Keith E. Cohn

RADIATION-INDUCED HEART DISEASE. A STUDY OF TWENTY-FIVE PATIENTS.

That high doses of x irradiation can damage the heart and pericardium is common knowledge among radiotherapists and radiobiologists. A small number of case reports have described cardiac lesions following radiotherapy of thoracic cancer; the prevailing feeling, however, is that such complications are rare and relatively unimportant (1). The purpose of this report is to review 25 cases in which significant heart disease followed radiation therapy to the chest for a variety of malignant tumors. Study of this unique series of patients from a single institution has provided data on the relative frequency of the various clinical features encountered and their correlation with the radiation technics and doses used, as well as estimates of the incidence of this group of complications in an irradiated population. The importance of recognizing cardiac complications and differentiating them from the manifestations of advancing neoplasm is emphasized. A previous report (2) described in detail the clinical findings, ...

Relation of left atrial pathology to atrial fibrillation in mitral valvular disease.

Abstract Biopsies of the posterior wall of the left atrium were obtained from 44 patients undergoing mitral surgery for mitral valvular disease, and the specimens were graded according to severity ...

Mechanisms of Pulsus Alternans

The mechanisms of pulsus alternans were studied in three patients by cineangiographic determinations of left ventricular volume. In two patients with left ventricular disease, pulsus alternans occurred without detectable variation in left ventricular enddiastolic pressure (LVEDP) or end-diastolic volume (EDV), although in the second case these values did alternate in the initial postextrasystolic beats. Another patient with normal left ventricular function had brief postextrasystolic pulsus alternans associated with LVEDV alternations. Twenty-nine patients with valvular aortic stenosis who showed pulsus alternans during left heart catheterization were also studied. Persistent alternation in LVEDP occurred in eight, with transient LVEDP alternation appearing after extrasystoles in 22 cases. Cardiac cycle length and diastolic interval alternation occurred inconsistently.

measurement of systemic cardiac output at rest and exercise in patients with atrial septal defect

Abstract The problem of accurate measurement of systemic cardiac output at rest and during exercise in patients with atrial septal defect was studied by three interrelated approaches. 1. (1) The optimal method of approximation of mixed venous blood oxygen saturation from the oxygen saturation of superior and inferior vena caval samples was evaluated by comparisons with pulmonary arterial samples in patients without intracardiac shunts. Optimal formulas derived by regression analysis were as follows: Mixed venous blood at rest = (3 SVC + 1 IVC ) 4 Mixed venous blood during exercise = (1 SVC + 2 IVC ) 3 2. (2) Arterial dye-dilution curves after left ventricular injection were established as a reliable method for determination of cardiac output by comparison with standard Fick determinations in patients without intracardiac shunts. 3. (3) Fick cardiac output values using the derived formulas were compared with dye-dilution values following left ventricular injection in patients with atrial septal defect. A close correlation was noted. It is concluded that systemic cardiac output may be measured with reasonable accuracy both at rest and during exercise in patients with atrial septal defect by either the Fick or the dye-dilution method.

Influence of Potassium Depletion on Myocardial Concentration of Tritiated Digoxin

The influence of potassium deficiency on myocardial 3H-digoxin concentration in the mouse was studied. Tritiated digoxin, 400 μg/kg, was injected intraperitoneally into mice, which were killed at varying time intervals, and the 3H-digoxin was extracted. One-half of the mice were made potassium deficient by a diet free of potassium. In control animals, myocardial 3H-digoxin was maximal by 30 min and declined through 24 hours. There was no significant difference between the myocardial 3H-digoxin of the control and potassium-depleted groups at ½ 1, 2, 6, or 16 hours, but at 24 hours a significantly higher concentration of digoxin was present in the potassium-deficient mouse hearts (23.6 ± 5.2 mμg/g) than in the control group (3.1 ± 1.5 mμg/g). Potassium-depleted mice with total renal failure, produced by bilateral ligation of the renal pedicle, showed increased myocardial 3H-digoxin levels at 20 hours as compared with mice with renal failure but without potassium deficiency. It is concluded that potassium deficiency may lead to increased concentrations of cardiac digoxin. The findings in the anuric animals suggest that diminished renal function produced by potassium depletion is not the sole mechanism of this retention of cardiac 3H-digoxin.

The Ejection Click of Valvular Pulmonic Stenosis

Ten patients with valvular pulmonic stenosis were studied by simultaneous external phonocardiograms and intracardiac pressure recordings during successive respiratory cycles to examine the mechanism of the respiratory variation in the ejection click. Selective cineangiograms were performed in four. During inspiration right ventricular end-diastolic pressure (RVEDP) exceeded the pressure in the pulmonary artery (+2.7 mm) and no ejection click was recorded. During expiration RVEDP was lower than the pressure in the pulmonary artery (-3.6 mm) and a click was recorded. The click was present throughout the respiratory cycle when pulmonary artery diastolic pressure consistently exceeded RVEDP. Clicks were associated with sudden “doming” of the valve demonstated by cineangiography. These data support the valvular origin of the ejection click in pulmonic stenosis and provide the following explanation for the respiratory variation: Inspiratory increase in venous return causes the valve leaflets to move to an open or “domed” position. Ventricular systole at this time produces no sound since there is no slack. With expiration pulmonary artery pressure exceeds RVEDP. Ventricular systole at this time produces an opening motion of the closed, slack leaflets. The click occurs when the opening motion is suddenly checked.

The effects of potassium on the positive inotropic action of ouabain

Abstract The effects of varying concentrations of extracellular potassium on the positive inotropic action of ouabain were studied in an isolated muscle preparation of guinea pig right ventricles. The isometric tension and peak dF dt were significantly greater at a concentration of extracellular potassium of 2 mEq. per liter than at the normal concentration of 5 mEq. per liter in control studies. There was no significant difference between the tensions or maximum dF dt at 5 and 10 mEq. per liter potassium. Ouabain produced a significant increase in tension and peak dF dt at all concentrations of potassium. The ouabain-induced increase in tension at 2 mEq. per liter potassium was not significantly different from that at 5 mEq. per liter, but the level of attained tension and dF dt were greater at 2 mEq. per liter since the base-line tension and dF dt at this concentration were greater. The positive inotropic effects of ouabain and low concentrations of extracellular potassium were, therefore, additive. At a potassium of 10 mEq. per liter the increment in tension and peak dF dt produced by ouabain was significantly less than at 5 mEq. per liter, and the absolute tension at 10 mEq. per liter was also significantly smaller. Possible mechanisms to explain these findings are considered.

Amyl nitrite inhalation as a screening test for hypertrophic subaortic stenosis

Abstract The influence of amyl nitrite inhalation on the ejection time, corrected for heart rate, was examined in 18 patients with hypertrophic subaortic stenosis and 34 with a variety of other cardiac diseases (control group). The corrected ejection time increased by 0.04 sec. or more in 11 of 18 patients (61 per cent) with hypertrophic stenosis after amyl nitrite; in the control group the corrected ejection time generally decreased, remained constant, or increased by less than 0.04 sec. The augmented degree of outflow obstruction produced by amyl nitrite probably accounts for the prolongation in corrected ejection time in hypertrophic subaortic stenosis. The change in ejection time after amyl nitrite inhalation may be conveniently studied during phonocardiography or right heart catheterization and employed as a simple screening test for hypertrophic subaortic stenosis. Thus, it is useful in determining the indications for left heart catheterization or angiocardiography in patients suspected of having this disease.