Ramon V. Canent

Right Ventricular Volume Determinations in Children Normal Values and Observations with Volume or Pressure Overload

Right ventricular (RV) volumes were calculated from biplane cineangiocardiograms in 46 patients undergoing diagnostic cardiac catheterization. Validation of methodology was performed by comparison of known and calculated volumes of postmortem RV casts as well as by comparison of cineangiocardiographic RV and left ventricular (LV) stroke volumes of patients without shunts or valvular insufficiency. Seven infants, <1 year of age, with normal right hearts as compared with older children showed smaller RV end-diastolic volumes (39 ± 8 vs 70 ± 13 ml/m2, P < 0.001) as well as decreased RV systolic indices (SI) (3.71 ± 0.68 vs 4.66 ± 1.10 liters/min/m2, P < 0.05). There were no differences between normal infants and older children for RV ejection fraction (EF), RVEDV/LVEDV = 1.01, RVSI/LVSI = 0.99, and RVEF/LVEF = 1.04 vs 0.99. In 13 patients with isolated pulmonary stenosis, RVEDV, RVEF, RVSI, RVEDV/LVEDV, and RVSI/LVSI were not different from normal, but RVEF/LVEF averaged 1.13 vs 0.99 in normal infants, P < 0.05. In contrast, 11 patients studied with atrial septal defect or total anomalous pulmonary venous connection had significant increases in RVEDV (128 ml/m2), RVSI (9.34 liters/min/m2), RVEDV/LVEDV (2.36), RVSI/LVSI (2.81), and RVEF/LVEF (1.17), but normal values for RVEF. There was a significant linear relationship between Qp/Qs from oxygen data and RVSI/LVSI. In three patients studied an average of 1 year following atrial septal defect (ASD) repair, RVEDV remained elevated. In volume overload, alterations in RV volume characteristics are apparent and can be useful in shunt estimation; adaptation to an RV pressure overload, however, is not associated with detectable volume alterations.

Left Heart Volume Estimation in Infancy and Childhood: Reevaluation of Methodology and Normal Values

Left ventricular (LV) volume determinations by the area-length method were reevaluated in postmortem studies of left ventricles ranging from 0.5 to 90 cm3 absolute volume. The regression equation relating known and calculated volumes for calculated volumes <15 cm3 (V′ = 0.733V) was found to be significantly different from that for calculated volumes >15 cm3 (V′ = 0.974V - 3.1). From these equations, normal values for cinecardiographic LV end-diastolic volume (LVEDV), LV ejection fraction (LVEF), LV systolic output (LVSO), LV mass (LVM), and left atrial maximal volume (LAMax) were derived from 56 children (19 < 2 years) with normal left ventricles who underwent cardiac catheterization. Values for LVEDV/BSA were significantly less for infants (< 2 years) than for older children (42 ± 10 versus 73 ± 11 cm3/m2, P <0.001). Values for LAMax/BSA were also less for infants than for older children (26 ± 5 versus 38 ± 8 cm3/ m2, P <0.001), and LVEF was significantly increasel for infants (0.68 ± 0.05 versus 0.63 ± 0.05, P <0.01). The values for LVM/BSA (88 ± 12 g/m2) and LVSO/BSA (4.42 ± 0.95 liters/min/m2) were not significantly different for infants and older children. Multiple regression equations were derived for the prediction of normal volume and mass variables from a patients height, weight, and age. The predicted values can be obtained from nomograms, and estimations of normalcy can be made by comparisons of observed and predicted values with the 95% limits as defined.

Atrial Pressure-Flow Dynamics in Atrial Septal Defects (Secundum Type)

This study was conducted to determine the instantaneous pressure-flow relationships across secundum atrial septal defects. Simultaneous right and left atrial pressures and the pressure difference (determined with an analog computer) were recorded with matched catheter systems. Biplane cineangiocardiography was used to evaluate the timing of the shunts in various phases of the cardiac cycle.These studies indicated that the major left-to-right shunt and pressure gradient occurred over an interval encompassing late ventricular systole and early diastole. Also, there was augmentation of the left-to-right shunt during atrial contraction. Minute right-to-left shunting and pressure gradients occurred at two times in the cardiac cycle: (1) with the onset of ventricular contraction; and (2) during early ventricular diastole (heart rate, 80 to 100 beats/min). Detection of systemic right-to-left shunts by dye curves was enhanced by relatively slow heart rates (prolonged diastasis) which allowed the shunted blood to flow into the left venrticle. The effects of respiration during phasic changes in intrathoracic pressure resulted in an increasing left-to-right gradient during periods of increasing intrathoracic pressure and a fall in the left-to-right gradient across the defect during periods of decreasing intrathoracic pressure.

Left Heart Function in Children with Tetralogy of Fallot before and after Palliative or Corrective Surgery

Left heart volume and left ventricular mass (LV mass) were calculated from biplane cineangiocardiograms in 58 tetralogy of Fallot (TF) patients preoperatively, in 31 patients after shunt procedure, and in 24 patients after complete correction. Preoperatively, the LV end-diastolic volume and left atrial maximal volume (LAmax) were normal in cyanotic infants less than 2.0 years old and in acyanotic patients more than 2.0 years old. These variables, however, were less than normal in cyanotic children > 2.0 years old. Left ventricular ejection fraction (LVEF) and LV systolic index (LVSI) were both less than normal in all groups preoperatively. LV mass was normal preoperatively. After successful shunt procedure, there was a significant increase (P < 0.01) in LVEDV, LVSI, LAmax, and LV mass. The LVEF, however, remained less than normal. After successful corrective surgery, the total group showed a significant increase (P < 0.01) in LVEDV, LVSI, LAmax,and LV mass as compared with preoperative values. Furthermore, the LVEDV was slightly but significantly higher than normal and the LV ejection fraction remained significantly depressed from normal. There was an inverse correlation between LVEDV or LVSI, expressed as a percent of normal, and hemoglobin concentration but not with the net left-to-right shunt or aortic saturation.The decreased LV ejection fraction in cyanotic tetralogy patients in the presence of decreased peak LV pressure (decreased afterload) as well as the decreased LVEF after shunt procedure or complete correction (increased preload) suggests that LV function is depressed in tetralogy patients and remains depressed despite corrective surgery.

Left Heart Volume Characteristics with a Right Ventricular Volume Overload Total Anomalous Pulmonary Venous Connection and Large Atrial Septal Defect

Left heart volume characteristics were evaluated by using biplane cineangiocardiography in 18 studies in 15 patients with total anomalous pulmonary venous connection (TAPVC) and in 37 studies on 35 patients with large secundum or sinus venosus atrial septal defects (ASD). Left ventricular end-diastolic volume (LVEDV) was decreased to less than 67% of normal in five of 15 preoperative TAPVC patients, but the average value for the entire group was not significantly different from normal. In ASD patients, the average LVEDV was 87% of normal which was significantly decreased (P < 0.001). The ejection fraction was decreased from normal in patients with TAPVC and ASD who were less than 2 years of age (0.62 vs. 0.68, P < 0.01), but was normal in older patients. Left ventricular systolic output was significantly decreased from normal in both TAPVC (75% of normal, P < 0.001) and ASD patients (81% of normal, P < 0.001). Left atrial maximal volume was significantly decreased from normal in TAPVC patients averaging only 55% of normal (P < 0.001), but was normal in eight ASD patients. All volume variables increased following corrective surgery in two TAPVC patients and two ASD patients. These studies document that left heart volumes and outputs in infants and children with TAPVC and large isolated atrial defects can be diminished preoperatively.

Left Heart Volume and Mass Quantification in Children with Left Ventricular Pressure Overload

This investigation was designed to quantify left ventricular and left atrial volume, volume change, systolic output, and ventricular mass in 31 patients with isolated left ventricular pressure overload secondary to aortic stenosis (AS, n = 14) or coarctation of the aorta (n = 17). These parameters were compared with normal standards and with data from a group of nine patients with a combined pressure and volume overload due to aortic stenosis plus aortic or mitral insufficiency (AS + AI or MI). Volumes were calculated from biplane cineangiocardiograms exposed at 60 frames/sec. Left ventricular end-diastolic volume (LVEDV) was significantly lower than normal in patients with AS (57 ± 11 cc/m2), but was normal (73 ± 12 cc/m2) in patients with coarctation. An increase in the ejection fraction (LVEF) was found in both groups averaging 0.73 ± 0.12 in AS patients and 0.69 ± 0.09 in coarctation patients. Patients with AS + aortic or mitral insufficiency (AI or MI) showed elevated LVEDV (103 ± 29 cc/m2), but had a normal ejection fraction. The LV mass was significantly increased in all groups: normal, 82 ± 10 g/m2; AS, 126 ± 41 g/m2; coarctation, 130 ± 44 g/m2; and AS + AI or MI, 168 ± 42 g/m2. The left ventricular systolic index and left atrial maximal volume were both normal in patients with pure pressure overload but were significantly increased in patients with combined pressure and volume overload. The low LVEDV in patients with AS as well as the normal volume in patients with coarctation occurred in the presence of elevated LV end-diastolic pressure and indicates a decrease in LV diastolic distensibility in patients responding to an isolated LV pressure overload by significant muscular hypertrophy without dilatation.

Characterization of Left Heart Volumes and Mass in Normal Children and in Ifants with Intrinsic Myocardial Disease

Quantitation of myocardial volumes, mass, and ejection fractions was performed in a group of 26 patients (10 of whom were infants less than 2 years old) with normal left ventricles and in a separate group of 13 children with intrinsic myocardial disease and clinical decompensation. All patients were studied by use of biplane cineangiocardiography, and volumes were determined by the area-length method. Left ventricular end-diastolic volume in normal infants below 2 years of age was 44.8 ± 8.5 cc/m2, and it was 71.4 ± 8.0 cc/m2 in older normal children (P<0.001), ages 3 to 16 years. Left ventricular ejection fraction also was different in the younger normals: 0.76 ± 0.07 versus 0.63 ± 0.05 in older normals (P<0.001). Left ventricular mass and left atrial maximal volume were not significantly different in normal infants and older children, averaging 81.7 ± 10.0 g/m2 and 33.6 ± 10.1 cc/m2, respectively. All patients in the cardiomyopathy group had significant elevations of left ventricular end-diastolic volume and mass, and the ejection fraction was reduced in all patients except one infant with severe mitral insufficiency. Five infants with chronic left ventricular failure and no mitral insufficiency had normal left atrial maximal volumes. Left atrial maximal volumes were increased significantly in six patients with myocardial disease, all of whom had mitral insufficiency. These results emphasize the potential value of the quantitative estimation of left heart volume and provide normative base-line data for left heart volume and mass parameters in both infants and children.

Intracardiac Pressure-Flow Dynamics in Isolated Ventricular Septal Defects

This study was conducted to determine the nature of intracardiac shunting in 50 patients between the ages of 3 and 15 years with isolated ventricular septal defects. Simultaneous right and left ventricular pressures and biplane cineangiocardiography were utilized to study the timing and the direction of flow across the defect. Patients with low to moderately elevated right ventricular pressures demonstrated left-to-right shunting across the defect throughout the cardiac cycle. When pressure in the right ventricle approximated that of the left, right-to-left shunting occurred across the defect into the left ventricle during isovolumic relaxation. All patients shared in common the following: (1) a predominant left-to-right gradient and shunt across the defect into the body of the right ventricle during diastole; and, (2) augmentation of the left-to-right gradient with resultant increase of the shunt into the right ventricle during isovolumic contraction immediately preceding opening of the aortic valve.In comparing patients with and without pulmonary hypertension, the major variations in the cardiac cycle occurred during the periods of ventricular ejection and isovolumic relaxation. These two periods are primarily affected by the changing relationships of the size of the defect, ratio of pulmonary to systemic resistance, and magnitude of net shunts.

In Vivo Pressure-Radius Relationships of the Pulmonary Artery in Children with Congenital Heart Disease

The effects of either increased pulmonary artery blood flow or pressure on the magnitude of the radius and the dynamic properties of the right pulmonary artery were studied angiographically in 162 patients during cardiac catheterization. Patients were divided into seven groups according to their hemodynamic findings. The right pulmonary artery radius was measured during systole and diastole, from the projected films, at the midpoint between the bifurcation of the main pulmonary artery and the bifurcation of the right pulmonary artery. The mean pulmonary artery radius was increased in patients with either increased pulmonary blood flow or pressure, and in patients with isolated valvular pulmonic stenosis. Both the pressure-strain elastic modulus (stiffness index) and the tension-radius regression were different from normal only in patients with increased pulmonary artery pressure regardless of the pulmonary blood flow. This finding indicates that the pulmonary artery is stiffer in patients with pulmonary hypertension but that its elastic properties are not altered secondarily to increased blood flow.

Evaluation of Left Ventricular Contractile State in Childhood Normal Values and Observations with a Pressure Overload

Left ventricular contractile state was evaluated in 20 children ages 3 to 11 years with normal left hearts and in 15 children ages 2 to 16 years with a left ventricular pressure overload. All patients were studied during diagnostic cardiac catheterization with catheter-tip micromanometry. Pressure-velocity curves were obtained during isovolumic systole by plotting (dp/dt)/28 P versus developed or total pressure (P). Computer analysis of five cardiac cycles was used to yield one composite pressure-velocity curve for each patient with both linear and second-degree polynomial curve analysis. The developed pressure method yielded higher values for the calculated Vmax index, (dp/dt)/28 P at zero P than the total-pressure method for all patients. Normal standards were defined for both methods. The Vmax index calculated with total pressure as well as peak (dp/dt)/28 P was significantly less than normal for the hypertrophy group. The Vmax index calculated with developed pressure was not significantly different from normal for the entire hypertrophy group, but four of the 15 patients showed a depression of contractile state defined as a value for the Vmax index less than 2 SD of normal. These results indicate the potential importance of preoperative and postoperative estimation of contractile state in patients with a left ventricular pressure overload in evaluation of possible irreversible alterations of contractility that may accompany myocardial hypertrophy.