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Biomedical subjects

R T Palac

Publications and source records attributed to R T Palac.

At least 19 recordsLinked to original sources
PubMed2001

Outcome of mild periprosthetic regurgitation detected by intraoperative transesophageal echocardiography.

OBJECTIVES: The goal of this study was to determine the outcome of trivial or mild periprosthetic regurgitation (PPR) identified by intraoperative transesophageal echocardiography (TEE). BACKGROUND: The clinical significance, natural history and correlates of trivial or mild PPR detected early after surgery are unknown. METHODS: Between 1992 and 1997, 608 consecutive patients underwent isolated aortic valve replacement or mitral valve replacement at Dartmouth-Hitchcock Medical Center. Of these, 113 patients (18.3%) were found to have trivial or mild PPR at surgery by TEE. Follow-up transthoracic echocardiograms (early TTEs) were obtained within six weeks of surgery in 99.0% of patients and late TTEs (mean 2.1 years) in 54.3%. Clinical, intraoperative and outcome variables associated with PPR were identified using t test, chi-square and logistic regression analyses. RESULTS: By univariate analysis, compared with patients without PPR, patients with PPR were older, of smaller body surface area (BSA), had degenerative valve disease more often and were more likely to receive a bioprosthetic valve. By multivariate analysis, smaller BSA and the use of a bioprosthesis were the strongest predictors of PPR (p < 0.01). At early TTE, PPR was not observed (n = 56) or remained unchanged (n = 44) in all patients. At late TTE, four patients were found to have progression of their PPR. All four patients had bioprosthetic valves. Two of these patients had endocarditis, and one had primary valvular degeneration. The fourth patient had progressive PPR. CONCLUSIONS: Trivial or mild PPR is a frequent finding on intraoperative TEE. Smaller body size and the use of a bioprosthetic valve are significantly associated with PPR. The clinical significance and natural history of PPR is benign in most cases.

Aged↗
PubMed1999

The clinical utility of adenosine in difficult to diagnose tachyarrhythmias.

BACKGROUND: The use of intravenous adenosine to help differentiate the origin of tachyarrhythmias has been suggested to be beneficial. However, the benefit of this intervention to physicians with different levels of training in electrocardiographic (ECG) interpretation is unknown. HYPOTHESIS: The purpose of the study was to determine whether intravenous adenosine improved the diagnostic accuracy of difficult to diagnose tachyarrhythmias when used by physicians with different levels of training in ECG interpretation. METHODS: We studied 28 consecutive patients presenting with wide and narrow complex tachyarrhythmias, in whom adenosine was given specifically for diagnostic purposes. Two groups of physicians, attending (n = 14) and housestaff (n = 10), reviewed each ECG before and after the administration of adenosine. RESULTS: For narrow complex tachyarrhythmias, neither physician group derived diagnostic benefit from the use of adenosine. However, for wide complex tachyarrhythmias, the diagnostic accuracy of the housestaff group significantly improved with the use of adenosine (pre = 54%, post = 70%, p < 0.01), while the attending physician group had no significant improvement (pre = 61%, post = 71%, p = NS). CONCLUSION: This study suggests that adenosine provides useful diagnostic information to physicians less experienced in ECG interpretation when presented with patients having wide complex tachyarrhythmias of uncertain origin.

Adenosine↗
PubMed1999

Color M-mode Doppler flow propagation velocity is a relatively preload-independent index of left ventricular filling.

Standard Doppler indexes of transmitral filling vary in response to alterations in left ventricular (LV) relaxation or preload. To determine whether color M-mode Doppler flow propagation velocity (vp), a new index of LV relaxation, is affected by preload, we obtained LV volumes, standard Doppler filling indexes, and vp in 20 patients at baseline, during Trendelenburg's position, inverse Trendelenburg's position, and after inhalation of amyl nitrite. LV end-diastolic volume decreased from 111 +/- 41 mL at baseline and 116 +/- 43 mL during Trendelenburg's position, to 104 +/- 40 during inverse Trendelenburg's maneuver and 92 +/- 33 mL after inhalation of amyl nitrite (P <.0001). Peak early filling velocity decreased from 79 +/- 19 cm/s and 90 +/- 20 cm/s to 73 +/- 22 cm/s and 64 +/- 20 cm/s, respectively (P < 0.0001). In contrast, no significant changes were found in vp (48 +/- 24 and 50 +/- 26 cm/s vs 48 +/- 25 and 48 +/- 25 cm/s). We conclude that vp is not affected significantly by preload. Thus vp may provide a more reliable and independent assessment of LV relaxation.

Adult↗
PubMed1997

Propafenone-induced drug fever in the absence of agranulocytosis.

Propafenone is an antiarrhythmic drug used in the treatment of life-threatening ventricular tachyarrhythmias. Adverse reactions necessitating discontinuation of the medication are common. Propafenone-induced drug fever has not been definitively proven. We present a case report of drug fever secondary to propafenone, confirmed with rechallenge.

Agranulocytosis↗
PubMed1991

Ribose infusion accelerates thallium redistribution with early imaging compared with late 24-hour imaging without ribose.

To determine if early (4-h) thallium-201 imaging with ribose infusion would enhance detection of thallium redistribution better than late (24-h) imaging without ribose infusion, 15 patients with coronary artery disease underwent thallium stress tests by both methods within 2 weeks. All 15 patients had quantitative coronary angiography. After immediate postexercise planar imaging during the first of two exercise tests, patients were randomized to receive either intravenous ribose (3.3 mg/kg per min) or a control infusion of saline solution for 30 min. Images performed at 4 h for the ribose study were compared with those at 24 h for the saline control study. During the second test, exercise was carried to the same rate-pressure product and each patient received the opposite infusion. Four-hour postexercise images after ribose infusion identified 21 reversible defects not seen in the 24-h saline study. Three reversible defects were seen only in saline studies, but not with ribose at 4 h (p less than 0.01); 15 reversible defects were seen with both tests. When analyzed with respect to the 31 vascular territories supplied by a coronary artery with a greater than 50% stenosis, 8 territories had reversible defects present in the ribose but not the saline study and the saline study did not demonstrate reversible defects in territories that were seen in the ribose study (p less than 0.01). In 14 of these territories, reversible defects were seen with both tests. In 6 of 15 patients, additional vascular territories with reversible defects were identified after ribose infusion. It is concluded that ribose enhances the detection of thallium redistribution at 4 h compared with 24-h control images in patients with coronary artery disease and, therefore, substantially improves the identification of viable ischemic myocardium.

Aged↗
PubMed1991

Ribose facilitates thallium-201 redistribution in patients with coronary artery disease.

To investigate whether i.v. infusion of ribose, an adenine nucleotide precursor, postischemia facilitates thallium-201 (201Tl) redistribution and improves identification of ischemic myocardium in patients with coronary artery disease (CAD), 17 patients underwent two exercise 201Tl stress tests, performed 1-2 wk apart. After immediate postexercise planar imaging, patients received either i.v. ribose (3.3 mg/kg/min x 30 min) or saline as a control. Additional imaging was performed 1 and 4 hr postexercise. Reversible defects were identified by count-profile analysis. Significantly more (nearly twice as many) reversible 201Tl defects were identified on the post-ribose images compared to the post-saline (control) images at both 1 and 4 hr postexercise (p less than 0.001). Quantitative analyses of the coronary arteriogram was available in 13 patients and confirmed that the additional reversible defects were in myocardial regions supplied by stenosed arteries. We conclude that ribose appears to facilitate 201Tl redistribution in patients with CAD and enhances identification of ischemic myocardium.

Aged↗
PubMed1990

Progression of native coronary artery disease at 10 years: insights from a randomized study of medical versus surgical therapy for angina.

Repeat coronary angiography was performed in 42 patients 10 years after randomization to medical (n = 21) or surgical (n = 21) therapy for chronic angina. The native coronary arteries were classified into 15 angiographic segments and 3 arterial trunks for analysis of progression of coronary artery disease. The incidence rate of disease progression in coronary segments was 24% and 28% in medically and surgically treated patients, respectively (p = NS). Grafted segments showed a 38% rate of disease progression, which was higher than the 18% rate of for nongrafted segments (p less than 0.001) and the overall rate of 24% for medically treated patients (p less than 0.01). Similarly, 29 (94%) of 31 grafted arteries exhibited disease progression compared with 19 (59%) of 32 nongrafted arteries (p less than 0.01) and 42 (67%) of 63 arteries in medically treated patients (p less than 0.01). In grafted vessels, disease progression occurred more often in arteries proximal (84%) to the anastomosis than in arteries distal (16%) to graft insertion (p less than 0.001). Progression occurred in 46% of proximal segments compared with 23% of distal segments (p less than 0.02). Progression was seen in 23 (55%) of 43 segments with an occluded graft compared with 30 (31%) of 96 segments with a patent graft (p less than 0.02). Ten years after randomization, medically and surgically treated patients showed a comparable rate of disease progression in coronary segments. However, surgical therapy appeared to significantly accelerate atherosclerotic progression in the grafted vessels, especially in the proximal portions. Occluded grafts also correlated with an adverse effect on disease progression.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1989

Detection of experimental atherosclerosis with indium-111 radiolabelled hematoporphyrin derivative.

It has been observed that atherosclerotic lesions (AL) concentrate certain porphyrins. We evaluated the usefulness of 111In-labelled Photofrin II (PFII), a porphyrin derived from haematoporphyrin derivative, for detection of experimental AL in cholesterol fed rabbits. Three groups of rabbits were studied: non-atherosclerotic (n = 3), 6 and 12 week cholesterol fed (n = 4, 3). 111In-PFII was injected intravenously and gamma camera images were obtained at 24 and 48 h. At 48 h, explanted aortas were also imaged. Aortic arch (AA) to background (BKG) count ratios were calculated from images of the whole body and explanted aortas. AA/BKG ratios were significantly higher in the 12 week cholesterol fed rabbits (3.9 +/- 0.72 at 24 h) and (4.0 +/- 0.67 at 48 h) than in the non-atherosclerotic rabbits (2.2 +/- 0.07 at 24 h) and (2.3 +/- 0.18 at 48 h) (p less than 0.05). The AA/BKG ratio for the explanted aortas showed similar results. Additionally, in two of three 12 week cholesterol fed rabbits, focal count deposition was visible on the whole animal images at the site of aortic arch atherosclerosis. We conclude that 111In-PFII concentrates in AL as early as 24 h after injection and has the potential to be used as an imaging agent for experimental atherosclerosis.

Animals↗
PubMed1989

Effect of thallium-201 blood levels on reversible myocardial defects.

To determine if 201Tl plasma blood levels correlate with the presence of reversible myocardial defects during exercise testing, 14 patients with stable coronary artery disease underwent two separate exercise 201Tl stress tests. Between initial and delayed imaging, on one test the patients drank an instant breakfast drink (eating) and on the other they drank an equivalent volume of water as a control (H2O). Thallium-201 imaging was performed immediately postexercise, immediately after eating/H2O and 210 min after eating/H2O. Between initial and immediate post eating/H2O images 201Tl reversible defects occurred in 27/38 regions in the H2O test versus 15/38 regions in the eating test (p = 0.02). Over this early time period, plasma 201Tl activity was significantly higher in the H2O test than eating test (p less than 0.05). In conclusion, early reversal of 201Tl defects may, in part, be the result of higher plasma 201Tl activity early after initial postexercise 201Tl imaging.

Angina Pectoris↗
PubMed1989

Iodine-123 metaiodobenzylguanidine imaging of the heart in idiopathic congestive cardiomyopathy and cardiac transplants.

Iodine-123 metaiodobenzylguanidine ([123I]MIBG) is a norepinephrine analog which can be used to image the sympathetic innervation of the heart. In this study, cardiac imaging with [123I]MIBG was performed in patients with idiopathic congestive cardiomyopathy and compared to normal controls. Initial uptake, half-time of tracer within the heart, and heart to lung ratios were all significantly reduced in patients compared to normals. Uptake in lungs, liver, salivary glands, and spleen was similar in controls and patients with cardiomyopathy indicating that decreased MIBG uptake was not a generalized abnormality in these patients. Iodine-123 MIBG imaging was also performed in cardiac transplant patients to determine cardiac nonneuronal uptake. Uptake in transplants was less than 10% of normals in the first 2 hr and nearly undetectable after 16 hr. The decreased uptake of MIBG suggests cardiac sympathetic nerve dysfunction while the rapid washout of MIBG from the heart suggests increased cardiac sympathetic nerve activity in idiopathic congestive cardiomyopathy.

3-Iodobenzylguanidine↗
PubMed1988

The effects of rapid volume expansion on the right and left cardiac filling pressures after coronary artery bypass surgery.

Rapid volume expansion is a diagnostic procedure which can reveal typical hemodynamics of pericardial constriction in patients with pericardial disease who have normal hemodynamics in their baseline state. We studied 20 patients with previous coronary artery bypass surgery in order to determine whether this operation results in some degree of pericardial constriction which could be demonstrated by rapid volume expansion. After infusing 1 L of physiologic saline solution over six minutes, the right atrial pressure increased by 5 +/- 2 mm Hg, the right ventricular diastolic pressure by 4 +/- 3 mm Hg, the pulmonary capillary wedge pressure by 7 +/- 3 mm Hg, and the left ventricular diastolic pressure by 7 +/- 4 mm Hg (mean +/- SD). Equalization of the left and right cardiac pressures was not observed, and the normal respiratory variation of the pressures was not altered by rapid volume expansion. Thus, the pericardial manipulation associated with the performance of coronary artery bypass surgery does not commonly result in the development of subclinical pericardial constriction.

Adult↗
PubMed1987

Effect of eating on thallium-201 myocardial redistribution after myocardial ischemia.

To determine whether eating a high-carbohydrate meal between initial and delayed postexercise thallium-201 (Tl-201) imaging affects detection of Tl-201 redistribution during exercise stress testing, 16 patients with stable angina performed 2 Tl-201 treadmill exercise stress tests within a 14-day interval. Immediately after initial postexercise imaging, patients either drank a commercially available instant breakfast preparation for the intervention test or drank an equivalent volume of water for the control test. Comparable exercise workloads were achieved by exercising patients to the same heart rate for both tests. The order of the 2 (intervention and control) tests were randomized. All patients had at least 1 region of Tl-201 myocardial redistribution on either their eating or control test scans, although only 7 of the 16 had positive treadmill exercise test responses. Forty-six regions showing Tl-201 myocardial redistribution were identified in all 144 regions examined. Significantly more of these regions were identified on control test scans than on eating test scans: 11 of 46 on both test scans, 6 of 46 only on eating test scans and 29 of 46 only on control scans (p less than 0.001). Consistent with results of the quantitative regional analysis, the percentage of Tl-201 clearance over 4 hours in the 46 Tl-201 myocardial redistribution regions was 39 +/- 8% for the eating tests and 29 +/- 8% for control tests (mean +/- standard deviation, p less than 0.003). In 4 patients diagnosis of transient ischemia would have been missed because their 14 Tl-201 myocardial redistribution regions were detected only on the control test scans.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Thallium scintigraphy during dobutamine infusion: nonexercise-dependent screening test for coronary disease.

Exercise thallium scintigraphy has proven to be a sensitive method for detecting coronary artery disease (CAD). However, early redistribution of thallium and inadequate exercise can reduce its sensitivity. In this study, dobutamine was infused in incremental doses (5, 10, 15, and 20 micrograms/kg/min) in 24 patients being evaluated for chest pain. Thallium scintigraphy was completed during the maximum dose of dobutamine tolerated and repeated 4 hours later. Significant CAD was present in 16 patients; the remaining eight had normal coronaries. Exercise ECG was obtained in 23 patients. During dobutamine thallium scintigraphy, reversible perfusion defects occurred in 15 of 16 CAD and in one of eight non-CAD patients, resulting in a sensitivity of 94% and a specificity of 87%. Exercise ECG had a sensitivity of 60% and a specificity of 63%. We conclude that: (1) dobutamine thallium scintigraphy appears to be a sensitive method for detecting significant CAD and provided a more sensitive screening test than exercise ECG; (2) dobutamine thallium scintigraphy is especially useful in patients who cannot exercise; and (3) because imaging occurs during dobutamine infusion, the problem of early redistribution may be mitigated.

Catecholamines↗