Dependence of canine right coronary arterial flow upon heart rate and right ventricular pressure

There is a paucity of knowledge regarding right coronary pulsatile hemodynamics when the right ventricle is under hemodynamic overload as is often the case in pediatric patients with congenital cardiac anomalies. To elucidate the exact mechanisms for the right coronary artery (RCA) to cope with the overload, we studied nine open-chest adult Beagles and analyzed the flow signals of the RCA in relation to independently varied heart rate (pacing) and right ventricular pressure (pulmonary artery banding). Both increased heart rate and right ventricular pressure increased the total volume flow of the RCA. The diastolic over total flow ratio (D/T), however, enlarged on increasing right ventricular pressures while it declined on increasing heart rates. Our data confirmed, as well, that increased flow of RCA on rising heart rate was provided mainly by an increase in systolic phase, while the increase on augmented right ventricular pressure was provided by the increase in diastolic phase. The RCA manages to deliver blood to the right ventricular musculature in two different ways in response to increasing heart rate and right ventricular pressure.     

Effects of red cell transfusion on pulmonary blood flow and right ventricular systolic time intervals in neonates

Blood transfusion increases blood volume and blood viscosity of the neonate. Since both volume expansion and increase in blood viscosity may be associated with increased pulmonary artery pressure, we studied effects of transfusion (10 ml of red blood cells per kilogramme of body weight) on right ventricular output and right systolic time intervals by means of pulsed-Doppler echocardiography in 38 preterm infants with a mean (SD) gestational age of 28 (5) weeks (range 25–34), birth weight 1060 (395) g (range 480–1910), actual body weight 1875 (450) g (range 820–2790) and postnatal age of 44 (23) days (range 17–105). After transfusion, packed cell volume and haemoglobin increased significantly from 0.26 (0.044) to 0.38 (0.046), and from 8.2 (1.6) g/l to 12.8 (1.9), respectively. Blood viscosity increased from 1.78 (0.3) mPa to 2.68 (0.4) by 33%. Right ventricular output decreased significantly from 320 (57) ml/kg/min to 290 (70) due to decrease in heart rate by 7%. Blood pressure and right ventricular stroke volume did not change. There was a significant increase in pulmonary red cell transport (right ventricular output times packed cell volume) of 21%. Right ventricular pre-ejection period (RPEP), right time peak velocity (RTPV), right ventricular ejection time (RVET), and ratios of RTPV/RVET_(c), RPEP:RVET did not change after transfusion. Conclusion These results suggest that neither pulmonary artery pressure nor right ventricular function changed as a result of transfusion in spite of rising blood volume and blood viscosity. Received: 19 October 1996 / Accepted: 23 December 1996     

A longitudinal study of blood pressure,cholesterol and left ventricular muscle volume in children: The Shimane Heart Study

Three hundred and forty-four healthy schoolchildren living in Izumo City, Shimane Prefecture, Japan, were assessed at 3 year intervals from 6 to 15 years, starting in 1978 (Cohort 1) or 1981 (Cohort 2). Tracking indices (Ti) were calculated as follows: Ti = (2x + y - z)/N/0.89, where x, y and z refer to the total number in the same, adjacent and remote trisections, respectively, and N = x + y + z. If Ti > 1, there is positive tracking. For systolic blood pressure (SBP) measurements (except at 6 years old) and serum cholesterol levels, all Ti were greater than 1.0 regardless of the time when tracking was commenced. Tracking indices were slightly greater in the serum cholesterol levels than in the SBP measurements. Left ventricular muscle volume indices (LVMVI) were calculated by echocardiographic measurements. In girls, the LVMVI was larger only in the above-median SBP group at the age of 12 years (P < 0.01), but the LVMVI of the higher SBP (above median) group was larger than in the lower (below median) group at every age in boys; the difference was statistically significant (P < 0.05) at 12 and 15 years of age. Left ventricular mass enlargement may occur in the prehypertensive stage in humans as well as in rats.     

Postnatal development of the cerebral blood flow velocity response to changes in CO2 and mean arterial blood pressure in the piglet

Cerebral blood flow velocity was studied during changes (haemorrhage) in mean arterial blood pressure or P _aCO₂ in 56 (aged 0–26 days) anaesthetized and ventilated piglets. The CO₂ reactivity increased with age from 6.5% kPa⁻'(< 1 day) to adult levels of 25% kPa⁻¹ for piglets over 4 days old. The mean arterial blood pressure reactivity was reduced from 1.3% mmHg⁻¹ (< 1 day old) to 0.0%/ mmHg (> 4 days old). The reactivities were similar with two different anesthetics: chloralose/urethane or pentobarbital. To validate the cerebral blood flow velocity data, both electromagnetic flow and precerebral Doppler ultrasound velocity were recorded from the same common carotid artery with extracranial branches tied off. There were no differences between the results with these two methods nor between these results and those obtained when the cerebral blood flow velocities were recorded from an intracerebral artery and the electromagnetic flowmeter recorded from the carotid artery. The vessel diameter appears stable during these interventions. In conclusion, the autoregulatory response and the reaction to P _aCO₂ appear poorly developed in the newborn piglet, but rapidly mature during the first 4 days of life.     

Use of an Amplatzer Duct Occluder for Closing an Aortico-Left Ventricular Tunnel in a Case of Noncompaction of the Left Ventricle

Aortico-left ventricular tunnel (ALVT) is a very rare congenital anomaly. Noncompaction of the left ventricle or spongy myocardium is another rare congenital cardiomyopathy. We report probably the first case in which these two rare anomalies causing pump failure coexisted in a 4-year-old male and the tunnel was successfully treated nonsurgically. Transcatheter closure of ALVT with the Amplatzer duct occluder is feasible and safe in a case of noncompaction of the LV with reduced LV function.     

Peripheral circulation in the newborn: Interaction of peripheral blood flow,blood pressure,blood volume,and blood viscosity

Peripheral blood flow and systolic blood pressure (strain-gauge plethysmograph), blood volume (Evans blue) and whole blood viscosity (cone-plate viscometer) have been measured in 66 premature and full-term infants 6 to 144h of age. Blood flow and blood volume were moderately decreased in the infants with respiratory distress. Highly significant (P<0.001) correlations were found betwen blood flow and blood volume (r=0.77), blood pressure and blood volume (r=0.50), peripheral resistance and blood volume (r=-0.44), blood flow and blood pressure (r=0.50), blood flow and peripheral resistance (r=-0.67), peripheral resistance and blood viscosity (r=0.45), and blood viscosity and haematocrit (r=0.86). There was no correlation between peripheral blood flow and blood viscosity. However, at given blood volume, peripheral blood flow decreased with increasing blood viscosity. These results indicate that in newborn infants peripheral blood flow, blood pressure and peripheral resistance are influenced by blood volume, but also depend on blood viscosity.Supported by Deutsche Forschungsgemeinschaft (SFB 147)     

Effects of heart rate and right ventricular pressure on right coronary arterial flow and its systolic versus diastolic distribution in a variety of congenital heart diseases in children

BACKGROUND AND METHODS: In order to elucidate the underlying adjusting mechanism of human right coronary arterial (RCA) flow to increased right ventricular pressure (RVP) in children, we recorded RCA flow velocity in 24 pediatric cardiac patients at the orifice of its main trunk at the time of heart catheterization using the Doppler guidewire. RESULTS: The ratio of diastolic flow (DF)/total flow (TF), or the proportion of the DF time integral over a total of one cardiac cycle, had a negative correlation with heart rate (HR; r = -0.58, n = 11) in children with normal right ventricular systolic pressure (RVSP; RVSP < 35 mmHg). In contrast, the DF/TF ratio had a good correlation (r = 0.88, n = 24) with RVSP in all patients under study. The ratio of diastolic area (DA)/total area (TA), defined as the ratio of an area encircled by the aortic pressure curve above and the RVP curve below for diastole, over a total of one cardiac cycle, representing the overall effect of both HR and transcoronary pressure difference, also correlated well (r = 0.89, n = 24) with DF/TF. Total volume flow of the RCA also increased (r= 0.76, n = 24) with increases in RVSP, first by an increase in flow velocity through the RCA, during both systole and diastole, then by widening of the RCA lumen at very high pressures. These changes were initially more dependent on diastole with increasing RVSP because: (i) of a more marked augmentation of flow velocity in diastole compared with systole; and then (ii) of a significant decrease in flow velocity in systole at very high pressures. CONCLUSIONS: We clarify how the RCA manages to increase flow through it at different HR as a function of chronic RVP overload in pediatric cardiac patients.     

Left atrial diameters in overweight children with normal blood pressure

OBJECTIVE: To measure left atrial (LA) diameter in normotensive, overweight children and to determine the variables that independently influence LA diameters. STUDY DESIGN: A cross-sectional study on 22 overweight children (age, 13.40 +/- 1.22 years) and 18 control children (age, 13.40 +/- 2.19 years) was performed. LA diameter, left ventricular (LV) geometry, and LV systolic/diastolic function were measured through echocardiography. Data were compared between the two groups. Multiple regression analysis, with LA diameter as dependent variable, was conducted. RESULTS: In the overweight group, LV diastolic dimension, LV mass index, peak S, S/D ratio, Am, maximal LA diameter (34.1 mm vs 25.4 mm), middle LA diameter (26.9 mm vs 18.1 mm), and minimal LA diameter (22.5 mm vs 16.1 mm) were increased and Em/Am ratio was decreased. In multiple regression analysis, body mass index (R(2) = 0.7040, 0.7085, 0.7406 in respective maximal, middle, and minimal LA diameter) and systolic blood pressure (R(2) = 0.0540, 0.0477, 0.030 in respective maximal, middle, and minimal LA diameter) were significant independent correlates of all three measures of LA diameter. CONCLUSIONS: LA diameter in normotensive overweight children is increased. Body mass index and systolic blood pressure were significant correlates of LA diameter.     

Alterations of intracranial pressure and cerebral blood flow velocity in healthy neonates and their implication in the origin of perinatal brain damage

Intracranial pressure and cerebral blood flow velocity were recorded in term healthy neonates during the first 3 days of life using non-invasive methods (LADD-fontanometry and cw-Doppler sonography). Intracranial pressure increased from 4.0±2.7 cm H₂O to 5.8±2.7 cm H₂O and maximal cerebral blood flow velocity in the anterior cerebral artery (ACA) increased from 33 cm/s to 58 cm/s as calculated from a Doppler shift of 0.63 to 1.10 kHz and vascular resistance decreased between the 1st and 3rd day of life. These alterations could not be demonstrated in the femoral artery. This is in accordance with other registrations obtained by different methods and under various conditions. They allow an explanation of some well known physiological phenomena like alterations of cranial volume and the structure of the bony skull in the first days of life. Furthermore, these physiological variations may have implications for the origin of cerebral damage during the perinatal period, especially of hypoxic-ischaemic encephalopathies.Abbreviations ACA anterior cerebral artery - CA carotid artery - FA femoral artery - IP intracranial pressure - MFV mean flow velocity - PI pulsatility index (Pourcelot) - REM rapid eye movements sleep state - TAM time-average-mean - V cranial volume     

Double-Outlet Right Ventricle (Tetralogy of Fallot Type) Associated with Anomalous Origin of the Left Coronary Artery from the Right Pulmonary Artery: Report of Successful Total Repair in a 2-Month-Old Infant

The case reported herein demonstrates the rare association of double-outlet right ventricle (tetralogy of Fallot type) with anomalous origin of the left coronary artery from the pulmonary artery. It is the first reported successful total surgical repair in an infant.     

Early versus late cord clamping: effects on peripheral blood flow and cardiac function in term infants

BACKGROUND: In the debate on the best cord clamping time in newborn infants, we hypothesized that late cord clamping enables an increased volemia due to blood transfer to the newborn from the placenta. AIM: To assess whether clamping time can affect limb perfusion and heart hemodynamics in a group of 22 healthy term newborn infants. STUDY DESIGN: A case-control study. SUBJECTS: Eleven early-clamped (at 30 s) vaginally-delivered newborn infants were compared with eleven late-clamped (at 4 min) newborns. OUTCOME MEASURES: The two groups were studied using near-infrared spectroscopy and M-mode echocardiography. RESULTS: Late cord clamping coincided with a higher hematocrit (median 62% versus 54%) and hemoglobin concentration (median 17.2 versus 15 g/dL), whilst there were no changes in bilirubin level. Echocardiography showed a larger end-diastolic left ventricle diameter (1.7 cm median value versus 1.5) coupled with unvaried shortening and ejection fraction values. There were no changes in calf blood flow, oxygen delivery, oxygen consumption or fractional oxygen extraction calculated from the NIRS measurements, or in foot perfusion index. CONCLUSIONS: Our results demonstrated that late cord clamping coincides with an increased placental transfusion, expressed by higher hematocrit and hemoglobin values, and larger left ventricle diameter at the end of the diastole, with no changes in peripheral perfusion or oxygen metabolism.     

Randomized trial of high-frequency oscillatory ventilation versus conventional ventilation: effect on systemic blood flow in very preterm infants

OBJECTIVE: Low superior vena cava (SVC) flow is common in very preterm infants in the first day and strongly associated with periventricular hemorrhage and disability. We examined the effect of high-frequency oscillatory ventilation (HFOV) compared with conventional ventilation (CV) on SVC flow and right ventricular output. METHODS: Forty-five infants <29 weeks were randomized before 1 hour of age to HFOV or CV. Echocardiography was performed on 43 infants at 3, 10, and 24 hours of age. Infants with low SVC flow (<50 mL/kg/min) or hypotension (mean blood pressure < or =20) were treated with volume and inotrope. RESULTS: Infants allocated to HFOV (n=23) and to CV (n=20) were well matched. There was a nonsignificant trend toward more infants on HFOV having SVC flow <50 mL/kg/min (48% vs 20%) and receiving volume and inotropes (61% vs 40%). There were no significant differences in mean SVC flow or right ventricular output at 3, 10, or 24 hours. Infants on HFOV had a significantly higher calculated upper body vascular resistance at 10 hours and mean blood pressure at 24 hours. CONCLUSIONS: There were no significant adverse effects of HFOV on systemic blood flow in very preterm infants during the first 24 hours of life.