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may be entirely normal in the absence of stress; "Con­ sequently, exercise or atrial pacing has been used in our laboratory in the preoperative evaluation. Al· though exercise stress appears to be a sensitive crite­ rion, it is contraindicated in the presence of the "preinfarction syndrome"; hence, such studies are not performed in patients with this syndrome. Low surgical mortality rates in many reported studies reflect the selection of low risk patients with good ventricular function. In our experience with more than 500 patients, the mortality rate for the group with poor left ventricular function was ap­ proximately 15 percent. Surgical mortality is also greater in patients with triple vessel disease than in those with single vessel disease. 4 It has been re­ ported 4 that the hospital mortality is slightly greater in those with double and triple vessel disease than in those with single bypass. These statistics are even more meaningful if the surgeon is not able to bypass an obstructed coronary artery. Patients who were subjected to an incomplete procedure wherein all the obstructed vessels could not be adequately bypaflsed did poorly after surgery. An anastomosis inadequate because of technical problems or severe distal ath­ erosclerosis permits continuing ischemia, and the operative and postoperative risk is thereby greatly increased. The number of operative deaths among patients with impending myocardial infarction varies consid­ erably, ranging from a to 19 percent. 5-8 These dispa­ rate results represent various methods of selecting patients. Apparently, these groups of patients are not homogeneous, and the risk and prognosis vary considerably. The physician at the bedside is not al­ ways able to differentiate preinfarction from the e­ volving infarction syndrome. We believe the mortality to be much greater in patients with evolving infarc­ tion and therefore do not recommend the operation at that particular time. What is the operative morbidity? Complications at the time of operation and during the immediate postoperative period include ventricular failure and cardiogenic shock due to prolonged pump time, myo

Advanced or second-degree atrioventricular (AV) heart block pro-existing or developing during atrial pacing (AP) at low heart rates of

This study describes a new method (NM) for estimation of sinoatrial conduction time (SACT), which utilizes constant atrial pacing (AP) instead of the premature atrial beats (PABs) used in the method reported in 1973 by Strauss et al. The SACTs were obtained by both methods in 20 patients. The SACT by the Strauss method (SM) was calculated as A2A3 minus A1A1. The NM consists of high right AP for a train of eight consecutive beats at rates less than or equal to 10 beats/min faster than the sinus rhythm. The interval between the last paced atrial electrogram (Ap) and the first escape atrial electrogram (A) of sinus origin (Ap-A) was measured along with several post pacing sinus cycles. The SACT by the NM was calculated as follows: SACT = Ap-A minus A1A1. The effect of AP at higher rates was also analyzed. In two patients, the SACT with the SM could not be defined, as all the A2A3 intervals were fully compensatory; with the NM the SACT was 217 and 320 msec. In the remaining 18 patients the SACT was obtainable by both methods. With SM, the SACT ranged 105--452 msec (mean 219 +/- 102 SD) and with the NM it was 85--492 msec (mean 201 +/- 112 SD), and the difference was statistically significant (P = 0.0162). The coefficient of correlation between the two methods was r = 0.97. During AP at faster rates, a rate related increment in Ap-A intervals and also post pacing sinus cycles was noted. This study describes a new and simple method for measurement of SACT in man.

To appraise the functional significance of coronary collateral vessels, 78 consecutive patients with angina pectoris and at least 75 per cent obstruction in a major coronary vessel were studied clinically, hemodynamically, and angiographically and by stress testing. Forty-eight of them (62 per cent) had coronary collateral vessels. When patients with collaterals were compared with those without, the severity of angina pectoris and the number of positive treadmill ECG's were not statistically different. The patients with collaterals had a greater incidence of past myocardial infarction, 3348 (68 per cent) vs. 830 (27 per cent) (P = 0.001); more extensive obstructive disease angiographically, 8.0 ± 0.4 vs. 6.3 ± 0.5 (P = 0.05); more abnormal pacing ventricular function curves, 2223 (96 per cent) vs. 915 (60 per cent) (P = 0.01); and a greater incidence of left ventricular contraction abnormalities, 4348 (90 per cent) vs. 1630 (53 per cent) (P = 0.025). Patients who have coronary artery disease and collateral vessels cannot be distinguished from their counterparts without collaterals on a clinical basis except for a greater incidence of myocardial infarction in the former. Present evidence implies that collateral vessels may protect the patient by delaying the onset of angina pectoris, but when angina occurs these patients have more extensive coronary artery disease and greater myocardial dysfunction. In addition, collaterals, although not preventing, may limit the extent of myocardial infarction and reduce immediate mortality. The prognosis from the onset of angina pectoris may be worse in those patients with collateral vessels, however, because of their more extensive disease.

In a patient with a documented nonejection systolic click and late systolic murmur, acute mitral insufficiency developed as a result of spontaneous rupture of mitral chordae tendineae. There was no evidence of previous endocarditis, rheumatic fever or congenital heart disease. The ballooning mitral valve syndrome has previously been considered relatively benign. Chordal rupture has been predicted, and presumptive cases have been alluded to by several investigators. This well documented report of such a complication casts further doubt on the benignity of the syndrome.

Spectroanalysis was performed to evaluate aortic prosthetic valve function in 16 adult patients who were observed for a maximum of eight years. These patients were restudied because of symptoms or signs of cardiac deterioration or because of a new aortic regurgitant murmur. One of the 16 patients was restudied without these indications on the advice of his referring physician. All 16 underwent repeated catheterization and spectroanalysis. Nine were operated on again. On the basis of the catheterization or the surgical findings, or both, three groups of patients were categorized as the following: Group 1, normal prosthetic valve function and no aortic regurgitation; the four patients in this group had a normal spectroanalysis. Group 2, normal prosthetic valve function with a paravalvular leak; six of the seven patients in this group had a normal spectroanalysis, with one borderline result. Group 3, abnormal prosthetic valve function; four of the five patients in this group had abnormal spectroanalysis frequency cut-offs, with one borderline result. Spectroanalysis is a safe, reliable, noninvasive method for clinical investigation of aortic prosthetic valve recipients. It is helpful in distinguishing patients with paravalvular leaks from those with true prosthetic valve dysfunction. A normal spectroanalysis suggests a normally functioning aortic prosthesis. The need for repeated catheterization and possible operation then rests solely on the presence or absence of significant cardiac signs or symptoms noted clinically.

This is a report concerning two cases of unusual complications, dissection and rupture of the ascending aorta, secondary to saphenous vein bypass surgery. We recommend that evaluation of patients undergoing saphenous vein bypass surgery include careful image-intensifier fluoroscopic examination during coronary arteriography. If aneurysmal dilatation of the aorta or calcification is observed, ascending aortography should be performed to better evaluate the aorta, and surgeons should be alerted to use appropriate maneuvers and techniques to minimize the risk of complications in the aortic site of the vein anastomosis. Internal mammary coronary-artery bypass should be the procedure of choice in such conditions.

The hemodynamic effects of pacing the outflow tract of the right ventricle were compared to those of pacing the inflow tract of the right ventricle at identical rates over a wide range of rates in subjects with either normal or abnormal A-V conduction. The results demonstrate that the hemodynamic sequelae of pacing the outflow and inflow tracts of the right ventricle are essentially similar and do not differ statistically. This study offers additional evidence of the relatively unimportant role of ventricular asynchrony in the cardiac performance in man.

The LVEDP, cardiac output, and V o o2 were measured before and during supine muscular exercise in 38 patients. The normal pattern, established in seven patients without left ventricular dysfunction, consisted of an exercise factor [see Equation in PDF File], an LVEDP during exercise of less than 12 mm Hg, and little change or a decrease in LVEDP, which was accompanied in most instances by an increase in the stroke volume. In the majority of 31 patients with various cardiac lesions, but without valvular regurgitation, measurement of the LVEDP before and during exercise permitted the definition of normal or abnormal left ventricular function when the status of the left ventricle could not have been ascertained from other measurements. Thus, in most of the patients with mitral stenosis and abnormal resting hemodynamics, the pattern of left ventricular function during exercise was considered to be normal. Among the patients with aortic stenosis or left ventricular myocardial disease and elevated resting LVEDP, two types of abnormal performance of the left ventricle were identified. In some patients, an increase in LVEDP was accompanied by an increase in stroke volume, and this response was termed "abnormal left ventricular dynamics"; in the remaining patients, an increase in LVEDP and no change or a fall in stroke volume occurred and this response was termed "depressed left ventricular function." It is concluded that determination of the LVEDP before and during exercise adds importantly to measurements of the changes in cardiac output and O 2 consumption in characterizing left ventricular performance. The method employs standard catheterization techniques and appears to provide a practical and useful means for evaluating the functional status of the left ventricle in patients with and without myocardial dysfunction.

Permanent pervenous pacing is now feasible with fixed rate and blocking or QRS synchronous demand pacers. Pervenous synchronous pacers still present problems that prevent their widespread use. Several considerations have led us to prefer QRS synchronous demand pacers to other varieties of permanent pervenous pacers at this time. The QRS synchronous demand pacer (the Ektocor) is readily available at this hospital and soon will be generally available commercially. Several electrocardiographic patterns associated with the use of demand pacers are illustrated.

The circulatory responses to nitroglycerin and to the Valsalva maneuver were studied in seven patients with idiopathic hypertrophic subaortic stenosis, in five patients with valvular aortic stenosis, and in three patients without obstruction to left ventricular outflow. In contrast to the patients with valvular stenosis who showed no changes or decreases in their aortic valvular pressure gradients, in all the patients with idiopathic hypertrophic subaortic stenosis an increased pressure gradient was observed following nitroglycerin administration. Similar effects on the pressure gradients were observed during the Valsalva maneuver, an augmentation occurring in patients with hypertrophic obstruction, and a fall being noted in patients with valvular stenosis. In one patient with idiopathic hypertrophic subaortic stenosis, the gradients across the right ventricular outflow tract were increased by nitroglycerin and the Valsalva maneuver. It is postulated that this increase in obstruction resulted primarily from a decrease in ventricular size secondary to the reduction in venous return induced by these interventions. It is proposed that reduction in the size of the left ventricle in patients with idiopathic hypertrophic subaortic stenosis, whether induced by changes in venous return, a decrease in arterial pressure, or by agents having a positive inotropic action, reduces the effective size of the outflow orifice. The administration of nitroglycerin and the performance of the Valsalva maneuver in the course of left heart catheterization provide simple methods for detecting the presence of latent obstruction in patients with idiopathic left ventricular hypertrophy and for differentiating idiopathic hypertrophic subaortic stenosis from other forms of obstruction to left ventricular outflow.

Abnormalities of myocardial function are frequently noted in patients with rheumatic mitral stenosis (RMS). Since ventricular function curves (VFC) relating pacing induced changes in left ventricular end-diastolic pressure (LVEDP) and stroke work (SW) have been useful in distinguishing diminished function in patients with coronary artery disease and myocardiopathy, atrial pacing was carried out during cardiac catheterization in 13 patients with RMS and compared to six normal subjects. Heart rate (HR) changes were similar in the two groups and in both groups no changes occurred in afterload or cardiac output while stroke volume, SW and LVEDP decreased. In those with RMS as LVEDP decreased during pacing, left atrial pressure and transvalvular gradient increased. VFC were abnormal in 5 of 13 with RMS when compared to the normal subjects and the VFC correlated well with clinical and angiographic findings. Atrial pacing is useful in evaluating LV myocardial function in patients with RMS and aids in the separation of myocardial from obstructive factors. Since HR changes are reproducible, it can be used for preoperative and postoperative comparisons.

These studies have confirmed the presence of late mitral regurgitation associated with a peculiar deformity of the mitral valve in patients with a late apical systolic murmur. This lesion is not always innocuous, however, as 4 of 8 of our patients have a severe degree of mitral regurgitation, 2 of them also having a significant amount of left ventricular and left atrial enlargement. In addition, in 1 patient with similar clinical findings bacterial endocarditis has developed. Evidence for a congenital origin of this lesion in some of these patients is also presented.

Low amplitude electrical stimuli delivered to the chest wall from a portable pacemaker may be used to suppress the implanted QRS-blocking, demand-type pacemaker. This technique allows analysis of the underlying electrocardiogram. The value of this method in the study of the natural history of conduction system disease, pacemaker-conduction system interaction, and in management of patients wearing these devices is illustrated.

In a patient with normal atrioventricular conduction, a Supraventricular tachycardia was repeatedly initiated and terminated by a single premature atrial beat. During the tachycardia, the atrial to His bundle activation time (A-H time) of the His bundle electrogram increased (P-R interval prolonged), and the polarity of the P wave remained unaltered. These observations suggest the creation and abolition of a circus movement of an unusual type, probably solely intraatrial, by a single premature atrial beat.

A consecutive series of aortic root cineangiograms was reviewed and the degree of aortic valve insufficiency (AI) correlated with clinical, hemodynamic, and operative data. The best correlations occurred in patients with pure AI; the clinical and hemodynamic values (pulse pressure, left ventricular end-diastolic pressure, aortic diastolic pressure, left ventricular hypertrophy) were not generally as helpful in evaluating the extent of AI in patients with mitral valve disease. Aortic root cineangiography is especially important in this latter group and is extremely accurate in determining the need for aortic valve as well as mitral valve operation.

Thirty patients with 70 percent or greater obstruction in the left main coronary artery were evaluated during hemodynamic and angiographic studies. There were 25 male and 5 female patients; the average age was 54 years. Twenty-seven patients had moderate to severe angina pectoris, with 14 noting an increase in severity of chest pain within 6 months before arteriography. Six patients also had hemodynamic evaluation by atrial pacing. In each, angina pectoris was easily induced, and all 6 had abnormal pacing ventricular function curves with marked increase in left ventricular end-diastolic pressure associated with a reduction in left ventricular stroke work. Image intensification fluoroscopy revealed calcification in the left main coronary artery in 7 patients. A striking finding was the severity of obstructive disease in the other coronary arteries. Eight patients had total occlusion of the right coronary artery, and 29 of the 30 patients had 2- or 3-vessel disease. Significant coronary arterial collateral vessels were noted in 21 patients. Contraction abnormalities were present in 24 left ventriculograms. Three deaths were associated with cardiac catheterization (mortality rate 10 percent). Only 2 of 18 patients who underwent aortocoronary bypass surgery died. The 16 surgical survivors are in clinically improved condition after a follow-up period of 10 months. Three of 9 patients not operated on have died, all within 1 month of arteriography. Because of the high risk of sudden death, coronary arteriography should be performed with caution in a patient with severe angina pectoris, very positive findings on exercise testing, easily induced angina and heart failure with stress and calcification in the left main coronary artery. After cardiac catheterization all patients should undergo routine monitoring and, when technically feasible, saphenous vein aortocoronary bypass surgery should be performed.

Chest wall electrical stimuli, too weak to affect the heart, act as electrical signals to an implanted ventricular-inhibited (QRS blocking) demand pacemaker which interprets them as originating from the heart and consequently responds according to its specifications. Rapid external stimulation permits diagnostic interpretation of the spontaneous electrocardiogram by completely inactivating the implanted pacemaker. The slow random delivery of external stimuli throughout the cardiac cycle delineates the pacemaker refractory period after the emission of a pacing stimulus and after the sensing of a spontaneous beat. During apparent fixed-rate pacing the demand capability of the pacemaker may be easily seen by appropriately timed chest wall stimulation which induces the pacemaker to sense a spontaneous QRS complex. This simple technique may reveal subtle changes in pacemaker performance, and contributes to the understanding of pacemaker arrhythmias.

Left ventricular function curves were constructed in 42 patients (18 normal, 5 with myocardial disease and 19 with coronary artery disease) by determining the responses to graded infusions of angiotensin. The curves were compared to standard methods of hemodynamic evaluation. The patients with coronary artery disease were in a wide range of functional categories with no consistent correlation between anatomic changes (determined angiographically) and left ventricular function. However, an abnormal left ventricular end-diastolic pressure or left ventricular cineangiogram always meant poor function, but abnormal reserve could be detected when these two measures were normal. The angiotensin infusion test proved to be safe and rapid in patients with coronary artery disease and is valuable in the preoperative assessment of left ventricular function, since standard objective measurements may be misleading. It can also provide an objective measurement in the patient after operation.

The diagnosis of familial cardiomyopathy was established by cardiac catheterization and cineangiography in six patients belonging to the same family. Five patients exhibited obstructive cardiomyopathy of the idiopathic hypertrophic subaortic stenosis type, while one displayed myocardial hypertrophy with a dilated poorly contractile left ventricle without obstructive phenomena. These observations support the concept that idiopathic hypertrophic subaortic stenosis and idiopathic myocardial hypertrophy represent different manifestations of the same disease. The disease was transmitted as an autosomal mendelian dominant with incomplete penetrance.

Atrial pacing and treadmill exercise were performed by 28 patients to determine the value of each test in the clinical and functional evaluation of the patient with coronary artery disease (CAD). The functional aerobic impairment (FAI) in 20 patients was 48 percent (eight patients with unstable angina paced but not exercised) and the pacing ventricular function curve (VFC) was abnormal in 13 of these 20. Five patients with severe FA1 (pain Limited) had a normal pacing VFC. Although the FA1 was greater the more extensive the CAD, no such correlation existed between the pacing VM= and the number of did coronary vessels. Exercise testing does not necessarily indicate the functional performance of the left ventricle since the V& max is frequently pein limited. Atrial pacing, although less sensitive, permits a VFC determination, even in poorly motivated and no* ambulatory patients, and combined studies will indicate the patient's clinical, as well as myocardial status. ince there may be no correlation between the control hemodynamic performance of the myocardium and the extent of coronary artery disease, some form of stress is usually required in evaluating this type of Most commonly, this is exercise stress either clinically or at cardiac catheterizati~n,~~ but infusions of angi~tensin,~ sustained hand grip,8 and atrial pacinga14 are also utilized to determine the functional status of the left ventricle. Although exercise may be the ideal method, the patient must be ambulatory and motivated, and the clinical situation should be stable. Therefore, unstable angina pectoris or a recent myocardial infarction is usually considered a reason to preclude this form of study. Many investigators have recently , used atrial pacing in the evaluation of patients with coronary artery disease since it is a controlled reproducible stress, which lacks the systemic metabolic effects of exercise and requires no particular cooperation on the part of the patient other than that of routine cardiac catheteri~ation.~'~ We and others have also utilized the multistage treadmill exercise test developed by Bruce and his as~ociates'~-~~ to evaluate and follow up these patients, and this has been used in conjunction with atrial pacing performed at the time of cardiac catheterization. This report describes our results in 28 consecutive patients with coronary artery disease, in whom both treadmill exercise and atrial pacing were performed. Although it is realized that each test is not measuring the same parameters, we have attempted to determine what relation exists between the two procedures. This was done to ascertain their individual and their combined potentials in determining the clinical and hemodynamic status of the patient with coronary artery disease. This knowledge is important since these techniques are so frequently used, especially in the preoperative and postoperative study of patients with coronary insdciency.

The study of the immediate hemodynamic effects of acute mitral valvar insufficiency (MI) has previously been limited to the experimental animal. The presence of a mitral valvar prosthesis, however, enables one to produce MI through passage of a transseptal catheter into the prosthesis to temporarily prevent proper seating of the ball or disc. In acute MI, so produced, there resulted a significant increase in heart rate, left ventricular end-diastolic pressure, pulmonary artery “wedge” pressure, and pulmonary artery pressure. Cardiac output and effective forward stroke volume decreased. The development of dyspnea and restlessness in three of six patients necessitated relief of the MI after seven to ten minutes. Withdrawal of the catheter, out of the prosthetic valve, returned the hemodynamic values to control levels within five minutes. Evidence is presented which indicates a protecting role for the pulmonary veins during the development of acute MI. No complications were noted in these six patients; however, only previously well-anticoagulated patients should be studied in this manner and then with great care.

Ventricular pacing is frequently associated with retrograde ventriculo-atrial conduction. In the absence of atrioventricular (A-V) block, the relatively intact antegrade A-V conduction system supplies the necessary pathway for a re-entry mechanism that may become operative in the presence of delayed retrograde conduction. Two patients with bradycardia and unimpaired antegrade A-V conduction exhibited reciprocal (echo) beating following nodal beats before ventricular pacing was instituted. After the introduction of an artificial ventricular pacemaker, reciprocal beats followed the paced ventricular beats in both patients. These observations suggest that a similar mechanism is involved in the production of reciprocal beats linked to impulses originating from the A-V node and the ventricles. When ventricular pacing is indicated for the treatment of bradycardia in the presence of intact antegrade A-V conduction, a situation which may produce echo beats, demand pacing is considered preferable to fixed-rate pacing as the latter may deliver a stimulus into the vulnerable phase following an echo beat.

A technic is described for controlling the heart rate in patients with normal atrioventricular conduction by means of an electrical pacemaker catheter that stimulated the right atrium. When the heart rates of 17 patients in the resting state were elevated from an average of 80 to 121 beats/min., the cardiac indices remained virtually unchanged and averaged 3.67 and 3.72 L./min./M. 2 , respectively. Further increases in the heart rates resulted in small reductions in the cardiac indices to an average value of 3.21 L./min./M. 2 at 148 beats/min. The stroke volumes, ejection periods, and mean rates of ejection decreased as heart rate was increased. The role of heart rate in the circulatory response to exercise was examined in seven patients. When the heart rates were controlled by electrical stimulation at rates comparable to those previously achieved spontaneously during exercise, it was observed that cardiac output rose normally with exercise and that this rise was accomplished entirely through an increase in the stroke volume. In five patients the effects of isoproterenol infusion were also studied before and during control of the heart rate at the level reached spontaneously during isoproterenol administration. Again, when the heart rate was not permitted to rise, the increases in cardiac output with isoproterenol were mediated through increases in the stroke volume. These studies indicate that in the absence of augmented metabolic requirements, homeostatic mechanisms maintain cardiac output relatively constant despite large induced changes in the heart rate. However, when metabolic demands are increased by muscular exercise, or the circulation is stimulated by catecholamines, cardiac output can rise through an increase in stroke volume, even when alterations in the heart rate are prevented.

A case of catheter-induced complete heart block in a patient with preexistent left bundle branch block is documented by His bundle recordings. It is recommended that a temporary pacemaker catheter on demand should be placed in the right ventricular apex in all patients with complete bundle branch block undergoing cardiac catheterization. In the coronary care units catheters should never be passed blindly to the right heart chambers in patients with left bundle branch block.

A patient with a “late systolic” murmur along the left sternal border was found to have an aneurysm of the membranous interventricular septum with a small left-to-right shunt through the dome of the aneurysm. A left ventricular cineangiogram, which delineated the nature of this shunt, helps to explain the auscultatory findings. Four other patients with this defect and a similar murmur have been reported. It is proposed that this murmur may be a clue to the clinical diagnosis in some patients with interventricular septal aneurysms.

Exercise testing has become standardized for the diagnostic and functional evaluation of male patients but little data is available regarding its specificity and sensitivity in the female. Therefore, maximum treadmill exercise (Bruce protocol) was performed on 98 consecutive females and compared to coronary arteriography. Using 50% obstruction as indicating coronary artery disease and 1 mm ST-segment depression (horizontal or downsloping) as positive for ischemia, 24 patients had coronary artery disease with seven false-negative results (sensitivity = 71%) and 74 patients had no coronary artery disease with 16 false-positive responses (specificity = 78%). Five of seven false-negative tests were in patients with single-vessel disease. Eleven of 16 false-positive responses were in patients on digitalis, diazepam, or methyldopa. In 39 patients on no drug therapy except for nitroglycerin there were no false negatives and only four false-positive tests. There were no false negatives and only two false-positive tests in 34 patients with normal resting electrocardiograms. Only one of 18 patients with both normal resting electrocardiograms and on no drug therapy had a false-positive test result. Eleven false-positive and seven false-negative results occurred in 40 patients with both an abnormal resting electrocardiogram and associated drug therapy. The exercise electrocardiographic response in female patients is similar to the male when patients with resting electrocardiographic abnormalities and concomitant drug therapy are eliminated.

A 47-year-old woman in normal sinus rhythm developed frequent pulse deficits, immediately following mitral valve replacement with a Beall disc prosthesis. Emergency bedside simultaneous tracing of echocardiogram, phonocardiogram and arterial pulse revealed a delayed opening of the disc with various timing intervals in diastole, and suggested some form of interference with normal disc motion. An interfering papillary muscle remnant was later confirmed and corrected by reoperation.

Echocardiographic studies were performed on 14 patients with endocardial cushion defects of different anatomic varieties. Four patients were studied again after operation. Patients with partial atrioventricular canal (PAVC) showed multiple systolic echoes on mitral valve echogram, with significant mitral-septal apposition in diastole. The left ventricular outflow (LVO) appeared significantly narrowed. The septal motions were paradoxic. After corrective operation, an increase in the width of the LVO was noted and mitral-septal apposition appeared to be less pronounced. Multiple systolic echoes, however, reappeared and persisted. The echocardiograms in patients with complete atrioventricular canal (CAVC) were characterized by wide excursion of an apparent single atrioventricular valve. The echoes of the mitral component of the common anterior leaflet moved anteriorly into the right ventricular cavity and overshadowed the tricuspid component in diastole. In addition, patients with CAVC and divided and medially attached common anterior leaflets had solitary mitral and tricuspid echograms. This feature differentiates this group of patients from those patients with CAVC with undivided freefloating common anterior leaflet.

To determine the validity and safety of exercise induced ST changes (1 mm ischemic depression or further depression in ECG lead V 5 ) as an indication of coronary artery disease (CAD) in patients with abnormal control electrocardiograms (ECG), 121 such patients were compared to 57 patients with a normal control ECG. All underwent a maximum graded treadmill exercise test and coronary arteriography. Among those patients with normal control ECGs, there were no false positives and five false negatives (sensitivity-85%, specificity-100%). In 61 patients with abnormal ECG (no drug therapy except nitrates) there were four false positives and nine false negatives (sensitivity-76%, specificity-79%). In this group of patients T waves reverted from negative to positive in four patients with CAD and 10 patients with no CAD, but T inversion during exercise only occurred in those with CAD (6 patients). Three of 12 patients (25%) with ECG evidence of old infarction and four of eight with single vessel disease had false negative tests. In 60 patients with abnormal ECG on drug therapy there were 10 false positives (17%) and 15 false negatives (sensitivity-55%, specificity-63%). Not helpful in differentiation were resting T vs ST changes, induction of arrhythmias or exercise induced chest pain. The validity of exercise induced ST changes in differentiating CAD is excellent when the control ECG is normal and is only slightly reduced with control ST-T wave abnormalities. When the latter occur in association with cardiovascular drug therapy, other than nitrates, the exercise ECG is of no use in differential diagnosis although still valid and safe for the determination of exercise tolerance.

The value of saphenous vein bypass surgery in the treatment of coronary artery disease will eventually be assessed through prospective randomized studies of homogeneous groups of patients undergoing either medical or surgical treatment. At present, there is insufficient evidence to demonstrate the beneficial effects of coronary bypass operations on prevention of myocardial infarction and prolongation of life. The improvement in the quality of life may be rewarding in patients with crippling angina pectoris in whom there is a major obstruction of the proximal coronary artery with good distal runoff and adequate ventricular function. This review summarizes our knowledge of the natural history of angina pectoris and examines the indications for a surgical approach in chronic, stable angina pectoris, in unstable angina, variant angina, main left coronary artery disease and acute myocardial infarction. Criteria for patient selection are tentatively defined.

Long-standing isolated traumatic tricuspid insufficiency in an elderly patient is reported. The hemodynamics and benign course of this lesion are compared briefly with the tricuspid insufficiency associated with rheumatic mitral and aortic valvulitis. We conclude that this lesion, when isolated, may be well-tolerated and managed medically for a long period of time.

A rare case of subacute bacterial endocarditis, due to a streptococcus viridans organism, is reported in a patient with idiopathic hypertrophic subaortic stenosis (IHSS). Subacute bacterial endocarditis prophylaxis is recommended for patients with IHSS.

Atrial pacing was performed in 10 patients with various degrees of aortic valvular stenosis (AVS) and the hemodynamics were compared to eight normal subjects. Similar maximum heart rates (135 ± 6/min) in each group resulted in no significant complications or symptoms and no changes in cardiac output or transvalvular pressure difference while stroke work (SW) and volume and left ventricular end-diastolic pressure (LVEDP) declined. A postpacing overshoot in LVEDP (control, 14 ± 2; postpacing, 25 ± 3 mm Hg; p = 0.01) which occurred in the cases of AVS probably reflects a decrease in myocardial compliance. Pacing ventricular function curves relating induced changes in SW and LVEDP were generally steeper in patients with AVS than in the normal subjects and were definitely abnormal in three of the former. Pulsus alternans induced in two patients was associated with abnormal myocardial function while the control LVEDP level was not a good indication of the functional response of the myocardium. Atrial pacing appears to be beneficial in the preoperative evaluation of the patient with AVS when exercise stress may be dangerous because of the possibilities of inducing arrhythmias, syncope, and sudden death. It permits precisely controlled evaluation for preoperative and postoperative comparison.

The first 21 survivors of mitral valve replacement with a Beall valve prosthesis were evaluated clinically and hemodynamically five months after surgery. Significant clinical improvement was noted in 18 of 21 patients. When compared with preoperative data, a significant improvement occurred in pulmonary artery and left atrial pressures, cardiac index, pulmonary vascular resistance, and in the mitral valve gradient. However, the majority of the patients still had mildly elevated left atrial and pulmonary artery pressures secondary to a mean resting prosthetic gradient of 7 mm Hg. Right heart pacing and exercise significantly increased the gradient and left atrial and pulmonary artery pressures. A remarkable freedom from thromboembolic complications was noted in this series of patients.

Cardiovascular effects of an intravenous injection of glucagon, 3 mg., were studied in 8 subjects during cardiac catheterization. In each study a prompt effect was noted, with an increase in heart rate, cardiac output, right ventricular dp/dt and right ventricular and systemic systolic pressures. Right ventricular end-diastolic pressure and systemic vascular resistance decreased. It is concluded that glucagon exerts positive inotropic and chronotropic effects upon the heart in man. Further studies are required to determine its proper clinical role and mechanism of action.

Five patients with “preinfarction” angina underwent cardiac catheterization, coronary arteriography and coronary artery bypass surgery without major complication. In order to evaluate myocadial function, stress testing by right atrial pacing was also performed. Pacing ventricular function curves were normal in three patients prior to angina and abnormal in each patient when angina was induced. Atrial pacing provides a safe technique for applying a stress in patients with preinfarction angina when exercise is contraindicated. It may be precisely controlled, gradually increased, rapidly discontinued and provides hemodynamic, electrocardiographic and clinical data for preoperative and postoperative comparisons.