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Biomedical subjects

B Pitt

Publications and source records attributed to B Pitt.

At least 325 records · Page 18Linked to original sources
PubMed1976

Nitroglycerin-induced severe hypotension and bradycardia in patients with acute myocardial infarction.

Seven episodes of simultaneous severe systemic arterial hypotension and absolute or relative bradycardia were observed in five patients receiving either sublingual nitroglycerin (two patients) or intravenous nitroglycerin (three patients) within the first 24 hours of onset of symptoms of acute myocardial infarction. Left ventricular filling pressure, measured as pulmonary artery diastolic pressure, decreased simultaneously in all four patients in whom pulmonary artery pressures were monitored. No initial increase in heart rate was observed in any of the five patients prior to the development of bradycardia. Possible mechanisms producing simultaneous bradycardia and hypotension during nitroglycerin administration are considered. The patient studies emphasize the importance of careful hemodynamic monitoring during administration of sublingual or intravenous nitroglycerin to patients with acute myocardial infarction.

Aged↗
PubMed1976

Thallium 201 myocardial imaging in patients with pulmonary hypertension.

The appearance of the right ventricular myocardium on thallium 201 myocardial perfusion images was evaluated in patients with chronic pulmonary hypertension and compared to patients without pulmonary hypertension. Four groups of patients were studied: 1) eight normals, 2) five patients with angiographically documented coronary artery disease and normal pulmonary artery pressures, 3) ten patients with moderate to severe pulmonary parenchymal or vascular disease and documented pulmonary hypertension and 4) eight patients with chronic left ventricular dysfunction and pulmonary hypertension discovered during cardiac catheterization. The right ventricular free wall was visualized on the thallium 201 myocardial perfusion image in only one of eight normals (group 1) and in only one of the five patients with coronary artery disease (group 2) and measured 0.5 cm and 0.9 cm in thickness, respectively. In patients with documented pulmonary hypertension the right ventricle was visualized on low contrast thallium 201 myocardial perfusion image in all patients. The apparent right ventricular free wall thickness measured from the ungated thallium 201 myocardial perfusion images was 1.7 +/- 0.3 cm in group 3 and 1.5 +/- 0.2 cm in group 4. Right ventricular hypertrophy was detected by electrocardiography in only five of ten patients in group 3 and only one of eight patients in group 4. Thallium 201 myocardial perfusion imaging appears to be a useful technique for assessing the effects of chronic pulmonary hypertension on the right ventricular myocardium.

Chronic Disease↗
PubMed1976

Thallium-201 for myocardial imaging: appearance of the normal heart.

Thallium-201 myocardial perfusion images were obtained from 13 healthy adults after tracer administration both at rest and at maximal stress. On the rest-injected scan, tracer was seen in left ventricular myocardium, liver, and spleen. In two subjects with resting tachycardia, the right ventricular myocardium was slightly visualized after tracer injection at rest. When tracer was administered at stress, the left ventricular activity was more nearly homogeneous and the left ventricle was better defined on the scan. The left-ventricle-to-lung-background activity ratio increased from 2.4 at rest to 3.4 at stress. The right ventricular myocardium was seen on the stress-injected scan. Phantom studies, performed to define the optimum position for visualization of lesions, showed that small lesions were best defined when seen either en face or in tangent. Scans should be performed at stress whenever possible and multiple views are essential.

Adult↗
PubMed1976

Natural history of myocardial infarction and its prodromal syndromes.

Angiographic studies have shown that the severity of obstructive coronary artery disease is a major facor determining mortality in patients with coronary artery disease. The symptomatic presentation of patients with coronary artery disease appears to be less important in determining survival than the extent of coronary artery narrowing. The extent of left ventricular dysfunction is a second major factor that determines survival. The extent of myocardial damage is also important in determining survival in patients with acute myocardial infarction. Infarct extension has been found to be a frequent occurrence in patients with acute anterior transmural infarction. Since infarct extension often occurs several days after hospital admission, an opportunity may exist to apply therapeutic interventions prophylactically to prevent or limit this additional myocardial loss. To limit the extent of myocardial damage that results from infarction may also help to reduce the frequency of ventricular arrhythmias that occur in the second week after infarction, since these arrhythmias are associated with relatively high peak CPK values and a low left ventricular ejection fraction. Studies in patients with acute nontransmural infarction suggest that infarct size may not be the major factor that affects long term survival but other factors, possibly the extent of coronary artery narrowing, may be important. Although in-hospital mortality following acute infarction may have been altered over the past decade by coronary care units, there is little to suggest that prehospital or late mortality following hospital discharge have been altered. If overall mortality associated with infarction is to be reduced, therapeutic interventions to reduce both the extent of myocardial damage and extent or effect of severe coronary artery narrowing will have to be more vigorously applied in the future.

Angina Pectoris↗
PubMed1975

Idiopathic hypertrophic subaortic stenosis: detection by thallium 201 myocardial perfusion imaging.

To determine whether thallium 201 myocardial imaging could be used to detect hypertrophic cardiomyopathy, 10 patients with idiopathic hypertrophic subaortic stenosis were studied. Asymmetric septal hypertrophy, an anatomic marker for this disease, was evident on thallium scans in the patients with idiopathic hypertrophic subaortic stenosis, with a ratio of septum to left ventricular free wall of 1.7 cm compared to 1.0 cm in eight normal volunteers, and 1.0 cm in eight patients with concentric left ventricular hypertrophy. Patients with hypertrophic cardiomyopathy also demonstrated apical ventricular wall thickening, and a thicker posterior ventricular free wall in the obstructive in contrast to the nonobstructive form of this disease. Thallium scans of three patients with pulmonary hypertension and secondary asymmetric septal hypertrophy were distinguished from idiopathic hypertrophic subaortic stenosis by marked right ventricular wall thickening. Thus, thallium 201 myocardial perfusion imaging provides a noninvasive method for detection and evaluation of idiopathic hypertrophic subaortic stenosis.

Cardiomyopathy, Hypertrophic↗
PubMed1975

Reversal by phenylephrine of the beneficial effects of intravenous nitroglycerin in patients with acute myocardial infarction.

Nitroglycerin has been shown to reduce ST-segment elevation during acute myocardial infarction, an effect potentiated in the dog by agents that reverse nitroglycerin-induced hypotension. Our study was designed to determine the effects of combined nitroglycerin and phenylephrine therapy. Ten patients with acute transmural myocardial infarctions received intravenous nitroglycerin, sufficient to reduce mean arterial pressure from 107 +/- 6 to 85 +/- 6 mm Hg (P less than 0.001), for 60 minutes. Left ventricular filling pressure decreased from 19 +/- 2 to 11 +/- 2 mm Hg (P less than 0.001). SigmaST, the sum of ST-segment elevations in 16 precordial leads, decreased (P less than 0.02) with intravenous nitroglycerin. Subsequent addition of phenylephrine infusion, sufficient to re-elevate mean arterial pressure to 106 +/- 4 mm Hg (P less than 0.001) for 30 minutes, increased left ventricular filling pressure to 17 +/- 2 mm Hg (P less than 0.05) and also significantly increased sigmaST (P less than 0.05). Our results suggest that addition of phenylephrine to nitroglycerin is not beneficial in the treatment of patients with acute myocardial infarction.

Acute Disease↗
PubMed1975

The effect of cardiopulmonary bypass perfusion pressure on myocardial gas tensions in the presence of coronary stenosis.

Mass spectrometry was utilized to determine myocardial gas tensions in dogs subjected to cardiopulmonary bypass. Myocardial ischemia occurred in animals with normal coronary arteries when cardiopulmonary bypass perfusion pressure fell 40 to 60 mm Hg below the mean aortic pressure measured prior to bypass. Myocardial ischemia did not occur, or could be eliminated when present, if cardiopulmonary bypass perfusion pressure was maintained near prebypass mean aortic pressure. In animals with constricted circumflex coronary arteries, the adverse effect of low perfusion pressure on myocardial metabolism during cardiopulmonary bypass was found to be more severe in areas of myocardium supplied by the stenotic coronary artery. It is concluded that maintenance of cardiopulmonary bypass perfusion pressure near the level of preoperative mean aortic pressure will help prevent myocardial ischemia during operation; particularly in patients with coronary artery disease.

Animals↗
PubMed1975

Role of sublingual nitroglycerin in patients with acute myocardial infarction.

Fourteen patients with acute myocardial infarction were given 0.3 mg sublingual nitroglycerin within the first 12 hours of their acute myocardial infarction. Five minutes after sublingual nitroglycerin mean arterial pressure fell 9 mmHg (1.2 kPa) and remained significantly reduced for 30 minutes. Pulmonary capillary wedge pressure fell from a mean control value of 17 to 12 mmHg (2.3 to 1.6 kPa) and also remained reduced for 30 minutes. Heart rate was significantly raised and stroke work index reduced at five minutes. Patients with a stroke work index of greater than 55 g m per m-2 b.s.a. responed to nitroglycerin with a fall in both pulmonary capillary wedge pressue and strokework index while in those with a stroke work index of less than 55 g m per m-2 b.s.a. stroke work index did not fall concomitantly with the fall in pulmonary capillary wedge pressure. In one patient, nitroglycerin led to a precipitious fall in arterial pressure andrecurrence of chest pain.

Acute Disease↗
PubMed1975

The combined use of Gated Cardiac Blood Pool Scanning and Myocardial Imaging with Postassium-43 in the Evaluation of Patients with Myocardial infarction.

Fourteen patients with transmural myocardial infarction were studied by gated cardiac blood pool scanning (to determine regional ventricular function) and 43-K myocardial imaging (to determine the regional distribution of myocardial perfusion). An akinetic area on the gated scan and an area of decreased tracer concentration on the 43-K image were detected. The area of reduced 43-K concentration averaged 33.5% of the left ventricular circumference which correlated (r = 0.74, p less than 0.01) with the area of infarction determined by the zone of akinesis, 34.2% of left ventricular circumference. The extent of akinesis and left ventricular ejection fraction were significantly different in those patients with left ventricular failure than in those without failure.

Adult↗
PubMed1975

Intravenous nitroglycerin in acute myocardial infarction.

Vasodilator therapy has been shown to improve ventricular function in patients with left ventricular failure complicating acute myocardial infarction. Sublingual nitroglycerin also improves ventricular function in these patients but its effects are transient and variable. Infusion of intravenous nitroglycerin in 12 patients with acute infarction resulted in a decrease in left ventricular filling pressure from a mean of 22 plus or minus 2 mm Hg to 12 plus or minus 1 mm Hg (P less than 0.001) associated with a 7 mm Hg decrease in mean arterial pressure (P less than 0.05). Since stroke work index did not change significantly, this represents and improvement in ventricular performance and/or an alteration in ventricular compliance. All six patients in whom serial precordial mapping studies were performed showed a decrease in sigma ST (P less than 0.001). These findings suggest that intravenous nitroglycerin improved left ventricular function and decreased the extent of myocardial ischemia. Longer infusion may act to preserve borderline ischemic myocardium and thus limit infarct size.

Administration, Oral↗
PubMed1975

Thallium-201 for myocardial imaging. Relation of thallium-201 to regional myocardial perfusion.

Following intravenous administration, the myocardial concentration of tracer thallium-201, potassium-43, and rubidium-81 were determined in mice; thallium was present in the greatest concentration in the myocardium (2.08% compared 1.25% for potassium and 1.15% for rubidium at 10 minutes). The regional myocardial distribution of thallium-201 was determined in dogs under conditions of normal flow, and total occlusion, and compared with potassium-43 (r=0.97). The regional distribution of thallium-201 was compared to microspheres under conditions of partial occlusion and reactive hyperemia (r=0.97). Thallium-201 was evaluated in a series of phantom scans, which demonstrated that the low energy X-ray of thallium was suitable for imaging. These results suggest that thallium-201 can be used for the evaluation of the distribution of regional myocardial perfusion.

Animals↗
PubMed1975

Hemodynamic and prognostic findings in patients with transmural and nontransmural infarction.

One hundred and eleven patients with transmural (TMI) and 49 with nontransmural myocardial infarction (NTMI) underwent hemodynamic investigation within 24 hours of onset of symptoms. Patients with NTMI were subdivided into those with ST-segment or T-wave changes alone with a normal QRS complex (NTMI-A) and a group with QRS abnormalities that did not satisfy the criteria for TMI (NTMI-B). Those with TMI had a significantly higher peak creatine phosphokinase (CPK) than those with NTMI: 840 plus or minus 99 and 336 plus or minus 69, respectively, P smaller than 0.05. There was not difference in peak CPK between those with NTMI-A and B. The incidence of arrhythmias and cardiac failure, and routine hemodynamic findings except for left ventricular filling pressure were similar in those with TMI and NTMI. There was not significant difference in in-hospital mortality between those with TMI (22%) and NTMI (33%). There was however a significant difference in in-hospital mortality between those with NTMI-A (0%) and NTMI-B (27%, P smaller than 0.05). The late mortality in those surviving their initial hospitalization was also not different between those with TMI (18%) and NTMI (19%) during a mean follow-up period of 20.2 months. In contrast to the in-hospital mortality those with NTMI-A had a late mortality similar to those with NTMI-B and those with TMI.

Arrhythmias, Cardiac↗
PubMed1975

Right ventricular dysfunction detected by gated scintiphotography in patients with acute inferior myocardial infarction.

Twenty-seven patients with acute myocardial infarction not complicated by cardiogenic shock and ten normal volunteers were studied with gated cardiac blood pool scans. The ratio right vetricular area/left ventricular area (RVA/LVA) determined from the left anterior oblique end-diastolic scans was examined. The ratio was 1.11 +/- .06 in the normal volunteers. In patients with anterior infarction the ratio fell to 0.75 +/- .12 (P less than .05) due to left ventricular enlargement. In those with inferior infarction the ratio was 1.12 +/- .23 which was greater than in those with anterior infarction (P less than .05) due to enlargement of both the left and right ventricles. Six patients with cardiogenic shock, three with inferior and three with anterior infarction were studied. The three with anterior infarction had left ventricular enlargement and a decrease in the ratio of RVA/LVA to 0.62 while the three with inferior infarction had an increase in the ratio to 2.05 suggesting right ventricular dilatation and dysfunction. These studies suggest a high incidence of right ventricular dysfunction in patients with inferior myocardial infarction.

Aged↗
PubMed1975

Ventricular arrhythmias in the late hospital phase of acute myocardial infarction. Relation to left ventricular function detected by gated cardiac blood pool scanning.

Abnormalities of left ventricular function and extent of myocardial infarction were studied in relation to prevalence of late ventricular premature contractions (VPCs) in 36 patients in the convalescent stage of acute myocardial infarction (MI). Left ventricular ejection fraction (EF) and percent akinesis (%A) were calculated from gated cardiac blood pool scans; myocardial infarct size was estimated from peak CPK values; and VPCs were detected by 24 hour ambulatory ECGs 2-4 weeks following hospitalization for acute MI. Twenty-two patients had either zero (class 0) or less than 30/hour unifocal VPCs (class I). Fourteen patients had greater than 30/hour unifocal (class II), multifocal (class III) or coupled VPCs (class IV), including ventricular tachycardia. Thirteen of 14 class II-IV patients had EF less than 40% compared with only 8 of 22 class 0-I patients. Class II-IV patients had significantly lower mean EF (30.5 +/- 2.3 SE to 49.6 +/- 4.0) P less than 0.01, higher mean %A (28.1 +/- 2.2 to 16.9 +/- 3.7) P less than 0.05, and higher mean peak CPK (1350 +/- 187 to 721 +/- 155) P less than 0.05 than class 0-I patients. These data suggest that VPCs may not be an independent risk factor for sudden cardiac death in the convalescent phase of MI.

Acute Disease↗
PubMed1975

Changes in intramyocardial ST segment voltage and gas tensions with regional myocardial ischemia in the dog.

This study was designed to evaluate the sensitivity of changes in myocardial carbon dioxide and oxygen tensions as indicators of regional myocardial ischemia and also to determine to what extent these changes can be related to changes in intramyocardial ST segment voltage. Changes in ST segment voltage recorded in unipolar epicardial electrodes proved to be a less-sensitive indicator of underlying myocardial ischemia than were changes in ST segment voltage recorded in unipolar intramyocardial electrodes. In 9 dogs, regional ischemia was produced by placing a variable constrictor on the left circumflex coronary artery; circumflex flow was monitored. Myocardial carbon dioxide and oxygen tensions were measured using a mass spectrometer. Unipolar electrograms were recorded using a multicontact plunge electrode. With progressive degrees of proximal stenosis, ranging from a critical stenosis, which is associated with a decrease in mean flow of less than 15%, to a severe stenosis associated with and 80% decrease, ST voltage increased 21 mv and carbon dioxide tension increased 84 mm Hg, but oxygen tension decreased only 7 mm Hg. The study suggests that increases in intramyocardial ST segment voltage, an index of myocardial ischemia, are associated with parallel increases in myocardial carbon dioxide tension, each providing a more sensitive quantitative correlate of regional myocardial ischemia than do decreases in oxygen tension. The local accumulation of carbon dioxide may be an important pathophysiological mechanism in myocardial ischemia.

Animals↗