Raul Gamboa

Pulmonary hypertension in healthy men born and living at high altitudes

Abstract Right heart catheterization studies were performed in 38 healthy men 17 to 34 years of age born and living at high altitudes. In order to obtain comparative data, a similar investigation was made in 25 healthy men born and living at sea level. Previously, a physical examination was performed, and roentgenograms of the chest, hematological, electrocardiographic and vectorcardiographic data were obtained. Mild pulmonary hypertension and a moderate increase of the pulmonary vascular resistance and right ventricular work were found in men living permanently at high altitudes. Pulmonary wedge pressure, cardiac output and heart rate did not show significant differences from the data obtained at sea level. The changes occurring in the heart and pulmonary circulation in men living permanently at high altitudes are not quite comparable with the changes described in temporary residents at high altitudes, nor with those experimentally obtained by acute hypoxia. This means that when studying the effects of hypoxia upon the heart and pulmonary circulation, it is important to bear in mind not only the degree of hypoxia but also the time of exposure to it. The augmented pulmonary vascular resistance in the high altitude dweller is related to the anatomic changes in the small pulmonary arteries and arterioles which have been described by other investigators. Functional factors such as vasoconstriction, hypervolemia and polycythemia do not play an important role in the mechanism of the pulmonary hypertension at high altitudes. The role of the pulmonary hypertension in the complex mechanism of acclimatization to life at high altitude is not well understood. Apparently pulmonary hypertension would not accomplish a useful part in this mechanism. It is possible, however, that pulmonary hypetension, in association with other factors such as hyperventilation and an extensive capillary bed of the lungs, does play a role in improving the arterial oxygenation in men living at high altitude.

Pulmonary hypertension in children born and living at high altitudes

Abstract 1. 1. Thirty-two healthy children aged 1 to 14 years, born and living at high altitudes were studied by means of right heart catheterization. They lived in Morococha and Cerro de Pasco, the former at an altitude of 14,900 feet, the latter at 14,200. 2. 2. Mild pulmonary hypertension and an increased pulmonary vascular resistance have been found in children born and living in high altitudes. Values of cardiac output and pulmonary wedge pressure were similar to those reported at sea level. The increased pulmonary vascular resistance is ascribed to structural changes reported by other investigators in the small pulmonary arteries and arterioles. 3. 3. Pulmonary hypertension is greater in children than in adults of high altitudes, and it is greater in children under 5 years of age than in those 6 to 14. In the younger group pulmonary pressures are similar to those obtained in newborns at sea level. This signifies that at high altitudes there is a delay in the evolution of the pulmonary pressures with aging, in contrast to what occurs at sea level. This slow evolution agrees with the slow regression of right ventricular hypertrophy at high altitudes as demonstrated by anatomic, electrocardiographic and vectorcardiographic studies. 4. 4. The pulmonary hypertension found at high altitudes could be considered to a certain extent as a form of primary pulmonary hypertension; however, basic differences are pointed out between both conditions. The role of pulmonary hypertension in the high incidence of patent ductus arteriosus at high altitudes is discussed.

Effect of Chronically Increased Ventricular Pressure on Electrical Forces of the Heart A Correlation between Hemodynamic and Vectorcardiographic Data (Frank System) in 90 Patients with Aortic or Pulmonic Stenosis

Hemodynamic measurements during left and right heart catheterization in 90 patients with aortic or pulmonic stenosis have been correlated with selected vectorcardiographic parameters obtained by the Frank vectorcardiogram.Evidence has been presented that increased left ventricular peak pressure (r=0.85) or pressure time (r=0.78) leads to augmentedmaximum spatial voltages. The coefficients for similar correlations on the right side of the heart were 0.87, respectively 0.82. When a sum of selected spatial vectors was used the correlation coefficient with left ventricular peak pressure rose to 0.90 (with controls r=0.93) and with right ventricular peak pressure to 0.89, while at the same time the standard error became less. Less significant correlations existed with the log of the valve area (r=−0.69 for the aortic valve and r=−0.66 for the pulmonary valve) and stroke work (r= 0.24 for left and r=0.32 for right ventricular work).These findings provide a further link between the morphology and the physiology of the ventricle producing wall tension and intracavitary pressure. The demonstration of no change in MSV over years of growth, while the heart increases from 20 grams to its mature weight of 300 grams and the remarkable linear increase in MSV once elevated resting pressure is produced, shows that the vectorcardiogram is capable of reflecting accurately the average peak pressure and pressure time delivered by either ventricle. Furthermore, the less significant relationship with stroke work or valve area, in the face of the good correlation with pressure time per minute and peak pressure, in particular, indicates that chronically increased ventricular pressure in obstructive lesions is the chief factor altering MSV. On the basis of Linzbachs histologic studies, it appears that the essential measurement made by the MSV or the SMSV is the number of cells constituting the actively contracting myocardial syncytium required for the maintenance of average resting ventricular systolic pressure.

Pulmonary Pressure, Cardiac Output, and Arterial Oxygen Saturation during Exercise at High Altitude and at Sea Level

The response elicited by exercise on pulmonary pressure, cardiac output, and arterial oxygen saturation in 35 lifetime residents of high altitude has been studied at high altitude (14,900 feet above sea level), and 22 residents of low altitude have been studied at sea level. A procedure combining cardiac catheterization, arterial cannulation, and spirometry was carried out. The exercise was moderate and was performed in supine position using a bicycle ergometer, the work load being 300 kg-m/min/m,2 and the average increase of the oxygen uptake being 4.7 times at sea level and 4.8 times at high altitude.Both at sea level and at high altitude the cardiac output augmented during exercise proportionally to the increase in oxygen uptake, and thus followed the pattern of response described by other authors. The cardiac output as well as the oxygen intake, for the magnitude of exertion performed in this study, was almost the same at sea level and at high altitude. The cardiac output rose during exercise almost exclusively as a result of an increase in the heart rate, with the stroke volume remaining practically constant.Despite similar increase in cardiac output, the response of pulmonary pressure was smaller for sea-level subjects than for the high-altitude subjects. Increments of mean pulmonary pressure of nearly 50% and 100% were observed on exercise at sea level and at high altitude, respectively.During exercise the arterial oxygen saturation did not change in the sea-level studies, but decreased significantly in the high-altitude studies. The decrement observed in high-altitude residents is related to a fall in arterial pO2 which at resting conditions is placed on the steep part of the oxygen dissociation curve.

Anomalous Left Coronary Artery Originating from the Pulmonary Artery Report of Two Surgically Treated Cases with a Proposal of Hemodynamic and Therapeutic Classification

Case histories of two infants with anomalous origin of the left coronary artery from the pulmonary artery are presented.Both infants underwent ligation of the left coronary artery at its entrance into the pulmonary artery. One survived the operation and is asymptomatic 3 years postoperatively, whereas the second one died at surgery.A classification of instances of anomalous left coronary artery according to adequacy of the collateral circulation between the left and right coronary systems is proposed.Surgical ligation of the pulmonary artery orifice of the left coronary artery is indicated only if the presence of a left-to-right shunt into the pulmonary artery is demonstrated.If the direction of blood flow is from pulmonary artery to left coronary artery, surgical procedures should be aimed toward increasing either pulmonary artery oxygen content or left coronary artery perfusion pressure.

THE INFLUENCE OF HIGH ALTITUDES ON THE ELECTRICAL ACTIVITY OF THE HEART. ELECTROCARDIOGRAPHIC AND VECTORCARDIOGRAPHIC OBSERVATIONS IN ADOLESCENCE AND ADULTHOOD

Abstract 1. 1. Electrocardiographic and vectorcardiographic observations were obtained in 550 normal subjects, 300 at sea level and 250 in Morococha, 14,900 feet above sea level. A comparative study was made in three age groups: the age range was 15 to 60 years. 2. 2. The ventricular activation process shows significant differences between the two places studied. In adolescent and adult inhabitants of high altitudes there is a wide range in SÂQRS direction, the configuration of the QRS complex is highly variable both in the limb and precordial leads, and the two-dimensional projections of the spatial QRS loop show wide diversity. 3. 3. Five principal QRS patterns are described according to the spatial SÂQRS orientation. These patterns do not represent different types of ventricular activation. They are varieties of a peculiar activation process which exhibits two principal characteristics: a delay in the pattern of development of the QRS changes that normally occur with aging, and an increasing magnitude of the terminal QRS vectors. 4. 4. The most common pattern in adults of high altitudes shows SÂQRS in the right inferior posterior octant, an rS complex in Lead V 1 , and S 1 -Q 2 -Q 3 or S 1 -S 2 -Q 3 patterns in extremity leads. The S 1 -S 2 -S 3 pattern is also observed, and it is related to predominant late QRS vectors and not to a special cardiac position. Predominantly positive QRS complexes in Lead V 1 are infrequent in adults of high altitudes. The r′-V 1 pattern seen in some subjects who live at high altitudes probably represents a transitional stage in the pattern of development of QRS throughout life. 5. 5. In adults at high altitudes, right ventricular preponderance is less than in children at the same altitudes, but the physiologic preponderance of the left ventricle seen at sea level does not occur even in the older adults. The moderate right ventricular hypertrophy of high altitudes is probably related to anatomic and functional changes that take place in the pulmonary circulation as a consequence of the process of acclimatization. 6. 6. The electrocardiographic and vectorcardiographic characteristics of the adolescents and adults who live permanently at high altitudes are not similar to those of normal adolescents and adults who live at sea level. Therefore, a high-altitude environment is an important cause of electrocardiographic and vectorcardiographic variability in healthy people.

Accuracy of the Phonocardiogram in Assessing Severity of Aortic and Pulmonic Stenosis

A critical evaluation was made of the reliability of three easily obtainable phonocardiographic criteria in the estimation of ventricular peak pressure in congenital pulmonic and aortic valvular stenosis.In 50 patients with pulmonic stenosis the Q-ejection click interval showed a significant inverse relationship to peak pressure (r=−0.77, p<0.001), while no significant relationship existed in aortic stenosis (r = 0.40, p<0.5). The timing of the peak magnitude of the murmur again related significantly to the right ventricular pressure (r = 0.72, p < 0.001) and with the log of pulmonary valve area (r=−0.72, p <0.001). In contrast no significant relationships existed in aortic stenosis. The degree of splitting also reflected the severity of right ventricular hypertension (r = 0.84, p <0.001), while this measurement in aortic stenosis proved quite variable and did not reflect ventricular peak pressure.The significance of a combination of these criteria in predicting the severity of right ventricular hypertension and in obviating the need for cardiac catheterization is stressed.An explanation for the mechanism underlying the observed changes is given. Q-ejection click interval in particular constitutes an indirect but sensitive way (r =−0.90, p< 0.001) of estimating the rate of pressure development (dp/dt) in the hypertrophied right ventricle.

Experimental right bundle branch block in the normal human heart. Electrocardiographic, vectorcardiographic and hemodynamic observations.

Abstract 1. 1. Right bundle branch block was experimentally produced in twenty normal subjects by applying pressure on the right ventricular septal surface with an electrode-catheter. Electrocardiographic, vectorcardiographic and hemodynamic observations were performed in varying degrees of right bundle branch block obtained in this way. 2. 2. The results of these experimental studies in man are in agreement with the current criteria for the diagnosis of right bundle branch block of advanced degree (complete right bundle branch block), but new and valuable information has been obtained concerning the minor degrees of right bundle branch block (incomplete right bundle branch block). 3. 3. Morphologic changes are more important than quantitative data for the electrocardiographic and vectorcardiographic diagnosis of incomplete right bundle branch block. A QRS duration of only 0.07 or 0.08 second can be associated with minor degrees of right bundle branch block. Slowing of the QRSsE loop is not always present in these cases, and the relationship between electrical and mechanical systole remains frequently within normal variations. 4. 4. Right bundle branch block of advanced and minor degrees is an experimental reality in human beings. On the other hand, the remarkable similarity between the experimental and clinical findings constitutes a valuable support of the hypothesis which explains the complete and incomplete right bundle branch block patterns, seen frequently in clinical practice, by right bundle branch involvement. However, it does not mean that a late R wave in the right precordial leads results always from this mechanism. 5. 5. A surprising similarity is noted when the electrocardiographic and vectorcardiographic changes developing during the regression from experimental right bundle branch block are compared with those observed following surgical repair of atrial septal defects with mild pulmonary hypertension or without pulmonary hypertension. It is believed that right bundle branch block in regression could be an electrogenic factor in these postoperative changes.

The Electrocardiogram in Tricuspid Atresia and Pulmonary Atresia with Intact Ventricular Septum

Electrocardiograms were studied in 37 patients with tricuspid atresia and in 20 with pulmonary atresia and intact ventricular septum. The results were correlated with angiocardiographic findings and postmortem examinations. Differential features were as follows:1. Biatrial hypertrophy with characteristic P “tricuspidale” was noted in 81% of the electrocardiograms in patients with tricuspid atresia, whereas this pattern was seen in only two infants with pulmonary atresia and intact ventricular septum.2. In tricuspid atresia, left axis deviation was usually directed posteriorly; however, anmal or right axis deviation was present in seven cases, six of whom were type 2C and the seventh, type 1A. In every case the horizontal QRS axis was oriented posteriorly. By contrast, in patients with pulmonary atresia there were no instances of left axis deviation in the frontal plane. Normal frontal plane axis was present in 12 patients, all of whom were type I; right axis deviation was evident in eight patients including the three infants with type II deformity. The horizontal QRS axis was usually directed posteriorly; however, anterior orientation occurred in several patients.3. A typical feature of the vectorcardiogram in patients with tricuspid atresia was the increased anterior magnitude of the initial forces followed by a sharp posterior shift. The initial forces in patients with pulmonary atresia were not characteristic.4. The electrocardiographic features in patients with tricuspid atresia and normal position of the great vessels showed decreased right ventricular potentials consistent with true hypoplasia of the right ventricle, but in patients with pulmonary atresia similar lack of right ventricular potentials could be correlated with decreased right ventricular cavity, whereas the ventricular wall was actually hypertrophied.

The role of the right and left ventricles in the ventricular pre-excitation (WPW) syndrome: An experimental study in man

Abstract In three patients with Wolff-Parkinson-White syndrome, right bundle branch block was induced during right cardiac catheterization. Electrocardiograms and vectorcardiograms were obtained before and after the production of right bundle branch block. In cases with WPW type A it was possible to obtain simultaneous features of pre-excitation syndrome and an advanced degree of right bundle branch block in the electrocardiogram and vectorcardiogram. This suggests that the muscular segment prematurely activated is located in the left ventricle and that the right bundle branch block delays the right ventricular activation. Right bundle branch block did not modify the end of the ventricular activation in the case with WPW type B. It is postulated that in this type of WPW syndrome the pre-excitation takes place in the right ventricle, and therefore depolarization of this ventricle is mainly dependent on the pre-excitation phenomenon. The different topographic situations of the pre-excitation area, as has been shown by the experimental production of right bundle branch block, are in agreement with the characteristic features of the two varieties of WPW syndrome.