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Biomedical subjects

H J Swan

Publications and source records attributed to H J Swan.

At least 37 records · Page 2Linked to original sources
PubMed1990

Can heart failure be prevented, delayed, or reversed?

A review of the clinical course of chronic heart failure demonstrates that current outcomes remain highly unsatisfactory both in mortality and perhaps more important in morbidity. The extraordinary satisfactory functional responses seen in patients who undergo cardiac transplantation clearly identify the primary cause as the status of the heart itself, whatever the pathophysiologic adjustments of the neuroendocrine system, and interventions of the wide variety of drugs. Since donor hearts are unlikely to be available even from younger sufferers of these clinical syndromes, prevention must be the hallmark. Protection of the viability of myocytes, such as in acute myocarditis and acute infarction, is essential. Myocardial collagen undergoes continual synthesis, and production is greatly stimulated in the presence of hypertrophy caused by increased wall stress. It is possible that excess collagen is intimately involved with diastolic ventricular dysfunction, but that this may be a reversible process if the collagen-producing stimulus is removed. Thus reduction in wall stress and reversibility of ventricular hypertrophy appear to be promising directions. However, to limit the catastrophic effects of chronic heart failure, early recognition of the precursors of these syndromes, prevention of progression, and surgical intervention in valvular heart disease at an optimal point in time are essential.

Heart Diseases↗
PubMed1989

Exercise-induced ischemia in the streptokinase-reperfused myocardium: relationship to extent of salvaged myocardium and degree of residual coronary stenosis.

To assess the functional significance of residual stenosis at the site of the thrombolysed infarct-related coronary artery, 37 patients underwent exercise radionuclide ventriculography or stress-redistribution thallium-201 scintigraphy at an average of 7 weeks following streptokinase therapy during evolving myocardial infarction. The size of the initially jeopardized myocardium and the salvaged myocardium were quantitated on thallium-201 studies obtained immediately before and 10 days after streptokinase infusion. Exercise-induced ischemia (defined by reversible thallium-201 perfusion defects or stress-induced deterioration of regional wall motion) in the reperfused myocardium was absent in 46% of patients and was present in different degrees in the remaining 54%. A significantly lower proportion of patients, however, showed exercise-induced chest pain and/or ST segment depression (10% and 20%, respectively). By stepwise multiple logistic regression analysis, the quantitatively determined size of the salvaged myocardium (398 units versus 65 units, p less than 0.01) and the ratio of the salvaged myocardium/extent of initially jeopardized myocardium (70% versus 28%, p less than 0.01) were both independent predictors of stress-induced ischemia, whereas the extent of initially jeopardized myocardium (585 units versus 407 units, p = NS), incidence of greater than or equal to 99% coronary stenosis (37% versus 46%, p = NS), and ischemic time (160 versus 196 minutes, p = NS) did not provide additional predictive information. We conclude that exercise-induced ischemia, which is frequently present in the streptokinase-reperfused myocardium, cannot be detected accurately by exercise-induced chest pain or ST segment depression, nor can it be predicted by the severity of residual coronary stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Adult cardiology and the expanding supply of physicians.

The number of cardiologists can be projected with considerable accuracy into the next century. The total cardiology pool of physicians will increase until the year 2015 at which time those entering and leaving the pool will come into equilibrium. At that time the ratio of active cardiologists to the population will have greatly increased. This nation's future need for cardiologists is difficult to assess with any degree of precision. Therefore, this is the time for updating practice profile studies. Such studies today could be formulated in a manner to provide more detailed information on the cardiologist's daily activities. In addition, a data base developed through methodology such as the consensus formation approach must be developed and updated on a periodic basis. Through such analyses it will be possible to quantitate the future needs of cardiovascular manpower.

Adult↗
PubMed1988

Patient monitoring.

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Monitoring, Physiologic↗
PubMed1987

The clinical significance of exercise-induced left ventricular wall motion abnormality occurring at a low heart rate.

We studied the relationship between the heart rate at the time of onset of exercise-induced wall motion abnormality and the severity of coronary artery disease in 89 patients who underwent exercise equilibrium radionuclide ventriculography as part of their evaluation for coronary artery disease. Segmental wall motion was scored with a five-point system (3 = normal; -1 = dyskinesis); a decrease of one score defined the onset of wall motion abnormality. The onset of wall motion abnormality at less than or equal to 70% of maximal predicted heart rate had 100% predictive accuracy for coronary artery disease and higher sensitivity than the onset of ischemic ST segment depression at similar heart rate during exercise: 36% (25 of 69 patients with coronary disease) vs 19% (13 of 69 patients), p = 0.01. Wall motion abnormality occurring at less than or equal to 70% of maximal predicted heart rate was present in 49% of patients (23 of 47) with critical stenosis (greater than or equal to 90% luminal diameter narrowing), and in only 5% of patients (2 of 42) without such severe stenosis, p less than 0.001. The sensitivity of exercise-induced wall motion abnormality occurring at a low heart rate for the presence of severe coronary artery disease was similar to that of a deterioration in wall motion by more than two scores during exercise (49% vs 53%) or an absolute decrease of greater than or equal to 5% in exercise left ventricular ejection fraction (49% vs 45%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Transient ischemic dilation of the left ventricle on stress thallium-201 scintigraphy: a marker of severe and extensive coronary artery disease.

On exercise thallium-201 scintigraphy, it has been noted that the size of the left ventricle is sometimes larger on the immediate poststress image than on the 4 hour redistribution image; this phenomenon has been termed transient ischemic dilation of the left ventricle. The angiographic correlates of this finding were assessed in 89 consecutive patients who underwent both stress-redistribution thallium-201 scintigraphy and coronary arteriography. A transient dilation ratio was determined by dividing the computer-derived left ventricular area of the immediate postexercise anterior image by the area of the 4 hour redistribution image. In patients with a normal coronary arteriogram or nonsignificant coronary stenoses (less than 50%), the transient dilation ratio was 1.02 +/- 0.05 and, therefore, an abnormal transient dilation ratio was defined as greater than 1.12 (mean + 2SD). The transient dilation ratio was insignificantly elevated in patients with noncritical coronary artery disease (50 to 89% stenosis) (1.05 +/- 0.05) and in patients with critical stenosis (greater than or equal to 90%) of only one coronary artery (1.05 +/- 0.05). In contrast, in patients with critical stenoses in two or three vessels, the transient dilation ratio was significantly elevated (1.12 +/- 0.08 and 1.17 +/- 0.09, respectively; p less than 0.05 compared with all other patient groups). An abnormal transient dilation ratio had a sensitivity of 60% and a specificity of 95% for identifying patients with multivessel critical stenosis and was more specific (p less than 0.05) than were other known markers of severe and extensive coronary artery disease, such as the presence of multiple perfusion defects or washout abnormalities, or both.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Prospective evaluation of ultrafast cardiac computed tomography for determination of coronary bypass graft patency.

Twenty-five consecutive patients with 68 independent (single distal anastomosis) saphenous vein aortocoronary and 12 internal mammary bypass grafts (27 to left anterior descending, 10 to diagonal, 23 to left circumflex, 20 to right coronary artery) entered a reader-blinded, prospective, standardized study to establish the accuracy of ultrafast (cine) cardiac computed tomography (CT) for determining graft patency compared with invasive angiography. All patients underwent imaging after injection of 35 to 45 ml of meglumine diatrizoate (Renografin-76; 7 to 9 ml/sec for 5 sec) into an arm vein. Electrocardiographically triggered images were acquired over eight to 16 tomographic levels at 1 cm intervals from aortic arch to mid left ventricle. Criteria for graft patency were contrast opacification on at least two noncontinguous levels and contrast density-time curves morphologically similar to that of the aorta. Ultrafast CT correctly determined that 46 of 48 bypass grafts were patent and 31 of 32 were occluded (sensitivity, specificity, and accuracy 96%, 97%, and 96%); there were no interpretation errors in 23 (92%) of the 25 patients. Accuracy was independent of vessel bypassed and not different for saphenous veins (96%) compared with internal mammary bypasses (100%). This study establishes a 20 min outpatient intravenous injection technique that is highly accurate for determining patency of coronary artery bypass grafts.

Coronary Angiography↗
PubMed1986

Variable spectrum and prognostic implications of left and right ventricular ejection fractions in patients with and without clinical heart failure after acute myocardial infarction.

To determine the spectrum and prognostic implications of left and right ventricular (LV and RV) ejection fractions (EFs) in acute myocardial infarction (AMI), radionuclide ventriculography was performed in 114 consecutive patients, admitted without (Killip class I, 78 patients) or with (killip class II, 36 patients) clinical signs of pulmonary congestion within 24 hours of onset of symptoms of a transmural AMI. Mean LVEF was significantly lower in patients in Killip class II than in those in class I (0.32 +/- 0.11 vs 0.46 +/- 0.15, p less than 0.001) and in patients with anterior than inferior AMI (0.34 +/- 0.11 vs 0.52 +/- 0.14, p less than 0.001). Of the 36 patients with a severely depressed (0.30 or less) LVEF, 15 (42%) were in Killip class I. Mean RVEF did not differ significantly between Killip class I and II patients (0.42 +/- 0.11 vs 0.40 +/- 0.12, difference not significant) but was significantly lower in patients with inferior than anterior AMI (0.38 +/- 0.09 vs 0.44 +/- 0.11, p = 0.005). In patients with inferior AMI, a depressed RVEF (0.38 or less) was associated with a normal LVEF in 30% and a depressed LVEF in 20%, whereas in those with anterior AMI, a depressed RVEF, observed in 25% of patients, occurred only in association with a depressed LVEF.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

A model for assessing the sensitivity and specificity of tests subject to selection bias. Application to exercise radionuclide ventriculography for diagnosis of coronary artery disease.

A probabilistic model was developed which allows one to estimate sensitivity and specificity of diagnostic tests for coronary artery disease without reference to angiography. The feasibility of the model was evaluated first in a series of computer simulations, and the model was then applied to the assessment of ejection fraction in 933 patients without prior myocardial infarction who underwent exercise radionuclide ventriculography. In 196 patients who were referred to angiography, the conventional abnormal ejection fraction criterion--an absolute rise of less than 0.05 with exercise--had a sensitivity of 79% and a specificity of 68% when referenced to coronary angiography. In 737 patients who were not referred for angiography and who were analyzed instead by our probabilistic model, sensitivity was 63% (p = 0.004 compared to that in the 119 angiographically diseases patients) and specificity was 79% (p = 0.036 compared to that in the 77 angiographic normals). Both the higher sensitivity and lower specificity in the catheterized patients are consistent with a preferential referral of positive test responders to angiography, and of negative test responders away from angiography. The distortion of test sensitivity and specificity which results from this selection bias can be circumvented by substituting a probabilistic estimate of disease for conventional angiographic ascertainment.

Adult↗
PubMed1986

Should the intent of testing influence its interpretation?

A test is often interpreted as "normal" or "abnormal" by a single criterion, regardless of the intent of testing. The discriminate accuracy of this convention was critically analyzed using information content (I), likelihood ratio and the area under the receiver-operating characteristic curve. Three ejection fraction variables were assessed--ejection fraction at rest, exercise ejection fraction and the change in ejection fraction from rest to exercise--each relative to three intentional goals: diagnosis of coronary artery disease in 929 patients without previous myocardial infarction, prediction of multivessel disease in these same 929 patients and prediction of multivessel disease in 507 patients with previous myocardial infarction. The information content of exercise ejection fraction (IEX) was higher than for ejection fraction at rest (IR) or for the change from rest to exercise (IEX-R), and was relatively constant regardless of the goal of testing. In contrast, neither IR nor IEX-R was constant. IR was lowest for diagnosis of coronary artery disease, whereas IEX-R was highest for this same goal. These empiric observations are consistent with the quantitative relation predicted by information theory: IEX = IR + IEX-R. Thus, ejection fraction at rest has little discriminate value relative to the diagnosis of coronary artery disease, but does have value in evaluating the extent of disease in patients after myocardial infarction. Exercise ejection fraction and change in ejection fraction are nearly equally useful for purposes of diagnosis, whereas the former is most useful for functional evaluation in postinfarction patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗