Normal patterns of flow in the superior caval, hepatic and pulmonary veins as measured using Doppler echocardiography during childhood

Surgical Outcomes of Total Anomalous Pulmonary Venous Connection Repair

Background and Objectives: Over the years, surgical repair of total anomalous pulmonary venous connection (TAPVC) outcomes have improved, however, morbidity and mortality still remain significant. This study aims to assess the early and long-term outcomes of surgical treatment of TAPVC children, operated on between 2006 and 2016, in one pediatric center in Poland. Materials and Methods: Diagnostics, surgical treatment, and follow-up data from 83 patients were collected. In addition, survival and risk factor analyses, control echocardiographic, and electrocardiographic examinations were performed. Results: In the analyzed group (n = 83), there were seven hospital deaths (within 30 days after the operation) (8.4%) and nine late deaths (10.8%). The mean follow-up time was 5.5 years, and, for patients who survived, it was 7.1 years. The mean survival time in patients with completed follow-up (n = 70) was 10.3 years; the overall five-year survival rate was 78.4%. Independent mortality risk factors were type I TAPVC, single ventricle physiology, time from admission to operation, intensive care unit stay, postoperative hospital stay, and temporary kidney insufficiency requiring dialysis. Conclusions: The presence of single ventricle physiology and the supracardiac subtype of TAPVC might be negative prognostic factors, while normal heart physiology presents with good post-repair results. This study indicates that cardiac arrhythmias may occur. Morbidity and mortality, related to surgical TAPVC correction, still remain significant.

Convective Leakage Makes Heparin Locking of Central Venous Catheters Ineffective Within Seconds: Experimental Measurements in a Model Superior Vena Cava

Central venous catheters (CVCs), placed in the superior vena cava (SVC) for hemodialysis or chemotherapy, are routinely filled while not in use with heparin, an anticoagulant, to maintain patency and prevent thrombus formation at the catheter tip. The heparin-locking procedure, however, places the patient at risk for systemic bleeding, as heparin is known to leak from the catheter into the blood stream. We provide evidence from detailed in vitro experiments that shows the driving mechanism behind heparin leakage to be convective-diffusive transport due to the pulsatile flow surrounding the catheter. This novel mechanism is supported by experimental planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) measurements of flow velocity and heparin transport from a CVC placed inside a model SVC inside a pulsatile flow loop. The results predict an initial, fast (<10 s), convection-dominated phase that rapidly depletes the concentration of heparin in the near-tip region, the region of the catheter with side holes. This is followed by a slow, diffusion-limited phase inside the catheter lumen, where the concentration is still high, that is insufficient at replenishing the lost heparin concentration in the near-tip region. The results presented here, which are consistent with previous in vivo estimates of 24 hour leakage rates, predict that the concentration of heparin in the near-tip region is essentially zero for the majority of the interdialytic phase, rendering the heparin locking procedure ineffective.

Reference intervals for the echocardiographic measurements of the right heart in children and adolescents: a systematic review

Background

Transthoracic echocardiography is the primary imaging modality for the diagnosis of right ventricular (RV) involvement in congenital and acquired heart diseases. There is increasing recognition of the contribution of RV dysfunction in heart diseases affecting children and adolescents, but there is insufficient information on reference intervals for the echocardiographic measurements of the right heart in children and adolescents that represent all the continental populations of the world.

Objective

The aim of this systematic review was to collate, from published studies, normative data for echocardiographic evaluation of the right heart in children and adolescents, and to identify gaps in knowledge in this field especially with respect to sub-Saharan Africans.

Methods

We performed a systematic literature search to identify studies of reference intervals for right heart measurements as determined by transthoracic echocardiography in healthy children and adolescents of school-going age. Articles were retrieved from electronic databases with a combination of search terms from the earliest date available until May 2013.

Results

Reference data were available for a broad range of variables. Fifty one studies out of 3096 publications were included. The sample sizes of the reference populations ranged from 13 to 2036 with ages varying from 5 to 21 years. We identified areas lacking sufficient reference data. These included reference data for determining right atrial size, tricuspid valve area, RV dimensions and areas, the RV % fractional area change, pulmonary artery pressure gradients and the right-sided haemodynamics, including the inferior vena cava dimensions and collapsibility. There were no data for sub-Saharan African children and adolescents.

Conclusion

Reliable reference data are lacking for important echocardiographic measurements of the RV in children and adolescents, especially for sub-Saharan Africans.

Dynamic relationships between catecholamine-induced shifts of pressure and blood flow in pulmonary artery

Experiments on cats showed that catecholamines produced maximum changes in pulmonary artery blood pressure during 12-16 sec postinjection, while blood flow in this artery attained maximum only to 40 sec postinjection, i.e. changes in blood flow attained maximum and ended later than blood pressure shifts. Intravenous epinephrine produced bidirectional changes in blood pressure, while norepinephrine always elevated blood pressure in the pulmonary artery; pulmonary circulation increased after injection of both catecholamines.

Normal Doppler spectral waveforms of major pediatric vessels: specific patterns

Every major vessel in the human body has a characteristic flow pattern that is visible in spectral waveforms obtained in that vessel with Doppler ultrasonography (US). Spectral waveforms reflect the physiologic status of the organ supplied by the vessel, as well as the anatomic location of the vessel in relation to the heart. In addition, the waveforms may be affected by age- and development-related hemodynamic differences. For example, adults tend to have higher flow velocities, whereas neonates, particularly those born prematurely, have higher resistance to flow, especially in the cerebral and renal vascular beds. As Doppler US is performed with increasing frequency for vascular evaluation in children, the recognition of normal flow patterns has become imperative. Familiarity with the waveforms characteristic of specific veins and arteries in children is important. In addition, an understanding of the hemodynamic factors involved provides a useful basis for interpreting waveform abnormalities.

Right ventricular restrictive physiology in repaired tetralogy of Fallot is associated with smaller respiratory variability

BACKGROUND

Long-term outcomes of patients with repaired tetralogy of Fallot (TOF) are known to be related with right ventricular (RV) volume overload, severity of pulmonary insufficiency (PI) and the type of outflow repair. Right ventricular restrictive physiology (RVRP) has also been reported to interfere with several factors influencing the late result in repaired TOF patients. However, the mechanism and physiology of this unique myocardial property in the chronically overloaded right ventricle are not yet clearly understood.

METHODS

We investigated 43 patients after repair of TOF to assess the relationships among biventricular diastolic function, volume characteristics, and influence of respiratory effort. The patients were classified into 3 groups; 15 patients with RVRP and significant PI (RP group, 35%), 19 without RVRP in the presence of significant PI (NR+PI group, 44%), and 9 without RP or significant PI (NR-PI group, 21%). Doppler spectrals obtained by echocardiography from systemic and pulmonary veins, main pulmonary artery (MPA), and both ventricular inlets, and biventricular diastolic function were compared according to the respiratory cycle.

RESULTS

The RP group revealed higher pulmonary venous systolic/diastolic flow ratio (S/D ratio) and the NR+PI group showed larger velocity-time integral (VTI) ratio of total regurgitant/antegrade flow at the MPA and more respiratory variability in the systemic vein.

CONCLUSION

RP is associated with less volume overload of the RV and smaller respiratory variability is also associated with the restrictive RV. The diastolic function and volume status of the RV may influence the diastolic properties of the left heart.

The characteristics of the spectra of superior venae cavae in patients with right heart failure

Background

Aimed to elucidate the characteristics of the spectra of superior venae cavae (SVC) in respiratory cycles in patients with right heart failure.

Methods

The spectra of SVC of 30 patients with right heart failure and 30 paired healthy subjects were recorded through right supraclavicular fossa view. The profiles of spectra of superior venae cavae were observed, and peak velocity and velocity time integral (VTI) of every wave of SVC under spontaneous respiration were measured for statistical analysis.

Results

In healthy subjects, the peak velocities and VTI of S wave and D wave increased in inspiratory phase and diminished in expiratory phase, and which of S wave were larger than which of D wave in whole respiratory cycle. In patients with right heart failure, spectral variations of SVC could be classified into three patterns: Pattern I: peak velocities and VTI of S wave were larger than that of D wave in early inspiratory phase, but peak velocities and VTI of D wave were larger than those of S wave in late inspiratory phase and early expiratory phase [Pattern I-1], even in whole respiratory cycle [Pattern I-2]; Pattern II: the S wave disappeared and was substituted by inverse wave with low amplitude in whole respiratory cycle. Pattern III: the profiles of the spectra of SVC in patients were similar to those of healthy subjects. In the whole, the respiratory variation ratios of peak velocities and VTI of S wave and D wave were diminished in patients compared with those in healthy subjects.

Conclusion

The spectra of superior venae cavae in patients with right heart failure were abnormal, and these characteristics could be used as signs in evaluating right heart failure.