Contribution of each ventricular wall to ventricular interdependence

Dynamic load modulation predicts right heart tolerance of left ventricular cardiovascular assist in a porcine model of cardiogenic shock

Ventricular assist devices (VADs) offer mechanical support for patients with cardiogenic shock by unloading the impaired ventricle and increasing cardiac outflow and subsequent tissue perfusion. Their ability to adjust ventricular assistance allows for rapid and safe dynamic changes in cardiac load, which can be used with direct measures of chamber pressures to quantify cardiac pathophysiologic state, predict response to interventions, and unmask vulnerabilities such as limitations of left-sided support efficacy due to intolerance of the right heart. We defined hemodynamic metrics in five pigs with dynamic peripheral transvalvular VAD (pVAD) support to the left ventricle. Metrics were obtained across a spectrum of disease states, including left ventricular ischemia induced by titrated microembolization of a coronary artery and right ventricular strain induced by titrated microembolization of the pulmonary arteries. A sweep of different pVAD speeds confirmed mechanisms of right heart decompensation after left-sided support and revealed intolerance. In contrast to the systemic circulation, pulmonary vascular compliance dominated in the right heart and defined the ability of the right heart to adapt to left-sided pVAD unloading. We developed a clinically accessible metric to measure pulmonary vascular compliance at different pVAD speeds that could predict right heart efficiency and tolerance to left-sided pVAD support. Findings in swine were validated with retrospective hemodynamic data from eight patients on pVAD support. This methodology and metric could be used to track right heart tolerance, predict decompensation before right heart failure, and guide titration of device speed and the need for biventricular support.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the use of cardiovascular magnetic resonance in pediatric congenital and acquired heart disease : Endorsed by The American Heart Association

Cardiovascular magnetic resonance (CMR) has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of CMR in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of CMR in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the Use of Cardiac Magnetic Resonance in Pediatric Congenital and Acquired Heart Disease: Endorsed by The American Heart Association

Cardiovascular magnetic resonance has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of cardiovascular magnetic resonance in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of cardiovascular magnetic resonance in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

The Degree of Left Ventricular Hypoplasia Is Associated with Tricuspid Regurgitation Severity in Infants with Hypoplastic Left Heart Syndrome

Tricuspid valve regurgitation (TR) increases adverse outcomes in children with hypoplastic left heart syndrome (HLHS). Changes in tricuspid valve (TV) annulus and leaflet geometry have been described but the underlying causes for TR in HLHS remain uncertain. We aimed to examine the association between left ventricular (LV) size and TR in infants with HLHS as right ventricular (RV)-LV interactions may be important in TR development. Echocardiograms of 50 infants with HLHS were reviewed. LV size, RV function, TR grade, TV annulus z-score, and aortic arch obstruction were examined at birth and 1 year of age (or the latest study post-bidirectional Glenn anastomosis if the patient was < 1 year of age). 24/50 (48%) had severe LV hypoplasia and 26/50 (52%) had mild/moderate LV hypoplasia. At 1 year, 10/24 (42%) with severe LV hypoplasia had moderate/severe TR versus 0/26 in the mild/moderate LV hypoplasia group (p = 0.0002). TR progressed ( ≥ 1 grade) in 14/24(58%) with severe LV hypoplasia versus 5/26 (19%) with mild/moderate LV hypoplasia (p = 0.008). In this cohort, no association was found between the degree of TR and either RV function, TV annular z-score, or arch obstruction; or between the degree of LV hypoplasia and either RV function or TV annular z-score. In infants with HLHS, the severity and progression of TR is associated with the severity of LV hypoplasia. The mechanism for this association needs further exploration but suggests a role for RV-LV interactions in the development of TR.

Comparison of the effects of candesartan cilexetil and enalapril maleate on right ventricular myocardial remodeling in dogs with experimentally induced pulmonary stenosis

OBJECTIVE

To compare the effects of candesartan cilexetil and enalapril maleate on right ventricular myocardial remodeling in dogs with experimentally induced pulmonary stenosis.

ANIMALS

24 Beagles.

PROCEDURES

18 dogs underwent pulmonary arterial banding (PAB) to induce right ventricular pressure overload, and 6 healthy dogs underwent sham operations (thoracotomy only [sham-operated group]). Dogs that underwent PAB were allocated to receive 1 of 3 treatments (6 dogs/group): candesartan (1 mg/kg, PO, q 24 h [PABC group]), enalapril (0.5 mg/kg, PO, q 24 h [PABE group]), or no treatment (PABNT group). Administration of treatments was commenced the day prior to surgery; control dogs received no cardiac medications. Sixty days after surgery, right ventricular wall thickness was assessed echocardiographically and plasma renin activity, angiotensin-converting enzyme activity, and angiotensin I and II concentrations were assessed; all dogs were euthanatized, and collagenous fiber area, cardiomyocyte diameter, and tissue angiotensin-converting enzyme and chymase-like activities in the right ventricle were evaluated.

RESULTS

After 60 days of treatment, right ventricular wall thickness, cardiomyocyte diameter, and collagenous fiber area in the PABNT and PABE groups were significantly increased, compared with values in the PABC and sham-operated groups. Chymase-like activity was markedly greater in the PABE group than in other groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that treatment with candesartan but not enalapril effectively prevented myocardial remodeling in dogs with experimentally induced subacute right ventricular pressure overload.

Different prognostic significance of right and left ventricular diastolic dysfunction in heart failure

BACKGROUND

Left (LV) and right (RV) ventricular diastolic dysfunction is common in heart failure but the prognostic value of RV diastolic dysfunction is not known.

HYPOTHESIS

As a follow-up to a previously undertaken study, this study was carried out to investigate whether LV and RV diastolic dysfunction affect prognosis differently and, in addition, whether changes in diastolic filling patterns over time correlate with clinical outcome.

METHODS

We studied a cohort of 105 patients (mean age 62.7 +/- 1.3 years, 66% male) with heart failure (ejection fraction < 50%) by Doppler echocardiography in both RV and LV.

RESULTS

An LV restrictive filling pattern (RFP) was present in 48% of the patients and, when compared with non-RFP subgroups, it was associated with poorer systolic function, higher New York Heart Association functional class, and higher cardiac mortality at 1 year (all p < 0.001). The coexistence of an LV-RFP and poor LV systolic function (ejection fraction < 25%) markedly decreased the 1-year survival that was significant when compared with other subgroups (p = 0.001). In contrast, RV diastolic dysfunction that occurred in 21% of patients was not a prognostic factor for mortality either alone or in combination with LV diastolic dysfunction, but predicted nonfatal hospital admissions for heart failure or unstable angina (p = 0.016).

CONCLUSION

An LV restrictive filling pattern is a powerful predictor of a poor prognosis, especially when combined with low ejection fraction, but in this study RV diastolic dysfunction did not appear to be an independent predictor of subsequent mortality.

New aspects of the ventricular septum and its function: an echocardiographic study

OBJECTIVES

To examine whether the line dividing the septum into two layers is found consistently by conventional echocardiography and to evaluate functional differences in the right and left side of the septum in terms of wall thickening, strain rate, and strain imaging.

DESIGN

In a systematic study in 30 normal subjects, M mode and Doppler myocardial imaging data from the interventricular septum (IVS) were recorded. Velocity curves, regional strain rate, and strain profiles were obtained. Systolic deformation (wall thickening, radial and longitudinal strain rate, and strain) of both sides were assessed. Furthermore, three patients with one sided abnormalities were studied.

RESULTS

A bright echo consistently segmented the IVS into a left and right part. In this normal population radial deformation was different for the left and right side of the septum (mean (SD) wall thickening on the left, 49 (46)%, and on the right, 17 (38)%; strain rate on the left, 3.8 (0.6) 1/s, and on the right, 2.1 (1.9) 1/s; strain on the left, 41 (17)%, and on the right, 22 (14)%), whereas longitudinal deformation was found to be similar (strain rate on the left, -2.2 (0.7) 1/s, and on the right, -2.0 (0.6) 1/s; strain on the left, -28 (12)%, and on the right, -25 (12)%). The presented clinical examples show that abnormalities can be strictly limited to one layer.

CONCLUSIONS

Differential radial deformation and knowledge of fibre architecture showing an abrupt change in the middle of the septum, together with the clinical cases, suggest the septum to be a morphologically and functionally bilayered structure potentially supplied by different coronary arteries.

Time course of right ventricular remodeling in rats with experimental myocardial infarction

Right ventricular (RV) weight increases dependent on time after myocardial infarction (MI) and on MI size. The sequential changes in RV volume and hemodynamics and their relations to left ventricular (LV) remodeling after MI are unknown. We therefore examined the time course of RV remodeling in rats with LV MI. MI was produced by left coronary artery ligation. Four, eight, and sixteen weeks later, LV and RV hemodynamic measurements were performed and pressure-volume curves were obtained. For serial measurement of RV volumes and performance, cine-MRI was performed 2 and 8 wk after MI. The ratios of beta-myosin heavy chain (MHC) to alpha-MHC and skeletal to cardiac alpha-actin were determined for the RV and LV after large MI or sham operation. RV weight increased in rats with MI, as did RV volume. RV pressure-volume curves were shifted toward larger volumes 16 wk after large MI. RV systolic pressure increased gradually over time; however, the gain in RV weight was always in excess of RV systolic pressure. The ratios of skeletal to cardiac alpha-actin and beta-MHC to alpha-MHC were increased after MI in both ventricles in a similar fashion. Because RV wall stress was not increased after infarction, mechanical factors may not conclusively explain hypertrophy, which maintained balanced loading conditions for the RV even after large LV infarction.

Cardiac MR imaging in congenital heart disease

Magnetic resonance imaging is a unique and insightful tool for the assessment of structure and function in congenital heart disease. For anatomic assessment, the large field of view, lack of limitation by patient size, and ability to create three-dimensional surface displays from routine imaging acquisitions offer several advantages over other modalities. The ability of magnetic resonance imaging to assess the volume and mass of bizarre ventricular shapes accurately and myocardial tissue and blood tagging as well as phase encoded velocity mapping has enhanced research in pediatric cardiology. Newer techniques, such as oxygen-sensitive magnetic resonance imaging and echo-planar magnetic resonance imaging, promise even further advances in research and in clinical applications.

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

The right ventricle is often subject to both pressure and volume overload in congenital heart disease. Evaluating right ventricular function in both the native lesion and after surgery in light of these loading conditions, presents a unique challenge for investigators studying these misshapen hearts. The purpose of this article is to briefly delineate what is generally known about right ventricular function in congenital heart disease and to touch on some noninvasive imaging modalities which have helped shed some light on this matter.

A study in ventricular-ventricular interaction. Single right ventricles compared with systemic right ventricles in a dual-chamber circulation

BACKGROUND

Ventricular-ventricular interaction is known to occur in normal human heart. To determine whether it plays a role in the function of single right ventricles, systemic right ventricles were compared with and without a left ventricle mechanically coupled to it.

METHODS AND RESULTS

A noninvasive magnetic resonance tagging technique (spatial modulation of magnetization [SPAMM]) that lays intersecting stripes down on the myocardium was used to examine 18 patients with systemic right ventricles: 7 with a single right ventricle who have undergone the Fontan procedure (age, 38.8 +/- 8.9 months) and 11 with transposition of the great arteries who have undergone an atrial inversion operation (age, 16.3 +/- 3.9 years). The motion of the intersection points was tracked through systole to determine regional twist and radial shortening. Shortening rates also were evaluated. Finite strain analysis was applied to the grid lines using Delaunay triangulation, and the two-dimensional strain tensor and principal E1 strains were derived for the various anatomic regions. Basal and apical short-axis planes through the ventricular wall were categorized into four distinct regions spaced equally around the circumference of the slice. We observed the following results. (1) Strain was greatest and heterogeneity of strain was least in patients with transposition of the great arteries who were status post atrial inversion operation (six of eight regions). Marked differences were noted in the distribution of strain within a given region, from endocardium to epicardium, and from atrioventricular valve to apical plane between patient subtypes and those with a normal left ventricle. (2) Contrary to the normal subject studied by the use of the same method, for both patient subtypes, there was counterclockwise twist in one region, clockwise twist in the posterior or inferior wall, and a transition zone of no twist at which the two regions of twist met. Normal human adult left ventricles studied in short-axis twist uniformly counterclockwise as viewed from apex to base. (3) Radial inward motion was greatest in the superior wall of both types of systemic right ventricle. The inferior walls of Fontan patients and the posterior (ie, septal) walls of patients with transposition of the great arteries, status post atrial inversion, moved paradoxically in systole. The shortening rate at the atrioventricular valve of patients with transposition of the great arteries, status post atrial inversion, was significantly lower than at the apex or in Fontan patients.

CONCLUSIONS

Marked differences in regional wall motion and strain were demonstrated in systemic right ventricles, depending on whether a left ventricle was present to augment its function. Ventricular-ventricular interaction appears to play an important role in affecting the biomechanics of systemic right ventricles. These observations were markedly different from those in the normal systemic left ventricle. These techniques demonstrate tools with which we can begin to evaluate surgical outcomes using regional myocardial mechanics and may provide a clue to single right ventricle failure.