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R J Gibbons

Publications and source records attributed to R J Gibbons.

At least 91 records · Page 5Linked to original sources
PubMed1998

Reversible perfusion defects on exercise tomographic thallium imaging in patients with and without collateral flow.

A consecutive series of patients underwent exercise thallium imaging and coronary angiography that identified single-vessel right coronary artery disease. Redistribution in the left anterior descending territory was significantly associated with the presence of left-to-right collaterals, whereas collaterals were significantly less frequent in individuals who did not exhibit redistribution.

Adult↗
PubMed1998

Usefulness of technetium-99m sestamibi infarct size in predicting posthospital mortality following acute myocardial infarction.

In this multicenter study, 249 patients who underwent tomographic technetium-99m sestamibi infarct size measurement at hospital discharge were followed up for a median duration of 7 months. Infarct size was significantly associated with mortality (chi-square = 5.8, p = 0.02) and could stratify patients into lower and higher risk subsets: 1-year mortality 2% for infarct size < 14% versus 8% for infarct size > or = 14% of the left ventricle.

Aged↗
PubMed1998

Correlation of resting first-pass left ventricular ejection fraction and resting myocardial infarct size.

This study determined the correlation between the extent of the resting perfusion defect by technetium-99m sestamibi tomographic imaging and the first-pass left ventricular (LV) ejection fraction (EF). A total of 1,955 patients underwent technetium-99m sestamibi tomographic imaging with measurement of first-pass resting LVEF. Twenty-five percent of patients had a prior history of myocardial infarction. First-pass LVEF was measured using a peripheral intravenous injection and a multicrystal gamma camera with standard software. Resting tomographic perfusion defect size (infarct size) was quantitated using previously published methods. Mean LVEF for the study group was 0.60 +/- 0.11. Mean LV infarct size was 5 +/- 11%. For the 1,265 patients (65% of the study group) with no measurable perfusion defect, the prevalence of a normal (> or = 0.50) LVEF was 96% (1,212 of 1,265 patients). For patients with a measurable defect (n = 690, 35%), the inverse linear correlation with LVEF was highly significant (r = -0.60, p <0.0001) but with wide confidence limits (SEE = 10 LVEF points), thereby limiting the predictive value in individual patients. Thus, in the absence of known cardiomyopathy, valvular heart disease, or left bundle branch block, patients without a quantifiable resting perfusion defect are highly likely to have a normal resting LVEF and may not require determination of LV function. For patients with resting perfusion defects, LVEF cannot be predicted with confidence and should therefore be measured.

Aged↗
PubMed1998

Prognostic value of vasodilator myocardial perfusion imaging in patients with left bundle-branch block.

BACKGROUND: The prognostic value of tomographic myocardial perfusion imaging with dipyridamole or adenosine in patients with left bundle-branch block has not been established. METHODS AND RESULTS: The study group consisted of 245 patients with left bundle-branch block who underwent tomographic (single photon emission tomography) myocardial perfusion imaging with thallium-201 (n=173) or technetium-99m sestamibi (n=72) and either dipyridamole (n=153) or adenosine (n=92) stress. Patients were prospectively classified into two groups. Patients were classified as "high risk" if they had (1) a large severe fixed defect (n=28), (2) a large reversible defect (n=36), or (3) cardiac enlargement and either increased pulmonary uptake (thallium) or a decreased resting ejection fraction (sestamibi) (n=20). The remaining 161 patients (66% of the study group) were at "low risk." Follow-up was 99% complete at 3+/-1.4 years. Three-year overall survival was 57% in the high-risk group compared with 87% in the low-risk group (P<.0001). Survival free of cardiac death/nonfatal myocardial infarction/cardiac transplantation was 55% in the high-risk group and 93% in the low-risk group (P<.0001). The presence of a high-risk scan had significant incremental prognostic value after adjustment for age, sex, diabetes, and previous myocardial infarction (P<.0001). Patients with a low-risk scan had an overall survival that was not significantly different from that of a US age-matched population (P=.86). CONCLUSIONS: Tomographic myocardial perfusion imaging with adenosine or dipyridamole stress provides important prognostic information in patients with left bundle-branch block, which is incremental to clinical assessment.

Adenosine↗
PubMed1998

Prognostic value of exercise thallium-201 imaging performed within 2 years of coronary artery bypass graft surgery.

OBJECTIVES: We sought to determine the prognostic capabilities of exercise thallium (Tl)-201 tomographic imaging performed relatively early (within 2 years) after coronary artery bypass graft surgery (CABG). BACKGROUND: Exercise testing is commonly performed after CABG, but few data exist demonstrating its prognostic value in this setting. METHODS: Four hundred eleven patients were followed up for a median duration of 5.8 years. Eleven prospectively chosen clinical, exercise and Tl-201 variables were tested for their associations with outcome end points by means of proportional hazards regression models. RESULTS: During follow-up there were 60 deaths from any cause, 53 initial cardiac deaths or nonfatal myocardial infarctions (MIs) and 22 late (>3 months after the Tl-201 study) revascularization procedures. The number of abnormal Tl-201 segments on the postexercise image was the only variable in the multivariate analyses to show a significant association with all three outcome end points: chi-square 7.3, p = 0.007 for overall mortality; chi-square 8.1, p = 0.004 for cardiac death or MI; chi-square 7.8, p = 0.005 for any cardiac event. Other independent predictors of outcome were exercise duration (chi-square 10.7, p = 0.001) and age (chi-square 3.9, p = 0.049) for overall mortality and exercise angina score (chi-square 8.7, p = 0.003) for cardiac death or MI. The 5-year survival rate free of cardiac death or MI was 93% for patients without angina and a normal image or small postexercise perfusion defect versus 71% for patients with angina and a medium or large defect. CONCLUSIONS: Exercise Tl-201 imaging performed within 2 years of CABG can stratify patients into low and high risk subgroups.

Aged↗
PubMed1998

Intercenter variability in outcome for patients treated with direct coronary angioplasty during acute myocardial infarction.

BACKGROUND: Direct coronary angioplasty is an effective therapy for acute myocardial infarction, but its success may be dependent on both ready availability and operator skill. The purpose of this study was to investigate the impact of the center performing direct coronary angioplasty for acute myocardial infarction while controlling for parameters known to affect outcome. METHODS AND RESULTS: The study group consisted of 99 patients with ST elevation who were treated with direct angioplasty in four high-volume centers. Patients were injected with technetium-99m sestamibi intravenously and then taken to the cardiac catheterization laboratory. Antegrade flow was graded before and after direct coronary angioplasty. Single photon emission computed tomography was performed 1 to 6 hours after injection to measure myocardium at risk and residual blood flow to the jeopardized zone using previously published quantitative methods. A repeat sestamibi injection and tomographic acquisition were performed at hospital discharge to measure actual infarct size. There were no significant differences by center for baseline clinical characteristics, mean myocardium at risk (29% to 37% left ventricle [LV]), time to reperfusion (3.1 to 4.1 hours), residual blood flow, infarct location, or antegrade flow. Despite these similarities, there were differences in outcome measures by center. Mean infarct size was as follows: center 1, 15%; center 2, 12%; center 3, 10%, center 4, 23% (all LV; p = 0.11 ). Mean left ventricular ejection fraction at discharge also demonstrated significant differences: center 1, 0.57; center 2, 0.47; center 3, 0.53; center 4, 0.47 (p = 0.002). The prevalence of Thrombolysis in Myocardial Infarction grade 3 flow after angioplasty significantly differed by center: center 1, 92%; center 2, 94%; center 3, 87%; center 4, 71 %; (p = 0.01). There was a low mortality rate for all four centers ranging from 0% to 6%. After adjustment for myocardium at risk, residual blood flow, and time to reperfusion, the primary outcome of the center where the angioplasty was performed was an independent determinant of both infarct size and left ventricular ejection fraction. CONCLUSION: The success of direct coronary angioplasty in reducing infarct size and preserving left ventricular function depends on the center performing the procedure. Direct measurement of the effectiveness of this reperfusion modality in community practice is required to assess the impact of this effect.

Aged↗
PubMed1998

Sex differences in ventricular function in patients with right bundle branch block.

BACKGROUND: Left ventricular function in patients with right bundle branch block is variable and depends on the population under study. This study assessed the implications of right bundle branch block for the estimation of resting left ventricular function in patients with right bundle branch and suspected coronary artery disease. METHODS AND RESULTS: Seventy-four patients with right bundle branch block, symptoms suggestive of coronary artery disease, and no electrocardiographic Q waves were compared with 649 patients with entirely normal electrocardiograms to assess the implications of right bundle branch block on resting left ventricular function. Resting ejection fraction was determined by radionuclide ventriculography. Patients with right bundle branch block were older (mean 65.0+/-10.2 years vs 53.8+/-11.1; P< .001) and had a lower mean ejection fraction (60%+/-11% vs 63%+/-9%; P< .005) compared with patients with normal electrocardiograms. There was a highly significant interaction between right bundle branch block and sex with respect to resting ejection fraction (P< .001). The mean ejection fraction for men with right bundle branch block was 57%+/-10% (17% with abnormal resting ejection fraction) compared with 62%+/-8% (7% with abnormal resting ejection fraction) for normal men. In contrast, the mean ejection fraction for women with right bundle branch block was 68%+/-9% (0% with abnormal resting ejection fraction) compared with 65%+/-9% (5% with abnormal resting ejection fraction) for normal women. CONCLUSIONS: Male patients with right bundle branch block and symptoms suggestive of coronary artery disease have a lower resting ejection fraction than mole patients with normal electrocardiograms. This difference is not seen in female patients.

Aged↗
PubMed1998

Prognostic value of exercise thallium-201 imaging in a community population.

BACKGROUND: The prognostic value of exercise thallium-201 imaging has been well established in referral patient populations at tertiary care centers, but these results may be influenced by referral bias. METHODS: This study was performed to evaluate the prognostic value of thallium imaging in a community-based population of 446 residents of Olmsted County, Minn. Eleven variables were prospectively selected and tested for their associations with outcome end points. RESULTS: Four variables (age, history of myocardial infarction, number of abnormal thallium segments on the postexercise images, and increased thallium lung uptake) contained the most independent prognostic information. For the end point overall mortality rate, the multivariate chi-square values were 17.2 (p < 0.0001) for age and 20.9 (p < 0.0001) for the number of abnormal thallium segments on the postexercise images. Five-year survival rate for patients older than the median age of 59 years with an abnormal scan was 84% versus 97% for patients < or = 59 years of age with a normal scan. CONCLUSION: Exercise thallium imaging was useful for prognostic purposes in this relatively low-risk community population, confirming the findings of referral population studies.

Adult↗
PubMed1998

Prevalence of spontaneous reperfusion and associated myocardial salvage in patients with acute myocardial infarction.

This study sought to determine the prevalence of spontaneous reperfusion of an infarct-related artery (IRA) and associated myocardial salvage in the absence of thrombolysis or angioplasty. Twenty-one patients with acute myocardial infarction received only heparin and aspirin. At a median of 18 hours after presentation, 12 patients (57%) had angiographic patency of the IRA. Technetium-99m sestamibi was injected acutely on presentation and again at hospital discharge. Acute and final perfusion defect sizes were measured. Their difference, myocardial salvage, was calculated along with salvage index (myocardial salvage/acute defect). Comparing patients with a patent versus occluded IRA, myocardium at risk was similar (16% +/- 12% vs 12% +/- 9% left ventricle, p = NS); however, myocardial salvage (9% +/- 9% vs -2% +/- 7% left ventricle, p = 0.01), and salvage index (0.62 +/- 0.37 vs 0.19 +/- 0.33, p = 0.01) were greater in patients with spontaneous reperfusion. Resolution of chest pain was greater in patients with a patent IRA (100% vs 55%, p = 0.003). Spontaneous reperfusion of the IRA occurs frequently in patients with acute myocardial infarction and is associated with significant myocardial salvage.

Aged↗
PubMed1998

Association between anterior ST depression and increased myocardial salvage following reperfusion therapy in patients with inferior myocardial infarction.

PURPOSE: To determine electrocardiographic features associated with myocardial salvage following reperfusion therapy in patients with inferior myocardial infarction. PATIENTS AND METHODS: Ninety-two consecutive patients with acute inferior myocardial infarction were treated with reperfusion therapy in a tertiary care center. Several features were measured on the presenting electrocardiogram, including the presence or absence of ST depression in the chest leads and the total magnitudes of ST elevation or depression, and were then evaluated for their association with myocardial salvage. Myocardial salvage (% of left ventricle) was the difference between myocardium at risk and final infarct size. Tomographic myocardial perfusion imaging with technetium-99m sestamibi was performed acutely to measure myocardium at risk and repeated prior to hospital discharge to measure final infarct size. RESULTS: The amount of myocardium at risk of infarction in the 92 patients was 19.1%+/-11.3% (range 1% to 68%), and the final infarct size was 10.6%+/-10.0% (range 0% to 45%). Thus, myocardial salvage in the 92 patients was 8.5%+/-8.4% (range -11% to 35%) of the left ventricle, or 0.51+/-0.38 (range 0.0 to 1.0) when expressed as a fraction of the myocardium at risk (salvage index). The presence or absence of anterior ST depression was the only one of seven electrocardiographic variables that was associated with myocardial salvage. Myocardial salvage was significantly greater in patients with anterior ST depression compared with those without it (10.6%+/-9.0% versus 5.9%+/-6.7%, P=0.025). Myocardium at risk was significantly greater in patients with anterior ST depression compared with those without the depression (22.8%+/-12.2% versus 14.6%+/-8.3%, P=0.0006), and infarct size tended to be larger (12.1%+/-10.4% versus 8.7%+/-9.4%, P=0.10). Myocardial salvage as a fraction of the myocardium at risk (salvage index) was similar between the two patient groups (0.52+/-0.37 versus 0.50+/-0.39, P=NS). CONCLUSION: The presence of anterior ST depression during inferior myocardial infarction identifies a group of patients with the potential for greater myocardial salvage with reperfusion therapy. Such patients derive greater absolute benefit from reperfusion therapy because they have a larger amount of myocardium at risk, although their response to therapy (salvage index) is not intrinsically different.

Adult↗
PubMed1998

Clinical determinants of hemodynamic and symptomatic responses in 2,000 patients during adenosine scintigraphy.

OBJECTIVE: To determine whether subsets of patients referred for a clinically indicated radionuclide adenosine stress study respond differently to a standard infusion of adenosine. MATERIAL AND METHODS: We assessed multiple clinical and hemodynamic variables in the first 2,000 patients who underwent adenosine perfusion studies in our laboratory. A relevant clinical variable was defined as one that was significantly associated with changes in heart rate and blood pressure during adenosine infusion. Relevant clinical variables that were most significantly related to hemodynamic variables included age, gender, rhythm (atrial fibrillation), diabetes, and left ventricular function. These variables were then related to symptomatic responses (adverse effects) to adenosine infusion. To determine whether the different peripheral responses to adenosine reflected clinically important differences in coronary vasodilatation, we compared perfusion imaging with coronary angiographic findings in the 408 patients who underwent both studies within 6 months of each other. RESULTS: The decrease in systolic blood pressure was greater and the reflex tachycardia was less in patients 70 years of age or older and in those with insulin-dependent diabetes in comparison with younger patients and those without type 1 diabetes. Men had smaller decreases in blood pressure and smaller increases in heart rate than did women. Patients with atrial fibrillation and those with left ventricular ejection fraction less than 40% had smaller decreases in blood pressure and smaller increases in heart rate than did those in sinus rhythm or those with an ejection fraction of 40% or more. Age 70 years or older, male gender, atrial fibrillation, and left ventricular ejection fraction less than 40% were associated with fewer symptoms and less severe chest pain in comparison with patients without these variables. For patients with coronary angiograms, the relationship between coronary artery disease evident on angiography and perfusion abnormalities noted on scintigraphy was not different for any of the relevant clinical variables. CONCLUSION: Common clinical patient subsets are associated with different peripheral hemodynamic and symptomatic responses to infusion of adenosine. Despite these observations, however, the ability to detect coronary artery disease with perfusion imaging is not obviously altered.

Adenosine↗
PubMed1998

Time to therapy and salvage in myocardial infarction.

OBJECTIVES: This study sought to examine the influence of time to reperfusion on myocardial salvage. BACKGROUND: Major trials of reperfusion therapy for myocardial infarction (MI) have demonstrated improved outcome for patients achieving earlier reperfusion. However, some patients experience significant benefit despite delayed reperfusion. METHODS: Fifty-five patients with a first anterior MI underwent successful reperfusion therapy (angioplasty or thrombolysis). Technetium-99m (Tc-99m) sestamibi was injected before reperfusion therapy and again at hospital discharge to determine the myocardial salvage index for each patient. Residual flow to the infarct territory was assessed by the nadir of the Tc-99m sestamibi count-profile curve. RESULTS: The salvage index showed wide variability (range -0.04 to 1.0), and extreme values were seen in 34.5% of the group (<0.10 in 9%, >0.90 in 25%). A high salvage index was associated with reperfusion therapy before 2 h (p=0.02) or good residual blood flow (p < 0.01). For the 10 patients who received reperfusion therapy within 2 h, residual blood flow was not correlated with salvage (p=0.12). For the 45 patients treated after 2 h, residual blood flow correlated significantly with salvage (r=0.57, p < 0.0001). There was a significant interaction (p < 0.05) between residual blood flow and time to therapy, indicating that the effect of each variable on salvage depended on the value of the other. Multiple historic and hemodynamic variables were examined, but none demonstrated any association with residual flow or myocardial salvage. CONCLUSIONS: In patients with acute MI, successful reperfusion therapy within 2 h is associated with the greatest degree of myocardial salvage. For patients treated after 2 h, residual blood flow to the infarct-related territory appears to be the most important determinant of myocardial salvage.

Adult↗
PubMed1998

Intravenous adenosine and lidocaine in patients with acute myocardial infarction.

OBJECTIVES: A pilot study was designed to assess the safety of combined intravenous adenosine and lidocaine in patients with acute myocardial infarction and to estimate the likelihood of a beneficial effect on final infarct size. BACKGROUND: Adenosine plus lidocaine reduces infarct size in animals, but the safety and efficacy in human beings is unknown. METHODS AND RESULTS: Adenosine (70 microg/kg per minute intravenous infusion) plus lidocaine (1 mg/kg intravenous bolus injection and 2 mg/kg per minute infusion) was given to 45 patients with acute myocardial infarction. Patients underwent immediate balloon angioplasty without preceding thrombolytic therapy. Myocardial perfusion defects were measured with serial technetium 99m sestamibi studies. One patient developed persisting hypotension in conjunction with a large inferolateral myocardial infarction. Transient hypotension in three other patients resolved with a reduction in adenosine. Advanced atrioventricular block was never observed. Other adverse events (including atrial fibrillation, ventricular tachyarrhythmia, bradycardia, and respiratory distress) occurred at low frequencies, as expected for patients with acute myocardial infarction. An initial median perfusion defect of 45% of the left ventricle (60% for anterior infarction, 17% for nonanterior infarction) was observed. At hospital discharge (mean +/- SD = 4.3 +/- 2.1 days) the median value was 12%, and at 8 +/- 4 weeks it was 3% (7% for anterior infarction, 0% for nonanterior infarction); 14 patients had no measurable follow-up. Compared with historical control patients, prehospital discharge measurements were not different but late perfusion defects were improved. CONCLUSIONS: Treatment with intravenous adenosine and lidocaine during acute myocardial infarction has sufficient safety and potential for improved myocardial salvage. Randomized studies are justified.

Adenosine↗
PubMed1998

Actinomyces naeslundii genospecies 1 and 2 express different binding specificities to N-acetyl-beta-D-galactosamine, whereas Actinomyces odontolyticus expresses a different binding specificity in colonizing the human mouth.

A total of 102 strains of Actinomyces were isolated from teeth, buccal mucosa and tongue in eight individuals. The isolates were characterized by multivariate statistical analyses of phenotypic characteristics, serotyping and binding to beta-linked galactosamine (N-acetyl-beta-D-galactosamine) and acidic proline-rich protein structures. Based on these characteristics, isolates were classified into three major groups: (i) Isolates of Actinomyces naeslundii genospecies 2 were the dominant species on teeth and buccal mucosa and bound commonly to N-acetyl-beta-D-galactosamine (63 of 63 isolates) and acidic proline-rich proteins (63 of 63 isolates), regardless of tissue origin. They all exhibited a N-acetyl-beta-D-galactosamine binding specificity signified by N-acetyl-beta-D-galactosamine-inhibitable coaggregation with the streptococcal strains LVG1, GVE1, 24892 and MPB1; (ii) Isolates of A. naeslundii genospecies 1 were prevalent on teeth in certain individuals and bound commonly to N-acetyl-beta-D-galactosamine (20 of 20 isolates), but less commonly to acidic proline-rich proteins (5 of 20 isolates). They all possessed another N-acetyl-beta-D-galactosamine specificity, i.e. N-acetyl-beta-D-galactosamine-inhibitable coaggregation with the same streptococcal strains except for strain MPB1; (iii) Isolates of Actinomyces odontolyticus, the dominant species on the tongue (17 of 19 isolates), bound commonly to unknown structures on streptococci (17 of 19 isolates) but rarely to N-acetyl-beta-D-galactosamine (2 of 19 isolates) or acidic proline-rich proteins (3 of 19 isolates). In conclusion, A. naeslundii genospecies 1 and 2 exhibit different patterns of N-acetyl-beta-D-galactosamine and acidic proline-rich protein specificities to colonize dental and buccal mucosa surfaces, whereas A. odontolyticus utilizes another specificity to colonize the tongue.

Acetylgalactosamine↗