmonary valve insufficiency (PI), which is therefore an important issue in follow-up examinations.

OBJECTIVE

To compare PI measured by echocardiography (ECHO) with data provided by cardiac MRI (CMR).

MATERIALS AND METHODS

We studied 54 selected patients (18 female; median age 14.0 years, range 3.8-53.4 years) after surgical correction of TOF. To quantify pulmonary regurgitant fraction (PRF) by CMR, flow velocity mapping was performed. On Doppler ECHO, length, width and localization of regurgitant flow was measured. The severity of PI was categorized as mild, moderate or severe and compared to the data obtained by CMR.

RESULTS

On CMR the mean PRF was 29.2 +/- 13.4%. Patients with a transannular patch had a significantly higher PRF (39.9 +/- 11.6%) than patients with an intact annular ring (23.6 +/- 11.4%). Differentiation by Doppler ECHO between the categories mild, moderate and severe PI was confirmed by significant differences in PRF measured by CMR (mild vs. moderate P < 0.04; moderate vs. severe P < 0.014; mild vs. severe P < 0.001). Furthermore, PRF correlated with right ventricular end diastolic volume index (r = 0.45, P < 0.01) and right ventricular end systolic volume index (r = 0.39, P < 0.01).

CONCLUSION

Doppler ECHO can estimate the severity of PI after repair of TOF with acceptable results compared to CMR flow measurement. In univariate analysis there is only a weak influence of PRF on right ventricular volume.

Impaired Power Output and Cardiac Index With Hypoplastic Left Heart Syndrome: A Magnetic Resonance Imaging Study

BACKGROUND

Unfavorable cardiac mechanics in children with hypoplastic left heart syndrome (HLHS) when compared with other single-ventricle defects may affect long-term morbidity and outcome. Using noninvasive phase contrast magnetic resonance imaging (PC MRI), we examined cardiac mechanics in children with HLHS and compared the results to other single-ventricle defects.

METHODS

Eighteen children with HLHS and 18 children with other single-ventricle defects were studied after the Fontan operation. Phase contrast MRI scans were obtained perpendicular to the ascending aorta, and flow was quantified using an in-house segmentation and reconstruction scheme. The total power output was determined using the modified Bernoulli equation along with cardiac output and systemic vascular resistance index.

RESULTS

Compared with non-HLHS congenital heart defects, children with HLHS had significantly lower power output (1.40 +/- 0.39 versus 1.78 +/- 0.38 W/m2, p < 0.004) and cardiac index (3.15 +/- 0.97 versus 4.09 +/- 1.23 L x Min(-1) x m(-2), p < 0.009) with a concomitant higher systemic vascular resistance index (28.94 +/- 11.5 versus 22.7 +/- 8.53 WU, p < 0.03) despite generating similar systolic blood pressures (112.9 +/- 22.4 versus 115.2 +/- 23 mm Hg, p > 0.05).

CONCLUSIONS

Minimally invasive measurements with PC MRI in children with HLHS showed significantly lower power output and cardiac index when compared with other single-ventricle physiologies. Abnormal aortic flow patterns may contribute to power loss and may have long-term survival and morbidity implications associated with the Fontan procedure. Elevated systemic vascular resistance index despite similar blood pressure opens avenues for therapeutic intervention for afterload reduction.

Cardiac resynchronization therapy in congenital heart disease

While cardiac resynchronization therapy (CRT) is of proven benefit in selected patients with severe ischemic or dilated cardiomyopathy, refractory symptoms, and conduction delay, extrapolation to congenital heart disease is not straightforward. This rapidly expanding patient population commonly suffers from heart failure, particularly in the presence of a single or systemic right ventricle. Surgical repair may also contribute to ventricular asynchrony. In this systematic review, the current state of knowledge regarding CRT in congenital heart disease is presented. Issues specific to congenital heart disease including right bundle branch block, right (pulmonary) ventricular dysfunction, systemic right ventricular dysfunction, and single ventricle dysfunction are explored. Evidence-based CRT applications for each of these particular conditions are reviewed. Initial experience with CRT in the acute postoperative setting and longer-term, including our own, is elaborated. Unlike standard indications based on multiple randomized clinical trials, supporting evidence for CRT in congenital heart disease is limited to case reports, case series, and small experimental crossover studies in the acute postoperative setting. The heterogeneous patient population, technical limitations from patient size, vascular access issues, and unique forms of ventricular asynchrony further obscure the selection of potential beneficiaries. Despite these limitations, experience thus far has been favorable. Quality of current data precludes definitive evidence-based recommendations, but optimistic initial results suggest that research endeavors in this field should be pursued. Multicenter prospective collaborative efforts are to be encouraged.

Pregnancy Outcomes in Women With Congenital Heart Disease

Background— Pregnant women with congenital heart disease are at increased risk for cardiac and neonatal complications, yet risk factors for adverse outcomes are not fully defined.

Methods and Results— Between January 1998 and September 2004, 90 pregnancies at age 27.7±6.1 years were followed in 53 women with congenital heart disease. Spontaneous abortions occurred in 11 pregnancies at 10.8±3.7 weeks, and 7 underwent elective pregnancy termination. There were no maternal deaths. Primary maternal cardiac events complicated 19.4% of ongoing pregnancies, with pulmonary edema in 16.7% and sustained arrhythmias in 2.8%. Univariate risk factors included prior history of heart failure (odds ratio [OR], 15.5), NYHA functional class ≥2 (OR, 5.4), and decreased subpulmonary ventricular ejection fraction (OR, 7.7). Independent predictors were decreased subpulmonary ventricular ejection fraction and/or severe pulmonary regurgitation (OR, 9.0) and smoking history (OR, 27.2). Adverse neonatal outcomes occurred in 27.8% of ongoing pregnancies and included preterm delivery (20.8%), small for gestational age (8.3%), respiratory distress syndrome (8.3%), intraventricular hemorrhage (1.4%), intrauterine fetal demise (2.8%), and neonatal death (1.4%). A subaortic ventricular outflow tract gradient >30 mm Hg independently predicted an adverse neonatal outcome (OR, 7.5). Cardiac risk assessment was improved by including decreased subpulmonary ventricular systolic function and/or severe pulmonary regurgitation (OR, 10.3) in a previously proposed risk index developed in pregnant women with acquired and congenital heart disease.

Conclusions— Maternal cardiac and neonatal complication rates are considerable in pregnant women with congenital heart disease. Patients with impaired subpulmonary ventricular systolic function and/or severe pulmonary regurgitation are at increased risk for adverse cardiac outcomes.

Effects of acute preload reduction on myocardial velocity during isovolumic contraction and myocardial acceleration in pediatric patients

We evaluated the effects of acute preload reduction with inferior vena cava (IVC) occlusion on myocardial velocities during systole (Sa), early (Ea) and late (Aa) diastole, isovolumic contraction (IVV), and myocardial acceleration (IVA) measured by tissue Doppler imaging (TDI) in pediatric patients. A total of 22 patients (5 +/- 3 years) were studied: 9 patients (4 +/- 3 years) with Kawasaki disease, 8 patients (6 +/- 3 years) with atrial septal defect and right ventricular (RV) volume overload, and 5 patients (5 +/- 4 years) with pulmonary stenosis and RV pressure overload. Using TDI, Sa, Ea, Aa, IVV were recorded at the base of the RV free wall from a four-chamber view. IVA was calculated by dividing IVV by the time interval from onset of IVV to the time at peak velocity of this wave. In each group, IVC occlusion caused significant decreases in peak Sa, peak Ea, and peak Aa (p < 0.05). However, IVV and IVA did not change during acute preload reduction. This study demonstrated the effects of acute preload reduction on TDI velocities. In contrast to peak Sa, peak Ea, and peak Aa, IVV and IVA were unaffected by preload within a physiological range.

Quantitative assessment of right ventricular geometric remodeling in pulmonary hypertension secondary to left-sided heart disease using real-time three-dimensional echocardiography

We assessed right ventricular (RV) geometric remodeling quantitatively in patients with chronic pulmonary hypertension (PH) secondary to left-sided heart disease using real-time 3-dimensional echocardiography by comparing segmental and total volumes to that in normal subjects. The comparison result revealed that RV geometric remodeling in the PH group mainly occurred at the basal, mid-basal, and mid-segments. Total RV end-diastolic and end-systolic volumes in the PH group were significantly larger than that in normal subjects.

Regional and global right ventricular dysfunction in asymptomatic or minimally symptomatic patients with congenitally corrected transposition

Patients with congenitally corrected transposition are at risk of right ventricular dysfunction and failure. With this in mind, we examined 13 patients with congenitally corrected transposition, 7 not having undergone surgery, and 6 after physiological repair, comparing them with 6 healthy subjects matched for age and sex, using cardiac magnetic resonance imaging, at rest and during dobutamine stress, in order to determine regional and global right ventricular response to stress. At rest, the patients had significantly decreased overall wall motion compared to their healthy peers (7.2 +/- 0.5, versus 9.8 +/- 0.4 mm). During infusion of dobutamine, overall wall motion increased to 12.8 +/- 0.4 mm in the healthy subjects, versus 8.8 +/- 1.0 mm in patients. At the regional level, significant differences in mural motion were found between patients and controls in the anterior (9.5 +/- 1.1, versus 13.2 +/- 0.6 mm), posterior (10.2 +/- 1.6, versus 13.2 +/- 0.8 mm), and septal segments (5.0 +/- 0.8, versus 11.2 +/- 0.6 mm). At rest, overall mural thickening in patients was similar to that of controls, but significantly less in patients during stress. During dobutamine stress, patients showed significantly less regional wall thickening than controls, particularly in the septal (2.7 +/- 0.6, versus 6.0 +/- 0.4 mm, respectively) and in the anterior segments (4.2 +/- 0.6, versus 7.8 +/- 0.6 mm, respectively). Right ventricular ejection fraction strongly correlated with mural motion and thickening, both at rest and during stress. Abnormal regional function in the systemic morphologically right ventricle may occur in patients with congenitally corrected transposition, which strongly correlates with right ventricular ejection fraction. Our findings support the hypothesis that, in patients with congenitally corrected transposition, ischemia of the right ventricular myocardium contributes to the development of right ventricular dysfunction.

Endovascular stents in pulmonary valve and artery in swine: feasibility study of MR imaging-guided deployment and postinterventional assessment

PURPOSE

To assess the feasibility of using magnetic resonance (MR) imaging to guide stent deployment in the pulmonary valve and artery and evaluate, after stent deployment, the position and morphology of and blood flow through the stent.

MATERIALS AND METHODS

Angiography and 1.5-T MR imaging were performed in a dual-imaging suite. Nitinol stents were placed in the pulmonary valve and main pulmonary artery in five pigs by using MR imaging guidance. For interactive MR imaging monitoring of catheter manipulation and stent delivery, balanced fast field-echo and T1-weighted turbo field-echo sequences were used. Visualization of the delivery system was based on T2* (with air as the contrast material) or T1 (with gadodiamide as the contrast material). After stent deployment, the position and morphology of and flow through the stent were verified with multiphase multisection balanced fast field-echo and velocity-encoded cine MR imaging. Findings at angiography and postmortem examination also helped verify stent placement. The paired Student t test was used for data analysis.

RESULTS

The stent was successfully deployed in all animals. The stent was placed distal to the pulmonary valve in four animals and across the pulmonary valve in one animal. The position and morphology of the stent were clearly depicted on balanced fast field-echo images. In the animal with the stent placed across the pulmonary valve, the pulmonary regurgitant fraction was 37%; this was not seen in the animals with stents placed distal to the pulmonary valve. No complication (eg, stent migration, intramural injury, or vascular perforation) was noted during the intervention. Findings at angiography and postmortem examination confirmed the position of the stents.

CONCLUSION

MR imaging has the potential to guide stent placement in the pulmonary valve or artery and to evaluate flow volume within the stent lumen after the intervention.

Detection of early right ventricular dysfunction in Chagas' disease using Doppler tissue imaging

BACKGROUND

The involvement of the right ventricle (RV) in Chagas' disease is frequent. Although echocardiography plays an important role in noninvasive assessment of cardiac function, evaluation of RV is challenging because of the anatomic and functional complexity of this chamber.

METHODS

To study early functional abnormalities in the RV, we selected 18 patients with Chagas' disease, no other disease, and a normal echocardiogram; and 12 normal individuals as a control group. All participants were submitted to Doppler tissue imaging and the parameters of systolic (systolic wave and regional isovolumic contraction time) and diastolic (early and late expansion waves) function were analyzed at the level of the interventricular septum and free wall of the RV.

RESULTS

Regional isovolumic contraction time values showed a statistically significant difference between the 2 groups both in the RV free (P =.0003) and septal (P =.003) walls. With respect to diastolic function, we observed a significant difference between groups involving the early expansion wave (P =.014) and e/a ratio (P =.004) of the RV free wall.

CONCLUSION

Doppler tissue imaging proved to be useful in early detection of RV dysfunction in Chagas' disease, with potential use in risk stratification of these patients.

Right ventricular function

This article describes the importance of the right ventricle in both the normal circulation, and in the abnormal milieu of previously palliated or corrected congenital heart disease. The latter group represents natural models of abnormal right ventricular loading that do not exist in any other experimental arena, and their study has provided insights into chronic adaptation of the right ventricle, in terms of cardiopulmonary haemodynamics, right-left heart interactions and mechano-electric inter-relationships.

Validation of myocardial acceleration during isovolumic contraction as a novel noninvasive index of right ventricular contractility: comparison with ventricular pressure-volume relations in an animal model

BACKGROUND

We have demonstrated that myocardial acceleration during isovolumic contraction (IVA) is a sensitive index of left ventricular contractile function. In this study, we assessed the utility of IVA to measure right ventricular (RV) contractile function.

METHODS AND RESULTS

We examined 8 pigs by using tissue Doppler imaging of the RV free wall and simultaneous measurements of intraventricular pressure, volume, maximal elastance (e(max)), preload recruitable stroke work, and dP/dt(max) by conductance catheterization. Animals were paced in the right atrium at a rate of 130 beats per minute (bpm). IVA was compared with elastance during contractility modulation by esmolol and dobutamine and during preload reduction and afterload increase by transient balloon occlusion of the inferior vena cava and pulmonary artery, respectively. Data were also obtained during incremental atrial pacing from 110 to 210 bpm. Esmolol led to a decrease in IVA and dP/dt(max). During dobutamine infusion, IVA, dP/dt(max), preload recruitable stroke work, and e(max) all increased significantly. During preload reduction and afterload increase, IVA remained constant up to a reduction of RV volume by 54% and an RV systolic pressure increase of 58%. Pacing up to a rate of 190 bpm led to a stepwise increase in IVA and dP/dt(max), with a subsequent fall at a pacing rate of 210 bpm.

CONCLUSIONS

IVA is a measurement of RV contractile function that is unaffected by preload and afterload changes in a physiological range and is able to measure the force-frequency relation. This novel index may be ideally suited to the assessment of acute changes of RV function in clinical studies.

Relation between right ventricular enlargement, QRS duration, and right ventricular function in patients with tetralogy of Fallot and pulmonary regurgitation after surgical repair

OBJECTIVE

In patients with repaired tetralogy of Fallot, to examine (1) a possible relation between right ventricular enlargement and QRS prolongation, and (2) the effect of right ventricular enlargement caused by pulmonary regurgitation on the right ventricular ejection fraction, evaluated by three dimensional echocardiography, and global function, evaluated by the myocardial performance index.

DESIGN AND PATIENTS

40 patients with repaired tetralogy were studied. Right ventricular volumes were derived from three dimensional echocardiographic data after this method had been validated by comparison with magnetic resonance imaging in 21 patients. Ejection fraction was calculated from end diastolic and end systolic volumes. The Doppler derived myocardial performance index was measured in all patients. Measured data were correlated with QRS duration.

SETTING

Tertiary cardiac centre for congenital heart disease.

RESULTS

There was good agreement between three dimensional echocardiographic and magnetic resonance assessment of right ventricular volumes and ejection fraction. The z score of the right ventricular end diastolic volume and ejection fraction of all patients was 1.35 and -4.15, respectively. Patients with severe pulmonary regurgitation had a lower right ventricular ejection fraction (p < 0.01) and an increased myocardial performance index (p < 0.01) compared with patients with mild to moderate pulmonary regurgitation. The correlation between ejection fraction and right ventricular end diastolic volume was r = -0.35 (p < 0.05). The mean (SD) QRS duration was 131.89 (25.69) ms, range 80-180 ms. The correlation between QRS duration and right ventricular end diastolic volume was r = 0.6 (p < 0.01).

CONCLUSIONS

There is a correlation between the right ventricular size obtained by three dimensional echocardiography and QRS duration on the surface ECG, indicating mechanoelectrical interaction. The severity of pulmonary regurgitation has a negative influence on right ventricular ejection fraction and combined systolic and diastolic global function, as assessed by myocardial performance.

Double-chambered right ventricle presenting in adulthood

BACKGROUND

Double-chambered right ventricle is a form of right ventricular outflow tract obstruction that develops over time, often in patients with an abnormally short distance between the moderator band and pulmonary valve. This lesion typically presents in childhood or adolescence and is often accompanied by a ventricular septal defect. Only a handful of previous cases have been described in which double-chambered right ventricle occurred in adulthood.

METHODS

Since 1992, three patients more than 30 years old (38, 43, and 66 years of age) have presented at our institution with unusual symptoms or a previous incorrect diagnosis. We reviewed the clinical data in these patients.

RESULTS

Presenting symptoms included syncope, angina, and severe dyspnea resembling pulmonary hypertension. In 1 patient, disease was categorized as New York Heart Association class IV, and in the other 2 as class III. Coexisting anomalies included a patent foramen ovale or secundum atrial septal defect in 2 patients, a small ventricular septal defect in 1 (with a probable history of ventricular septal defect in another), and mild aortic regurgitation in 1. All patients required urgent or emergent operations, with peak pressures in the proximal right ventricular chamber of 135 to 180 mm Hg and severely depressed left ventricular function in 1 patient. Resection of the anomalous right ventricular muscle bundles was achieved through a right atrial approach in all patients. All patients were alive with improved functional status at follow-up, which was between 15 and 40 months.

CONCLUSIONS

Right ventricular outflow tract obstruction resulting from a double-chambered right ventricle is rare in adults, but when it does occur it can present with unusual symptoms. When evaluating the patient with signs or symptoms of primary right heart failure, cardiologists should make an effort to image the entire right heart complex. Subcostal echocardiography can facilitate adequate visualization of the right ventricle when it is difficult to distinguish the subpulmonary outflow tract from the parasternal and apical windows.

Right ventricular volumes and ejection fraction with fast cine MR imaging in breath-hold technique: applicability, normal values from 52 volunteers, and evaluation of 325 adult cardiac patients

Our goal was to establish right ventricular (RV) volume and ejection fraction (EF) values in normal volunteers with fast magnetic resonance (MR) imaging using a breath-hold technique, to assess the frequency and severity of RVEF abnormality in cardiac patients and to compare RV with left ventricular (LV) data. We performed simultaneously derived RV and LV fast cine measurements in 52 normals and 325 patients with coronary artery disease (CAD), acquired valvular disease (VD), cardiomyopathy (CM), or congenital heart disease (CHD). RVEF was reduced in 31% (102) of all patients, in 50% dilated CM, 39% CHD, 34% CAD, and 22% acquired VD patients. Solitary abnormally low RVEF was found in only 15/325 (5%) of all patients, whereas combined with LVEF deterioration in 87/172 (51%) patients. RVEF reduction was mild in 64%, moderate in 25%, and severe in 11%. Although RVEF correlated significantly (r = 0.55, P < 0.001) with LVEF, the predictive value of LVEF for RVEF was low. We conclude that RV volumes can be routinely assessed with fast MRI and should be performed in addition to LV evaluation in CHD, in right-sided VD, and in all patients with an abnormal LVEF.J. Magn. Reson. Imaging 1999; 10:908-918.

Pediatric echocardiography: applications and limitations

Echocardiography is an extraordinarily useful imaging technique in fetuses, infants, children, and adolescents. Recent technologic innovations have expanded its versatility in the pediatric population. However, limited societal resources, limitations inherent to ultrasound imaging, and numerous imaging options even within the field of pediatric echocardiography necessitate the discriminate and thoughtful use of echocardiography in children. The clinical assessment remains a critical prelude to echocardiographic examination of the pediatric cardiovascular system.