Serial right ventricular thallium-201 imaging after exercise: Relation to anatomy of the right coronary artery

The relation of the appearance of the right ventricle on serium thallium-201 myocardial imaging to coronary artery anatomy was examined in 88 consecutive patients undergoing exercise thallium-201 testing and coronary angiography for the evaluation of chest pain. Transient defects in the right ventricle were found in 8 patients. All had high grade (≥ 90 %) stenosis of the proximal right coronary artery. Nonvisualization of right ventricular (RV) activity occurred in 10 patients. Nine of the 10 (90%) had significant (>- 50% stenosis) disease of the proximal right coronary artery and 7 (70%) had high grade stenosis. The right ventricle appeared normal in 70 patients. Twenty-nine (41 %) of these patients had significant proximal right coronary artery disease. Right ventricular appearance was not affected by the presence or absence of disease of the left anterior descending or left circumflex artery or by the appearance of the left ventricle.

Thus, with serial RV thallium-201 myocardial imaging after exercise, we found that (1) RV transient defects suggest the presence of high grade proximal right coronary artery stenosis, (2) nonvisualization of RV activity also predicts significant proximal right coronary disease, and (3) the right ventricle frequently appears normal despite proximal right coronary artery disease and therefore this finding does not exclude such disease.     

Early changes in left ventricular size and function after correction of left ventricular volume overload

The ability to predict early postoperative left ventricular size and function in patients with isolated aortic or mitral regurgitation was determined utilizing multigated blood pool imaging before and 2 to 4 weeks after valve replacement (aortic valve, 20 patients; mitral valve, 20 patients). Early postoperatively, ejection fraction decreased significantly (p <0.001) in both patient groups (from 0.55 ± 12 to 0.40 ± 0.14 [mean ± 1 standard deviation] in patients with aortic regurgitation and from 0.66 ± 0.09 to 0.48 ± 0.11 in patients with mitral regurgitation). The decrease in ejection fraction was associated with a large decrease in stroke volume with minimal or no change in end-systolic volume; it was unrelated to the preoperative ejection fraction. Early postoperative ejection fraction correlated best with preoperative end-systolic volume and was normal in 14 (67 percent) of 21 patients with a preoperative ejection fraction above 0.60; 4 (27 percent) of 15 patients with a preoperative ejection fraction of 0.50 to 0.60; and in 0 of 4 patients with a preoperative ejection fraction below 0.50 (p <0.05). In addition, a repeated scan in 16 patients late (1 to 2 years) after operation showed a further reduction in endsystolic volume in patients with aortic regurgitation with an increase in ejection fraction toward preoperative values. There was no significant change in patients with mitral regurgitation.End-diastolic volume decreased significantly (p <0.001) early postoperatively (from 162 ± 60 to 102 ± 41 ml/m² in patients with aortic regurgitation and from 131 ± 40 to 78 ± 30 ml/m² in patients with mitral regurgitation). This decrease was closely related to a decrease in stroke volume and was unrelated to preoperative ejection fraction. Early postoperative end-diastolic volume correlated best with the preoperative end-systolic volume. The major part of the reduction in end-diastolic volume occurred within 2 weeks of valve replacement.Removal of chronic left ventricular volume overload due to aortic or mitral regurgitation produces a decrease in ejection fraction and end-diastolic volume. The early reduction is in part a result of altered loading conditions and may not necessarily imply alterations in myocardial contractile function. The reduction in ejection fraction appears to persist in patients with mitral regurgitation.     

Increased lung uptake of thallium-201 during exercise myocardial imaging: Clinical,hemodynamic and angiographic implications in patients with coronary artery disease

To determine the clinical significance of increased thallium-201 activity in the lung immediately after exercise stress, the thallium-201 scans in 227 patients undergoing cardiac catheterization were reviewed. Thallium lung activity on the Initial anterior view images were graded qualitatively as follows: 0 (none) in 175 patients (77 percent); 1+ (moderate—increased activity in the lungs but less intense than that in left ventricular myocardium) in 37 patients (16 percent); and 2+ (severe—activity equal to or greater in intensity than left ventricular myocardlal activity) in 15 patients (7 percent). Increased (1+ or 2+) lung activity was related to (1) a greater number of myocardial segmental thallium defects (probability [p] < 0.05); and (2) increased severity and extent of coronary artery disease (p < 0.05). In addition, 2+ lung thallium activity was associated with: (1) a greater prevalence of prior myocardial infarctions (p < 0.01); and (2) a lower angiographic ejection fraction at rest (p < 0.05). To determine the hemodynamic changes associated with increased lung uptake of thallium-201, supine stress thallium imaging was performed during cardiac catheterization in 12 additional patients. Of these, the five patients with increased lung activity on thallium scanning had a mean pulmonary capillary wedge pressure that increased with exercise from 12 ± 1 (mean ± 1 standard deviation) to 24 ± 3 mm Hg (p < 0.05); cardiac index did not increase with stress. In contrast, seven patients without increased lung thallium activity demonstrated an increase in mean cardiac index (p < 0.05) without an associated rise in pulmonary capillary wedge pressure (at rest = 10 ± 3 mm Hg; during stress = 12 ± 2 mm Hg). In conclusion, increased pulmonary uptake during exercise thallium-201 imaging suggests the development of exercise-induced left ventricular dysfunction. Evaluation of lung activity should be added to the routine interpretation of exercise thallium-201 myocardial imaging studies.     

Quantification of pulmonary thallium-201 activity after upright exercise in normal persons: importance of peak heart rate and propranolol usage in defining normal values

Fifty-nine normal patients (34 angiographically normal and 25 clinically normal by Bayesian analysis) underwent thallium-201 imaging after maximal upright exercise. Lung activity was quantitated relative to myocardial activity and a lung/myocardial activity ratio was determined for each patient. Stepwise regression analysis was then used to examine the influence of patient clinical characteristics and exercise variables on the lung/myocardium ratio. Peak heart rate during exercise and propranolol usage both showed significant negative regression coefficients (p less than 0.001). No other patient data showed a significant relation. Using the regression equation and the estimated variance, a 95% confidence level upper limit of normal could be determined for a give peak heart rate and propranolol status. Sixty-one other patients were studied to validate the predicted upper limits of normal based on this model. None of the 27 patients without coronary artery disease had an elevated lung/myocardial ratio, compared with 1 of 8 with 1-vessel disease (difference not significant), 6 of 14 with 2-vessel disease (p less than 0.005), and 6 of 12 with 3-vessel disease (p less than 0.0001). Thus, lung activity on upright exercise thallium-201 studies can be quantitated relative to myocardial activity, and is inversely related to peak heart rate and propranolol use. Use of a regression analysis allows determination of a 95% confidence upper limit of normal to be anticipated in an individual patient.     

Relationship between airway hyperreactivity and hyperpermeability in Ascaris-sensitive monkeys.

In four Ascaris-sensitive rhesus monkeys, we measured the fractional absorption of 3H-histamine (3HH) and airway response, as pulmonary resistance (R1), to standard histamine aerosols containing tracer amounts of 3HH for control runs (Run 1) and runs after Ascaris antigen challenge (Run 2). The mean rate of accumulation of radioactivity in the plasma volume as a function of delivered dose during histamine exposure (2 min) was fivefold greater for Run 2 (0.047% delivered dose/min) as compared with Run 1 (0.009% delivered dose/min). Whereas histamine inhalation led to insignificant (less than 25%) increases in R1 over control in Run 1. R1 increased by 247% over control after histamine inhalation in Run 2. Thus, both airway hyperpermeability and hyperreactivity to inhaled histamine were observed following specific antigen challenge in this animal model. These data are consistent with the hypothesis that airway mucosal hyperpermeability induced by an allergic reaction is one of the factors contributing to airway hyperreactivity by increasing flows of inhaled bronchoactive agents to effector sites in the airway wall.     

Initial and delayed right ventricular thallium-201 rest-imaging following dipyridamole-induced coronary vasodilation: Relationship to right coronary artery pathoanatomy

The relationship of coronary anatomy to right ventricular (RV) appearance on serial thallium-201 myocardial imaging (TI) following dipyridamole (DP)-induced coronary vasodilation was examined in 71 consecutive patients undergoing coronary angiography for the evaluation of chest pain. Transient defects of the RV were found in 18 patients. All 18 had significant (≥ 50%) stenosis of the proximal right coronary artery (RCA). Nonvisualization of RV activity occurred in 13 patients. Six of these 13 (46%) had proximal RCA disease (p < 0.05 compared to transient defects). Normal RV appearance was seen in 40 patients, of whom only six (15%) had proximal RCA disease (p < 0.001 compared to transient defects). RV appearance was not affected by left anterior descending or left circumflex artery disease or by the thallium-201 uptake in the left ventricle. Thus with serial (initial and delayed) TI following DP (1) a transient RV defect appears to indicate significant proximal RCA disease; (2) normal RV appearance suggests the absence of proximal RCA disease; and (3) however, nonvisualization of the RV appears to be nondiagnostic.     

Airway mucosal permeability in the Ascaris suum-sensitive rhesus monkey.

The permeability of the airways to technetium 99m-labeled albumin was measured in Ascaris suum-sensitive rhesus monkeys. All 8 animals were skin-sensitive to Ascaris suum (AA) antigen, 4 being respiratory responders (R) and 4 nonresponders (NR) to aerosolized antigen. In the absence of antigen challenge there were no differences in the accumulation in the blood of radioactive material from the tracheobranchial tree between the R and NR animals. After a five-minute challenge with aerosolized AA, there was a threefold increase in the rate of accumulation of radioactive material in the blood over control for the R group with no effect noted in the NR group. Gel filtration data indicated that the radioactivity in the blood most likely represented low molecular weight albumin fragments, resulting from spontaneous degradation of Tc-albumin, that crossed the mucosa and partially bound to circulating albumin. It is concluded that hyperpermeability of the airway mucosa probably is not a factor that contributes to the selective responsiveness of the R group to aerosolized antigen, and that airway permeability is increased consequent to the allergic reaction mediating acute bronchoconstriction.     

Mitral valve replacement for isolated mitral regurgitation: Analysis of clinical course and late postoperative left ventricular ejection fraction

One hundred five patients underwent mitral valve replacement for relief of isolated mitral regurgitation between 1974 and 1979. There were 4 in-hospital deaths (4 percent) and 12 late deaths giving an 82 percent predicted 5 year survival rate. An age of 60 years or more at the time of surgery and a preoperative left ventricular ejection fraction of less than 0.40 were the only variables that correlated with decreased survival at 3 to 5 years after operation (p <0.05). Postoperatively, 87 (98 percent) of 89 long-term survivors were in New York Heart Association functional class I or II (68 in class I and 19 in class II). Survival did not differ between patients with porcine versus mechanical valve replacement, but patients with a mechanical valve had a greater incidence of postoperative cerebrovascular accident ($\text{8.6}\text{100}$ patient years) than did patients with a porcine valve (2.8/100 patient years) (p <0.002). Ejection fraction at rest was determined with multigated cardiac imaging 12 to 75 months post-operatively in 34 of 89 long-term survivors. The mean preoperative ejection fraction was 0.62 ± 0.09 (mean ± 1 standard deviation) and the mean postoperative ejection fraction was 0.50 ± 0.15 (p <0.001). When the preoperative value was compared with the postoperative value at rest the ejection fraction increased by 0.10 or more in 1 patient (3 percent), remained within ±0.09 of the preoperative value in 12 patients (35 percent) and decreased by 0.10 or greater in 21 patients (62 percent). Sixteen (94 percent) of 17 patients whose postoperative ejection fraction was greater than 0.50 were in functional class I postoperatively compared with 11 (65 percent) of 17 patients whose postoperative ejection fraction was 0.50 or less (p <0.05). No preoperative factor, including preoperative ejection fraction or cardiothoracic ratio, predicted the postoperative ejection fraction. A postoperative exercise ejection fraction was obtained in 29 patients, and an abnormal ejection fraction change with exercise (increase <0.05) was observed in 20 patients (69 percent). Patient age at the time of study correlated inversely with the change in ejection fraction from rest to exercise; no other variables were predictive.It is concluded that, in addition to age, only preoperative left ventricular function as measured by ejection fraction predicts survival in patients undergoing mitral valve replacement for isolated mitral regurgitation. Clinical recovery is good even though the majority of long-term survivors have a postoperative decrease in ejection fraction.     

Urban diabetic retinopathy teleophthalmology screening: results and impact at the service corridor

ObjectiveTo assess real-world results and the impact on a hospital service corridor for screening for DR through an urban community teleophthalmology service.MethodsRetrospective analysis at the hospital service corridor of 148 diabetics referred to it following DR teleophthalmology screening of 1185 type II diabetics.ResultsOf the screened diabetics, 87.4% (n = 1036) were exempted from face-to-face clinical examination (FFCE) in a traditional hospital eye care pathway and continued monitoring through teleophthalmology under a watch-and-wait attitude, while 12.5% (n = 148) were recommended for an FFCE. The FFCEs revealed that significant DR was present in 48.2% or in 5.6% of this screened diabetic population. Reasons for referral were findings of significant DR in 40.5%, of which diabetic macular edema (DME) represented 86.6%, other incidental significant sight-threatening findings represented 32.4% (4% of the screened diabetics), and insufficient image quality was obtained for the other 27.0%. Optical coherence tomography (OCT) imaging at FFCE confirmed DME in 26.4% and led to treatment. Patients referred for insufficient image quality showed significant pathology in 90.2%, of whom 63.4% underwent further monitoring or treatment. The readers requested the FFCEs for 148 patients within 1 month of the reading in 19.6%, 3 months in 26.3%, 4–12 months in 47.3%, and 12 months in 6.7% over the 34 months of the study. Compliance with FFCEs was 91.9%, absolute in 78.4% and relative in 21.5%. The availability of OCT at the imaging site would have impacted 4.5% of the screened diabetics by enabling teleophthalmology monitoring of 91.6%, identifying just-in-time interventions for DME treatments in 26.4% and reducing by 25% the need for referral of OCT-negative reader-identified DME.ConclusionThe FFCEs generated at the hospital service corridor by an urban community DR screening teleophthalmology project did not impact negatively on its services; moreover, the service corridor was exempted from providing FFCEs to 87.4% of the diabetic population it serves. This study may help provide cost-efficiency indications for a screening protocol that would include OCT availability at the imaging site and measure its positive effects. While DR of which DME was the main cause of referral for FFCE, incidental significant sight-threatening findings were significant and approached DR as a cause of referral; this supports the recommendation of continued human intervention in DR teleophthalmology screening at this time and for this population, until automatic computer-aided diagnosis systems can recognise biomarkers associated with other significant fundus diseases. As a secondary gain this project benefited individuals in need of care who were lost to the traditional eye care pathway. Good compliance with the follow-up FFCE further supports teleophthalmology in its effort to provide better access to DR screening.     

Lumbosacral fusion using the Boucher technique in combination with a posterolateral bone graft

This study evaluates the clinical and radiological results of using the facet screw fixation technique described by Boucher in combination with a posterolateral fusion rather than a posterior fusion for symptomatic degenerative disease of the lumbosacral junction. It is a retrospective review of 38 consecutive patients with an average follow-up of 28 months. Radiologically, all patients had a solid fusion. Clinically, 23 patients (60%) had excellent results, 11 patients (29%) good results, 3 patients (8%) fair results and 1 patient (3%) had a poor result. There were no neurological complications. The findings support the view that the Boucher technique of facet joint fixation in combination with a posterolateral fusion is a safe and effective method of dealing with chronic symptoms relating to degenerative changes at the lumbosacral junction. The authors stress the importance of patient selection and attention to operative technique if the clinical results are to correlate with the results of fusion.