The P wave and P-R interval. Effects of the site of origin of atrial depolarization.

The atria of 37 patients were paced from selected sites during cardiac surgery. When the atria were paced from endocardial sites low in the right atrium, the P waves in ECG leads II, III, and aVF were shown to be either negative, biphasic, or positive, depending on the site paced. When the endocardial sites were paced, the P-R intervals were, almost without exception, less than 0.12 sec. When those endocardial sites closest to the A-V junction were paced, the P-R intervals were always less than 0.12 sec. When the atria were paced, from the epicardial sites, the P-R intervals were always greater than 0.12 sec. Negative P waves in ECG leads II, III, and aVF were recorded when the atria were paced from the postero-inferior left atrium and the caudal right atrium. The P-R interval did not always reflect the initial period of atrial activation because an isoelectric interval, generally of 0.01 to 0.025 sec, was frequently present between the onset of atrial stimulation and the first clear evidence of the P wave in the ECG. The implications of these results are discussed.

Right atrial ultrastructure in congenital heart disease. I. Comparison of ventricular septal defect and endocardial cushion defect.

Ultrastructural studies were performed on portions of the operatively resected right atrium from six patients with a ventricular septal defect and six patients with an endocardial cushion defect. The six patients with a ventricular septal defect had normal right atrial mean pressure and no evidence of right atrial volume overload. Ultrastructurally, the atrial muscle cells in these patients appeared normal and measured 6 to 12 mu in diameter. The six patients with an endocardial cushion defect had elevated right atrial mean pressure and evidence of right atrial volume overload. Ultrastructurally, the atrial muscle cells in these patients were generally larger than 12 mu in diameter. The cells were irregular and had multiple and occasionally widened intercalated discs. In addition, there were degenerative changes in two patients with markedly increased atrial pressure. These changes included extensive loss of contractile elements, aggregation of small irregular mitochondria and proliferation of tubules of the sarcoplasmic reticulum. The structural changes suggest that hypertrophy of the right atrium may be secondary to volume overload of the atrium, whereas degenerative changes may be secondary to increased right atrial pressure.

Postoperative assessment of porcine-valved right ventricular-pulmonary artery conduits.

Insertion of extracardiac right ventricular (RV)-pulmonary artery (PA) conduits for repair of severe forms of RV-PA discontinuity has become a widely used technique. During a 10-year period, 76 patients had open heart repair with a porcine-valved RV-PA external conduit. The most common diagnoses were truncus arteriosus (15%) and pulmonary atresia with ventricular septal defect (15%). The patients were 18 days to 37 years old (median 7 years). The postoperative median follow-up period was 4 years. Four patients (8%) have been lost to follow-up. Nineteen patients (25%) died in the early postoperative period and there were 10 late deaths (13%). Calculated probability of survival was 66% at 8 years. Thirty-six patients have undergone late hemodynamic studies. A residual shunt was present in 14% of the patients; moderate to severe PA hypertension was present in 25% and significant RV-PA gradients (greater than 30 mm Hg) in 50%. The mean RV pressure for the group was 78.5 +/- 38 mm Hg. The severity of the gradients appeared to be greater in patients who had been followed longer. Ten patients have undergone reoperation because of conduit obstruction or residual shunting; 6 are alive and well. Of the surviving patients, 95% are acyanotic and without significant exercise intolerance and only 5% have cardiovascular symptoms. Thus, open heart repair using an external RV-PA conduit provides a marked improvement in the quality of life in patients who survive.

Muscular ventricular septal defects repaired with left ventriculotomy.

Between 1974 and 1979 nine patients, aged 10 months to 4 years, underwent left ventriculotomy for closure of single or multiple defects in the muscular ventricular septum. The vertical incision paralleled the anterior descending branch of the left coronary artery near the apex of the left ventricle and ranged from 2.5 to 3.5 cm in length. Four patients also had a right ventriculotomy with closure of a high perimembranous ventricular defect in two. Serial electrocardiograms indicated changes of myocardial ischemia or necrosis. Left bundle branch block did not develop in any patient. Three patients died in the early postoperative period. The six surviving patients are living and well 2 to 7 years later. There is apparent complete closure of the ventricular defects, which was documented by cardiac catheterization in four cases. Two patients had cardiomegaly and left ventricular dysfunction as assessed with echocardiographic and angiographic study, whereas four displayed good cardiac function. In three of the latter patients, cardioplegia or deep hypothermia techniques were utilized intraoperatively. The observations indicate that left ventriculotomy of limited size is an acceptable approach to the difficult problem of repair of muscular ventricular defects but may involve some risk of compromise of the coronary circulation.

Mechanical assistance of the pulmonary circulation after right ventricular exclusion.

The Fontan procedure is often associated with elevated right-sided pressures and low cardiac output during the early postoperative period. A dog model was established to test the effect of pulmonary artery counterpulsation after atriopulmonary anastomosis. After exclusion of the right ventricle by a purse-string suture at the right AV orifice, placed during inflow occlusion, a valved conduit was inserted between the right atrial appendage and the pulmonary artery. This created a circulatory pattern comparable to a Fontan procedure. Counterpulsation was achieved by inserting a cannula into the conduit distal to the valve in eight dogs; alternatively, in four, counterpulsation could be achieved through a 10 mm side-arm graft connected to the conduit distal to the valve. Twenty-four observations were made. Without counterpulsation the circulatory status of the dog deteriorated rapidly. Counterpulsation resulted in a mean increase in cardiac output of 48% (p less than 0.0001). Right atrial pressure fell significantly with a mean drop of 4 mm Hg (p less than 0.003). This allowed for a further increase in right-sided filling pressure by transfusion, with a subsequent further increase in cardiac output. Left atrial pressure did not change significantly unless altered by transfusion. Counterpulsation instituted through the 10 mm side-arm graft gave similar results. Pulmonary vascular resistance decreased with counterpulsation (mean decrease 35%; p less than 0.002). The use of a side-arm graft connected to the conduit after a Fontan procedure affords a clinical method of circulatory support without the need for additional surgical intervention for decannulation. These data suggest that mechanical assistance of the failing right atrium after atriopulmonary anastomosis is both feasible and effective.

Intraoperative unidirectional intra-aortic balloon pumping in the management of left ventricular power failure.

Unidirectional intra-aortic balloon pumping (IABP) was applied to 28 adult patients undergoing open-heart surgery over a 35 month period. The patients were divided into three groups according to the temporal sequence of initiating IABP. Group A consisted of 4 patients who were in a low output state or in cardiogenic shock prior to study. All patients survived cardiac catheterization and surgery, and 3 (75 per cent) were long-term survivors. Group B included 15 patients who could not be weaned from cardiopulmonary bypass with the usual supportive measures. Twelve patients (80 per cent) were weaned from bypass with IABP, and 11 (73 per cent) were discharged from the hospital. Group C was composed of 9 patients who manifested a low cardiac output syndrome within the first 24 hours following surgery. IABP was initiated in the recovery room. Six patients (67 per cent) were discharged. The total experience with these 28 patients therefore includes 24 patients (86 per cent) who were weaned from IABP, 20 (71 per cent) who were discharged, and 18 (64 per cent) who were long-term survivors. The present criteria for the use of IABP in the cardiac surgical patient are defined.

Pharmacologic antagonism of beta-adrenergic blockade in dogs. I. Hemodynamic effects of isoproterenol, dopamine, and epinephrine in acute propranolol administration.

Hemodynamic effects of isoproterenol, dopamine, and epinephrine were studied before and after acute beta-adrenergic blockade in 16 open-chest, anesthetized mongrel dogs. Beta blockade was induced with 1 mg. per kilogram of intravenous propranolol. Cardiac output measurements were obtained by thermal dilution, and pressure recordings were obtained in the right ventricle, pulmonary artery, left atrium, left ventricle, and aorta. Derived parameters included stroke volume, pulmonary and systemic vascular resistances, and peak left ventricular dP/dt. In the presence of propranolol, epinephrine became a lethal drug in large doses and did not increase cardiac output in standard doses. Dopamine, in 25 to 50 mcg. per kilogram per minute doses, increased arterial pressure and systemic resistance; cardiac output was diminished compared with dopamine, 10 mcg. per kilogram per minute, prior to propranolol, as a result of increased resistance and decreased LV contractility. Isoproterenol, 0.6 to 0.9 mcg. per kilogram per minute, 15 to 20 times standard dosages, had moderately positive inotropic effects and increased cardiac output. Left ventricular systolic pressure with isoproterenol after propranolol was reduced when compared with effects of smaller doses prior to propranolol. These observations suggest that none of the catecholamines studied would be optimal for circulatory support in heart failure in the presence of propranolol. The present results define a pharmacologic basis for design of appropriate drug combinations for circulatory support in beta-blocked animals.

Surgical management of ventricular septal defects in infants.

Infants with ventricular septal defect (VSD) who are symptomatic despite intensive medical therapy require surgical intervention. Choice of treatment depends upon the cumulative mortality and morbidity rates of the two-stage approach of initial pulmonary artery banding followed by debanding and VSD closure as compared to the risk of primary intracardiac repair in infancy. Sixteen infants underwent pulmonary artery banding at Columbia-Presbyterian Medical Center between 1967 and 1976, with one operative death but with a significant incidence of morbidity and late death. Forty patients underwent pulmonary artery debanding and closure of VSD with three operative deaths. This second-stage procedure was frequently complicated by repair of acquired lesions. During the same 10 year period 37 infants underwent primary closure of VSD with eight operative deaths. The morbidity related to this procedure is low. With the use of profound hypothermia and circulatory arrest, results have significantly improved and the risk of early correction now compares favorably with the cumulative mortality rate of the two-stage approach. Primary intracardiac repair is the procedure of choice.

Single-stage management of sternal wound infections.

Deep median sternotomy wound infection is a significant source of morbidity after cardiac operations. Accepted approaches in treating this complication include débridement with either sternal closure over an irrigation system or open dressings and closure by secondary intention. Muscle flaps are often used in subsequent procedures for wound closure. A single-stage procedure was developed to eliminate irrigation, open wound management, or reoperation for muscle flap closure. This approach consists of débridement and immediate closure with a pectoral musculocutaneous flap. The following report describes 31 patients treated by such a method. Compared with results of previous techniques in treating sternal wound infections, hospital study is decreased, fewer reoperations are needed, and patient management is simplified.

Acute hemodynamic alterations after aortic valve replacement with the glutaraldehyde-treated porcine heterograft prosthesis.

Twenty-two patients underwent aortic valve replacement for acquired valvular heart disease with the porcine heterograft prosthesis. In the immediate postoperative period, a transient decrease in the cardiac index (CI) (preoperative 3.0 +/- 0.14 to 2.45 +/- 0.16 L. per minute per square meter, p less than 0.05) and an increase in the systemic vascular resistance (SVR) (preoperative 1,078 +/- 62 to 1,287 +/- 103) dynes/sec./cm.-5, p greater 0.05) were seen; these values returned to preoperative levels by the first postoperative day. After valve replacement, an elevation in the heart rate (HR) (preoperative 75 +/- 2 to 87 +/- 4 beats per minute, p less than 0.05) and a reduction in the stroke volume (SV) and stroke work index (SWI) (preoperative 35 +/- 2 to 26 +/- 2 Gm.-M. per square meter, p less than 0.05) occurred which persisted throughout the study. The endocardial viability ration (EVR) increased after valve replacement. These findings suggest that, following aortic valve replacement, (1) an increase HR is the mechanism utilized to maintain cardiac output, (2) subendocardial perfusion is enhanced as indicated by an increase in the EVR, and (3) the hemodynamic alterations following insertion of the porcine heterograft prosthesis are not different from those observed when other valves are placed in similar patient populations.

Signal enhancement for detection of specialized atrioventricular conduction system electrograms during open-heart surgery.

A method for signal enhancement of electrograms of the specialized atrioventricular conduction system is presented. This method allows a single electrogram to replace the tracings of bipolar electrograms previously required to ensure recognition of the specialezed conduction system and yet maintains the safety afforded by use of three pairs of recording electrodes. In addition, this new signal is enhanced in magnitude and is always unidirectional (positive). These features are desirable for automated signal recognition. This method therefore provides an important step toward future automation and signal recognition of specialized conduction system electrograms during open-heart surgery.

Pharmacologic antagonism of propranolol in dogs. III. Effects of dopamine-isoproterenol and glucagon on hemodynamics and myocardial oxygen consumption in ischemic hearts during chronic propranolol administration.

In 31 dogs chronically beta blocked with oral propranolol (12 to 14 mg/kg/day), glucagon (20 micrograms/kg) and combined dopamine (10 micrograms/kg/min) and isoproterenol (0.2 micrograms/kg/min) were given intravenously and tested for hemodynamic efficacy. Dogs were divided into four groups. Basal hemodynamics were obtained In Group I (n = 8) without cardiopulmonary bypass. In Group II (n = 8), hemodynamics were studied after 15 minutes of global ischemia during cardiopulmonary bypass. In Group III (n = 8), hemodynamics were studied after regional ischemia produced by ligation of the proximal left anterior descending coronary artery. In Group IV (n = 7), myocardial oxygen consumption and left ventricular mechanics were studied before and after 1 hour of cardiopulmonary bypass. Our results indicate the following: (1) Dopamine-isoproterenol improves hemodynamics in basal, post-global ischemic, and post-regional ischemic states. Glucagon improves hemodynamics either insignificantly or to a lesser extent than dopamine-isoproterenol. Furthermore, glucagon produces a larger increase in heart rate, which is not desirable. (2) Both dopamine-isoproterenol and glucagon increase myocardial oxygen consumption in comparison with control.

Effects of pulsatile and nonpulsatile coronary perfusion on performance of the canine left ventricle.

This study compares the effect of pulsatile (Group C, Fib/P) and nonpulsatile (Group B, Fib/NP) coronary perfusion on myocardial performance during 2 hours of normothermic ventricular fibrillation. Group A (BH/NP), used as a base-line observation, consisted of 2 hours of nonpulsatile coronary perfusion in beating hearts. The assessment of ventricular performance included diastolic ventricular compliance, myocardial oxygen consumption and lactate extraction, regional myocardial blood flow, and histology. After 120 minutes of ventricular fibrillation, Group C showed normal ventricular diastolic compliance as compared to a 50 per cent decrease in Group B (p less than 0.01). Myocardial oxygen consumption was not significantly different from that in Group B. Because of a 70 per cent increase in oxygen extraction above Group B (p less than 0.05), total left ventricular myocardial blood flow was reduced (103 +/- 23 versus 260 +/- 36 ml. per 100 Gm. per minute, p less than 0.05) and had near-constant resistance. Lactate extraction was significantly greater and more stable as compared to Group B (9.28 +/- 1.33 versus 1.8 +/- 1.08, p less than 0.05). Left ventricular endocardial/epicardial flow ratio was greater in Group C (1.21 +/- 0.08 versus 1.06 +/- 0.06, p less than 0.05). Minimal subendocardial histologic changes were present as compared to the marked patchy subendocardial ischemic changes seen in Group B. The results demonstrate that the addition of pulsatile flow to coronary perfusion minimized the deleterious effects of prolonged ventricular fibrillation on myocardial performance.

Cardiac output in infants and children after open-heart surgery.

Green dye measurements of cardiac index (in liters per minute per square meter) were compared in 32 infants and 58 children, 6 and 24 hours after normothermic cardiopulmonary bypass. Cardiac index was significantly lower in infants under one year of age, as compared to older infants and children. This parameter was also lower in patients with total anomalous pulmonary venous drainage, truncus arteriosus, and tetralogy of Fallot. Five infants who died had 6-hour cardiac index determinations of 2.0 L./min./sq. M. Only 2 of 27 survivors had cardiac indices below this level. Simultaneously recorded heart rate and central venous pressure did not correlate with cardiac index. Systolic blood pressure was significantly lower in infants in whom the cardiac index was less then 2.0 L./min./sq. M. (p less than 0.01). However, in individual situations, determination of systemic blood pressure lacked specificity in predicting outcome. Measurements of cardiac index are helpful in the management of infants and children following intracardiac repair by (1) assessing the hemodynamic status, (2) providing a useful indication of the cardiocirculatory effects of therapeutic interventions, and (3) predicting outcome.

Pulmonary atresia with intact ventricular septum. Sixteen-year experience.

Infants with pulmonary atresia and intact ventricular septum (PA-IVS) usually require urgent surgical intervention. Thirty patients with this anomaly, seen at the Columbia-Presbyterian Medical Center between 1962 and 1978, had palliative operations, 26 within the first 3 days of life. Six underwent a closed pulmonary valvotomy alone, with no survivors; six had only a systemic--pulmonary artery shunt, with three early survivors. Because of this experience, 17 had a combined procedure of valvotomy and shunt, with 14 early survivors. One patient recently underwent a definitive right ventricular outflow patch procedure with cardiopulmonary bypass. Eight patients subsequently have had corrective open-heart procedures, with five patients surviving from 2 to 10 years. A unicusp aortic homograft was used for repair in five and a Hancock valved conduit in three. Four patients are presently awaiting operation. We conclude that the initial surgical management of these critically ill infants must not only increase pulmonary blood flow but in addition provide an opportunity for right ventricular growth. Thus we continue to advocate the combined procedure of a valvotomy plus a shunt to provide adequate palliation. Repeat catheterization should be performed within a year to confirm the adequacy of the valvotomy, since this is essential to maximal right ventricular enlargement and to allow for definitive correction at a later date.

Comparison of intraoperative nitroprusside unloading in mitral and aortic regurgitation.

To compare the hemodynamic effect of vasodilator therapy on different regurgitant lesions, we infused sodium nitroprusside intraooperatively in 12 patients with mitral regurgitation and 15 with aortic regurgitation. During the critical period preceding establishment of cardiopulmonary bypass, both groups had developed intense vasoconstriction and cardiac decompensation. All demonstrated improved cardiac function with vasodilator therapy; however, the degree of improvement with nitroprusside differed in the two groups. Stroke volume increased 10 ml. per beat per meter squared in those patients with aortic regurgitation and only 6 ml. per beat per meter squared in those with mitral regurgitation (p less than 0.05). The percent increase in stoke volume induced by nitroprusside was inversely correlated to the preoperative left ventricular ejection fraction (r = 0.44, p less than 0.02). Patients with aortic regurgitation had lower preoperative left ventricular ejection fractions than those with mitral regurgitation (0.53 versus 0.63, p less than 0.02). Therefore, we conclude that patients with aortic regurgitation derived greater intraoperative hemodynamic benefit from unloading with nitroprusside, because they came to surgery with greater impairment of left ventricular contractility. Although nitroprusside improved cardiac function in both groups, only the patients with aortic regurgitation achieved normal pulmonary artery pressure (17 torr) and pulmonary vascular resistance (2.1 units) as a result of unloading. Those with mitral regurgitation continued to have pulmonary hypertension (28 torr) and increased pulmonary vascular resistance (3.9 units) despite vasodilator therapy. Thus the data suggest that patients with mitral regurgitation derived less hemodynamic benefit from intraoperative nitroprusside therapy because they were also limited by right ventricular dysfunction and a less responsive pulmonary vasculature.

Increased cardiac output by downstream pumping with a reversed unidirectional intra-aortic balloon.

Downstream and upstream pumping with unidirectional intra-aortic balloons was compared in 8 open-chest normal mongrel dogs anesthetized with pentobarbital. Downstream pumping effect a 32 per cent increase in cardiac index, a 24 per cent decrease in systemic resistance, and a 2 per cent decrease in heart rate. Upstream pumping did not significantly affect these parameters. Mean aorta pressure proximal and distal to the balloon was not altered significantly by pumping in either direction. This unique observation of increased cardiac output may have important implications for the treatment of low output cardiac failure. Preliminary studies including baroreceptor denervation suggest that a reflex mechanism may be involved.

Pharmacologic antagonism of beta adrenergic blockade in dogs. II. Hemodynamic effects of simultaneous intravenous infusion of isoproterenol and dopamine during chronic propranolol administration.

Chronic beta adrenergic blockade was induced in eight dogs with 240 to 360 mg of oral propranolol dailty for 2 to 6 weeks. Beta blockade was confirmed by a minimal heart rate response to isoproterenol, 0.06 micrograms/kg/min, in a pentobarbital-anesthetized, open-chest preparation. Subsequent to confirmation of beta blockade, hemodynamic effects of isoproterenol and dopamine were examined individually and in combination. A desirable balance of arterial pressure and cardiac output was achieved by combining isoproterenol, 0.2 to 2.0 micrograms/kg/min, with dopamine, 5 to 20 micrograms/kg/min. This combination increased mean arterial pressure (109 +/- 9 versus 81 +/- 7), cardiac output (4.3 +/- .5 versus 2.8 +/- .3 L/min) and heart rate 156 +/- 4 versus 120 +/- 7) (p less than 0.05). The hemodynamic effects of combined isoproterenol-dopamine were superior to the effects of either drug alone and suggest a method for effective circulatory support of man during chronic beta adrenergic blockade.

Preparation of fibrin glue from single-donor fresh-frozen plasma.

Fibrin glue is used widely in Europe as a tissue sealant and hemostatic agent. The European glue is prepared commercially from pooled human blood. It is not available in this country because of the risk of transmission of hepatitis B, acquired immune deficiency syndrome, and other blood-transmitted diseases. We describe a cryoprecipitation technique for preparation of fibrin glue from single-donor fresh-frozen plasma. This technique enables the glue to be made in large quantities with no greater risk of disease transmission than with that from the transfusion of single-unit fresh-frozen plasma. We have found that the glue is a useful tool in surgery. By helping to control difficult bleeding, its use can decrease the need for blood transfusions and shorten operating room time. It also is effective as a means to pretreat highly porous vascular prostheses that currently are used infrequently because of bleeding. These porous grafts offer potential advantages in handling, suturing, and long-term patency. This new technique of fibrin glue preparation may make this useful surgical adjunct as readily available in this country as it is in Europe.

Adjustable annuloplasty for tricuspid insufficiency.

De Vega described a technique for tricuspid annuloplasty using synthetic suture to reduce the size of the dilated annulus. We present our experience with an adjustable modification of de Vega's suture annuloplasty technique. The records of 12 patients followed for 15 to 30 months were reviewed. All 10 survivors had a significant drop in right-sided filling pressure (average, 39% decrease) and an associated improvement in clinical status. The 2 deaths in the series were not related to persistent tricuspid insufficiency. This technique represents a reliable, rapid, and readily teachable method for the surgical management of tricuspid insufficiency.