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Biomedical subjects

L M Boxt

Publications and source records attributed to L M Boxt.

At least 73 records · Page 4Linked to original sources
PubMed1986

Automated morphologic evaluation of pulmonary arteries in primary pulmonary hypertension.

Pulmonary wedge angiograms have been shown to reflect the severity of pulmonary vascular disease in congenital heart disease. Thirteen pulmonary wedge angiograms with a balloon occlusion catheter were performed in 11 adult patients (five normals and six with primary pulmonary hypertension [PPH]) and their features related to the resting pulmonary artery pressure (PAP). Individual cine frames from each study were selected and digitized with a computer-assisted operator-interactive program. By fitting densitometric profiles from the vessel segments, serial arterial cross-sectional diameters were calculated from mathematically derived points. There was a strong correlation between arterial taper (T, change in vessel caliber per unit axial length) and a power function of mean PAP with T = 0.304 X PAP-0.59, R = .91, P less than .001. These results demonstrate a correlation between an angiographically derived morphologic characteristic of the pulmonary vasculature (taper) and a hemodynamic parameter (PAP) in PPH. This offers a method to follow the course of the disease and the effects of drug therapy by assessing anatomic changes in the vessels.

Humans↗
PubMed1986

Side branch occlusion complicating percutaneous transluminal coronary angioplasty.

A frequent concern during angioplasty is the possibility of occluding important side branches that originate in arterial stenoses subjected to balloon dilatation. The effect of dilatation on 93 side branches (greater than or equal to 1 mm in diameter) was evaluated in 86 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) in whom those branches arose directly in dilated segments of the left anterior descending, circumflex, or right coronary arteries. Seventy-six of the 93 side branches had minor (less than 50%) narrowing at their origin. Among these side branches, nine (12%) were compromised by PTCA. Seventeen of the 93 side branches had greater than 50% ostial stenosis. Significantly more of these side branches (seven of seventeen, or 41%) were compromised by PTCA (P less than .01). Even when compromise does occur, it usually takes the form of increased stenosis rather than total occlusion. The presence of side branches originating in stenotic lesions is not a contraindication to PTCA since serious compromise of such branches rarely results from this procedure.

Angioplasty, Balloon↗
PubMed1985

Intravenous digital subtraction angiography in diagnosis of vascular graft occlusion.

Differentiation is often difficult between vascular graft occlusion and progression of underlying disease in patients after vascular surgery. We have studied 57 patients after surgery for traumatic and atherosclerotic arterial occlusion and other vascular anomalies using a commercial digital subtraction angiography (DSA) unit; no complications occurred. Indications for examination included pain, diminished pulse, and failure of catheter angiography. Graft patency was established if proximal and distal anastomoses were visualized; occlusion was diagnosed if no graft was imaged or vascular stump found--noted in 31 grafts. Our diagnosis was proved surgically in 24 patients (two refused operation); three others were confirmed angiographically and one by Doppler ultrasonic examination. In our experience DSA is a safe, specific means of following postoperative grafts and diagnosing their occlusion.

Angiography↗
PubMed1985

Comparison of intravenous digital subtraction angiography to conventional aortography in patients with abdominal aortic aneurysm.

Evaluation of intravenous digital subtraction angiography (IV DSA) in patients with abdominal aortic aneurysm was performed by obtaining catheter aortograms immediately before DSA studies in ten patients. Diagnostic images were obtained in nine of ten digital subtraction examinations. Although repeat injections were necessary in six DSA and three conventional aortography cases for adequate imaging of both cephalad and caudal extension of the aneurysm, average contrast dose was 53 cc (62 cc in standard catheter studies). Renal artery stenosis was diagnosed by DSA in two of three vessels, multiple renal arteries were demonstrated by both modalities in two cases. Digital subtraction and conventional aortographic findings were proved at surgery. Intravenous DSA was shown to be useful in the preoperative evaluation of patients with abdominal aortic aneurysm.

Angiography↗
PubMed1985

Zonal parametric imaging: concept and application to renal angiography.

A new method is described that modifies the original concept of parametric or functional imaging. While the conventional parametric image replaces a temporal sequence of images with a single static image based upon a selected parameter, in the new approach fixed zonal areas and bands are established within the imaged organ, and the mean value for each zone is computed. It is shown that parametric images can be quantified and objectively compared in this way. The algorithm has been implemented to analyze renal studies.

Angiography↗
PubMed1985

Nuclear magnetic resonance spectroscopy of rat ventricles following chronic hypoxia: a model of right ventricular hypertrophy.

Nuclear magnetic resonance spectroscopy was used to study the effect of chronic hypoxia on both right (RV) and left ventricular and septal (LV + S) muscle. Rats in the hypoxic group, kept in a hypobaric chamber at 1/2 atm pressure for 2 weeks, developed right, but not left, ventricular hypertrophy (p less than 0.001). Tissues were studied within 2.5 h of return to air. T1 and T2 relaxation times of RV, LV + S and thigh muscle (Th) from hypoxic and control rats were compared. The T2 value distinguished hypoxic from control RV (p less than 0.002), but not hypoxic from control LV + S or Th, indicating that the change in relaxation time reflects cellular hypertrophy, and not hypoxemia. For hypoxic rats only the T2 value distinguished each muscle type: RV from LV + S (p less than 0.009), RV from Th (p less than 0.001) and LV + S from Th (p less than 0001). The T1 value did not identify either the hypoxic or control group or the type of muscle. Percent water content was similar for all tissues. For hypoxic RV, T2 correlated with the percent water content (r = 0.89; p less than 0.01). The sensitivity of T2 to the cellular changes associated with hypoxic RV hypertrophy could provide a means of detecting right ventricular hypertrophy.

Animals↗
PubMed1985

Comparison of the response of the renal blood supply to acetylcholine and to a calcium channel blocking agent, diltiazem, in the dog.

Several vasodilators, including acetylcholine, are capable of inducing maximal renal vasodilatation when infused into the renal artery. Despite substantial interest in the renal vascular response to calcium channel blocking agents, there has been no systematic comparison of any of these agents to an index vasodilator, such as acetylcholine. We compared the renal vascular angiographic response to acetylcholine and diltiazem, infused into the renal artery in graded dosage, in 14 dogs. In eight of the dogs renal blood flow was measured with an electromagnetic flowmeter. At peak, the acetylcholine-induced increase in renal blood flow (155 +/- 25 to 309 +/- 55 ml/min) slightly exceeded that induced by diltiazem (143 +/- 13 to 257 +/- 58 ml/min). A close correlation was found between the maximal blood flow increase induced by acetylcholine and by diltiazem (R = .95). Dilatation of the intrarenal arterial tree evident on the renal arteriogram was substantially less striking with diltiazem than with acetylcholine in these eight dogs. To ascertain the possible contributing role of the surgery required for blood flow measurement, the two agents were assessed in six additional dogs without blood flow measurement. In these six dogs diltiazem and acetylcholine induced essentially identical degrees of renal arterial vasodilatation. It is concluded that diltiazem, the calcium channel blocking agent, produces near maximal renal vasodilatation at the arteriolar level and that responses of more proximal elements of the renal arterial tree, visible during renal arteriography, are sensitive to the conditions of the experiment.

Acetylcholine↗
PubMed1985

Evaluation of optimized biplane pulmonary cineangiography.

Biplane pulmonary cineangiograms utilizing a short cine pulse width and automatic brightness control were performed in 47 patients during normal respiration. The diagnostic quality of the arteriograms was categorized as good in 33 patients, fair in 12 patients, and poor in two patients. Of the 18 patients in whom pulmonary emboli were identified, cineangiography displayed certain diagnostic features to advantage, including motion of emboli in ten and respiratory scissoring of vessels overcoming vascular superimposition in three. Optimized pulmonary cineangiography is an acceptable alternative to serial film pulmonary angiography for the diagnosis of pulmonary embolism.

Cineangiography↗
PubMed1985

Percutaneous transluminal coronary angioplasty with an over-the-wire system.

The original Gruentzig coaxial catheter system for percutaneous transluminal coronary angioplasty (PTCA) utilized a blunt, closed-end, inner balloon catheter with a short guide wire attached to its tip. Options for safely crossing severe stenoses with this large, nonmaneuverable catheter were limited. More recently, over-the-wire systems have been developed in which the lesion initially is crossed with a small-caliber floppy or steerable guide wire, then by the balloon catheter advanced over the wire. Technical success was achieved in 78 of our first 100 PTCAs with this system. Significant cardiac complications occurred in ten patients, seven of whom required emergency coronary bypass surgery. A recently published survey of all PTCA techniques reported a technical success rate of 62%. Our higher success rate may be attributed to certain advantages of the over-the-wire system, which are discussed in detail. A learning curve is associated with this procedure: our success rate was 65% in the first 20 cases but 81% thereafter. These results can be considered typical of those expected at hospitals now beginning PTCA programs with advanced over-the-wire technology.

Angioplasty, Balloon↗
PubMed1985

Dissection complicating angioplasty.

Extensive arterial dissection producing significant arterial obstruction or occlusion after technically uncomplicated percutaneous transluminal angioplasty in three patients is described. Despite the initially ominous arteriographic appearance, short-term (4-8 months) follow-up demonstrated complete resolution without surgical intervention. A trial of conservative management is recommended for this complication.

Adult↗
PubMed1985

Percutaneous transluminal coronary angioplasty.

Percutaneous transluminal coronary angioplasty (PTCA) has revolutionized the treatment of patients with coronary disease. As many as 25 per cent of those requiring myocardial revascularization can now undergo PTCA instead of bypass surgery. This article reviews PTCA techniques, clinical results, case selection, complications, recent advances in equipment design, restenosis rate, use in acute myocardial infarction, and PTCA of coronary bypass grafts.

Angioplasty, Balloon↗
PubMed1984

Equipment choices, technical aspects and pitfalls of percutaneous transluminal angioplasty.

Previously published papers on percutaneous transluminal angioplasty (PTA) have emphasized results rather than techniques. This review deals with equipment choices, technical aspects and pitfalls observed during the first 200 PTAs at the Brigham and Women's Hospital. Specific topics discussed include: (1) catheters kept in stock in the laboratory, (2) choice of approach and entry into the artery, (3) techniques for crossing stenoses, (4) dilatation of the lesion, (5) drugs used during the procedure, and (6) proper performance and interpretation of the postangioplasty arteriogram.

Angioplasty, Balloon↗
PubMed1984

Digital subtraction angiography: principles and pitfalls of image improvement techniques.

The technology of imaging methods in digital subtraction angiography (DSA) is discussed in detail. Areas covered include function of the video camera in both interlaced and sequential scan modes, digitization by the analog-to-digital converter, logarithmic signal processing, dose rates, and acquisition of images using frame integration and pulsed-sequential techniques. Also discussed are various methods of improving image content and quality by both hardware and software modifications. These include the development of larger image intensifiers, larger matrices, video camera improvements, reregistration, hybrid subtraction, matched filtering, recursive filtering, DSA tomography, and edge enhancement.

Angiography↗