Samuel B. Itscoitz

Relation between echocardiographically determined left atrial size and atrial fibrillation.

In an attempt to define quantitatively the relation between left atrial size and atrial fibrillation, echocardiography was used to study 85 patients with isolated mitral valve disease, 50 patients with isolated aortic valve disease, and 130 patients with asymmetric septal hypertrophy. In all three groups of patients, atrial fibrillation was rare when left atrial dimension was below 40 mm (3 of 117 or 3%) but common when this dimension exceeded 40 mm (80 of 148 or 54%). In addition, when left atrial dimension exceeds 45 mm, cardioversion, while initially successful, is unlikely to produce sinus rhythm that can be maintained at least six months. These data suggest that left atrial size is an important factor in the development of atrial fibrillation and in determining the long term result of cardioversion. The pathophysiologic mechanism most consistent with this is that a chronic hemodynamic burden initially produces left atrial enlargement which in turn predisposes to atrial fibrillation. Only prospective studies will determine definitively whether these observations will be useful in decisions concerning prophylactic anticoagulation and elective cardioversion.

Operative treatment in hypertrophic subaortic stenosis. Techniques, and the results of pre and postoperative assessments in 83 patients.

The results of operative treatment in 83 patients with idiopathic hypertrophic subaortic stenosis (IHSS) are described. Most patients with the disease are asymptomatic, or derive satisfactory symptomatic improvement from nonoperative therapy: administration of propranolol, exercise limitation, control of arrhythmia, etc. Operation is required, however, in 10-15% of patients, those who remain severely symptomatic after nonoperative treatment or who become refractory to it. Operation relieves symptoms in IHSS by relieving obstruction to left ventricular outflow, and for a patient to be considered an operative candidate severe obstruction must be documented at left heart catheterization either under resting conditions or after provocative interventions. All 83 patients were severely incapacitated — 58 in Class III and 24 in Class IV. Seventy had obstruction at rest (average gradient 96 mm Hg), and 13 had only provocable obstruction. At operation the hypertrophic interventricular septum was exposed via an aortotomy, and a vertical bar of muscle was resected between parallel myotomy incisions. There were six operative deaths (7%); no patient has died since 1970. Seven patients have died late after operation, five of them from causes unrelated to their heart disease or the operation. All surviving patients describe symptomatic improvement. Fifty-two patients with obstruction at rest preoperatively (average gradient 95 mm Hg) have been studied postoperatively: no resting gradient was evident in 47, while in the remaining five the gradient was less than 25 mm Hg. Recurrence of obstruction has never been observed at late catheterization (21 pts) or late echocardiographic examination (37 pts). Obstruction could not be provoked postoperatively in ten of the 11 patients who had large gradients only with the Valsalva maneuver or isoproterenol administration preoperatively. Obstructed and provocable obstructed patients had similar symptomatic improvement after operation. A variety of rhythm and conduction abnormalities were observed both pre and postoperatively, and these are described in detail. The results of operation in these 83 patients with IHSS demonstrate that gratifying symptomatic and hemodynamic improvement uniformly follows left ventriculomyotomy and myectomy. Relief of obstruction and amelioration of symptoms have proved to be long-lasting during postoperative observation periods extending to 14 years. Continued application of the operative procedure in properly selected patients appears to be indicated.

Determinants of ventricular septal motion. Influence of relative right and left ventricular size.

To test the hypothesis that the ventricular septum moves during systole toward the center of the ventricular mass (so that the end-diastolic position of the septum within the heart should determine both the direction and the magnitude of septal motion during systole), echocardiograms from patients with several different hemodynamic burdens were analyzed. A linear relation was noted between the end-diastolic intracardiac position of the ventricular septum and the direction and magnitude of systolic septal motion in 1) forty three patients with an atrial septal defect )regression coefficient r = 0.80), 2) fourteen patients with other causes of right ventricular volume overload (r = 0.82), 3) nineteen patients with left ventricular volume overload (r = 0.74), 4) ten patients with right ventricular pressure overload (r = 0.93), 5) ten patients with left ventricular pressure overload (r = 0.80), 6) twenty-eight normal subjects (r = 0.82). We conclude that, in the presence of normal ventricular activation and contraction, the direction and magnitude of sepatal motion during systole is determined by the intracardiac position of the septum at enddiastole.

Deterioration of Myocardial Function Following Aorto-Coronary Bypass Operation

Twenty-two patients underwent cardiac catheterization before and an average of five months after aorto-coronary bypass operation (ACBO). Two groups were examined: 10 patients with all grafts patent, and 12 patients with one or more grafts occluded. All patients improved symptomatically, regardless of graft patency. However, in the occluded group, left ventricular end-diastolic pressure (LVEDP) increased (4.4 ± 2.2 mm Hg, P < 0.05), stroke volume index fell (9.8 ± 3.1 ml/m2, P < 0.05), ejection fraction decreased (10 ± 4%, P < 0.05), and left ventricular stroke work index fell (12 ± 3 g-m/m2, P < 0.01).Qualitative analysis of segmental left ventricular contractility was performed. Of 28 segments supplied by patent grafts, six improved and nine deteriorated. Of 22 segments supplied by occluded grafts, none improved and eight deteriorated. Frequently no angiographically demonstrable basis for the segmental deterioration was evident.We concluded that while ACBO may appreciably benefit severely symptomatic patients, our results do not substantiate the claim that ACBO should be recommended when the primary surgical goal is preservation or enhancement of myocardial function.

Evaluation of aortic valve replacement in patients with valvular aortic stenosis.

Echocardiographic and hemodynamic studies were obtained in 42 consecutive patients undergoing aortic valve replacement for isolated aortic stenosis. Concentric left ventricular (LV) wall thickening, the most common preoperative abnormality, occurred in 95% of patients. LV dilation with reduced fractional shortening was noted in approximately 25% of patients but was severe in only one patient. Six months after operation, LV wall thickness had decreased on average but had not returned to normal and fractional shortening was unchanged. Repeat measurements in 13 patients an average of 37 months after operation were unchanged compared with measurements made 6 months after operation. When patients were subdivided into those with LV dilatation and those without, we found that patients with dilated ventricles preoperatively had a greater decrease in LV internal dimension and mass than those without preoperative dilatation.The patient data also were examined for possible association with mortality. One operative (2%) and five late cardiac (13%) deaths occurred. No preoperative or 6-month postoperative echocardiographic or hemodynamic measurement was strongly associated with these deaths, nor were any late deaths due to congestive heart failure.Compared with preoperative measurements in symptomatic patients who were operated for isolated aortic regurgitation, patients with aortic stenosis had smaller left ventricles with less depression of systolic function, as well as less aortic root and left atrial dilatation. Our data do not support the concept that the aortic valve should be replaced before the onset of symptoms to prevent irreversible LV damage in patients with isolated aortic stenosis.

A Method for Evaluating Computer Programs for Electrocardiographic Interpretation II. Application to Version D of the PHS Program and the Mayo Clinic Program of 1968

A previously described method for evaluating computer programs for electrocardiographic (ECG) interpretation was applied to Version D of the Public Health Service (PHS) program and to the Mayo Clinic program of 1968. Staff cardiologists found agreement with the results of the PHS program in 45.5% of 1150 unselected tracings. Clinically significant disagreements based strictly on application of different criteria occurred in 29%, while disagreements based on program errors were found in 25.5%. The corresponding results for the Mayo Clinic program are: agreement in 47%, disagreements due to criteria differences in 30.9%, and disagreements due to program errors in 22.1%.Both programs had serious deficiencies, particularly in the diagnostic categories of myocardial infarction and cardiac arrhythmias. PHS program errors resulted primarily from mismeasurements and deficient program logic, while Mayo Clinic program errors more frequently resulted from pattern recognition failures. Neither program appears suitable for routine clinical use at the present time.

A Method for Evaluating Computer Programs for Electrocardiographic Interpretation I. Application to the Experimental IBM Program of 1971

A method for evaluating computer programs for electrocardiographic interpretation is described. This method allows a clinician to judge the usefulness of a program for his specific setting and needs. The method requires a significant proportion and variety of abnormal tracings, the application of specific fixed criteria, and the separation of disagreements between the computer program and the clinician into those resulting from criteria differences and those resulting from programming errors, viz., pattern recognition failures, mismeasurements, and/or deficient program logic. When applied to the experimental IBM program 1971, staff cardiologists found essential agreement with the programs results in 76% of 1150 unselected tracings. Clinically significant disagreements based strictly on the application of different criteria occurred in 20% of the tracings, whereas disagreements based on program errors were found in only 4%. Although this program requires some system of human overview and quality checking, its potential for clinical implementation is worthy of consideration.

Saphenous vein bypass grafts: Long-term patency and effect on the native coronary circulation

The long-term durability of saphenous vein bypass grafts and their effect on existing intrinsic coronary artery disease remain ill defined. Therefore, sequential catheterization studies were performed in patients selected for study solely on the basis of documentation of a patent graft at an earlier study performed three to nine months postoperatively; at that time 29 patent grafts were demonstrated in 20 patients. Fifteen to 36 months postoperatively (average 22 months), 27 grafts were unchanged, 1 manifested minimal luminal irregularities and 1 was occluded. In one additional patient, studied 4 months and 4 1/2 years postoperatively, the graft was widely patent and had good distal runoff at the second study. Sequential coronary arteriograms revealed that progression of disease to complete occlusion occurred in 24 percent of vessels with severe lesions proximal to a patent graft, whereas progression of disease distal to a graft anastomosis was uncommon. Of 25 vessels not receiving grafts, disease progressed in 5 (20 percent). Grafts that are patent 3 months after operation appear to remain patent for at least 2 to 3 years, and their presence does not unduly accelerate the disease process involving the native coronary arteries.

A Method for Evaluating Computer Programs for Electrocardiographic Interpretation III. Reproducibility Testing and the Sources of Program Errors

A simple method for testing reproducibility in ECG computer program performance results from using two digital representations of the same analog ECG tracing. Each digital representation is separated from the other by one millisecond in time. When the digital representations are processed by the Mayo Clinic program (1968), the diagnostic statements are identically reproduced in only 60% of 33 tracings. When the method is applied to version D of the PHS program and to the newly released IBM program of 1973, identical reproducibility is 43.3% and 76.0%, respectively, of 217 tracings. After analog filtering these figures are improved to 49.8% and 79.7%, respectively. These results show that reproducibility is most affected by a programs algorithms for pattern recognition, measurement, consistency checking, and noise handling. Reproducibility is less affected by attenuation of high frequency noise at the analog level. The relationship of reproducibility to program error rate in previous studies is discussed. Hence poor performance on this test obviates the need for a more time-consuming clinical evaluation. The need for human overview and quality checking is re-emphasized.

Nitroglycerin-induced improvement in exercise tolerance and hemodynamics in patients with chronic rheumatic heart valve disease.

Nitroglycerin reduces elevated left ventricular filling and pulmonary arterial pressures in resting patients with rheumatic valve disease and reduces symptoms when given over long periods to patients with primary myocardial disease. To determine whether nitroglycerin may prove effective therapeutically in ambulatory patients with heart valve disease, its effects on hemodynamics and exercise capacity were studied in 11 severely symptomatic adults who were already receiving optimal treatment with digitalis and diuretic agents. Seven had predominant mitral valve disease, one had predominant aortic insufficiency and three had equally severe mitral and aortic valve disease. Maximal exercise capacity was assessed with graded treadmill exercise after placebo and after nitroglycerin (0.5 mg sublingually) administered in random sequence to each patient. Exercise capacity (exercise time to limiting fatigue or dyspnea) increased from a mean of 8.3 minutes after placebo to 9.8 minutes after nitroglycerin (P less than 0.005). Eight patients were studied hemodynamically during further intense treadmill exercise. Pulmonary arterial pressure was significantly lower (P less than 0.05) after nitroglycerin than after placebo (mean 44 versus 56 mm Hg), but cardiac output was greater after nitroglycerin (5.0 versus 4.6 liters/min, P less than 0.005). Thus, nitroglycerin appears to increase exericse tolerance and improve the hemodynamic response to exercise in patients with heart valve disease and may be valuable in the long-term pharmacologic therapy of such patients.