Role of kinetic energy in pulmonary valvar pressure gradients

Blood flow kinetic energy is a novel marker for right ventricular global systolic function in patients with left ventricular assist device therapy

Objectives

Right ventricular (RV) failure remains a major concern in heart failure (HF) patients undergoing left ventricular assist device (LVAD) implantation. We aimed to measure the kinetic energy of blood in the RV outflow tract (KE-RVOT) - a new marker of RV global systolic function. We also aimed to assess the relationship of KE-RVOT to other echocardiographic parameters in all subjects and assess the relationship of KE-RVOT to hemodynamic parameters of RV performance in HF patients.

Methods

Fifty-one subjects were prospectively enrolled into 4 groups (healthy controls, NYHA Class II, NYHA Class IV, LVAD patients) as follows: 11 healthy controls, 32 HF patients (8 NYHA Class II and 24 Class IV), and 8 patients with preexisting LVADs. The 24 Class IV HF patients included 21 pre-LVAD and 3 pre-transplant patients. Echocardiographic parameters of RV function (TAPSE, St', Et', IVA, MPI) and RV outflow color-Doppler images were recorded in all patients. Invasive hemodynamic parameters of RV function were collected in all Class IV HF patients. KE-RVOT was derived from color-Doppler imaging using a vector flow mapping proprietary software. Kruskal-Wallis test was performed for comparison of KE-RVOT in each group. Correlation between KE-RVOT and echocardiographic/hemodynamic parameters was assessed by linear regression analysis. Receiver operating characteristic curves for the ability of KE-RVOT to predict early phase RV failure were generated.

Results

KE-RVOT (median ± IQR) was higher in healthy controls (55.10 [39.70 to 76.43] mW/m) than in the Class II HF group (22.23 [15.41 to 35.58] mW/m, p < 0.005). KE-RVOT was further reduced in the Class IV HF group (9.02 [5.33 to 11.94] mW/m, p < 0.05). KE-RVOT was lower in the LVAD group (25.03 [9.88 to 38.98] mW/m) than the healthy controls group (p < 0.005). KE-RVOT had significant correlation with all echocardiographic parameters and no correlation with invasive hemodynamic parameters. RV failure occurred in 12 patients who underwent LVAD implantation in the Class IV HF group (1 patient was not eligible due to death immediately after the LVAD implantation). KE-RVOT cut-off value for prediction of RV failure was 9.15 mW/m (sensitivity: 0.67, specificity: 0.75, AUC: 0.66).

Conclusions

KE-RVOT, a novel noninvasive measure of RV function, strongly correlates with well-established echocardiographic markers of RV performance. KE-RVOT is the energy generated by RV wall contraction. Therefore, KE-RVOT may reflect global RV function. The utility of KE-RVOT in prediction of RV failure post LVAD implantation requires further study.

Disturbed left and right ventricular kinetic energy in patients with repaired tetralogy of Fallot: pathophysiological insights using 4D-flow MRI

OBJECTIVES

Indications for pulmonary valve replacement (PVR) in patients with pulmonary regurgitation (PR) after repaired tetralogy of Fallot (rToF) are debated. We aimed to compare right (RV) and left ventricular (LV) kinetic energy (KE) measured by 4D-flow magnetic resonance imaging (MRI) in patients to controls, to further understand the pathophysiological effects of PR.

METHODS

Fifteen patients with rToF with PR > 20% and 14 controls underwent MRI. Ventricular volumes and KE were quantified from cine MRI and 4D-flow, respectively. Lagrangian coherent structures were used to discriminate KE in the PR. Restrictive RV physiology was defined as end-diastolic forward flow.

RESULTS

LV systolic peak KE was lower in rToF, 2.8 ± 1.1 mJ, compared to healthy volunteers, 4.8 ± 1.1 mJ, p < 0.0001. RV diastolic peak KE was higher in rToF (7.7 ± 4.3 mJ vs 3.1 ± 1.3 mJ, p = 0.0001) and the difference most pronounced in patients with non-restrictive RV physiology. KE was primarily located in the PR volume at the time of diastolic peak KE, 64 ± 17%.

CONCLUSION

This is the first study showing disturbed KE in patients with rToF and PR, in both the RV and LV. The role of KE as a potential early marker of ventricular dysfunction to guide intervention needs to be addressed in future studies.

KEY POINTS

• Kinetic energy (KE) reflects ventricular performance • KE is a potential marker of ventricular dysfunction in Fallot patients • KE is disturbed in both ventricles in patients with tetralogy of Fallot • KE contributes to the understanding of the pathophysiology of pulmonary regurgitation • Lagrangian coherent structures enable differentiation of ventricular inflows.

The Journey of an Indian Pediatric Cardiologist : Dr. K. C. Chaudhuri Lifetime Achievement Award/Oration at AIIMS, New Delhi, September 2017

The life journey of an Indian pediatric cardiologist, who bestowed considerable attention to the development of new knowledge and train/teach physicians around the world while providing care of patients with heart disease over a 45-y period, is reviewed. This appraisal focuses particular attention on the scientific contributions to the literature. These include spontaneous closure of physiologically advantageous ventricular septal defects, various issues related to a congenital heart defect namely, tricuspid atresia and transcatheter and, interventional pediatric cardiac procedures.

Ventricular kinetic energy may provide a novel noninvasive way to assess ventricular performance in patients with repaired tetralogy of Fallot

OBJECTIVE

Ventricular kinetic energy measurements may provide a novel imaging biomarker of declining ventricular efficiency in patients with repaired tetralogy of Fallot. Our purpose was to assess differences in ventricular kinetic energy with 4-dimensional flow magnetic resonance imaging between patients with repaired tetralogy of Fallot and healthy volunteers.

METHODS

Cardiac magnetic resonance, including 4-dimensional flow magnetic resonance imaging, was performed at rest in 10 subjects with repaired tetralogy of Fallot and 9 healthy volunteers using clinical 1.5T and 3T magnetic resonance imaging scanners. Right and left ventricular kinetic energy (KERV and KELV), main pulmonary artery flow (QMPA), and aortic flow (QAO) were quantified using 4-dimensional flow magnetic resonance imaging data. Right and left ventricular size and function were measured using standard cardiac magnetic resonance techniques. Differences in peak systolic KERV and KELV in addition to the QMPA/KERV and QAO/KELV ratios between groups were assessed. Kinetic energy indices were compared with conventional cardiac magnetic resonance parameters.

RESULTS

Peak systolic KERV and KELV were higher in patients with repaired tetralogy of Fallot (6.06 ± 2.27 mJ and 3.55 ± 2.12 mJ, respectively) than in healthy volunteers (5.47 ± 2.52 mJ and 2.48 ± 0.75 mJ, respectively), but were not statistically significant (P = .65 and P = .47, respectively). The QMPA/KERV and QAO/KELV ratios were lower in patients with repaired tetralogy of Fallot (7.53 ± 5.37 mL/[cycle mJ] and 9.65 ± 6.61 mL/[cycle mJ], respectively) than in healthy volunteers (19.33 ± 18.52 mL/[cycle mJ] and 35.98 ± 7.66 mL/[cycle mJ], respectively; P < .05). QMPA/KERV and QAO/KELV were weakly correlated to ventricular size and function.

CONCLUSIONS

Greater ventricular kinetic energy is necessary to generate flow in the pulmonary and aortic circulations in repaired tetralogy of Fallot. Quantification of ventricular kinetic energy in patients with repaired tetralogy of Fallot is a new observation. Future studies are needed to determine whether changes in ventricular kinetic energy can provide earlier evidence of ventricular dysfunction and guide future medical and surgical interventions.

VEGF-PLCgamma1 pathway controls cardiac contractility in the embryonic heart

The strength of the heart beat can accommodate in seconds to changes in blood pressure or flow. The mechanism for such homeostatic adaptation is unknown. We sought the cause of poor contractility in the heart of the embryonic zebrafish with the mutation dead beat. We find through cloning that this is due to a mutation in the phospholipase C gamma1 (plcgamma1) gene. In mutant embryos, contractile function can be restored by PLCgamma1 expression directed selectively to cardiac myocytes. In other situations, PLCgamma1 is known to transduce the signal from vascular endothelial growth factor (VEGF), and we show here that abrogation of VEGF also interferes with cardiac contractility. Somewhat unexpectedly, FLT-1 is the responsible VEGF receptor. We show that the same system functions in the rat. Blockage of VEGF-PLCgamma1 signaling decreases calcium transients in rat ventricular cardiomyocytes, whereas VEGF imposes a positive inotropic effect on cardiomyocytes by increasing calcium transients. Thus, the muscle of the heart uses the VEGF-PLCgamma1 cascade to control the strength of the heart beat. We speculate that this paracrine system may contribute to normal and pathological regulation of cardiac contractility.

Mechanical pathophysiology of some heart diseases: a theoretical model study

Sarcomere dynamics are related to the global left ventricular (LV) function in some representative pathological states, by using a theoretical model which combines sarcomere function, LV fibrous structure and geometry with the haemodynamic loading conditions. The analysis shows that pressure (concentric) hypertrophy due to hypertension or aortic stenosis is associated with an increase of the normal endocardial-to-epicardial gradient(s) of oxygen demand, which may be one of the causes for the development of endocardial fibrosis. The analysis also indicates that sarcomere shortening is relatively normal in compensated volume (eccentric) hypertrophy. Mitral stenosis demonstrates a case of decreased LV function, secondary to a chronic decrease in LV end diastolic volume, with sarcomeres that operate at their lowest length range. Conversely, the sarcomere function is depressed in cardiomyopathy; the heart's pumping function is maintained by appropriate adjustment mechanisms. However, the sarcomeres show minimal shortening and function at their highest length range with low (or zero) functional reserve. The study thus provides a quantitative tool that relates global LV function to local sarcomere dynamics in various pathological states.

Ebstein's anomaly of the left atrioventricular valve with congenital corrected transposition of the great arteries. Diagnosis by intracavitary electrocardiography

We present the findings in a 13-month-old infant with angiographically confirmed congenital corrected transposition of the great arteries and insufficiency of the left atrioventricular valve. Simultaneous intracavitary electrocardiographic and pressure recordings across the left atrioventricular valve were similar to those obtained in Ebsteins' anomaly and suggested Ebstein's disease of the left atrioventricular valve. To our knowledge, this is the first reported case with intracavitary electrocardiograms in a patient with congenital corrected transposition of the great arteries with Ebstein's malformation of the left atrioventricular valve. The usefulness of the simultaneous recording of the intracavitary ECG and pressure in the diagnosis by catheterization of Ebstein's anomaly of the left atrioventricular valve in patients with congenital corrected transposition of the great arteries is emphasized.