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Biomedical subjects

R E Fowles

Publications and source records attributed to R E Fowles.

31 records · Page 2Linked to original sources
PubMed1981

Spontaneous dissection of the ascending aorta diagnosed by two-dimensional echocardiography.

In two patients with acute dissection of the ascending aorta, the diagnosis was made with two-dimensional echocardiography and confirmed by aortography. The echocardiograms localized the intimal flap and false channel in both cases. Although clinical evaluation and indicated radiologic studies remain the primary modalities of diagnosis in acute aortic dissection, two-dimensional echocardiography may be a useful additional diagnostic technique.

Adult↗
PubMed1979

Two dimensional echocardiographic assessment of patients with bioprosthetic valves.

The clinical utility of two dimensional echocardiography in assessing bioprosthetic and left ventricular function was studied in 40 consecutive patients 1 week to 60 months after valve replacement surgery. These patients were referred to obtain normal baseline studies as well as to evaluate complications:suspected endocarditis, embolic phenomena and congestive heart failure of unknown cause. Independent M mode echocardiograms were also obtained in each patient. Confirmation of ultrasonic studies was by cardiac catheterization with angiography, surgery and pathologic study in 10 patients; cardiac catheterization with angiography alone in 7 patients; surgery and pathologic study in 3 patients; autopsy in 3 patients; blood cultures to confirm or exclude endocarditis in 10 patients; and confirmation on clinical grounds in 7 patients. Technically adequate two dimensional studies were recorded in 39 of 40 subjects. Two dimensional echocardiography accurately assessed 15 of 16 patients with an abnormal bioprosthetic valve and a normal left ventricle (1 of 16 patients had a false positive two dimensional echocardiogram); 8 of 8 patients suspected to have prosthetic valve or left ventricular dysfunction but who were normal; 7 of 7 patients with a normal prosthesis and an abnormal left ventricle; the one patient with an abnormal valve and left ventricle; and 7 of 7 clinically normal patients who were referred for baseline studies. In summary, the two-dimensional echocardiogram demonstrated a 97 percent diagnostic accuracy rate which was significantly greater than the 67 percent (P less than 0.001) for M mode echocardiography in the same group of patients. It is concluded that two dimensional echocardiography has excellent diagnostic accuracy in assessing bioprosthetic and left ventricular function and is superior to M mode echocardiography in evaluating patients after such valve replacement.

Adolescent↗
PubMed1979

Single and two dimensional echocardiographic features of the interatrial septum in normal subjects and patients with an atrial septal defect.

The interatrial septum is one of the least studied structures in M mode echocardiography. Two dimensional echocardiography has made it possible to record simultaneous M mode and two dimensional echocardiograms. Such studies were performed in 10 normal subjects and in 9 patients with a secundum atrial septal defect. In the short axis view of the base of the heart, the interatrial septum was visualized in the two dimensional studies as a linear echo running from the posterior aortic wall to the posterior atrial wall and in the M mode records as a series of dense echoes posterior to the aorta. The great variability in echo dropout of the interatrial septum made it impossible to distinguish the normal subjects from the patients with atrial septal defect. The dense echoes of the interial septum in the M mode records gave the false impression that they were filling the left atrium. These data indicate that (1) a secundum atrial septal defect cannot be reliably differentiated from a normal septum using these echocardiographic methods, and (2) the medial location of the interatrial septum should be appreciated so that it will not be confused with a left atrial mass.

Echocardiography↗
PubMed1979

Effect of coronary arterial bypass surgery on exercise-induced ventricular arrhythmias. Long-term follow-up of a prospective randomized study.

The effect of coronary arterial bypass surgery on exercise-induced ventricular arrhythmias and their relation to sudden death was examined in 102 patients with stable angina pectoris randomly assigned to medical and surgical therapy (54 and 48 patients, respectively). Symptom-limited treadmill tests were performed at entry and at 1 and 5 years. The surgical group demonstrated significant improvement in exercise performance at 1 year compared with the medical group, and at 5 years exercise-induced ischemia as evidenced by S-T depression and exertional angina remained substantially decreased in the surgical group with little change in the medical group. However, the frequency and severity of exercise-induced ventricular arrhythmias in each group remained unchanged at 1 and 5 years from those at entry. Similar results were obtained from an evaluation of ventricular arrhythmias in the electrocardiogram at rest. With the exception of exercise-induced ventricular tachycardia and fibrillation, no relation was found between ventricular arrhythmias and sudden death. Coronary bypass grafting does not decrease the frequency or severity of exercise-induced or resting ventricular arrhythmias. In patients with stable angina pectoris, with the exception of ventricular tachycardia and fibrillation, exercise-induced ventricular arrhythmias are poor predictors of sudden death. The data suggest that exercise-induced ventricular arrhythmias may not be related to ischemia but to other effects of exercise such as cardiac stimulation by catecholamines or other factors.

Angina Pectoris↗
PubMed1979

Two-dimensional echocardiographic features of bicuspid aortic valve.

The two-dimensional cross-sectional echocardiographic diagnosis of bicuspid aortic valves is described and compared with results of M-mode echocardiograms. Aortic valve anatomy was determined in 19 selected patients by angiography, and confirmed in five by direct surgical visualization. Using an eccentricity index (EI) of 1.3 or greater as diagnostic of bicuspid aortic valve, M-mode correctly identified anatomy in 14 of 19 valves (74 percent), although EI varied in several patients. For two-dimensional diagnosis of bicuspid aortic valve, short axis cross section was preferred, and criteria included number of cusps seen in real time motion, irregularity of folding of cusp margins, and location of commissural insertions. Two-dimensional echocardiography correctly identified anatomy in 18 of 19 valves (95 percent). Long axis cross section disclosed valvular doming in all 8 patients in whom doming was observed angiographically, correlating with hemodynamic findings. Two-dimensional echocardiography aids in the detection of bicuspid aortic valve in a suspected population, can give an estimate of valve gradients, and explains variability in M-mode findings. As such, two-dimensional echocardiography is a valuable tool in the noninvasive diagnosis of the bicuspid aortic valve.

Adolescent↗
PubMed1978

Idiopathic cardiomyopathy, age, and suppressor-cell dysfunction as risk determinants of lymphoma after cardiac transplantation.

A review of lymphomas developing in recipients of cardiac allografts has yielded significant risk factors. Frequency varied strikingly according to original cardiac disease: lymphoma developed in 6 of 37 patients with prior idiopathic cardiomyopathy (I.C.M.) but in one of 54 patients with prior coronary-artery disease (C.A.D.). All patients who developed lymphomas were aged under 40. Combination of both risk factors (I.C.M. and age less than 40) produces a sub-group with a highly significantly increased risk of lymphoma. I.C.M., but not C.A.D., is characterised by a defect in mitogen-induced mononuclear-cell suppressor activity. It is postulated that defective regulation in the immune systems of younger patients under chronic alloantigen stimulation may allow lymphoid proliferation to proceed to lymphoreticular malignancy. Immunosuppressive agents such as azathioprine may exert a co-oncogenic effect.

Adolescent↗
PubMed1978

Clinical electrophysiologic effects of tocainide.

The electrophysiologic properties of tocainide were evaluated by electrophysiologic studies in 11 patients before, during and after a constant intravenous infusion of the drug for 15 minutes. Peak plasma tocainide concentrations averaged 11.0 +/- 1.7 microgram/ml (SEM), range 3.7 to 22.7. AH, HV, QRS, QTc and RR intervals were measured every 5 minutes during sinus and atrial-paced rhythms and showed small changes which were not statistically significant for HV and QRS. Mild shortening of RR was significant (P less than 0.05) at 15 minutes only. AH tended to increase slightly for spontaneous (but not paced) rhythm, becoming significant at 15 minutes only (P less than 0.05). QTc decreased slightly, a change which was significant (P less than 0.05) for paced but not spontaneous rhythm. A progressive rise in mean arterial pressure occurred during infusion and persisted through 30 minutes (P less than 0.001). Comparison of electrophysiologic studies at 0 and 30 minutes showed decreased in mean effective refractory periods of atrium, A-V node, and right ventricle by 17, 22, and 23 msec, respectively (P less than 0.05, 0.01, 0.01). Functional refractory period of the A-V node showed an average decrease which was not significant. Sinus node recovery time and Wenckebach cycle length were unchanged. The drug was well tolerated in all 11 patients. Hypotension in a twelfth patient may or may not have been drug related. These results obtained at therapeutic plasma concentrations suggest qualitative similarities between the conduction system effects of tocainide and those published for lidocaine.

Aged↗
PubMed1978

The hemodynamic effects of intravenous tocainide in patients with heart disease.

In order to evaluate its hemodynamic actions, tocainide, a new orally effective antiarrhythmic drug, was given intravenously over a 15 minute period to 12 patients with compensated left ventricular dysfunction. Doses were 0.5 (4 patients) or 0.75 (8 patients) mg/kg/min. Hemodynamics and drug plasma concentrations were measured at the end and 15 minutes after the end of the infusion. Tocainide infusion produced small but statistically significant increases in the pulmonary and systemic vascular resistance, aortic and pulmonary arterial pressure, and left and right ventricular end-diastolic pressure. There was no significant change in left ventricular dp/dt, heart rate, or cardiac index. In patients with compensated left ventricular dysfunction, tocainide produces a small rise in vascular resistance and arterial pressure. Overall cardiac function is maintained with a small increase in left ventricular end-diastolic pressure.

Adult↗
PubMed1973

The enhancement of macrophage bacteriostasis by products of activated lymphocytes.

It was reported previously that the incubation of normal guinea pig macrophages with partially purified products of activated lymphocytes resulted in altered macrophage function including increased cell adherence to culture vessels, spreading, phagocytosis, and glucose carbon-1 oxidation. Studies reported here demonstrate that such macrophages also exhibit enhanced bacteriostasis. Lymphocytes were stimulated with concanavalin A, the culture supernatant was chromatographed over Sephadex G-100 and the fraction of mol wt 25,000-55,000, rich in lymphocyte mediators, was cultured with normal guinea pig macrophages for 1-3 days. Macrophages incubated with fractions from unstimulated lymphocyte cultures served as controls. The resulting macrophage monolayers were infected with Listeria monocytogenes. Macrophages incubated with mediator-rich fractions exhibited 2- to 10-fold enhanced bacteriostasis compared to controls. Further studies indicate that this enhancement was attributable to intrinsic changes in the macrophages and not simply a consequence of the number of macrophages on the monolayers. The studies support the concept that macrophage bacteriostasis can be enhanced by lymphocyte mediators. However, macrophages, which have been preincubated directly with sensitive lymphocytes and antigen exhibit even greater bacteriostasis and sometimes bactericidal capacity, suggesting that either a labile lymphocyte factor or direct lymphocyte macrophage interaction may also be involved in bactericidal activity.

Animals↗