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Biomedical subjects

J A Ronan

Publications and source records attributed to J A Ronan.

At least 19 recordsLinked to original sources
PubMed1984

Effects of nadolol on the spontaneous and exercise-provoked heart rate of patients with chronic atrial fibrillation receiving stable dosages of digoxin.

Nadolol, a long-acting beta-adrenergic-blocking agent, was evaluated in 20 patients with chronic atrial fibrillation by means of a randomized, double-blind, crossover study. Patients were required either to demonstrate resting heart rates in excess of 80 bpm or to show a rate of 120 bpm or an increment of greater than 50 bpm during mild treadmill exercise provocation (3 minutes, 1.75 mph, 10% grade). With placebo the group averaged a heart rate of 92 +/- 19 bpm, determined by 24 hours of ambulatory ECG recordings; this rate was significantly reduced to 73 +/- 16 bpm (p less than 0.001) with nadolol (mean dosage, 87 +/- 43 mg/day). During standardized exercise testing, heart rates increased to 153 +/- 26 bpm with placebo and to 111 +/- 24 bpm with nadolol (p less than 0.001), representing 65% and 52% increments, respectively. Digoxin blood levels averaged 0.8 +/- 0.5 ng/ml with placebo and were similar with nadolol (0.9 +/- 0.4; p = NS). Total exercise time on a modified Bruce treadmill protocol was 466 +/- 143 seconds with placebo and was significantly decreased by nadolol (380 +/- 143; p less than 0.01). During initial dose titration with nadolol, one patient was dropped from study for intolerable fatigue and one for worsened claudication. No patients were dropped from the double-blind treatment periods, although two patients receiving nadolol and one patient receiving placebo complained of moderate fatigue. We conclude that nadolol is a safe and effective agent for the control of spontaneous and exercise-provoked heart rates in patients with chronic atrial fibrillation who were already receiving digoxin treatment.

Adrenergic beta-Antagonists↗
PubMed1983

A new oral slow release form of isosorbide dinitrate. Effect on the hemodynamics and exercise capacity of patients with angina.

To assess the bioavailability of a new oral and slow release form of isosorbide dinitrate (ISDN-SR), we evaluated 12 patients with confirmed coronary artery disease, chronic stable angina pectoris and abnormal maximal exercise tests (angina-limited and associated with greater than or equal to 0.1 mV ST displacement). Each patient was known to have an increased exercise time after 0.4 mg of sublingual nitroglycerin. Patient responses to exercise on the treadmill at two, four, six, and eight hours after the double-blind administration of 40 mg of ISDN-SR were compared to an identical placebo. It is concluded that 40 mg of this slow release form of isosorbide dinitrate is bioavailable for at least eight hours as demonstrated by significantly improved exercise capacity of the majority (64 percent) of angina patients in this study, each of whom demonstrated anginal limitation to exercise and favorable responses to 0.4 mg of sublingual nitroglycerin.

Administration, Oral↗
PubMed1981

Accuracy of angiographic determination of left main coronary arterial narrowing. Angiographic--histologic correlative analysis in 28 patients.

To evaluate the accuracy of coronary angiography in identifying severe narrowing of the left main coronary artery (LMCA), the degree of narrowing observed by angiography was compared to that observed at necropsy in 28 patients with symptomatic coronary heart disease in whom angiography had been performed within 40 days of death. The angiograms were evaluated independently by three experienced angiographers. In 20 of the 28 patients (71%), the degree of narrowing of the LMCA was either underestimated (13 patients) or overestimated (10 patients) by two or three of three angiographers; of 84 angiographic judgments made by the three angiographers in the 28 patients, 54 (64%) were underestimates (33 judgments, 39%) or overestimates (21 judgments, 25%) of the degree of LMCA narrowing. Of 12 LMCAs narrowed 76-100% in cross-sectional area at necropsy, six were underestimated at preoperative angiography by two or three of three angiographers; of 12 LMCAs narrowed 51-75% in cross-sectional area at necropsy, all 12 were either under- or overestimated angiographically by two or three of three angiographers; of four LMCAs narrowed 26-50% in cross-section at necropsy, two were overestimated by two of three angiographers. Thus, angiographic determination of degrees of narrowing of the LMCA during life is subject to considerable error. The angiographic errors appear to have resulted primarily from the presence of atherosclerotic plaque in the LMCA and an insufficient number of angiographic projections.

Adult↗
PubMed1980

Pseudoischemic "false positive" S-T segment changes induced by hyperventilation in patients with mitral valve prolapse.

Hyperventilation-induced S-T segment changes that simulate myocardial ischemia have previously been noted, but the origin of this electrocardiographic finding has never been defined. To investigate further the basis for this response, the records were reviewed of 1,678 consecutive patients who underwent forced hyperventilation for 90 seconds and treadmill exercise testing. Twenty-eight patients (1.7 percent) were identified in whom hyperventilation resulted in ischemic-appearing S-T segment changes, and follow-up was possible in 21 (17 women, 4 men). Of the 21 patients, 16 (76 percent), including 15 (88 percent) of the 17 women, had evidence of mitral valve prolapse, 6 on auscultation alone, 2 on echocardiography alone and 6 with a combination of studies. Ten of the 21 patients had a negative exercise test; of the 11 patients who had a positive exercise test, only 1 had angiographic evidence of coronary arterial narrowing. The finding of ischemic-appearing S-T segment changes in response to forced hyperventilation has a high predictive value for the presence of mitral valve prolapse, particularly in women. The possible association of autonomic factors and mitral valve prolapse in the pathogenesis of an abnormal response to hyperventilation is discussed.

Adult↗
PubMed1979

Systolic click from a Swan-Ganz catheter: phonoechocardiographic depiction of the underlying mechanism.

Although echocardiographic manifestations of Swan-Ganz catheters have received increasing attention, auscultatory sequelae have not previously been described. In the patient described in this report, insertion of a Swan-Ganz catheter resulted in a loud mid systolic click; removal of the catheter eliminated the click. Simultaneous phonoechocardiograms suggest that the click resulted from crisp contact of the catheter against the ventricular septum. Catheter momentum was enhanced by wide excursion and systemic pressures in the right ventricle; paradoxical motion of the septum during systole may have accentuated the force of its contact with the catheter.

Cardiac Catheterization↗
PubMed1975

The angiotensin infusion test as a method of evaluating left ventricular function.

Fifteen patients had left ventricular function measured by the angiotensin infusion method. Seven patients had no evidence of heart disease, and eight patients had angina pectoris and coronary arteriographic evidence of coronary disease without congestive heart failure. During angiotensin infusion, those patients without heart disease had a decrease in cardiac index (average, 0.63 L. per minute per square meter) and a decrease in heart rate (average, 12 beats per minute.) The ventricular function curve had a poor SWI response in four of the seven subjects. The patients with coronary artery disease also had a reduction in cardiac index during angiotensin (average, 0.44 L. per minute per square meter) and the heart rate was unchanged in four subjects, increased in two subjects, and decreased in two subjects. Six of the subjects had flat or descending slopes on the function curve, and in one subject there was only a very gradual ascending slope. Many of the curves of both groups looked similar so that the function curves did not differentiate between those patients with or without heart disease. The mechanism for production of bradycardia, reduction of cardiac output, and depressed function curves with angiotensin is multifactorial, but is probably due to the baroreceptor reflex response, the increase in coronary artery resistance, and possible to the direct effect of increased left ventricular afterload itself. The ventricular response to angiotensin is so variable that the angiotensin infusion method of evaluating ventricular function is not reliable.

Adolescent↗
PubMed1975

Radiographic appearance of the thorax in systolic click-late systolic murmur syndrome.

The posteroanterior and lateral chest X-ray films of 64 consecutive patients with an isolated systolic click (55 patients) or a systolic click with a late systolic murmur (9 patients) showed a striking frequency of thoracic skeletal abnormalities. There were 50 female and 14 male subjects. The average age of the female subjects was 36.7 years (range 13 to 67), that of the male subjects 39.7 years (range 17 to 56). Seventy-two percent of the female and 78 percent of the male subjects had an anteroposterior/transverse thoracic ratio less than the mean ratio in a small population. Bony abnormalities such as pectus excavatum, straight thoracic spine and scoliosis occurred alone or in a combination in 31 of the 50 female patients (62 percent) and in 8 of the 14 male patients (57 percent). Overall, 39 of the 64 patients (61 percent) had at least one of the skeletal abnormalities. Scoliosis occurred in 25 subjects (39 percent) and was mild in 19. A "straight back" was found in 15 (23 percent) and pectus excavatum in 7 patients (11 percent). The explanation for these findings is not apparent. Thoracic cage abnormalities should be included as one of the nonauscultatory features of the systolic click-late systolic murmur syndrome.

Adolescent↗