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Biomedical subjects

N J Weissman

Publications and source records attributed to N J Weissman.

63 records · Page 4Linked to original sources
PubMed1995

Dynamic expansion of the coronary arteries: implications for intravascular ultrasound measurements.

The majority of coronary artery blood flow occurs in diastole; however, systolic epicardial coronary artery expansion has been described. With the advent of intravascular ultrasound, precise measurements of arterial structures with excellent spacial and temporal resolution are now readily available. However, the effect of dynamic expansion of the coronary arteries on routine intravascular ultrasound measurements has not been assessed. The purpose of this study was to determine in vivo the presence, timing, and extent of dynamic changes in the coronary arteries and saphenous vein grafts and to assess their implications for intravascular ultrasound measurements. Intravascular ultrasound images were obtained with simultaneous electrocardiographic monitoring in 202 coronary artery and 50 saphenous vein graft sites in 32 patients with varying plaque burden and morphologic features. Arterial, luminal, and plaque area were measured at end-diastole and early, mid-, and end-systole. Coronary luminal diameter increased 2.1%; luminal area increased 8.1%; arterial area increased 3.7%; and plaque area decreased 4.9% during mid and late systole (p < 0.01). There was no detectable cyclic change in saphenous vein graft dimensions. In coronary arteries there was significant systolic expansion of the artery and lumen and systolic thinning of the plaque. The magnitude of dynamic luminal area change was greater than the variability in measurement and thus warrants gating to the cardiac cycle. The lack of dynamic change in saphenous vein grafts and the relatively small dynamic change in luminal diameter and arterial and plaque areas suggest nominal utility in gating these measurements to the cardiac cycle.

Adult↗
PubMed1995

Three-dimensional intravascular ultrasound assessment of plaque volume after successful atherectomy.

The primary purpose of directional coronary atherectomy is the removal of intraluminal plaque. Angiography allows assessment of residual lumen narrowing but is limited in the assessment of residual plaque burden. Intravascular ultrasound has proven useful in assessing plaque size, but current use has been limited to a single, representative cross-sectional image rather than an evaluation of the entire plaque volume. To determine the volume of residual plaque after angiographically successful directional coronary atherectomy ( < or = 20% residual stenosis), we performed intravascular ultrasound in 19 patients before and after atherectomy. Only coronary lesions optimal for three-dimensional analysis (a single, discrete stenosis in a nontortuous, noncalcified native coronary artery) were selected. A 2.9F sheath-design intravascular ultrasound catheter with a motorized pullback device was used in all patients. The cross-sectional area of the artery (defined by the medial-adventitia border), the lumen, and the plaque were measured at 1 mm intervals over a 15 to 20 mm segment, which included the target lesion and a proximal reference segment (n = 362 cross-sections), before and after atherectomy. The volumes of the artery, vessel lumen, or plaque were calculated with a modified Simpson's equation and compared with standard area measurements at the point of maximal stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Effect of beta-adrenergic receptor blockade on the physiologic response to dobutamine stress echocardiography.

Dobutamine is an effective pharmacologic stress agent because of its beta-adrenergic receptor agonist properties. Theoretically, concurrent beta-adrenergic receptor blockade might alter this effectiveness, but clinical experience has been variable. Before assessing the relative effectiveness and implications of dobutamine stress echocardiography (DSE) to detect myocardial ischemia in the presence of beta-blockade the physiologic and hemodynamic effects of dobutamine with simultaneous beta-blockade must be understood in a controlled setting. Therefore the purpose of this study was to determine if beta-blocking agents alter the timing and magnitude of the physiologic response to graded doses of dobutamine during a standard DSE. Paired DSEs were performed in seven instrumented open-chest dogs with and without beta-blockade (esmolol 500 micrograms/kg initial bolus and 100 micrograms/kg/min infusion). Heart rate, systolic pressure, proximal left anterior descending coronary artery flow, myocardial thickening, and percentage left ventricular area change (% AC) were monitored. The data for each parameter were fit to linear or exponential functions. With graded doses of dobutamine, the rate of increase in coronary flow was greater than that in %AC, which in turn was greater than that in heart rate (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1994

In vivo mitral valve morphology and motion in mitral valve prolapse.

Mitral leaflet morphology in mitral valve prolapse (MVP) has been suggested to be prognostically important, but in vivo valvular morphology is incompletely described in patients with MVP or in normal subjects. Accordingly, the length of both mitral leaflets and their zone of apposition, the thickness of their rough and clear zones, diastolic and systolic mitral annular diameters, and indexes of abnormal leaflet motion were measured in the parasternal long-axis echocardiographic view in 100 patients with MVP and 100 age- and sex-matched normal subjects. In both groups posterior leaflet thickness was related to age, as were anterior leaflet thickness and posterior leaflet length in patients with MVP. Compared with normal subjects, MVP patients without mitral regurgitation had thickened leaflets, elongated anterior leaflets, and large annular diameters (p < 0.0001). Patients with severe regurgitation had thicker leaflets, longer posterior leaflet and annular dimensions, and more abnormal leaflet motion than MVP patients without regurgitation. Leaflet thicknesses of different zones were supranormal in 60% to 67% and in 49% to 59% of MVP patients with and without severe regurgitation, respectively. MVP patients with regurgitation also had higher prevalences of abnormal mitral annular diameter than those without regurgitation (67% vs 29%) and > 3 mm posterior leaflet billowing into the left atrium (60% vs 34%). Thus, mitral valve size and leaflet thickness are increased in MVP patients without as well as with clinically important mitral regurgitation. The usefulness of leaflet thickening as a marker of severe MVP is limited by its high prevalence in patients with clinically mild MVP.

Adult↗
PubMed1987

Contrasting patterns of autonomic dysfunction in patients with mitral valve prolapse and panic attacks.

Both mitral valve prolapse (MVP) and panic attacks have been reported to be associated with autonomic dysfunction, but previous studies have been limited by the lack of clear separation between patients with MVP and those with panic attacks and the use of noncomparable control subjects. Accordingly, heart rate and blood pressure responses to deep breathing, five minutes' quiet standing, and the Valsalva maneuver were studied in age- and cardiac symptom-matched groups of 33 control subjects, 66 patients with MVP, 20 patients with panic attacks, and 17 patients with both MVP and panic attacks. Compared with control subjects, patients with MVP exhibited more syncope (13 of 66, or 20 percent, versus none of 33, or 0 percent; p less than 0.01), more orthostatic hypotension during quiet standing (11 of 66, or 17 percent, versus one of 33, or 3 percent; p less than 0.01), loss of the normal decrease with age in vagally-mediated heart rate variability during deep breathing (r = 0.13, p = NS versus r = -0.44, p = 0.01), and lower 24-hour epinephrine excretion (6.1 +/- 0.7 versus 11.0 +/- 2.7 micrograms; p less than 0.01). In contrast, patients with panic attacks had greater increases than control subjects or patients with MVP without panic attacks in heart rate, mean blood pressure, and the product of heart rate and mean blood pressure during each minute of quiet standing and during the early strain phase of the Valsalva maneuver. These findings indicate that autonomic dysfunction occurs both in patients with MVP and in those with panic attacks in comparison with symptomatic control subjects, but that the patterns of abnormality differ. Patients with MVP exhibit decreased effectiveness of responses to orthostatic stress, reduced epinephrine excretion, and abnormal vagal tone, whereas patients with panic attacks have heightened cardiovascular responses to postural and positive intrathoracic pressure stresses.

Adult↗
PubMedDate not supplied

Clinical and echocardiographic follow-up of patients previously treated with dexfenfluramine or phentermine/fenfluramine.

CONTEXT: Use of anorexigen therapy is associated with valvular abnormalities, although there is limited information on long-term changes in valvular regurgitation following discontinuation of these agents. OBJECTIVE: To evaluate changes in valvular regurgitation, valve morphology, and clinical parameters 1 year after an initial echocardiogram in patients previously treated with dexfenfluramine or phentermine/fenfluramine and in untreated controls. DESIGN AND SETTING: A reader-blinded, multicenter, echocardiographic and clinical 1-year follow-up study at 25 outpatient clinical sites. PATIENTS: A total of 1142 obese patients (1466 participated in the initial study) who had follow-up echocardiogram; all but 4 had a follow-up medical history and physical examination. Follow-up time from discontinuation of drug to follow-up echocardiogram for 371 dexfenfluramine patients was 17.5 months (range, 13-26 months) and for 340 phentermine/fenfluramine patients was 18.7 months (range, 13-26 months) after discontinuation of drug therapy. MAIN OUTCOME MEASURE: Change in grade of valvular regurgitation and valve morphology and mobility. RESULTS: Echocardiographic changes in aortic regurgitation were observed in 8 controls (7 [1.7%] had decreases; 1 [0.2%] had an increase); 29 dexfenfluramine patients (23 [6.4%] had decreases; 6 [1.7%] had increases; P<.001 vs controls); and 15 phentermine/fenfluramine patients (4.5% all decreases; P =.03 vs controls). No statistically significant differences were observed when treated patients were compared with controls for changes in medical history, physical findings, mitral regurgitation, aortic or mitral leaflet mobility or thickness, pulmonary artery systolic pressure, ejection fraction, valve surgery, or cardiovascular events. CONCLUSION: Progression of valvular abnormalities is unlikely in patients 1 year after an initial echocardiogram and 13 to 26 months after discontinuation of dexfenfluramine and phentermine/fenfluramine.

Adult↗
PubMedDate not supplied

Diagnosis of pulmonary artery hypertension.

The challenge for the clinician is to detect and diagnose pulmonary artery hypertension early, when treatment can be most beneficial. This can be done only if the clinician looks for pulmonary hypertension and confirms the diagnosis through history taking, physical examination, and electrocardiographic and chest roentgenographic evaluation.

Diagnosis, Differential↗