Harold D. Levine

Theory of the Circular Diffraction Antenna

The circular diffraction antenna consists of a coaxial wave guide fitted with an infinite‐plane conducting baffle, and open to free space. An equivalent circuit description, appropriate to principal‐mode propagation in the coaxial region, is investigated theoretically. Variational expressions for the circuit parameters are derived, and used for accurate numerical evaluation.

Studies of Congenital Heart Disease IV. Uncomplicated Pulmonic Stenosis

Congenital pulmonic stenosis is indicated by cardiac catheterization by the finding of a higher systolic pressure in the right ventricle than in the pulmonary artery. Eight cases of uncomplicated pulmonic stenosis are studied. The findings on history, physical examination, x-ray and fluoroscopy, and electrocardiogram have been analyzed and the variations in circulatory dynamics encountered in these individuals are described in detail.

CLINICAL RECOGNITION AND TREATMENT OF ACUTE POTASSIUM INTOXICATION

Excerpt The toxicity to the living organism of an excess of potassium ion in the extracellular fluid has been recognized for many years.1, 2, 3The accumulation of toxic amounts of potassium may occ...

Acute myocardial infarction following wasp sting. Report of two cases and critical survey of the literature.

Summary Over the span of two or three days in August,1972, in two separate communities in eastern Massachusetts two men, one aged 39, the other 66, each without previous overt heart disease, were stung by wasps. Each went into shock rapidly, after an interval of over a half-hour developed chest pain and, later, sequential electrocardiographic changes diagnostic of acute myocardial infarction. Each survived; each had normal electrocardiograms before the sting. Though preexistent coronary artery disease can be excluded in neither, the view is favored that acute myocardial infarction in each was caused by deficient coronary perfusion secondary to anaphylactic shock induced by the wasp stings. An intriguing case was just recently reported 58 of a 62-year-old man with previous angina who developed pulmonary edema but no chest pain following wasp sting and went on to show rapidly reversed electrocardiographic changes attributable to subendocardial ischemia or infarction. In a sense, this sequence fills the gap as an intermediate phase between the normal and the two individuals described here who developed pain after anaphylactic shock, then proceeded, perhaps through this phase, to develop transmural infarction.

The Normal Apex Cardiogram: Its Temporal Relationship to Electrical, Acoustic, and Mechanical Cardiac Events

The configuration of the apex cardiogram and its temporal relationship to the electrocardiogram, phonocardiogram, carotid pulse, and jugular venous pulse were analyzed in 25 normal subjects. In two patients with rheumatic valvular disease simultaneous electrocardiograms, phonocardiograms, left intraventricular pressure and apex cardiograms were obtained. In all cases the apex cardiogram showed a characteristic and reproducible contour in both its systolic and diastolic components. The curves of the apex cardiogram display all consecutive phases of the cardiac cyle; contraction-and-emptying and relaxation-and-filling. It bears a constant relationship to the phonocardiogram and is more useful as a reference tracing for acoustic events than the electrocardiogram, carotid pulse, or jugular venous pulse. The onset of the systolic wave of the apex cardiogram precedes the rise of left intraventricular pressure and mitral valve closure. The maximal systolic peak of the apex cardiogram occurs simultaneously with the onset of left ventricular ejection and the rise of the carotid pulse pressure. Small deflections are frequently inscribed on the apex cardiogram at the time of mitral, tricuspid, and aortic valve closure.The wave form of the apex cardiogram is caused primarily by movements of the left ventricle against the chest wall. It is thus a translation of the sequence of hemodynamic events occurring in the underlying left ventricle. The inaccuracy of the jugular venous pulse for timing right- and left-sided cardiac events is emphasized.

Non-specificity of the electrocardiogram associated with coronary artery disease

Abstract Changes in the T wave, in the RS-T segment, and in the QRS complex of the electrocardiogram enerally reflect, respectively, myocardial ischemia, current of injury or death of muscle. The T wave, the most labile and least specific feature of the electrocardiogram, may be affected by a great variety of factors, only one of which is ischemia. Changes in the RS-T segment usually but not always correspond to acute muscle damage. It is generally transitory, rarely permanent. Like the T wave this may indicate an anatomical or a biochemical lesion. QRS changes practically always signify death or replacement of heart muscle; this is generally associated with coronary artery disease. Rarely it may result from heart muscle damage from other causes. The electrocardiogram is quite accurate in the detection of acute myocardial infarction but inaccurate in the diagnosis of old or of multiple infarcts. It remains to be seen whether the newer vectorcardiography will attain a greater accuracy.

Myocardial Fibrosis in Constrictive Pericarditis Electrocardiographic and Pathologic Observations

It has been suggested that a tentative preoperative decision favoring a pericardial lesion, on the one hand, or a myocardial lesion, on the other, may be made from certain noninvasive procedures, including the electrocardiogram. An attempt was therefore made to detect associated myocardial fibrosis by electrocardiogram in 67 patients with constrictive pericarditis as proven at catheterization (63 patients), surgery (64 patients) or postmortem examination (12 patients). Seven of the 67 had electrocardiograms characteristic of, and 16 compatible with, old myocardial infarct. The electrocardiographic experience was otherwise typical of the literature with non-specific changes in the T waves or RS-T segments and/or low voltage in the remaining 44. All three autopsied patients whose electrocardiograms were interpreted as diagnostic of an old myocardial infarct and both autopsied patients with electrocardiograms compatible with that diagnosis showed myocardial fibrosis. In seven autopsied cases with non-specific T waves or low voltage, the myocardium was normal in three while four showed myocardial fibrosis. It appears that in a few cases right ventricular hypertrophy might have simulated infarct by inducing tall R waves over the right precordium, or R waves which decreased in amplitude as the electrode was passed from the right to the left precordium.Pathologic evidence related myocardial fibrosis to: (1) direct subepicardial penetration by the inflammatory process or deposit of fat in the subepicardial myocardium; (2) compromise of coronary blood flow, as by (a) direct throttling of coronary arteries by scar tissue or (b) deficient irrigation of subendocardial layers due to rigidity of the pericardium; or (3) a concomitant myocardial and pericardial process (lupus, radiation fibrosis, rheumatoid). Independent pericarditis and coronary disease was surprisingly rare. This limited experience (1) suggests that, though myocardial fibrosis may be predicted in constrictive pericarditis if the electrocardiogram shows characteristic changes of myocardial infarction, non-specific T wave changes or low voltage may likewise be associated with myocardial fibrosis, and (2) emphasizes that the difficulty in determining the site of a constrictive process may be compounded by the co-existence in the same heart of both a pericardial and a myocardial process.

A Clinical Appraisal of the Vectorcardiogram in Myocardial Infarction

A total of 161 vectorcardiograms was recorded with the Grishman cube system in patients with suspected myocardial infarction. In the group of 49 cases subsequently examined post mortem and of 73 non-autopsied cases, in whom the diagnosis of infarction appeared certain, a comparison was made between the standard electrocardiogram and the vectorcardiogram taken in succession. The vectorcardiogram demonstrated more infarcts than the electrocardiogram. Of a total of 122 cases in which the vectorcardiogram showed infarction, 19 had normal and 17 equivocal electrocardiograms. A number of simple and easily applicable criteria for the vectorcardiographic diagnosis of infarction are given. It appears that even the older, uncorrected cubelead system permits a more accurate diagnosis than currently available standard electrocardiographic procedure. It is suggested that this method of exploration may be useful in cases of suspected myocardial infarction in which the routine electrocardiographic examination leaves doubt.

Paroxysmal atrial tachycardia with block.

THE digitalis drugs can produce nearly everv form of disturbed heart rhythmi. Thus far elinical attention has been directed to the venitricular effects. Digitalis-induced ventricular arrhythmias are therefore clearly catalogued and are recognized as of potentially grave signifieance. Recent studies indicate that certaiin atrial disorders are also imaniifestations of serious digitalis poisoning.1 Trhe prototype of these atrial arrhythmias is paroxysmal atrial tachyeardia with advanieed degrees of atrioventricular (A-V) block (referred to as PAT with block). This has been regarded as a hybrid disorder of rhythm exhibiting features of both atrial flutter and atrial tachyeardia. As in atrial flutter A-V block occurs either spontaneously or as a result of vagal stimulation. As in atrial tachyeardia the ectopic rate ranges from 150 to 250 per minute (fig. 1). A review of the literature suggests that PAT with block is anl unusual disorder of uncertain etiology. Somne of the leading cardiologists of our era have reported either isolated examples or small series of cases.2-10 The general view has been that PAT with block

Compromise therapy in the patient with angina pectoris and hypothyroidism: A clinical assessment

The teaching that thyroid replacement therapy can aggravate angina or induce myocardial infarction in patients with hypothyroidism and coronary disease, and thus compel acceptance of incomplete control of either, was substantiated in 51 patients (18 with iatrogenic and 30 with idiopathic primary hypothyroidism, and three with secondary hypothyroidism as a component of panhypopituitarism). Based upon clinical and laboratory criteria, control of hypothyroidism was unsatisfactory in two fifths of the patients. Judged by frequency and ease of induction of angina and nitroglycerine requirement, control of angina was unsatisfactory in one-third. In many patients maximal tolerated dose of thyroid varied with time. The effect of combined propranolol and thyroid therapy in 13 patients was quite satisfactory in seven patients, fair in three and poor in three, but excellent in none. Transfusions were useful as a short- or long-term expedient in a few. Of 12 patients considered for coronary revascularization, three were rejected because of other medical problems and one showed prompt improvement after the dose of thyroid was decreased. Five of the remaining eight studied by coronary cineangiography were rejected as unsuitable for surgery. The remaining three were subjected to coronary revascularization. One did well for a time, apparently until a graft became occluded, the remaining two are still doing well. Coronary bypass graft surgery may deserve a larger role in the future management of these patients.