Biomedical subjects
H J Swan
Publications and source records attributed to H J Swan.
The rt-PA versus streptokinase controversy--IV.
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The pulmonary artery catheter.
First developed more than 20 years ago as a research tool for investigations of myocardial infarction, the pulmonary artery or Swan-Ganz catheter has gained general usage as a valuable clinical tool. Its development paralleled the rapid growth of technological advancements in clinical medicine. Rapid incorporation of technological advancements into clinical practice, however, is not without risk. Care must be taken to assure that clinicians possess the understanding of both basic concepts and requisite hardware to provide quality patient care. Equipment selection and calibration, patient selection, data interpretation, potential complications, troubleshooting, and procedure limitations must all be considered. Broader application of the Swan-Ganz catheter in surgery, anesthesiology, and critical care as well as in cardiology has provided information on hemodynamics that has had considerable impact on diagnostics as well as on therapy for patients with a wide variety of clinical conditions.
New method for monitoring pulmonary artery catheter location.
OBJECTIVE: To test the ability of a modified pulmonary artery (PA) monitoring catheter to detect distal catheter migration. DESIGN: Prospective nonrandomized trial. PATIENTS: Surgical ICU patients requiring invasive hemodynamic monitoring. INTERVENTIONS: Eight patients received PA catheters modified to include a right ventricular (RV) pressure monitoring port located 7 cm from the tip. Fifteen patients received catheters with an RV port located 10 cm from the tip. Guided by the RV port pressure waveform, catheters were initially positioned so that the RV port was located just proximal to the pulmonic valve. MEASUREMENTS AND MAIN RESULTS: Pulmonary capillary occlusion pressure (PAOP) could not be obtained in six of the eight patients receiving the 7-cm RV port catheter unless the RV port was advanced into the PA. PAOP was consistently obtained in all 15 patients receiving the 10-cm RV port catheter, with the RV port positioned in the RV. Chest radiographs confirmed a central PA catheter position. In this group, distal migration of the catheter occurred 14 times in eight patients, as detected by appearance of a PA pressure waveform at the RV port. Distal migration was corrected by withdrawal of the catheter until an RV waveform reappeared at the RV port. CONCLUSIONS: We conclude that distal catheter migration occurs frequently with PA monitoring catheters, but can be detected at the bedside with a catheter modified to include an RV port 10 cm from the tip. This new catheter may add a margin of safety to PA monitoring and lower its overall cost by eliminating the need for chest radiographs ordered solely to confirm catheter tip location.
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.
Ambulatory monitoring and silent myocardial ischemia: have the basics been done?
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Enoximone in chronic heart failure.
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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)
Acute myocardial infarction: a failure of timely, spontaneous thrombolysis.
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Hemodynamic monitoring in anesthesiology--past, present and future.
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Getting to the heart of the matter. Interview by RL Reece.
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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.
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)
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)
Application of high technology in the diagnosis and treatment of the elderly.
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Cardiology: a transatlantic view (2).
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Future directions in cardiology.
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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.