Incidence of thrombosis in perioperative and non-operative myocardial infarction.

BACKGROUND: The contribution of thrombosis to the aetiology of perioperative myocardial infarction (MI) is uncertain. We used optical coherence tomography (OCT) to determine the presence of thrombus and plaque morphology in patients experiencing a perioperative MI and matched patients experiencing a non-operative MI using OCT. METHODS: We conducted a single-centre, prospective, cohort study. Thirty patients experiencing a perioperative MI and 30 matched patients experiencing a non-operative MI, without ST elevation, underwent OCT to determine the presence of thrombus and culprit lesion plaque morphology. Angiography and OCT were performed a mean of 1.93(1.09) days and 1.53(0.68) days after the onset of perioperative and non-operative MI, respectively. OCT images were evaluated by an independent core laboratory without knowledge of whether the patient had suffered a perioperative or non-operative MI. RESULTS: We identified thrombus at the culprit lesion in four of 30 patients (13.3%) who experienced a perioperative MI and in 20 of 30 patients (66.7%) who experienced a non-operative MI, P<0.01. The only non-culprit lesion with thrombus was in a perioperative MI patient who also had a culprit lesion thrombus. Perioperative and non-operative MI culprit lesions demonstrated fibroatheroma in 18 patients (60.0%) us 20 patients (66.7%), respectively (P=0.52) and thin cap fibroatheroma in one patient (3.3%) us five patients (16.7%), respectively (P=0.11). One perioperative MI patient (3.3%) suffered a cardiac death and no non-operative MI patient died during the 30-day follow-up. CONCLUSIONS: Thrombosis was less common in perioperative than non-operative MI, despite similar underlying plaque morphology.

What is the role of invasive versus non-invasive coronary angiography in the investigation of patients suspected to have coronary heart disease?

The improved technology of multi-slice cardiac CT angiography (CTA) has enabled production of high quality images of the coronary arteries. The sensitivity and specificity of the test in identifying patients with obstructive coronary lesions in 64-slice and later generations of scanners is high. To enable effective use of CTA in the clinical setting, a better understanding of this technology, particularly in comparison to invasive coronary angiography, is needed. In this article we discuss the characteristics of CTA in comparison to invasive coronary angiography and discuss the role of CTA in the diagnosis of coronary artery disease (CAD). Newer CTA scanners and individualized scanning protocols can minimize radiation exposure from CTA. CTA can provide more information than invasive coronary angiography on the type and burden of atherosclerotic plaque in the coronary tree. CTA is most useful in those at intermediate risk of CAD.

Incremental detection of coronary artery disease by assessment of non-calcified plaque on coronary CT angiography.

AIM: The purpose of this study was to evaluate the improved assessment of coronary atherosclerotic plaque burden by measurement of non-calcified plaque in addition to calcified plaque using CT coronary angiography (CTA). MATERIALS AND METHODS: Low to intermediate-risk outpatients with suspected coronary artery disease were prospectively recruited. Patients underwent CTA and calcium scoring in addition to invasive angiography. The presence of plaque (calcified, non-calcified, and mixed) was analysed on a per segment basis (percentage of segments with disease) with stratification by calcium score (CS). RESULTS: Seventy-six patients were enrolled of whom 30 had a CS of 0, 26 had a CS of 1-200, and 20 had a CS of >200. One thousand, one hundred and two segments were analysed using CTA and invasive angiography. The prevalence of segments with calcified or mixed plaque was 3.1% (n=13) for a CS of 0, 15.1% (n=57) for a CS of 1-200, and 50% (n=142) for a CS of >200 (all p<0.0001). The proportion of segments with non-calcified plaque alone was low and similar among the three groups: 5.4% (n=23; CS=0), 8.2% (n=32; CS=1-200), and 8.6% (n=25; CS= >200), (CS=0 versus CS= >200; p=0.04, others p=ns). The relative increase in diseased segments by additional assessment of non-calcified plaque was greatest for patients with a CS of 0 (173%) versus a CS of 1-200 (55%), and a CS of >200 (17%). CONCLUSION: CTA offers increased relative incremental detection of non-calcified plaque, particularly in those with negative CS; however, the absolute detection of non-calcified plaque in those with negative CS is low. The prognostic significance of non-calcified plaque for the prediction of cardiac events, particularly in patients with low CS, requires continued study.

Rotational changes in the morphology of the vertebral artery at a common site of artery dissection.

OBJECTIVE: Given that vertebral artery dissection and transient vertebrobasilar insufficiency occurs commonly at the C1-C2 junction, the objective was to study, in vivo, the normal rotational anatomy at C1-C2 using magnetic resonance angiography (MRA) with 3-dimensional (3D) reconstructions and to correlate these reconstructions with our experience of dissection location. METHODS: 3D phase-contrast MRAs were obtained from the foramen magnum to C3 in 4 normal volunteers in neutral and rotated (45 degrees) positions. The magnitude images were used as source images for 3D reconstruction. The images from only 1 of the volunteers were completely motion free, and these were subjected to arterial length calculations using image analysis wire frame outline of the vessel. All angiograms of vertebral artery dissection obtained at our institution from 1993 to 1997 were also reviewed. RESULTS: 3D reconstructions document elongation (approximately 7% in quantitatively analyzed case) and slight narrowing of the artery contralateral to the direction of head rotation from C2 to the dural entry point. The artery turns most sharply and is subject to the anterior force of the rotating C1 vertebra as it exits the C1 foramen. Of 14 cases of vertebral artery dissection, 50% occurred between the transverse foramen and the posterior lamina of C1. CONCLUSIONS: With head rotation, the contralateral vertebral artery undergoes the greatest anatomical distortion as it exits the C1 transverse foramen. This increased stress may account for the higher frequency of dissections at this location.

Relationship of current and past smoking to mortality and morbidity in patients with left ventricular dysfunction.

OBJECTIVES: The aim of this study was to evaluate the impact of smoking in patients with left ventricular dysfunction. BACKGROUND: The impact of smoking in patients with left ventricular dysfunction has not been well-studied. METHODS: We compared the incidence of death, hospitalization due to heart failure and myocardial infarction (MI) in current smokers to ex-smokers of < or =2 years and ex-smokers of >2 years duration to never-smokers among participants of the Study Of Left Ventricular Dysfunction (SOLVD) Prevention and Intervention trials. Participants all had left ventricular ejection fraction (LVEF) <35% and follow-up was over a mean of 41 months. RESULTS: Complete smoking status and outcome data were available in 6,704 subjects. There were 1,562 current smokers, 1,317 ex-smokers of < or =2 years, 2,354 ex-smokers of >2 years and 1,471 never-smokers. After adjusting for baseline differences of age, LVEF, race and etiology of heart failure, current smoking was associated with a significantly increased all-cause mortality (relative risk [RR]: 1.41, 95% confidence interval [CI]: 1.25 to 1.58, p < 0.001) compared with ex-smokers and never-smokers. The incidence of death or recurrent congestive heart failure requiring hospitalization or MI was significantly greater (RR: 1.39, 95% CI: 1.26 to 1.52, p < 0.001) in current smokers compared with ex-smokers and never-smokers. There were no significant differences in the number of deaths or hospitalizations due to heart failure between ex-smokers and never-smokers. This effect was consistent across both the SOLVD Prevention and Treatment trials. CONCLUSIONS: Current smoking is a powerful independent predictor of morbidity (recurrent heart failure and MI) and mortality in patients with left ventricular dysfunction. Quitting smoking appears to have a substantial and early effect (within two years) on decreasing morbidity and mortality in patients with left ventricular dysfunction, which is at least as large as proven drug treatments recommended in patients with left ventricular dysfunction.

Cardiovascular and cancer mortality among Canadians of European, south Asian and Chinese origin from 1979 to 1993: an analysis of 1.2 million deaths.

BACKGROUND: Cardiovascular disease and cancer are important health problems worldwide, yet our knowledge of these conditions is derived principally from populations of European descent. To investigate ethnic variations in major causes of death in Canada, the authors examined total and cause-specific mortality among European, south Asian, and Chinese Canadians. METHODS: Canadians of European, south Asian and Chinese origin were identified in the Canadian Mortality Database by last name and country of birth and in the population census by self-reported ethnicity. Age-standardized death rates by cause, per 100,000 population, were calculated for ages 35 to 74 years from 1979 to 1993 and in 5-year intervals grouped around census years (1979/83, 1984/88 and 1989/93). RESULTS: Rates of death from ischemic heart disease were highest among Canadians of south Asian origin (men 320.2, women 144.5) and European origin (men 319.6, women 109.9) and were markedly lower among Canadians of Chinese origin (men 107.0, women 40.0); the rates declined significantly in all 3 groups over the study period. Rates of death from cerebrovascular disease were relatively low and showed less ethnic variation (Canadian men of European, south Asian and Chinese origin 49.5, 47.0 and 45.8 respectively; Canadian women of European, south Asian and Chinese origin 34.8, 39.0 and 42.2 respectively) and declined similarly in all groups over time. Rates of death from cancer were highest among Canadians of European origin (men 343.6, women 236.2), intermediate among those of Chinese origin (men 258.1, women 161.6) and lowest among those of south Asian origin (men 122.3, women 131.3). Over time, cancer mortality increased in Canadians of European origin but remained constant or declined in those of south Asian and Chinese origin. INTERPRETATION: Substantial differences exist in rates of death from ischemic heart disease and cancer among European, south Asian and Chinese Canadians.

Brain perfusion imaging in asymptomatic patients receiving cyclosporin.

BACKGROUND AND PURPOSE: Cyclosporin has neurotoxic effects in a significant number of transplant patients that are associated with characteristic findings on MR images. Focal abnormalities in cerebral perfusion have been implicated in the pathophysiology of cyclosporin neurotoxicity. In the clinically asymptomatic patient, however, it is not known whether any imaging evidence of cyclosporin's effect on the brain is demonstrable. Our hypothesis was that conventional MR imaging, perfusion MR imaging, and single-photon emission CT (SPECT) could enable detection of subclinical lesions in asymptomatic patients. The ability to detect such lesions might aid in the identification of persons most at risk for clinical neurotoxicity. METHODS: Ten posttransplant patients being treated with cyclosporin were recruited prospectively. Imaging studies were performed within 3 weeks of transplantation. Patients were examined with MR imaging, using standard spin-echo and dynamic contrast-enhanced perfusion techniques, and SPECT scanning. Postprocessing of MR perfusion data was performed to obtain pixel-by-pixel maps of regional cerebral blood volume, peak height, and time-to-peak parameters. RESULTS: The mean age of the patients was 45 +/- 11 years. At the time of imaging, three patients had minor neurologic manifestations commonly associated with cyclosporin (ie, mild tremor, headache), but no patient had clinical neurotoxicity. Findings on conventional MR images, MR perfusion maps, and SPECT perfusion scans were normal in all patients. CONCLUSION: Conventional MR imaging, dynamic perfusion MR imaging, and SPECT do not depict any lesions in asymptomatic patients on cyclosporin. Therefore, it may not be possible for imaging methods to aid in the identification of patients at risk for neurotoxicity. Our findings support previously published conclusions that the lesions visible in patients with clinical neurotoxicity are due to cyclosporin effects and not to preexisting coincidental abnormalities.

Increased winter mortality from acute myocardial infarction and stroke: the effect of age.

OBJECTIVES: We examined seasonal variations in mortality from acute myocardial infarction (AMI) and stroke by age using 300,000 deaths in the Canadian Mortality Database for the years 1980 to 1982 and 1990 to 1992. BACKGROUND: The effect of age on environmental determinants of AMI and stroke is not well understood. METHODS: Seasonal variations were analyzed by month and for the four seasons (winter beginning in December). A chi-square test was used to test for homogeneity at p < 0.01, and relative risk ratios (RRs) for high and low periods were determined in relation to the overall mean. For each of four age subgroups, the magnitude of the seasonal variation was reported as the difference in mortality between the highest and lowest frequency seasons. RESULTS: By month, AMI deaths were highest in January (RR = 1.090) and lowest in September (RR = 0.904), a relative risk difference of 18.6%. The seasonal mortality variation in AMI deaths (winter vs. summer) increased with increasing age: 5.8% for <65, 8.3% for 65 to 74, 13.4% for 75 to 84 and 15.8% for >85 years (p < 0.005 for trend). Stroke mortality peaked in January (RR = 1.113) and had a trough in September (RR = 0.914), a relative risk difference of 19.9%. The seasonal variation in stroke mortality also increased with age. Seasonal variations were not seen in those aged <65 years, compared with 11.6% for 65 to 74, 15.2% for 75 to 84 and 19.3% for >85 years (p < 0.005 for trend). CONCLUSIONS: The elderly demonstrate a greater winter increase in AMI and stroke mortality than younger individuals. An understanding of these seasonal patterns may provide novel avenues for research in cardiovascular disease prevention.

Reactivation of neurocysticercosis: case report.

A 37-year-old woman with a known history of longstanding neurocysticercosis presented with a three-day history of new onset headache. Several years prior to her current presentation, she had undergone cysticidal treatment and was assumed to be cured of active disease. Computed tomography and magnetic resonance imaging studies done three months prior to presentation showed multiple intracerebral calcified lesions consistent with resolved neurocysticercosis. Physical and laboratory findings were noncontributory. Imaging studies showed the same previously calcified lesions, but they were now surrounded by large amounts of edema. This case represents a unique report of reactivation of neurocysticercosis and raises interesting questions about the natural history of this infection.

Persistent MR contrast enhancement of calcified neurocysticercosis lesions.

PURPOSE: We sought to determine whether cysticercosis lesions in the brain continue to enhance after nodular involution and complete calcification, and to investigate the clinical significance of this finding with respect to seizure recurrence after cysticidal treatment. METHODS: Serial contrast-enhanced MR images were obtained in all patients with neurocysticercosis seen at our hospital over a 6-year period (1991-1997). From this group, all patients with nodular calcified lesions were selected for study. RESULTS: Sixteen of 29 patients with neurocysticercosis had nodular calcified lesions. Six of these 16 had rim enhancement of nodular calcified lesions for at least 1 year after imaging evidence of complete calcification. Three of these six patients with enhancing, calcified lesions continued to experience seizures. Three of the 10 patients without enhancement also continued to have seizures. CONCLUSION: Contrary to the literature, which states that enhancement and disease activity cease with calcification, six (38%) of 16 patients had lesions that continued to enhance after complete calcification. This abnormality may be a risk factor for posttreatment seizures or may suggest eventual resorption of the calcified lesion.

The relation of conjunctival pallor to the presence of anemia.

OBJECTIVE: To determine the value of conjunctival pallor in ruling in or ruling out the presence of severe anemia (hemoglobin < or = 90 g/L) and to determine the interobserver agreement in assessing this sign. DESIGN: Patients were prospectively assessed for pallor by at least one of three observers. All observations were made without information of the patient's hemoglobin value or of another observer's assessment. SETTING: Tertiary-care, university-affiliated teaching hospital. PATIENTS: Three hundred and two medical and surgical inpatients. MEASUREMENTS AND MAIN RESULTS: Likelihood ratios (LRs) calculated for conjunctival pallor present, borderline, and absent were as follows: pallor present, LR 4.49 (95% confidence interval [CI] 1.80, 10.99); pallor borderline, LR 1.80 (95% CI 1.18, 2.62); pallor absent, LR 0.61 (95% CI 0.44, 0.80). Kappa scores of interobserver agreement between paired observers were 0.75 and 0.54. CONCLUSIONS: The presence of conjunctival pallor, without other information suggesting anemia, is reason enough to perform a hemoglobin determination. The absence of conjunctival pallor is not likely to be of use in ruling out severe anemia. With well-defined criteria, interobserver agreement is good to very good.

Classifying ethnicity utilizing the Canadian Mortality Data Base.

UNLABELLED: The study of ethnic differences in disease is a methodological challenge as ethnicity is often not identified in existing datasets and surrogate measures need to be used. We have developed a novel methodology combining last name and country of birth to study mortality patterns of Canadians of South Asian (SA) and Chinese (CH) ethnic origin and have compared death rates among SA, CH, and White (WH) Canadians. METHODS: SA and CH were identified in the Canadian Mortality Data Base (CMDB) using the last name and country of birth of the deceased. Records of people who had been born in countries with large South Asian and Chinese populations (e.g. India, Pakistan, China, Hong Kong) were selected and manually screened by last name. A name directory was then created of distinct South Asian and Chinese names and this directory was used to search all other records in the CMDB for SA and CH deaths. Where necessary, other identifying characteristics such as first name and parents' last name were also used. Population counts were obtained from the Census self-reported question on ethnicity for SA and CH. WH were identified as non-immigrant Canadians who were neither SA nor CH. The method of assigning ethnicity in the CMDB and Census were assessed for comparability and issues of validity and reliability were addressed. RESULTS: Using this method, 10,989 SA and 21,548 CH deaths were identified. There was marked heterogeneity in birthplace, with only 56% of SA born in South Asia and only 74% of CH born in Greater China. Last names had high validity for self-reported ethnicity in a population sample of SA and were highly reproducible. Mortality rates varied dramatically between groups studied. SA and WH had high rates of ischemic heart disease while stroke mortality was similar among all three groups. Cancer death rates were high in CH and WH and much lower in SA. CONCLUSION: Last names and country of birth can be used to determined ethnicity of SA and CH with validity and reliability, and leads to a more accurate classification than country of birth alone. The contrasting patterns observed in mortality from major causes of death suggest many interesting hypotheses for further study.

Ion channel formation by duramycin.

The formation of ion channels by the nonadecapeptide antibiotic duramycin was examined using black lipid membranes and using the patch-clamp technique. In black lipid membranes made from glyceryl monooleate or a phosphatidylcholine/phosphatidylethanolamine mixture, duramycin induced complex fluctuations in membrane conductance, some step-like and some which were incapable of being resolved into discrete conductance states. Both conductance and largest step size increased with time. A similar time-dependent increase in conductance was seen in patch-clamp experiments with HCA-7 Colony 29 human colonic epithelial cell. The channels displayed weak anion selectivity and the smaller channels formed in patches from epithelial cells showed weak inward-rectification. Channel formation by duramycin was achieved at lower concentrations when the black lipid membrane was made with phospholipid rather than with glyceryl monooleate. Lower concentrations were effective in generating conductances in epithelial cells than in bilayers. It is concluded that duramycin forms ion channels in both artificial and biological membranes. Accumulation of duramycin and coalescence of initially small channels into larger ones is considered to be responsible for the recorded behaviour and to final disruption of membranes.