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Biomedical subjects

B Pitt

Publications and source records attributed to B Pitt.

At least 217 records · Page 12Linked to original sources
PubMed1984

The beneficial effects of nafazatrom (BAYg6575) on experimental coronary thrombosis.

An in vivo model of coronary artery thrombosis in the conscious dog was used to evaluate the potential antithrombotic effect of nafazatrom (BAYg6575). A silver wire electrode was implanted in the left circumflex coronary artery (LCX) and was used at a later time to deliver a 50 uA anodal current for 24 hours to the intimal surface of the vessel. The resulting injury to the endothelium was accompanied by the adhesion, aggregation, and subsequent formation of an occlusive thrombus in the LCX of vehicle-treated dogs. Nafazatrom was given as an intravenous dose of 1 mg/kg for 48 hours, before anodal stimulation of the coronary artery was initiated, and was repeated every 6 hours during anodal stimulation for a total treatment period of 72 hours. As compared to vehicle-treated control dogs, the dogs treated with nafazatrom had smaller thrombi, preservation of coronary blood flow, a lesser degree of ischemic injury in the myocardial region subserved by the LCX, and less frequent premature ventricular complexes during the final 12 hours of the study period. Concomitant ex vivo platelet aggregation studies revealed significant inhibition of platelet aggregation in response to collagen and adenosine diphosphate in drug-treated dogs. The results of these investigations provide evidence that nafazatrom prevents in vivo development of occlusive coronary artery thrombi in response to disruption of the endothelial surface of the vessel.

Adenosine Diphosphate↗
PubMed1984

The chronic coronary flow reserve provided by saphenous vein bypass grafts as determined by digital coronary radiography.

Intraoperative measurements following aortocoronary revascularization have demonstrated a reduced coronary flow reserve (CFR) in saphenous vein bypass grafts. To determine whether chronic bypass graft flow reserve returns to normal, we studied patients in the cardiac catheterization laboratory by means of a newly developed digital coronary radiographic technique. CFR ratios were determined for 54 arterial distributions from 33 men. Twenty-two distributions were normal (group I) 22 had saphenous vein bypass grafts (group II), seven had high-grade stenoses, which were subsequently bypassed (group III), and three were bypassed but had flow-limiting stenoses (group IV). Group II arteries had approximately half the CFR of group I arteries (1.40 +/- 0.17 vs 1.78 +/- 0.31; p less than 0.0001) but significantly improved CFR compared to group III arteries (1.40 +/- 0.17 vs 1.05 +/- 0.13; p less than 0.002) or group IV arteries (1.40 +/- 0.17 vs 1.05 +/- 0.12; p less than 0.02). These results indicate that regional CFR is improved by nonstenotic saphenous vein bypass grafts but does not return to normal.

Adult↗
PubMed1984

Effects of reperfusion on complete heart block complicating anterior myocardial infarction.

Two patients with complete heart block complicating extensive anterior myocardial infarction underwent late (greater than 40 hours) coronary reperfusion with angioplasty. One to one atrioventricular conduction was restored within minutes of reperfusion despite a lack of measurable ventricular muscle salvage as demonstrated by ventriculography 1 week later. The evidence favors reversible ischemia rather than extensive necrosis of the proximal conduction system as the mechanism of heart block in this subgroup of patients.

Adult↗
PubMed1984

Criteria for successful coronary angioplasty as assessed by alterations in coronary vasodilatory reserve.

Currently, the success of coronary angioplasty is defined by anatomic criteria. Because of the known limitations of coronary arteriography, the translesional pressure gradient and coronary vasodilatory reserve were studied in 15 patients undergoing coronary angioplasty with the intent of defining a physiologically successful result. Coronary vasodilatory reserve was measured by a digital radiographic technique that has been previously validated against directly measured coronary sinus flow (r = 0.90, p less than 0.0001). A significant reduction in luminal stenosis from 71 +/- 12 to 34 +/- 11% (p less than 0.001) was accompanied by a reduction in translesional gradient from 47 +/- 19 to 21 +/- 12 mm Hg (p less than 0.001) and an increase in coronary vasodilatory reserve from 1.03 +/- 0.15 to 1.29 +/- 0.13 (p less than 0.001). There was a significant correlation between changes in luminal stenosis and changes in translesional gradient (r = 0.61, p less than 0.05), although a change of 20% or less in luminal diameter was accompanied by no change in pressure gradient. A more significant relation between changes in gradient and in coronary hyperemic reserve existed (r = 0.77, p less than 0.005). The relation was accurate even for small changes in gradient. Because saphenous vein bypass grafts have been shown to increase coronary vasodilatory reserve to at least 1.20, it is proposed that this physiologic criterion be used to define the success of revascularization by angioplasty. In patients in whom this value was achieved, translesional gradient was invariably 25% or less of ostial pressure and 20 mm Hg or less.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1984

Regional myocardial contractile response to the beta-adrenergic stimulant prenalterol in the conscious dog following myocardial infarction. Mechanism of hemodynamic effect.

In order to assess regional myocardial contractile responses to the beta-adrenergic stimulant prenalterol after recent myocardial infarction, 9 male mongrel dogs underwent left circumflex coronary artery (LCX) occlusion after implantation of miniature subendocardial sonomicrometer crystals in normal, marginally ischemic (border) and central ischemic zones. 90-min LCX occlusion with reperfusion resulted in substantial infarction (mean +/- SEM 24 +/- 3% of total left ventricular area) and characteristic regional functional alterations. In conscious, unsedated animals 72 h after infarction, intravenous prenalterol (30 micrograms/kg) significantly decreased end-diastolic and end-systolic segment length and increased percent systolic shortening in normal and border zones, but did not alter ischemic zone function. Heart rate increased significantly with prenalterol. Regional myocardial function before drug administration correlated closely with response to the inotropic agent. These results indicate that the mechanism by which prenalterol improves cardiac function 72 h after myocardial infarction is stimulation of normal and marginally ischemic myocardium.

Animals↗
PubMed1984

Unsedated animal models of pulmonary mucociliary transport.

Measurements of the rate of mucociliary transport in the airways of the lower respiratory tract have been shown to be influenced by the techniques and protocols used. To avoid the effects associated with invasive techniques and anesthesia in animal models used to study the effect of maturation, drugs, disease, and inhaled pollutants on mucociliary transport we have developed unsedated dog and baboon models of mucociliary transport using radioaerosol techniques. As far as they have been tested these animal models of mucociliary transport react to drugs such as isoproterenol and atropine in the same manner as in man.

Aerosols↗
PubMed1983

Noninvasive quantification of jeopardized myocardial mass in dogs using 2-dimensional echocardiography and thallium-201 tomography.

The evaluation of jeopardized myocardial mass is important in defining the effect of interventions during myocardial infarction. To quantitate the in vivo mass at risk, 2-dimensional echocardiography (2-D echo) and thallium-201 single-photon emission computed tomography (SPECT) was performed in 10 closed-chest dogs after circumflex coronary artery occlusion. The 2-D images were manually digitized to compute left ventricular (LV) mass using a modified Simpson's rule algorithm. This measure of LV mass correlated well with the actual LV mass (r = 0.97). Perfused myocardial mass was estimated from thallium SPECT images 4 hours after occlusion using a region-growing algorithm. After the dogs were killed, the jeopardized mass was outlined using a dual perfusion staining technique using triphenyltetrazolium chloride and Evans blue dye. The actual perfused mass was well estimated by the thallium images (r = 0.96). The noninvasively determined mass at risk was calculated as: 2-D mass--thallium SPECT mass, and correlated well with the pathologically determined mass at risk (r = 0.91). Thus, the jeopardized mass may be determined noninvasively by using 2-D echo and thallium-201 tomography. This approach may provide further information regarding the effect of intervention therapy on jeopardized myocardium.

Animals↗
PubMed1983

Intracoronary fibrinolytic therapy in acute myocardial infarction. Report of a prospective randomized trial.

We performed a randomized trial comparing intracoronary administration of streptokinase versus dextrose placebo within six hours after the onset of symptoms of acute myocardial infarction in 40 patients. The base-line clinical, hemodynamic, and angiographic findings were similar in the control and streptokinase-treated groups. Reestablishment of flow occurred in 12 of 20 patients treated with streptokinase and in 2 of 20 given placebo (P less than 0.05). Left ventricular function, angiographic ejection fraction, and regional wall motion, measured before and immediately after intervention, and serial radionuclide ejection fractions, measured at treatment, at 12 days, and at 5 months, were compared according to type of treatment (streptokinase vs. placebo) and outcome of therapy (reperfusion vs. no reperfusion). No statistically significant differences between groups were found. Thus, although streptokinase was more effective than placebo in achieving reperfusion, we detected no improvement of left ventricular function as a result of reestablished coronary flow.

Adult↗
PubMed1983

Automatic computer processing of digital 2-dimensional echocardiograms.

Quantitative studies of left ventricular function using 2-dimensional echocardiography have been limited because of a lack of computerized methods to automatically analyze the echocardiographic images. Previous computer efforts have been directed at digitizing the video output of the 2-D echocardiogram, but this digitizing method has significant limitations. A direct digitization method that produces improvement in signal-to-noise ratio and, subsequently, improved automatic detection of endocardial and epicardial borders, was developed. With definition of these edges, left ventricular global and regional analysis is possible frame by frame so that dynamic changes in cardiac function may be assessed throughout the cardiac cycle. Further technologic advances in 2-D echocardiographic acquisition and image processing should allow computer processing of 2-D echocardiographic data in real time.

Computers↗
PubMed1983

Left ventricular function in patients with ventricular arrhythmias and aortic valve disease.

Forty patients having aortic valve replacement were evaluated preoperatively for ventricular arrhythmia and left ventricular ejection fraction. Arrhythmias were classified as complex or simple using the Lown criteria on the 24-hour ambulatory electrocardiogram; ejection fractions were determined by radionuclide gated blood pool analysis and contrast angiography. The ejection fractions determined by radionuclide angiography were 59.1 +/- 13.1% for 26 patients with simple or no ventricular arrhythmias, and 43.9 +/- 20.3% for 14 patients with complex ventricular arrhythmias (p less than 0.01). Ejection fractions determined by angiography, available for 31 patients, were also lower in patients with complex ventricular arrhythmias (61.1 +/- 16.3% versus 51.4 +/- 13.4%; p less than 0.05). Seven of 9 patients showing conduction abnormalities on the electrocardiogram had complex ventricular arrhythmias. Eight of 20 patients with aortic stenosis had complex ventricular arrhythmias, while 2 of 13 patients with aortic insufficiency had such arrhythmias. It is concluded that decreased left ventricular ejection fraction, intraventricular conduction abnormalities, and aortic stenosis are associated with an increased frequency of complex ventricular arrhythmias in patients with aortic valve disease.

Aortic Valve↗
PubMed1983

Impact of radionuclide techniques on evaluation of patients with ischemic heart disease.

Radiotracer studies of the heart have become clinically important in the last decade, especially for evaluation of patients with known or suspected ischemic heart disease. Radionuclide ventriculography provides quantitative measures of biventricular function and regional wall motion. Recent technical advances include the development of computer programs for analyzing diastolic function, parametric imaging methods such as "phase" analysis and methods for calculating absolute ventricular volumes. Thallium-201 scans provide maps of regional myocardial perfusion. Recent advances include development of computer programs to quantitate regional thallium-201 uptake and to calculate thallium-201 turnover rates and the development of tomographic imaging systems. Technetium-99m pyrophosphate localizes in irreversibly damaged myocardium and provides a method for diagnosing, localizing and sizing acute myocardial infarcts. Recent applications include tomographic imaging to improve image contrast and development of criteria to identify high risk patients after infarction. Two important trends affecting the application of all the radionuclide studies in clinical cardiologic practice are the increasing use of decision analysis for incorporating results of multiple tests into single diagnostic probability statements, and the use of diagnostic algorithms that include the radionuclide studies to optimize the cost effectiveness of evaluation of patients with ischemic heart disease.

Coronary Angiography↗
PubMed1983

Topography of preemptying ventricular segments in patients with Wolff-Parkinson-White syndrome using scintigraphic phase mapping and esophageal pacing.

We analyzed the sequence of ventricular emptying using the phase image in 10 patients with accessory pathways and in 15 normal subjects. In normal subjects, the earliest emptying occurred in ventricular septal, apical and left basal segments. Eight patients had manifest preexcitation; the earliest emptying occurred ectopically in the right ventricle in one of these patients and in the left ventricle in five. The remaining two patients had normal phase maps. Two patients had concealed left-sided pathways. Their phase maps showed earliest emptying in left basal segments. Six of the 10 patients underwent electrophysiologic mapping. There was complete agreement between phase and electrophysiologic maps. Transesophageal atrial pacing increased preexcitation in one patient, normalized the ECG in another and precipitated narrow QRS tachycardia in four patients. Phase maps then showed enlargement, reduction and loss of the ectopic earliest emptying segments, respectively. We conclude that this technique in conjunction with pacing is successful in lateralizing accessory pathways.

Adolescent↗
PubMed1983

Prostaglandins and prostaglandin inhibitors in ischemic heart disease.

The evidence for a role of the prostaglandin system in myocardial ischemia and its consequences is still fragmentary. We review the factors that alter the relation between thromboxane A2 and prostacyclin production such that vasoconstriction, platelet aggregation, and the tendency toward thrombus formation are increased. Strategies to prevent platelet aggregation by interfering with the production of thromboxane A2 or by stimulation or administration of prostacyclin are currently under investigation in a number of centers. The ubiquity of the prostaglandin system and our incomplete understanding make careful long-term clinical trials and observations essential if we are to be sure that the net effect of these attempts is beneficial.

Animals↗
PubMed1983

A randomized clinical trial of intravenous nitroglycerin in patients with acute myocardial infarction: benefits of early treatment.

A prospective randomized clinical trial of intravenous nitroglycerin administered for 48 hours following acute infarction was undertaken to determine whether clinical improvement and/or preservation of ischemic myocardium could be demonstrated. One hundred four patients were randomized to receive either nitroglycerin or placebo infusion. Nitroglycerin infusion was titrated to lower mean arterial pressure 10% using non-invasive monitoring. Early nitroglycerin treatment, defined as treatment initiated less than 10 hours after symptom onset, resulted in a lower incidence of new congestive heart failure, myocardial infarct extension, and/or early death from pump failure (15%) compared to late nitroglycerin treatment (50%, p = 0.008) or early placebo treatment (48%, p = 0.01). Improvement in ejection fraction of greater than or equal to 10% was demonstrated in 7 of 20 (35%) early nitroglycerin treated patients compared to 6, 11 and 0% of patients in the three other subgroups, respectively (p = 0.004). Similarly, thallium-201 perfusion scintigrams showed a greater than 75% improvement in defect score in 23 (48%) patients receiving nitroglycerin within 10 hours compared to 14%, 33% and 0% respectively, in the remaining subgroups (p = 0.035). However, before routine administration of nitroglycerin can be recommended for all patients with acute infarction, larger clinical trials will be required.

Clinical Trials as Topic↗