Hg Gradient Research Articles

Value of multiple echocardiographic views in the evaluation of aortic stenosis in adults by continuous-wave Doppler

Fifty-two adults referred for evaluation of aortic stenosis (AS) were studied using continuous-wave and pulsed Doppler echocardiography. Three windows were used to determine which approach (apical, right parasternal or suprasternal) yielded optimal results. Doppler-derived peak aortic valve gradients were compared with the peak gradients measured at cardiac catheterization in 23 patients. High-velocity jets were best recorded from the cardiac apex and less frequently from the right parasternal and suprasternal areas. However, gradients from the right parasternal area correlated best with cardiac catheterization findings, although recordings could be made from this window in only 49% of the patients. Velocities from the suprasternal window were significantly (p < 0.01) lower than those from the apex or right parasternal areas. Gradient underestimation from the suprasternal window tended to increase with age of the patient (p < 0.1). When the maximal Doppler derived gradient from any window was compared with catheterization measurements, the correlation coefficient was 0.86. Gradients derived from Doppler velocities accurately predicted severe (more than 50 mm Hg) gradients at catheterization. Thus, Doppler echocardiography is useful in evaluation of AS when several windows are used for optimal assessment of aortic valve gradient.

The role of the Glenn shunt in patients undergoing the Fontan operation

Twenty-seven patients (3 to 22 years) underwent the Fontan operation. Seventeen had tricuspid atresia and 10 had other complex lesions. Sixteen patients had a Glenn shunt (12 prior to, three simultaneous with, and one following the Fontan operation). One early death (3.7%) occurred in a 4 1/2-year-old child with tricuspid atresia II-C, previous pulmonary artery banding, and a closing ventricular septal defect (80 mm Hg gradient). There were two late deaths (7.4%) from Candida sepsis, after 4 and 6 months, respectively. The 24 patients who survived the Fontan operation had postoperative hospital stays of 6 to 90 days (average 18). Patients with tricuspid atresia and an established Glenn shunt (nine patients, Group I) had postoperative hospital stays of 7 to 19 days (average 9.5), and none had significant pleural or pericardial effusions. Patients with tricuspid atresia without a Glenn shunt (seven patients, Group II) had postoperative hospital stays of 6 to 60 days (average 17.5), with three having significant effusions. Of the patients with other complex lesions, all without an established Glenn shunt, five had significant effusions. Four additional major complications (two tricuspid patch disruptions with ineffective pulmonary blood flow and two complete occlusions of a valved conduit) were encountered in which the Glenn shunt proved lifesaving. We believe that an established Glenn shunt played a major role in attaining minimal postoperative hemodynamic instability, effusions, renal failure, and mortality in our patients. The Glenn shunt should be considered in patients who are less than ideal candidates for the Fontan operation.

Tandem coarctation of the thoracic aorta: An unusual congenital anomaly

The coarctation involving the aortic isthmus, with hypoplasia of the upper aortic segment, was satisfactorily repaired in a 15-year-old girl. The technique used was subclavian flap arterioplasty followed by reimplantation of the distal subclavian artery into the left carotid artery. Suprisingly weak femoral pulses were noted postoperatively and prompted a control angiogram. This showed an intraluminal diaphragm 2 cm below the site of the previous repair, with a 100 mm Hg gradient. At reoperation, a centrally performed fibrous diaphragm was excised, and the aorta was enlarged with a small Dacron patch. The postoperative course was uneventful.

Septal Aneurysm and Right Ventricular Obstruction: A Case Report

A 32-year-old man with a history of ventricular septal defect presented with systolic and diastolic murmurs and vectocardiographic evidence of right ventricular hypertrophy. Echocardiography demonstrated a prominent systolic bulging of the interventricular septum into the right ventricle. Left ventricular angiograms indicated that the ultrasonic abnormality was based on an aneurysm of the membranous septum which produced a 35 mm Hg gradient within the right ventricle. After plication of this aneurysm, murmur and abnormal septal protrusion were not recorded.

Artifacts in the measurement of pulmonary artery wedge pressure.

Pulmonary artery wedge pressure (PAWP) will only reflect left atrial pressure (LAP) if continuity of fluid exists from the catheter tip to the left atrium. Either increased airway pressure or decreased hydrostatic pressure may lead to discontinuity of the fluid column and midinterpretation of PAWP. Simultaneous measurements of PAWP and LAP were made in 19 anesthetized dogs. Placement of the pulmonary artery wedge catheter above the left atrium (West Zone I) in combination with the incremental addition of 5 cm H2O of PEEP caused a 5 mm Hg gradient between PAWP and LAP in the normovolemic animal. Augmenting PEEP further or hypovolemia (i.e., decrease in LAP) increased the gradient. Hypervolemia (increase in LAP) diminished the gradient. Fluid continuity between the PAW catheter and LA is a prerequisite for monitoring LAP with the Swan-Ganz catheter. Increases in PEEP, placement of the catheter above the left atrium and hypovolemia may occlude the fluid column and cause artifacts in the PAWP obtained.

Extraanatomical Bypass of the Aortic Root: An Experimental Technique

Endocarditis involving a prosthetic aortic valve is associated with persistently positive blood cultures and aortic regurgitation. With rare exception, it is a fatal disease. An experimental technique was developed that would allow for removal of the infected aortic prosthesis with debridement and permanent closure of the aortic root. An extraanatomical outflow for the left ventricle was created using a valve-containing conduit between the apex of the left ventricle and the descending thoracic aorta (apicoaortic anastomosis). The procedure was performed on 5 mongrel dogs through a left thoracotomy without use of cardiopulmonary bypass. Four survived the procedure and required no cardiotonic support. One died as a result of a technical problem. Intraoperative pressure determination revealed a 0 to 15 mm Hg gradient across the apicoaortic prosthesis and a left ventricular enddiastolic pressure of 0 to 4 mm Hg. Both postoperative angiocardiogram and postmortem examination confirmed patency of the aortocoronary bypass grafts and good function of the prosthesis.

Experience with Valved Conduits for Repair of Congenital Cardiac Lesions

Dacron valved conduits or aortic allografts were placed between the right heart and the pulmonary artery for repair of various complex congenital cardiac anomalies in 56 patients (aged 15 days to 33 years; median, 11 years). Forty-four patients had a total of 56 previous palliative procedures, which contributed to postoperative morbidity and mortality. Six patients had a total of seven episodes of early or late sepsis involving the conduit. One patient, treated for early sepsis, again developed infection in the Hancock graft 1 year postoperatively and died. Three other patients, 2 with calcified allografts, developed infections 4 months to 7 years following repair and required graft replacement. Hemodynamic data 1 month to 5 years (mean, 1.6 years) following repair revealed mild to moderate obstruction (< 45 mm Hg gradient) at the Hancock conduit valve ring in 13 of 19 patients, while 5 had large pressure gradients (> 75 mm Hg). All aortic allografts had severe obstruction and calcification necessitating graft replacement. It is anticipated that improved technique and appropriate timing of palliative and corrective operations will substantially reduce or eliminate these problems.

Pulmonary valve cyst in an adult: Case report

A case is described of an asymptomatic woman who had typical findings of mild pulmonic stenosis. Right heart catheterization revealed a 44 mm. Hg gradient across the pulmonary outflow tract, and a filling defect was discovered by angiography. On surgical exploration, the defect was found to be a benign cyst attached to the anterior leaflet of the pulmonary valve.

An operation for relief of severe left ventricular outflow tract obstruction

The case history of a 30-year-old man with severe mitral and aortic stenosis and slight aortic regurgitation who underwent replacement of both valves is presented. At the initial surgical procedure, because of the small-size annuli, a small Beall mitral prosthesis and a No. 19 Björk-Shiley aortic prosthesis were used. The subsequent recurrence of severe symptoms and findings of an 80 mm. Hg gradient across the Björk-Shiley aortic valve led to repeat exploration and corrective surgery. The operative procedure to relieve left ventricular outflow obstruction is described. It is felt that this procedure can be used not only for the relief of severe aortic annular stenosis but also for other forms of severe left ventricular outflow tract obstruction such as idiopathic hypertrophic subaortic stenosis and particularly in the patients who have experienced poor results with one of the known surgical procedures for this clinical entity.

Treadmill Exercise Test in Aortic Stenosis and Mitral Stenosis

The incidence of positive submaximal treadmill exercise tests was evaluated in patients with mitral stenosis and aortic stenosis, no electrocardiographic evidence of left ventricular hypertrophy, and normal coronary arteries on angiography. Seven of 19 patients (37 percent) with aortic stenosis (53 to 80 mm Hg gradient across the aortic valve) had greater than or equal to 1.0 mm of ischemic S-T segment depression during or after a submaximal treadmill test. Three of 15 patients (20 percent) with mitral stenosis (11 to 22 mm Hg mean gradient across the mitral valve) had greater than or equal to 1.0 mm of ischemic S-T segment depression during or after a submaximal treadmill exercise test. Patients with significant valvular disease, no electrocardiographic evidence of left ventricular hypertrophy, and normal coronary arteries may have a positive submaximal treadmill exercise test due to an unfavorable balance between myocardial oxygen supply and myocardial oxygen demand.

Repair of coarctation of the thoracic aorta by patch graft aortoplasty

Patch graft aortoplasty, rather than resection of the coarctation segment plus end-to-end anastomosis, was utilized in 70 patients ranging from 2 days to 65 years in age. Associated defects were present in 84 per cent of the patients under the age of 2 years (Group I) and in 50 per cent of the patients ages 2 to 65 years (Group II). The mortality rate in Group I was 26 per cent. All 5 patients who died were under the age of 2 months, had severe pulmonary hypertension from associated cardiac defects, and died within 4 days after the operation. None of the patients between 2 months and 2 years of age died. In Group II the mortality rate was 4 per cent. Both patients who died had severe associated defects; no patient with simple coarctation died. In Group II, associated cardiac defects were concomitantly repaired with patch graft aortoplasty. There was no evidence of recurrence in the follow-up period up to 12 years following surgery, but in 1 patient there was a 20 mm. Hg gradient across the repair. One technical aspect essential for successful repair is the fashioning of a patch large enough so that the proximal and distal portions of the patch along with the coarcted segment do not result in subsequent obstruction. The advantages of avoiding a circular constricting anastomosis, retaining the posterior wall for further growth potential, and eliminating suture line tension are essential in repair of coarctation in infants. Lack of hemorrhage problems, adaptability to long coarcted segments, and the small degree of mobilization of the aorta required are other definitive advantages. The technique is recommended for more widespread usage and for routine repair of coarctation of the thoracic aorta.

Development of subaortic stenosis after pulmonary artery banding.

Palliation of children with large ventricular septal defects (VSD) by pulmonary artery banding (PAB) is associated with a variety of unfavorable sequelae. We document another possible complication of PAB, the development of subaortic stenosis, which occurred in 4 of 40 infants with large VSD and PAB. Prior to surgery all had congestive heart failure, cardiomegaly, pulmonary plethora, and biventricular or right ventricular hypertrophy on electrocardiogram. At cardiac catheterization all had large VSD with pulmonary artery hypertension. No gradient between left ventricle and systemic artery was demonstrated. PAB was followed by improvement in all four children. Repeat catheterization at 4 to 11 years of age revealed that they had developed a significant (30 to 100 mm Hg) gradient across the left ventricular outflow tract. Although the etiology of the subaortic stenosis is not known, it is felt that the hypertrophied and possibly leftward deviated conal septum was impinging on the left ventricular outflow tract in three of the four. Since the subaortic stenosis was not suspected prior to the second catheterization, we feel that preoperative evaluation of children with VSD and PAB should include evaluation of the left ventricular outflow tract to be certain that no obstruction is present.

Myocardial blood flow in man: effects of coronary collateral circulation and coronary artery bypass surgery.

The effects of coronary artery bypass graft (CAB) and coronary collaterals (CC) on myocardial blood flow (MBF) were studied in 24 patients undergoing 29 CAB's. MBF after CAB was compared to preexisting MBF by intraoperatively injecting (133)xenon via distal CAB with proximal CAB first occluded then open. Pressure gradients across bypassed obstructions were measured. The results were correlated with preoperative coronary arteriograms to determine the effects of CC on MBF and postobstructive perfusion pressures. Mean MBF was increased by CAB from 32+/-6 (se) ml/min per 100 g (CAB occluded) to 118+/-13 ml/min per 100 g (CAB open). The (133)Xe clearance curves with CAB open were resolved into slow (19+/-2 ml/min per 100 g) and rapid (133+/-12 ml/min per 100 g) phases, suggesting that MBF remained heterogeneous after CAB. Vessels with less than 80% stenosis by angiography had pressure gradients less than 20 mm Hg across obstructions, high postobstructive perfusion pressures (75+/-7 mm Hg), and normal MBF (87+/-6 ml/min per 100 g) even with CAB occluded. Vessels with greater than 80% stenosis or total occlusion by angiography had significant pressure gradients with marked reduction of postobstructive MBF. No significant difference in postobstructive MBF was found when vessels with CC (21+/-4 ml/min per 100 g) were compared to those without CC (17+/-4 ml/min per 100 g) (P > 0.4). These studies demonstrate that (a) mean MBF increased 268% after CAB, (b) heterogeneous MBF persisted after CAB, (c) CC were not associated with significant increases in MBF, and (d) vessels with less than 80% stenosis had less than 20 mm Hg gradient with minimal effect on resting MBF.

Angiographic and catheterization findings in patients with difficulties after total correction of tetralogy of Fallot.

Tetralogy of fallot is an anatomically complex intracardiac defect resulting in right-to-left or bidirectional shunts at the ventricular level and decreased pulmonary blood flow. The peripheral arterial unsaturation varies with the size of the interventricular defect and its anatomic relationship to the enlarged aortic root, as well as with the severity of the right ventricular outflow obstruction. The muscular hypertrophy of the right ventricle may be pronounced. Total repair of the anomaly achieves physiologic correction by separation of the intracardiac streams and by relief of the pulmonic stenosis. The repair may or may not result in perfect anatomic or entirely normal intracardiac pressure relationships. Of 124 patients operated upon, there were 102 long-term survivors in this series. Twelve of these were restudied by cardiac catheterization and angiocardiography performed from two months to ten years after total correction of the defects. The most common indication for re-examination was the presence of a loud systolic murmur over the pulmonary area suggesting significant residual pulmonary stenosis. Other indications were a loud diastolic murmur or parasternal systolic murmur, cardiac enlargement and failure, a bulge along the left upper cardiac border on the chest roentgenogram suggestive of right ventricular outflow tract aneurysm, and electrocardiographic evidence of increasing right ventricular hypertrophy. Table I summarizes the catheterization and angiographic findings in these patients as well as their subsequent course. Three have had repeat operations with good results. Examples of the lesions found in seven patients are described in the following brief case reports and illustrated in the accompanying figures. Case Reports Case I (N. R): The diagnosis of tetralogy of Fallot was established in this boy at three years of age. Preoperatively a bidirectional shunt was found at the ventricular level. No atrial septal defect was diagnosed. The right ventricular systolic pressure was 88 mm Hg, and there was a 76 mm Hg gradient across the pulmonary valve. One of the views from the lateral angiocardiogram is shown in Figure 1, A. At operation, a moderate amount of infundibular stenosis was encountered and resection was done. The stenosed pulmonary valve was opened by incising two of the commissures, and the ventricular septal defect was closed with a Teflon patch. After surgery, digitalization was necessary because of congestive heart failure, and systolic and diastolic murmurs persisted over the pulmonic area. The electrocardiogram revealed complete right bundle branch block. The child was recatheterized at five years of age because of the persistent murmurs and cardiac failure. At this time the systolic right ventricular pressure was 110 mm Hg in the inflow tract.

A case of valvular and supravalvular aortic stenosis and coarctation of the aorta

A case of valvular aortic stenosis, supravalvular aortic stenosis and coarctation of the aorta is presented. The patient, a 17 year old girl, presented with easy fatigability, occasional frontal headaches and vague chest pain. The prominent physical findings were a systolic ejection murmur over the base of the heart, a systolic thrill and bruit in the neck, and diminished femoral artery pulses. At cardiac catheterization there was a 36 mm. Hg pressure gradient across the aortic valve, a 20 mm. Hg gradient across the supravalvular obstruction and a 10 mm. Hg gradient across the coarctation. The pathology and possible relation of the coarctation and supravalvular aortic stenosis are discussed.

Changes with age of the pulmonary valve area in children with pulmonary valvular stenosis

osmotic pressure was measured by osmometry. The pulmonary extravascular water volume was obtained from the difference between the volumes of dilution of T-1824 and tritiated water injected simultaneously into the pulmonary artery and sampled from the aorta; it was measured in duplicate before and at the end of the test period. The total lung water was determined at autopsy by drying. Water loss through pulmonary lymph flow was assessed by surgically obstructing right lymphatic duct drainage. At transcapillary gradients of 10.0 to 17.4 mm. Hg (8 dogs) extravascular water accumulated at an average rate of 1.0 ml. per kilogram body weight per hour per 10 mm. Hg gradient: following lymphatic obstruction (9 dogs) the filtration rate at similar gradients was 1.4 ml. per kilogram per hour per 10 mm. Hg. At gradients of 21.6 to 32.5 mm. Hg (5 dogs) lung water accumulated at an average rate of 4.1 ml. per kilogram per hour per 10 ram. Hg gradient. In these experiments obstructing the right lymphatic duct was without influence on the development of acute puhnonary edema, The difference in filtration rates at the low and high gradients suggests either that the lung developed a positive tissue pressure resisting edema formation at the low gradients, or that capillary permeability was increased at the high gradients.

The spectrum of pure mitral stenosis: Hemodynamic studies in relation to clinical disability

The pathophysiology of mitral stenosis is reassessed, with special emphasis upon relation of physiologic variables to severity of symptoms and degree of disability. Data from 44 patients with pure mitral stenosis are presented. Cathetcrization of the left side of the heart was performed in all and catheterization of the right side of the heart in 25 patients. Twenty-six patients were in Class I or II (American Heart Association Functional Classification) with mild symptoms or none at all, while 18 patients were in Class III with severe symptoms. As expected, inverse relationships existed between left atrial pressure and mitral valve area ( r = − 0.618), pulmonary arterial pressure and mitral valve area ( r = − 0.575), and between mean mitral diastolic pressure gradient and mitral valve area ( r = − 0.708). There was a positive relationship between cardiac index and mitral valve area ( r = + 0.407). All correlation coefficients were significant to the 1 per cent level. Seventeen of the 26 patients in Classes I and II had mitral valve areas of 1.5 cm 2, or less. This indicates that severe mitral stenosis can be found in a nearly asymptomatic state. All of the 18 Class III patients had valve areas of less than 1.5 cm 2. These two groups of patients with similar degree of valve narrowing were compared. Cardiac output was significantly ( p < 0.01) reduced in both categories (2.81 L. min. M 2. for Classes I and II, and 2.82 L. min. M 2. for Class in patients). Left atrial pressure in the two groups, 18 and 19 mm. Hg, respectively, and mean diastolic pressure gradient, 11 and 13 mm. Hg, respectively, did not show significant differences. However, pulmonary arterial pressure, 22 mm. Hg in Classes I and II and 36 mm. Hg in Class II, as well as pulmonary arteriolar resistance, 105 compared to 425 dynes sec. cm. −5, did allow a hemodynamic distinction between the two clinically different groups. These data suggest that the degree of pulmonary vascular disease is an important determinant of the symptoms of mitral stenosis. For Class I and II patients, history, physical examination and radiographic studies did not allow an accurate prediction of the mitral valve size. It is suggested that one of the earliest adaptive mechanisms to mitral blockade is a decrease in cardiac output and that this is not mediated, initially, through an elevated pulmonary vascular resistance, myocardial failure or atrial fibrillation. It is one of the means by which a patient with severe stenosis of the mitral valve may remain asymptomatic for prolonged periods of time.

Scientific body measurements needed

Compression stockings are commonly prescribed by physicians for lower extremity edema and venous insufficiency. However, no data are available for clinicians to assess the relative quality of various brands, particularly low-cost generics now available directly to consumers through the Internet. We examined the actual compression provided by gradient stockings from multiple manufacturers.A total of 36 class 2 (20-30 mm Hg) men's medium-sized below-knee compression stockings from six different manufacturers (n = 6 of each brand) with approximately the same quality and materials were chosen to be studied. Identifying brand names were removed, and they were randomly and blindly tested by a technician in accordance with accepted industry standards. A calibrated constant rate of extension tensile instrument (Zwick Z010; Zwick Roell, Ulm, Germany) was used, and the tension generated by the stockings at the ankle and calf was measured using minimum, average, and maximum circumference sizes. All measurements were performed in duplicate.The compression pressures generated by the stockings were almost all within the stated range of 20 to 30 mm Hg at the ankle, but all except one were below 20 mm Hg at the calf. There were also significant differences between manufacturers at both the ankle and the calf (P < .0001). The expected pressure reduction between the two locations varied, but one stocking had only a minimal 2 mm Hg (8%) gradient, which was significantly less than all of the other tested brands and below the recommended 20% to 50% reduction. Cost analysis demonstrated that the discount brands were significantly lower in price but provided absolute compression and pressure gradients similar to those of the more expensive brands.There is significant variability among stockings, both in the absolute pressures and in the pressure gradients generated from the ankle to the calf, thought to be functionally important for venous flow. The cheaper stockings offered the same degree of compression and pressure gradient as the more expensive brands. These results suggest the need for manufacturing standards in the United States and a revision in labeling requirements to mandate more accurate and complete pressure disclosures.