Exercise thallium-201 scintigraphy in the diagnosis and prognosis of coronary artery disease

Multi Vessel Coronary Artery Disease Presenting as a False Negative Myocardial Perfusion Imaging and True Positive Exercise Tolerance Test: A Case of Balanced Ischemia

Non-invasive investigations play an important role in the early diagnosis of coronary artery disease. Although the stress test is an easily available investigation for the diagnosis of obstructive coronary artery disease, its results are affected by the pretest probability. Myocardial perfusion imaging (MPI) is one of the commonly performed non-invasive cardiac imaging. The common reasons for false-negative exercise MPI are reported to be inadequate exercise, a lower dose of radio-tracer, small area of perfusion defect, and ischemia caused by left circumflex or its branches. Balanced ischemia is one of the rare causes of false-negative MPI. In this case report, we present a 73-year-old gentleman who presented with chest pain and shortness of breath. An exercise electrocardiogram (ECG) at five metabolic equivalents was positive for symptoms and electrocardiographic evidence of ischemia, but the myocardial perfusion image did not show ischemia. An invasive coronary angiogram was done due to high-risk exercise ECG, which revealed severe three-vessel coronary artery disease. Although the false-negative myocardial perfusion scan in the presence of a positive exercise electrocardiogram is unusual, it should not be ignored. Positive exercise ECG with the reproduction of symptoms indicates a high probability of critical coronary artery disease, irrespective of perfusion defects.

Diagnostic Performance of Dobutamine Stress Echocardiography in End-Stage Liver Disease

OBJECTIVES

This study determined the test performance of dobutamine stress echocardiography (DSE) in end-stage liver disease (ESLD).

BACKGROUND

The reported sensitivity of DSE in ESLD has been variable.

METHODS

Data from 633 ESLD patients who had coronary angiography within 6 months after DSE was analyzed.

RESULTS

The prevalence of coronary arterial disease (CAD) (≥70% stenosis by quantitative angiography) was 12% (74 of 633 patients). DSE sensitivity was 24% (17 of 72 patients), and specificity was 90% (503 of 559 patients). The positive and negative predictive values were 23% (17 of 73 patients) and 90% (503 of 558 patients), respectively. Stratifying the cohort into low-, intermediate-, and high-risk CAD groups yielded sensitivities of 0%, 21%, and 32%, respectively. Independent predictors of an accurate ischemic DSE result included left ventricular internal dimension at end-diastole (LVIDd) >4.8 cm and assigning ischemia based on tardokinesis or lack of low-to-peak dose hyperkinesis (p < 0.05 for all). DSE sensitivity was 38% in LVIDd >4.8 cm versus 13% with LVIDd ≤4.8 cm (p = 0.013). The sensitivity was 67% when tardokinesis or lack of hyperkinesis was considered abnormal versus 15% (p < 0.001) for readings that did not consider tardokinesis or lack of hyperkinesis abnormal. There was a higher frequency of cardiac events in patients with significant CAD who had abnormal (45%) versus normal (18%) DSE (p = 0.01).

CONCLUSIONS

The sensitivity of DSE in ESLD was low. DSE sensitivity was higher for those with larger cavity dimension and when tardokinesis or lack of hyperkinesis was considered abnormal. An abnormal DSE in those with significant CAD was associated with worse outcome.

Clinical significance of right ventricular activity on treadmill thallium-201 myocardial single-photon emission computerized tomography using cadmium-zinc-telluride cameras

OBJECTIVE

Identification of right ventricular (RV) abnormalities is important in patients with suspected coronary artery disease (CAD). RV activity can be better visualized on myocardial single-photon emission computerized tomography (SPECT) using a higher sensitivity cadmium-zinc-telluride (CZT) detector. The aim of this study was to investigate the clinical significance of RV/left ventricular (LV) uptake ratios during exercise thallium-201 SPECT using CZT detectors.

PATIENTS AND METHODS

A total of 102 patients underwent treadmill ECG-gated SPECT, coronary angiography, and echocardiography. SPECT myocardial perfusion was interpreted using a 17-segment model and a 0-4-point scale. RV/LV uptake ratios were calculated on the basis of maximum counts per pixel within the entire RV and LV walls. The relationships between RV/LV uptake ratio and gated SPECT, presence of CAD (≥50% stenosis in the left main or ≥70% in the main branches), demographics, and echocardiographic parameters were analyzed.

RESULTS

Stress RV/LV ratios correlated positively with the presence of left main or multivessel disease, and tricuspid regurgitation maximum pressure gradient. After multivariate regression, stress/rest RV/LV ratios correlated positively with mitral flow deceleration time, age, female sex, and use of β-blockers.

CONCLUSION

RV/LV uptake ratios on the basis of exercise myocardial perfusion SPECT imaging using CZT cameras are useful for the detection of severe CAD and could serve as an indicator of pulmonary hypertension and LV diastolic dysfunction.

Correlation between transient ischemic dilatation (TID) and coronary artery disease in Saudi male patients

OBJECTIVE

A high transient ischemic dilatation ratio (TID) for the left ventricle (LV) from a gated myocardial perfusion imaging (G-MPI) study is widely believed to be associated with significant coronary artery disease (CAD). We have investigated the relationship between TID and CAD for our male Saudi Arabian patient population.

METHODS

In this retrospective study, all male Saudi Arabian patients who underwent a two-day G-MPI study using Tc99m MIBI during the year 2011 having a TID ⩾ 1.20 were included. Quantitative perfusion and gated parameters were obtained using Cedar Sinai's AutoQuant software version 3.0, 2003, Means of summed stress scores, summed rest scores and summed difference scores (SSS, SRS, SDS, respectively), stress and rest ejection fraction (EF) were calculated. Visual interpretation was performed to classify the perfusion as normal, fixed, mixed (fixed and reversible defects), single reversible or multiple reversible defects. Coronary angiograms were assessed as normal with no CAD, single vessel, two-vessel or three-vessel disease. Correlations between the TID and other parameters were studied using analysis of variance (ANOVA) with IBM-SPSS version 20.

RESULTS

A total of 52 male patients had a high TID of ⩾1.20 (mean 1.30 ± 0.13). Ten patients had a SSS of 0-3 and 16 were classified as normal by visual assessment. Stress EF (mean 50.4 ± 12%) was lower than the rest EF (mean 56.6 ± 12.8%) with the difference being statistically significant (Students paired t-test, p = 0.001). Angiography results were available in 44 patients, 3 having a normal angiogram, 24 having three vessel disease, 7 having two vessel disease and 10 having one vessel disease. Five patients with normal perfusion and SSS = 0-3 had CAD as seen on a coronary angiography. CAD on coronary angiography showed a significant correlation with perfusion abnormalities as assessed by visual interpretation (p = 0.002). TID showed a significantly correlation with both perfusion abnormalities (p = 0.009), as assessed by visual interpretation, and with Summed difference scores, SDS (p = 0.000).

CONCLUSION

A high TID on G-MPI was a very sensitive indicator of significant CAD. In patients with normal perfusion and high TID further workup is warranted.

Temporal trends in the frequency of inducible myocardial ischemia during cardiac stress testing: 1991 to 2009

OBJECTIVES

This study sought to assess whether the frequency of inducible myocardial ischemia during stress-rest single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has changed over time.

BACKGROUND

The prevalence of cardiac death and other clinical cardiac events have declined in recent decades, but heretofore no study has examined if there has been a temporal change in the frequency of inducible myocardial ischemia during cardiac stress testing.

METHODS

We assessed 39,515 diagnostic patients undergoing stress-rest MPI between 1991 and 2009. Patients were assessed for change in demographics, clinical symptoms, risk factors, and frequency of abnormal and ischemic SPECT-MPI.

RESULTS

There was a marked progressive decline in the prevalence of abnormal SPECT studies, from 40.9% in 1991 to 8.7% in 2009 (p < 0.001). Similarly, the prevalence of ischemic SPECT-MPI declined, from 29.6% to 5.0% (p < 0.001), as did the prevalence of severe ischemia. The decline of SPECT-MPI abnormality occurred among all age and symptom subgroups, falling to only 2.9% among recent exercising patients without typical angina. We also noted a progressive trend toward performing more pharmacological rather than exercise stress in all age and weight groups, and pharmacological stress was more likely than exercise to be associated with SPECT-MPI abnormality (odds ratio: 1.43, 95% confidence interval: 1.3 to 1.5; p < 0.001).

CONCLUSIONS

Over the past 2 decades, the frequency and severity of abnormal stress SPECT-MPI studies has progressively decreased. Notably, the frequency of abnormal SPECT-MPI is now very low among exercising patients without typical angina. These findings suggest the need for developing more cost-effective strategies for the initial work-up of patients who are presently at low risk for manifesting inducible myocardial ischemia during cardiac imaging procedures.

Single Dose Treatments in Tropical Infectious Diarrhoea

Single dose treatments have the important advantages of simple administration, excellent compliance, short-lived side effects (if any) and short period of drug pressure. However, drugs used for single dose treatments must possess important characteristics, namely, long half-life, effective concentration in tissues over a long period, and low toxicity. In tropical medicine, such drugs are an important advance in the treatment of malaria (mefloquine and halofantrine), schistosomiasis (praziquantel and metrifonate), filariasis (ivermectin), and genitourinary tract and intestinal infections.

Intestinal infections are one of the most frequent problems in tropical medicine. While a large number of cases of diarrhoea are of viral (rotavirus) or bacterial (Salmonella, Escherichia coli) origin, necessitating only oral rehydration, some are of parasitological origin (Giardia, Entamoeba histolytica, Strongyloides, Trichuris, Schistosoma) and can be cured by a single dose treatment (tinidazole, secnidazole, ivermectin, albendazole, praziquantel). Secnidazole is the nitroimidazole with the longest half-life and is, therefore, used in single dose treatments for Giardia, acute intestinal amoebiasis and E. histolytica cyst carriers. Single dose treatments of most intestinal parasites will be a major advance in the management of tropical infectious diarrhoea. In the next decade, opportunistic intestinal infections (Cryptosporidium, Isospora, Enterocytozoon) in AIDS patients that are refractory to treatment could be the major problem.

Gastric and intestinal barrier impairment in tropical enteropathy and HIV: limited impact of micronutrient supplementation during a randomised controlled trial

BACKGROUND

Although micronutrient supplementation can reduce morbidity and mortality due to diarrhoea, nutritional influences on intestinal host defence are poorly understood. We tested the hypothesis that micronutrient supplementation can enhance barrier function of the gut.

METHODS

We carried out two sub-studies nested within a randomised, double-blind placebo-controlled trial of daily micronutrient supplementation in an urban community in Lusaka, Zambia. In the first sub-study, gastric pH was measured in 203 participants. In the second sub-study, mucosal permeability, lipopolysaccharide (LPS) and anti-LPS antibodies, and serum soluble tumour necrosis factor receptor p55 (sTNFR55) concentrations were measured in 87 participants. Up to three stool samples were also analysed microbiologically for detection of asymptomatic intestinal infection. Gastric histology was subsequently analysed in a third subset (n = 37) to assist in interpretation of the pH data. Informed consent was obtained from all participants after a three-stage information and consent process.

RESULTS

Hypochlorhydria (fasting gastric pH > 4.0) was present in 75 (37%) of participants. In multivariate analysis, HIV infection (OR 4.1; 95%CI 2.2-7.8; P < 0.001) was associated with hypochlorhydria, but taking anti-retroviral treatment (OR 0.16; 0.04-0.67; P = 0.01) and allocation to micronutrient supplementation (OR 0.53; 0.28-0.99; P < 0.05) were protective. Hypochlorhydria was associated with increased risk of salmonellosis. Mild (grade 1) gastric atrophy was found in 5 participants, irrespective of Helicobacter pylori or HIV status. Intestinal permeability, LPS concentrations in serum, anti-LPS IgG, and sTNFR55 concentrations did not differ significantly between micronutrient and placebo groups. Anti-LPS IgM was reduced in the micronutrient recipients (P <0.05).

CONCLUSIONS

We found evidence of a specific effect of HIV on gastric pH which was readily reversed by anti-retroviral therapy and not mediated by gastric atrophy. Micronutrients had a modest impact on gastric pH and one marker of bacterial translocation.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN31173864.

Review of Movahed's sign (D shaped left ventricle seen on gated SPECT) suggestive of right ventricular overload

Recently, D shaped ventricle seen on gated SPECT imaging (Movahed's sign) has shown to correlate with right ventricular overload similar to the D shape ventricle seen on echocardiography. Right ventricle (RV) imaging during gated SPECT studies is challenging because of the low tracer uptake due to relatively smaller right ventricular myocardial mass and lower coronary flow to the RV. Increased mass or workload causes higher tracer uptake in the RV wall secondary to increase in RV wall thickness and higher coronary flow. Furthermore, increased RV volume or pressure load can cause displacement of the septum towards the left ventricle causing septal flattening and a D shaped configuration of the left ventricular septum. This is an important finding that should be a part of nuclear gated SPECT interpretation.

Absence of an Association Between Enteric Parasites in the Manifestations and Pathogenesis of HIV Enteropathy in Gay Men

49 gay men confirmed to be infected with the human immunodeficiency virus (HIV) and 9 HIV seronegative gay men participated in a pilot study comparing clinical status and enteric parasite load with gastrointestinal structure, function and symptomatology. Cases included 16/49 (33%) men who were CDC stage II, 7/49 (14%) who were CDC stage III, and 26/49 (53%) who were CDC stage IV. The mean CD4-lymphocyte count was 476 +/- 199 (SD)/microliter. The prevalence of enteric parasitic flora was similar in HIV seropositive patients and controls. Seven cases had enteric infection with pathogenic agents including 3 patients with Entamoeba histolytica, and 4 patients with Giardia lamblia, one of whom also had cryptosporidiosis. Other cases were most frequently colonized with Blastocystis hominis (44%) and Endolimax nana (41%) regardless of the HIV clinical status. HIV seropositive patients with enteric parasitic colonization tended to have lower mean levels of serum IgA than cases without parasites. Duodenal morphometric mucosal changes demonstrated a significant decrease in the mean villous height (p < 0.01) with no elongation of the crypt depth in HIV-infected patients with and without diarrhea compared to controls. Despite gastrointestinal symptoms including diarrhea and weight loss being more prevalent in HIV infected individuals than controls, no correlations were found between the presence of particular enteric parasites, gastrointestinal symptomatology, the clinical HIV status of the CD4-lymphocyte count, the malabsorption of D-xylose or morphometric changes in the duodenum.(ABSTRACT TRUNCATED AT 250 WORDS)

Women with high exercise tolerance and the role of myocardial perfusion imaging

BACKGROUND

Myocardial perfusion imaging (MPI) provides incremental diagnostic and prognostic information, even in patients with high exercise tolerance.

HYPOTHESIS

Myocardial perfusion imaging provides significant diagnostic value, specifically in women with high exercise tolerance.

METHODS

Our study population consisted of all women who underwent exercise MPI in our Department from January 1992 to June 1996 and reached at least Stage IV in the Bruce protocol. Patients were divided into those with known and those with possible coronary artery disease (CAD). All patients were followed for 3 years from the performance of MPI.

RESULTS

Of 4,803 women who underwent myocardial perfusion imaging, 3,183 had exercise stressing, and of those, 311 reached at least Stage IV in the Bruce protocol. Of these 311 MPI scans, only 23 (7.4%) were abnormal (reversible, fixed, or mixed) and the remaining 288 (92.6%) were normal. Of the 82 patients with known CAD, 13 (15.8%) had an abnormal MPI, while only 10 (4.4%) of the 229 patients with possible CAD. No myocardial infarction or cardiac death occurred within 3 years; one patient with normal MPI needed revascularization.

CONCLUSION

In women with high exercise tolerance, especially in those without already known CAD, the yield of MPI is very low. Women with high exercise tolerance have an excellent prognosis.

Susceptibility to intestinal infection and diarrhoea in Zambian adults in relation to HIV status and CD4 count

BACKGROUND

The HIV epidemic in sub-Saharan Africa has had a major impact on infectious disease, and there is currently great interest in the impact of HIV on intestinal barrier function. A three year longitudinal cohort study in a shanty compound in Lusaka, Zambia, carried out before anti-retroviral therapy was widely available, was used to assess the impact of HIV on susceptibility to intestinal infectious disease. We measured the incidence and seasonality of intestinal infection and diarrhoea, aggregation of disease in susceptible individuals, clustering by co-habitation and genetic relatedness, and the disease-to-infection ratio.

METHODS

Adults living in a small section of Misisi, Lusaka, were interviewed every two weeks to ascertain the incidence of diarrhoea. Monthly stool samples were analysed for selected pathogens. HIV status and CD4 count were determined annually.

RESULTS

HIV seroprevalence was 31% and the prevalence of immunosuppression (CD4 count 200 cells/microL or less) was 10%. Diarrhoea incidence was 1.1 episodes per year and the Incidence Rate Ratio for HIV infection was 2.4 (95%CI 1.7-3.3; p < 0.001). The disease-to-infection ratio was increased at all stages of HIV infection. Aggregation of diarrhoea in susceptible individuals was observed irrespective of immunosuppression, but there was little evidence of clustering by co-habitation or genetic relatedness. There was no evidence of aggregation of asymptomatic infections.

CONCLUSION

HIV has an impact on intestinal infection at all stages, with an increased disease-to-infection ratio. The aggregation of disease in susceptible individuals irrespective of CD4 count suggests that this phenomenon is not a function of cell mediated immunity.

Parasites in patients with malabsorption syndrome: a clinical study in children and adults

BACKGROUND

Intestinal parasites not only cause diarrheal diseases but also significant malabsorption. Literature on the role of parasites, such as intestinal coccidia and microsporidia in malabsorption syndrome is limited.

METHODS

Three consecutive stool samples from 50 adult and 50 children patients with malabsorption syndrome and an equal number of healthy controls without diarrhea were examined for intestinal coccidia, microsporidia and other intestinal parasites by wet mount, Kinyoun's modified acid-fast staining and chromotrope 2R staining.

RESULTS

Celiac disease was the commonest cause of malabsorption syndrome in both adults (52%) and children (74%). Forty (80%) and 41 (82%) adults and children, respectively, with malabsorption syndrome were infected with parasites. These results were significantly higher in comparison to those from the healthy adults and children controls (22% and 16%), respectively (P < 0.001). Of them, 48% and 46% of the adults and children, respectively, with malabsorption had pathogenic parasitic infections. The pathogenic parasites detected in adults were Giardia lamblia 12 (24%), E. histolytica / dispar 5 (10%), Ancylostoma duodenale 4 (8%), H. nana 2 (4%) and Cyclospora cayetanensis 1 (2%). The pathogenic parasites detected in children with malabsorption syndrome were Giardia lamblia 8 (16%), Cryptosporidium 7 (14%), E. histolytica / dispar 3 (6%), Ancylostoma duodenale 3 (6%), Isospora belli 1 (2%), and H. nana 1 (2%). None of the stool samples from healthy controls were positive for Cryptosporidium spp., Cyclospora and Isospora belli. All the patients infected with intestinal coccidia were HIV sero-negative.

CONCLUSION

Celiac disease is the most common cause of malabsorption syndrome in both adults and children. These people harbor significantly more pathogenic parasites and are more frequently colonized with harmless commensals as compared to healthy controls. Intestinal coccidia are associated with malabsorption syndrome, particularly in malnourished children.

Risk Stratification Using Stress Echocardiography: Incremental Prognostic Value over Historic, Clinical, and Stress Electrocardiographic Variables Across a Wide Spectrum of Bayesian Pretest Probabilities for Coronary Artery Disease

OBJECTIVES

We sought to evaluate the risk stratification ability and incremental prognostic value of stress echocardiography over historic, clinical, and stress electrocardiographic (ECG) variables, over a wide spectrum of bayesian pretest probabilities of coronary artery disease (CAD).

BACKGROUND

Stress echocardiography is an established technique for the diagnosis of CAD. However, data on incremental prognostic value of stress echocardiography over historic, clinical, and stress ECG variables in patients with known or suggested CAD is limited.

METHODS

We evaluated 3259 patients (60 +/- 13 years, 48% men) undergoing stress echocardiography. Patients were grouped into low (<15%), intermediate (15-85%), and high (>85%) pretest CAD likelihood subgroups using standard software. The historical, clinical, stress ECG, and stress echocardiographic variables were recorded for the entire cohort. Follow-up (2.7 +/- 1.1 years) for confirmed myocardial infarction (n = 66) and cardiac death (n = 105) was obtained.

RESULTS

For the entire cohort, an ischemic stress echocardiography study confers a 5.0 times higher cardiac event rate than the normal stress echocardiography group (4.0% vs 0.8%/y, P < .0001). Furthermore, Cox proportional hazard regression model showed incremental prognostic value of stress echocardiography variables over historic, clinical, and stress ECG variables across all pretest probability subgroups (global chi2 increased from 5.1 to 8.5 to 20.1 in the low pretest group, P = .44 and P = .01; from 20.9 to 28.2 to 116 in the intermediate pretest group, P = .47 and P < .0001; and from 17.5 to 36.6 to 61.4 in the high pretest group, P < .0001 for both groups).

CONCLUSIONS

A normal stress echocardiography portends a benign prognosis (<1% event rate/y) in all pretest probability subgroups and even in patients with high pretest probability and yields incremental prognostic value over historic, clinical, and stress ECG variables across all pretest probability subgroups. The best incremental value is, however, in the intermediate pretest probability subgroup.

Factors contributing to spontaneous Enterocytozoon bieneusi infection in simian immunodeficiency virus-infected macaques

BACKGROUND

A cohort of SIV-infected macaques had been used to investigate the effect of dietary supplement, immune status, SIV/AIDS disease progression and serum micronutrients levels on spontaneous acquisition of Enterocytozoon bieneusi infection in SIV-infected macaques.

METHODS

Twenty-four SIV-infected macaques were randomized into 2 groups. One group received a vitamin/mineral supplementation and a second group received a placebo. Both groups were examined for E. bieneusi infection.

RESULTS

SIV-infected macaques were more prone to acquire E. bieneusi with the progression of SIV/AIDS, and the increased shedding of infectious spores was directly associated with decreased CD4 lymphocyte and increased circulating SIV, in both supplemented and unsupplemented groups of animals. Dietary supplementation, body composition factors and serum micronutrients levels however had no association with the acquisition of E. bieneusi infection in these animals.

CONCLUSIONS

Acquisition of E. bieneusi infection is related to SIV disease progression, CD4 counts and viral load but independent of changes in body composition and serum micronutrient levels.

Food and water safety for persons infected with human immunodeficiency virus

Public health and food safety experts estimate that millions of episodes of illnesses annually can be traced to contaminated food and water. Food and water safety is extremely important to persons infected with the human immunodeficiency virus (HIV) or with acquired immunodeficiency syndrome (AIDS). A compromised immune system causes people with HIV or AIDS to be more susceptible to foodborne illness from eating foods that are unsafely handled and poorly prepared and from using water from unsafe sources. Food- and waterborne illnesses can cause diarrhea, nausea, and vomiting that can lead to weight loss. These illnesses can be minimized or prevented if proper precautions are taken.

Visual acuity following cataract surgeries in relation to preoperative appropriateness ratings

The authors initiated this study to consider if the formal preoperative assessment of appropriate or inappropriate utilization of cataract surgery by an expert panel could predict postoperative improvement or decline in visual acuity. They evaluated the association between ratings of appropriateness, as determined by the RAND-UCLA method, and measurements of postoperative visual acuity using Fisher's exact tests for tables greater than 2 x 2. For 768 patients, improvement of at least 2 Snellen chart lines occurred in 89% of surgeries rated as appropriate or appropriate and crucial, 68% rated as uncertain, and 36% rated as inappropriate (P < 0.0001, Fisher's exact test). These results provide evidence supporting the validity of the RAND-UCLA method to assess the appropriateness of surgery.

HIV1 and the gut in the era of highly active antiretroviral therapy

The gut and its gut-associated lymphoid tissue serve as a preferential site for HIV1 entry, active viral replication, reservoir, and HIV-mediated CD4 cell apoptosis. The widespread use of highly active antiretroviral therapy (HAART) has resulted in a significant decrease in the incidence of opportunistic enteric pathogens as a consequence of immune recovery. Nonetheless, patients with advanced HIV1 disease who were recently diagnosed or have poor response to HAART can still suffer from opportunistic infections with pathogens such as Cryptosporidium, microsporidia, Isospora belli, Cyclospora cayetanensis, Mycobacterium avium complex, and cytomegalovirus, among others. This review describes the impact of HIV1 infection on gut immune function, the salient features of the most common opportunistic enteric pathogens and HIV-associated enteropathy, and the effects of immune reconstitution after introduction of HAART.

Exercise testing scores as an example of better decisions through science

INTRODUCTION

The application of common statistical techniques to clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners function as gatekeepers and decide which patients must be referred to the cardiologist, they need to optimally use the basic tools they have available (i.e., history, physical exam, and the exercise test).

METHODS

Review of the literature with a focus on the scientific techniques for aiding the decision-making process.

RESULTS

Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power when compared using receiver-operating-characteristic curves with the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers as part of information management systems can calculate complicated equations to provide scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Scores have also been compared with physician judgment and been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists, and often better than nonspecialists.

CONCLUSION

Multivariate scores can empower the clinician to assure the cardiac patient with access to appropriate and cost-effective cardiological care.

Relationship between exercise-induced ST segmental depression and myocardial ischemia assessed by technetium-99m tetrofosmin SPECT imaging in patients with inferior Q wave myocardial infarction

BACKGROUND

ST segment depression (STD) is a standard electrocardiographic sign of myocardial ischemia. Although STD may represent reciprocal changes in patients with previous myocardial infarction, studies of reciprocal changes during exercise testing are scarce.

METHODS

From December 1999 to December 2000, 160 patients (119 males, 41 females, mean age 54 +/- 8 years), undergoing, maximal or symptom-limited exercise treadmill test (Bruce-protocol), myocardial perfusion scintigraphy using technetium-99m tetrofosmin single photon emission computed tomography (SPECT) imaging, within 30 days of an uncomplicated inferior Q wave myocardial infarction. The location of STD at the electrocardiogram (ECG) was defined as anterior (V1-4), high lateral (I, aVL), and lateral (V5-6). Ischemia was defined as reversible perfusion abnormalities.

RESULTS

STD occurred in anterior leads in 29 patients (18.1%), in the lateral leads in 41 patients (25.6%), in the high lateral leads in 20 patients (12.5%). In 70 patients (43.8%) no significant STD occurred during the exercise test. ST segment elevation occurred in 28 patients (17.5%) in inferior leads. High lateral STD was associated with inferior ST elevation in 16 patients (80%), whereas only eight patients (19.5%) with lateral STD and nine patients (31%) with anterior STD were associated with inferior ST elevation. Ischemia was detected in 63 of 90 patients (70%) with and in 10 of 70 patients (14.3%) without STD (p < 0.0001). Patients with high lateral STD had a higher prevalence of fixed perfusion defects in the inferior wall (95 vs. 27.8%) and in posterolateral wall (75 vs. 18.9%) compared with other patients (p = 0.003 and 0.002, respectively). Ischemia was more prevalent in patients with lateral STD than without (87.8 vs. 14.3%, p < 0.0001).

CONCLUSION

In patients with inferior Q wave, the presence of exercise-induced STD in lateral and anterior leads appears to be a sign of myocardial ischemia, and may require invasive evaluation; on the other hand, the presence of STD in high lateral leads should be recognized as a reciprocal change for ST elevation in the inferior leads, and may not be an indication for invasive evaluation.

Better decisions through science: exercise testing scores

Statistical tools can be used to create scores for assisting in the diagnosis of coronary artery disease and assessing prognosis. General practitioners and internists frequently function as gatekeepers, deciding which patients must be referred to the cardiologist. Therefore, they need to use the basic tools they have available (ie, history, physical examination and the exercise test) in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with diagnosis only using the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a more practical management strategy than a response of normal or abnormal. Although computers, as part of information management systems, can calculate complicated equations and derive these scores, physicians are reluctant to trust them. However, when represented as nomograms or simple additive discrete pieces of information, scores are more readily accepted. The scores have been compared with physician judgment and have been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated METs? Should ST/heart rate index be used instead of putting ST depression and heart rate separately into the models? Should right-sided chest leads and heart rate in recovery be considered? There is a need for further evaluation of these easily obtained variables to improve the accuracy of prediction algorithms, especially in women. The portability and reliability of scores must be ensured because access to specialized care must be safeguarded. Assessment of the clinical and exercise test data and application of the newer scores can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiologic care.

Assessing patients with possible heart disease using scores

Multivariable analysis of clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners are functioning as gatekeepers and decide which patients must be referred to the cardiologist, they need to use the basic tools they have available (i.e. history, physical examination and the exercise test), in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with simple classification of the ST response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers, as part of information management systems, can run complicated equations and derive these scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Their results have also been compared with physician judgment and found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated metabolic equivalents (METs)? Should ST/heart rate (HR) index be used instead of putting these measurements separately into the models? Should right-sided chest leads and HR in recovery be considered? There is a need for further evaluation of these routinely obtained variables to improve the accuracy of prediction algorithms especially in women. The portability and reliability of these equations must be demonstrated since access to specialised care must be safe-guarded. Hopefully, sequential assessment of the clinical and exercise test data and application of the newer generation of multivariable equations can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiological care.

Sensitivity and specificity of the RAND/UCLA Appropriateness Method to identify the overuse and underuse of coronary revascularization and hysterectomy

There is no empirical evidence on the sensitivity and specificity of methods to identify the possible overuse and underuse of medical procedures. To estimate the sensitivity and specificity of the RAND/UCLA Appropriateness Method. Parallel three-way replication of the RAND/UCLA Appropriateness Method for each of two procedures, coronary revascularization and hysterectomy. Maximum likelihood estimates of the sensitivity and specificity of the method for each procedure. These values were then used to re-calculate past estimates of overuse and underuse, correcting for the error rate in the appropriateness method. The sensitivity of detecting overuse of coronary revascularization was 68% (95% confidence interval 60-76%) and the specificity was 99% (98-100%). The corresponding values for hysterectomy were 89% (85-94%) and 86% (83-89%). The sensitivity and specificity of detecting the underuse of coronary revascularization were 94% (92-95%) and 97% (96-98%), respectively. Past applications of the appropriateness method have overestimated the prevalence of the overuse of hysterectomy, underestimated the prevalence of the overuse of the coronary revascularization, and provided true estimates of the underuse of revascularization. The sensitivity and specificity of the RAND/UCLA Appropriateness Method vary according to the procedure assessed and appear to estimate the underuse of procedures more accurately than their overuse.

Exercise echocardiography for the prognostic stratification of patients with low pretest probability of coronary artery disease

PURPOSE

The aim of this study was to determine whether exercise echocardiography provides incremental data for risk stratification of patients with a low pretest probability of coronary artery disease.

PATIENTS AND METHODS

The study included patients referred for exercise echocardiography whose probability of coronary artery disease was 25% or less. We calculated an exercise wall motion score index (on a 1-5 scale), an indicator of the extent and severity of exercise-induced abnormalities. The primary outcomes of the study were subsequent cardiac events (cardiac death and nonfatal myocardial infarction).

RESULTS

We studied 571 men and 1047 women; their mean (+/- SD) age was 55 +/- 13 years. During a median follow-up of 3 years, there were 19 cardiac events (6 cardiac deaths and 13 nonfatal myocardial infarctions); an additional 37 patients underwent coronary revascularization. In a multivariate analysis of clinical, exercise electrocardiographic, and echocardiographic parameters, exercise wall motion score index (hazard ratio [HR] = 2.1 per 0.5 units; 95% confidence interval [CI]: 1.3 to 3.4), and age (HR = 2.0 per decade; 95% CI: 1.2-2.8) were independently associated with the risk of cardiac events. Although exercise echocardiographic variables contributed significantly (P = 0.01) to a model of the risk of adverse events, only 9 (47%) of the 19 patients with cardiac events were identified by an abnormal exercise echocardiogram.

CONCLUSION

Among patients with low pretest probability of coronary artery disease by clinical criteria, exercise echocardiography identifies some, but not all, patients at risk of future events. Because of the low event rate, routine application of exercise echocardiography in a patient with a low pretest probability does not appear to be cost-effective and therefore cannot be recommended.

Simple treadmill score to diagnose coronary disease

OBJECTIVE

Our aim was to derive and validate a simplified treadmill score for predicting the probability of angiographically confirmed coronary artery disease (CAD).

BACKGROUND

The American College of Cardiology/American Heart Association guidelines for exercise testing recommend the use of multivariable equations to enhance the diagnostic characteristics of the standard treadmill test. Most of these equations use complicated statistical techniques to provide diagnostic estimates of CAD. Simplified scores derived from such equations that require physicians only to add points have been developed for pretest estimates of disease and for prognosis. However, no simplified score has been developed specifically for the diagnosis of CAD using exercise test results.

METHODS

Consecutive patients referred for evaluation of chest pain who underwent standard treadmill testing followed by coronary angiography were studied. A logistic regression model was used to predict clinically significant (> or = 50% stenosis) CAD and then the variables and coefficients were used to derive a simplified score. The simplified score was calculated as follows: (6 x maximal heart rate code) + (5 x ST-segment depression code) + (4 x age code) + angina pectoris code + hypercholesterolemia code + diabetes code + treadmill angina index code. The simplified score had a range from 6 to 95, with < 40 designated as low probability, between 40 and 60 was intermediate probability, and > 60 was high probability for CAD.

RESULTS

A total of 1,282 male patients without a prior myocardial infarction underwent exercise treadmill testing and coronary angiography in the derivation group, and there were 476 male patients in the validation group from another institution. The area under the receiver operating characteristic curve (+/- SE) for the ST-segment response alone was 0.67 as compared to 0.79 +/- 0.01 for the diagnostic score (p > 0.001). The prevalence of significant disease for the men was 27% in the low-probability group, 62% in the intermediate-probability group, and 92% in the high-probability group, which was similar to the prevalence in the validation group, with 22%, 58%, and 92% in low-, intermediate-, and high-probability groups, respectively. The low-probability group had < 4% prevalence of severe disease. In both populations, 7 more patients out of 100 were correctly classified than with the use of ST-segment criteria. When used as a clinical management strategy, the score has a sensitivity of 88% and a specificity of 96%.

CONCLUSION

This simplified exercise score that estimates the probability of CAD can be easily applied without a calculator and is a useful and valid tool that can help physicians manage patients presenting with chest pain.

The clinical use of imaging techniques with exercise testing

The addition of nuclear imaging techniques to basic exercise electrocardiography (ECG) has provided significant diagnostic and prognostic information in the evaluation of patients with suspected coronary artery disease. During the last decade, new classes of isotopes (technetium-and rubidium-based perfusion agents) and refinements in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have become better accepted. These new studies have added to the diagnostic armamentarium available to physicians, but at considerable costs with an estimated 4.8 million procedures performed this year. Nuclear imaging techniques can assess myocardial blood flow (perfusion imaging) or function (ventriculography). Another imaging modality, stress echocardiography, has also achieved widespread acceptance with clinical guidelines for its use published in 1997. This review addresses these imaging techniques in diagnostic evaluation of the patient with suspected coronary artery disease.

Comparison of myocardial blood flow during dobutamine-atropine infusion with that after dipyridamole administration in normal men

OBJECTIVES

The present study was designed to compare the absolute myocardial blood flow (MBF) after intravenous dipyridamole infusion with that during dobutamine-atropine administration in normal healthy male volunteers.

BACKGROUND

Both safety and usefulness of dobutamine-atropine stress in myocardial perfusion imaging have been reported. However, no information exists on whether the magnitude ofhyperemia achieved with dipyridamole and dobutamine-atropine is comparable.

METHODS

Myocardial blood flow was measured with positron emission tomography and 15O-labeled water in 20 healthy young men (23 +/- 3 years) 1) at baseline, 2) after dipyridamole infusion (0.56 mg/kg over 4 min), and 3) during dobutamine (40 microg/kg/min) and atropine (0.25 to 1.0 mg) infusion.

RESULTS

The MBF was significantly increased during dipyridamole infusion and during dobutamine-atropine stress compared with at rest (4.33 +/- 1.23 and 5.89 +/- 1.58 vs. 0.67 +/- 0.16 ml/min/g, respectively, p < 0.0001). Moreover, dobutamine-atropine infusion produced greater MBF compared with dipyridamole (p = 0.0011), while coronary vascular resistance did not differ significantly after dipyridamole administration and during dobutamine-atropine infusion (17.6 +/- 7.9 vs. 18.6 +/- 5.6 mm Hg/[ml/min/g], respectively).

CONCLUSIONS

Near maximal coronary vasodilatation caused by dipyridamole is attainable using dobutamine and atropine in young healthy volunteers. Dobutamine in conjunction with atropine is no less effective than dipyridamole in producing myocardial hyperemia.

Preparing the azotemic diabetic patient for surgery

Azotemic diabetic patients have more risk of complications during or after surgery than those without diabetes and azotemia. These complications include infection, excessive bleeding, cardiovascular events, and electrolyte imbalance. The appropriate preoperative evaluation, measures to be taken to avoid the complications, and how to adequately manage blood sugar during surgery is discussed.

Diarrhea and abnormalities of gastrointestinal function in a cohort of men and women with HIV infection

OBJECTIVE

The aim of this study was to determine the prevalence of gastrointestinal dysfunction in the era of improved treatment of HIV infection.

METHODS

Gastrointestinal function was studied cross-sectionally in 671 persons with HIV. Absorptive function was measured by a 25-g D-xylose test, a Sudan-III stain for fecal fat on a 100-g fat diet, and serum levels of micronutrients.

RESULTS

Eighty-eight percent had at least one abnormality of gastrointestinal function: 47.7% had low D-xylose absorption; 40.3% had a history of liver disease; 38.9% had diarrhea; 28.3% had chronic diarrhea; 22.5% had borderline or low serum vitamin B12 levels; 12.2% had stool pathogens; and 7.2% were hypoalbuminemic. Men were more likely to have low D-xylose absorption, diarrhea, and stool pathogens than women. Intravenous drug users (IVDUs) were more likely to have a history of liver disease and hypoalbuminemia. However, borderline or low vitamin B12 levels were less frequent in IVDUs; they tended to have less diarrhea and a lower prevalence of stool pathogens. Despite less history of liver disease, 14.1% of women were hypoalbuminemic. Differences in patterns of gastrointestinal dysfunction are unlikely to be due to severity of immunosuppression as abnormalities were seen in all risk groups with CD4 >200 cells/mm3. D-xylose absorption below 30 mg/dl, current diarrhea, and borderline levels of vitamin B12 were associated with advanced immunosuppression.

CONCLUSIONS

Abnormalities of gastrointestinal function are common in the current era of HIV treatment, appear early in the course of HIV infection, and in the absence of diarrhea. Gender and IVDU are important determinants of the type and frequency of gastrointestinal abnormalities.

Fat malabsorption assessed by 14C-triolein breath test in HIV-positive patients in different stages of infection: is it an early event?

The aim of this study was to evaluate fat absorption in HIV-positive (HIV+) patients in different phases of HIV infection using a 14C-triolein breath test. We distributed 47 HIV+ patients according to the 1993 Centers for Disease Control Revised Classification: 20 in Group 2 (A1 or A2) and 27 in Group 3 (B1, B2, A3, B3, or C). Ten HIV-negative healthy subjects comprised the control group (Group 1). All individuals underwent a 14C-triolein breath test. Parasitic infection was evaluated through three stool exams, including Cryptosporidium and Isospora investigation. The median value of cumulative 6 hours' 14C excretion expressed as percentage of the 14C given as triolein was significantly higher in Group 1 (8.4%) than Group 2 (5.5%) or Group 3 (3.4%), p = 0.04 and p << 0.01, respectively. Fat malabsorption was found in 25% of Group 2 individuals, 52.6% of those without diarrhea in Group 3, and was correlated with CD4+ lymphocyte counts (p << 0.01). Fat malabsorption is a common feature in advanced stages of HIV infection, even in the absence of diarrhea and is also present in asymptomatic HIV+ patients. These findings suggest that malabsorption is an early event in HIV-infected individuals and is correlated with the degree of immunosuppression.

The grade of worsening of regional function during dobutamine stress echocardiography predicts the extent of myocardial perfusion abnormalities

AIM

To evaluate the angiographic, myocardial perfusion, and wall motion abnormalities in patients with severe compared with mild worsening of regional function during dobutamine stress echocardiography (DSE) for evaluation of myocardial ischaemia.

METHODS

147 patients with significant coronary artery disease and new or worsening wall motion abnormalities during DSE were enrolled. Left ventricular function was evaluated using a 16 segment/4 grade score model where 1 = normal and 4 = dyskinesis. Simultaneous sestamibi SPECT myocardial perfusion imaging was performed in all patients.

RESULTS

Severe worsening of regional function (an increase in wall motion score of two grades or more in >/= 1 segment) was detected in 37 patients, while 110 patients had mild worsening (an increase in wall motion score of no more than one grade in >/= 1 segment). Patients with severe worsening of regional function had more stenotic coronary arteries (2.31 (0.8) v 1.97 (0. 8) (mean (SD)) (p <0.05), a higher prevalence of left anterior descending coronary artery disease (95% v 73%) (p < 0.05), a higher resting wall motion score index (1.71 (0.42) v 1.51 (0.40) (p = 0. 01), and more stress perfusion defects (3.8 (1.5) v 2.8 (1.5) (p < 0.001) compared with patients with mild worsening. Multivariate analysis identified the number of stress perfusion defects (p < 0. 005, chi(2) = 8.8) and the number of ischaemic segments on echocardiography (p < 0.05, chi(2) = 4.3) as independent variables associated with severe worsening of regional function.

CONCLUSIONS

The grade of worsening of regional function during DSE predicts the underlying extent of myocardial perfusion abnormalities. The occurrence of severe worsening of regional function is associated with variables known to predict worse prognosis in patients with coronary artery disease.

Significance of resting wall motion abnormalities in 2-dimensional echocardiography in patients without previous myocardial infarction referred for pharmacologic stress testing

BACKGROUND

Resting wall motion abnormalities (WMA) in 2-dimensional echocardiography may be encountered in patients without previous myocardial infarction or known coronary artery disease (CAD) who are referred for stress testing. However, the functional significance of these abnormalities has not been evaluated by an independent technique. The goals of this study were to assess the value of resting WMA in the prediction of an ischemic response during dobutamine stress testing independent of other clinical characteristics in patients without known CAD, and to evaluate whether the presence of resting WMA is related to the presence or extent of myocardial perfusion abnormalities during dobutamine stress testing.

METHODS

We studied 116 patients (mean age 57 +/- 13 years, 50 men) without known CAD or a history of myocardial infarction by dobutamine-atropine (dobutamine: </=40 microg/kg/min; atropine: </=1 mg) stress echocardiography and simultaneous stress and rest technetium sestamibi single-photon emission computed tomography imaging. Ischemia was defined as new or worsening wall motion abnormalities and reversible perfusion defects, respectively.

RESULTS

Resting WMA were detected in 24 patients (21%). Patients with resting WMA had a higher prevalence of abnormal perfusion (75% vs 25%, P <.001) and a higher prevalence of ischemia by single-photon emission computed tomography (50% vs 24%, P <.05) and by echocardiography (42% vs 9%, P <.001) compared with patients without resting WMA, respectively. Stress and rest perfusion defect scores were significantly higher in patients with than in those without rest WMA (3.25 +/- 2.67 vs 0.88 +/- 1.77, P <.0001; and 1.46 +/- 1.69 vs 0.21 +/- 0.70, P <.0001; respectively). Independent predictors of the occurrence of ischemia by echocardiography were the presence of resting WMA (P <.01, chi(2) = 6.7), ST-segment depression (P <.005, chi(2) = 11.3), and angina during the test (P <. 05, chi(2) = 5.3) by using multivariate analysis of clinical and stress test variables. The presence of resting WMA was the only independent predictor of an abnormal perfusion (P <.0001, chi(2) = 20).

CONCLUSION

The presence of resting WMA in patients without known CAD or a previous myocardial infarction who were referred for pharmacologic stress testing is highly predictive of abnormal myocardial perfusion. Resting WMA are powerful independent predictors of an ischemic response during dobutamine stress testing and identify a population with a higher prevalence and extent of myocardial perfusion abnormalities.

Is rest or exercise hypertension a cause of a false-positive exercise test?

STUDY OBJECTIVES

To determine if a history of hypertension or an exaggerated rise in exercise systolic BP is associated with a false-positive exercise ECG.

DESIGN, SETTING, AND PATIENTS

Retrospective analysis of the associations between exercise-induced ST-segment depression and a history of hypertension, exercise systolic BP, and several other clinical and exercise test variables. Among 20,097 patients referred for exercise tomographic thallium imaging in a nuclear cardiology laboratory at a tertiary care center, 1,873 patients met inclusion criteria for this study, which included no history of myocardial infarction or coronary artery revascularization, a normal resting ECG, and normal exercise thallium images.

RESULTS

False-positive ST-segment depression occurred in 20% of the population. A history of hypertension was actually associated with a lower likelihood of ST-segment depression (odds ratio, 0.70; 95% confidence interval [CI], 0.55 to 0.89; p = 0. 004). A higher peak exercise systolic BP was associated with a higher likelihood of ST-segment depression (odds ratio, 1.08 for each 10-mm Hg increase in systolic BP; 95% CI, 1.03 to 1.14; p < 0. 001). However, the association between peak exercise systolic BP and ST-segment depression was so weak that this measurement could not be predictive in the individual patient (R(2) = 0.2%). For every 20-mm Hg increase in peak exercise systolic BP, the percentage of patients with ST-segment depression increased by only 3%.

CONCLUSIONS

In patients with normal resting ECGs, we conclude the following: (1) a history of hypertension is not a cause of a false-positive exercise test, and (2) higher exercise systolic BP is a significant but weak predictor of ST-segment depression.

Screening for coronary artery disease

Unidentified coronary artery disease remains a significant cause of premature death and morbidity during the prime of life. The availability of effective interventions for the management of ischemia has provoked new interest in screening for this condition in asymptomatic patients, in the hope of reducing the burden of this condition. Although widespread use of stress testing is ineffective, the use of imaging techniques may offer better accuracy for detection of ischemia. Other tests that identify evidence of atheroma in the peripheral or coronary circulation may be useful to identify patients at risk.

Myocardial perfusion abnormalities in treated hypertensive patients without known coronary artery disease

OBJECTIVE

Myocardial perfusion abnormalities may occur in hypertensive patients in absence of significant coronary artery disease. However, it is not well established whether hypertensive patients without known coronary artery disease have a higher prevalence or extent of myocardial perfusion abnormalities compared with normotensive patients with similar clinical features.

DESIGN

This study compares the prevalence and extent of rest and stress-induced myocardial perfusion abnormalities in patients with and without hypertension.

METHODS

Dobutamine (up to 40 microg/kg per min) stress technetium-99m myocardial perfusion SPECT imaging was performed for evaluation of myocardial ischaemia in 350 patients (mean age = 60+/-13 years, 146 men) without known coronary artery disease. One hundred and forty-eight patients were hypertensive. Rest SPECT images were acquired 24 h after the test Abnormal perfusion was defined as the presence of reversible or fixed perfusion defects.

RESULTS

No significant difference was detected between patients with and without hypertension regarding gender, prevalence of symptoms, risk factors, pretest probability of coronary artery disease (52+/-28 versus 53+/-29%), peak rate pressure product (21040+/-4755 versus 20774+/-4865) or number of patients achieving the target heart rate during stress (85 versus 86%). Hypertensive patients were significantly older (62+/-11 versus 58+/-13 years, P = 0.005) and were receiving beta-blockers more frequently (34 versus 18%, P = 0.0001). The prevalence of myocardial perfusion abnormalities was similar in patients with and without hypertension (28 versus 31% in patients with low, 38 versus 33% in patients with intermediate and 60 versus 58% in patients with high pretest probability of coronary artery disease, respectively). No significant difference was detected between the two groups regarding stress perfusion defect score (1.45+/-2.5 versus 1.50+/-2.6) or rest score (0.72+/-1.8 versus 0.68+/-1.6).

CONCLUSION

Treated hypertensive patients without known coronary artery disease have a similar prevalence and severity of myocardial perfusion abnormalities at rest and at dobutamine stress compared with normotensive patients with similar clinical characteristics.

Gender differences in the relation between ST-T-wave abnormalities at baseline electrocardiogram and stress myocardial perfusion abnormalities in patients with suspected coronary artery disease

The presence of ST-T-wave abnormalities in the resting electrocardiogram was reported as a predictor of coronary artery disease (CAD) and increased morbidity and mortality. However, the independent value of ST-T abnormalities for predicting the presence and severity of perfusion abnormalities during stress testing has not been studied in a homogenous patient group without known CAD. We evaluated the relation between resting ST-T abnormalities and myocardial perfusion abnormalities in 246 patients (age 59 +/- 13 years, 114 men and 132 women) without known CAD or previous myocardial infarction referred for evaluation of possible myocardial ischemia by dobutamine (up to 40 microg/kg/min) stress sestamibi or tetrofosmin single-photon emission computed tomographic imaging. Resting ST-T abnormalities were present in 123 patients, whereas 123 patients with normal resting electrocardiograms served as a matched control group. Abnormal myocardial perfusion (fixed or reversible perfusion defects) was detected in 72% of men with and in 35% of men without resting ST-T abnormalities (p <0.0001), whereas the prevalence of myocardial perfusion abnormalities was not different in women with and without resting ST-T abnormalities (27% vs 23%, p = NS). In the entire population, independent predictors of an abnormal perfusion by multivariate analysis of clinical characteristics and risk factors were male gender (p <0.001, chi-square 10.5) and resting ST-T abnormalities (p <0.05, chi-square 3). Separate analysis of patients based on gender revealed resting ST-T abnormalities as independent predictors of abnormal perfusion in men (p <0.05, chi-square 4) but not in women. Stress perfusion defect score was higher in men with than without ST-T abnormalities (887 +/- 545 vs 207 +/- 180, p <0.001). It is concluded that resting ST-T wave abnormalities are associated with a higher prevalence and severity of resting and dobutamine-induced myocardial perfusion abnormalities in men but not in women. Resting ST-T wave abnormalities are powerful predictors of compromised myocardial perfusion independent of other clinical risk factors of CAD in men.

Pharmacological stress testing

Pharmacological stress in conjunction with radionuclide myocardial perfusion imaging has become a widely used noninvasive method of assessing patients with known or suspected coronary artery disease. In the United States, over one third of perfusion imaging studies are performed with pharmacological stress. Pharmacological stress agents fall into two categories: coronary vasodilating agents such as dipyridamole and adenosine, and cardiac positive inotropic agents such as dobutamine and arbutamine. For both, in the presence of coronary artery disease (CAD), perfusion image abnormalities result from heterogeneity of coronary blood flow reserve. Vasodilating agents work directly on the coronary vessels to increase blood flow, whereas inotropic agents work indirectly by increasing myocardial work load, which then leads to an increase in coronary blood flow. Both classes of agents have high accuracies for diagnosing coronary artery disease, and they have excellent safety records with acceptably low occurrences of side effects. For dipyridamole planar thallium imaging, pooled analysis yields a sensitivity of 85% and a specificity of 87% for diagnosis of coronary disease, but there is a large variation in reported values depending on various factors, such as the extent of postcatheterization referral bias, the type of imaging (planar versus single photon emission computed tomography [SPECT]), the types of patients being studied (single versus multivessel disease, men versus women), and the imaging agent used (thallium versus one of the technetium-based agents). Diagnostic accuracies for adenosine are similar to those of dipyridamole, with reported overall sensitivities ranging from 83% to 97%, and specificities ranging from 38% to 94%. For dobutamine, pooled analyses yield a sensitivity of 82% and a specificity of 75%. There is some concern that dobutamine may interfere with uptake of technetium-99m sestamibi, lowering the sensitivity for detection of disease, and thus the vasdodilating agents are generally preferred. Pharmacological stress testing has high clinical use for risk stratifying patients with known or suspected CAD, in patients after myocardial infarction, and in patients needing noncardiac surgery. Vasodilating agents are particularly advantageous in assessing post-myocardial infarction patients, allowing testing as soon as 2 days after the event. Like patients undergoing exercise stress testing, patients with normal perfusion images by pharmacological stress have a <1% annual incidence of cardiac events. The likelihood of an event increases with the extent and severity of perfusion abnormalities. However, it is important to consider clinical variables when using perfusion imaging for risk stratification, particularly in the presurgery patients. As with exercise testing, adjunct markers such as ST segment depression during testing, lung uptake of radiotracer (if thallium is used), and ventricular cavity dilatation add additional prognostic information to that available from the perfusion images alone. The aim of current research is to find better agents that are easier to use and that have fewer side effects. MRE-0470 is an experimental vasodilating agent that is more receptor selective than adenosine and promises a lower incidence of hypotension. Arbutamine more closely simulates exercise than dobutamine, and it can be administered by a closed-loop computerized delivery device. Work is also underway to look at novel uses of pharmacological stress agents, such as acquiring gated SPECT images during dobutamine infusion to enhance detection of myocardial viability. With increasing use of noninvasive testing in elderly patients and in patients with comorbidities that preclude adequate exercise, pharmacological stress testing has become an indispensable tool for radionuclide myocardial perfusion imaging studies. A good understanding of pharmacological stress testing is essential for performing high-quality nuclear cardiology

Exercise stress testing. An overview of current guidelines

Exercise stress testing (ET) is an inexpensive noninvasive tool that provides valuable cardiopulmonary information in healthy and diseased populations. It is most commonly used for diagnosing coronary artery disease (CAD) and developing appropriate exercise prescriptions (EP). With its widespread use and application, it is imperative that safe and appropriate guidelines and procedures are used, as there are a number of risks associated with testing in a population with or suspected of having CAD. The focus should be on the patient's safety: personnel must be properly trained and aware of all emergency procedures, contra-indications for ET and indications for test termination must be strictly adhered to. Three main types of testing are prevalent: submaximal, maximal and maximal utilising gas exchange. The maximal test is most commonly used, and the submaximal is appropriate for hospitalised patients. Gas exchange data is essential when assessing congestive heart failure and timing for heart transplantation. ET is commonly performed using a treadmill or a bicycle ergometer. The treadmill provides a more familiar exercise modality and has been shown to have greater diagnostic sensitivity than the bicycle ergometer; it is, however, more expensive and requires more space in the testing room. The bicycle ergometer is more appropriate for those individuals who are severely obese or have problems with extended periods of walking. Regardless of the modality used, an appropriate exercise protocol should be used. In North America, the Bruce protocol is the most common. However, the Bruce protocol, and others that estimate exercise capacity based on equations, tend to overestimate exercise capacity. They may be too demanding for those with limited exercise capacity, and too long for those with high exercise capacity. For these people, an exercise protocol that reaches maximal capacity in 8 to 12 minutes using smaller increments in workload should be considered. Once completed, the results of ET needs to be correctly interpreted. This includes reviewing the test results while considering the patient's history, medications and indication for the test. ET can also be used to develop an EP for the participant. An EP should take into account the intensity, modality of exercise, frequency and duration, as well as being realistic for the individual and the goals to be achieved. All the information from the test results and the pre-test examination should be presented in a report that also includes the advised EP.

The significance of stress-induced ST segment depression in patients with inferior Q wave myocardial infarction

OBJECTIVES

This study was conducted to evaluate the relationship between ST segment depression (STD) during dobutamine stress tests in different electrocardiogram (ECG) leads and myocardial ischemia assessed by simultaneous single photon emission computed tomography (SPECT) imaging in patients with inferior Q wave myocardial infarction.

BACKGROUND

STD is a standard electrocardiographic sign of myocardial ischemia. Although STD may represent reciprocal changes in patients with previous myocardial infarction, studies of reciprocal changes during stress tests are scarce.

METHODS

Dobutamine (up to 40 microg/kg/min) stress and rest myocardial perfusion scintigraphy using technetium SPECT imaging was performed in 125 patients >3 months after Q wave inferior myocardial infarction. The location of STD at the ECG was defined as anterior (V1-4), high lateral (I, aVL) and lateral (V5,6). Ischemia was defined as reversible perfusion abnormalities.

RESULTS

STD occurred in the high lateral leads in 20 patients, in the anterior leads in 12 patients and in the lateral leads in 2 patients. ST segment elevation occurred in 25 patients in the inferior leads. High lateral STD was associated with inferior ST elevation in 16 patients (80%). There was a significant inverse linear correlation between the magnitude of ST segment shift from rest to peak stress in the inferior and the high lateral leads (r = -0.8, p < 0.0005), whereas no significant correlation was found between ST segment shift in the inferior and the anterior leads (r = -0.1, p = NS) or between the inferior and the lateral leads (r = 0.15, p = NS). Ischemia was detected in 45% of patients with and in 42% of patients without high lateral STD (p = NS). Patients with high lateral STD had a higher prevalence of fixed perfusion defects in the inferior wall (100% vs. 70%) and in the posterolateral wall (55% vs. 29%) compared with other patients (both p < 0.05). Ischemia was more prevalent in patients with anterior STD than without (75% vs. 39%, p < 0.05).

CONCLUSIONS

In patients with inferior Q wave myocardial infarction, stress-induced STD in high lateral leads should be recognized as a reciprocal change for ST elevation in the inferior leads, and therefore, should be interpreted with the consideration of the significance of ST elevation if present, rather than being indicative of myocardial ischemia on its own. The STD found in the anterior leads appears to be a sign of myocardial ischemia. These findings should be considered in the definition of a positive ECG stress test and in establishing the criteria for the termination of stress test.

Declining CD4+ T-lymphocyte counts are associated with increased risk of enteric parasitosis and chronic diarrhea: results of a 3-year longitudinal study

From January 1991 through September 1994, we observed people who were infected with HIV to assess the impact of enteric parasite-associated diarrhea. Respondents answered comprehensive questionnaires covering clinical and epidemiologic information and provided stool specimens monthly, which were examined unstained as well as stained with trichrome, chromotrope 2R, and with Kinyoun carbol-fuchsin, and with indirect immunofluorescence for Cryptosporidium. In all, 602 participants, who were interviewed, provided stool specimens at 3254 monthly visits. Parasites were associated with 50 of 354 (14.1%) acute diarrheal episodes (lasting < or = 28 days) and with 97 of 279 (34.8%) chronic episodes (lasting > 28 days). A parasite was associated with 31 of 222 (14.0%) episodes that occurred when CD4+ counts were > or = 200 cells/microl and with 150 of 566 (26.5%) episodes that occurred when CD4+ counts were < 200 cells/microl. The most commonly identified parasite was C. parvum, which was associated with 18 of 354 (5.1%) acute episodes and 36 (12.9%) of the 279 chronic episodes of diarrhea. In this patient population, enteric protozoan parasites were commonly associated with illness, particularly as immunosuppression worsened, and were more likely to be associated with chronic rather than acute diarrhea.

Quantification of Viable Myocardium in Multivessel Coronary Disease: Effects of the Redistribution Time after Reinjection Of Thallium-201 and Comparison with Postrevascularization Defect Size

Reinjection of 201Tl is used for improved detection of viable myocardium. Prospectively the effect of the redistribution time after injection for the quantification of the definitive perfusion defect size in multivessel coronary heart disease and severely impaired left ventricular function was examined. Thirty patients were included preoperatively before CABG. The study was performed with 80-90 MBq 201Tl-Cl and reinjection (40-50 MBq). Imaging was performed after an exercise test and 3 hours afterwards. Thereafter, the reinjection dose was given and repeated studies were performed 10 minutes, 2 hours, and 20 hours later. Defect sizes were compared with the 3-hour rest-study without reinjection. Imaging studies were repeated postoperatively. The defect size was expressed as % of left ventricular total myocardium. Perfusion defect sizes were as follows: post-stress study (27%), 3 hour rest-study (17%), post-reinjection-10 min (12%), 2 hours (9%), and 20 hours (7%). Compared with the 3 hour rest-study, the perfusion defect was reduced only in 7/30 patients in the study immediately after reinjection. In the delayed studies, defect sizes were markedly smaller (p < 0.05) both in studies 2 hours and 20 hours after reinjection. In 15/30 patients there was a marked reduction of 50% of defect sizes in the study 2 hours post-reinjection vs the 3 hour rest-study. The residual defects at 2 hours after reinjection were identical to the postoperative defect sizes (10%). Further prolongation of the redistribution time to 20 horus caused an additional small reduction in defect size only in two patients compared with the 2-hour post-reinjection images (n.s.). Using a marker as 201Tl with redistribution characteristics, the redistribution time after reinjection is of utmost importance to correctly identify the definitive size of the perfusion defect vs viable myocardium in patients with multivessel disease. A delay of 2 hours for redistribution after the reinjection most correctly corresponds to the postop defect size; a longer redistribution time did not provide additional advantages.

HIV/SIV enteropathy

Evidence is increasing that HIV/SIV-induced changes in the highly differentiated gut-associated immune system play a central role in the pathogenesis of gastrointestinal manifestations in HIV/SIV infection. It has been shown in both humans infected with HIV and in nonhuman primates infected with SIV that a rapid, very early, and more pronounced loss of CD4+ T-cells occurs in the mucosa in comparison to the peripheral blood. The loss of this important regulatory T-cell subset might explain mucosal immunodeficiency with the consequence of opportunistic mucosal infections. In addition, there is evidence that small intestinal damage occurs independently of secondary infections (HIV/SIV enteropathy). In late-stage human disease, HIV enteropathy is characterized by villous atrophy with hyporegeneration and dysmaturation of intestinal epithelial cells. In SIV infection of macaques, villous atrophy is a very early event; however, it is accompanied by crypt cell hyperproliferation. Early- and late-stage enteropathy in immunodeficiency virus infection may represent two types of immunologically mediated mucosal transformation in which the number and state of activation of regulatory T cells determine whether hypo- or hyperproliferative villous atrophy occurs.

Scintigraphic diagnosis of coronary artery disease: myocardial bull's-eye images contain the important information

The bull's-eye image, also called polar map image, has been developed as an important display for the visual and quantitative analysis of myocardial perfusion scintigrams. Quantitative analysis can be performed for example by comparing areas in the bull's-eye image with normal limits or by processing it using artificial neural networks. The usefulness of such methods is highly dependent on the information content of the bull's-eye image. The purpose of this study was to investigate whether there is more diagnostically important information in a set consisting of the myocardial bull's-eye image plus tomographic slice image than in the bull's-eye image alone. A population of 135 patients who had undergone both myocardial scintigraphy and coronary angiography, with no more than 3 months elapsing between the two examinations, was studied retrospectively. Four experienced observers independently classified visually all scintigrams regarding the presence/absence of coronary artery disease in two vascular territories using a four-grade scale. The observers classified the scintigrams once viewing bull's-eye images only, and once viewing tomographic slices and bull's-eye images. Coronary angiography was used as gold standard. The classifications were evaluated using the areas under the receiver operating characteristics (ROC) curves. The classifications based on bull's-eye images only were slightly more accurate than those based on tomographic slices and bull's-eye images in one of the two vascular territories (ROC areas of 0.66 vs. 0.64). The opposite relationship was found in the other vascular territory (0.78 vs. 0.81). None of the differences was statistically significant. In conclusion, the diagnostically important information for the diagnosis of coronary artery disease by myocardial perfusion scintigraphy is present in the bull's-eye image.

Selection of the optimal stress test for the diagnosis of coronary artery disease

OBJECTIVE

To compare the value and limitations of exercise testing, dipyridamole echocardiography, dobutamine-atropine echocardiography, and MIBI-SPECT (technetium-99m methoxyisobutyl nitrile single photon emission computed tomography) during dobutamine infusion in the diagnosis of coronary artery disease.

DESIGN

The performance of these four tests was assessed in random order on a consecutive cohort of patients. The presence or absence of coronary artery disease was confirmed by coronary angiography.

SETTING

Two tertiary care and university centres.

PATIENTS

102 consecutive patients with chest pain and no previous history of coronary artery disease. Ten patients with left bundle branch block were excluded for further analysis of exercise testing and scintigraphy results.

RESULTS

MIBI-SPECT was the most sensitive (87%) but the least specific test (70%). Exercise stress testing had a sensitivity of 66%, which increased to 80% when patients with inconclusive results were excluded. Dipyridamole and dobutamine echocardiography had similar sensitivity (81%, 78%) and specificity (94%, 88%). All four tests had similar accuracy and positive and negative predictive values. Agreement between the echocardiographic techniques was excellent (detection of coronary artery disease 87%, kappa = 0.72; regional analysis 93%, kappa = 0.72; diagnosis of the "culprit" vessel 95%, kappa = 0.92), and it was good between echocardiographic techniques and MIBI-SPECT (diagnosis of the culprit vessel 90%, kappa = 0.84 with dobutamine and 92%, kappa = 0.85 with dipyridamole).

CONCLUSIONS

Exercise stress testing has a sensitivity comparable to other tests in patients capable of exercising and with no basal electrical abnormalities. The greatest sensitivity is offered by MIBI-SPECT and the greatest specificity is obtained with stress echocardiography. Redundant information is obtained with dipyridamole echocardiography, dobutamine echocardiography, and MIBI-SPECT.

Factors of weight loss in patients with HIV and chronic diarrhea

Weight loss is significant in patients with HIV and chronic diarrhea. The aim of our study was to test for the links between weight loss, the level of food intake, and the severity of diarrhea and nutrient malabsorption. One hundred and sixteen patients with HIV and chronic diarrhea underwent a standardized gastrointestinal and nutritional evaluation, which included a questionnaire on diarrhea, a prospective estimation of food intake, a measurement of blood parameters and fecal lipid and nitrogen outputs, a stool examination for bacteria and parasites, and upper and lower digestive tract endoscopy. Diarrhea resulted from an infection by Cryptosporidia, Microsporida, or other pathogens in 22%, 20%, and 13% of the patients, respectively. Diarrhea appeared idiopathic in 45% of the patients. A significant negative correlation existed between the severity of weight loss and the levels of nutrient intake (p < .005), and a significant positive correlation between the severity of weight loss and stool frequency (p < .01). Multiple linear regression identified low caloric intake and high stool frequency as predictive of weight loss. No significant correlation was found between weight loss and the parameters of malabsorption, either by bivariate study or multiple regression. These results suggest that, in patients with HIV and chronic diarrhea, the degree of wasting is significantly related to the levels of dietary intake and the clinical severity of diarrhea, but not to the extent of nutrient malabsorption.