Absence Of Shunt Research Articles

Intracranial Pediatric Vascular Abnormalities: an Imaging Approach

Neurovascular disease is less common in children than in adults. Although it corresponds to a small proportion of pediatric pathologies, it represents a clinical challenge because the signs and symptoms are nonspecific, and when the patient presents with stroke or hemorrhage, it is associated with high morbidity and mortality. Intracranial pediatric vascular pathologies can be classified into several types. In this article, we propose a didactic classification based on the presence or absence of shunting and a subclassification of nonshunting arterial diseases according to vessel morphology. From this radiologic perspective, a differential group of pathologies can be included to characterize the specific findings of each disease. In addition to identifying the etiology, gaining insights into the natural evolution of the disease is crucial for the better care of this specific group of patients, which, in some cases, will be evaluated recurrently throughout their lifetimes.Learning Objective: To describe the main imaging aspects and categorize the pediatric intracranial vascular pathologies.

Patent Ductus Arteriosus and Lung Magnetic Resonance Imaging Phenotype in Moderate and Severe Bronchopulmonary Dysplasia-Pulmonary Hypertension.

Rationale: Hemodynamically significant patent ductus arteriosus (hsPDA) in premature infants has been associated with bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH). However, these associations remain incompletely understood. Objectives: To assess the associations between hsPDA duration and clinical outcomes, PH, and phenotypic differences on lung magnetic resonance imaging (MRI). Methods: In this retrospective cohort study, we identified all infants with BPD at <32 weeks' gestation who also underwent research lung MRI at <48 weeks' postmenstrual age (PMA) from 2014 to 2022. Clinical echocardiograms were reviewed for hsPDA and categorized as no hsPDA, hsPDA 1-60 days, and hsPDA >60 days. Outcome variables included BPD severity, PH at 36 weeks' PMA, PH after 36 weeks' PMA in the absence of shunt (PH-pulmonary vascular disease [PVD]), tracheostomy or death, and lung phenotype by MRI via modified Ochiai score, indexed total lung volume, and whole-lung hyperdensity. Logistic regression and ANOVA were used. Measurements and Main Results: In total, 133 infants born at 26.2 ± 1.9 weeks, weighing 776 ± 276 g, were reviewed (47 with no hsPDA, 44 with hsPDA 1-60 days, and 42 with hsPDA >60 d). hsPDA duration > 60 days was associated with BPD severity (P < 0.01), PH at 36 weeks' PMA (adjusted odds ratio [aOR], 9.7 [95% confidence interval (CI), 3.3-28.4]), PH-PVD (aOR, 6.5 [95% CI, 2.3-18.3]), and tracheostomy or death (aOR, 3.0 [95% CI, 1.0-8.8]). Duration of hsPDA > 60 days was associated with higher Ochiai score (P = 0.03) and indexed total lung volume (P = 0.01) but not whole-lung hyperdensity (P = 0.91). Conclusions: In infants with moderate or severe BPD, prolonged exposure to hsPDA is associated with BPD severity, PH-PVD, and increased parenchymal lung disease by MRI.

304Cryoablation versus Radiofrequency Ablation of the Atrioventricular Node in Patients with His-bundle Pacing

Abstract Background Atrioventricular node (AVN) ablation in the setting of His bundle pacing (HBP) may be challenging due to risk of compromising the function of the His lead. Cryoablation (CRYO) may offer theoretical advantages over conventional radiofrequency ablation (RFA), due to absence of shunting of current to the His lead, more discrete lesions, and potential reversibility in case of transient elevation of capture thresholds. However, CRYO has never been tested for AVN ablation in this setting. Purpose To compare procedural characteristics and outcome of CRYO compared to RFA for AVN ablation in patients with HBP. Methods Thirty-five patients (age 76 ± 8 yrs, 23% male) with HBP underwent AVN ablation for an "ablate and pace" indication. CRYO was performed in the first 22 pts and RFA in the following 13 pts. Procedure and fluoroscopy times, change in His threshold and success rates were compared between groups. Results The acute procedural success rate was 100% for both strategies without any major complications. There were no significant differences in procedure characteristics and outcome between CRYO and RFA, except for significantly shorter application times with RFA and a trend to more frequent reconduction and requirement for a redo procedure with CRYO (see table). All recurrences occurred within one month after ablation. Conclusion CRYO does not seem to offer any advantage over RFA for AVN ablation in patients with HBP, and does not avoid rise of His capture thresholds. Moreover, the recurrence rate may be higher with CRYO leading to more redo procedures. Table Parameter CRYO (22 pts) RFA (13 pts) P-value Total procedure time (min) 50 [38 - 63] 40 [33 - 53] 0.257 Fluoroscopy time (min) 5.0 [2.2 - 5.4] 3.5 [1.9 - 9.0] 0.578 Expo Rx (mcGy.cm2) 237 [110 - 525] 139 [65 - 721] 0.468 Number of applications (n) 6 [3 - 11] 4 [1 - 15] 0.371 Total application time (min) 17 [9 - 29] 3 [1 - 9] 0.001 His threshold pre-ablation (V) 1.63 [0.75 - 3.44] 0.75 [0.53 - 1.63] 0.180 His threshold post-ablation (V) 1.88 [0.75 - 3.81]* 1.25 [0.63 - 3.50] 0.389 His threshold change (V) 0.00 [0.00 - 0.31]* 0.00 [0.00 - 0.75] 0.933 His threshold rise ≥1 volt (n) 4 (18%)* 3 (23%) 0.726 Acute procedural success (n) 22 (100%) 13 (100%) 1.000 AV reconduction during follow-up (n) 5 (23%) 1 (8%) 0.254 AV reconduction needing redo procedure (n) 3 (14%) 0 0.146 Interquartile range is shown in square brackets. *one loss of capture.

Imaging Bulk and Edge Transport near the Dirac Point in Graphene Moiré Superlattices.

Van der Waals structures formed by aligning monolayer graphene with insulating layers of hexagonal boron nitride exhibit a moiré superlattice that is expected to break sublattice symmetry. Despite an energy gap of several tens of millielectronvolts opening in the Dirac spectrum, electrical resistivity remains lower than expected at low temperature and varies between devices. While subgap states are likely to play a role in this behavior, their precise nature is unclear. We present a scanning gate microscopy study of moiré superlattice devices with comparable activation energy but with different charge disorder levels. In the device with higher charge impurity (∼1010 cm-2) and lower resistivity (∼10 kΩ) at the Dirac point we observe current flow along the graphene edges. Combined with simulations, our measurements suggest that enhanced edge doping is responsible for this effect. In addition, a device with low charge impurity (∼109 cm-2) and higher resistivity (∼100 kΩ) shows subgap states in the bulk, consistent with the absence of shunting by edge currents.

226 Accuracy and Precision of a New Method for Hemodynamic Assessment in Children Undergoing Cardiac Surgery Based on Ultrasound Dilution Methodology

Background and aims: This novel monitor (COstatus, Transonic Systems Inc., Ithaca, NY) uses existent intravascular lines for injections of isotonic saline to measure CO and BV (blood volume) by ultrasound dilution methodology. It can also identify the presence of cardiac shunts. We investigated the accuracy and precision of the method during pediatric congenital heart surgery (CHS).Methods: 9 pts scheduled for CHS [age 8 (0-39) months; weight 7.6 (3.2 - 14.1) kg] were included. Measurements (2-4 injections of saline 0.5-1 mL/kg/session) started in the OR, before/immediately after CPB and then repeated in PICU at 2, 3, 4, 5, 6, 12 and 24 h after weaning. Accuracy was tested in the OR using transit time technology (TT).Results: 56 measurement-sessions were performed. In 5 pts, during stable hemodynamic conditions, TT was simultaneously obtained (Fig 1). We identified left-to-right shunts in 12 sessions. The coefficient of variation (CV= SD/mean) was calculated for CO, central BV index (CBVI), total end-diastolic volume index (TEDVI), and active circulation volume index (ACVI) in each session.[Accuracy] Table Table Full size table Conclusions: COStatus offers reproducible measurements in pediatric patients. It does not require insertion of dedicated catheters. In the absence of shunts, two injections are typically adequate for data collection; in the presence of shunts, more injections may be required.

Comments on Point:Counterpoint: Exercise-induced intrapulmonary shunting is imaginary vs. real

Comments on Point:Counterpoint: Exercise-induced intrapulmonary shunting is imaginary vs. real

Time-Resolved Spinal MR Angiography: Initial Clinical Experience in the Evaluation of Spinal Arteriovenous Shunts

Spinal arteriovenous shunts usually require digital subtraction angiography (DSA) for evaluation. We report a unique time-resolved spinal MR angiographic (TRSMRA) technique with a temporal resolution of 3-6 seconds and spatial resolution of approximately 1 mm(3) that has the potential to noninvasively detect, localize, and follow-up these cases. Eleven patients with clinical presentation and/or MR findings suspicious for a spinal arteriovenous shunt were referred for TRSMRA. Patients subsequently underwent spinal DSA to confirm the presence or absence of a shunt or were followed clinically until an alternative diagnosis was found. TRSMRA was also used to predict the level of the shunt in the positive cases. In addition, 2 of these patients as well as a 12th patient referred to us posttreatment received a follow-up TRSMRA to assess treatment outcome. Early venous shunting was identified by using TRSMRA in 6 cases. All 6 were confirmed to have an AV shunt on subsequent spinal DSA. The shunt level predicted by TRSMRA consistently correlated with DSA to within 1 vertebral level. In the 5 patients with a negative screening TRSMRA, DSA or clinical outcome confirmed the absence of an arteriovenous shunt in all of the cases. Posttreatment TRSMRA in 3 patients accurately assessed the success or failure of treatment. Combining acceleration techniques to achieve high frame rate TRSMRA provides sufficient temporal and spatial resolution to identify, localize, and follow patients suspected of having a spinal arteriovenous shunt. Further study in a larger population is warranted to assess the accuracy of this technique.

Percutaneous transcatheter closure of atrial septal defects: initial single-centre experience and follow-up results. Initial experience with three-dimensional echocardiography.

Objective — Registry to report our single-centre experience in closing defects of the atrial septum.Methods — Between 1996 and 2001, transcatheter device closure of significant atrial septal defects was performed in 32 adults (mean age 45.1 years, range from 15 to 76 years), using different device types. Six patients had a patent foramen ovale (PFO) and 26 patients had a secundum atrial septal defect (ASD II). Defects were selected by means of two-dimensional transoesophageal echocardiography (2D TOE). For 12 defects additional three-dimensional transoesophageal echocardiography (3D TOE) was performed.Results — Mean balloon-stretched diameter was 19.3 mm (range from 11 to 24 mm). A device was successfully placed in all PFO patients (100%) without complications at follow-up. Successful immediate device placement occurred in 24 out of 26 ASD patients.Two immediate placement failures, 1 device embolisation and 1 device non-fixation, occurred and required urgent surgery. There was 1 patient with pericardial effusion after the intervention, requiring pericardiocentesis. Three late placement failures occurred: 2 device embolisations and 1 device dislocation. Clinical success after 3 to 6 months follow-up, defined as the absence of shunt or small shunt, was achieved in all 6 PFO patients and in 21 out of 23 ASD patients (1 device embolisation, requiring surgery, occurred before follow-up was completed).Two patients with significant shunt, 1 late device dislocation and 1 late device embolisation, underwent elective surgery. For patient selection, 3D TOE proved useful in the evaluation of large and/or complex defects.Conclusion — Transcatheter device closure of carefully selected atrial septal defects is an alternative to surgery. Although the results are promising, surgical back-up is often needed.

The use of xenon-133 for measurement of blood flow through systemic arteriovenous malformations before and after therapeutic embolization

Embolization is increasingly used to treat systemic arteriovenous (AV) shunts although its success, as judged by either angiographic or clinical means, is difficult to quantify. The aim of the study was to quantify blood flow through AV shunts with 133Xe, which, because of its relatively long transit time through peripheral tissues, behaves like microspheres. Following arterial injection, 133Xe entering an AV shunt rapidly arrives in the lung and can be quantified with a scintillation probe. In 17 patients with systemic AV shunts, the reduction in shunt flow following therapeutic embolization was quantified in the angiography theatre by comparing the initial count rates in the lung, recorded by probe, following injection of identical quantities of 133Xe into a supplying artery before and after embolization. By comparing the lung counts with those given by an intravenous injection of 133Xe, the fraction of flow at the catheter tip entering the shunt was also quantified. Tissue perfusion in the vascular territory distal to the shunt was measured at the same time by recording the clearance of non-shunted 133Xe with a second probe over the extremity. Control injections of 133Xe were given in the contralateral limb in order to assess 133Xe transit in the absence of shunting and to compare tissue perfusion between the two sides. Shunt flow ranged from 40% to 100% (of that at the tip of the catheter) (n = 14), while the reduction in shunt flow following embolization ranged from 15% to 96% (n = 19). Tissue perfusion distal to the shunt and in the contralateral limb was about 5 ml 100 ml-1 min-1. Contrast medium had no consistent effect on tissue perfusion in either limb, or on shunt flow. There was no difference in peripheral perfusion between the abnormal and control sides, nor any significant difference in perfusion in the distal tissue on the abnormal side before and after embolization. There was, however, a consistent increase in the fraction of the injected 133Xe delivered to the distal tissue after embolization (median increase 93%, p < 0.001). The technique is relatively simple and merits further development as a means of continuous quantification of systemic AV shunt flow in the angiography theatre at the time of embolization.

Peripheral ischemia as a complicating factor during somatosensory and motor evoked potential monitoring of aortic surgery

HE incidence of paraplegia following aortic surgery is reported to vary between 2% and 25%.lm4 This reported incidence has made intraoperative spinal cord monitoring an area of interest.5-9 Two monitoring modalities, somatosensory evoked potentials (SEP) and motor evoked potentials (MEP), can detect ischemia of nervous system structures. Of these, the SEP, although controversial, is used most for both experimental and clinical monitoring of aortic aneurysm surgery.5-i0 The SEP monitors physiologic integrity of the peripheral nerve, from the site of stimulation to the cerebral cortex, via the dorsal columns of the spinal cord. The most sensitive area of the spinal cord to ischemia is the anterior horn area, as shown by the distribution of postoperative spinal cord injury.” Although some investigators have suggested that a steal of blood from the posterior to anterior spinal cord may occur during aortic cross-clamping, changes in SEPs will, at best, indirectly monitor ischemia of the motor areas1*J3 Hence, SEP monitoring has yielded low specificity and sensitivity to postoperative neurologic deficits in the absence of shunt or partial bypass use during these operations.r4J5 As suggested by McNulty et a1,r3 use of these operative adjuncts, however, does in part improve the predictive value of SEP monitoring for postoperative neurologic deficits. Recent investigations have used MEPs induced by electrical stimulation to monitor spinal cord function during aortic occlusion.16-ia Monitoring MEPs may be more sensitive than SEPs to spinal cord ischemia. Clinical examples using magnetic transcranially induced MEPs in humans during aortic aneurysm surgery have yet to be reported. An often neglected factor in spinal cord monitoring is that an insult to any part of the nervous system pathway that is monitored will result in a change in the evoked potentials.19 Ischemia to the peripheral nervous system is an important factor that must be addressed during future clinical investigations involving evoked potential monitoring of aortic aneurysm surgery. Two cases are presented, one in which SEPs alone and one in which both SEPs and MEPs were monitored during aortic surgery. Both cases demonstrate the importance of peripheral ischemia as a possible explanation for changes in SEPs and/or MEPs during aortic surgery.

Magnetic resonance imaging.

<b>BACKGROUND AND PURPOSE:</b> Spinal arteriovenous shunts usually require digital subtraction angiography (DSA) for evaluation. We report a unique time-resolved spinal MR angiographic (TRSMRA) technique with a temporal resolution of 3–6 seconds and spatial resolution of approximately 1 mm³ that has the potential to noninvasively detect, localize, and follow-up these cases. <b>MATERIALS AND METHODS:</b> Eleven patients with clinical presentation and/or MR findings suspicious for a spinal arteriovenous shunt were referred for TRSMRA. Patients subsequently underwent spinal DSA to confirm the presence or absence of a shunt or were followed clinically until an alternative diagnosis was found. TRSMRA was also used to predict the level of the shunt in the positive cases. In addition, 2 of these patients as well as a 12th patient referred to us posttreatment received a follow-up TRSMRA to assess treatment outcome. <b>RESULTS:</b> Early venous shunting was identified by using TRSMRA in 6 cases. All 6 were confirmed to have an AV shunt on subsequent spinal DSA. The shunt level predicted by TRSMRA consistently correlated with DSA to within 1 vertebral level. In the 5 patients with a negative screening TRSMRA, DSA or clinical outcome confirmed the absence of an arteriovenous shunt in all of the cases. Posttreatment TRSMRA in 3 patients accurately assessed the success or failure of treatment. <b>CONCLUSION:</b> Combining acceleration techniques to achieve high frame rate TRSMRA provides sufficient temporal and spatial resolution to identify, localize, and follow patients suspected of having a spinal arteriovenous shunt. Further study in a larger population is warranted to assess the accuracy of this technique.

Systemic surgical shunts and splenomegaly as causes of haemolysis in portal hypertension in mansonic schistosomiasis: Evaluation through serum levels of haptoglobin, hemopexin and bilirubins

The haemolytic process in hepatosplenic schistosomiasis is often regarded as a result of splenomegaly that can be increased by spontaneous or surgical shunts. The importance of splenomegaly and/or shunt on the etiology of haemolysis was studied in a group of 74 patients with hepatosplenic schistosomiasis and portal hypertension. They were divided into 4 groups: Group I (22 cases) - pre-operative; Group II (15 cases) - classic splenorenal shunt; Group III (22 cases) - selective portal decompression and Group IV (15 cases) - azygoportal disconnection with splenectomy. The first group is characterized by the presence of splenomegaly and the absence of shunt; the second by the presence of shunt and absence of splenomegaly; the third, by the presence of both splenomegaly and shunt and the last by absence of both, shunt and splenomegaly. In all cases, the levels of sensitive markers of haemolysis, such as haptoglobin and hemopexin as well as non-conjugated and total bilirubins were determined. Biochemical and coagulation parameters, used to evaluate the hepatic function, were also studied. The data was initially analysed according to a factorial experiment of 2 and standard least squares techniques were used to evaluate the effects of splenomegaly, shunt and their interaction. The results showed that the shunts always provoked haemolysis, even in the absence of splenomegaly, but the presence of both, splenomegaly and shunt, always increased the process of haemolysis.

Inert gas elimination studies without mixed venous partial pressures

In theoretical studies of steady state inert gas elimination in parallel ventilation and perfusion lung models with intravenous administration of dissolved test gas, the ratio of arterial partial pressure to expired partial pressure when known for a range of solubilities gives valuable information, which includes the fraction of total ventilation going to unperfused areas, the presence or absence of shunt and the number of compartments. If the total ventilation to total perfusion ratio ( V ̇ T Q ̇ T ) is known, the test is equivalent to a retention-solubility study. Simple procedures exist for giving the distribution of fractional perfusions over the ventilation-perfusion ( V ̇ A Q ̇ ) scale as a function of V ̇ T Q ̇ T . The fractional shunt is expressed as a simple function of V ̇ T Q ̇ T .

Paradoxical motion of the interventricular septum with right ventricular dilatation in the absence of shunting: Report of two cases

A history, heart murmur, electrocardiogram and chest X-ray film suggesting an atrial septal defect associated with an echocardiogram revealing paradoxical motion of the interventricular septum with a dilated right ventricle may be considered indicative of a secundum or primum defect in a young adult or child. Two patients who fulfill all these criteria and had the presumptive diagnosis of an atrial septal defect were found at cardiac catheterization to have no demonstrable left to right shunt or other significant abnormality. The results of standard T-M mode echocardiograms were verified with B scan ultrasonograms. These cases may represent an early stage in the development of a cardiomyopathy. There is no echocardiogram pathognomonic of an atrial septal defect, and patients whose history and echocardiogram suggest this defect should have further diagnostic evaluation including technetium scan or cardiac catheterization.

Breathing pattern effects on pulmonary oxygen uptake

Pulmonary oxygen uptake has been analysed to determine the relative importance of breathing pattern parameters. Computer simulations of pulmonary oxygen transport were obtained with a multicompartment model of the lung, assuming an absence of shunts, constant cardiac output, and 21% inspired oxygen. Simulations of oxygen uptake in the lung for various breathing patterns showed that the parameters having the greatest effect on the arterial PO2 are the tidal volume and breathing rate. At a constant tidal volume and breathing rate, that is a constant total ventilation, even extreme variations in the shape of the flow pattern produce relatively small changes in arterial Po2. At a given inspired oxygen concentration, optimal strategies to provide sufficient gas exchange with mechanically aided ventilation in the absence of significant oedema or aetelectasis can be based primarily on changes in tidal volume and breathing rates.

SUGA, HIROSHI

In the detection of shunt and regurgitation in cardiac diseases or in the measurement of cardiac output by dye dilution method, an intuitive interpretation of the shape of obtained curves is unavoidable. Therefore, 'the results obtained are not always accurate. Especially, the curves recorded through ear piece after injection of the dye into the peripheral veins are sometimes equivocal and less accurate than those obtained by injection of dye in the large central vessels, although the former procedure is much simple and does not inflict much discomfort to the patients. Accordingly, it would be very advantageous for us to develop a means for deriving the useful information sufficient for clinical diagnosis from the curves obtained by the former method. In this respect, the writer has developed a method, in which the dye dilution curves recorded through ear piece is measured automatically and the presence or absence of shunt or regurgitation is determined by a computer. Calculation of cardiac output is, of course, included in the procedure. The dye dilution curves, which were used for the present study, were recorded by the Cam-bridge's Dye Dilution Curve Recorder using an ear piece. The employed dye was Coomassie blue, 40 mg of which was injected into the antecubital vein. In recording the dye dilution curve, generally to, ti, tp, tL, tr, td, cp, ct, cr and the terminal concentration (Et) have 'been measured hitherto. In writer's experience, however, the ascending and descending limbs also show outstanding characteristic in some of the diseases. Accordingly, the maximum slope of the ascending limb (maxS1) and its average slope (meanS1) during the period of 3 sec. (1.5 sec. before and 1.5 sec. after the point of the maximum slope), the maximum slope of the descending limb (maxS2) and its average slope (meanS2) were added to measuring items. When shunt or regurgitation exists, the calculation of td becomes inaccurate, so that the point (td, ) where meanS2 intersects the baseline was used in place of td, A ratio of Cp/Et was also added. Thus, a total of 19 items were used. The dye dilution curve was digitized by A-D converter at a sampling rate of 6 per second. The curves, which had been recorded on the sheets previously, were put in the tape recorder using a pencil follower, then delivered also to an A-D converter.

MEASUREMENTS OF EFFECTIVE PULMONARY BLOOD FLOW IN THE NORMAL NEWBORN HUMAN INFANT

Effective pulmonary blood flow was measured in 32 normal infants by an indicator gas technique. To check the accuracy of this technique in the absence of shunts, we obtained 39 pairs of measurements of pulmonary blood flow in anesthetized rabbits by the gas technique and dye dilution. The results showed a high degree of correlation between the two methods of measurement (r = 0.986). Effective pulmonary blood flow was 1.1% less than total pulmonary flow (p &amp;lt; 0.005); this difference was attributed to venoarterial shunting through non- ventilated parts of the lung. Measurements of effective pulmonary blood flow in normal newborn infants increased with age. Before 24 hours of age, mean effective pulmonary flow averaged 138 ml/min/kg or less and gradually rose to a mean value of 166 ml/min/kg (±25.6 SE) at a mean age of 81 hours. It is possible that our measurements of effective pulmonary blood flow before 24 hours of age were falsely low because of the presence of clinically undetectable left-to-right shunts.

Hemodynamic findings in normal children.

Extract: We have studied cardiac function and dynamics in 29 apparently normal children under 20 years of age. Table I lists the values obtained for intracardiac and great vessel pressures. There was no correlation of these pressures with either age or increasing body size. Except for the possibility that our data is inadequate for patients under one week of age, these pressures as well as the ratio between pulmonary artery mean to systemic artery mean (fig. 1), appear to be constant throughout the pediatric age range. Arterio-venous differences ranged from 28 to 78 ml of O2/l of blood. The mean was 44.3 ml/l with a S.D. of 15.0. Left ventricular cavity diameters are shown for 11 normal children from our series and 9 patients from the literature (fig.4). The two measurements recorded in the youngest subjects are elevated, probably as a result of our inability to distinguish that area of left ventricular ‘wall’ occupied by the thymus. The ratio of the left ventricular cavity diameter to wall thickness was 7.0 (fig. 5). Calculated systemic, total pulmonary and pulmonary arteriolar resistances appeared to be inversely related to age, height, and weight. Therefore, it seemed that non-linear regression formulae employing the inverse of age, height and weight would be more suitable (table III). Height alone gave the best correlation with all cardiac functions except output. Calculated resistances for both systemic and pulmonary circulations fall with increasing age at approximately the same rate (figs. 6-8). As systemic blood flow increases to accommodate the needs of increasing body size, the denominator of the DC resistance term increases and ‘resistance’ decreases. Since in the absence of shunts, pulmonary blood flow must parallel the increase in systemic blood flow, pulmonary ‘resistance’ decreases pari passu. Speculation: High speed digital computers now make the development of regression equations increasingly simple. These equations will be increasingly employed by clinical investigators in place of ‘surface area’. It is also obvious that calculated ‘resistances’ tell us far less about the vascular bed than was formerly believed. Input impedance calculation will be employed in the future, particularly as better methods for measuring instantaneous flow become available.

PHONOCARDIOGRAPHIC STUDIES BEFORE AND AFTER CARDIAC SURGERY: ATRIAL SEPTAL DEFECT, VENTRICULAR SEPTAL DEFECT AND MITRAL STENOSIS

Phonocardiographic studies were undertaken on the patients with congenital and acquired heart diseases before and after cardiac surgery in hope that follow-up studies on the changes in heart sounds and murmurs might reflect the effect of surgery and normalization of cardiopulmonary function. Materials and Methods Twenty cases of atrial septal defect (ASD), 29 cases of ventricular septal defect (VSD), and 10 case of mitral stenosis (MS) were subjected to this study. Phonocardiograms were also taken in sixteen cases of normal individuals in order to obtain normal values (Table 1). A multifilter system phonocardiograph and microphone of dynamic type* were used. Phonocardiograms were taken at a speed of 100 mm per second together with electrocardiograms. Responses of cardiac murmurs to amyl nitrite and phenylephrine were analyzed to differentiate the origin of murmurs before and after surgery. Right heart catheterization was performed before surgery in all cases and was repaeted one month after surgery in 10 cases of ASD, 10 cases of VSD and 8 cases of MS. Results 1. ASD Postoperative right heart catheterization study showed normal RV and PA pressure and absence of shunt in 8 cases out of 10, and per sisting elevation of RV and PA pressure with a residual shunt in the remaining 2 cases (Fig. 6). Q-I interval was slightly prolonged preoperatively and it returned to normal range within 1 month after operation. Two case with a residual shunt, however, still showed prolongation even 6 months after operation (Fig. 1). Apical first sound was accentuated in 16 cases before operation. Accentuation persisted, though in a decreased intensity, in 5 cases 1 month after operation, and in 3 cases 6 months after operation. The cases with a residual shunt showed a persistent increase in intensity of apical first sound (Fig. 2).